Timing on Brushless motor
 

I am trying to set my touring car to the approved racing parts and I need some guidance to buy a 17.5T motor. I find "EcoPower Slingshot SLV" but the timing on the rear panel seems inaccurate as I tend to join the Blinky class. If someone check the image below it seems I can not set the motor to 0 degrees (zero timing) while some other motor specify the 0 point on the timing gauge. Do I get some help on that?
https://cimg6.ibsrv.net/gimg/www.rct...7a075a5364.jpg
https://www.amainhobbies.com/ecopowe...p-8003/p968778

Unless your track has special rules, "zero timing" for blinky class refers to electronic timing in the speed control. There is (normally) no rule on where the motor's mechanical timing can be.

stock blinky zero timing means zero addition timing on the ESC. Most people that racing stock blinky set the timing on the motor close to maxed out usually somewhere in the 40-50 range. When the ecs is still for zero timing or no additional timing the light will blink red. Thats how you know your in blinky mode. Total timing is timing on the motor plus what ever timing you add through the esc. Most boosted stock class use a 13.5 motor and you can add timing through the esc. Typical timing for a boosted 13.5 is somewhere in the 20-30 on the motor and an additional 60+ through the esc.

If you set your 17.5motor timing to zero or close to it your car will be crazy crazy slow. Significantly slower than anyone else racing in the 17.5 blinky class because everyone's timing on the motor is set to 40-50

typical motor setup for 17.5 touring car blinky class is 40-50 timming on the motor and somewhere in the low 4"s for the final drive ratio.

Zero timing as others have noted here is what's found in the esc when setting the boost or turbo within the esc itself. When the degree indication on both boost and turbo in the esc reads 0 that's when the esc is set to run with zero timing. Zero timing is specific to what's set in your esc *only*. The timing on the motor can be set to whatever you choose based on the temps you get based on gearing choice, size track, layout of track, indoor or outdoor as climate temps also play a part. From what I've read the preferred motor temp after running for 5-6mins should be no higher than 160F, some run just beyond but most esc's lowest heat cut-offs are 185F. So with that it's best to ask at your track what's the common FDR(gearing) used and go from there. Also take note that not all motors will have the same behavior when set to the same degree of timing. Some will be faster and others slower.

Thanks.

i would recommend 42 as a starting point but don't trust the can markings. Find someone with a Motolyser to set it. I have seen as much as 14 degrees of difference between the can markings and actual timing.

With a 17.5 motor, my dyno showed diminished efficiency that will cause excessive heat after about 30 degrees. But there are a lot of other variables to contend with at the track. Different dynos might show other results too depending on how they are measuring the current going into the motor ("Electrical Energy Consumed" in the diagram). Mechanical power output is calculated from RPM data of a disk of known mass and dimensions.
https://cimg2.ibsrv.net/gimg/www.rct...ae80637918.jpg

From my experience different motors (brand / model) will react differently to timing. For example in 25.5, the reedy sonic will cook itself at the same timings the the R1 and Revtech motors like to be at.

this is very good information but I cant calibrate myself to it. do you have the labels backwards? a 17.5 should be putting down at least 100 watts on chassis. Im not nay saying your results. you have created something very helpful but maybe the data points are off a bit.

I wouldnt be shocked to see a 17.5 put down 175 watts on chassis and 225-300 motor only.

hmm I wonder who’s chassis dyno is this ? Lol jk

https://cimg9.ibsrv.net/gimg/www.rct...97a394437.jpeg
https://cimg0.ibsrv.net/gimg/www.rct...dd4d67898.jpeg

I use a Fantom Dyno and typically 42 is a spot that efficiency will peak. After that you still see the power gain but efficiency drops faster than the power gain. Bottom end torque also begins to fall off after 42. Very few motors don't do this.

Marcos-not a bad little dyno.

old dude-What you are seeing is called “field weakening”. its a tool used by motor control manufacturers.

at about 42 degrees the timing is not very good for low rpm. the coils are firing a little late so low rpm suffers but as the motor rpm increases the timing gets closer to ideal. if the coils are fireing a little late then the voltage difference between back emf and forward emf grows. this is what happens when you add a bunch of timing and your kv jumps up. you get more rpm but less torque down low. Servo controllers intentionally weaken the field to extend rpm. they just wait to weaken it until you reach high rpm so that good timing down low keeps the power there.

so thats great. mfgs can retain low end power and widen the curve at high rpm. they get twice the benefit. low rpm and high rpm. but they can move timing any way they want at anytime and a blinky motor cannot. its fixed. so what is the benefit of me explains this if we dont have dynamic timing (in blinky)? yes above 42 will take away power from low end but you cant stop that. But what if you arent using low rpm on the motor? then you dont need low end torque and efficiency. you still have the option of field weakening to create top end efficiency. when I say top end efficiency its not the same as bottom end efficiency. it takes away a little torque in the middle and adds a little rpm in the end. peak power will drop but if you need a wide curve at high rpm this is the way to do it. However I think most people think that because on the motolyzer it spins faster that its creating more power. its not. it widens the power.

