motor theorie en praktijk (huiswerk)

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Wouterb
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motor theorie en praktijk (huiswerk)

Bericht door Wouterb » 06 nov 2017 13:52

Gejat van de andere kant van de plas, van ene 'Olle P'.
De man lijkt te weten waar hij over praat (in tegenstelling tot ondergetekende). Evengoed had ik het idee het te kunnen volgen...

http://www.rccrawler.com/forum/electron ... ctice.html

Post Motor theory... and practice.
Investigating what’s behind the “Old Truths” and general advice regarding our typical use of electric motors.
This apply to brushed and brushless motors alike, although for brushed motors I’m aware that some of the mathematical models used only work well within a narrower voltage range. The general conclusions still hold though.
I’ve stuck to dissecting the influence of winding turns and feed voltage, since those are the primary factors that we as users can influence when choosing motor and battery. The rest of the internal motor hardware is simply assumed to be “constant”.
The article is very wordy and there are many formulas presented. I’ve broken this subject into one post for each motor property. Each post, apart from the last ones, is subdivided into a short presentation, Theory, Reality Check and Conclusion.


Introduction:
I’ve started this thread as a spin-off from another thread.

Originally Posted by JohnRobHolmes
Once inside the motor coils, the respective voltage and amperage that power is produced from doesn't matter if we keep the amp/turn and copper volume constant. The torque and power can't be changed with a different KV, low KV motors do not produce more torque. They do produce more torque per amp, but they also need higher voltage applied to get it. ...
In theory (and what seems like technically possible) John is correct, as shown below.

My previous statement, to the effect of “More turns => More torque, more efficiency and less Kv” stems from what’s generally accepted as the “truth” and also on the fact that the general (and good) advice is to gear down when switching to a higher Kv motor. I blame only myself for not previously having done the proper research…

Now I’ve spent some time going back to the basic physics of electric motors and compare that to reality to find out what is true.
The physics is simply an applied use of Ohm’s law, Faraday’s law, Kirchhoff’s voltage law and some other basic rules of electronics and mechanics.
For the mathematical models I’ve throughout assumed that all pieces of the motors except the windings are identical and constant. The amount of copper used for the windings is also constant (unless otherwise explicably noted).
“Reality” is represented by well proven general advice and experience as well as manufacturer’s data for the somewhat older range of Turnigy TrackStar motors. I used these motors because of the relatively exhaustive amount of data given and I run the 17.5T version myself. The full range isn’t directly comparable without caution since the motors up to 8.5T have an internal fan that the others don’t and some data lack precision. The 4.5T version can be found here.
I’m aware it’s not sufficient to have a select very few motors to make perfect conclusions set in stone, but it’s far better than having only the theories.
Some results are intriguing, to say the least…

Legend
Physics and maths go hand in hand when doing the theoretical study, so here is a legend for terms used later. Notice that there’s a difference between upper and lower case letters:
N = Number of winding turns.
R = Electrical resistance in the winding. Unit: Ω
f = Motor angular velocity, used as a variable. Unit: rad/s
f0 = Angular velocity at no load for a given voltage.
Kv = f0*π / 30*voltage. Unit: rpm/V (For brushed motors this is more voltage dependent than for BL motors. I use it as a constant though.)
V = Feed voltage, when used as a variable. Unit: V
V0 = The feed voltage, a constant.
VE = Electromotive Force. Unit: V
I = The electrical current through the motor. A variable. Unit: A
I0 = The no load current at a given voltage.
T = The torque. Unit: Nm
Ts = The stall torque.
T0 = The torque required to overcome motor friction.
P = Power. Can be electrical or mechanical. Unit: W
Pin = Electrical power drawn by the motor.
Pout = Mechanical power given off the motor axle.
Ph = Power generated as heat within the motor due to winding resistance.
Pm = Power generated as heat within the motor due to mechanical friction.
L = Load. A value from 0 to 1, often given as a percentage.
E = Power efficiency.
k[index] = used for various constants depending on the motor design
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Motor data explained

There are eight motors (older generation TrackStar) used for the “reality checks”.
These have the windings 3.5T, 4.5T, 5.5T, 6.5T, 8.5T, 10.5T, 13.5T and 17.5T.
The motors up to and including 8.5T have integral fans mounted on the rotors, which can be expected to add some loss of output torque. The results from this study show that in practice the fans have very little overall influence though.

