R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 12-15-2016, 01:58 PM   #16
Tech Elite
 
Zerodefect's Avatar
 
Join Date: Apr 2008
Location: Underground, Ohio
Posts: 4,305
Default

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.
Zerodefect is offline   Reply With Quote
Old 12-15-2016, 02:03 PM   #17
Tech Regular
 
Join Date: Sep 2010
Location: Chicagoland
Posts: 323
Send a message via AIM to Nerobro
Default

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.
Nerobro is offline   Reply With Quote
Old 12-15-2016, 02:04 PM   #18
Tech Elite
 
Join Date: Sep 2010
Location: Beneath a rock down by the river. Don't have money for van
Posts: 2,900
Trader Rating: 1 (100%+)
Default

Does this helps?

Can I help with anything? I have a telemetry project that could be useful.
__________________
( ͡ ͜ʖ ͡)
30Tooth is offline   Reply With Quote
Old 12-15-2016, 02:14 PM   #19
Tech Regular
 
Join Date: Sep 2010
Location: Chicagoland
Posts: 323
Send a message via AIM to Nerobro
Default

Quote:
Originally Posted by Zerodefect View Post
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.
If you look at it as if it were a circuit, you'd be measuring say.. a 1ohm resistor with a 2ohm in parallel. The reason I want to test them, is to see how consistant motors are coil to coil. I'm willing to bet we'll find some trends on "better" motors versus less good motors based on coil consistancy, and total resistance.

Quote:
Use a heavy flywheel and accelerate it. Whatever motor gets it up to speed 1st, is the fastest.
My trouble with this, is if we're testing acceleration, we're ~also~ testing the motor software. If people want to repeat my results, they're going to need the same ESC on the same software load. That gets ugly, fast.

Quote:
Concentrate on your other tests first, they're all cheaper to test as well.
That's the idea.
Nerobro is offline   Reply With Quote
Old 12-15-2016, 02:20 PM   #20
Tech Regular
 
Join Date: Sep 2010
Location: Chicagoland
Posts: 323
Send a message via AIM to Nerobro
Default

Quote:
Originally Posted by gigaplex View Post
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.
There are standard methods for testing oil. We can look those up. We can also build a simple "standard" rig to do testing on.

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.
Nerobro is offline   Reply With Quote
Old 12-15-2016, 02:49 PM   #21
Tech Elite
 
howardcano's Avatar
 
Join Date: Jan 2012
Location: Olathe, KS
Posts: 3,541
Trader Rating: 35 (100%+)
Default

Quote:
Originally Posted by Nerobro View Post
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.
Measuring power output accurately is definitely not easy. There are several threads here on RCtech, mine included, that detail some of the challenges.

The software is already tested by ROAR for non-timing "blinky" operation.

Quote:
Originally Posted by Nerobro View Post
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.
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.
__________________
Howard Cano
When race results are re-calculated using the IOF (Index Of Fun), I always win.
1993 ROAR 1/8 Pan National Champion
howardcano is offline   Reply With Quote
Old 12-15-2016, 02:53 PM   #22
Tech Elite
 
howardcano's Avatar
 
Join Date: Jan 2012
Location: Olathe, KS
Posts: 3,541
Trader Rating: 35 (100%+)
Default

Quote:
Originally Posted by Nerobro View Post
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.
The viscous fluids we use for shocks, oil, etc., all exhibit substantial non-Newtonian behavior, and significant temperature sensitivity.
__________________
Howard Cano
When race results are re-calculated using the IOF (Index Of Fun), I always win.
1993 ROAR 1/8 Pan National Champion
howardcano is offline   Reply With Quote
Old 12-15-2016, 02:56 PM   #23
Tech Elite
 
DesertRat's Avatar
R/C Tech Elite Subscriber
 
Join Date: Mar 2011
Location: Sniffin the 'Sauce Fumes
Posts: 2,570
Trader Rating: 1 (100%+)
Default

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.
__________________
I race toy cars for fun. If I need to explain, you'll never understand.
Current rides: Diggity DC4 Chassis #10. Losi JRX-S Type R. CRC Xi (retired), CRC Altered Ego Aluminum Chassis. Associated B4 based dirt oval late model.
WTB: Carpet racing in Arizona.
DesertRat is offline   Reply With Quote
Old 12-15-2016, 02:59 PM   #24
Tech Regular
 
Join Date: Sep 2010
Location: Chicagoland
Posts: 323
Send a message via AIM to Nerobro
Default

Quote:
Originally Posted by howardcano View Post
Measuring power output accurately is definitely not easy. There are several threads here on RCtech, mine included, that detail some of the challenges.
I was going to use input power as a proxy for output power. It's not strictly correct.

Quote:
The software is already tested by ROAR.
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.

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.

