# Adapter/Flywheel Fit?



## Yabert (Feb 7, 2010)

PeterH said:


> Is this a problem or am I concerned about nothing?


It's a problem!... 
As you noticed, this is the main way to centered the both parts.
Fraction of inch uncentered will be enough to cause some vibrations. Those vibrations will have bad consequence on motor shaft and bearing.

You will need to rework the hub to fit the flywheel.


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## PeterH (Mar 20, 2009)

Thanks for the quick response! 

Is centering the flywheel the only concern you'd have for a situation like this? 

I forgot to indicate in the sketch that there is a small and very thin walled extension of the adapter that is roughly the size of the motor shaft, that projects toward the flywheel and is sized to fit within the opening at the center of the flywheel (right where the transmission input shaft bushing goes). 

The flywheel inner opening actually has to fit over that extension of the adapter for it to fit. This centers the flywheel. I ran the motor on 12 VDC for a few minutes, after I had installed the flywheel and everything seemed to be centered and vibration free.

Should I still be concerned?

Thanks,
Pete


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## piotrsko (Dec 9, 2007)

yes you need to be concerned. 1: while grade 8 bolts are fairly strong in shear, they suck at resisting any bending forces. your 2nd picture will subject the bolts to a fair amount of bending. 2: at 12 volts, the motor may spin at up to 500 rpm. at 100 volts the motor will spin fast enough that a #4-40 screw set into the flywheel rim will imbalance it enough to make the motor walk around the floor by itself before it explodes.

OTOH, having a hard time installing the adapter means it is a good close fit. a wee bit oh heat will make it move on and off easier.


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## Yabert (Feb 7, 2010)

PeterH said:


> Is centering the flywheel the only concern you'd have for a situation like this?


No, but it's the main concern.
The other concern for me is transmision of torque between both part. Isn't anybody know that, but the torque in this assembly isn't transmited from the bolts in shearing action. In fact, the torque is transmited by the friction create by the bolts between two surfaces.
In your case, the bolts don't compress the surface just behind hers head. Well, depending how in reality the parts are in contact isn't maybe a big deal.





> I ran the motor on 12 VDC for a few minutes, after I had installed the flywheel and everything seemed to be centered and vibration free.


That is fine at 12v unload, but it can be another story when it will transmit full torque. You know better than me if your assembly will stay concentred.


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## PeterH (Mar 20, 2009)

Thanks everyone for your thoughts on this. Since machining the adapter so there is a flush fit will change the distance between motor and the clutch plate/flywheel face I'll contact the shop that did this work and verify their intentions. Then I'll either have the adapter machined locally or replaced entirely. 

I'm getting good at installing the adapter on the motor shaft...this will be the third time!

I'll also update this thread just so it is complete all the way thru to the final solution.

Thanks,
Pete


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## Woodsmith (Jun 5, 2008)

To save changing the length of the coupler how about machining out a location recess in the face of the coupler and bolting in a tight fitting extension plug. The flywheel can then be located on the extension and bolted through to the coupler.


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## EV-propulsion.com (Jun 1, 2009)

Your local machine shop may want to re-do the entire coupler, to get that coupler re-chucked in the lathe in the exact same concentric position will be difficult, or at least time consuming...


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## piotrsko (Dec 9, 2007)

I like woodsmiths answer, just make an adapter adapter style plug for the flywheel backside. Use 3/8 dia holes drilled through, doesn't have to be anything but close enough in diameter to the flywheel.


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## Guest (Dec 14, 2011)

Have the original maker re-do the adaptor at no cost to you. They screwed up, right? 

Pete


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## dtbaker (Jan 5, 2008)

PeterH said:


> In the sketch on the left, I've tried to show how the original crankshaft fit within the face of the flywheel. Notice the red circle highlighting the way the original shaft end sat in the recessed center of the flywheel.
> 
> Now, look at the sketch on the right and at the red circle. The new adapter was machined too large to fit in the recessed center area in the flywheel.
> 
> Is this a problem or am I concerned about nothing?



this is bad, and the shaft adapter should be re-done to insure a concentric fit, and one that will not rely on bolt tension to keep everything balanced. If the shaft adapter had a correct shoulder to set both the axial face depth of the flywheel/clutch AND concentrically.... you'd be in business. as it is will be an eventual nightmare, and tough to balance as it will require everything to be mounted and spun up on your motor and balanced 'in-situ'. not good.


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## Zappo (Sep 1, 2011)

Woody has a great solution. If possible, take the adapter and flywheel in to your machine shop along with your sketch and woody's concept. If they are a good machine shop, they should be able to fix you up just fine. I strongly agree that you don't want to run it that way though. I'm sure it would turn out pretty catastrophic.


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## skooler (Mar 26, 2011)

I thought you may be interested in how I did mine.

Its not too far away from your idea.

link below:

http://www.diyelectriccar.com/forums/showthread.php?t=65096

Cheers

Mike


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## PeterH (Mar 20, 2009)

gottdi said:


> Have the original maker re-do the adaptor at no cost to you. They screwed up, right?
> 
> Pete


Boy... I like that idea... learned last night that they never even looked at the flywheel that was sent with the transmission... this is just a 'stock' adapter they sell to everyone. The custom work was in the two plates that mate the motor to the transmission bell housing.

Since the shop was concerned with the "magic number" describing the distance between the end face of the crank shaft on the ICE and the engine block, I have to assume that they intend for the new motor shaft adapter to sit flush with the recessed portion of the flywheel. That means that I need to have the adapter machined down to fit in that opening to restore the correct distance.

I hope to pull things apart later today. If so, I'll grab a bunch of photos to illustrate the issue more clearly. Again, just so this thread has a complete description of the problem and solution to help some poor builder who follows avoid the same problem...


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## PeterH (Mar 20, 2009)

Ok, got it all fixed up... took the adapter to a local machine shop and it was done and ready to be picked up before I even made it home.

you can see below how much wider the adapter is than the opening in the flywheel.



















It cost me $20 to have the adapter machine. Was very happy with that little turn of events...



















That should bring this little thread to a close. If you ever run into this situation, you can now see how I fixed it.

Good luck!
Peter


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