Timing advance and gearing as BL tuning tools:
Let's look at each seperately, and then how they would work together.
Timing advance:
Advance in a brushless motor works on the same principles as it does on a brushed motor, and also very similar to a combustion engine. That is: when you advance the timing up from zero on a brushed motor, it does several things UP TO A POINT OF DIMINISHING RETURNS:
1) Raising the advance raises the Kv of the motor.
2) Raising the advance in some cases can make the motor feel punchier
3) Raising the advance generally increases motor temps
But as above - the first two of those three things will only increase up to a certain point, and beyond that point, the Kv can actually go DOWN, and the punch can go down as well with excess advance. Motor heat will generally go up in small increments up to that same point, and the next setting up can show GREATLY increased motor temps.
Timing advance is a dynamic thing, meaning there will always be an "ideal" setting to get the best mix of rpm and torque relative to motor heat, but that "ideal" figure is different for each motor, track layout, surface, vehicle, and gearing. It's even different for each state the motor is in while you're driving - as in hard acceleration out of a hairpin to a straight, slow throttle ramp up out of a sweeper to a straight, and medium/low throttle modulation through chicanes and S curves. So essentially, any time you're changing the throttle position on your Tx, the "best" advance level for the motor changes as well.
So how do you "tune" the advance to get the most from your motor? You use two main parameters and one minor one in race conditions:
1) Motor heat
Heat is caused by the efficiency level of the motor, as in - 200 watts of electrical power are going into the motor from the battery and throught the ESC, and 150 watts of power are being transfered as physical work onto the spur gear of the car. 50 watts of power are being lost due to the efficiency level of the motor. (which the tech heads will instantly recognize that this example motor is running at 75% efficiency) Those 50 watts lost are created/expelled by the motor as heat. So the lower the efficiency level of the motor (more heat/less work) the more heat it creates and the hotter it gets.
Increasing the timing from a starting point of zero can in some cases (explained more fully below) INCREASE the overall efficiency of the motor, and cause it to be cooler at the end of the run. But generally, you'll see increased temps with each notch higher advance level. What you want to look for here, is relatively small increases as you go up, and then that next setting that causes a DRASTIC temp increase. This is your "point of diminishing returns" for that particular motor/gearing/car/track/driving style/traction situation. Generally it's best to run one (high level competition) or two (club racing) settings below this point as an optimal place for the motor with a little safety factor.
2) Motor "feel"
Upping the timing from zero, you'll also notice the motor feels more punchy, and has a touch more speed (with the GT ESC, it's about 1/4 to 1/2 a 64p pinion tooth per setting speed difference) than the last lower setting. The same process as above will reveal for each motor/gearing/car/track/driving style/traction situation a certain point at which the motor will actually be slower and less punchy than the next lower advance setting. Generally you'll find that the "point of diminishing returns" as far as track feel goes, will match up fairly close to the excessive temperature difference point.
3) Battery capability
This is a minor point compared to the first two, but in some situations (mod) it can make a BIG difference on the track. Increasing timing advance generally increases the apm draw of the motor. This in turn increases the load on the battery. The higher the amp load, the lower the battery voltage goes, and the lower the voltage the slower the motor is. I've seen many occasions with NiMH packs and even a few with lesser Lipo packs that upping the timing advance doesn't change the motor temps much, but the punch suddenly goes WAY down. What's happening here is that the motor is simply asking for more current than the battery can provide, and the voltage is dipping WAY down under heavy acceleration loads. Again, a minor point but worth mentioning.
Very rarely do broad generalities work for electric systems, but here are some basic guidelines in real-world settings to go by:
1) Generally the faster the motor (lower turns, Higher Kv) the LESS timing advance it will tolerate before getting to it's "point of diminishing returns".
2) Generally the slower the motor (higher turns, lower Kv) the more it "likes" and responds well to higher levels of advance.
3) Generally the longer and more open or "sweepy" the track is, more advance can be used.
4) Generally the shorter and tighter the track is, less advance is better.
So as real world examples - If we're running a tight technical track with a mod motor, generally plan to use very low advance settings. For a long sweepy track with a 13.5 motor, generally plan to use higher advance settings.
BL Gearing:
This one is much easier than timing advance!
The faster you gear a BL motor, the hotter it will get - period.