Quote:
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.
Y wound.. does that explain the "half" turns?

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.
Nerobro is offline   Reply With Quote
Old 12-15-2016, 03:01 PM   #25
Tech Elite
 
howardcano's Avatar
 
Join Date: Jan 2012
Location: Olathe, KS
Posts: 3,541
Trader Rating: 35 (100%+)
Default

Quote:
Originally Posted by DesertRat View Post
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.
Silicone shock oil also exhibits decreasing viscosity with increasing shear rate.
__________________
Howard Cano
When race results are re-calculated using the IOF (Index Of Fun), I always win.
1993 ROAR 1/8 Pan National Champion
howardcano is offline   Reply With Quote
Old 12-15-2016, 03:04 PM   #26
Tech Elite
 
DesertRat's Avatar
R/C Tech Elite Subscriber
 
Join Date: Mar 2011
Location: Sniffin the 'Sauce Fumes
Posts: 2,570
Trader Rating: 1 (100%+)
Default

Quote:
Originally Posted by howardcano View Post
Silicone shock oil also exhibits decreasing viscosity with increasing shear rate.
its complicated but if its in a shock with holes to pass through quickly it can flow as a turbulent fluid and become effectively more viscous, but that's really only an issue for offroad cars landing jumps. We try to keep our cars on the track.
__________________
I race toy cars for fun. If I need to explain, you'll never understand.
Current rides: Diggity DC4 Chassis #10. Losi JRX-S Type R. CRC Xi (retired), CRC Altered Ego Aluminum Chassis. Associated B4 based dirt oval late model.
WTB: Carpet racing in Arizona.
DesertRat is offline   Reply With Quote
Old 12-15-2016, 03:06 PM   #27
Tech Regular
 
Join Date: Sep 2010
Location: Chicagoland
Posts: 323
Send a message via AIM to Nerobro
Default

Quote:
Originally Posted by DesertRat View Post
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.
Contact life of connectors is a thing. And age does mater. That ~does~ need testing. Or at least manufacturer quotes.

Quote:
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.
I found that changing grease used in my gearboxes made a very big difference in the amount of friction in the gearbox. I think that's worth testing.

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.

Quote:
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%.
Wouldn't it be nice to have an article to point someone to to demonstrate that? I think so.

Quote:
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.
It should be, but ROAR has now taken to testing IR, so there must be some kind of difference. Even if it's not "a big difference between brands" I suspect it IS a big difference generation to generation.
Nerobro is offline   Reply With Quote
Old 12-15-2016, 03:09 PM   #28
Tech Regular
 
Join Date: Sep 2010
Location: Chicagoland
Posts: 323
Send a message via AIM to Nerobro
Default

Quote:
Originally Posted by DesertRat View Post
its complicated but if its in a shock with holes to pass through quickly it can flow as a turbulent fluid and become effectively more viscous, but that's really only an issue for offroad cars landing jumps. We try to keep our cars on the track.
And mach. It's called "packing" by the suspension companies. To control that, cars and bikes have gone towards higher and higher lever ratios on shocks, so that piston speed is well controlled.

They also use blowoff valves, and one way valves to allow for separate compression and rebound speeds. And for limiting packing.
Nerobro is offline   Reply With Quote
Old 12-15-2016, 03:09 PM   #29
Tech Elite
 
howardcano's Avatar
 
Join Date: Jan 2012
Location: Olathe, KS
Posts: 3,541
Trader Rating: 35 (100%+)
Default

Quote:
Originally Posted by Nerobro View Post
I was going to use input power as a proxy for output power. It's not strictly correct.
That would not be accurate enough to draw any conclusions.

Quote:
Originally Posted by Nerobro View Post
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.
I'd be the guy to ask about the ROAR test.

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.
__________________
Howard Cano
When race results are re-calculated using the IOF (Index Of Fun), I always win.
1993 ROAR 1/8 Pan National Champion

Last edited by howardcano; 12-16-2016 at 03:58 AM. Reason: Corrected "uS" to "us".
howardcano is offline   Reply With Quote
Old 12-15-2016, 03:13 PM   #30
Tech Elite
 
howardcano's Avatar
 
Join Date: Jan 2012
Location: Olathe, KS
Posts: 3,541
Trader Rating: 35 (100%+)
Default

Quote:
Originally Posted by Nerobro View Post
It should be, but ROAR has now taken to testing IR, so there must be some kind of difference. Even if it's not "a big difference between brands" I suspect it IS a big difference generation to generation.
Yes, there is a big difference.

And unfortunately ROAR has only specified a minimum resistance for 25.5T motors.
__________________
Howard Cano
When race results are re-calculated using the IOF (Index Of Fun), I always win.
1993 ROAR 1/8 Pan National Champion
howardcano is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 07:32 AM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net