Testing - What's better? Lets do some science, and share the results.
12-15-2016, 01:58 PM
#16
Wire resistance should be tested under load.
Measure voltage drop across 3 feet of RC wire while the car is scrubbing tires on carpet. One lead on ESC A and motor A. Should read 0. Any voltage difference measured is your voltage drop for the wire.
Do the same test on the battery leads. You'll quickly find that RC wire is greatly oversized most of the time.
As for connectors. Just cut the plug off of a heater, drier, air compressor, load bank, or something. Any kind of load that we know the connectors can't handle. And wire them in. Then just measure temps that the connectors increase.
Measure voltage drop across 3 feet of RC wire while the car is scrubbing tires on carpet. One lead on ESC A and motor A. Should read 0. Any voltage difference measured is your voltage drop for the wire.
Do the same test on the battery leads. You'll quickly find that RC wire is greatly oversized most of the time.
As for connectors. Just cut the plug off of a heater, drier, air compressor, load bank, or something. Any kind of load that we know the connectors can't handle. And wire them in. Then just measure temps that the connectors increase.
12-15-2016, 02:03 PM
#17
Enviromental Data
When we do a test, we should record the starting temp, ending temp, and barometric pressure. If doing the test outside, we should also note the relative humidity. A note of time of day, and lighting conditions may also be relevant for eliminating "weird" readings.
General Testing Methods
1. All tests should be done ~at least~ three times. If there's any significant difference in readings (say.. more than 5%) testing should continue. I need to talk with some mathy type folks to determine a good number to work from.
2. All tests that involve motion must be done somewhere that has zero wind gusts. EG: in a shed, in a room. In a room with a fan on.
3. All tests involving motion should be preformed on a level, rigid, surface.
4. All rpm measurements should be made with a non-contact tachometer.
5. All measuring equipment should be noted for the test. Model numbers, calibration dates, calibration methods, etc... "none" is ok, so long as it's noted.
When we do a test, we should record the starting temp, ending temp, and barometric pressure. If doing the test outside, we should also note the relative humidity. A note of time of day, and lighting conditions may also be relevant for eliminating "weird" readings.
General Testing Methods
1. All tests should be done ~at least~ three times. If there's any significant difference in readings (say.. more than 5%) testing should continue. I need to talk with some mathy type folks to determine a good number to work from.
2. All tests that involve motion must be done somewhere that has zero wind gusts. EG: in a shed, in a room. In a room with a fan on.
3. All tests involving motion should be preformed on a level, rigid, surface.
4. All rpm measurements should be made with a non-contact tachometer.
5. All measuring equipment should be noted for the test. Model numbers, calibration dates, calibration methods, etc... "none" is ok, so long as it's noted.
12-15-2016, 02:14 PM
#19
Use a heavy flywheel and accelerate it. Whatever motor gets it up to speed 1st, is the fastest.
Concentrate on your other tests first, they're all cheaper to test as well.
12-15-2016, 02:20 PM
#20
http://www.cscscientific.com/csc-cie...sure-Viscosity
http://www.machinerylubrication.com/.../oil-viscosity
And by standard, I mean "Who the heck has the right answer". I think we could do a dropping ball rig that would be consistent enough for our work. But it might take a whole bottle of fluid to fill it and test with.
There are some other wacky factors to think about. Not all fluids are newtonian, so "speed" may matter. And the viscosity to temperature rate may change as well.
12-15-2016, 02:49 PM
#21
Motor Testing
i'm going to need help on this one.
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.
i'm going to need help on this one.
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.
The software is already tested by ROAR for non-timing "blinky" operation.
Motor Testing
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.
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.
Our motors are Y-wound.
While you can use simple algebra to calculate the individual coil resistances from the measured terminal resistances, there is no reason to do so. The terminal resistances are the important parameter, because that's what is driven by the ESC.
12-15-2016, 02:53 PM
#22
There are standard methods for testing oil. We can look those up. We can also build a simple "standard" rig to do testing on.... There are some other wacky factors to think about. Not all fluids are newtonian, so "speed" may matter. And the viscosity to temperature rate may change as well.
12-15-2016, 02:56 PM
#23
Wire and connectors are all equal if they are the same gauge assembled correctly. Their conductivity also doesn't change unless you damage them. Learn to solder better joints, that may help a little but not much.
