Going twin brushless motor

[Rob Buckle]

All,

I'm fast becoming frustrated at having to substantially disassemble my Clod in order to replace worn brushes. Therefore, I figure that I may as well educate myself with regard to moving over to brushless motor/ESC technology while messing about with my Clod as it currently stands. With that in mind...

I'm looking to obtain speed at least as great as that from my Super Stock TZ motors, and ideally greater. If I understand correctly, on 7.2v I'd require brushless motors that deliver 26500 revs of TZs/7.2 volts = 3681kv minimum. The 'standard' (?) kv rating closest to, but greater than this is 4600kv, an increase of 25% - a significant percentage. Is this correct? Would anyone advise a motor of greater kv than this or is it likely to start breaking axles etc?

I appreciate I'll have to purchase 2 motor/ESC combo packages. One of the motors in the Clod runs in reverse. I think it's the case that an unsensored brushless motor can be made to run in reverse simply by reversing the positive and negative leads, but that a sensored brushless motor cannot be run in reverse - the reason presumably related to it being sensored. Is this correct?

If the above is correct than presumably I'm after sensorless motors, though I'm not keen on the idea of 'cogging' occurring, which I understand can sometimes occur at low speeds with sensorless motors. A long time ago I was perusing TWINSET's showroom and seen an 'outrunner' motor for the first time. Having looked into them a bit I'm really attracted to the thought of using them in my Clod. I've performed a forum search but the threads discussing this type of motor are several years old now, so the difficulty of fitting a pinion to, or getting adequate performance from, outrunner motors in non-plane R/C models may be a thing of the past for all I know. Can anyone enlighten me if it would be possible to fit outrunners to my Clod and if so, what modifications, if any, would be required?

If I'm missing anything obvious here please chip in!

Cheers,

Rob

[Percymon]

My first thoughts would be EZRun systems, but for a Clod i'd opt for one of their specs ending .5T to ensure getting the bigger 540 sized rotor. My EZRun 9T 4300kV system in the Hotshot is a 380 rotor size but still motors it along nicely; maybe two of these would be fine in the Clod, but two 8.5T systems would be better. Brushless unsensored uses three wires to the ESC, swap an two and the motor runs in reverse.

You could look at Hobbyking, as they have a euro warehouse so no import duty. They have Turnigy 4400kV motors pretty cheap, although you'd need two ca 50A ESCs to go with them

http://www.hobbyking.com/hobbyking/store/u...idProduct=14495

45A esc with reverse..

http://www.hobbyking.com/hobbyking/store/u...idProduct=13445

2 motors and 2 escs for £41 plus postage (although the ESCs are only available from the HK warehouse !)

I've got the same ESC powering a turnigy 3980kV brushless motor in my Gmade R1 and it doesn't cog, but can back flip the R1 easily from a standing start !

Unless you do a lot of jumps you're unlikely to have many issues with the axles, but the gearbox internals may have a shortened lifespan (albeit longer than a set of TZ brushes !)

[thorsteenster]

Castle Creations Mamba Sidewinders and 4600KV motors. The 4600kv's will have plenty of pep and are standard sized motors.

[Rob Buckle]

Brushless unsensored uses three wires to the ESC, swap an two and the motor runs in reverse.

I'd assumed that a third wire was required only for sensored motors and that it carried to the motor a repeat on/off state in order to turn it, but I guess not. What's the third wire for? Also, does this mean that sensored motors are an option? Are there any problems associated with using sensored motors for this application?

A question that came to me last night: What informs the decision between using a higher kv motor paired with 2S versus a lower kv motor paired with 3S?

[TA-Mark]

I'd assumed that a third wire was required only for sensored motors and that it carried to the motor a repeat on/off state in order to turn it, but I guess not. What's the third wire for? Also, does this mean that sensored motors are an option? Are there any problems associated with using sensored motors for this application?

All brushless use 3 wires to send the phase changes to the motor. Sensored systems have an extra sensor wire as well as the 3 main wires.

