Sunday, January 31, 2010

Mini Cooper Clubman Drive Train Assembly

We have finally made some progress on the 2009 Mini Cooper Clubman drive train.  I had nearly given up all hope.  

My history is of course in electronics and software.  Mechanical issues usually result in the use of a hammer at some point from frustration.  This one almost brought out the big sledge.  

We originally contacted VAC Motor Sports in Philadelphia.  They purported to be an experienced BMW repair facility, with a BMW race team, a full line of BMW Mini Cooper parts, and a full CNC machine shop as well.

Who could possibly be better equipped to mate our MES-DEA 200-250 30kW motor to the Getrag 6 transmission in the Mini Cooper?

Well it turns out, just about anybody.  This bunch of clowns held our transmission and motor from July 9 to October 10 without ever touching it.  Then they "estimated" the project at $5500, meaning they didn't want to do it at all.  

We had them ship it back to us.  And at that point had about $1000 in shipping with nothing to show for our efforts.  They DID very nicely offer to sell us the Quaife auto torque biasing differential for the transmission however.

And at $1600, we thought that was a bit pricey.  But I wanted one pretty badly.  So we bought it.

As it turns out, they even got THAT wrong.  WITH the transmission in front of them, they sold us a Quaife that doesn't even kind of fit that transmission.

The photo shows the problem.  The Quaife is taller.  It has 10 mounting bolts instead of 8, and it has an entirely different spline for the drive shafts.

We talked to Quaife.  The Getrag 6 transmission we have, was a mid year model change to the "large housing" - under the same BMW part number mind you.  The only way you can tell is to open the transmission and look.  We did.  They don't match.

So the "experts" at VAC Motor Sports turned out to be a bunch of kid clowns.  And there IS no Quaife for this transmission.

So we got thoroughly skunked on this one.  The Quaife will fit an S model of previous years, so feel free to make me an offer.  This one is beautiful at 0 miles.

My cousin Peewee Erlbacher actually owns a machine shop two blocks from the house and has since 1955.  They mostly machine gears and so forth for very large equipment, trucks, cranes, etc.  He's really quite ingenious and was able to work out how to make some kind of 6 foot diameter gears for an undersea crawler that is used to examine pipeline from the off shore platforms.  This thing is 6 foot in diameter but only about six inches in width and a couple of inches thick.  Anything you do to cut the teeth in it causes it to scroll up like Christmas ribbon from the heat.  He built a jig that clamps a couple or three of them into place in a sandwich and then automatically rotates it and cuts the teeth.  It takes 56 hours to machine this thing.

In any event, he stopped by the garage to see what was up and took an interest in the project. Work was a little slow around the shop, so he offered to make us an adapter and shaft coupling.

It took a couple of months, as we kind of had to work around the million dollar projects he would get in along the way, but I didn't mind too much being the bastard step child in this case.   But the results were worth it.  Highly recommended. Erlbacher Gear and Machine Works.

The photos below tell the story.  We wound up with three pieces:  A transmission plate, a motor plate, and a shafft coupler.

The shaft coupler features an A20X17 metric spline to match the involuted spline shaft on the motor.  The other end mates to the Mini Cooper flywheel.  We added a spacer around the machined shaft that rides on the motor shaft bearing.  This keeps any pressure from bottoming out the shaft in the motor and avoids "mushrooming" the shaft over time which would make it hard to remove.

I've taken some photos and annotated dimensions so all of this can be created at any machine shop if you need it.  I actually failed to document the flywheel mounting holes, as no one actually wrote those down.  But you'll have a flywheel and so it is pretty easy to take those holes and the position dowel from that.

We did do two plates.  In the end, they are just sandwiched together on the two locating dowels, and in retrospect, the entire thing can be machined out of one piece of aluminum.  We didn't originally know how thick the adapter would be, or how long the shaft.  But we do now and the dimensions are for a single piece of aluminum showing all the holes and locations to quite good accuracy.

And once its done its done.  We had to work all this out, but you don't have to precisely.  Take these photos and dimensions to almost any CNC outfit that can cut gears and you're pretty much there. The one technical item you'll need is the fact that the involuted spline is an A20X17 DIN 5482.  It's a kind of unusual European metric spec. Erlbacher actually had to rent a blade of that particular spec to cut the splines on our shaft coupler.  But they are certainly available.

We bolted the adapter plate on to the motor face with some M10 1.5 grade 8 hex bolts.  The adapter is of course counter sunk for bolt heads.

We bolted the shaft coupler to the flywheel and then mounted the clutch disk and pressure plate to that.  Normally, in doing so you want a clutch centering tool.  This is typically just a cheap plastic jobber that costs a couple of dollars that allows you to center the clutch disk on the motor shaft.  As it turns out, they are simply not available for the 2009 Mini Cooper Clubman as yet.  You can get them for previous models of course, but they are simply not available anywhere at this point for the 2009 and it is different - of course.

We had machined a little recess in the shaft coupler to accommodate the transmission shaft, largely because the coupler on the original engine was made in this way.  In doing so,  he kind of had to leave us a center mark in that milled recess and so it was really quite easy to eyeball the clutch into a pretty close center before tightening the pressure plate bolts.

And then we slid the transmission into position on the two positioning dowels and it slid right in like it was made for it.  Actually it was made for it.  We tightened it down with some hex bolts.  And we have a drive train.

Our next step is to fabricate a bracket for the REAR end of the motor to hang it from the right side engine mount.  This is pretty easy.  We'll just use a sheet of 6061 aluminum, 0.90 thick.  We have to do a little cutout for the cable assembly, and drill holes to match the pattern on the rear of the motor.

As the motor is a bit rounded, we'll use 8 ordinary flat washers as "spacers" for each bolt.   And then we mount the bottom half of the engine mount to that.

In this way, the motor will "hang" from a flexible rubber mount at the transmission, and from another one at the other end.

That will leave it rocking like a cradle. We'll also have to refashion our right drive shaft carrier bracket and strap it to the motor.  And finally we're planning a mounting plate running across the front from one structural member to the other.  This will give us a place for a water pump, air conditioning compressor and so forth.  But we'll also use it to put a little sideways pressure on the motor .

We'll cover that installation into the engine compartment in the next video.  Meanwhile, we do have a latest video of the adapter assembly at