100% agree and I also see that with the Fantom. The power curve widens as you increase the timing and has a higher peak. But as I stated the amp draw increases but not at a match. On track data aq. shows thta on our tight indoor tracks you need the bottom end to be there. So we typically get the motor to work in that bottom end of the curve. Peak RPM on the track is typically 75% of free rev when you have the spot. Data collected with a Tekin esc. For oval I start with the average per lap RPM at 1/2 of peak for gearing.

that makes perfect sense. your rpms are probably sitting right on top of peak efficiency at 42 degrees if you are gearing for that.

there is a use for field weakening in fixed timing if you only have 1 motor and and need to extend the efficiency curve but its difficult for most people to apply it. I cant think of a reason to use it on a short course though. we should start a thread for the motors we dyno. the data isnt published anywhere. I started one a long time ago. efficiency and torque versus rpm. 42 degrees, 50 degrees and full boost. This would create a nice database of low end torque, field weakening, and theoretical max. I think a few people would add to the data.

in motor control (industrial world) people interested in motors start by thinking about power. in our world a single peak on the torque rpm curve. Then they realize that on a PMDC motor that having so much torque at low rpm allows you to look at a mechanical system different and that power does not matter. each point of torque on the curve at low rpm is more important than the peak power. you get to this point when someone tells you that a motor 30% smaller will do the job than you thought you needed based on hp. You either believe the person or you ask them to prove it.

they ask you about the mechanical system, mass and the track. then they ask about the speeds for different point on the track and create a demand curve. basically its 10000 rpm for 3 seconds, 5000 rpm for 5 seconds...it describes all the accel/deceleration and constant work. they take your dyno curve and put 2 dots on it. 1 dot is the average rpm and average torque. if its under the dyno curve the motor will work. usually its well under the curve and they show you a motor that is more appropriate. But I said 2 dots. the second dot takes you to full on motor selection guru.

our dyno curves tell us nothing about heat. an efficiency curve tells you a little about the opposite of heat but its not as easy to use as having 2 curves in one. industrial motors have what is called continuous duty ratings. this is simply our dyno curve divided by the motors ability to dissipate heat continuously to 55C. so you get a curve that sits under our dyno curves that when you plot the first point you know the motor will never overheat (ever). Our dyno curves become the intermittent duty cycle. for example 200% of continuous duty. which basically means if you run the motor on our dyno curves it will overheat in say 1 minute.

So how does an EV like the tesla run massive acceleration torque and not overheat? the car is designed to drive at say 80% duty of the continuous torque curve (heat adjusted curve). but you have a limit of 200% for 1 minute or 300% for 20 seconds or 400% for 1 second. if you average all of the peak and continuous power and it sits below the continuous duty curve it will never overheat. so you can really accelerate for a short amount of time if you give the motor time to cool by driving at 80% for awhile.

well I cant walk everyone through how to build this heat modified curve but thats not the point. when you set a motor up to use a continuous and intermittent curve you find massive amounts of acceleration and hidden power by modifying the mech system. You will have learned that heat management of an electric motor is everything.

to review and summarize. applying an electric motor comes in 3 stages. 1-understanding peak power 2-getting 30% more out of a motor by understanding all the torque points on the curve 3-realizing that an electric motor is not like any experience you can draw from because they are all about heat control. the torque and rpm is ludicrous when you know how to control heat.

As if my techno babble about power wasnt enough to confuse people. There are a few of you who understand what power is. fewer people dabbling in the how to measure the track to match the physics to the motor. and maybe a few who see signs that manipulating heat constraints unlocks the motor completely. These comments are to point to a horizon for you know matter where you are at in your quest to understand motors. Please disregard something that doesnt make sense. it may eventually if you want.

