# How to make a motor shaft adaptor?



## Woodsmith (Jun 5, 2008)

I am looking to achieve the same thing with whatever motor I get. I am keeping hold of the crankshaft in case it is useful but I think I iwll be making up the whole thing from scratch.

A simple way is to get a taperlock chain sprocket to fit the motor shaft. The type where the sproket is a large flat disc with the taper lock on one side.
Machine off the sprocket teeth and make the face of the remaining disc flat and true.

Machine a round steel blank to the diameter of the crank end and then machine the small diameter lip to centre the flywheel. 
Then index and drill the mounting bolt holes and tap to fit the flywheel.

Machine the other side of the blank to give some sort of location to the taper lock sprocket. The relative sizes of each would decide the best method.

Drill and tap each so that the two parts can be bolted together. That would give you a taper lock to the motor shaft with a flange and an adaptor that can be bolted to it to fit the flywheel.

If you are lucky in the dimensions then you can use the flywheel mounting bolts to the flange and skip the adaptor.

Machining the end of the crank shaft may be a little tricky if it has been heat treated and is hard.
If you can then you would need the end of the crank and the length of the main bearing too.
It can be cut off at the crank web and then machined to form a true face at the cut end.
The centre can be drilled out and then a key way cut inside by whatever means the machining shop has. 
Grub or set screws are then used to fit the adaptor to the shaft. 
Generally I would guess three pairs of screws equidistant at 60 deg apart around the main bearing diameter with one pair on the key. The other two pairs could set into small dimples drilled on the shaft to locate it axially.


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## piotrsko (Dec 9, 2007)

cutting the crank may be the fastest and easiest, except for the motor dissassembly to get it out. cranks aren't necessarily hardened beyond .002" deep. take a file and gently just nick part of the flange before you start. if it nicks easily, it is soft enough for you to do work on it at home. You will have to probably cut the last journal in half to get enough to grab for machining. If you pull the pilot bushing in the crankshaft end but not replace it, the trans input shaft will wobble and destroy the input bearing in the tranny. So when you bore the center hole for the motor shaft, it will need a pilot bearing machined from oilite or kevlar. You didn't indicate if you are running a clutch, but showed a flywheel installed and I didn't see the clutch lever. It might just be easier to take the flywheel and motor to the machine shop amd let them fab something. Most small shops can deal with this easily. might cost as much as $300 usd however.


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## Woodsmith (Jun 5, 2008)

I am getting very tempted to use the end of the crank now, having spent a bit more time looking at my costs. I don't want to buy any more stuff unless I have to.

I have the advantage that the MR2 transaxle doesn't need a pilot bearing though that also means that the motor/flywheel assembly needs more accurate location.


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## Drew (Jul 26, 2009)

From what I can see all you'd need to do is go to any place with a 3 axis mill and ask them to fab you one up out of solid round stock.

The details you'd need based on the picture would be the bearing seat diameter for the bearing in the center as well as the pitch circle diameter for the holes on the outer circumference and their diameter or thread size.

If there are any other interfacing areas on the end of the crank then you'll need those as well, but from the look of it and with the even hole count it should be very simple to sort out.


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