What data is presented?
These are two-pole sensored brushless inrunners of 540-size. Good to know but mostly irrelevant.
Winding turns: Not much to say about that.
Kv-value: An essential piece of data.
Max voltage: Good to know.
Maximum current: Not how much the motor is willing to draw, but how much it can handle at a constant load without overheating at some unspecified level of cooling.
Maximum power: Not how much power the motor can deliver but the power drawn by the motor while fed the “maximum current” at the “maximum voltage”.
Winding resistance: Required for the mathematical models used.
No load current: My analysis indicates that it is valid for a 7.4V feed, not the maximum voltage.
Physical dimensions: Irrelevant for this discussion.
I think it’s a shame that the newer motor designs are not presented with as much data.
Laatst gewijzigd door Wouterb op 06 nov 2017 13:55, 1 keer totaal gewijzigd.
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Re: motor theorie en praktijk (huiswerk)

Bericht door Wouterb » 06 nov 2017 13:53

First property: Kv rating

The “old truth” is that “when the number of turns go down the Kv goes up”. Is it true?

Motor torque (required to overcome any internal friction and accelerate the rotor) is produced by the current running through the coils. The current is driven by the feed voltage and limited by the winding resistance. If these were the only factors involved the current would be constant and very high, with the motor accelerating until it broke down. Another factor is also limiting the current and this is the Electromotive Force (EMF) (a voltage).

Theory:
The current is thus defined by (V – VE[7size])/R.
Faraday’s law says that the EMF (at a given motor speed) is proportional to the number of turns.
VE = kF*N*f
At no load f = f0 = Kv*V0*π/30
VE = kF*N*Kv*V0*π/30 =>
Kv = VE*30 / (kF*N*V0*π)
Set VE ≈ V0 so VE/V0 ≈ 1 and we get Kv ≈ 30/kF*N*π
It’s obvious the theory states that if N goes down Kv goes up.

Reality Check:
With lower N-value the Kv does go up.
The theory says 30/(π*Kv*N) should be constant (kF). For the actual motor range it’s close, with kF = 0.000286±0.000013.

Conclusion: The old truth holds true!
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Re: motor theorie en praktijk (huiswerk)

Bericht door Wouterb » 06 nov 2017 13:55

Second property: Torque
Old truth: ”More winding turns gives more torque.”
Standard, well proven, advice: “When changing to a motor with less turns, gear down [to reduce the required torque].”

Theory:
The (total) torque depends on the current and the number of turns.
T = kT*N*I
Maximum current (and thus torque) is given at stall, when EMF=0V.
Then Ts = kT*N*V0/R
With the assumption of “constant copper” follows that if you double N the wire cross section is halved (doubling R) and the length of wire doubled (doubling R once more).
Thus R = kR*N^2
Giving
Ts = (kT*N*V0) / (kR*N^2) = (kT*V0) / (kR*N)
Look at that! Torque is proportional to 1/N. Say what? That’s the exact opposite of the old truth!
There must be something more to this…

So what happens if the motor manufacturers cheap out and use the same wire for all winds?
Then R is proportionate to N (wire length) so
Ts = (kT*N*V0) / (kR*N) = kT*V0/kR
Stall torque becomes a constant relative to N. It’s still not enough to verify, or even to explain, the old truth.

Reality Check:
Is the wire gauge constant or optimized?
In the motor range R correlates much better to N^2 (0.200±0.035) than it does to N (increase with N), so it’s optimized using available standard gauges.
From that follows that for a given voltage and load percentage a low turn motor will provide more torque than a high turn motor, opposing the old truth.