For club racing, try to match what others are doing and check your temps after race condition practice runs. Generally you'll find the same "point of diminishing returns" where going up one more tooth drastically increases your motor temps. Same deal as timing here - back off a tooth or two for a safety factor and then start fine tuning from there.
BL motors are interesting machines. For mod motors, you generally have so much torque in excess that you can't "gear it out" like a brushed motor to soften the low end response. In these cases, it's best to use "feel" as well as motor temps to find the optimal gearing for the track and conditions. The faster the gear, the faster the car will be on the straight, and the "jumpier" it'll feel in the infield (presuming top level batteries). Mod motor driving is all about what you can hang onto, react fast enough for, and train your trigger finger to deal with! Gearing here goes hand-in-hand with motor selection really. If you're running too hot and still want more speed - then you need another turn lower motor. If you're geared down as far as you can go and you're still having trouble staying ahead of the car - you need the next higher turn motor.
Stock motors are a little different however. Generally most racers can handle the tippy-top performing speeds of a 13.5 on most tracks pretty easily, and finding that pinnacle of performance can take some work. On the gearing side, start with temps as your guide and find the point where one more tooth makes a large difference in temps and/or is approaching the danger zone. Depending on the track, this line can be vey broad or extremely narrow. I race 13.5 TC as my primary class and I've found some interesting things about them. Try backing down 3-6 pinion teeth from the excessive temp point, and you'll likely find you're visibly faster on the straight and have more punch in the infield. A lot of this has to do with the fact that these motors are purposely NOT the super powerful "killer torque" brushless monsters their lower turn brothers can be. 13.5 motors are all about finesse, and not so much brutal horsepower. Much like brushed motors, you CAN dial out a bit of torque by going up a few teeth as long as your temps stay managable. If you find yourself running on the hot side and not keeping up with the pack - gear a few teeth "slower" and I'll bet your lap times and straight speed will both improve.
The 10.5s are a different animal as well. They basically fall in between the "finesse" of a 13.5, and the brutal horsepower of a mod motor. How you gear them depends completely on the track layout and traction conditions, and thus relies equally on your expected feel, and optimizing the motor performance. The general rules still apply though - find the breaking point in the motor temps, and then step down a tooth or two for a baseline of fine tuning. On asphalt, traction is king ruler and generally the punch is in excess, so going down a few more teeth from the baseline especially on smaller/tighter tracks can improve lines and lap times significantly. On the rug however, 10.5s can be finnicky on the mix between punch and speed, so race condition practice and top performing batteries are a must to fine tune a gearing balance.
So much like advance, motor gearing depends on the motor itself, track size, track layout, traction conditions, and your driving style/capabilities
Putting the two together - Gearing and timing advance combination tuning:
The most important point here is the fact that you need to use gearing alone to get you to 95% of where you want/need to be on the track as far as basic speed, punch and lap times. Gearing has a far more important role in the overall performance of the motor as the timing advance does. So look at gearing like the "basic chassis setup", and timing advance as "tuning for the track conditions of the day".
As pointed out independently above, mod, 10.5 and 13.5 all react differently to gearing and advance, so we'll look at them seperately here:
For mod motors, gearing is almost everything and timing advance plays an extremely small role. Gear to what you can hang onto, adjust motor turns or rotors to keep temps in check, and keep advance to as low as possible to help keep the motor efficiency up. (lower turn motor = generally lower advance in order to raise efficiency)
For 13.5 (or higher) stock motors, find the excessive temp point for the track via gearing, and back off 3-6 pinion teeth (~3 teeth for 48p, and ~6 teeth for 64) to put the motor in the low/middle of it's powerband, and then adjust the timing and gearing interchangably from there to find the optimal power point for the conditions. The proper gearing/advance mix can be critical to find that last 5% of performance. The optimal range I like to find is where I can go up a tooth or two in pinion AND down an advance setting and see a softer infield throttle response but the same good motor temps, OR go down a pinion tooth or two and up an advance setting to see a punchier infield response with the same good motor temps, and same top speed on the straight. That tells me I'm operating in the best efficiency range of the motor, and still have room to tune for the changing conditions of the day.
10.5s again totally depend on the track and traction conditions, but generally give you a larger "target zone" as far as the interplay between gearing and advance than the 13.5 and mod motors do. Lots of race condition practice may be required to find the target zone where individual deviations can then be looked at via lap times and feel.