Just to clue you in as you are very much into industrial motor control. I was a mechanical engineer and worked very closely with the electrical/control engineers. I often was working the mechanics with them to optimize performance typically in the area of inertia matching. I have been out of that for 12 years now after 36 of them involved with it. I keep digging for ways to apply what I know and learn new things all of the time. Once a engineer, always one.

well then we are birds of a feather. While in school I worked at Honda on the machine design team. i went to work for Mori Seiki (Fanuc and Mitsubishi guy), then indramat that turned into Mannesman Bosch Rexroth. I started as the the guys who designed the control systems (starting with servos and spindles) for whatever new job we had. Indramat developed the first digital ac servos (not me) and i was responsible for all the inertia mismatch in the great lakes region. At that time most of the competition sized based on horsepower. you very well could have gotten a design from me starting around 94. If you were using our stuff and had a bad sizing from a distributor or elsewhere...oops. I got lucky. Indramat guarenteed designs and I had good teachers. Indramat basically owned the auto industry back then.

if you are trying to find ways to apply what you know we are like minded. at some point I would like to model a chassis in a motor selection software (some still prefer to do it by hand) and use the rules of thumb for inertia on a BLDC motor. based on the way we accelerate and decelerate I would match the motor rotor to the chassis below 30;1. but based on just looking at the way we accelerate and decelerate I think its a little too high. position10>1, reciprocate 30>1, and line shafting at 60>1. I wont hog all the glory if you want to crack that nut.

I dont think that a dead weight on the motor shaft would be illegal.

​​​​​​Dead weight on the motor shaft or a heavier rotor shaft would achieve the same goal....

and there is is the famous “Vibranium” rotor

Oh there was some rotor inertia drama in the past?

it has a purpose. Im still not sure how much it would do in rc. the reason its a thing at all is that Drives with closed loop control (not an esc) have 3 closed loops running simultaneously and they fight each other for processor time. And the code is sequential not simultaneous so these loops fight each other. Current, velocity and position. ESCs only have 1 loop. so a resistance to change in speed or efficiency in change of speed can be managed by rotor inertia (or mass accelerated if thats simpler). if you know the math for each type of application you can control oscillations or lack of response from the motor. in its simplest form ..some motors cog at low rpm. adding the right amount of weight will end the cogging. at higher rpm the cogging still exists and maybe its enough to create some error in the hall effect sensors. there are small differences in acceleration between motor phases that can create small timing errors.

it would be like balancing a tire. but instead of 1 weight at the right spot its a bigger weight on the entire tire. there is more to it then what i explained but that is the fundamental.

This is a motor dyno and the numbers on the axis are not calibrated to anything. The software gives a relative number simply called "Power" for comparison between motors. The difference between the two curves is HEAT (conservation of matter and energy: horsepower = watts = jouls/sec heat)

Also, as anyone who has checked can attest, the marks on the endbell are almost never correct. So, hand-in-hand with this test is first a test to find the true Zero on the endbell. When that condition is met, most motors I checked have somewhat similar curves. If I designed the motor I'd have a big cooling heat sink, but the point is moot now, as our track is CAN-AM handout motor. So the dyno is just for fun.

My dyno is setup different from old dude. I found with experimentation that this particular ESC (and only this one) will power up by being back-fed through the servo cable even when it is turned OFF. So for my tests the ESC switch is actually always OFF. That is crazy but it works, and the light on the ESC lights and shows full throttle, but the motor does not surge or pump with the servo driver (blue box) set to 100% throttle. With this setup, the disk remains perfectly still until the power hits the ESC, controlled from the software start button. So the disk spins up instantly with full throttle from a standing start.


https://cimg7.ibsrv.net/gimg/www.rct...34944d16a9.jpg

A little off topic, but in case anyone out there with a Fantom dyno wants to use it with Brushless, I call this the old dude method, from what he showed me and, unlike the method above, it works with all ESCs that I tried. The car's transmitter is set to an 'instant on' throttle curve and you pull the trigger at the same time you click the 'start' button on the software.


https://cimg6.ibsrv.net/gimg/www.rct...4169d979f8.jpg

How good is your dyno?

This is a test result of a R1 v21 21.5 under load set at 41 degrees timing with a motor analyzer...
Tell me what do you see?

https://cimg5.ibsrv.net/gimg/www.rct...5c51a0c4fc.jpg



https://cimg6.ibsrv.net/gimg/www.rct...e66ea8e2e1.jpg

Ok. Ive been pondering this curve for days. there is allot of “stuff” underneath it. there is so much underneath it the curve feels more like something that says “trust me”. I want to but I also need to be able to apply it.For example the vertical axis is power which makes it difficult to abstract allot. the peak of power moves with timing and diminishes. which means anything that has field weakening is going to look bad. the results will always be severely skewed but because peak power drops but also it widens. if the vertical was torque rather than power it would be easier to conceptualize and more information could be abstracted. I could apply it to things of done in the past as a truth test (in my head). I assume voltage is fixed anyways and torque is the result of current. Any chance I can get you to create this curve with torque or current on the left? If you remove “power” from the equation the power constant wont interfere with deep thought, which also means there wont be a tendency for all things to appear as a crossover point at 5252 rpm.