It is possible to use sensored brushless in a twin system setup. How you switch one system to run backwards is the difference. With a sensorless system it's achieved by swapping any 2 of the 3 motor wires. With a sensored system you MUST set the direction of rotation with the ESC setup. Wiring a sensored system any other way but the designated positions will make pretty blue smoke.

A question that came to me last night: What informs the decision between using a higher kv motor paired with 2S versus a lower kv motor paired with 3S?

One word... Heat!

Lower Kv, higher output motor with taller gearing works better. I would recommend the Sidewinder SCT 3800Kv system. The 3800Kv Y1410 motor is 4 pole (vs 3 pole of other motors) for almost double the torque and is 550 sized longer can than the CM36 motors. The MambaMax Pro SCT ESC with the same 3800Kv motor would be better of course. 2S2P (two 2S Li-Po packs in parallel) Li-Po for this setup is plenty of 'too much' for a 1:10 twin motor MT.

[Rob Buckle]

Hey TA-Mark,

It is possible to use sensored brushless in a twin system setup. How you switch one system to run backwards is the difference. With a sensorless system it's achieved by swapping any 2 of the 3 motor wires. With a sensored system you MUST set the direction of rotation with the ESC setup. Wiring a sensored system any other way but the designated positions will make pretty blue smoke.

Thanks very much for clarifying. Can you confirm if all sensored motors can be made to run in reverse by changing settings during setup of the ESC, or just certain manufacturers' offerings?

One word... Heat! Lower Kv, higher output motor with taller gearing works better.

I'm a bit confused by the above quote. Lower kv equates to lower output motor doesn't it? Also, by taller gearing, do you mean a greater number of teeth on the pinion (assuming we do not adjust the spur)? This would increase rpm at the expense of a reduction in torque, but wouldn't it generate more heat from a heavier load placed on the motor (trying to turn would be more difficult at speeds less than flat out wouldn't it?)?

I would recommend the Sidewinder SCT 3800Kv system.

In Castle's nomenclature, what does SCT refer to? I'm aware that SCT is an acronym for Short Course Track, but what does that mean? That the motors are only good for short runs?

The 3800Kv Y1410 motor is 4 pole (vs 3 pole of other motors) for almost double the torque and is 550 sized longer can than the CM36 motors.

Hmm, a 550 size can may be a problem, as I understand it clashes with the stock Clod's links, and may (?) with made up links.

The MambaMax Pro SCT ESC with the same 3800Kv motor would be better of course.

Why would it be better if the same motor was used?

2S2P (two 2S Li-Po packs in parallel) Li-Po for this setup is plenty of 'too much' for a 1:10 twin motor MT.

I could be wrong here, but I think I can get away with a single battery. I have a 5000mAh 45C LiPo. My understanding is that with 45C I will have no trouble delivering the high current drawn by the motors, and that while on the one hand the greater motor draw will reduce battery runtime, on the other hand the efficiency of brushless compared to brushed will reduce that penalty (not sure by how much though). At present I get around 20 to 25 minutes of run time, which I find more than enough. As long as I maintain, say, 15 to 20 minutes I think I'll be content - though don't quote me on it as I may want to run for longer when I see the Clod flying!

[TA-Mark]

Hey TA-Mark,

Thanks very much for clarifying. Can you confirm if all sensored motors can be made to run in reverse by changing settings during setup of the ESC, or just certain manufacturers' offerings?

It depends on what features the ESC offers. You would need to check carefully if reverse rotation is supported before outlaying money.

I'm a bit confused by the above quote. Lower kv equates to lower output motor doesn't it? Also, by taller gearing, do you mean a greater number of teeth on the pinion (assuming we do not adjust the spur)? This would increase rpm at the expense of a reduction in torque, but wouldn't it generate more heat from a heavier load placed on the motor (trying to turn would be more difficult at speeds less than flat out wouldn't it?)?

