help with ring gear ford 8n

[Hemmjo]

7/800 are 1000 is not going to affect the teeth.

You keep believing that!

 

[Non-farmer]

A post earlier in this thread suggested using Loctite 640 sleeve and bearing retainer.
How in the world could one do that?
It takes 600 degreesF just to slip over and on.
I doubt ANY glue could survive that.

I've got some stuff that's good to 2000F.

Thing is, you'd need a new mortgage to buy enough to do a ring gear.

 

[Dave G9N]

A post earlier in this thread suggested using Loctite 640 sleeve and bearing retainer.
How in the world could one do that?
It takes 600 degreesF just to slip over and on.
I doubt ANY glue could survive that.

I had asked about the wicking grade, Loctite 290. Chetswen suggested 640. My idea was that 290 would wick into the gaps and provide enough grab to keep the ring gear from slipping. The problem there was that the gap is already full of oil. Loctite 640 is stronger, but I don't think it would wick into a fairly tight space, and as you pointed out, neither of them will take the heat for a shrink fit, so wicking after assembly while it is still clean could work, but the gear starts to slip long after it gets contaminated and we start looking for a solution.

I checked back after finally getting around to welding the gear today. In retrospect, I should have bought Ultradog the beer. I live near Minneapolis and it would have been well worth the price. As I have been advised, even a rank amateur welder can do this job. I have a flux core wire welder that even I can sorta use.

There has been some discussion of shrink fitting, temperatures and botched assembly. There was some discussion of reason that the temperature should not exceed 450 or 600 F, depending on the source. Also something about thermal expansion. I have some experience with heat treatment, if not as much with carbon and low alloy steels as aluminum and stainless steel. My gear steel experience is sufficient to know that there is a lot more that I would have to learn to claim to be an expert.

The reason to avoid overheating the gear is that the strength and hardness is reduced by heating. According to the 1963 SAE handbook. starter and ring gears are generally hardened to Rockwell C 45 to 52, which is approximately Brinell 421 to 512. Some additional reading indicated that light duty gears can be made of medium carbon steel. Heavier duty steels can be high strength alloys like 4340 and 4140 and a laundry list of less familiar alloys. I found a tempering graph that illustrates what happens to the strength and hardness over a wide range of tempering temperatures. I would expect the old tractors to have ring gears made of the less expensive and more forgiving medium carbon steel. The high end steels can have some more complex problems such as temper embrittlement, which is nothing but trouble when heating between 400 and 700 F, so I doubt Ford would choose an alloy that required strict temperature control. Without knowing the exact alloy and heat treatment, All you can say for sure is that there is a trend than can cause problems when you overheat a part. Here is a chart for tempering medium carbon steel:

Thermal expansion is nowhere near as complicated. All carbon and low alloy steels expand close to 6 millionths of an inch per inch per degree Fahrenheit. When you heat a 12" steel ring 100 degrees, it will expand 6 x 12 x 100 / 1,000,000,000 or about .007 inch. If you are looking at a shrink fit, the difference in temperature between the two parts gives you the differential expansion. If the flywheel temperature is 80° and the ring gear is heated to 450°, the temperature difference is 370 and the expansion is 0.0025"more than the flywheel. Cooling the flywheel is the safe way to increase the temperature difference, but isn't as easy as heating the ring.