Intermediate Conclusion:
One conclusion is that high turn motors provide more torque at the same current, not at the same voltage. They need more voltage to reach that same current.
Higher torque (with low turn motors) allows for higher gearing, so one should expect broad recommendations to gear up when changing to a motor with fewer turns but instead the advice is to gear down. WHY?
I will return to this issue later on, since I think it’s related to the following properties…
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Re: motor theorie en praktijk (huiswerk)

Bericht door Wouterb » 06 nov 2017 13:56

Third property: Power
The “old truth” state that “with a decrease in turns the power goes up”.

Theory:
Mechanical power: P = T*f
I’ve already proven that Kv increase with lowered N, and shown that Ts also seems to increase with lowered N.

Neglecting the internal friction(*) to make the mathematical formulas cleaner:
For a given load L
T = Ts*L = (kT*V0*L) / (kR*N)
and
f = f0*(1-L) where f0 = kF*V0 / N
Thus
P(out) = (kT*V0/N)*L * (kF*V0/N)*(1-L) =
= kT*kF*V0^2*L*(1-L) / N^2

From this we can read that:
P is proportional to 1/N^2.
P is proportional to L*(1-L). (It’s 0 when L is 0 or 1 and there’s a maximum when L = 0.5.)
P is proportional to V0^2.

Reality Check:
For a car speed is a function of power. It’s well known that R/C race cars go faster if they get a motor with less turns.
It’s also well known that they go faster with higher voltage.

Conclusion:
The old truth holds true!

(*) The power lost due to internal friction is typically magnitudes smaller than the output power.
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Re: motor theorie en praktijk (huiswerk)

Bericht door Wouterb » 06 nov 2017 13:57

Fourth and fifth properties: Heat and Power Efficiency, part 1
The “old truth” state that “with a decrease in turns the power efficiency goes down”.
John Holmes use to say “Volt up, gear down” [to get less heat (and more efficiency?)].

Theory:
When running a motor of any kind the power fed to the motor (Pin) exceeds the mechanical power delivered by the motor (Pout). The difference comes out mostly as heat. (Combustion engines also have other losses.)
The relation between output and input is called Power efficiency (E) and is defined as E = Pout/Pin

The heat generated is something we generally don’t want but also can’t avoid.
From the definition of efficiency follows that for a given power out you get less heat if the efficiency is better.

The power “lost” in an electric motor is two-fold:
Heat as a result of wire resistance.
Ph = R*I^2
Heat as a result of friction.
Pm = T0*f
We know also that Pin = Pout+Pm+Ph

At no load:
Pin = V0*I0
Pout = 0W
Ph = R*I0^2
Pm = T0*f0 = kT*N*I0*f0

Put together: V0*I0 = R*I0^2 + kT*N*I0*f0
(Divide by I0.) V0 = R*I0 + kT*N*f0
V0-R*I0 = kT*N*f0
We know from post 2 that V0-R*I0 = VE at no load and that
VE = kF*N*f0, so now we get
kF*N*f0 = kT*N*f0, which is true only if kF ≡ kT
Let’s verify by dimensional analysis:
kF = VE / (N*f) corresponding to [V]/([1]*([1]/[s]) = [Vs]
kT = T / (N*I) corresponding to [Nm]/([1]*[A]) = [Nm/A]
At first glance [Vs] ≠ [Nm/A] but then I realize that
1Nm=1J=1Ws=1VAs so 1Vs = 1Nm/A and therefore kF ≡ kT.

