Hey Iggy - stepper motors ?

It has been a while since I played around making wheels for belt drives. We were fooling around with belt drives for small aircraft using VW, Subaru, and several two cylinder two-strokes.

Chuck modified the cutter to match the tooth profile of a Gates belt and we made a dozen or so wheels using a manual gear cutter.

In the end, we got a couple of engines running well, but the weight of even small auto engines was excessive. At least for what we were trying to do.

The one thing I can remember clearly about cutting belt drive wheels is

- don't back up!

I'm thinking something much smaller , like a 4mm tooth/notch profile .

This article might be of use

Terry, I only have tiny stepper motors, not NEMA 34 or 23.

i

Terry Coombs prodded the keyboard

Have you considered car wiper motors ?

See my build log :- You will need to register to see the pictures.

Having worked with stepper motors in space- and power-constrained devices, I am highly prejudiced against them. That doesn't mean they won't work -- it just means that I've had bad experiences. I much prefer a servo motor driven by a feedback loop (at least, when I get to design the controller).

Check with Herbach & Rademan

for motors. They may not have what you want, but they have lots of stuff in that sort of size.

For pulleys and belts and whatnot, check Stock Drive products. They aren't a surplus place, but they have fair to middlin' prices on fair to middlin' stuff, and they'll have the same thing next year. I've had good success tossing together mechanisms using their parts.

I have a couple sitting on the shelf , but they both have stripped worm gears that I can't repair . With the PWM controller I have here now there may be other options for those too . Thanks for the reminder !

Thanks , I'll check that supplier for motors . As far as gears and pulleys , I'm equipped to make those , from casting the blank in aluminum or brass to final machining . I have lots more time than money ... and a big pile of casting stock .

Thanks for the link. I did not realize making pulleys for cogged belt was so simple.

Dan

From $12.99 w/ f/s on eBay

How much torque do you need?

Cogs are cheap as dirt online.

David's link looks like a promising start.

Terry Coombs prodded the keyboard

Hi Terry, I get my wiper motors from the scrap yard for peanuts. On most of the ones that I've played with the worm is just pressed onto a splined shaft. A PWM controller works just fine with these motors since they are permag types. I've had mine upto 30 volts for rapid traverse, it gets barely warm from one end of the table to the other, (762mm).

Those HTD ones aren't bad, I used to know a guy that made the classical timing belt types on a Fellows gear shaper and they were more difficult to make by simple means IIRC, of course his speciality was machining gears and he had the kit. These days with pilot bore ones being quite cheap I would just buy them and alter them to suit, which I have done on a few occasions recently.

Do you heat treat the aluminium at all as my limited experience with as cast items is it is soft and gummy and not nice to machine. A mate that worked as a designer at a company the made a number of products with aluminium castings said they always heat treated them, not for strength reasons, but for machinability as the surface finish achieved was much better and some other benefits.

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Just had a thought, given the relative ease of fabrication and availability compared to gears, i. e. no special tooth cutters.

Many of us on the group have older change gear lathes and are missing some of the gears. Has anyone done a conversion to a cogged belt arrangement? If so how did it work out? What sort of a belt tensioning device did you use? Did you require multiple belts to cover all the pitches? What material did you use for the cog pulleys? Would delrin or nylon work?

My experience has been that extruded stock makes gummy castings . Material that was originally cast usually machines just fine . My usual practice is to dunk the casting in water as soon as it comes out of the mold , this both helps machineability and helps get residual molding sand off the piece . Letting a casting stand for a few days also helps , as I understand it aluminum gets some temper from just aging .

Sounds like you are doing a basic post cast heat treatment with that procedure. The castings I've had done were done commercially with a standard casting alloy, LM25?, and were soft and not nice to machine.

A wiper motor may work if you do not need accuracy and repeatability. The beauty of a stepper is you can control rate of feed ACCURATELY, and also control the actual distance the drive moves the feed.

It really all depends on what your smelting stock is. What alloy are you casting? If you start with 6061, you will get a machineable, weldable casting. If you start with 3000 series aluminum, you will get bubblegum.

6061 age hardens.

snipped-for-privacy@snyder.on.ca fired this volley in news: snipped-for-privacy@4ax.com:

And you can't with a servo? Really? Lloyd