Is 205°F too hot for a TrailMaster Sport?

[fyrstormer]

Just kidding, I already know the answer.

I recently bought a TRX-6, and I wanted to get it up and running without spending any extra money on it, so I swapped the stock motor (which I plan to sell) for a TrailMaster Sport 550 21T that I had in one of my many spare-parts boxes. I have my TRX-6 geared pretty high, 20/39, same as my TRX-4, so I can run it on 2S and still get 14mph in second gear. (or at least, the TRX-4 can go that fast -- not sure about the TRX-6 yet.) I took it out for a drive tonight -- nothing serious, just up and down some curbs and through some grass and over a drainage trench filled with canteloupe-sized rocks, plus a couple "speed runs" to see how the TRX-6 handled on flat ground. I ran the battery down from full-charge to storage-charge, so...about 65-70% of the total charge, I guess?...and when I got back to my house I noticed that distinctive smell of overheated wiring.

I expected the motor to be hot, but I didn't expect it to be over 200°F. The ESC's heatsink was about 130°F and the battery was barely warm to the touch, so obviously the motor is the weak link in my current setup. I expected that, just not to such an extreme. Interestingly, the armature coils still look nice and shiny -- all of the smell was coming from the commutator, which is currently regretting the day it was born. The comm is covered with a lovely shimmery-black coating of baked-on carbon dust from the brushes.

So yeah, if anyone was wondering whether a TrailMaster Sport 550 21T is up to the task of moving a 9-pound TRX-6, the answer is "no". (at least, not on 2S.) Now I get to contemplate whether to buy yet another TorqueMaster Pro to put in my TRX-6 just like all my other crawlers...or maybe try a 5-pole CrawlMaster Pro since I'm running a pretty high-torque/low-rpm setup and 5-pole motors are supposed to be better for that...or maybe splurge on a HobbyWing Axe, which I'm also curious about. I'm a little concerned that any 550-size brushed motor will be overwhelmed, but I'm also a little concerned that if I put a brushless setup in my TRX-6 then I'll suddenly want to spend a couple thousand dollars putting them in all my other crawlers too. Choices, choices.

In any event, the moral of the story is: If you're going to run a motor in a high-torque/low-rpm setup, make sure it's a premium motor with the strongest magnets you can get, not a disposable motor with cheap magnets. If the armature doesn't have strong-enough magnets to push against, it will behave like an electric heater instead of an electric motor. I already knew this, but somehow I was still surprised by the result of this test.

[CamoColton]

Honest question - why not just run 3S, and then gear down to get the top speed you're looking for? Would cut your Amps by a third.

The 6x6 has taller tires than a TRX-4, and two more of them needing to be powered. So much is working against you here. In the 1:1 scale world this is like putting 40's on a stock Jeep without changing the axle ratios from stock.

[dirtman71]

I would not blame the motor. Sounds like it is geared way to high and you sound like you pushed it quite hard through a Lipo pack. Over gearing is just like over proping a rc plane. It’s just drawing too many amps

Either gear down and volt up or gear down and kv up.

When I used to race all the time and you were in a 17.5 class stuck with that motor you had to gear it based on temp. Run 2 hard laps and check the temp. If I was just 165 I could raise the pinion till I could run the whole 6-8min with the temp at 185. If I cooked a motor it was on me

[CamoColton]

Solid advice from the man himself: https://blog.holmeshobbies.com/holme...tion-and-care/

[JohnRobHolmes]

It probably didn't hurt the motor much, if at all. A commutator will get a patina that is actually critical to it's life and operation.


Run 3s with lower gearing and it will be just fine at the same wheelspeed. A 1/3 reduction in gearing and increase in voltage will more than than half the heat generated, since heat is by the square of amp draw.

[fyrstormer]

Originally Posted by CamoColton

Honest question - why not just run 3S, and then gear down to get the top speed you're looking for? Would cut your Amps by a third.

The 6x6 has taller tires than a TRX-4, and two more of them needing to be powered. So much is working against you here. In the 1:1 scale world this is like putting 40's on a stock Jeep without changing the axle ratios from stock.

I don't run 3S because I don't want to buy different batteries for just one truck. I haven't needed 3S to move any of my RCs under 10 pounds anyway. This particular problem was the result of using a motor that wasn't up to the task; if the battery had been the problem, the battery would've been hot, but it was in fact the coolest component in the entire power system.

The 6x6 DOES NOT have taller tires than the TRX-4, and I'm getting tired of correcting people one-by-one on this point. The tire height is the same; the only difference is the TRX-6 uses 2.2" wheels for a more scale-accurate appearance for the specific truck it's modeled after.

You are correct, though, that the TRX-6 has more drivetrain drag due to the extra axle and the extra pair of tires dragging against the ground. That is really the only variable in this build that I've never had to deal with before, and I don't really know how to account for it.

[fyrstormer]

Originally Posted by JohnRobHolmes

It probably didn't hurt the motor much, if at all. A commutator will get a patina that is actually critical to it's life and operation.

I've seen a healthy motor patina before; it's a dark copper color, not black. The armature seems to be fine, but the commutator definitely overheated. It's not buckled or melted at the edges, though, so at least it's still usable.

Originally Posted by JohnRobHolmes

Run 3s with lower gearing and it will be just fine at the same wheelspeed. A 1/3 reduction in gearing and increase in voltage will more than than half the heat generated, since heat is by the square of amp draw.

3S isn't going to happen because I don't own any 3S batteries and don't feel like buying them just for one truck. I'll get a better motor instead, which I was already planning to do anyway. I know running 2S means more amperage is required to provide the same wattage to the motor, and I'm fine with that; all of my other crawlers run TorqueMaster Pro 540 or 550 motors with higher gearing than most people here would think is wise, and they all work fine. I was just surprised at how much more the TrailMaster Sport struggled compared to your premium motors. I had never tried that direct comparison before.