Now we can also calculate T0:
V0*I0 = R*I0^2 + T0*f0
T0 = (I0*(V0-R*I0))/f0

Reality check #1:
(From here on the “reality” gets a bit shady, since it’s all a matter of applying the mathematical models on the given motor data, no actual measurements to verify that the models are correct.)
What’s the calculated value of T0 for the motors?
T0 = 16±6 mNm
Quite a spread, relatively, but the input data (especially I0) isn’t very high precision either…

Reality check #2:
What’s the heat generated in the windings?
At 7.4V and no load:
R*I0^2 = 0.36±0.15 W, so quite a spread, again probably due to poor precision in input data.
At maximum rated current:
R * Imax^2 = 15.4±1.0 W, Principally the same all over the range.
At 7.4V and stall:
R*Is^2 = V0^2/R = V0^2 / kR*N^2
For the 3.5T motor the heat generated at stall is a whopping 26.08 kW while for the 17.5T motor it’s a more moderate 1.07 kW.

Reality check #3:
What’s the mechanical heat generated at no load?
We’ve already stated that T0 is roughly the same for all motors whereas f0 is the inverse function of N, so lower turns means more heat due to mechanical friction.
At 7.4V for the 3.5T motor it’s 95.8 W and for the 17.5T motor it’s just 14.6W.
With load added the speed goes down and with that the internal heat generated by the friction (assuming the friction itself stays the same).

Intermediate conclusion:
At a constant voltage you get more heat from a motor with less turns. No surprise there…

Power efficiency
The heat goes up with less turns, but we already know that so does the output power as well.
Power efficiency (E) is the relationship between output and input power.
E = Pout / Pin
Pin = V0*I
Pout = T*f
I = (Is-I0)L + I0
T = (Ts-T0)*L
f = f0*(1-L)
Ts = Is*N*kT
T0 = I0*N*kT
f0 = V0/(N*kF)
kF = kT
E = (Ts-T0)*L*f0*(1-L) / (V0*((Is-I0)*L+I0)) = V0*N*kT*(Is-I0)*L*(1-L) / (V0*N*kF*((Is-I0)*L+I0)) =
= (Is-I0)*L*(1-L) / ((Is-I0)*L+I0)
Power efficiency doesn’t seem directly related to N although N does have some influence on I0.
Solving E’(L) = 0 says E reaches maximum when L = ((Is*I0)^½-I0) / (Is-I0)

Reality Check: #4
How does L for maximum E vary with N?
Optimum L goes up with N, from 5.73% for 3.5T to 10.82% for 13.5T. (The 17.5T motor as well as the 4.5T motor deviate a little from the trend.)
Looking at the numbers reveals a good correlation between optimum L and the square root of N.

So what’s the efficiency at optimum load?
At optimum load the efficiency is also somewhat dependent on N. Most efficient is the 3.5T motor at 88.6% and least efficient the 13.5T motor at 78.3%.
Higher turn motor is NOT more efficient!

Intermediate Conclusions:
It’s quite obvious that higher turn (low Kv) motors are not more efficient as such!
So let’s explore further to see where the “old truth” comes from…

Theoretical models applied to the motors:
Comparing the motors at 7.4V feed and the maximum rated current.
The 17.5T motor operates at its maximum efficiency. 10.5%load, 79% efficiency, delivering 99.4W power on the axle and 26.4W heat.
The 3.5T motor at the other end of the scale is far from its optimum load, at 2.0% load instead of 5.7%. Still the efficiency is 83%, the power on the axle is 508W and the heat generated is 107W.
This tells me the maximum current rating has little to do with the heat generated! (Actually, more current does mean more heat, but my point is that the “extra” heat doesn’t come from the winding resistance, and there’s also a difference in output while generating that heat. The value for maximum current doesn’t seem to correlate to the risk of motor overheating though.)
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Re: motor theorie en praktijk (huiswerk)

Bericht door Wouterb » 06 nov 2017 13:58

Fourth and fifth properties: Heat and Power Efficiency, part 2
This far I’ve compared the circumstances with same voltage and same load.
What about same output power? The power is what we want and use, so how does different motors behave while delivering the same power?

