Most of the restoration work on my ST4 is now complete, except it really needs new tracks & sprockets. I did make a start on this but got sidetracked buying another ST4 off E-Bay - it was too cheap to ignore at 650 quid so I'm now the proud owner of 1962 ST4 330
This, as you can see, is in similar condition to the last one, except that the gearbox is ok, and, after a bit of tinkering and fitting a new exhaust valve, the engine is a runner too. The worst bits are the tracks - rubber is rotten, and most of the track guides are as well, so I have made a start on fabricating some new ones.
I have made a few jigs for cutting, drilling, folding and welding 3mm steel strip, but it is a bit of a task - the top of the guide is a complex compound curve and the only way to do this is to fold it over a suitable dolly made from 2 pieces of 20mm steel, clamp in place with a matching clamping piece made from a single piece of 20 mil then cold form the curves with a hammer - each guide needs about 100 blows so to do a full set that's 32,000 hammer blows! - i'll have arms like Popeye.
The good new is these are only costing about £1.25 in material, and I can get all 320 powder coated for about £100, so much cheaper than trying to buy new even if you can get them.
I've been experimenting with casting the sprockets as well - so far only in aluminium as its easier to work with, but results are promising - I've over estimated the shrinkage factor at 2%, so need to re-work the pattern to approx 1.5% before having a go in bronze
This, as you can see, is in similar condition to the last one, except that the gearbox is ok, and, after a bit of tinkering and fitting a new exhaust valve, the engine is a runner too. The worst bits are the tracks - rubber is rotten, and most of the track guides are as well, so I have made a start on fabricating some new ones.
I have made a few jigs for cutting, drilling, folding and welding 3mm steel strip, but it is a bit of a task - the top of the guide is a complex compound curve and the only way to do this is to fold it over a suitable dolly made from 2 pieces of 20mm steel, clamp in place with a matching clamping piece made from a single piece of 20 mil then cold form the curves with a hammer - each guide needs about 100 blows so to do a full set that's 32,000 hammer blows! - i'll have arms like Popeye.
The good new is these are only costing about £1.25 in material, and I can get all 320 powder coated for about £100, so much cheaper than trying to buy new even if you can get them.
I've been experimenting with casting the sprockets as well - so far only in aluminium as its easier to work with, but results are promising - I've over estimated the shrinkage factor at 2%, so need to re-work the pattern to approx 1.5% before having a go in bronze