Chamber of Understanding

RX8 Project – Part 13, Canbus #3, Labview!

If you just want the CANbus ID for the RX8 PS light and not all the background work just skip to the end!

So it’s been quite a long time since I had chance to have another go at getting the CANbus on the cluster working and while previously I manged to get everything apart from the power steering warning light working I decided I really should find out why not. This is a simple lesson in why getting sufficient sleep is really important!

I was contacted a while ago buy a guy doing a similar conversion to mine who happened to have a second complete RX8 and a variety of diagnostic equipment that can talk CANbus who had send me a block of CANbus log data that I’ve done nothing like enough work on since I’ve had it! Anyway the key here is I knew that the car some of the logs had come from had the factory PCM (ECU) working as intended and as such the power steering light doesn’t illuminate. This meant that somewhere in that log file was the data that turned off the light, I just had to work out where it was!

Now first off I took the approach of taking the two sets of data logs I had, one from a car with a functioning PCM and one from a car that doesn’t. Then list out all the ID’s that occurred in each set of data. I’m going to assume for my purposes that any that occur in both sets are not required. The logic being that the data that turns off the light must be present in one set and not the other. I admit that this might not be the case if there’s something more complex going on like if with the PCM removed the power steering computer doesn’t get the required data and sends a different value on the same ID. But for now it’s a starting point!

The ID’s that remain are as follows:

201, 203, 215, 231, 240, 250, 420, 620, 630, 650

A couple of these we’ve already seen elsewhere, specifically 201, which is the RPM and speed to the dash, and 420 which control the cluster warning lights. So after setting up the arduino and canbus data to strobe all these remaining address and nothing happening I gave up!

Many weeks went by and I it was nagging at me why I couldn’t find the right code. Eventually I decided to try a different tack so I ordered a USBtin which is a really neat little USB to CAN adapter which appears as a virtual COM device in windows and can be controlled using a series of commands known as the LAWCIEL protocol (details of which can be found here). The kit version is really quite cheap and would probably be a good option for the budget conscious but on this occasion I just decided to be lazy and buy the prebuilt one.

Clearly I’ve decided to PC control it at this point! Next up I needed a way to stop it when the warning light went off. I ordered a very cheap optical detector off ebay which can be wired into an Arduino or something similar. These are the ones that vary around £1-2 so difficult to argue with. They offer a potentiometer to adjust the switching brightness so I can tune it to what I need and a digital output so I don’t need to mess about doing analog reads or calibrating things on a microcontroller. Yes i know it’s not the neatest or most efficient way of doing it but for my purposes it’s so cheap and easy it really doesn’t matter! So I need to make that talk to a PC in a way I can use and that’s where this whole thing starts to get more interesting.

I’d pondered ways of interfacing a microcontroller to a PC easily and while it’s not terribly hard to make it shout over serial when an input goes high I came across something much more interesting. There’s a company called National Instruments who make lots of very expensive software and equipment for recording data from experiments but fairly recently they started supporting hobbyists by producing the Labview Makerhub, and more specifically a package called LINX. LINX includes a series of drivers and firmwares to allow things like Arduinos, Beaglebones and even Raspberry Pi’s to be used as IO devices (the Raspberry Pi can actually have programs loaded to them as a full remote node). This is quite a major step because it suddenly allows hobbyists to use really good professional software without having the problem of only being able to use NI’s extremely expensive hardware! This gave me and idea – use labview as the core software then I can use the supplied LINX firmware to set up an arduino as IO. To make this deal even sweeter you can also download Labview for free from NI for home use. Take a look here

So after a quick bit of following the instructions we have a basic labview program that will read the arduino IO via serial:

Basically what this does is it starts by opening a serial connection via the LINX toolkit, this returns a device name to an on screen string display and passes a reference which identifies the connection to the read stage. The next bit the larger grey rectangle is how Labview handles a while loop so it’ll keep performing the enclosed functions constantly from left to right until the conditional term in the bottom right goes high – in this case it’s a stop button. So basically the loop just calls a LINX channel read of channel 2 where I connected the light sensor to the Arduino. The inner rectangle only executes when the read value is false (i.e. when the light goes off) and while there’s a lot of information recorded here from elsewhere in the program basically if it sees the light go off it records the current ID being tested, the time that has elapsed since the test started. This means we know when it’s right!

Labview is designed to capture data from lab instruments and so there’s a really handy thing called the VISA toolkit that allows blocks of data read and write via the serial port and basically you can just open a port with specified settings then make read and write requests and do things like crop the incoming data at a predefined character. In this case that character needed to be CR (Carriage Return) this is ASCIIcharacter 13 because LAWCIEL terminates everything with one.

For the USBtin we open the correct COM port at 115200,8 Data bits, No parity, 1 stop bit and no flow control. The other thing to note is at the top right, this sets the termination character to the numeric value of CR, the benefit here is you can perform a read of any length and it will automatically break up the data in the buffer so a single read can vary in length but the start will always synchronise with the read call. Opening the connection in a terminal program for the first time and you’ll see nothing actually happens as such, an OK is signified by a CR so all you see is the cursor move. At this stage we are only connected to the USBtin, not the CANbus. So next, configure the CAN connection, send a value of “S6\r” . The code is S6, this will set the USBtin to 500kbit correct for the dash, the \r is how you indicate a CR in a Labview string. Next I chose to send “v\r” which requests the version from the USBtin, we don’t need this but it gives a solid confirmation it’s talking to us. Next up Z1\r tells the USBtin to timestamp the incoming data, I thought this might be useful but never actually implemented it.

