Cast pulleys and "extrusions"

[sonicwonder2000]

Hello to the forum!

I recently caught the CNC bug and have been spending WAY too much time on the zone . My last project was building an Al melting furnace, but I have yet to put it to any good use ...

I have been considering building a metal, belt-driven table, but the prices for extruded aluminum and pulleys are prohibitively ridiculous ... enter plan 2.

Build a cheap, small CNC. Use it to cut out some XL pulley patterns. Cast the pattern. The only snafu is I don't have any machining capabilities (lathe or mill). I am, however, casting in petrobod ...

Has anyone cast their own pulleys or large aluminum "extrusions" (c-channel)?
Will the finish be good enough not to tear up the belts?

Thanks for any input!

[diecutter]

Check out www.mscdirect.com. They sell aluminum extrusions with various tooth configurations to fit standard toothed belts. Simply slice off a piece and you have a toothed pulley.
You might also want to check into the pulleys on junk overhead cam engines, notibly Subaru. They have twin overhead cams and therefore a couple high quality toothed pulleys on each engine. You might be able to find low cost pulleys there.

[neilw20]

Have you considered chain. It is low cost, no limit on length, and sprckets are cheap.

[sonicwonder2000]

Thanks for the suggestions but I am really interested in knowing if home casting technology is capable of creating a useable XL belt pulley ...

diecutter: I searched mscdirect for about 30 minutes but could not find the extrusions you speak of? The Subaru tip is great, but I am working off the Solsylva plans which specify the pulley and belt sizes, so I'd rather not have to swim through the mechanicals of the engine to find the appropriate pulleys.

Neilw20: I have considered chain, but the backlash is considerable. I suppose one could minimize that with tensioned multi-sprockets, but this adds a level of complexity to the design.

Has anyone created gears from castings that have been used without finish machining?

[307startup]

Originally Posted by sonicwonder2000 Thanks for the suggestions but I am really interested in knowing if home casting technology is capable of creating a useable XL belt pulley ... diecutter: I searched mscdirect for about 30 minutes but could not find the extrusions you speak of? The Subaru tip is great, but I am working off the Solsylva plans which specify the pulley and belt sizes, so I'd rather not have to swim through the mechanicals of the engine to find the appropriate pulleys. Neilw20: I have considered chain, but the backlash is considerable. I suppose one could minimize that with tensioned multi-sprockets, but this adds a level of complexity to the design. Has anyone created gears from castings that have been used without finish machining?

I have done a fair amount of "accurate" castings using my home foundry. About the only way you'd have a useable casting that is ready to be used sans machining would be some sort of investment casting and your shrinkage tolerances have to be right on. Even a lot of aerospace application investment castings have to have some machining in order to function properly.

[Kipper]

Originally Posted by sonicwonder2000 diecutter: I searched mscdirect for about 30 minutes but could not find the extrusions you speak of?

I found it for you Aluminium Pulley Bar Stock It's already been mentioned that an investment method is the best and I concur with that...No possibility to include any draft angle negates the "no machining" method. And with the price of buying the ready made extrusion... I just wouldn't try

[sonicwonder2000]

Originally Posted by Kipper I found it for you Aluminium Pulley Bar Stock It's already been mentioned that an investment method is the best and I concur with that...No possibility to include any draft angle negates the "no machining" method. And with the price of buying the ready made extrusion... I just wouldn't try

Thanks for the link, my brain must be failing me in my old age

I guess investment casting is the way to go ... Do you think .01" tolerance on the pulley will be sufficient to have it function properly? I'm not sure I'll be able to get any better than that with an el cheapo cnc setup ...

[Kipper]

Originally Posted by sonicwonder2000 Thanks for the link, my brain must be failing me in my old age I guess investment casting is the way to go ... Do you think .01" tolerance on the pulley will be sufficient to have it function properly? I'm not sure I'll be able to get any better than that with an el cheapo cnc setup ...

Now bear in mind I'm widely regarded as a tight sod But personally I wouldn't consider casting them due to time constraints...But if I had the inclination I would make a mould from an existing pulley and use that. Having said that the pulley bar is very cheap which suits a Yorkshireman like me just fine As far as .01 tolerance goes I could imagine the belt being eaten slowly All the best matey