Hello everyone.
...............................................
This thread actually started a few days ago on the general engine discussion forum, but it seemed like it really belonged on this forum, so here it is.
How to fit mismatched rings and piston and cyl bore??
................................................
I have wanted to build a diesel for a long time, actually a 2 stroke complete with Roots blower. Why not bite off more than I can chew? I call it being greedy; and it usually gets me in trouble. EDIT:I have since revised my expectations and have dropped the blower and 2 stroke concept.
About a year ago, I found Find Hansen's beautiful engines on Youtube, and that almost pushed me into the project. Then I ran across his new video of the build of an A-Frame diesel. Darn! Then I found this great forum with lots of smart and helpful and friendly members. That's a rare combination to find on the internet! So I dove in head first.
The selection of 33mm bore x 66mm bore had an odd beginning. In one of my junk piles I had some short pieces of 8" welded steel pipe (actually 8-5/8" O.D.). I thought, that could make a great flywheel, what size cylinder would it go with?
So the first item is the one that for me, took the least amount of decision making. Like using 4 spokes or 5 spokes? The 5 curved spokes spoke to me. It is bolted construction, with inner and outer rim, 5 spokes and a hub, and hidden bolts.
I started by slicing off 3 pieces of the 8-5/8" O.D. x .30 wall welded steel pipe: rim, inner rim, spokes. I used a Harbor Freight $120 portable band/hack saw and had to saw all the way the way around each ring. I sawed them all in one session, using plenty of oil on the cuts. The Lennox blade held up fine. The saw didn't whimper.
My lathe is a Grizzly 10x22 and that pipe definitely pushed the limit, but I got the outer rim roughed out, clamping from the inside out with the 6-1/4" 4 jaw. Indicating the rings in to get them to run optimally for least amount of material removal was a chore. The outer ring was the first part rough machined. To make the inner spoke ring, I sawed out a 2" section of one of the pipe slices, and clamped it to force it into an 8" O.D. Then I welded it, multiple passes, grinding out the flux and inclusions between passes, One thing that really helped the welding was preheating the joint area with a Mapp gas torch. Welding that 5/16" wall just wouldn't have worked, not a my skill level anyway. Then I rough machined the new not trying to get 100% cleanup.
I machined the last ring to the finished cross section of the spokes.
The hub was rough turned from 12L14. It has an O.D. groove the width of the spokes, and has 5 flats machined into that groove.
I rough cut the 5 spokes to length plus about 1/8". It is bolted construction, with each spoke attached to the rim with a single 8-32 bolt, with the head counterbored into the rim. After all 5 spokes were attached to the rim, I fit them to the hub and determined how to trim the ends of the spokes and install the bolts.
After it was all lightly bolted together I chucked it in the lathe and pushed it around to get minimal runout and wobble, which ended up being about 30 thou. I tightened the bolts up, using a generous amount of 680 loctite. I then trued it up ont he lathe, changing the chucking at least 4 times.
Then the outer rim was attached using (5) 10-32 set screws that fit into pockets on the I.D. of the outer rim. After it had a final alignment, one last set of clean-up cuts were needed to get the non-painted surfaces all pretty looking. Lastly was several sessions of epoxy and JB Water Weld. I was shocked at how well that combination worked. i cleaned with acetone, and lightly preheated before applying epoxy, and used a heat gun to get the epoxy to flow properly. If this wheel were dropped hard enough to break it, I think a cast iron one would have broken too.
Here are the final as-built specs for the flywheel.
Outer rim O.D. 8.58"
Outer Rim width 1.99"
Inner rim 1.13 wide x . 25 thick
Spokes (5) at .88" x .20" cross section
Hub 2.30 long x 1.82 O.D.
Hub Bore .75"
Weight 7.96 pounds
........................................
Starting with a chunk of 8" nominal welded steel pipe.
View attachment 108091
Three slices of pipe.
View attachment 108092
L to R, Outer rim, spokes, inner rim.
View attachment 108093
The bolted assembly with the epoxy and bolts visible.
The JB water weld has NOT been applied yet.
EDIT: Each spoke is machined for a snug fit into its loacation, including a snug fit into the matching groove in the hub. There is one 8-32 bolt radially thru the inner rim into the spoke. There is also a 10-32 bolt that goes thru the spoke radially into the hub.When these 10 screws were all tightened and secured with Loctite 680, the flywheel became a rigid unit. The outer rim was a slip fit onto the inner rim, and epoxy was was used to secure it in place (and possibly kill some vibration) and was also secured with setscrews radially outward from the inner rim into pockets in the outer rim. This method allowed the outer rim to be aligned with the hub to minimized radial and axial runout. The additional epozy and JB water weld fillets are mainly for cosmetic purposes, but I am sure they also will contribute to strength and vibration damping.
View attachment 108094
After filling, sanding, priming and painting, here is the Glamour photo
of the finished flywheel, using special lighting,
and the photo editor, for those extra special high-lites, LOL.
View attachment 108095
More to come, but not really fast.
Lloyd