Lower Kv = lower RPM, not lower power. It's the same power in a different RPM range. Higher Kv motors naturally run hotter in any chassis. You can achieve the same performance with gearing from a lower Kv motor with taller gearing than a high Kv motor with short gearing and save on heat, which means the motor lasts longer.

In Castle's nomenclature, what does SCT refer to? I'm aware that SCT is an acronym for Short Course Track, but what does that mean? That the motors are only good for short runs?

It means 'Short Course Truck'. Specifically designed for those 'odd' sized 'giant' SCT's like a slash that is closer to 1:8 scale than 1:10 scale. Heavy vehicles with big wheels. The same system will also work well in true 1:10 Monster Trucks.

Hmm, a 550 size can may be a problem, as I understand it clashes with the stock Clod's links, and may (?) with made up links.

Brushless motor wires exit from the side of the can, not the end like a brushed motor. There is also no brushes hanging off the end of the motor. The length of the motor is generally shorter than a brushed motor + clearence for the wires. It needs 57.7mm to fit in. Measure on the Clod to see if this is too long. The larger magnets and winds would certainly be noticed in the performance.

Castle do have 540 can size motors with 4 poles aswell. The 1406 series which needs 49.5mm to fit.

Why would it be better if the same motor was used?

The MM SCT Pro is a higher Amp rated ESC than the Sidewinder SCT. It can handle more Amps and 1/3 more voltage. In high load (big wheels) situations you keep the ESC within it's limits much easier and ESC running temps are lower. The motor will run the same on either ESC.

I could be wrong here, but I think I can get away with a single battery. I have a 5000mAh 45C LiPo. My understanding is that with 45C I will have no trouble delivering the high current drawn by the motors, and that while on the one hand the greater motor draw will reduce battery runtime, on the other hand the efficiency of brushless compared to brushed will reduce that penalty (not sure by how much though). At present I get around 20 to 25 minutes of run time, which I find more than enough. As long as I maintain, say, 15 to 20 minutes I think I'll be content - though don't quote me on it as I may want to run for longer when I see the Clod flying!

A single 45C 5000mAh 2S would be fine. The higher power and efficiency means you don't need to pull the trigger as hard to get the same effect. If you drive in the exact same manner you will see longer runtimes... but who does that? You'd use that extra power to full effect and make your smile bigger which equates to similar runtimes to what you're getting now.

If you were using lower 'C' rated packs you would need to parallel two packs together.

[Rob Buckle]

Lower Kv = lower RPM, not lower power. It's the same power in a different RPM range.

So even though on paper I'd achieve less rpm than my TZs, I'd claw it back (and more) through changing the gear ratio, right? Does this not make it difficult to determine the speed/torque you'll obtain for a given motor/ESC combo...before you purchase? Presumably I'd need to buy an adjustable mount for each motor?

Higher Kv motors naturally run hotter in any chassis. You can achieve the same performance with gearing from a lower Kv motor with taller gearing than a high Kv motor with short gearing and save on heat, which means the motor lasts longer.

Okay, but I note that CC's 1410 series motors (see below) are able to handle 2S and 3S (assuming the ESC was man enough for 3S). Given identical gearing would it be better to run, for example, a 1410 series on 3S or a 1415 series on 2S, in terms of the health of the motor?

It needs 57.7mm to fit in.

It would be extremely tight with the stock links. I think it may well fit with home made links though, which is something I'll have in due course (don't ask me when!).

Castle do have 540 can size motors with 4 poles aswell. The 1406 series which needs 49.5mm to fit.

I think the 1410 series would also physically fit with a few millimeters to spare.

All,

From reading a range of threads on the forum it is clear that by far the most common brushless setups are EZrun and Castle. The former is obviously popular principally because of its modest price, though I gather that perfomance is good too. The latter is popular because of...what? I guess the fact that it is sensored means cogging is impossible, as opposed to possible and occurring/not occurring in some cases with EZrun. Is this the only difference? Are Castle products better performing? Longer lasting? I guess what I'm really asking is: where is your money going if you go with Castle as opposed to EZrun?

