Burman GB Gears - Rescuing the dogs?

[barry.krauter]

I got a request for a 3652-52 21T Third Gear. I looked over my GB parts and found that 3 of the 4 I have are unusable due to worn dogs.

It occurred to me that while we hear of camshafts being built up with weld, and shifter forks being similarly reclaimed, I have not heard of anyone
repairing the dogs with welding and subsequent regrinding.

Why not? I note that Drags has no supply of the 3652-52 and judging by my examples, these tend to wear rapidly - lots of people must need replacements.

I'm tempted to ask a specialist welder, but meantime does anyone have any thoughts?

[john.whiting]

Using preheat to moderate any excessive hardening,gear dogs can be built with weld and without expensive heat treatment to restore the parts.The earlier Burman boxes have 3 1/2 nickle steel gears,oil hardened,and easy to weld successfully.It depends on whether the GB used the same steel,or has case hardened gears.There is always a tendency to develop cracks where the weld meets the case,even if stainless is used as a filler.Its usually pretty easy to see if case hardened gears have been used.Regards John.

[Richard Kal]

Hi Barry,
Modak in Melbourne, Aust have a used gear for $145Aus.

Richard

[Eero.Korhonen]

Hi,
Here is link:
http://modakmotorcycles.com.au/?page_id=435
Br, Eero

[john.whiting]

Ripoffsville.Time to get out the welder.Incidentally,I get good used gears from the NOC for 5 to 10 quid plus post.Try the Matchless owners club.Regards John.

[barry.krauter]

Ripoffsville.Time to get out the welder.Incidentally,I get good used gears from the NOC for 5 to 10 quid plus post.Try the Matchless owners club.Regards John.

John, after building up the dogs with weld, what do you use to reshape them?

Regards

Barry

[john.whiting]

I use a 4" angle grinder with a thin disc.Takes a bit of skill,but as a method this is the most satisfactory way of profiling gears,breaking sharp edges,undercutting dogs,and numerous small jobs on hardened steel.Regards John.

[Peter.Greene]

I picked up an old workshop book that indicated that the dogs can be built up using "Stellite" or similar hard-facing welding rod, Stellite alloy is a range of cobalt-chromium alloys designed for wear resistance. It may also contain tungsten or molybdenum and a small but important amount of carbon.

[nevhunter]

That gear has been in demand for a long time now. Probably time to have some made. Nev

[john.whiting]

Burman were specialists and used their own ideas of tooth form and pitch.This means that standard hobs and cutters wont match Burman teeth.CNC single point machining could duplicate,but you would need to digitize form first.This means expensive time on a current machine,not some tinkerer used an old Sykes planer in his garden shed.Then there is the expense of small lot heat treatment,unless you are happy with 4140HT as it comes from the suppliers.Regards John.