12v Motor Torque Measurements

[allockse]

Hello all,

This may sound like an odd request, but I am making a large mixer for my physics classroom using primarily mineral oil, and I was under the impression that an RC motor with a boat prop on it would be the most cost effective approach for the volume I have in mind (4-6 Gal)

I have been looking around at 12v motors, and I have found a few that seem reasonably priced. However I wanted to compare these motos to those used in RC boating, to make sure the motos I'm looking at have a high enough stall torque to get a good sized vortex going in the oil.

Also, for this application I was thinking that a 3 or 4 prop motor would provide more thrust and better mixing than the standard 2-prop designs. Please let me know if I am way off base.

The two motos I was looking at were from Anaheim Automation:

BDR-28-33: 12v
20,000RPM
484 g/cm Stall Torque

BDS-36-50: 12v
10,000RPM
1395 g/cm Stall Torque

If these are not high enough specs for this application, I would love if you guys could redirect me to some better ones. The motor needs to be 12v, and an amp draw less than 20 would be nice.

The school board has really locked in my bugdet as far as supplies for non-typical projects like this, so this will be out of my own pocket.

Thanks again.

[patmat2350]

How about a paint mixer from Sears and a cheap electric drill?

[allockse]

Thanks for the quick reply!

Thought of something similar, but that would mean I'd need to find an alternate container. Using the drill method, I'd have to cut out the bottom and seal it with silicon or caulk (I am terrible at this). The aquarium is my wife's, and I had to beg her to use it in the first place.

I could have it stirred from the top, but I can't have the top obstructed where all the measurements will be taken. Plus, highschoolers and power drills in the same room are never a great combo.

I can think of several ways to do this with a higher budget, but we all know how well teachers get paid don't we. :rolleyes:

I think using a drop-in motor like this will save me the most time and money.

So, is 20 oz-in torque too low?

[green-boat]

Why not a magnetic mixer, no holes or sealing needed.

[Shaun Hendricks]

Try a car fan.

Most will run submerged and run on 12V DC. A small replacement fan from any auto parts store (maybe 6-8" in diameter, cut down if need be), will churn your aquarium full of oil into a serious vortex in seconds.

I don't think anyone here could guarantee a vortex in mineral oil from a boat prop. That would probably take some imperical time and effort you may not want to invest.

[allockse]

Why not a magnetic mixer, no holes or sealing needed.

Yeah, that was my first idea. Was working great until I filled the container up all the way. I used my largest stir bar (3") and a 120mm PC fan. The magnetic stirrers here are much smaller quantity, and I'm sure the chemistry dept. wouldn't want to break any of theirs because of the size of this thing.

I haven't ruled out the stir-bar idea completely. I get a LOT of drag on the small fan motor, since it's not very powerful.

I still have my doubts though, I think once you hit upwards of 5L or so, magnetic mixing stops being as effective.

[allockse]

Try a car fan.

Most will run submerged and run on 12V DC. A small replacement fan from any auto parts store (maybe 6-8" in diameter, cut down if need be), will churn your aquarium full of oil into a serious vortex in seconds.

I don't think anyone here could guarantee a vortex in mineral oil from a boat prop. That would probably take some imperical time and effort you may not want to invest.

Good plan, that could do it. Again, I appreciate the help on this out of the ordinary request.