About wires
Resitance from wire comes from three qualities:
1) Strand count
The more (and thus the smaller) individual strands in the wire, the less resistance it has. Electricity likes to travel on the wire surface, so lots of tiny strands = lots of surface area and happy electrons
2) Wire Guage
The bigger the wire, generally the less resistance it has. Potentially a no-brainer here but see below:
3) Length
The longer the run, the more resistance.
So obviously the higher the strand count, shorter the run and thicker the wire, the better off you are.
In order to save weight without sacrificing performance, consider overall length FIRST. Cutting an inch off all the lengths is a far better option than going down in size if it's available to you.
Wire guage and strand count work hand in hand, so be careful here. Cheap 12Ga wire can have MORE resistance than really good 16Ga wire! What you want to look for in good wire is it's "floppyness". They don't call it Deans "wet noodle" wire for no reason - it's floppy like a wet noodle and thus one of the best wires you can find.
14Ga on a 13.5 as long as it's high quality high strand count (floppy) wire is no problem. If it's stiff and "bendy", then it's not so great.
Generally I'm not comfortable with even the VERY BEST 16Ga wire on a car BL system unless it's a 17.5 on asphalt. So consider my personal recomendation that high quality 14Ga is the minimum for 13.5s on any surface.
An interesting compromise point is on the motor wires. Going down to very good 16Ga on the motor wires if you really really have to, won't hurt you too much. The most you'll feel is slightly less punch, and especially on asphalt w/BL - that's not such a bad deal.
What you NEVER want to do is sacrifice wire Ga and quality on the battery to ESC wires. Poor wire/too small/too long here can cause excessive ESC heat, blown caps, and ultimately blown ESCs.
Caps (kondensaatorid):
All ESCs work as simple on and off switches. The "switch" is being thrown electronically, and thousands of times per second, but it still always comes down to one of two states for an ESC - either "on" at full power, or "off" at no power. The battery voltage (regardless of cell count/type) depresses under the full power pulses, and rebounds (over the actual pack voltage) during the off pulses. ESCs aren't built to handle such a wide variance in input (battery) votage, and if left unchecked (no cap) it just plays havoc with everything the ESC is trying to do.
What the cap is there for, (and what they are/do by definition) is to store up voltage from the battery on each off pulse, and then give up voltage to the ESC on each on pulse. So the ESC sees a much "smoother" supply voltage from the battery without very large voltage depressions and spikes going on all the time. Net result = Happy, accurate and cool ESC operation.
The better the battery (lower internal resistance) and the less load (higher turn motor, slower gear ratio) in the system, then the voltage swings are smaller true, but even with the best battery and slowest motor you STILL want that cap there to keep things happy and smooth.
As above - capacitance makes a HUGE difference in ESC heat and operational accuracy. the bigger, and better quality it is, the cooler and safer your ESC is. Is it necessary? If you're running mod on tired old cells it absolutely is (better batteries and lower speed makes for less work on the capacitor). If you're running top shelf Lipos with a 17.5 on asphalt, then you'd be just as safe with about half the cap capability.
Motors and advance:
The lower the turn of motor, the LESS tolerance to excessive timing advance it has. The higher the turn, the more (to a degree) it LIKES high levels of advance.
A 13.5t on setting 6 or 7 is a happy motor. On 8 or 9, it can turn unhappy very fast.
A 2.5 motor on the other hand is very happy at setting 1,2 or 3 (depending on conditions) but is very unlikely to be happy at setting 5 and above.
So remember: LOW turn, LOW timing. High turn, High(er) timing.
Theoretically, the advance you run on the ESC PLUS the advance set on the motor will give you the total timing advance given to the motor.
Example: Motor is set to 5deg, and ESC set to 13.75 = 18.75deg of timing, OR the same as 18.75 on the ESC and 0deg on the motor.
Generally in brushless, it's best to let the ESC do EVERYTHING, and treat the motor as a "dumb" unit in the system.
And by everything, I really mean everything!
Drag brake - on the ESC not on the radio
Throttle/punch softening - on the ESC (or your trigger finger) not on the radio
Timing advance - on the ESC not on the motor
Full speed limiting - with GEARING, not on the radio EPA
Various information:
Generally as the turns go down in a motor, the overall power (watts) goes up, the kv (speed at the same gearing) goes up, and the thickness of the winding wires goes up as well.
