3d printed gears? Resin molded gears?

[wingspan99]

Is it feasible to 3d print the main gears? Or maybe make from resin molds? Maybe make a silicone mold from a good gear and pour glass reinforced resin gears? Certainly the secondary tail drive gears that have less stress can be 3d printed, no? How about a zinc gear from a silicone mold? I'm trying to figure what to do if I strip a main gear on my fury and stratus. This ain't rocket science, there's got to be a way to make a serviceable gear.

[Heliguy3D]

Likely not. More feasible is to have someone machine one from Delrin

[wingspan99]

I tt a friend with a 3d printing business, and he said the PLA and ABS plastics used in 3d printing are too low in temp to withstand the harshness of heli main gear duty. But he said that a urethane casting may be strong enough and heat resistant enough. There is a wide spectrum of hardness and flex in urethane resins. Urethane is what bowling balls are made of, which may be a little too brittle, but just below that may give a hardness similar to nylon. If I get one of these main gears made I will test it on my Tempest and Stratus machines, and maybe someone else can test one too, in a hot climate, near sea level with a high power engine, on a hard 3D flight. I fly at 6100' and cant stress it nearly as much. I mainly need a recommendation for a urethane to make the first batch. I will probably make silicone molds that are flat on top, pour urethane to overfill the cavity and clamp a piece of glass over the top to get it flat while it cures so that it will run true. I am already thinking about the other heli's gears and how to cast them in urethane as well as a tiny spur gear for some of the servos I have stripped that have no gearsets available. A urethane gear could be even tougher than nylon.
The mold making process is pretty simple, you coat the part in silicone mold release agent, attatch it flat to a glass plate with a little hot glue, make a wall around it, and pour silicone mold formula over it, and when the silicone is cured the part comes out leaving a detailed impression. Then some urethane mold release is brushed in the mold and the urethane is poured in and a plate is clamped over the top to get it flat. If anyone has casting experience please chime right in here.

[wingspan99]

I found this link to a spec sheet for casting resins.
http://www.freemansupply.com/tables/...ing-resins.htm
The strength of these liquid tooling resins is 2x-3x higher than urethanes even, and the durometer hardness of 90D for some of them is much harder than the hardest urethanes, yet still not as hard as nylons which rate 110R-115R (Rockwell R).
With aluminum fillers I wonder if it will increase the lifespan of an epoxy main gear being driven by a steel pinion? Freeman 801 or Freeman 805 would be a first guess. The tensile strength is way up there at 7-8k psi.
Liquid tooling resins are designed to become a mold to inject something of slightly lower temperature into it (like liquid nylon) to make a part. Talk about strong epoxy, this aint no 5-minute "epoxy"! Maybe JB Weld is the closest thing I've seen.
-Tom