Kyosho Ultima (Original/Vintage) - Center Gear Replacement?

[EEK2112 8]

Does anyone know where I can get a replacement "Center Gear" for a vintage Kyosho Ultima? I saw some 3d printed ones out there, but I'm not sure they will hold up...this is for a runner that I am rebuilding. I have been looking forever and no luck. Any help would be awesome!

 

Erick

[Champ85 609]

Part UM-1 is getting hard to find these days and expensive when they come up.  The 3D printed option is becoming a last resort if you want to get a car running again. As for how tough they would be, it depends on what plastic they are made of and how they were created. Anything created on a home 3D printer wouldn't be worth the plastic it is made from, IMO. The resolution is just not high enough.  But if it is the Shapeways Nylon 12 Versatile Plastic printed using the SLS (selective laser sintering) or the other Nylon 12 (MJF Plastic PA12) , then it will be pretty strong and wear resistant and worth a shot.  A few years ago I made a gear for the Kyosho Rocky using the SLS Versatile Plastic and it's been working fine, though I don't do much offroad with the car to stress the gear much (like jumps, etc.). But it's a good hard plastic that is very tough as you would expect for Nylon.

The hardest part to design a gear for 3D printing is the actual shape of the gear teeth.  Unless the designer has experience making gears for 3D printing and knows how to compensate for the shrinkage and other things that are involved in the specific type of plastic being used, the gear could be a poor fit resulting in a bad mesh to the other gears, risking damage to them.  It took me about 5 tries to get the proper tooth shape/size and gear diameter as correct as I could get it to match the original gear when I was doing it, but I'm a total amateur.  I mean, we are talking about making 0.3mm to 0.1mm modifications to tooth width and gear diameter here - really intricate stuff that could even be within the margin of error of the printing process itself.  But it is important to get it right for maximum gear life of both the 3D printed part and the gears it meshes with.  It would suck to buy a 3D printed gear that ends up destroying the gear next to it because the tooth shape is wrong.  I have no idea if "Vintage Gears" (seller on eBay) has made sure the gears are the correct profile or mesh properly.  Still, I would buy one to see how it fits if I were you.

[EEK2112 8]

Thanks, I was looking at a few on Shapeways (yes, the nylon 12), but if you factor in shipping and processing fees it might be better to either find another donor car, or just upgrade to the re-release gearbox/gears. It would be great if Kyosho supported the old vintage buggies, but I understand why they wouldn't at the same time. That being said, I was able to find another complete Ultima with radio for $110...should be delivered tomorrow...if the gears are destroyed I'll probably go the Shapeways route. Unless one pops up here or on EBay. One nice thing about the Tamiya kits, I am usually able to find replacement parts.

[RichieRich 685]

Yeah, your best bet might be buying some junked donor cars. The gears are generally pretty solid though they can get chewed up pretty bad if someone wasn't great at setting gear mesh. That center gear was used in about 15 versions of the Ultima/Optima gearbox so you'd think they'd be rather common.

[EEK2112 8]

I have been looking and haven't found the gear, I did find a second Ultima that has all the parts I need to complete my project. Luckily the center gear is perfect in this one. Seems like parts are getting harder to find for the vintage Kyosho kits...and when they do pop up on ebay, people are asking a fortune for them.