With the setup complete we can start reading data by opening the CAN connection by sending O\r. On a terminal program (assuming you have the CANbus wired up) doing this would result in packets of can data from the cluster appearing. The initial read of length 1 byte reads just the confirmation from the USBtin that it has received the open request. Next is the main read, it’s worth noting the read length is set at 50 bytes but this will be cut short by the termination character set earlier so we can accept varying length CAN data. C\r closes the CAN connection and again another read 1 byte clears the acknowledge. Tacked on the end is a section to read the controller status looking for error states etc. The keen eyed amongst you will notice the majority of this code is conditional, this is because the code needs to insert send requests among the stream of reads. This is because if the data is not read from the USBtin constantly a buffer somewhere fills (I imagine on the USBtin itself but can’t confirm this) and the port crashes. I spent a lot of time finding this out the hard way!

This is the write data code, again very similar but it just opens the port, writes whatever string is in the buffer and closes the connection. Once the connection is confirmed closed it resets the Boolean that causes the ‘write’ condition so on the next loop it goes back to reading again to keep the buffer clear. The read loop runs at the maximum possible speed but it is slowed down because it waits for either a termination character or 50 characters to be received before it completes and loops again.

Beyond that the only other bits of code just generate the data for the write buffer using an increment counter for the ID field and toggling between either 8 bytes of FFFF or 0000 every 100ms for 20 cycles and setting the write flag high to send the data..

So after letting this run for a fair while it started spitting out values, specifically the ID 300 for the power steering light. Wait a minute that wasn’t in the list earlier. Yes I know that, that’s where getting enough sleep comes in. Originally I split the data based on whether or not the PCM was fitted and ignored the ones that occurred in both sets, the obvious mistake here is that of course the power steering light isn’t controlled by the PCM, quite logically it’s controlled by the power steering controller!

So there we go, ID 300, the first byte (leading) controls the light, values below 80 turn the light off. Unplugging the PCM causes the controller to send 80 on loop hence the the warning light.

Get data from ID: 4B1
0	0	0	0	0	0	0	0	
-----------------------------
Get data from ID: 81
43	6F	1	4B	
-----------------------------
Get data from ID: 300
80	
-----------------------------
Get data from ID: 231
F	0	FF	FF	0	
-----------------------------
Get data from ID: 430
95	5F	83	0	0	0	60	
-----------------------------
Get data from ID: 81
25	6F	1	4B	
-----------------------------
Get data from ID: 81
16	6F	1	4B	
-----------------------------
Get data from ID: 630
8	0	0	0	0	0	6A	6A

Looking at the log data again we see that ID 300 is getting a value of 80 – this is during the self test before the engine is started. I previously tried sending this data on the original Arduino CAN setup and go no result so what did I do wrong. Again this is based on another assumption, I though the logger was ignoring high order bytes with zero value (ie this value if could be 00-00-00-00-00-00-00-80) well it turns out that was totally wrong, it actually ignores trailing zeros, the value of the can data here should be 80-00-00-00-00-00-00-00.

So while all these hours of work told me one thing I should have already known it’s actually worked out Ok because it highlighted this other problem (read ‘incorrect assumption’ !). This means The odds of me working out all the other data from the logs (that I’d previously written off as not usable) is actually much higher!

RX8 Project – Part 12, Turbos #3 – Flanges

This is a step that most people won’t need to do. Or rather there are usually easier alternatives to! When most people build a turbo manifold they simply buy pre-cut flanges for both the inlet and outlet and weld them onto the ends of whatever intricate bit of welded pipework they have devised and all is well. This is fine for the vast majority of turbos currently available but what if we have one that’s a bit more unusual, say one that most people would never even dream of using for a custom setup. For example the custom housing GT15 turbo used on a diesel Rover from about 20 years ago. That would present more of a challenge! Why do I never make these things simple!

So what we need to do is make some flanges, this isn’t a technically complex task but does take a little thought.

The first step is to carefully measure the size of either the fixed studs (or bolt holes). These are commonly M8 and so the bolt OD will be just under 8mm and if the flange has the holes will be more than the bolt size as they tend to be quite generous to aid alignment. M8 clearance hole might well be as much as 9mm but note these all down.

Next measure the distance between each of the holes/studs, adding half of each hole/stud diameter on these numbers will give you the distance between the centre of each fixing position. This gives the fixing positions and would allow a template for these to be drawn. If doing the job this way you just need to measure the main port diameter and its distance from the centre of each hole/stud position to the centre of the port. In my case one port was handily central in a triangle so I could just measure half way between each pair of stud and draw a line to the third stud and where they cross the port centre goes.

I also tried another approach which involved taking a thing piece of aluminium and physically imprinting it with the studs using a mallet. This can be handy for really irregular patterns but does mean you don’t have a nice dimensioned drawing to keep, but you do get an aluminium template. Basically you take your aluminium, lay it over the studs and tap it with a mallet. This leaves an impression for all the fixing positions. What you’d normally do here is just drill a small pilot hole where the centre of each stud is to use to mark up your steel. in my case I didn’t want to have to remove the studs from the turbo so I drilled them out full size.

At this stage I used the same method to indent the sheet metal for the port which was then drilled with a 3mm hole for later transfer.

The port mark was critical because the port was the largest hole and most likely to go wrong! After marking it up on the 10mm thick steel plate I was going to use as the flange and looking at my pillar drill I decided I needed a substantial clamp for safety! While I could have bought a suitable clamp kit I decided that since I already owned suitable tee nuts for the bed I could make it safely.

So this was the final drilling arrangement – and yes that is a hole saw! I feel at this point I should point out that not all hole saws are created equal. Most commonly found at DIY shops are only suitable for wood/plastic/plasterboard and maybe aluminium sheet which not unreasonably are the sort of things used in DIY. Proper tool shops will supply hole saws rated for steel but they will cost a little more the set I used was this one. It’s certainly not the most expensive out there and probably won’t last terribly long with this level of use but it’s rare I use them for anything like this and I can replace the individual saws in the set fairly cheaply.

You need to centre punch where the port centre is to locate then mount the plate onto the drill. Put a smallish drill bit (don’t go really small as you risk breaking it, I started at 3mm but you could easily go a little larger as this isn’t really precise work) into the chuck and carefully align the punched mark on the plate with the tip. Once you are happy with the location tighten the clamps down. Tighten a little each side at a time if you have an arrangement like mine as otherwise the high pressure on one side will tend to make the place slip out of position during tightening.