[thorsteenster]

Castle systems are not sensored, about the only company making sensored systems is Novak. The biggest difference from what I've found between sensored and non is start up power/smoothness being that a sensored motor senses what position the rotor is in.

My reason for going Castle doesn't work for you, I'd buy castle because they are based right here in the US, I can call them and they offer top notch support. I've never heard of EZrun, but my guess would be if they have a support number you'll need a translator, and God knows where you'd send a product back to.

Novaks are great too, I like them equally but the thing Castle has is PC prgrammability with a Castle Link, you can fine tune brushless settings, drag brake, start up power etc etc.

[TA-Mark]

Castle systems are all sensorless by definition. They do have a programming profile very different to other brands which uses the back EMF from the idle phase so the controller knows which direction and phase the controller should be sending to the motor. This almost removes all cogging from the system at low speeds, unlike some sensorless brands.

The difference between EZ-Run and Castle systems is the amp ratings. Castle don't make low Amp systems like EZ-Run. Castle's 35Amp ESC is for 1:18 scale...

As far as price goes, The only 2 systems you can directly compare is EZ-Run's 60A ESC and Castle's lowest spec Sidewinder system. The Castle is still a quite higher rating than the EZ-Run, and about $10 difference in price.

The other difference is the programming software. The Castle has infinite adjustment once connected via USB to a PC, where as the EZ-Run has pre-sets and its settings are still in large increments when using the program card.

I very much doubt you are getting the stated RPM from those TZ motors fitted in a Clod. They are for 1.5kg touring cars afterall. The Castle/Neu 1410 4 pole 3800Kv on 7.4v is ~28,000rpm. The TZ is ~26,000rpm. How did you get the TZ was a higher rpm? The smallest Castle/Neu 1406 4 pole motor is 4600Kv (~34,000rpm).

If the 1410 motor is too long at 57.7mm, the 1415 motor certainly will not fit. It's 69.5mm long.

[Rob Buckle]

Thorsteenster/TA-Mark,

Thanks for straightening out my erroneous assumptions and mistakes.

The Castle/Neu 1410 4 pole 3800Kv on 7.4v is ~28,000rpm. The TZ is ~26,000rpm. How did you get the TZ was a higher rpm?

Er, not sure what I was thinking. Sorry, you are of course correct.

If the 1410 motor is too long at 57.7mm, the 1415 motor certainly will not fit. It's 69.5mm long.

I'd been looking at the range of motors offered by Castle on their web site and again got confused when typing here - sorry! Yes, the 1415 series is definitely too long. The 1410 series, after measuring the gap again, may just fit, especially with, as you say, the wires coming out of the side of the motor. The 1406 series will definitely fit.

If I can ask another question without putting my foot in my mouth again, is it true to say that:

1. Without adjusting the gearing, the 1406 series 4600kv motor will return greater rpm than the 1410 series will with 3800kv, albeit the latter will have significantly greater torque than the former;

2. With adjustment to gearing only for the 1410 series 3800kv motor, greater rpm and the same or greater torque (even though it has been reduced through gearing) can be obtained than that from the 1406 series 4600kv motor;

If 2 above is correct, does that necessarily mean that at any given rpm for both the 1406 and 1410 series motor, the 1410 series motor will have greater torque than the 1406 series motor?

Additionally, how does one calculate the increase in rpm from substituting, say, the stock 13 tooth pinion for, say, a 15 tooth pinion?

[Rob Buckle]

All,

I'm getting thoroughly confused. Until recently I'd been under the impression that I'd see an increase in speed so long as the product of kv and v was at least equal to quoted rpm for my TZs. I now appreciate that, for certain motors with kv less than my TZ's rpm/v, I could change the gearing and still see an increase in speed (for the same torque as the TZs). However, in looking at HobbyKing's web site I came across this. This motor is 7900kv, which I would have assumed signified that it was very powerful, yet the motor looks pitiful. What am I missing?

