I have a FVP in the queue that will need something doing with the leg, and I was considering making a new one out of stainless As I have a spare lower housing and leg I thought I would take a look at it and see if a means of getting the old leg off could be thought through. I do think is is possibly the worst piece of engineering design ever. Why they didnt just make the joint a clamped one like the 102 is beyond me
Gentlemen your mission should you choose to accept it is to discuss a way of achieving this. This post will not self destruct however.
My initial thought as a (very) ex toolmaker is to mount the leg on a lathe and carefully machine out the leg from the inside lower, with a small boring bar, without damaging the threaded alloy housing. It is quite corroded so might come apart easily, when there is only 010" to 020" wall thickness left. Both metric and imperial helicoils are available, but the taps are very expensive.
Finding the thick walled tube to make a new leg will also be difficult.
Hold the tube in the vice & get the casting hot, very hot, 450 centigrade but no hotter,it gets soft, it helps if you've got an IR thermometer, then with a piece of wood between the exhaust & the drive shaft tube housing, try to unscrew with gentle to firm pressure, when it starts to turn undo it half a turn then a quarter back to loosen the aluminium oxide that's binding it.
Don't expect it to come right out without reheating & lots of forward & back movement, 450 C is around the temperature a matchstick will leave a black mark on the ally when used like a pen.
Make it idiot proof and someone will make a better idiot.
Good idea Charles. I have a decent blowtorch, but I suspect I will need something bigger than that. We will see. Any suggestions as to where stainless tube 1.125"x 12 gauge can be obtained?
I did find a company in Middlesex last year who could supply 1.125” by 0.120” stainless tube.
Unfortunately the price quoted was prohibitively expensive at £110.40 for a 700mm length. I opted for mild steel instead with the intention of having it chromium plated.
I tried the suggested method, but no joy. It is stuck solid.
Interestingly I measured the wall thickness which is approximately 080" Somewhat thinner than I expected, and a lot thinner than the legs on the 102s. So it seems to be 14 gauge tube.
If anyone knows of a supplier, or can get any do let me know.
I have already got my tube off and I had a look around for some stainless, I did find some 28.58mm (1 1/8")diameter and with a wall thickness of 2.64mm in lengths of 700mm.
For just over £20.
That's with the postage.
I will have to look at the thread on the drive tube, I think its an odd one.
You could try cutting up the inside of the tube with a hacksaw or saber saw to release the thred pressure. It could result in damaging the thread a bit though.
A mill might be easier to hold it for boring out but I would probably find a way of holding it in the lathe as it makes for easier boring.
We have a guy here that travels around in a van doing thread repairs, recoils, timeserts etc. if you had someone similar they are a good source of coils and inserts. My guy lends taps too so it avoids the cost of whole kits. Remember that some of the coil taps are just standard taps if you know the size and pitch so you or someone you know may have a tap.
Yes I have I bought it for a proposed long tail Seagull racing Century, I'm sure it was 1.125 but but can't remember the wall thickness, I think it was around 12 gauge, I'll find it & measure it tomorrow.
Make it idiot proof and someone will make a better idiot.
Cracked it I cut off the old leg, then very carefully cut a slot through the old leg threaded section. Then with a lot of care, mounted on a wooden block collapsed the threaded section inwards. The threads in the alloy are still usable.
It helped that the leg was soft, so perhaps mild steel and only 080" wall thickness.
Next job is to measure the thread pitch, polish up the casting and seek some stainless tube 1 hour in the garage before dinner well spent.
Good job! I'm glad it worked for you.
If you were not too worried about originality, couldn't you use stainless tube? We have a specialty stainless place here that sells or can get most sizes of tube and pipe with different wall thicknesses, usually imperial. I'm sure you would have the same. Saves chroming and you can polish it up.
I just noticed your going for stainless anyway. Our place sells a lot of handrail stuff and stainless industrial pipe fittings and the like, might help in your search.
As I have a spare lower housing and leg I thought I would take a look at it and see if a means of getting the old leg off could be thought through. I do think is is possibly the worst piece of engineering design ever. Why they didnt just make the joint a clamped one like the 102 is beyond me 
Gentlemen your mission should you choose to accept it is to discuss a way of achieving this. This post will not self destruct however. 
I cut off the old leg, then very carefully cut a slot through the old leg threaded section. Then with a lot of care, mounted on a wooden block collapsed the threaded section inwards. The threads in the alloy are still usable. 