it appears that your curve is like a summary of the difference between electrical power in and mechanical power out. it basically says that field weakening does nothing except generate a bunch of heat. but we know that field weakening improves high rpm response by removing low rpm response. I cant see that in the curve because there is only a tangential reference to speed as an element of power. In other words I cant see the drop in efficiency at low rpm and high rpm with the power picking up around the timing mark. Peak torque should be very close to 1 rpm but power is a measurement that crosses over itself which makes this even harder to understand. you add another degree of freedom to the data with timing. which takes it beyond my brains capability.

Dont get me wrong. I understand the concept you are trying to communicate. its a simple and unique approach to an interesting issue. It even looks horribly simple which is always a bonus in my book. its just at a level that I cant apply it to future problems, I cant check it with my own experience, and there isnt underlying data to help. I live to solve puzzles and Im excited to have an opportunity at this one. Im just hoping for more info.

if the vertical was the slope of torque and rpm, or just torque, or just rpm I could look deeper in to applying the info.

How good is your Dyno, continued..
 

Further to this post, I have additional slides to help explain why I asked anyone if they can tell me what they see...
The graphs above contain some interesting details on the performance of the motor that I own.

In the two graphs, you can see the length of time the motor need to spool up to reach maximum RPM. The timing on the motor for this test was set at 41 degrees, measured with a motor analyzer. There are two pieces of info that stand out in the graphs.. The first is what you see on the current (amp draw) graph, just after 2.24 seconds, you see a dip in the current and if you use your mouse cursor if using a computer, line it up with that spot and then scroll without moving it. The same spot on the RPM graph could be interpreted as the start of the power band, up until the motor starts to cog, which you can clearly see at the end of the current graph.

Now the next graph is the voltage, which for this test the lipo I have was at storage voltage 7.6v re-peaked with icharger.

https://cimg8.ibsrv.net/gimg/www.rct...18021e0baa.jpg

Then torque, power, efficiency and current all over RPM.

In this graph you can see lots of good details, and with a 1:1 ratio, the RPM can be match to with data loggers to ensure you select the best gearing for your layout..
Now does the setting of 41 degrees create the best torque and overall power? Not sure as I need to do more testing to validate this. However as Bry195 mentioned before, "as you increase timing, you are field weakening", which is also known as widening the power. However when it comes to spec racing, you need to find the setting that produces the torque and power that the motor can produce before it starts to generate too much heat. Remember that as you widen the power band, and depending on the track layout you have in front of you should also influence what setting you select. If grip is high, its a no brainer, torque.

https://cimg0.ibsrv.net/gimg/www.rct...2f23150ecb.jpg


Lastly here is a comparison of two motors, with one motor at two different timing settings. You can see the field weakening that happens when you go from 30 to 41 degrees timing for the motor.


https://cimg9.ibsrv.net/gimg/www.rct...115a3bb012.jpg


For those who are interested in seeing the field weakening results of the R1 v21, I will be posting the results soon on my Facebook page.

your first curve shows a peak around 7000 rpm. at 7000 rpm divided by the fdr and multiplied by the distance the tire rolls gets you a fast lap time thats the right timing. you can calculate the what the track needs by selecting a time to run a lap over the distance and convert to rotations per minute at the motor.

if the gearing wont let you use 7000 rpm then set it to run the motor at 7500 and adjust the timing to 41. this is just an example (not a great one but for demonstration). a better example would be if the track needed 10000 rpm. maybe 52 degrees of timing and gear to 10000 rpm.

67 volts? did I see over 400 amps? wow, I get less than 200 amps on a 17.5 at 8+ volts but I never ran that low of voltage.

On small tracks, I find corner speeds for hairpin turns can be as low as 3000-3500 rpm, and accelerating out of them with peak around 7000 rpm gives very good exit speed when you gear correctly.

In response to your question about 67 volts, the scaling on the power run fitting module defaults to a different unit of measure which is why you see the high values. The graph showing torque displays correctly when you adjust the settings.

