Polyurethane support rails ???

[Eurisko]

To make a long story short...

I'm designing a 48x36 router, stainless steel shafts, linear bearings, etc.

After pricing aluminum shaft supports, I'm toying with the idea of creating a silicone mold and using polyurethane resin to create the rails at a much lower cost.

I think it will be strong enough. It will be bolted to the shafts and to a steel frame. It will there simply to keep the shafts from deflecting.

Has anyone tried this stuff for structural components of a router?

If it fails, I can always reuse the silicone mold and try my hand at lost wax casting with aluminum

[Zumba]

Way too soft and squishy. Plus it shrinks as it dries.

[svenakela]

Everything is about how much load you will put on the rails, but yes it will work for lighter loads. P-u flex a lot more than alu. If I were you I would go for full length support.

Regards,
Sven

[svenakela]

Way too soft and squishy. Plus it shrinks as it dries.

It will shrink homogeneous.

[walter]

Epoxy Granite might work.

[Eurisko]

Thanks for the input.

I've seen PU shaft end supports on eBay, thought it might just work for a full length shaft support.

Anyway, I have about 3 gallons of this stuff, 1 part resin, 1 part hardener. Dries hard in 2 1/2 minutes, full cure in 24 hours. Machines well.

Shrinkage seems to be about .001 per inch.

If it doesn't work for the rails, I'll have to find another use for it.

[svenakela]

Go man, just go!
(And for you guys not watching movies, that's from Dum Dumber. )

[Eurisko]

Thanks svenakela,
Just needed a little motivation...

[ahren]

I also bet it will work -- if they are full length supports, they'll only be loaded in compression, and that loading will be spread over a huge surface area, so you shouldn't see much stress (and hence not much movement). Even for crappy plastic, you'll have an ultimate stress of ~1-4 ksi (as opposed to 45 ksi for aluminum). At a conservative 1 ksi, assuming your support is 1/2" wide, and your load is spread over 6" (for 3 square inches), you'd have to see 3000 lbs before failure, and probably 200 lbs before significant mushing of the material.