Thicker winding wires = more power capability. Less turns of wire = faster motor.
All motors (brushed or brushless) have more power capability when the windings "fill" as much as possible. So it becomes a finesse game of thicker single wires vs smaller multiple wires in order to get the best "fill" for the speed and power capability target you're looking for.
No need to change the timing on the motor if you don't have that capability.
Super extra capacitance would help in a couple of "outside the norm" circumstances: If you're running old tired NiMH packs and gearing to keep up with new killer cells, the low turn brushless motors can come close to "browning out" the Rx in some particular cases with some radio gear. Also low battery capability (also seen as very hot packs with cool motors and a hot ESC) can be made up for on the ESC with more caps. The cap is there to smooth the voltage spikes from the battery, and the more overworked the battery is, the hotter it'll get, and it can make the ESC/cap hot as well from the same spikes. Additional caps can help cool the ESC (doesn't help the batts themselves) in a case of working the batts too hard.
Hybrid?!?
2. The BL world really is buzzing about your hybrid technology. In theory, it seems to be the next step in BL technology. Can you explain to the average driver what this is, how it works, and what the advantage is here?
Before the GT ESC, ESCs have been locked into one or another mode of operation, andeach has some distinct advantages and disadvantages: Sensored operation (using sensor wires and a Hall effect sensor in the motor) essentially slaves the ESC into the motors sensor array for information as to where the rotor is, and how to make it do exactly what the driver is commanding.Sensored operation has always exclusively given the user beautiful and accurate control over the motor regardless of its directional and/or power state. Starting from zero rpm, wanting to go forward from a state of rolling backward, feathering the throttle through a sweeper - its all done accurately and smoothly. However, one of the areas it falls short on is with timing advance for the motor. Since its taking direction completely from the sensor array, its locked in to the advance level that the physical array is currently positioned in. There are no timing advance tuning options available from the ESC at all, and in most cases no easily attained options on the motor itself either. Sensored brushless systems have been available in the hobby for decades now and because of their directional and start from zero rpm consistency and reliability they have become the accepted standard among racers.
Sensorless operation uses only the three main motor power wires, and a whole lot of sophisticated software within the ESC in order to determine not only the motors rotor position, but its current state and then how to deal with it in order to make it do what the driver commands of it. The accuracy and observed smoothness of a sensorless system from a state of zero rpm, rolling backwards or feathering through a sweeper tends to depend entirely upon the motor itself. Generally when paired with a sensorless motor, the best ESCs can manage almost acceptable performance for most racers. In a bashing environment, the minor eccentricities and brief periods of ESC confusion and/or delay are easily overlooked by the sheer power and speeds these systems are typically capable of. When paired with sensor based race legal motors however, sensorless ESCs historically have shown a severe lack of accuracy and smoothness very few racers can accept. Once the motor is under way however, the sensorless design shows its real strengths. Unencumbered by a sensor array to slave it to the motor, the ESC is free to be able to alter timing advance at will, as well as use the actual and more accurate millisecond by millisecond electronic feedback from the motor itself in order to drive it with top efficiency (most power at less current). So instead of relying on a fixed physical sensor unit to only know where the rotor is at a particulartime in order to drive the motor, the sensorless ESC can know not only where the rotor is, but under what torque state its in, what its been doing recently, what timing advance is best for its current state, and a host of other useful information that a sensor based ESC by definition just cant know about the motor.
So what if you could have the best of both worlds? All the accuracy and smoothness of a race legal sensored system, PLUS the running efficiency and advanced tuning options of sensorless? Well theres no need to dream, because thats EXACTLY what the Speed Passion GT ESC gives you. While the sensor based designers are lockedin to their Hall sensors, and the admittedly genius sensorless software designers remain directionally confused, The Speed Passion GT has it all, and has it RIGHT NOW.
Sensored control and accuracy when its needed, and sensorless efficiency once things are smoothly moving in the correct direction is the reality of Hybrid Drive. Top level racers have already discovered they can get more power and speed from ANY brand of sensored motor with the GT ESC. Its a true competitive advantage on any track, and this is only one of the many things Im so excited about with this ESC!
Originaal, kust tähtsama info siia kokku korjasin: RCTech foorum, Shawn Palmer, Schumacher USA
FR
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