Case 1: Same maximum power, delivered at 50% load.
With the 17.5T motor running at 14.8V and 50% load it will deliver as much as 1,038W on the axle (slightly less power than the heat generated).
The motors with less windings need much less voltage to deliver the same power at 50% load. The 3.5T motor needs only 2.96V and will consume 73W less from the ESC while doing it!
Comparing the currents we find the 17.5T motor requires 146A while the 3.5T will need a full 707A.
Comparing the torque delivered at 50% load on these voltages we find it to be roughly the same across the spectrum, which isn’t surprising since the motors are also running at the same speed.
From an efficiency point of view it’s therefore in theory slightly better, or at least just as good, to use a motor with fewer turns running the same gearing on lower voltage.

Compare model to what’s feasible:
In real life there are some limiting factors that come into play.
Delivering 146A at 14.8V is hard, but not impossible using a 4S LiPo able to deliver 70C or more peak. There are ESCs able to handle it as well.
707A at 3V is much worse. Not many ESCs can handle that current, and it takes a battery pack typically of 1S 10Ah with 70C peak rating to do it (and matching cables and connectors).

Case 2: Same stall torque.
How much heat is developed at (the same) stall torque?
Ts = kT*N*Is so Is = Ts/(kT*N)
Pstall = R*Is^2 = kR*N^2*Ts^2 / (kT*N)^2 = kR*Ts^2 / kT^2
The power (heat) at stall is independent of N, varies with actual torque (squared).

Some more theory:
Let’s look at the other end of the envelope. Motors need some voltage above 0 to start in the first place because the (stall) torque needs to overcome the friction at rest.
Assume the required torque is Tx, same for all motors of same type.
Then we know that Tx = kT*N*Istart = kT*N*Vstart/R = (kT*N*Vstart) / (kR*N^2) = (kT*Vstart) / (kR*N) =>
=> Vstart = Tx*kR*N/kT
Vstart is thus proportional to N, so the relative difference between minimum speed and maximum speed stays roughly the same even if the low turn motor is run at a lower voltage.

Volt up, gear down?
Is there some merit to this advice?
Starting from the situation above, with the 17.5T motor fed 7.4V at 10.5% load (maximum rated current). The input is 125.8W and the output is 99.4W.
If we double the voltage while keeping the output power the same the load is reduced to 2.4% (by means of gearing down). Then the current drops from 17A to 10.9A but the input power increase to 161.0W, which means the heat generated is more than doubled!
Why doesn’t it help to volt up and gear down? Because the motor was running at peak efficiency. Gearing down reduced the efficiency and thus increased the power loss (read: heat).
A motor geared to operate at loads above peak efficiency will benefit from gearing down.
The current, which in itself might be the limiting factor, is reduced by using higher voltage while keeping the load constant.
Running RC cars one “issue” is that the load is far from constant. During hard acceleration and (typical for crawlers) when the wheels get stuck in tight spots there’s a very high load.

So to reduce current: Volt up, gear down!
To increase efficiency (reduce heat): Optimize the gearing and voltage, not necessarily by gearing down.

Other observations
The relationship between Is and Imax at a given voltage is much bigger for low turn motors. If we to that add that the heat generated is proportional to the difference squared it’s easy to understand that at high loads a low turn motor will heat up much faster than a low turn motor.

Heat as the limiting factor
How do we maximize the output power while keeping the generated heat at a constant level?
That’s done by maximizing the efficiency!
Ph + Pm = Pin * (1-E)

Theory and reasoning
We’ve seen that low turn motors provide the most efficiency for a given maximum load.
The “cost” for this efficiency comes in the form of a high current and a requirement for reduced voltage.
Low voltage makes it difficult to get a perfect match in the choice of battery.
High current at that low voltage makes the resistance in cables and ESC a concern.

What numbers are we talking about?
Say we want 50W continuous output from the 3.5T motor.
Using the optimum load at 5.7% we need a voltage of 1.40V (equivalent of a single, fully charged, NiMH cell) and the motor will draw 40.5A (56.7W).
The 17.5T motor also providing 50W at optimum load will require 5.29V, 12.1A (64.2W)
The difference in heat is thus considerable, with the 17.5T motor generating more than twice as much heat as the 3.5T motor. (14.2W vs 6.7W)
The difference is that at stall with these voltages is quite different though. The 3.5T motor will draw 933W and the 17.5T motor only 546W, so it’s almost the opposite.
Evaluating further we find that the low turn motors run faster at optimum load (and thus require lower gearing) than the high turn motors while providing the same power. That’s probably where the “higher Kv => less gearing” stem from.