Grease, gear lube, and by association bearings (when fresh and undamaged) are useless to 'test' because more important that the grease or oil is how its applied and its temperature, also, grease is a non-Newtonian fluid that becomes LESS viscous as it is stirred up and put under shear faster, think of it like reverse shock fluid that flows easier the harder you hit it. It's anti-wear properties are its important feature.
Much more important to gear efficiency is having the correct mesh instead of its material. A metal-on-plastic gear is very efficient, on the odds of 99%.
Motor IR could be useful, but should be very nearly the same across all brands as they have basically specified how much wire and what gauge of wire it will contain. Quality control of RC motors is actually pretty good, so there are fewer "sweet" motors. This also needs to happen under temperature controlled conditions, and is subject to a fair amount of error.
Grease, gear lube, and by association bearings (when fresh and undamaged) are useless to 'test' because more important that the grease or oil is how its applied and its temperature, also, grease is a non-Newtonian fluid that becomes LESS viscous as it is stirred up and put under shear faster, think of it like reverse shock fluid that flows easier the harder you hit it. It's anti-wear properties are its important feature.
Much more important to gear efficiency is having the correct mesh instead of its material. A metal-on-plastic gear is very efficient, on the odds of 99%.
Motor IR could be useful, but should be very nearly the same across all brands as they have basically specified how much wire and what gauge of wire it will contain. Quality control of RC motors is actually pretty good, so there are fewer "sweet" motors. This also needs to happen under temperature controlled conditions, and is subject to a fair amount of error.
12-15-2016, 02:59 PM
#24
The software is already tested by ROAR.
I'm a big fan of brake, versus intertial dynos.
A brake dyno would also allow us to track motor temperature, and maximum sustained wattage.
Measuring stator IR is pretty darn easy with the proper equipment.
Our motors are Y-wound.
While you can use simple algebra to calculate the individual coil resistances from the measured terminal resistances, there is no reason to do so. The terminal resistances are the important parameter, because that's what is driven by the ESC.
Our motors are Y-wound.
While you can use simple algebra to calculate the individual coil resistances from the measured terminal resistances, there is no reason to do so. The terminal resistances are the important parameter, because that's what is driven by the ESC.
Measuring terminal to terminal, is easy. Provided clean contacts and a meter that can handle low resistances.
I still wonder if matched coils has any effect on the motor.
12-15-2016, 03:01 PM
#25
Grease, gear lube, and by association bearings (when fresh and undamaged) are useless to 'test' because more important that the grease or oil is how its applied and its temperature, also, grease is a non-Newtonian fluid that becomes LESS viscous as it is stirred up and put under shear faster, think of it like reverse shock fluid that flows easier the harder you hit it.
12-15-2016, 03:06 PM
#27
Grease, gear lube, and by association bearings (when fresh and undamaged) are useless to 'test' because more important that the grease or oil is how its applied and its temperature, also, grease is a non-Newtonian fluid that becomes LESS viscous as it is stirred up and put under shear faster, think of it like reverse shock fluid that flows easier the harder you hit it. It's anti-wear properties are its important feature.
Also, people seem to have magic sauces that they believe make their bearings better. I want to test that. Debunk, or support, I don't care, I just don't like the "well I think it's better" or "My experience says" answer.
Testing the anti wear properties is going to be rather difficult on the scale i'm able to test.
Much more important to gear efficiency is having the correct mesh instead of its material. A metal-on-plastic gear is very efficient, on the odds of 99%.
Motor IR could be useful, but should be very nearly the same across all brands as they have basically specified how much wire and what gauge of wire it will contain. Quality control of RC motors is actually pretty good, so there are fewer "sweet" motors. This also needs to happen under temperature controlled conditions, and is subject to a fair amount of error.
12-15-2016, 03:09 PM
#28
They also use blowoff valves, and one way valves to allow for separate compression and rebound speeds. And for limiting packing.
12-15-2016, 03:09 PM
#29
I'll need to look up their testing methodology. My concern is that with a very heavy weight, cogging will be trouble. In which case we'll need to throw out the bottom end of the accelaration curve. On the other end, the software for turning on the coils at the right time, can have trouble with a quickly accelerating motor. By doing steady state measurements, we take rotating mass out of the equation.
The hardware or software used to drive the motor coils has no problems with accelerating load. The drive signals must follow the sensor signals within less than 10us. In its simplest form, the ESC doesn't even know if the motor is accelerating.
Last edited by howardcano; 12-16-2016 at 03:58 AM. Reason: Corrected "uS" to "us".