Next you need to lubricate! This is absolutely critical drilling metals otherwise you will spend a lot of time either sharpening worn drill bits or trying to extract broken ones! There’s a lot of debate on whats best, for most light work I use WD40 but you will get through it quite quickly as it will tend to vaporise with the heat, this is good in that it helps cool the metal and cutting tool but it must be replaced with more. With deeper holes or larger diameters I tend to use 3in1 as it seems to work well. For the hole saw here I actually started using car gearbox oil, this slows the cutting but protects the tool.

Once you have a pilot hole swap the small drill bit out for the hole saw, make sure you have the speed slow, cover everything in lubricant and gently start to cut. This will take a considerable amount of time, be patient and regularly stop the drill and clear the cut debris away from the saw. Try to avoid using your fingers to do this as the edges can be very sharp. An air compressor is great for this but I have found that cans of computer air duster work pretty well.

Once you have your main port drilled remove the plate from the drill and file back any sharp edges then use your template to mark the centres for all the other holes, these will then need to be centre punched as before and drilled out to size in stages, I went 4mm, 6.5mm, 8.5mm from what I remember. The only critical one being the final size with the earlier steps being arbitrary. If smaller increments are used the cuts are normally quicker and easier but it adds more operations and so will likely take longer. Also I drilled all the stages on a single hole and then moved the plate which adds many more drill changes but you could also drill all the holes to one size then change drills but this has the added risk of the alignment being off which increases the chance of the bit chattering and potentially breaking but can be done if you’re careful. For the level of precision we really need it doesn’t really matter.

By now you should have something a bit like this! At this stage with the new flange seated in place marking the outside edge of the flange becomes much easier – you simply bolt the flange in place and draw (or even better scribe) round it on the mating side. The flange then needs to be removed and trimmed back to the mark. I rough cut the bulk off this with and angle grinder and then tidied the edges back with a bench grinder. Again working 10mm plate takes a little time but it’s not too bad and the outside edge doesn’t need to be perfect just not look silly or clash with anything and still be wide enough to hold a gasket.

Here’s the result, two respectable looking turbo exhaust inlet flanges. The process for the exhaust outlets was exactly the same but the main port was 55mm diameter rather than 36mm diameter making the process take even longer! If you’re in a hurry get them laser/waterjet cut!

In another entry I’ll be looking at the process of making the custom exhaust gaskets I need to match.

RX8 Project – Part 11, Turbo’s #2 – Wastegates

So now the project is going in the turbo direction I need to be a bit wary with how I do it. The GT1549 turbo’s I chose had positives and negatives. They looked to be exactly the right size for the engine I had, they were fairly common in one form or another and importantly the price was spot on! I still don’t understand quite how but I managed to find someone on eBay with a matching pair of these turbos fully cleaned and rebuilt for £65 each delivered! So that’s the positives, now the negatives, firstly rather than the normal bracket bolted to rear of the compressor housing to hold the wastegate actuator. On these turbos it is actually cast into the housing and so it would make rotating the housing to fit the application considerably more difficult. The second problem is they have a factory fitted actuator which isn’t adjustable more than a small amount and I really didn’t want to start tweaking a completely untested engine with no idea what was going to happen with no way of keeping the boost below the 18 psi wastegate pressure!

So getting over these problems. Having looked at the rotation problem I came to the conclusion I should be able to make them both fit with no rotation changes needed. The backup plan here was to grind off the cast in mount and custom make a bracket using a bit of steel plate if it turned out I needed to later on. This takes us to the wastegate problem. I looked at a number of ways of providing a reduction in the actuator pressure including adding springs to the rod side of the actuator and even bolting the internal wastegate solid and fitting external wastegates to the manifolds I came to the conclusion the only real way of giving a wide but reliable range of adjustment while keeping the package as small as possible would be to replace the stock actuator with an aftermarket adjustable one.

Now this is where the plan goes a bit wrong about – after looking about for ages to find a sensible option at a half sensible price the best I could come up with was this : Kinugawa Actuator

I’m under no illusions here, this is a a cheapo unit! But I strongly object to spending the cost of the car on each wastegate. The problem is even though I got these for £68 each which really is very cheap they actually cost more then the pair of turbos! Considering all this it’s still a pretty good option because it is a ‘universal’ version. It comes with a range of springs for different pressures so I can start at just a few psi and swap the springs out as needed and also comes supplied with four different actuator rods.

So here we are – actuators!

So at first glance they look ideal, but don’t let that fool you! There’s a couple engineering problems to overcome.

The first problem is this; the hole in the supplied rod end isn’t large enough for the flap actuator on the turbo. The solution is simply to drill this out to fit. I didn’t note the sizes, but it was a standard drill size.

Next up was that this ‘universal’ actuator was never really intended for a turbo this small and as such the shortest actuator rod is too long to allow the wastegate flapper to close so I had to modify that as well. The rods are nominally 6mm diameter but the end the rod end has a fine pitch thread meaning modifying that would need me to buy a fine pitch die to extend the thread. Luckily the end that goes into the actuator is a standard M6x1mm metric thread so that was the easier option.

I measured how much I needed to shorten the rod to allow the flapper to just close at one end of the rod ends adjustment. The opening pressure of the actuator is set by preload so the more it is tightened greater the boost pressure. I then simply cut the thread down to the required point and then trimmed off the excess. The good news is if I made the rod too short I three more tries for each one!

And here is the difference – it’s actually about 25mm less than it started out! Reassemble the whole thing and magically it now fits where it needs to!

The other thing you will need to do potentially at this point is change the spring. Once the actuator rod is in the actuator this is actually not too bad but be a bit fiddly. First of position the actuator so the rod is sticking downward between the jaws of a vice. Tighened the vice to hold the rod in place then undo all the housing screws. Lift off the top housing and carefully remove the diaphragm underneath. Next you need to carefully release the rod to take the load off the spring. then you just unscrew the rod and take the aluminium piston and the spring underneath out the housing. Reassembly is just the reverse but the key is to put tension on the rod again and clamp it in place again before refitting the diaphragm and cap otherwise it’s very difficult to get the diaphragm correctly positioned without any wrinkles that could cause damage or leakage.