A real life example:
Apart from my crawler I’m also running a drift car.
The typical setup for a drifter is:
2S battery.
9.5T motor (±1T)
Gearing close to 8:1
My setup is:
4S battery
17.5T motor (the TrackStar)
Gearing 4.25:1.
Reported power consumption with the typical setup is 60W (estimated for driving indoors on carpet).
Power consumption with my setup is 30W (measured while driving outdoor on asphalt).
Why does my setup use roughly half the power of the typical setup when my motor is supposed to be slightly less efficient?
There are a number potential flaws in the comparison:
One of the consumption levels is just an estimate by the driver, not actually measured.
The driving conditions are different. I have no idea which surface requires more power.
The cars and motors are different, but there if anything I think the “typical” car is better than mine, using a more expensive (efficient design?) motor and generally optimized chassis and suspension.
Driving style differs. I’m a rookie and the other driver is a seasoned veteran.
Can the sum of errors make up for all of the difference? I find it unlikely…
To me one really interesting factor is the difference in gearing. I decided to use the higher gearing based on the assumption that my motor has more torque, but in reality (based on the torque findings above) the difference should be negligible!
My motor should thus see a higher load and my car should behave quite differently than the typical.
I haven’t tried the typical setup, so I can’t comment on any differences, but I have no problems drifting with my setup! (And I rarely need to use more than 1/3 throttle doing it.)
Perhaps my motor is running closer to peak efficiency? But even then the difference should be much smaller. (And the “typical” setup adjusted to use a more efficient gearing.)
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Re: motor theorie en praktijk (huiswerk)

Bericht door Wouterb » 06 nov 2017 13:58

Conclusions
Creating this article has really rocked my world regarding motor properties!
Things that I took for granted have been proven wrong. There were many “eureka moments” along the way, mixed with dead ends and failures (in the model design process).
Do take note that everything below relates to the MOTOR only, unless otherwise explicitly expressed. What happens in ESC and battery is NOT examined!

Here’s a recap of what’s been found:
“When the number of winding turns go down the Kv goes up.”
That’s True!
“When the number of winding turns go down the output power goes up.”
That’s True! (With the voltage kept constant.)
“When the number of turn goes up, so does the torque.”
Wrong for constant voltage! (True for same current though.)
True also if you keep the output power the same and adjust gearing and voltage so that the motor operates near its maximum efficiency.
The maximum efficiency is at a higher load for high turn motors, and therefore it’s better to have them geared a little higher, not because “they have more torque”.
“When the number of turns go up, so does the efficiency.”
Wrong! If anything the efficiency goes down with more turns. (At least while the load is <50%.)
“Volt up, gear down!”
Good advice if the objective is to reduce the motor current. Not good for improving motor efficiency.
To increase efficiency you’re probably better off doing the opposite…

Further findings:
The no load current is a result of bearing (and other) friction and can therefore not be estimated without actual test data. It can be said that it’s higher for low turn motors though.
For a given torque the power loss due to wire resistance does NOT depend on the number of turns. Any difference in total power loss is due to difference in speed (for a fixed general design).

Based on these motor findings the general advice should be:
ALWAYS use very low turn motors. (The lower the better.)
Adjust voltage and gearing to fit the requirements for power and torque.
It’s obvious that these advice can’t be applied in practice though.

Some limiting factors are:
The ability of battery and ESC to handle large currents (and/or high switching speeds, in the case of BL motors).
The ability of ESC and other electronics to use a relatively low voltage (<2V) feed.
The motor being exposed to peak loads way above “optimum”. (Resulting in very high currents.)
Not many battery options for very low voltage.

