Comparing motor performance,

[Aaron]

As ausmicro.com is now selling a lot of stuff I m constantly being asked for a measure of how various items perform.

This is easy with some parts (bearings/shocks) but with things like motors it s more difficult.

I would like to devise a system for rating motors and measuring their performance that can be applied to all motors we sell.

At the moment here are my thoughts on the basics I d like to compare between motors.

[*] Weight

[*] Physical size/construction method (endbells/mounts/vents)

Measured Factors

[*] No Load RPM @ 4.8v

[*] No Load Current Drain @ 4.8v

Tested factors

On a test jig the motor would be operated to measure the following.
[*] Torque
[*] Power (rate of change of Torque)
[*] Rotational inertia on coasting.

I m proposing to build a test jig that will be built from an all alloy motor pod, and drive a modified axle/diff which has a known weight and size. By using a computer to measure the RPM of the weights and control the testing cycle we can simply bolt up each motor and get compareable output. And then obviously we can graph it, map it against peak current drain etc.

But before I re-invent the wheel (or the dyno in this case) has anyone come across a good (cheap!) reliable dyno design for 130 > 540 class motors?

A.

--
Site Owner Guy.

[micro_Amps]

‘Cheap’ is the magic word Aaron. If you want to go anywhere near a decent DC motor dyno you will need to throw in some reasonable dollars.
There are several commercial versions around, some measure under no-load (not that much use IMO) and others that go right up to full on PC based read-outs with variable loads, costing thousands.
I still have interest in this subject, but at the moment I am hamstrung with selling/moving/building a house, and will be for the next few months.
I did some research on DC motor dynos back in the ‘Bit’ days and even found a very good example of a home built dyno that an engineer friend built with all the correct calculations and computations.
I have a Tekin dyno here (540 size DC dyno) that does produce useful numbers running test motors at 5v and loading them up (with another 540 motor), but as with most of my hobby stuff at the moment, its boxed up ready to move. They are 10 years old now, but still a useful tool in comparison tuning 540s. I am sure some of the 1:10 racing guys will have dyno info to add to this topic, but I’d like to keep an eye on this topic just the same.
A standardised comparison of small dc motors is long overdue, and several forum sites have threads about motor power/torque/rpm under load/no load that are just plain incorrect.
I’d like to see this corrected and see Ausmicro develope a definitive list, (if one is indeed possible) rather than just the rhetoric that is already out there.

[Aaron]

From my estimation I can design and build a proper Dyno that will measure motor horsepower (or kw) accurately for about USD $200

Most of the existing systems are about measuring current load when driving a propellor (water of air) and so on and not that good for comparison between motors.

More to come!

A.

--
Site Owner Guy.

[betty.k]

does anyone know how accurate the tamiya mini 4wd dyno is? if it’s not surely it can be made more precise, right?
the good thing is there are 2 sets of rollers for the rear wheels, so the “free” wheels could be hooked up to a torque measuring device giving you speed and power info simultaneously. i realise it’s easier said than done but surely it’s feasable yeah:question::8ball:

[Aaron]

That would be the “chassis” dyno implementation….

You’d nee to find a way of determining the work required to spin up the system though – that’s where it gets all trick and people don’t want to sshare as there’s mega $$$ to be made 😉

A.

--
Site Owner Guy.

[merc-blue]

http://www.sci-spot.com/Mechanical/dyno.htm
check it out

[betty.k]

far out!!!! that’s awesome. ifit works as stated that is but it looks pretty good to me:8ball:

[merc-blue]

hey guys im considering building ones.. could i be supplyed 2 mini-z bearings from some 1s sares box if i built one?

PS. i would be more than willing to “loan” it to ausmicro for a month or 2

Edited by – merc-blue on 16 April 2005 10:33:25

[Aaron]

merc, I’ll be very interested in your preliminary results. The unit we’re looking at make is going to be far more detailed than that but it’s the exact same principles. Just expanded a little more

A.

--
Site Owner Guy.

[merc-blue]

yeha i origionly lookeed at this topic and though… hmm hall effect dyno ETC.. if ya build one tell me

[azza2000]

that dyno looks good. How do you mount up the motor to it?

[Author]

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