Making transmission gears

[jedi-]

I thought I would post this just for interests sake, kinda off topic as these aren't Max gears but are basically similar. They are out of a racing Triumph and I just wanted to show the procedure in making them in detail as to give some insight as to what is involved and what to be aware of if the transmission is apart and why gears may slip etc.. We'll undercut the dog teeth which I'll show in detail as we make them.
The job is in progress, so I'll take pictures and update as we go.
So far I have machined the gear blanks ( 3 of each) which are shown in the picture. In the background are the gears we are going to replicate made by us last year I think and the gear shaft to be made also. To the right is a piece of billet steel which these were machined out of. There are several processes to go through and I'll show each step. So, so far we have the gear blanks with material left in critical areas which will be ground after heat treatment and the next steps will be the gear-cutting and machining the spline teeth.
I've never had my Max transmission apart but if I did I'd probably give it a ratio transplant.
More later as we machine them....

 

[KJShover]

That kicks much ass. Grat work!:clapping:

Hmm gets me thinking, about a 6 speed gearbox for the Vmax :eusa_dance:

 

[Thevmaxrider]

Would there be room for a 6th gear would be the question. I would be happy with a bit taller gearing in 5th (more like an overdrive). Machining your own gears opens up a world of possibilities.

 

[one2dmax]

We already have an overdrive 5th available. Cheaper then custom gears 9 out of 10 times.

Sean

 

[shawn kloker]

Don't forget,not everyone is looking for a castrated overdrive.I want one that is lower or a whole closer ratio tranny.

 

[jedi-]

A couple of pics showing typical dog wear on a "dog box" ie. non synchromesh evo 6 rally car as an example as to the rounding of the edge of the dog tooth. Although these are undercut anyway, the amount of wear they have sustained will make it not hold in gear. The situation is worse in typical motorcycle gears whereby the dogs are straight to begin (on many bikes) with and minimal wear could make it jump.
Leaving aside possible reasons as to why the damage could be occurring other than wear & tear(damaged shift cam etc) obviously the situation has to be fixed.

I never recommend welding the damaged teeth and then having them re-machined, reason is that the heat from the weld can and often does affect the case hardening of the gear. Not much heat is required to anneal slightly the hardness which means the gear teeth can become soft and will wear, those worn shavings will pass into the oil, might last for ages but who wants to pull the motor apart again?
Even reclaiming the edge without building up with weld can cause problems because the case hardness is only a skin and the core material is somewhat softer below that. So if the milling cutter has gone through the skin in order to reclaim the dog face then all that's going to happen is the dog will be rounded again in a short time because it is soft and it will have to come apart again.
In either of these two cases it could be possible to re-harden the gear but that can also be a problem. Who knows EXACTLY what the parent material was used and other than a destructive test to find out the heat treatment will be an educated guess on the assumption that is a typical case hardening material. Particularly if the dog was welded with a HT type rod, hows that now going to tolerate being heat treated, case hardened rather than a typical process for high tensile. Material often grows in heat treatment so the parts may no longer fit like previously and require further work. Also experience has shown that putting heat treatment on top of previous heat treatment could make the components brittle and therefore break.
Those pictures of the evo 6 gears are typical of what the rally cars experience on a regular basis. The gearboxes are thrashed and the gears are thrown away when they are worn. They won't risk a failure during an event.

Better solutions for the motorcycle guys are to either buy new gears or have them made. New oem parts are dirt cheap and although some material is removed from the dog teeth when machining them for the undercut, it shouldn't be enough to go through the hardening particularly as most of the material is taken from the bottom of the tooth and minimal at the top where it's doing most of the work.
New gears of course are hardened after machining the teeth and therefore have a uniform case hardness and desirable gear ratios can be obtained. They are expensive to manufacture because of the quantities involved.
The picture of motorcycle gear clearly shows the undercut on the dog when we made it.
More pics to follow ...