What's the significance of amps? I gather the ESC has to be rated at least equal to the quoted amps for the motor, but is more amps good or bad? Does a greater value for amps signify a more powerful motor? Is the value for amps one I should take into account when making a purchase or is it of little or no significance? I find myself looking at outrunner motors but not having a clue if they are sufficently powerful as they are, or would be sufficently powerful if they were geared appropriately.

The overwhelming majority of outrunners have low kv ratings compared to brushless (inrunner) motors typically used in cars/trucks, but it is my understanding that a brushless outrunner has far greater torque than a brushless inrunner. If I am not mistaken, this implies that through gearing you can enjoy an increase in rpm even more so with an outrunner than an inrunner, albeit you start off with lower kv with the former compared to the latter. It also suggests to me that at 4400kv, torque for the outrunner suggested by Percymon would be insane (compared to a 4400kv inrunner). Am I mistaken?

I hope one or more members can help me understand by addressing the above.

Cheers

[TA-Mark]

Kv is simply an indication of how high the motor rpm will be per volt of electricity supplied. It's not an indication of power in any way. Power is rated in W (watts) which is rarely mentioned by manufacturers of vehicle systems.

[southy]

Here's a thread of a twin brushless clod.

http://www.tamiyaclub.com/forum/index.php?...=brushless+clod

[Rob Buckle]

Here's a thread of a twin brushless clod.

Thanks Southy. I'd read that thread previously. Unfortunately the problem with threads discssing this topic is that they generally state what someone has done and not why they did it. Answers to questions posed in my previous 2 posts would help me (and possibly others in future) understand the reason behind the choices we may make, rather than blindly purchasing something simply because "someone else used it and it worked".

[Rob Buckle]

All,

Can this be used to connect 2 ESCs to a single battery? Not sure if the limitation on amps is a problem or not.

[thorsteenster]

All,

Can this be used to connect 2 ESCs to a single battery? Not sure if the limitation on amps is a problem or not.

Yup, should work a treat, no worries with Deans. Too you could use a Y cable if you're buying stuff locally add 2 sets of M/F Deans and a package of good wire.

[kaiser]

Thanks Southy. I'd read that thread previously. Unfortunately the problem with threads discssing this topic is that they generally state what someone has done and not why they did it. Answers to questions posed in my previous 2 posts would help me (and possibly others in future) understand the reason behind the choices we may make, rather than blindly purchasing something simply because "someone else used it and it worked".

thats my truck in that thread.

ask away. it was easy and the truck flies!

i used the 60amp 8.5t versions because they are efficient. temps are very low and runtimes are long. it was very easy to do as well.

[Rob Buckle]

Kaiser,

...ask away.

You may come to wish you'd never typed that! Seriously, thank you for your offer. I genuinely appreciate the help I receive in threads I start, but I also feel strongly that it is better to make an infomed purchase than to purchase solely on the recommendation of another - even though I have little or no doubt that such a recommendation would work. I hope my line of thinking does not offend anyone.

Questions:

1. How does one calculate the increase in rpm from substituting, say, the stock Clod 13 tooth pinion for, say, a 15 tooth pinion?

2. You used two 60 amp motors. Does that mean the ESC needs to be able to handle 2*60=120 amps? Continuously?

3. Does temperature typically increase with a corresponding increase in amps, or does it decrease?

4. Given the text content in the link in my previous post for the y-adapter, would 60amp motors not be a problem, and if not, why?

Cheers,

Rob

[TA-Mark]

2. You used two 60 amp motors. Does that mean the ESC needs to be able to handle 2*60=120 amps? Continuously?

Brushless MUST have a controller for each motor. One controller cannot possibly control two brushless motors at the same time. I think you will find it is 2x 60A combo systems running in parallel.