So now we have two turbos with adjustable wastegate actuators with a potential working range covering something like 3-30psi!

RX8 Project – Part 10, Turbo!

So this is about the time this whole project started getting a bit out of hand, when I decided I was going to need more power…significantly more.

I looked into what options I had –

Option 1 – I could stay naturally aspirated and probably skim the head to increase compression a bit and get more out of it but tuning in this way can be very intricate and looked to be more involved than I wanted for the amount of power I could expect.

Option 2 – Supercharger, there are a few options here. Realistically the most common supercharger these days the Eaton M45 found on the modern Mini cooper S is just too small for this so sticking with the positive displacement type we can get an M62 from a mercedes CLK230 and with the right pulley ratio it would probably be ideal for moderate improvements. For real degrees of silliness an M90 might well be needed and these are a little harder to find.

Option 3 – Turbo, this gives a huge amount of options due to the prevalence of turbo engines at the moment and would give potential for significant power gains comparatively cheaply and without needing to align belts.

After debating for a very long time the best way to go for a road car I settled on option 3 primarily for the simplicity aspect – I know very little about the intricacies of high compression engines and I know superchargers require a level of alignment very difficult to achieve with DIY manifolds! The next obvious question is how much power? Well following finding out from Noble that the rods in the engine fold up at something a bit over 300bhp I decide that from a cost and complexity point of view I’d aim for about 280bhp as a limit so I could keep the amount of parts I needed to a minimum – famous last words!

Now there’s a huge online argument about whether two smaller turbos or a single larger one gives the best throttle response and performance. This isn’t an argument I want to get into but in my case I decided twin turbo was the way to go for two reasons. Firstly because I could close mount them under the engine to keep the overall engine package as small as possible and so simplify the pipework on the exhaust side. Secondly because due to the government publicising the benefits of diesel there are now loads of small cheap turbos about for very little money..

Getting into sizing most of the information is that Noble used two T25 turbos. Taking a look at http://www.boosttown.com/forced_induction/air_amount_calculator.php

We can see that for this engine at 6000 rpm and 0.7 bar of boost we need about 27 lbs/min of total airflow. Next we need the T25 Map for a common inducer size:

Looking at the map for the normal T25 turbo we can see that with two turbos to share the load and so only needing about 13.5 lb/hr at 1.7 pressure ratio the turbo is right in its optimal zone. Not a bad choice all in all but these are old design turbos and as a twin turbo configuration the actual amount of available exhaust will be limited so the turbo may not spool until a bit high up the rev range so I started looking at other options which would give a good improvement across a wider rev range. To achieve this a smaller exhaust housing was needed and this is where the diesel engines come in. Turbos used for diesel engines tend to have smaller exhaust housings for this very reason and they’re abundant. This led me to the GT1549, this is a manufacturer specific version of the GT1548 turbo, people have reported them to be good for 180-200bhp which is right in the area we want.

In many ways a similar map to the T25 but the spindle speeds are noticeably higher. The unit as a whole is much smaller but will have less weight in the rotating components and as a result of the smaller exhaust housing the turbo should generate boost at lower RPM. I used to have a map for the exducer which confirms this but have since misplaced it. Now before anyone tells me “you can’t use a diesel turbo on a petrol” consider this – this same turbo was used on both a huge range of diesel engines but also on the Saab 9-5 V6 petrol. That said there is also a VNT version of this turbo (GT15xxV), VNT turbos don’t last long on petrol engines by all accounts.

So here we are, the turbos :

So there you have it, a short post but a complete change in the direction of the project from where it started off and we’re only just getting started!

Engineering – Removing Stuck Bolts

This post seeks to record the ways I generally go about removing a stuck bolt using a particular repair I did – Skip further down if you don’t want the background.

I recently agreed to help out a friend with her first car which she had bought for a few hundred pounds and then found out how much a cam belt replacement actually costs when you get a garage to do it!

The car in question was a fairly common 2004 Fiesta 1.4 – this is the Ford Sigma engine which was also used in the Puma and Focus. Having done a few different cam belt changes over the years I figured it would be comparatively simple. Turns out that logic was badly flawed due to a design “feature” included by Ford which makes the job very difficult. This “feature” is a single bolt which can be almost impossible to remove – the crank bolt!

To explain the technical problem you need a bit of background knowledge on how pulleys are normally mounted on shafts. The method normally used is called a Woodruff key, this is a lump of metal which goes into a slot on the shaft. A corresponding slot is machined into the pulley/gear to be driven preventing any rotation. The key can be seen on the bottom left of the shaft in the photo.

Now the problem caused by Ford on the engine I was dealing with was that to save money (machining that slot adds a manufacturing operation) they did not use a key and instead relied solely on friction. The Ford engine uses the crank bolt to not only hold the pulleys on the crank but actually tighten it sufficiently that the friction between the pulley and the crank prevents rotation. The down side being that the bolt has to be incredibly tight so it can be very difficult to remove and if replaced must be absolutely torqued to specification because if it allows the timing gear to slip the engine would likely be destroyed!

Removing a stuck bolt…

In terms of getting out a bolt start small and build up. In this case there’s no chance a ratchet will do it so I started with a normal short breaker bar and an 18mm deep socket (a slighly unusual size not found in most smaller kits) so I had to buy one) and not terribly surprisingly nothing happened. So I got out my big breaker bar – it’s 800mm long so allows a significant amount of torque to be applied. To get clearance to use this I had to use two long 1/2″ drive extensions so the bar could be positioned outside the wheel arch. Again this didn’t do as much as I’d hoped…

Normally at this point the common next step is to put a bar in place resting against a cross member and then crank the engine. This uses the torque of the starter motor with the mechanical advantage resulting from the starter ring gear to apply a very large torque. Unfortunately you can’t do this with this engine because of the above issue with the crank not having a key. The moment the bolt undoes the engine would lose its relative timing and would probably be badly damaged or destroyed. Unfortunately at the time I wasn’t aware the crank had no key so we tried it anyway. After several goes on the starter and still having no luck I thought we might get more force into it by pushing the car rolling and having the driver let up the clutch like a bump start – using the inertia of the car as the force. Astonishingly even this didn’t get it moving (actually very lucky as it later turned out!).

