Casting pulleys in resin?

[bigegg]

I'm wanting to make up a few four-step vee pulleys - between the holbrook, two drill presses, and a belt grinder I need 7, i think.

My aluminium casting gear is still in storage, so i'm thinking of taking a mould from one of the pulleys i have, and casting them in polyester resin (with some fiberglass choppings for reinforcing maybe?)

Has anyone had any experience of making or using pulleys in this way?
2800 rpm max (step-down, not up), driven by a 1hp motor, so no massive strength required.

 

[Member 32799]

Waste of time ,very difficult to find aresin with little flex ( too hardwill crack) And stiffness and Abresive resistant ,Cheap , in the end It cracks anyways At stress points ,

use baltic birch Plywood , lasts longer

 

[bigegg]

Waste of time , use plywood baltic birch

I don't have a working lathe - until i make some pulleys.

 

[Member 32799]

Matthias wandel Youtube , style ! A drill a motor woodblocks and chissel

 

[gaz1]

forget baltic birch its expensive for us just buy the pulleys that you need bigegg

 

[bigegg]

forget baltic birch its expensive for us just buy the pulleys that you need bigegg

I have a shed full of baltic birch!

 

[More Amps]

I have a shed full of baltic birch!

Sell some....and buy a pulley!

 

[bigegg]

Sell some....and buy a pulley!

7!!! pulleys.

Plus - its as much the "making" as the "having"

 

[More Amps]

7!!! pulleys.

Plus - its as much the "making" as the "having"

Don't worry - you're among friends, and we all understand the overwhelming and illogical urges that occur from time to time.

 

[DAPPH]

I'm wanting to make up a few four-step vee pulleys - between the holbrook, two drill presses, and a belt grinder I need 7, i think.

My aluminium casting gear is still in storage, so i'm thinking of taking a mould from one of the pulleys i have, and casting them in polyester resin (with some fiberglass choppings for reinforcing maybe?)

Has anyone had any experience of making or using pulleys in this way?
2800 rpm max (step-down, not up), driven by a 1hp motor, so no massive strength required.

My ancient Sphere lathe has all the belt driven pullies made from Bakelite plastic so it should work .
Can't you get them 3D drawn and 3D printed .......it sounds like a good project for someone . Splitting them from north to south to make it much easier to print , glue & screw the halves together , even to using cable ties on the unused Vee's to hold it secure

 

[frank horton]

big egg,
it'll take a while but have u got a router table.....?
cut out the circles then shape 1/2 the V on the router able...router bit with a bearing...
provided u mount on a fixed center axis they will be round enough for the pattern...
too much work for 7 whole pullies...all depents on time....
or make enough for the lathe then spin the others up....easy...
then glue n screw it all together.....it'll at least get u going....

 

[Dcal]

You can make great pullies out of plastic.
A lot of the crane manufacturers have moved over to it from steel or cast.
PE is a good place to start looking.
You can use the same methods as you would for wood and there is a better chance of it holding together at 2800 revs.

I agree with you, making it is all part of the fun

 

[awemawson]

Make the pair for the lathe, then you can use the lathe to make the rest, and better ones for the lathe if the resin proves not to last

 

[Agroshield]

You can make great pullies out of plastic. A lot of the crane manufacturers have moved over to it from steel or cast.

Yes, but the pulleys used on cranes are idler pulleys or redirect pulleys not driving pulleys.

I think these are used for weight saving as much as anything. I suspect they are nylon 66 or delrin (some kind of 'hard' plastic anyway) as PE might be too soft.

I worry a little about using a very slippery material in an application where you are trying to transmit drive. The whole point of a belt drive is that there is sufficient friction between belt and pulley to transmit the power. I know the wedging action of the belt contributes a lot to this but it is something to bear in mind.

 

[bigegg]

Sounds like i'm pushing boundaries.

I'll make up a rubber mould over the next couple of days and give it a go.
( I'll need one to make wax masters for aluminium casting anyway).

Unfortunately, my lathe needs more than just a couple of pulleys.
It needs a complete drive train, and a cabinet to fit the drive train in. And space in the shed to fit the cabinet.

 

[hotponyshoes]

I would not use fibreglass strands to reinforce it, I can see the resin wearing down and exposing sharp ends which will destroy the belt. Got to be better fillers to use? A decent epoxy would probably be strong enough for that with out anything else anyway.
You may need to make allowance for shrinkage when making the molds if you need them precision

 

[bigegg]

I would not use fibreglass strands to reinforce it, I can see the resin wearing down and exposing sharp ends which will destroy the belt. Got to be better fillers to use? A decent epoxy would probably be strong enough for that with out anything else anyway.
You may need to make allowance for shrinkage when making the molds if you need them precision

No precision neccessary - at 1/8 per foot, even a 6inch pulley will only lose 1/16" of an inch across the diameter. And since the opposite pulley will lose a similar %, it should balance out?

Good point about the fiberglass - i'll see how it goes, and if i can be bothered, i'll chop up some spun nylon thread to mix in with it.

I don't want to buy any more resin (especially expensive epoxy!) - i've got 30 or 40 liters of polyester resin that i need to get used up in next couple of months.

 

[Kram]

Make up a pair of crude pulleys to get lathe working then cut them out of alumium bar, which you can cast.
I turned each individually and shrink fit onto a hub, that way good access on both sides of the V and minimum material wasted.

 

[bigegg]

Update.
I had a reply from a USA supplier of resins.

They recommended me to use a "urethane resin", rather than epoxy (which would not be abrasion resistant enough), or polyester (too brittle/hard)

So i've ordered a kg pack from easycomposites