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Old 01-03-2014, 08:46 PM
Motorized Bicycle Elite Member
Join Date: Jul 2010
Location: CA
Posts: 1,750
Default Re: Motorized Bicycle Take a Tip...Leave a Tip

I would like to adapt a 5/8 inch shaft on my engine to 3/4 inch driver element of a torque converter system. The driven element that Comet makes for the 30 series is in 5/8 inch but the driver is either 3/4 inch or 1 inch with the key permanently installed on the driver.

If the key was not integrated on the driver, I could make a special key with a one dimension the height being 1/8 inch (the difference between 5/8 inch and 3/4 inch) so that a bushing with the 3/16 inch cut slot would make a nice adapter. The cylinder shape thing with the cut slot, called a adapter bushing you see at Grainger and on Ebay, so that is not a problem.

I could make a special size key or some on Ebay even have a 3/16 inch by 5/16 inch (3/16 inch + 1/8 inch) special size key.

It is just that the Comet 30 series driver element either in 3/4 inch or 1 inch have a permanently integrated key that is too short by 1/8 inch if you are going to use one of these adapters.

There is another way much more involved using a stepped size non-square key made special. It could only be used for the 1 inch driver not the 3/4 inch driver as the permanently installed key in the 3/4 inch would not reach far enough to make it work.

I thought of getting two adapters, one from 5/8 inch to 3/4 inch and another from 3/4 inch to 1 inch and make a special key shaped to go into the keyway on the engine 5/8 inch shaft.

The special key extends through the first bushing and part way into the second bushing.

This would be so that both bushings turn with the engine shaft.

The driver built in key extends 1/8 inch into the 2nd bushing.

The key built into the driver for the 1 inch shaft uses normally a square key of 1/4 inch when not already built in. The built in one then is half the height. That means that 1/8 inch then that goes into the second outer bushing as the integrated key the driver supplies.

Using a mill maybe the key would be sufficient, but using a Dremel tool, hacksaw, and file is what I maybe have to use depending on costs involved.

Anyone had need to adapt from 5/8 inch to 1 inch with a key already built in where there is no option?

Other than that I would look for another manufacturer that does not use a permanently installed key on both the driver and driven elements of a torque converter.


Last edited by MEASURE TWICE; 01-03-2014 at 08:58 PM.
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