Having exhausted hand tools I contacted a mate of mine who has an impact gun. It was a fairly basic one but rated at 220Nm should give the bolt a good beating and the percussive action will free up a good many stuck bolts but in this case it just wouldn’t do it!

I started drilling small holes in the bolt head to try to relieve some of the friction between the flange under the bolt head and the pulley. The idea being to remove enough material from the back of the bolt such that it relieves the force by the head flexing a little. After quite a bit of drilling and several goes with the gun it became apparent it just wasn’t going to cut it on this one!

Having accepted I needed a lot more force and having few ideas how to achieve this I decided I would finally splash out on a tool I’d been looking at for ages…

http://products.dewalt.co.uk/powertools/productdetails/catno/DCF899P2/

This is a Dewalt DCF899. The torque ratings for it are amazing for something of this size at 950 Nm continuous but it is a bit pricey. That said it will undo almost anything I’ve found and the batteries last forever!

So having bought this beast I gave it a go and after a number of goes at full power and some rust falling out the bolt still didn’t move! Careful inspection of the bolt head showed that the impact gun was hitting it so hard now for a comparatively small bolt head (18mm hex) the steel of both the bolt head and the socket we getting damaged. I made the choice to give it one last go and ended up rounding off the bolt head entirely!

Most people at this point would probably give up but I had one last idea I wanted to try! I realised that an M20 nut could be drilled out to a 20mm round hole and then it would fit over the rounded off bolt head. The benefit being an M20 nut is much larger hex than the original 18mm across flats bolt head at 30mm, this would replace the stripped head and resist a huge amount of torque before rounding off. I also needed to drill the nut half way through to 24mm as the m20 nut was much thicker and I needed clearance for the next part of the plan…At this point a mate of mine turned up so we broke out the welder and proceeded to join the combination of nut and bolt with weld. After a couple false starts where the new nut sheared off because we didn’t use enough weld we just filled up the head with weld as a last ditch attempt and once the whole bolt was glowing cherry red we used the big impact gun and out it came!

Spot the difference! The one on the left is the replacement ready to go in because on this engine the crank bolt should not be re-used.

Subwoofer Project – Part 1, My First DIY Amplifier

This write up is largely just to set the scene for my later forays into audio projects which I will progress onto in later sections but it does ramble a bit!

Some time ago back when I was still a student I realised that most reasonably priced speaker systems consisted almost exclusively of a series of tiny satellite speakers and a main sub which was often comparatively overpowered in order to mask the inadequacies in the satellite speakers mid range. Now there are systems about which actually use pretty well performing satellites with a decent frequency range but these are usually quite expensive making them well beyond my reach as a student and still a bit lacking and so I started working out what I could do.

My first project was based around some ~~amplifier kits~~ I found at a local electronics store on offer so being student with little money I decided they would be a good place to start so I bought a pair of them to provide both left and right channels with the heady heights of 7W per channel! Shortly afterwards I went on eBay to find a cheap and reliable way to power them from the mains to make a self contained unit with minimal risk of death! I ended up buying a job lot of 5 transformers each rated at 12VAC at about 5A, or about four times what both amplifiers would use at peak output! But they were cheap and well insulated (much safer than cutting up a wall adapter and fitting it in the case). Some may ask why I didn’t just use a normal 12VDC wall adapter and just have the amplifier modules in a case – basically I hate the things but it was also because I wanted to be totally sure the power supply wasn’t the limiting factor!

Note : Since writing this post the company I bought the kits from (Maplin) has ceased trading and so the link above no longer works. The kit in question is Velleman K4001 7W Mono Amplifier details can be found here.

Going off on a tangent….

Now all this was going well except one thing, at the time I had virtually nothing in the way of tools I needed to build this apart from the soldering iron – an item my dad happened to see in a skip when a local college was upgrading their equipment back in probably the late 90’s and an item that has been used for every electronics project I’ve done ever since! If anyone is curious it’s actually one of these Xytronic XY9-60A but it’s been branded as a Rapid Electronics unit and is orange rather than the blue shown.

These were about £100 new and my advice is if you know anyone who is starting to show an interest in soldering buy them something like this! There are plenty of even cheaper, decent soldering stations around now due to the greater number of people doing hobby electronics projects at home and it makes these projects considerably less frustrating!

One key thing for me was the temperature control which being an analog control on mine isn’t terribly precise but it’s still a huge improvement over very basic soldering irons and good enough for the vast majority of hobby projects. The second thing is the soldering tip is small and also interchangeable. A soldering iron that looks like a screwdriver isn’t terribly helpful in most cases because it makes even easy joints much harder to get access too. Back during the early 2000’s when the old Nokia phones were popular there was a brief craze of changing the tiny keypad and screen backlight LED’s out for different colours and I actually did several of these with a soldering tip I filed narrower for the purpose!

Now back to the point…

Having no tools I decided to buy something that would cover as many tasks for as little money as possible, so I bought a £20 fake Dremel and an aluminium enclosure and got to it! Some might describe what happened to that case as butchery but at the time I was using what I had. So the case looked a bit scruffy but it did the job! In the process of using the fake Dremel with an abrasive disk the disk shattered and one of the bits flew of and made a mark in my then virtually new monitor but by luck missed my face. Wear safety goggles – they really are worth it!

