Monday, August 7, 2017

...And flywheel solutions!

I removed all the dowel pins from the crankshaft, which wasn't super difficult this time around... I think my holes are a light press fit, rather than the super-tight holes that were there originally. I'm not sure if that'll cause problems down the road or not; they are still a press fit, so load should (theoretically?) be transferred just as effectively.

The flywheel face on the crankshaft seemed to have zero runout when sitting in the crankcase, but there were a few problems with how I was taking that measurement that could have absorbed imperfections... so I decided to throw it at the lathe and check runout by painting the face with red dykem and scraping a tool along the face. The goal was to avoid removing any material, just rub the dykem off, and see if it was a gnarly edge on a dowel hole that was causing issues, or if the face itself was not perpendicular to the axis of rotation. I thought I took a picture of the result, but apparently this was another instance where my phone shut off instead of taking a picture... that's been happening a lot recently.

Anyways, the dykem was scraped off of about half the face, and the other half the dykem was still there; it made almost a perfect half circle of red and a half circle of steel. Now, the crankshaft was out about .0005 on each end, and I failed to document whether it was out the same direction at the same point in rotation; so when I did the math, I had to assume worst-case of the crankshaft being out a full thousandth of an inch. Even so, the pattern was much too extreme to blame it on a misalignment of that magnitude, so I turned a couple thousandths off the entire face. When I re-attached the flywheel, it was only out about 1 thousandth of an inch as opposed to the 8 I had before, so I put the dowels back in and put the flywheel back on. I put the whole thing on the lathe as an assembly, because I have to do a little more work on the flywheel.

Now to the part I have pictures of! The final flywheel is going to be two parts riveted together. The inside part will be turned from the original flywheel, and the outside is from a much lighter flexplate (which basically just positions the ring gear and transfers the load from the starter.) I cut the inside out of the flexplate on a CNC mill at work, since it was too big to turn on the lathe.

I also cut the outside off of the flywheel on the mill, but left it oversize so I could finish it on the lathe.

I could have programmed the mill to cut a circle, but I wanted to use a rotary table to get a true circle on the flexplate, since I can't touch that up on the lathe. Once I was set up to do that, it was just easier to do the same with the flywheel.

Once the flywheel and crankshaft assembly were on the lathe together, I started working towards the final shape. There's a step on the outside of the flywheel that needed to be turned flat with the rest of the face, and then a new step needed to be cut out from 5" diameter outwards to accept the flexplate. I've got the whole thing turned flat, and I used some red dykem to help me visualize where that 5" diameter will be.

It's been a little tough to find time to work on this stuff, but I think I see the light at the end of the tunnel. I have a few more parts on order, and once they get here I should be able to begin the reassembly process... which should be a pretty quick process, given how much documenting and adjusting and tweaking I've done *before* started to put it all together.

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