Thorp Air Command - T18.net

Gentelmen:
I am relevantly new to the Thorp world & this is my first letter to the forum.
I was lucky enought to become famous by bending the gear legs about 6" back & sliding down the runway on the spinner @ the Murry,Ky. fish fry.
Repair work is taking place.
The gear legs have been annealed, then strightened,the cracks have been welded & fish plate welded. I realize the inner leg is supposed to slide inside the outer tube. I could see the inner leg thru the crack in the outer tube & no crack appeared.I have no way of knowing for sure if the inner leg became somewhat attached to the outer leg in the welding process, what movement at that point had to be miniscule.
I am now looking for a heat treater that can handel the length of the legs.
My gear legs are diff. than the plans show, there may have been difficulty in finding a heat treater in the first place.
Picture the "A" frame being split vertical & a tab at the top bolted together. The horziontal tube in the "A" cut in the center with an inner tube about 15" long to slide inside each half with two bolts in each side.
Now I have two seperate legs that doesn't require as large an oven.
Does anyone know of a heat treater that can handel parts of this size? Help Help
Thank you Mike

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Mike Fleming

It sounds like you may have the CSA gear ? Mike made it in 3 pieces to make it easier to ship. [:)] The fact that you can take it apart should make it considerably easier to find an oven to heat treat it in. [;)]

RB

The gear Mike has is a later mod of the standard gear so it would fit in an oven. There is a drawing of this mod. I was there and helped move the plane, it is the old style gear. As for the new CSA gear "don't even go there".

Find a spring shop that repairs heavy truck/tractor/trailer springs. Most will have a oven big enough. We have one here in Sacto, CA. I suspect many larger cities will have similar shops.

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Dave M
Sacramento
ex-T-18 owner

BTW, when going to such a shop, I tell them that the part is for an "off road vehicle".

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Dave M
Sacramento
ex-T-18 owner

I am in the process of cold straightening my bent gear and am just getting prepared if that does not go well. If I have to do some welding repairs on the gear and then need to get them re-heat treated what is the heat treatment specification/ process required? I thought I had read a post or a NL where someone had the process sent to them but I can't find that after searching the site. Bedsides the 180000 number is there more to know when specifying what I need when I go to the heat treater?

Hopefully I don't have to go that route but I am just getting ready if I do.

Dave

You want to specify a quench and temper heat treat process.

heat to 1600 F (cherry red)
Quench in oil
Hardness should be about 625 BHN

Temper at around 825 for 45 minutes
Water cool after
final hardness should be around 420 BHN

A good Spring Shop should be able to do this. I used to work in one.

DW

Dick, thank you for the info. In searching the news letters I found the attached heat treating receipt from 1979 in the NL 56. It differs a bit from your spec but I think I am learning that the heat treating process is a heat, quench and temper process to achieve 180000 psi tensile strength without leaving the 4130 in a martensite structure. I guess a good heat treater will be able to tailor their process to achieve that strength.

I live in the St.Louis, Missouri area and it looks like there are a few heat treaters to contact. I have not found any spring repair outfits around here yet. It looks like the fellow Mike Fleming who started this thread lives in this area, I have sent him a PM but no reply yet. Would any of you know another way to contact Mike. I would like to pick his brain on the heat treaters in this area.

thanks for the help

Dave