Taken from Reddit:

View post on imgur.com

I soldered up the kits as per the instructions and then soldered a diode rectifier and a capacitor onto the transformer output to produce DC (like this) and connected this to the two amplifier modules. I used a dual logarithmic potentiometer (variable resistor) for the volume control (one potentiometer wired to each amplifier). This is wired between the audio source and the amplifier input.

A single pot usually has three legs, in the diagram the box represents the pot. The audio in+ and audio in- go to the two outer legs (doesn’t matter which way) with the audio to amp+ being taken from the middle leg. Audio in- and Audio to Amp- are both connected to the same leg.

It’s probably best to point out here while it doesn’t electrically matter which way round you wire the In+ and In- just make sure when doing a dual pot make both channels the same otherwise when you turn the pot one side will get louder as the other gets quieter and you have accidentally made a balance control!

Power came through a panel mounted IEC connector. If you can’t cut panel holes perfectly accurate then I recommend buying these as bolt in types, they normally need M3 countersunk bolts and then a matching nut on back but they offer a much greater tolerance than push fit ones and you wont pull them out! As a bonus they can also be fitted to any thickness of material with either long bolts or if you’re trying to mount into a decent thickness of wood even small screws in a sensible length can be used.

The finished product looked like this:

It’s moved house with me maybe six times and has suffered a bit but it still works ten years on!

As a final note on this, this amplifier is as basic as it gets. The Velleman kits use a TDA2003 amplifier chip for all their functionality and the boards are basically just filtering capacitors for it. These are ok but the main limitation I found is at very low volume they seem to either limit the output power or the frequency response is terrible and all the bass on the audio drops away. As you turn it up the bass comes back which is a bit odd but in some ways actually ok when I was a student as it meant the low frequencies which tend to disturb people at night weren’t so prevalent! I never saw this as a major problem though.

Another point it’s worth considering because very few people actually appreciate it is that 7W per channel doesn’t sound much but it’s quite surprising what it can do – the volume control has lived at 25-30% for most of its life and with the source on maximum you will almost certainly go well above what most would consider a comfortable listening volume. Speakers are rated for sensitivity which is the sound level they generate per Watt of supplier power at 1m distance. The very cheapest speaker drivers should achieve 82db for 1W at 1m so for just 1W of input power we’re talking a sound level similar to a food blender! The issue is that the sound level vs power is not linear, doubling the sound level (+3db) actually requires four times as much power but we have 7W watts and that only takes us up to 4W but clearly another 3dB is beyond the limits of the amplifier but at 85dB we’re at the point where in the UK companies have to supply workers hearing protection. Better speakers can achieve sensitivities of 90dB with 1W at 1m which puts at noise levels comparable to petrol lawnmowers using 4W of power! Higher power outputs amplifiers have their uses but the next time you hear about someones 1kW+ amplifier it’s worth being *very* dubious!

If you want to understand what this is all about I recommend reading http://sound.whsites.net/articles/pwr-vs-eff.htm where Rod Elliot describes the concept of power vs sound level in much greater detail. It gets quite involved but will explain the limitations and realities!

Also for a bit of a laugh have a look at http://sound.whsites.net/project117.htm where he describes what a 1.5kW amplifier would actually look like and involve. Rod is amazingly knowledgable and I have built some of his projects using his PCB’s and used them in my subwoofer project so these will appear in later sections.

RX8 Project – Part 9, Flywheels Part 3

So just to finish of the flywheel section here are the the finished custom parts :

Flywheel spacer on the crank, you can see the black dust seal in the centre covering the new pilot bearing underneath.

A wider shot showing the spacer in position among the currently disassembled state of the engine.

And finally the flywheel itself.

In this photo the ring gear and location dowels for the clutch basket have been fitted.

The ring gear was actually a lot easier to fit than it was to remove because you can just put the ring gear in the oven (at maximum, in my case 250°C+ off the end of the scale!) and put the flywheel in the freezer for an hour or so as well – this may not actually be necessary but you want the most possible room between the parts when you fit them together. If the ring gear snags on the way down it because there isn’t quite enough space it can be a real pain to get it off again. Before installing the ring make sure it is the correct way round – all the teeth should have a bevel on one side to help the starter engage cleanly this goes towards the position of the starter motor! Take the hot ring out the oven, check it and drop it into place as quickly as possible but make sure it’s right and fully seated to the shoulder of the flywheel. Once touching the flywheel the ring will cool rapidly and lock in place.

The dowels in question turned out to be the wrong size, I specified them as 1/4″ diameter (6.35mm) and this is what is still shown on the drawing but it turns out the ones I measured had more rust than I thought and the holes in the clutch basket are actually designed to locate on ~~6mm dowels – something I really should have checked!~~ From what I have since found out this is likely one of the many Ford engines which have special dowels ~~which are (from what I can find out) 8mm on the flywheel side but only 6mm on the clutch side.~~ The correct dowels are actually 6.30mm on the smaller diameter so my original measurement wasn’t actually too far off, I just shouldn’t make daft assumptions! Larger end is 7.97mm diameter by 6.5mm long on the ones I have, overall length is 18mm. Tolerances and fits are not my strong point but I’ll probably start with a 7.9mm drill and hope to press fit them.

For simplicity I recommend buying something like this available via eBay as Cosworth clutch dowels by x-power engines:

I’m planning to modify the appropriate holes on the flywheel to use the correct dowels I just haven’t quite got round to it yet!

I should probably also take a moment here to mention flywheel bolts. The Duratec crank has a slightly unusual thread which is M10x1.0mm (M10 Extra fine). This is as it happens the same thread commonly used on brake hydraulic components like bleed screws. Needless to say the stock bolts are far too short as the engine originally just had a thin flex plate so longer bolts were needed. Now various companies will sell flywheel bolts for almost any engine but not for something like this and they rarely specify the actual sizes of the bolts in a kit so I can’t just buy one for something else that will fit very easily. My solution was find the best standard bolt I could and so I am using some 12.9 high tensile socket cap bolts which I managed to find from a bolt supplier on eBay with the right thread. For anyone who doesn’t know 12.9 rated bolts are the highest rating before getting into one off special items (usually using exotic materials) and they really are very strong. As a comparison ARP gives their flywheel bolts as having a tensile strength of 180,000 PSI. The 12.9 bolts are rated to have a minimum tensile strength of 176,900 PSI – a number close enough it makes me think they are likely the same material! The strength figures for these bolts mean at the size I will be using each bolt can be safely loaded to in excess of 7000kg of tensile load indefinitely with no deformation. Their failure point being somewhere north of 9500kg each! Some time in the future I will do a full write up of nuts bolts and other fixtures it’s worth knowing about.

