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Old 12-15-2016, 12:25 PM   #1
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Default Testing - What's better? Lets do some science, and share the results.

Hello Everyone,

Data is good. There's remarkably little ~real~ data for r/c out there. The last good data I remember seeing was 1990's RC Car Action publishing actaul power numbers, resistance numbers, and other data for batteries, motors, esc's, and connectors.

Lets do that again. Lets share how to get GOOD data. I'm going to post my testing methods. I'm going to share my data. None of us are making money, or need sponsors, so we can ~do the job right~.

Here's what I propose we test:

Bearings - Brands
Bearings - Treatments
Wire - Resistance
Motors - Ir
Motors - Power
Motors - kV
Connectors - new resistance
Connectors - resistance after 100 cycles
Connectors - resistance after 1000 cycles
Gear lube - running friction
Gear materials - "standard spur" versus materials and brands of pinion, at standard sizes.

To start? In the coming week, I'm going to do wire and connectors. If I get my bench power supply done, I can do Ir and KV on a few motors.

In the next post, I will present my testing methods for those three things.

FAQ:

1. How do I add my data?
Post your method, and your data. I'll move it up in to the aproprate post.

2. Can you test something for me?
Yes. PM me, and we can work it out. Most of what we're testing is going to be stupidly cheap to ship.

3. I think you're wrong!
We are posting how we're doing the testing, repeat the test, and report your results. With research, and science, it's NEVER ~done~. More data is better.

4. I want X tested!
Make a post, we'll discuss a testing method. Once we have agreed upon that testing method, order one, and we'll test it.
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Old 12-15-2016, 12:29 PM   #2
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Copper wire resistance is in almost every wire gauge chart, freely available on the interwebz.

https://en.wikipedia.org/wiki/American_wire_gauge
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Old 12-15-2016, 12:30 PM   #3
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Testing Bearings:

My thought is to get a knuckle from a TC4 or similar. And an Axle. Mount the bearings in the knuckle, and mount a 500g aluminum disk to the axle. Spin the arrangement up to 2000rpm, using compressed air. Take video as it spins down to we can track rpm versus time.

Using a standard 500g aluminum disk, means we'll have consistent aerodynamic qualities. And 500g gives us enough weight to have "a lot of time" to measure the spindown. I'll need to make a technical drawing, and make up a few to distribute. :-) I, do not, want to be the only person testing.

We'll need to decide on a "standard" bearing for testing lubes. My first thought on that is a bocca bearing with the shields removed. Any arguments there?

Last edited by Nerobro; 12-15-2016 at 12:32 PM. Reason: BOLD.
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Old 12-15-2016, 12:32 PM   #4
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Quote:
Originally Posted by howardcano View Post
Copper wire resistance is in almost every wire gauge chart, freely available on the interwebz.
There is. But that's just a lookup chart, and has no confirmation. Which.. we should do. And there are some potential weird stuff to run into. Like limp noodle wire, with high strand count, ends up being higher resitance. And also putting brands to specific data is a good idea.

if it ends up being to redundant, we just won't keep doing the testing. :-)
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Old 12-15-2016, 12:35 PM   #5
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You're going to be miffed when Olive Oil wins the bearing treatment testing.
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Old 12-15-2016, 12:43 PM   #6
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Gear / Drivetrain testing

For testing gear lube, I think I need some help. Getting "unloaded" resistance is easy. But what we need is "some sort of load".

How about a pan car pod, with our 500g aluminum wheel on it. For a load to pull against, we can use magnets held near the aluminum wheel. Or a fan, but I think it might be harder to standardize the fan. Doing "standard" testing with the magnets would be as simple as wrapping a string around the aluminum wheel and timing how long it takes for a weight to reach the ground.

Calibrating a motor... might be tougher. But we may not need to calibrate a motor. Just get a calibration number before each run. Would hooking a "standard" motor up to a volt and current limited PSU do the same job? I'm not sure. It might be enough to be consistent run to run so we can do a comparison between lubes, and gear types.

