73

I'm expecting a new test unit of 4 pole brushless 550 motor (36mm x 60mm) for the Hyper 10SC, so does anyone know whether a 4 pole needs some different gearing to a 2 pole motor?

Currently the truck is happy with a 2 pole 2700kv 1000watts 550 motor, running on 17T pinion gear. The new motor will be 4 pole, 1000watts and 3600kv. I'm thinking of having a 15T pinion for this one, to try to get slightly more (or equal) power than the present 2 pole setup.

Any thoughts are welcome. [8D]

Slo-V Flyer

2-pole or 4-pole, the Kv rating still gives you rough what kind of torque the motor will exert per amp (Kt rating) (all efficiency rating aside, which is a handful of percentage points in this case).

As you said your old one is a 2700 Kv, the new one is 3600 Kv so that is almost 40% faster, but also has less torque per amp. Technical mumbo jumbo aside, given the 4-pole is slightly more efficient anyway, I'd try a 13t pinion and go up to 15t if the motor/esc and everything else stay fine heat wise. Always a good idea to start from a safe point then go upward/downward.

73

Thank you for the insight!
I have to admit that even with those minimal technical breakdown, it's already giving my brain a good workout. [X(] Takes a mountain bike/MX guy some time to understand electrical systems.

OK, I'll start with smaller pinion gear and work it up from there.

Just for discussion sake,
there was this impression I got from reading on-line postings that 4 pole motor has more torque than a 2 pole, while a 2 pole will rev out to higher rpm better. This has me comparing the 2 pole power output to something like a 2 stroke engine, and the 4 pole to a 4 stroke. If so, then perhaps a 4 pole doesn't like high rpm, and a 2 pole is "softer" in comparison coming out of corners.
Or am I completely out of line?

HJJFFFAA

Don't want to start too small. It is possible to be undergeared and that will cause your system to heat up, as well.

Slo-V Flyer

I am not sure about the RPM limits of two similar sized brushless motors when comparing a 2 pole to a 4 pole. However I understand what you're saying. I do know that an ESC has to work twice as hard (twice as many times it has to switch the coils polarity etc) to make a 4 pole turn over as compared to a 2 pole. As such, you may find some ESC rate the max RPM it can handle for a 2-pole motor and a 4-pole etc and you'll notice the #s for the higher pole motors drop proportionally each time.

And yes, a 4-pole will have a smoother power curve, and possibly better bottom end torque, while the 2 polers will generally be more "rougher" at lower speeds and sometimes lower efficiency (not always), and should get more RPM I would think.

73

That's true too, under-gearing also cause overheating. Base on the 2700kv motor with 17T pinion, I'm guessing a 13, 14T pinion will be quite close on the new motor.
To get a clearer picture, when do we know a motor is over or under geared? Let's say we do physical field runs instead of punching numbers on the calculator (drive ratio, roll out, etc.).

If I cruise around for a few minutes without full throttle and the motor heats up, does that mean it's over-geared?
If cruising doesn't heat up the motor but overheating occurs during normal race runs with occasional full throttle, means the motor is under-geared?

73

The new 4 pole came in and I've managed to do a amateur test today. It's not a good comparison since the 2 pole is 2700kv and this 4 pole is 3800kv, but have to make do here.

With a 14T pinion on the 4 pole, the temperature is below 60 degree C, a little cooler than the 2 pole running 17T pinion. Instead, it is the ESC that ran slightly hotter when on the 4 pole motor.
Right now the powerband is quite close to my liking, with good torque out of corners and just enough speed to handle the straights.
But run time for the 4 pole is almost 3 mins less at 11mins, was actually hoping for the 4 pole's efficiency to give me more run-time. Might try a 13T pinion and play around with the programmable ESC to get back some top end speed.

Something that I'm not completely certain is, the 4 pole seems to sound more comfortable holding full rpm. On a 2 pole, we will know when the motor rev out as it kind of tells us it's "out of breath". But this 4 pole, at the max rpm it seems to simply stay humming along with less complain. Well, maybe the fact that this 4 pole is made for RC boats...

This is only the initial test, so more consistent results may come in after a few more runs over the weekend.

Slo-V Flyer

Interesting observation. usually if the ESC is overheating, that means that you may possible be over amping it, though you have geared down, so it can also be a myriad of reasons that I don't want to bombard you with. As for the reduced runtime, yes you theory on efficiency is correct but don't forget the 4-pole is much more faster rpm so a 3 minute penalty is not bad.

I'd gear UP a couple of teeth and run that motor a few minutes and compare the results. You may be surprised, the motor might run cooler, the ESC might run cooler, OR both might run hotter.

I know that when running mid throttle a lot, an ESC tends to get hotter than the motor, and at WOT (with proper motor gearing) the ESC will run a bit cooler.

73

Slowly but steadily, I'm learning about this amp rating thing on ESCs. The one I run is a 60A, most likely constant. It is meant for 540 sized motor and easily supports up to 4000kv motors in offroad applications.

