Yes I try all methods, and found nothing that bonds to nylon, including various thermal welding techniques which works, but not as strong. Even try plasticizer additives and light abrasion. Also yes try acrylic mixture but snaps easy, but does bond somewhat and will still use to form the fake teeth, but still failed at not snapping with stress. So figure give this stuff call "Tech bond" with the acrylic mixture to form the fake teeth a try and it works wonders, it actually bonded to point I snap a different piece, trying to get it apart, it take 24 hours to cure and you do have to sand the surface same as other methods. It is expensive but looks to be a good permanent fix.

To fix the gear, To get the color use acrylic paint to the plastic mixture when forming  then add to crack and let dry when it dry and you use you router, or mini drill to sand to the same shape of the teeth and made surface smooth, this take time and skill. resnap the piece, and to make surface rough, then use the special primer with the Tech Bond, use for Nylon, Polymers, Polyethylene, Polypropylene, UHMW, etc. Then use SI blue, or black, which the black is thicker and take longer to cure 24 hours, then sand if you can see the glue, repaint and gear will look like it brandnew and you won't be able to crack it I try already, so have no doubt this will hold up, unless gear get even smaller. 

BTW Make sure you get the spacing dead on, when making teeth, most will be around two teeth, sometime different, depends on how big the gap is, if gear is oval you need to do spit method, so gear is round, like all other methods otherwise you will get click and wow and flutter problems, mainly make sure when you turn gear it doesn't hit forward gear wall surface.

very difficult to bond delrin and nylon, etc etc -

so THANKS for this discovery-

i have used ' marine GOOP ' --

it seems to adhere well - but i dont really trust it

Plumbers pvc pipe glue works

Gear after being repair. Had to made fake teeth, due to gap and shape it almost dead on and after sanding and painting it. Yes this take time and a good drill, used a high RPM dental micro drill due to less vibration in the motor to shape and sand. 

Wow nice work

It is good to see the competition between Dottor Walkman and retrodos in striving for the perfect repaired centre gear is leading to better techniques of repair.

All this means is win win for the rest of us

Not even trying to start a competition as his work is nothing less then stunning, plus he in a different part of the world, so make sense for people around his area to go to him. Was always looking for better ways to fix these, as they are a huge issue for alot of us. And epoxy and superglue wasn't cutting it and no longer be used around here.  

Being the nearest to where in the world you are, this is not strictly true. People will always seek out those that have the skill to repair to a level that they are happy with where ever they may be.

However in terms of you not seeing it as a competition, the rest of us view it as a case of one member coming up with an idea as to how to fix something and then another doing it slightly differently and or perhaps even better. This is good competition and a win all within the community. It is a colaborative work method since lost to many due to greedy corporations wanting to protect processes to maximise profits.

I really admire the work of Retrodos and Plop.
They are also a source of inspiration for me to improve myself.
They have a great passion.
Continue in this way, also thanks to you the Walkmans are still living.

After adding a little SI and little more sanding to get it smooth and painting one last time looks like a brandnew center gear, install this one in WM-D3 transport.

utterly stunning work. Mine is a mess compared to work like this.

I got away with ca glue and polystyrene cement- so far my DC2 is holding up.

Here the walkman that the gear goes to and after all repairs as had to clean battery acid, replaced flex cable under battery plastic area and switch plus found some bad 220uf 4v capacitors that needed to be replaced.

Thanks 

How about a large full size macro photo of the gear, we don't want to think you're hiding something!

Look at top photo it alot closer, but is as far as I could go, it not a macro lens

You see toward the top that where the crack was, this was before I did the second sand, so you can see I actually fix the gear and not used a uncracked one, if you look close you will see the little spot towards the top on the left side by the teeth before I fill it in and resanded it. Yes good at plastic repair because I fix alot of antique radios where pieces of bakelite was missing making look like theirs was never a crack. Just never bother to fix nylon gears before.

I do one better I do a video of the repair process on the next gear I do, as not trying to sell the gear, so don't mine teaching other how to do the repair, just trying to sell better quailty walkmans instead of the AS-IS not tested junk for same price as restored one I see on eBay all the time, as tried of that already, plus for my own DD series collection.

And like I said before not in competition between Dottor Walkman, as he does fine work to. If anything motivated me to find a better fix, instead of the old CA glue and epoxy, to offer customers a better solution and dd series I sell I won't have to worry about potential issues down the line. 

Nylon 66 plastic may be welded with phenol or carbolic acid.  You need to locate some that is concentrated and wet both surfaces, wait about 5 minutes and press together and clamp for about an hour.  That is what Remington used on their nylon gunstocks.    I located some at an old time pharmacy.  It is used in very dilute mixtures for throat sprays.