# Coupler Pilot/Spigot Bearing



## dillond666 (Dec 27, 2010)

If you are using the clutch I would bore the end of the motor shaft to accept a brass bush, this will be adequate as you will not use the gears that much anyway and you should never be slipping the clutch for hill starts etc.

Cutting the end of the shaft off would be detrimental to the gearbox input bearing.

You could also machine an adapter for the motor shaft which would mimic the crankshaft flange of the engine. this would have a spigot bearing incorporated into the adapter so you wouldn't have the hassle of machining the motor shaft. This would make the gearbox/motor assembly fractionally longer but is probably the best method.


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## skooler (Mar 26, 2011)

dillond666,

Thanks for the reply, I am not sure if this will be possible with the way the coupler has been created ( I haddnt seen it when I started this thread.

Sorry to bring up something from another post but it seems like the answers might be more readily available in this subforum. apologies for reposting

I am now thinking of turning the end of the transmission input shaft to a point - javelin shape and then creating a smaller bore in the motor shaft. There is already a small hole from where it has been in the lath.

These can then push together with plenty of lubricant, no bearing. Thoughts?

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*Coupler and Flywheel
*This is my little breakthrough over the last couple of weeks. stupidly, I forgot to take the 'before' pictures of the flywheel. I will try to describe it! 

It was as below but with a ring gear on the outside and about half inch thick weight on the back, see the second pic and the shiny outside. 










I had the the sprocket that came with the motor converted into the coupler! the gear was removed and 4 additional holes tapped to allow it to bolt to the flywheel. 3 grub screws are then positioned around the outside to assist with locking it to the shaft. The locking nut and washer shown in the first picture are still to be used to lock it to the motor shaft.










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The above picture tries to show the thickness of the flywheel.

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Trying to show the 4 bolts locking the coupler to the flywheel. these are all grade 10.9 to stop them from sheering.

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I kept the 2 threaded inserts to help remove the coupler if ever needed. it provides something to 'grip' to.

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Trying to show 2 of the 3 grub screws in this picture.

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finnished product









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The above shows how the centre of the sprocket has been turned to fit inside the stock flywheel. the RX8 flywheel also has a keyed centre

Forgot to mention. the machinist charged me £50 to turn the sprocket, flywheel and join them together! bargain!


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## DavidDymaxion (Dec 1, 2008)

My gasser has a plain bearing for the pilot bearing. It galled after 100k miles of use (and I suspect the previous clutch job or jobs might have never replaced it, as it was very hard to remove, so it might have been 200k miles of use). The car was difficult to shift into 1st gear when stopped, but slides in very easily now that I have fixed it.

My Porsche conversion has a pilot bearing with ball bearings. My purchased coupler had a spot for the pilot bearing, so I ran with that. BTW the Porsche does not shift as well as the gasser.

Wear in either case is minimal, as the shaft only spins in the pilot bearing during idling or shifting. Once the clutch is engaged the pilot bearing spins at the same speed as the tranny shaft and flywheel, so no relative motion for it.

My humble opinion is to do it the same way the stock car did. If you go with a plain bearing, I would use the same kind of material a plain bearing pilot bearing uses, to prevent galling and seizing.

I would never cut off the shaft. You now have a cantilevered shaft that could wreak havoc on the bearings even if you never use the clutch. BTW I had a Jeep with this condition once. Some idiot had put in the clutch with no pilot bearing. It worked fine at low rpm, but would sometimes vibrate hard at high rpm -- it was a luck thing if everything was aligned or not. It would vibrate hard enough to bang the tranny shaft on the edges of the pilot bearing hole. A new pilot bearing made it work great.


skooler said:


> Hi All,
> 
> I havent posted an update on my RX8 conversion for a few weeks as not much significant has happened - I will post an update this weekend.
> 
> ...


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