So that’s my shiny custom flywheel, next time you see it it should be bolted to a rebuild engine with a whole host of custom or cobbled bits on it!

RX8 Project – Part 8, Flywheels Part 2

Apologies for the long delay since my last post (more than a month!), life has been getting in the way of having time to do anything on blog of late. The good news is that the RX8 project has made some progress and this blog is still no-where near the current status so there’s still plenty to come!

In flywheels part one I mentioned how I ended up in a situation where I didn’t really think the cast flywheel was save to modify and how a chance encounter led me to a solution. The problem it presented is I’m primarily an electrical/electronic engineer, while I dabble fairly extensively in mechanical things designing a flywheel isn’t exactly something that comes up every day and the precision was critical so I spent a lot of time making sure I got it right!

Critical aspects as I saw them were the bolt pattern to match the crank, bolt points for a suitable clutch and and very accurate outer diameter to allow fitment of the RX8 starter ring gear.

Looking at these criteria one at a time the bolt pattern is an interesting one. At first glance all the 8 bolts appear to be evenly spaced around the crank on a PCD (Pitch Circle Diameter – this means the centre of each of the holes is placed on a circle). After checking my early flywheel model drawings against the real flywheel I noticed that all the bolts lined up except one which was just slightly wrong; ok, approximately 2mm, enough to be considered very wrong!

This suggested the pattern wasn’t exactly what I thought so I started checking exactly what the error was in different directions to figure out what was going on. After extensive measurement I managed to work out what was wrong, the bolts were indeed on a PCD they just weren’t evenly spaced. For even spacing the bolts would be at 45° intervals but one hole was shifted 4° round the PCD so it was 41° and 49° to the two nearest holes. Combined with a 76mm PCD this made the bolt pattern line up perfectly. This is actually quite useful because it means when the crank/flywheel are balanced they cannot be reassembled in the wrong alignment.

The crank also features a location register to make sure the centre of the flywheel is perfectly centred on the crank. The register is a raised lip accurately machined to a specific outer diameter so there is no lateral slop between the parts, in this case I measured this to be 44.40mm in diameter. when I trial fitted this it needed some emery on the crank to fit but this seemed due to surface rust where the engine had been stored in a damp room for a long time. Your mileage may vary!

Next up we had the clutch, I initially planned on using the RX8 clutch as I thought it would be stronger and have more options later but on further research it turned out RX8 clutches are very expensive indeed and anything other than a stock one gets very expensive very quickly and largely need to be imported so I started looking at other options. This took me back to the idea of using a Mondeo 240mm clutch, they’re cheap, readily available and the stock ones will handle a fair amount of power. Admittedly a stock kit is highly unlikely to last long with the amount of power this project could get to but there are readily available uprated covers and plates that could be used. Plus £50 on a project that may never really work isn’t too bad, £300 for a new RX8 stock clutch is more than the car cost! I also already head the factory Mondeo flywheel to take all the appropriate dimensions from which kept the process fairly simple.

The last issue was the ring gear, this is critical because the RX8 has its starter motor on the gearbox side and when because of this the options are either re-use the RX8 starter or butcher the RX8 bellhousing to allow an engine side starter to fit. For simplicity I figured I’d go with the RX8 starter since I was getting the flywheel made anyway. Starter ring gears are whats called an interference fit on the flywheel. In essence the ring gear is intentionally slightly smaller than the flywheel it is designed to fit onto and when the two parts are either pressed or heat fitted (heating up the ring so it expands and can be slipped into place) together. It is a tiny change in size when fitted and just the friction between the two parts that prevents the ring gear slipping when the engine is started hence why this is rather critical. To simplify this I modelled a nominal 290mm for the diameter of the lip this mounts on but supplied the ring gear to the machine shop and asked them to machine to an interference fit. This led to the following design:

RX8 Flywheel V6 – Machining Drawing

After a lot of double checking with these base measurements I needed to get the correct offset from the crank to make sure the clutch plate is in the correct position to be fully engaged with the gearbox splines. This led to me modelling everything to make sure it would all fit where it needed to:

Here you can see how everything stacks up. Between the bell housing and engine there is a 10mm spacer (grey) this represents the adaptor plate thickness. Clearly the bell housing has been simplified but the overall length is correct and the position of the splines (a little hard to see in the picture) and pilot bearing diameter (the reduced diameter) on the gearbox input shaft are correct.

Unfortunately having got all of this looking right and sent it over to the machinist and work starting on it I realised a couple minor mistakes, one was that I’d not offset the flywheel to match the spacing of the bell housing caused by the adaptor plate (shown above but this picture is from a later version) but related to that I hadn’t checked the offset to make sure the starter ring gear was actually in the right position to engage with the starter!

Turned out it was a little off and actually needed more offset but unfortunately the raw material for the flywheel had been delivered and machining had already begun and sadly it wasn’t big enough to allow for this extra thickness so I needed a new plan. The best I could come up with was to add a small spacer to correct this. Luckily this also allowed an opportunity to include a new pilot bearing location. This is a bearing that locates into the end of the crank to support the engine side of the gearbox input shaft and due to the gearbox adaptor plate thickness and the fact of it being a mismatched engine and gearbox the standard bearing was now too far away to support the shaft.