Question for everyone here:
I may be able to pick up a CE Turbodyno. As it is not a flywheel, do you feel it can still give useful data?

thats interesting. I looked at pictures. does it have a motor as the load for the test motor? I think this is a brushed system isnt it?

if you want to test a motor you have to simulate the acceleration loads and the work loads. a flywheel dyno is great for measuring power during acceleration but after acceleration it doesnt provide useful data. it does provide data that allows you to match inertia so that deceleration and acceleration can be tuned.

a load dyno can provide power curves and simulate the work that has to be done at a constant speed so its good for measuring power, torque, rpm. it doesnt help with inertia. but what it does very well is allow you to test the thermal characteristics of a motor under work conditions. this allows you to determine the max power a motor can deliver without overheating.

if you had an inertia and load dyno in one you would need to do less testing and math to understand everything a motor can do. if the flywheel matches the inertia your chassis normally introduces during acceleration you have 1 of 2 pieces of physics covered. the second piece is the friction and and efficiencies of the chassis which can be simulated by the brake motor (the second motor) resisting the same way tires and belts and ... does on a chassis.

but there in lies the problem. you can calculate the inertia and pick a flywheel to simulate. but then you have to determine how much power is lost between the motor and the wheels to setup the load motor to introduce those same losses.

If it were me and you wanted to cover these two pieces of physics I would get a chassis and add a load motor. you can run a fixed pwm to the load motor to simulate friction on track but its will be different for each track. it would also be flight cheaper to get a motor acceleration dyno and add a load motor that would simulate heat rain and road conditions.

in short I wouldnt convert a motor only load dyno over to brushless unless you are pretty decent with DIY. if you dont simulate the inertia under acceleration you are only half way there.

max rain-you may find more power and less heat if you come into a corner at 3000 and exit at 10,500 because the average corner speed of 7000 is your peak power. peak efficiency will be 15-20% higher so it would come out even cooler.

There are chassis dynos with load motors. I have one but it is a simple one. Bank of resistors to give three loads. Simple amp draw of test motor and load motor voltage generation to determine wheel speed. Have thought about equipping it with a accurate sensor system for true motor rpm via the sensor wire tap off.
I will add one of my theories that is backed by Tekin esc data. On tight indoor road courses or ovals, the motor is always in acceleration or deceleration. Hardly ever does one peak out unless your gearing is too low. To get the most from a motor, it must be worked as much as possible.

Its a very good dyno, and very simple to convert to brushless. The only thing really required to go brushless is to use a brushless speed control between the test motor and the dyno. You will be required to have the speed control "on", so have the switch turned on, on the speed control. Eliminate the use of a receiver and transmitter by using a servo tester, and adjust it to full throttle.

yea I have the minipro chassis dyno. its flywheel is aluminum. so I have an electromagnet pulsing eddycurrents on the flywheel.

an acceleration and load dyno are very good at calculating power. the accel dyno does some things batter than the load dyno and vice versa. One of the advantages of a load dyno is it can pinpoint the exact amount of peak work you can do continuously before the motor overheats. so if you add 80 watts of resistance to a 150 watt motor and it almost overheats after running it for an hour you know that the motor can dissipate 80watts/second of heat. this means 80 watts in acceleration/deceleration or constant power.

if you know that a corner that goes from 5000 rpm on entry to 10000 rpm on exit over a 1 second time fram the average rpm is 7500. the efficiency over that range goes from 40 to 60 so you have an average of 50% efficiency. if the average power at 7500 rpm is 150watts and the average efficiency is 50% 75 watts. you can run that corner indefinately. or you can run the next corner at 85 watts of dissipated heat and still stay under the thermal limit.

so if you set the motor to run 150% for 1 second the next second should be 50% so that you stay under 100%. you can look at it this way in seconds or minutes or laps or ...

furthermore you know 100% is 160f. if you like 130f you know that the average efficiency has to stay at something like 80%.

so then you realize that instead of setting the motor to take the corner at 5k in and 10k out that you get 15% more efficiency if its 7.5k in and 12.5k out. so instead of an average efficiency of 50% you have one of 65%. which means the motor can come off cooler or you can save that efficiency for the next corner.

it gets complicated if you try to follow it all in one go but if you take it step by step you will understand how to adjust power in the unique way that electric motors deliver it.

you will also see the point of over timing a motor in special situations to induce field weakening.

There is lots of truth to this explanation..
In my own testing, if you are reaching temps of 130f with a fan on the motor at the end of your race running with 80% efficiency, it gives you a safe operating window in case the fan stops cooling the motor for what ever reason. Testing without a fan, I have seen temps reach 155-160 with the same efficiency.

yea, it can be a pretty big difference. but using the efficiency per second you can figure out what the temp will be with a fan and without and pick what you want. liquid cooled allows you to dissipate about 10 times more than natural convection.

Once the heat management and efficiency becomes the “prime directive” power almost becomes irrelevant. A result of thinking about heat per second is that once you do it you learn how to think about torque per second rather than overall power and you have the right power available when it counts as a result.