Friday, March 7, 2008

Flywheel Mounting, Part 2

After much discussion, and lots of doodles, I think I have my final answer. The various factors which contributed to this include:

  • I definitely want to use the original manual transmission (it will feel too sluggish otherwise)
  • EA does not have a prefab kit for the Jeep
  • I like having the splines meshing with the hub
  • I want to minimize holes
  • The splined hub must allow the compression effect of the taperlock
  • Machining should be as simple as possible
So, I came up with this idea. Basically, the splined hub gets machined down slightly to a shape like two truncated cones stuck together base-to-base and then cut into 4 segments:

Next, I create two nearly identical outer hubs, 4 inches in diameter - the six holes are intended to match the bolt locations on the flywheel itself. The center hole is slightly tapered to match the newly machined hub. The bottom of the two hubs is threaded to accept the bolts (that's the only difference between the bottom and top hubs). And that's it:

The inner and outer hubs mate like this. The unthreaded top part goes next to the flywheel, the threaded bottom part goes on the other side, and the flywheel bolts hold the whole thing together. The assembly plan is to position and torque down the hub without the flywheel attached at first. The compression / friction caused by torquing it all together should hold it in place when the bolts are removed. And then the flywheel is put on and torqued to the proper specifications.

A PDF version of all these is available here. One last note: I did a calculation, and I believe that the hub will compress properly if cut into four segments this way. Calculations (based on the angle of the splined hub facets) show that the direction of compression will be offset about 3 degrees from directly toward the center of the shaft. I don't believe this will cause any issues.

Comments and suggestions welcome...


Roy said...

Dad said,

Sounds as if it should work nicely. The only concern I might have is the extra weight that you are spinning at 3500 rpm. This extra weight would cause a dampening effect on the rotation of the flywheel. In turn, the flywheel possibly would be a little bit sluggish to changes in rotation direction.

jk.kunka said...

You just invented the shrink disc. They are fantastic replacements for shaft keys, transmitting high torques. We use them in many applications in my field. I have PDF catalogs if you want to compare the size of yours to a standard unit - email me for a copy.

The inertia of your assembly is minuscule compared to your flywheel - I wouldn't worry about sluggishness.

I love your project, having stumbled on the same motor/drive in consideration for a conversion of my Tacoma.

Aaron Proman said...

It appears that in the end you used the taper-lock from electroauto, correct? Still have the two HubCity Splined Hubs?

Ross Cunniff said...

Yes, I did end up using the ElectroAuto taperlock. I still think this is a good design, though.

Yes, I do still have the splined hubs. They make very nice paperweights :-)

Aaron Proman said...

Interested in selling them?

Ross Cunniff said...

Possibly - send me email to my last name at