The more Amperage the ESC can handle, the 'safer' the system will run without causing problems. Load on the motor increases the amount of Amps they will ask from the controller. Acceleration uses alot more than maintaining the same speed for example, just as a heavy vehicle with big wheels will see the motor want more Amps from the controller. Motors aren't rated in Amps as I previously stated. A motor will draw as many Amps as it requires within the limits of the controller. Motors are rated for rpm per volt (Kv) and power output in Watts (W). An ESC that is running at it's limits constantly will not last long just the same as any electrical device.

To work out the difference in speed between 2 different size pinions you need to know the FDR (final drive ratio) of the vehicle, and also take into consideration the diameter of the wheels used (a little maths will work it out). Different sized pinion will also change the load on the motors, smaller pinions being less load, which also means less current draw, and less top speed. However, gearing that is too short will have the motors running at near peak rpm all the time which will also cause heat issues in the motors. You will find that gearing is trial and error as you 'break new ground' with systems that have not been tried in this chassis before.

Battery and ESC temperatures are the biggest concern when there is high load on the system. The battery must be able to supply the controller with how much Amps the motor is asking for. Overheat a Li-Po and it will swell. Overheat the ESC and it will thermal shutdown or worse. Again trial and error to get the gearing and load right for the Kv of motor you choose.

[Rob Buckle]

Many thanks TA-Mark, I think all but one of my four question has been answered.

With regard to the y-adapter to allow connecting 2 ESCs (sorry for forgetting I'd require 2 ESCs in my previous post - I did know this) to 1 battery:

1. If each ESC was rated for 60 amps minimum then the ESCs would be safe;

2. The draw on the battery would be 2*60=120 amps. If my 5000mAh 45C LiPo can handle 5*45=225 amps continuous then that is okay;

However, wouldn't the y-adapter fail (melt?) with, potentially, 120 amps passing through it (remember the link says 2*30 amp max)?

[kaiser]

Kaiser,

You may come to wish you'd never typed that! Seriously, thank you for your offer. I genuinely appreciate the help I receive in threads I start, but I also feel strongly that it is better to make an infomed purchase than to purchase solely on the recommendation of another - even though I have little or no doubt that such a recommendation would work. I hope my line of thinking does not offend anyone.

Questions:

1. How does one calculate the increase in rpm from substituting, say, the stock Clod 13 tooth pinion for, say, a 15 tooth pinion? i run 2 15tooth, it increases top end. i don't know the math though. lol don't need to know the math because temps are good.

2. You used two 60 amp motors. Does that mean the ESC needs to be able to handle 2*60=120 amps? Continuously? you need 2 brushless esc's to run 2 bl motors

3. Does temperature typically increase with a corresponding increase in amps, or does it decrease? my temps have been cool, thats all i know.

4. Given the text content in the link in my previous post for the y-adapter, would 60amp motors not be a problem, and if not, why? i clipped the red wire off one of the legs of the y adaptor, otherwise you over power the receiver. the motors aren't 60amp, the esc's are capable of 60amp continous discharge....or sumptin like that.

Cheers,

Rob

answers in quote.

i think you are overthinking the whole thing to be honest. i almost went with the "good ole 9t / 35amp combo" but spent the extra $$ on the 60's for peice of mind and efficency.

[kaiser]

for batts i have a few different ones that i use.

none of them have overheated or been stressed. all of them are 30c or more. of course the 50c 5000mah has the most punch and is the pack i race with.

[TA-Mark]

How often do you think it would draw a constant 60Amps from the battery? Only if you were doing something silly with the Clod I'd think (towing a 1:1 car through sand maybe ). Under normal use it'd burst high current on take off, then drop away as the speed increased to very little current draw once at speed.

It's something you would keep a check on the same as the battery, ESCs and motors in the first few runs to make sure everything is working happily together.

[kaiser]

you're right. you'll only see high amps at take off, aka a spike.

the other reason to go for the 60's / 8.5t's is the full 540size rotor = mucho torque over the 380's.