Wednesday, December 31, 2014

Clutch Alignment Repairs

I've had another day to work on the car and made some good progress.  Last I showed you, the driveshaft was high compared to the motor shaft.  I took some closer measurements and it's hard to tell, but I've estimated that the shaft is about 0.045 inches off center.

The bellhousing and motor adapter are located to each other with alignment "sleeves" at two of the bolt holes.  These locations need to be moved by 0.045 inches, but that's easier said than done.  I decided to punch out the alignment sleeves and replace them with relocated pins.  You can see the two housings here.

Getting a pin pressed in the adapter and aligning it with a hole in the bellhousing in the perfect spot is a little tricky.  I finally decided I'd make a couple special plugs to do it.  You can see them in the picture below.  Each one has a diameter that tightly fits to the locating hole in the bellhousing.  Then the diameter of the other end of the plug is 0.090 inches smaller than the corresponding hole in the adapter plate.  That way I can put them together and shift the adapter plate within the clearance of the plug in the correct direction.  Since the radial clearance is half the diametral clearance, it should move 0.045 inches.  The plug on the left is in the alignment hole.  You can see the two diameters on the loose plug on the right.

After that, I drilled a 5/32 hole through the adapter plate and slightly into the bellhousing.  Now that the holes are lined up with each other between the two housings, I opened the hole in the adapter plate just enough to press a 3/16 pin into it, and opened the hole in the bellhousing so the pin just slips in.  Here you can see the pin pressed into the adapter plate.  In the above picture you can see the hole it mates with in the bellhousing.

Now it's time to test the fit.  I put the adapter plate back on the motor, put the bellhousing back in the car, and put the motor back in with it.  The bolt holes that hold everything together have enough clearance that the bolts still fit through.  And here's how the shafts line up after the new alignment.  Not perfect, but a huge improvement.  I was able to shift the joint between the bellhousing and the driveshaft tube just enough that it looks perfect to the eye.  Considering 0.045 looked pretty bad, I think it ought to be good enough.

So now it's time to put it all together again.  I pressed the pilot bearing into the coupler (shown below), lubed it up with some bearing grease, and remounted the coupler, flywheel, new clutch disc and pressure plate.  Then I put it all in the car along with a new throw out bearing.  

By this time I've put the motor in and out of the car about 4 times in one day (not counting the dozen times I did it the last time I was trying to fix this problem) and I'm really hoping this is it.  Two years ago when I spun up the motor, something in the driveshaft assembly (probably a bearing) made this nasty, loud, clacking noise.  This time I hooked the motor up to 12v and the spinning makes a noise more beautiful than a chorus of angels playing harps!  No laugh of a child, purr of a cat, or chink chink chink of coins dispensing from a slot machine could melt my heart that day like the soft whirring of the brushes in the motor did.  This problem was in my top 3 issues making the car a pain to drive.  Time to finish putting the car back together and tackle the other two!

Oh and happy new years to all of you!

Monday, December 29, 2014


It was a pretty good year for driving the electric car.  My goal was 5000 miles, and I made it to 4893.  I was on track to make it, but the Tuesday a week and a half before Christmas, something happened on the way home.  At first I noticed a very subtle looseness in the steering that would have been imperceptible if you hadn't been familiar with the car.  Then I noticed some brake squealing coming from the front driver's side wheel.  Finally I notice the speedometer isn't working!  I know the speedo cable attaches on that same wheel that the noise is coming from, so I figure the end of the cable broke off and was somehow scraping on the brake rotor.

I got home and pulled the wheel off.  To my surprise, the entire rotor assembly was loose!  The wheel mounts to the rotor, and rotor is supported by a pair of wheel bearings.  One of the bearings was completely pulverized, and the only thing keeping the wheel from falling off was the brake caliper!  Yikes, I dodged a bullet there.

Meanwhile, I've been planning some maintenance on the car for the Christmas break, so parking the car a few days early isn't a big deal.  When I put the car together a year and a half ago, I had to fit the motor in and out a number of times and I was using the old clutch to avoid banging up a new one.  Well, before I knew it, the car was all put together with the old clutch and I wasn't about to tear it all apart to replace the clutch.  Well, not too long after I started driving, I began to hear some clutch noise.  It started slow, and eventually got worse and began to vibrate.  I decided it was time to get a new one in there.  The biggest downside is it requires removing either the front or rear set of batteries to make the swap.  Here I've got 24 cells removed along with the BMS.  No turning back now.

2 hours of work later and the motor is pulled out enough to remove the clutch.  When I pulled the disk out I was expecting it to look pretty bad and I was a little disappointed that it looked okay.  Not bad enough to be causing me all the issues I've been seeing.

I dig a little deeper, and here's the problem.  The pilot bushing in the flywheel adapter is totally worn out!  Not a good sign if this needs replacing every 5-6k miles.  Something more significant must be wrong.  For that, we need to jump into the way back machine for the rest of the story.

About 2 years ago I was spinning the motor for the first time and excited for the day I get to finally drive the car.  When I first mounted the motor in the car and spun it up, it made a fairly significant clicking noise.  I don't recall if I blogged about that, but I had the motor in and out a dozen times in an attempt to fix it, mostly working on improving the pilot bushing.  Nothing I did seemed to fix the problem so I started to suspect there was an alignment problem between the motor and the bellhousing.  I loosened the mounting bolts a bit and used a jack to lift on the motor adapter to see if that made any difference.  What that did was change the angle between the motor shaft and the driveshaft.  I found that a very slight angle made a significant improvement in the noise, so I shimmed the joint and bolted it up.

The noise was all but gone, and I didn't look back because I was finally on the road.  Deep down I knew it was a bogus solution, but my desire to get the car rolling after 20 months of work was overwhelming so I chose to ignore it.  Well, apparently my days of looking the other way are over, and I find myself in the same spot I was in Feb of 2013.  What to do now?  Well, to start I need to fix the pilot bushing.  The original Porsche used a pilot bearing.  I didn't try this because I assumed it wouldn't fit with my flywheel coupler design.  Too bad I never checked the dimensions because it actually is smaller than the bushing I made!  With the increased load capacity of needle bearings vs. the phosphor bronze bushing, this ought to last longer.

My neighbor happened to be working in his garage the yesterday, and it also just happens that he is a professional mechanic and builds race cars, so I stopped by with the coupler to see what he thought.  He took one look and said the motor shaft and driveshaft centerlines aren't lined up.  He'd seen it a dozen times with poorly made motor adapters.  He sent me back home with a homework assignment of taking some careful measurements to figure out where the problem is.

I'm lucky enough to have an inspection panel on the clutch housing, so I have a 4x4 inch window to look at the parts.  Without the clutch and flywheel in place I can get a good view of the driveshaft and coupler.  I put the motor back in place and had a look.  Note that I've opened up the hole in the pilot bushing to accept the new bearing, but haven't pressed the bearing in yet.  Here you can see from the bottom that the shaft lines up fairly well left to right.

You can see a side view from the inspection hole, but I squeezed the camera in there and took a picture from the left side.  Now it's obvious there's an alignment problem in the vertical direction!  As unfortunate as it is to have this problem, I'm ecstatic to find a concrete problem that I can now solve!  Instead of being a poorly made adapter plate, I'll call this a poorly designed one since I took all the measurements.  Reworking the adapter is going to be interesting, but I've still got 7 days of vacation to figure out how to do it.  Better get working...