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
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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.