Jeandr wrote:... Obviously you did the job too good, it is hard to notice anything had been done.

Jean

Thanks , that's what I was going for

willh wrote:Thanks Jean,

The last photos are of my frame after I did the work. There was no easy bearing swap with the AJS/Matchless/Norton neck with 1" neck diameter for the triple clamp shaft. The casting would have been hogged out to the point of being too weak to do it's job. I sleeved the neck and welded new cups for Timken"s. It's done now. It's strong and almost looks like it was made that way originally.

Will

I wonder how you kept the parts exactly in line when welding? Seems to me that this must have been very very difficult, and may have been an awful lot easier to make a completely new headstock to take modern front forks suitable for off road riding? If the bearing houses arent perfectly in line, then a tight spot in the steering may result, and I cant see any way to overcome this, without putting the frame into a jig, and fitting a new headstock. Hopefully it wont have a tight spot though, and there will be no need to deal with the problem.

Carbonfibre wrote:
I wonder how you kept the parts exactly in line when welding? Seems to me that this must have been very very difficult, and may have been an awful lot easier to make a completely new headstock to take modern front forks suitable for off road riding? If the bearing houses arent perfectly in line, then a tight spot in the steering may result, and I cant see any way to overcome this, without putting the frame into a jig, and fitting a new headstock. Hopefully it wont have a tight spot though, and there will be no need to deal with the problem.

I sleeved the neck with a very light press fit, while keeping in mind the brittle casting, and the cups were lightly pressed in and bottomed in the full length sleeve. The triple was installed, tightened, and checked for tightness. The cups were tacked and then triple was removed before MIG-ing the bottom. Cool down then top, cool down then bottom, etc. to get the thickness desired.

I was somewhat concerned about the neck casting properties and brass. If I were to go another route, IE cutting the neck off, I feel that the whole casting would have had to come off and tubing lengthened, etc. I seriously considered it but tried this first. Happy to report that there are no tight spots so it worked as hoped. If it had failed then the next step would have been a new neck farther down the road.

The machine time was free. I had to pay for the welding because I didn`t have the free time at work but wanted to have it done anyway.

I`m on a budget. I`d love to have a frame jig at home and a tig, lathe, milling machine, etc.... Doing what I can with what I have at my disposal...

Will

Thats fine then................I would have tended to TIG braze a job like that though, as there is far less chance of distortion. If the frame has a cast headstock, then its investment cast steel and pretty durable. It is worth bearing in mind if you are doing any welding in or around investment cast frame lugs etc, that it is possible to melt the braze joining the lug to the frame tube, and this can obviously have very serious consequences!

Carbonfibre wrote:.... that it is possible to melt the braze joining the lug to the frame tube, and this can obviously have very serious consequences!

I cleaned out the neck of all brass that could have made it to the welds. We took are time and kept the temps down.

There are areas of the frame that are dripping with brass. They didn't seem to bother with wiping the extra off at the factory.

Old Brit bike frames are hearth brazed, as this is the only real way for the brass to fully wick into most of the joint area. Some lugs are retained on the frame tubes by nails driven through pre drilled holes to keep them in position during the joining process. Any form of welding in or around a brazed lug joint can compromise the joint strength, and as such its always a good idea to TIG braze if this seems feasible.

Carbonfibre wrote:Old Brit bike frames are hearth brazed, as this is the only real way for the brass to fully wick into most of the joint area. Some lugs are retained on the frame tubes by nails driven through pre drilled holes to keep them in position during the joining process. Any form of welding in or around a brazed lug joint can compromise the joint strength, and as such its always a good idea to TIG braze if this seems feasible.

I have never TIG brazed but have Oxy-Acetylene brazed with good results, just never had to do it on a bike frame as all my frames with the exception of this one are welded.
I usually do all my own welding, MIG, TIG, oxy-acetylene. I had a change of employment that has had a negative effect on the amount of after hours shop time that I have available to me. A trusted shop did the job with full understanding of the dangers involved. Possible problems with welding the casting were considered and precautions taken to insure that they would not arise. I am very satisfied with the results.

Will

There are no problems with welding investment cast lugs, as these are steel and present little difficulty. Only issue is the heat of the welding process is a great deal more then that of the melt temperature of the material used to make the frame, and even though all seems perfectly ok it is possible the brazed joints will have been weakened by the welding carried out.

If you are sleeving something like an investment cast headstock, to take different bearings, then TIG brazing is the best process to use, as this puts the least amount of heat into the job, and greatly reduces the chances of any problems with the original brazed joints.

An example of what can happen when welding is carried out adjacent to lug brazed joints, was a BSA MX frame which had had welding carried out near to the front motor mount, and which unfortunately resulted in the brazed joint failing after landing from a big jump (there was a picture of this on the net several years ago, but not sure its its still to be found).

Carbonfibre wrote:....Only issue is the heat of the welding process is a great deal more then that of the melt temperature of the material used to make the frame, ....

willh wrote: We took are time and kept the temps down.

All is well, for the most part the welds are far from the brazed areas and were welded in small doses and allowed to cool down in between to avoid the problems you speak off.