We need to decide on the "standard" gears. Suggestions? What are the most common brands of spurs and pinions?
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Old 12-15-2016, 12:44 PM   #7
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Quote:
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You're going to be miffed when Olive Oil wins the bearing treatment testing.
I have no horse in the game. I just want to know what's best, and what's worth the effort. :-)
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Old 12-15-2016, 12:46 PM   #8
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Originally Posted by Nerobro View Post
There is. But that's just a lookup chart, and has no confirmation. Which.. we should do. And there are some potential weird stuff to run into. Like limp noodle wire, with high strand count, ends up being higher resitance.
The total cross-sectional area of the copper doesn't change with strand count.

The accepted data is more than a century old, so by now it's pretty accurate. But it's always possible that some brands don't meet the specs in an attempt to make more money!
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Old 12-15-2016, 12:48 PM   #9
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But it's always possible that some brands don't meet the specs in an attempt to make more money!
And that's why it's worth testing.
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Old 12-15-2016, 12:49 PM   #10
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love it! Can't wait for some information.

Quote:
You're going to be miffed when Olive Oil wins the bearing treatment testing.
--I had a buddy who swore by Crisco oil on his mountain bike chain. I never tried it, but hey whatever floats your boat!
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Old 12-15-2016, 01:28 PM   #11
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Originally Posted by eR1c View Post
love it! Can't wait for some information.

--I had a buddy who swore by Crisco oil on his mountain bike chain. I never tried it, but hey whatever floats your boat!
I Hope this isn't your friend!

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Old 12-15-2016, 01:28 PM   #12
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Motor Testing

i'm going to need help on this one.

Measuring KV is easy. EG: apply voltage to ESC, aim tach at motor.

Measuring Power is easy. Apply a load to the motor, and look at the readout of a power meter. The alumininum disk, and magnets will come into play there too. Adjusting the distance between the magnets and the aluminum disc changes the load on the motor, that will allow us to test "at" an rpm, instead of measuring the acceleration of a weight. Which also, inadvertanly, ends up testing the software in the ESC.

Ir is a little more tricky. IIRC our motors are wound as a delta. This means if you're measuring between two terminals, you're also measuring between the other two sets of terminals. If someone has an easy answer, I'm open to it. I'm thinking about methods to get the resistance of each coil... but it's not going well.
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Old 12-15-2016, 01:43 PM   #13
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Oh, and i'm doing this in public so people can criticize it. If you see something wrong with a testing methodology, speak up!

Is there something you want to see tested? Lets discuss how to test it.
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Old 12-15-2016, 01:50 PM   #14
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Quote:
Originally Posted by Nerobro View Post
Is there something you want to see tested? Lets discuss how to test it.
Shock fluid. I'd be curious how the same wt/cst from different brands actually compare, since I hear that they're often quite different. Not sure how to test it though.
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Old 12-15-2016, 01:51 PM   #15
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Originally Posted by Nerobro View Post
Motor Testing

i'm going to need help on this one.


Ir is a little more tricky. IIRC our motors are wound as a delta. This means if you're measuring between two terminals, you're also measuring between the other two sets of terminals. If someone has an easy answer, I'm open to it. I'm thinking about methods to get the resistance of each coil... but it's not going well.
You'll only get the measurement reading for the shortest distance between the windings. Your meter isn't going to measure the LONG way around the delta or wye. I wouldn't sweat this, dyno test motors instead.

Use a heavy flywheel and accelerate it. Whatever motor gets it up to speed 1st, is the fastest.

By the time you get the motors all tested, they'll be obsolete. Brushless motors are still missing many key ingredients to make more power. The motor companies are likely holding onto those tricks, and releasing them one at a time so they can make us buy new motors every two years or so.

Concentrate on your other tests first, they're all cheaper to test as well.
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