How would this be implemented onto my crawler?
As mentioned I’ve been running the 17.5T motor on 4S in my LCC (a shafty with worm drives) for a while. I had some trouble with the low speed characteristics, but that might have been a timing issue.(*) Otherwise I felt the power and torque to be satisfying.
Adopting the findings above I should:
Switch to the 3.5T motor.
Use 1S LiPo.
Limit the ESC output to 82% (3.0V nominal).
Gearing could be reduced a little, but I was running it below optimum just to get the low speed behavior better so no change required.
What problems arise?
The ESC (standard MMP) can’t handle that low input voltage.
The Servo and Rx want higher voltage as well.
For the Rx I can use a voltage booster, but the servo will need a separate feed.
Finding a suitable sized 1S LiPo will be difficult.
Second option is to use 2S LiPo which will eliminate the problems above but require the ESC output to be limited to 41%. That might in turn provide problems in the ESC as well.
How much current will I need to handle?
At around optimum load there won’t be much difference in current, so that’s not a problem. However, the stall current at 3.0V is 1.4kA for the 3.5T motor, up from 0.3kA of the 17.5T motor. That might be a problem, not only for the MMP but also for the battery. Experience says that the full stall current won’t be used, but 1/3 of it is a reasonable maximum, so 475A from the ESC and 195A from the battery must be manageable.
At least HobbyKing doesn’t have a suitable (2S, ~1.5Ah, 130C peak discharge) battery in their assortment.
At the end there will need to be a compromise to find out a working combination of parts that actually exist …
… and since I’m now using a completely different motor it’s not an actual issue to start with!

Where do I go from here?
From the above findings and conclusions I realize that the next “black hole” in my knowledge is ESC performance.
How (in)efficient is an ESC depending on variations in current, voltage and (motor) frequencies?
I can make a few guesses, but they’re by no means “educated” guesses…
Unfortunately I don’t even know where to start looking for the type of knowledge needed, so anyone that can give me a nudge in the right direction is welcome to do so.
________________

(*) Lately I’ve found indications that the markings on the sensor timing ring are way off. The markings indicate that timing can be adjusted between 15 and 45 degrees (with 30 degrees being the default factory setting), so I set it to “15 degrees”. The real numbers might very well be -15 to +15 degrees, so I ran it at -15 degrees actual timing (if the indication is true).
'Crazy Janey' (zelfbouw chassis, lc70 hardbody)
Baja Cherokee (zelfbouw, Jeep Cherokee hardbody)
Ramrod (VS4-10, kit)
Rip-Off (zelfbouw chassis, Toyota SR5 lexan)

Arjan
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Re: motor theorie en praktijk (huiswerk)

Bericht door Arjan » 07 nov 2017 10:45

:o ken je dat samen vatten in 100 woorden in jip en janneke taal
"You can't treat a car like a human being - a car needs love" (WALTER ROHRL) 8-)

Mud monkey
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Re: motor theorie en praktijk (huiswerk)

Bericht door Mud monkey » 07 nov 2017 19:28

:doh: Vergeet de heleboel Arjan zo als wij rijden kan je het heel simpel houden
Met scalen rijden we gemiddeld met 35t tot 55t en gaan we niet tot het uiterste van motor en accu
Gewoon een hoge MAh en rijden tot ie leeg is nieuwe accu er in en rijden maar weer :dance:

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Wouterb
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Re: motor theorie en praktijk (huiswerk)

Bericht door Wouterb » 27 nov 2017 10:32

In filmformaat van de grote baas zelf:





:lol: "na elke rit je motor eruit, schoon spoelen en de lagertjes smeren."

Mag ik vingers zien?
Ik niet in ieder geval.
'Crazy Janey' (zelfbouw chassis, lc70 hardbody)
Baja Cherokee (zelfbouw, Jeep Cherokee hardbody)
Ramrod (VS4-10, kit)
Rip-Off (zelfbouw chassis, Toyota SR5 lexan)

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