RX8 V6 Crank Spacer V1

This spacer corrects the problems above and still includes the correct bolt pattern, location diameters to keep everything centred. The 35mm internal diameter is the exact size of the bearing I used. This allowed a suitable bearing and a dust seal to be pressed into place and likely stay there, that said there’s a lip in the spacer to hold the bearing up and once the gearbox shaft is in place it physically can’t fall out. It’s probably worth pointing out here that this bearing only actually moves in use when the clutch is pressed, when driving along in a gear the clutch locks the crank and input shaft together and so the bearing is rotating overall but the inside and outside are rotating at the same speed so the vast majority of the time it shouldn’t experience any wear.

The final product to be coming in part 3!

AMD Crimson Driver Start Bar Problem

Just a quick post to record a solution I just found to a problem I’ve had for ages.

The problem revolves around the AMD crimson drivers when using eyefinity. What happens is the start bar will default to being across all 3 screens on eyefinity setups on boot even when the driver options are set up to force it to the one screen only – usually the centre one. Opening the graphics advanced settings will set it right until the system is rebooted but this is an irritating thing to have to do on every reboot.

I found the solution that worked for me here : https://community.amd.com/thread/192070

Basically what you do is go to the following location

C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp

Right click in the window and click new—–>shortcut.

As the location of the item paste in :

For 64 bit
“C:\Program Files (x86)\AMD\CNext\CCCSlim\SLSTaskbar64.exe” -l -e

For 32 bit
“C:\Program Files (x86)\AMD\CNext\CCCSlim\SLSTaskbar.exe” -l -e

Then just click next and finish. If you run the shortcut now you should find your start bar jumps to the correct monitor and will do the same every time you reboot so no need to manually fix it any more!

Hopefully this will help someone else with the same problem!

RX8 Project – Part 7, Introduction to flywheels

Having decided what engine I was going to use and deciding to keep the existing gearbox so I could retain the factory carbon prop shaft the next logical step was to work out how exactly to achieve that…

First off the engine I had bought was from an automatic and so had a flex plate rather than a flywheel. This is a comparatively thin piece of steel which gives the starter ring gear, which would be on the outside of the flywheel on a manual, a fixing point and also mates the torque converter to the crank. In automatics the torque converter provides the rotating mass to smooth the engine pulses. So the first step was to get a flywheel that would work. My first idea was to take the factory RX8 flywheel which has quite a deep offset (i.e. it is quite dished) which would help correct for gearbox adapters which would space the gearbox off the engine. So I looked into simply machining off the back of the RX8 flywheel flat and drilling the bolt pattern from the V6 crank into it. While technically this would work there are a few problems.

(Taken from here : http://www.locostbuilders.co.uk/viewthread.php?tid=185939&page=2)

The image above shows exactly what I’m talking about, this is a factory RX8 flywheel modded onto a V6 crank. I believe the engine used in this case is the Mazda KLDE. While this all looks good there are a couple of issues. First is that the RX8 flywheel isn’t balanced as it stands, it forms a balanced arrangement with the rest of the engine and so needs modifying. I don’t have a picture of this but the weighted lip on the rear ranges from thin on one side to very thick the other. Aftermarket flywheels get round this by using balanced flywheel and a separate counterweight. Problem two is that the factory flywheel is cast iron, this has an irregular structure and can have flaws and other weaknesses from new but parts are generally made with a factor of safety to account for this but modification in this way will remove some of this additional strength and change areas of stress. I actually 3D modelled this change to see if it would work:

Original:

Modified:

Having modelled this I performed a stress analysis of this based on the force created by the flywheel spinning at 8000 RPM. This is more than redline as it stands but it seemed prudent to plan ahead! It turns out the stock flywheel is only about 20% stronger than required based on the nominal ‘standard’ properties of cast iron. The new version would be below strength at this speed, dropping to 7500 RPM gave something around 102% strength. Not a number I felt confident in at all! Just to make a point here as people argue the safety of modded flywheels a lot (mostly from “I’ve done it and it’s fine”). I’m not saying it will fail modded like this, in fact the numbers suggest it is (just) strong enough here but there is no margin for error even on the ‘ideal’ material and cast iron does vary significantly. A given flywheel might be fine like this for years, but get a weaker one or one with a flaw or even give it a hard jolt when it’s at full revs and it may just shatter. If it does, be somewhere else!

So after deciding the mod wasn’t really the best idea I realised that all I needed was a flywheel that would bolt up and work. A fairly easy task at face value since it turned out the the standard Ford clutch splines (1″ dia, 23 spline) match the gearbox the solution suddenly seemed simple and I just needed a stock Ford flywheel and clutch for that engine. It turns out there were a few variations of the Ford flywheel depending if you went for an ST200, ST220 or just a vanilla V6 Mondeo but the difference between them seems to be some are ‘lighter’ versions to make the more special cars rev a little more freely. This is achieved by leaving out sections of the outer lip on the flywheel. In my case I had no idea if this project would ever work so I bought the cheapest! This is when another problem emerged:

Note the starter ring gear on each. The top is the S-Type flex plate, the bottom is the Mondeo one. It seems the Ford and Jag use a different starter motor as well. Add to this that the Mondeo flywheel puts the clutch far too far forward to mate to the gearbox and because the starter is on the engine side on the Jag but on the top of the gearbox on the Mondeo (because it’s transverse) – something we can’t do on the RX8 as the gearbox is wrong and there isn’t the room in the tunnel the whole idea falls apart! Modifying the cast one seems to be the only sensible option.

Around this time I happened to have a chat with a colleague at work who is a professional mechanical engineer and 3D designer I know through the job I had at the time and explained the problem and he directed me towards a machinist who did a lot of work for him and was well into cars. By chance a few days later this machinist came into the office and as soon as I explained the problem he just said “ah, we’ll just make you a custom one if you do a design”…. So I found myself with the challenge of designing a custom flywheel which as per the machinists recommendation would be made out of EN24 steel. As a comparison changing the models above to EN24 changes the safety factor to something around 300% from memory meaning we can lighten it significantly later if required and not risk weakening it dangerously.

More to come…