# Clutch thrust? Hardened crank?



## Greenflight (Sep 13, 2007)

Well, you're making me think here. I didn't do anything special to my motor, and I'm running it with a clutch. So far I've run it 1700 miles that way, without any problems. I haven't noticed any issues with it so far. I had the opportunity to take it apart at about 500 miles (motor shorted internally) and the bearings seemed perfectly fine. It doesn't seem to have any difficulty with it. We'll find out eventually.  

I think using the end of a crank is an awful lot of trouble to go to. Couplers just aren't that tough if you have them made by a machinist. Both the one for my truck and the one for my Tercel cost under $300 and they're made out of 4140 steel. Both use 1 1/8" shafts with a 1/4" key, two setscrews (each backed up with another setscrew), and loctite. So far, no problems.

I'm interested to hear what others say about the clutch issue. I really never thought about it before.


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## Pb Cruiser (Oct 29, 2007)

I posed that same question on another DL and the response I got was that the motor bearings suffered no unusual wear. Mind you the clutch is not used near as much as in an ICE situation; but yet and still ball bearings don't like axial loads. I plan to retain my clutch only because I think it will be easier and stronger to couple the motor shaft to the input shaft of the 5 speed via the flywheel/clutch disc. My plan is to drive in 2nd or 3rd gear all the time and maybe downshift to negociate a hill.


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## Nick Smith (Oct 26, 2007)

Looking at the ADC motor diagram it would appear that it utilises standard deep groove bearings which look like they would be in the 1" (25mm) sort of size. The allowable axial loading on these bearings (assuming bearing 6205) is something in the order of 200kg (440lb) as a maximum for a reasonable life. (I am working with a metric SKF bearing catalog here). I know that clutch plates do have a pretty good loading on them but I'm not sure it would be quite as high as that. If you were really worried it would be possible (with judicious application and depending on what the original bearing actaually is) to change the loaded bearing for a spherical roller bearing (say 22205) which would increase the axail load to 900kg (2000lb)! This may or may not require machining modifications to the motor end plates.

Alternately it would be possible to place a thrust bearing between the motor end plate and the clutch adaptor hub. Again this may require machining modifications but you would also need to ensure that the bearing was always loaded to prevent "skidding" of the balls. This can be achieved quite simply with a belville (tension) washer.

The thing that worries me is that most people seem to rely on the grub screws to prevent the hub slipping down the input shaft under clutch loading! I have read of one person who did this and ended up grinding the end plate of the motor away. I always prefer to machine the hub with a step to prevent it slipping down the shaft. This necessarily involves machining the key to the bottom of a blind hole (which is possible) but it costs more than broaching a key right through the hub.

As far as materials for the hub goes 4140 (per Greenflight) is a sweet material but 1040/1045 medium tensile steel would be well within specification for a properly designed adaptor.


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## Greenflight (Sep 13, 2007)

Yeah, I doubt that the force of engaging a clutch is over 400 lbs. I'd be very surprised.

My Mazda has two set screws and a key, and no step to keep the hub from sliding on the shaft. In retrospect, this wasn't the smartest design I could have used, although so far it hasn't caused any problems. My Tercel's hub is similar, except the bushing that was made in place of a pilot bearing has a step on the edge, which is retained by the flywheel. This is probably cheaper than having a step machined into the hub istelf. Check out the pic to see what I'm talking about.


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## Nick Smith (Oct 26, 2007)

Greenflight - Your idea looks like an inexpensive way to achieve what I was talking about. A heavy duty internal snap ring is another way that would work well too.


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## Greenflight (Sep 13, 2007)

Yeah, that would work fine too. I like mine because it takes care of the pilot bearing, but either idea should work fine.


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