A quick session today came back with more pleasant results.
Being a 4 pole, it has more off-power drag than a 2 pole motor. This mirrors a brushed motor effect, which helps with driving as far as I'm concerned. Nice.
Went for some quick laps with a full speed straight on loose surface, and once again got only 11mins.
So tried another pack running some technical laps, hardly reaching full speed, and came back with 13mins! I'm just glad the system behaved as such, instead of giving me more questions than answers.

Also nice to find that so far, the motor has never gone beyond 60 *C (140*F), the ESC stays below 60 *C too, while the soft case lipo consistently max out at 42*C.
You're right, 11mins is not bad actually. Maybe I was jealous that my buddies that run Novak 4.5T Ballastics (550) are having almost 14, 15mins run time. [X(]

I can try out bigger pinions, but a guess would be less run time and too much speed?
Presently the power and speed of this Leopard Hobby motor is sufficient for my applications, so I may stay with the 14T pinion or go to a 13T. Tracks here are not that huge so I'll try to be practical, don't feel need to gear it to the moon and give up run time. [8D]

Slo-V Flyer

Nice to see some results you like. As for the suggestion to gear up, that was merely to test the temps and see how the ESC and motor respond. Sure, you may probably get lesser runtime, but just testing a few minutes won't hurt. I forgot the motor's brand you mentioned. As it is 4-pole, it can be more efficient, but (and I'm not saying you get what you pay for always) I have no experience with the Leopard motors (I have seen them online though) or feedback about their efficiency. I know the usual suspects for efficiency cost a bit over $100-$250 like Neu, Neu-Castle, Lehner, and even Medusa to a degree, they do run cooler and hence better performance/efficiency, and can be geared up a bit more due to that (to squeeze the extra bit of power that way as needed).

As for the brushed motor like effect, yes, I noticed that right away with certain motors, including 2-pole ones, it depends on the rotor's magnetic strength from what I gather (and the stator). I have some motors that free spin almost freely, and others (My Novak 3.5R with sintered rotor, and Medusa 3300) that click or "cog" when you turn them by hand/coast more obviously. Some prefer that as it "feels" familiar to brushed motors, others prefer the extra free wheeling of the less clicky motors.

Keep the lipo below < 120*F for best life and performance in the long run. I am too lazy to convert 42*C to degrees F.

73

Thanks for the reminder. 120*F is just about 49*C so I'm not too close to killing the batteries. They're 5000mah and have 40C discharge rate, but anything less has shown signs of stress in the truck.

As for trying out other pinion sizes, I plan to go smaller first. Then if I do get curious, may go bigger just to see what happens.

I agree that most time we get what we pay for.
Case in point is the Novak system my buddies run. They cost more but the motor runs cool, fast and longer. Then there are the cheaper tires, and the genuine Pro Lines. Also, the Deans connector and the knock-offs, etc.
I was prepared to get less from going with this cheaper China option, as long as it work nice enough and doesn't blow itself up too quickly. In this case it was easy for me since I'm not looking for speed to beat my buddies, but just enough motor to hang with them and have fun. This may not be the better 4 pole motor, still it satisfied my joy of testing stuffs, and I'm pretty happy with it actually.
Some China products these days are more stable than yester-year's "gamble purchases." We've so far have good value and lifespan from their brushless motors, ESCs, Lipo and even 2.4G transmitters.

Now that you mention it, the drag of the rotor may not be the norm for all 4 pole motor then. I recalled having some brushed motors with stronger magnets, and others with weaker ones. The stronger ones usually have nice torque, if I'm not wrong.

genitor

Can you post a link to that motor?

Slo-V Flyer

Yah if you read my signature, I'm running 2 Feigao motors (cheap at $60-$80), the Mamba Max is no more. And recently a Medusa motor (after 2 years of Feigao) which used to retail for $100+. Just like you, I wanted to break into brushless 3 years ago, and just get the better power compared to my old brushed crap.

After my Mamba Max burned up /shorted (whoooops) I run a cheapy XE-run 80A and another off-brand 60A esc and they work fine for what I paid (their lipo voltage cut offs are funky though). So yah nothing wrong with getting proven Chinese stuff.

73

This is the motor I'm testing now, it's the 3800kv unit.
[link=http://www.leopardhobby.com/product/product_veiws.asp?id=1258&functionID=01020203]Leopard 3660[/link]
I like that it is almost as light as a 540 motor, and built simply, with no bells and whistle to complicate things. There could be similar motors in places like Hobbyking, although I have not really checked as I got it from my LHS.

This motor is about nice for my Hobbywing Xe-run 60A version2 ESC. With the ESC temp hovering around 55*C (131*F) now, I'm not eager to run a hotter motor with it.
The nice thing about this China ESC other than the lipo cut-off, is the upgrade software and programming versatility. Our experience with these ESC shows that it's almost always better to flash the software after purchase, especially when brand new. No harm anyway as it's free of charge.