On that note, would you recommend the CrawlMaster vs. the TorqueMaster? I remember having a conversation with you a couple years ago about the differences between 3-pole and 5-pole motors. I don't clearly remember what you said anymore, but I think you said that 5-pole motors were more efficient at low RPM but got hotter at high RPM, because having more and narrower pads on the commutator effectively translates to a faster switching frequency inside the motor. Is that accurate, or am I remembering incorrectly?

[fyrstormer]

Originally Posted by dirtman71

I would not blame the motor. Sounds like it is geared way to high and you sound like you pushed it quite hard through a Lipo pack. Over gearing is just like over proping a rc plane. It’s just drawing too many amps

Either gear down and volt up or gear down and kv up.

When I used to race all the time and you were in a 17.5 class stuck with that motor you had to gear it based on temp. Run 2 hard laps and check the temp. If I was just 165 I could raise the pinion till I could run the whole 6-8min with the temp at 185. If I cooked a motor it was on me

*sigh* Motors do not "draw amps". I don't know who invented the term "amp draw", but they need to be taken outside and hit with a rusty pipe until they learn their lesson. Electrical devices resist the flow of amperage, they don't pull amperage out of the power source. Nothing can pull amperage. Being hit with a rusty pipe would actually be a great object-lesson for that person, because it would teach them that their skull is resisting the rusty pipe, not drawing the rusty pipe towards it.

Voltage is the motive force behind electricity. Batteries use their voltage to PUSH amps through the motor. The motor merely permits a certain amperage to pass through it at any given voltage, depending on the motor's electrical resistance. The motor's electrical resistance is determined by two main factors: 1) The length and diameter of the armature wires, and 2) The electromagnetic interaction between the armature and the permanent magnets inside the can. When a motor is spinning fast, the electromagnetic interaction increases, and the motor's electrical resistance increases too. When a motor is spinning slowly, the electromagnetic interaction decreases, and the motor's electrical resistance decreases too. When a motor is stalled, its electrical resistance is at its lowest point, hence why stalled motors overheat so fast.

However, the strength of the permanent magnets is also a factor; strong magnets will produce higher electromagnetic interaction at any given wattage, and weaker magnets will produce lower electromagnetic interaction at any given wattage. This is why motors with strong magnets spin slower at the same wattage but also produce more usable torque and less waste heat. I've been running Holmes TorqueMaster Pro motors in my other crawlers for years, which have premium FB12 magnets in them (though still not as strong as the neodymium magnets in his Puller motors), but I cheaped-out on the TRX-6 because I just wanted to see it run after two weeks of sitting on the shelf. I don't know what the magnets are in the TrailMaster Sport, but they're definitely not FB12's. Weaker magnets = lower electromagnetic interaction = lower electrical resistance = more heat.

My original post was mainly intended for entertainment value. I was sharing an experience I had. I wasn't actually asking for advice on how to not make the same mistake again, because I already knew the answer to begin with.

[scalemadness]

Sounds more like a whining rant. You have been informed what the root of the problem is and instead of listening even to an expert you bi*ch and moan and pretend to be an expert. If you don't like being assisted with your issues then why post? Your asking for help posts always seem to go the same route basically you know better. Brings to question why post and ask if your already the "expert"

[Voodoobrew]

Electrons have a negative charge so they are drawn to the positive cathode and pushed from the negative anode. So depending on where said electron is the attracting and repelling forces vary.

So you can use push or pull interchangably.
Honestly it's just semantics if everybody already knows what they're talking about.

Pretty entertaining and informative all the same though.

Now let's contemplate the difference between a hoedown, a hootenany and a shindig...

Sent from my SM-N950U using Tapatalk

[fyrstormer]

Originally Posted by scalemadness

Sounds more like a whining rant. You have been informed what the root of the problem is and instead of listening even to an expert you bi*ch and moan and pretend to be an expert. If you don't like being assisted with your issues then why post? Your asking for help posts always seem to go the same route basically you know better. Brings to question why post and ask if your already the "expert"

If you read every post with the assumption that the poster is asking for help and not just talking about their hobby, that's your issue not mine.

Yes, I do sometimes have trouble with my "help" threads regarding electronics going off the rails. (this generally isn't a problem for mechanical questions, though.) The reason this happens is because I have a basic understanding of electrical engineering (because, you know I am an engineer), whereas damn near everyone else on RCC doesn't. They know how to use electronic components but they don't know why those components work the way they do. So when I ask a question about electronics, I get generic advice that doesn't directly pertain to my exact situation, and when I reply with corrections in hopes of getting better advice on the second attempt, people just get angry because I won't listen to them. So let me just say, going forward, I only want advice regarding electronics from experts or professionals, because they are the only people who will be able to explain things I don't already know in a sufficient level of detail.

I did have a question in my original post, though. It pertains to the advantages of running a CrawlMaster 5-pole motor instead of a normal 3-pole motor. Thus far everyone has ignored that question in favor of regurgitating the band-aid advice of "volt up and gear down" that everyone on RCC already knows by now.

[fyrstormer]

Originally Posted by Voodoobrew

Electrons have a negative charge so they are drawn to the positive cathode and pushed from the negative anode. So depending on where said electron is the attracting and repelling forces vary.

So you can use push or pull interchangably.
Honestly it's just semantics if everybody already knows what they're talking about.

Pretty entertaining and informative all the same though.

Now let's contemplate the difference between a hoedown, a hootenany and a shindig...

Sent from my SM-N950U using Tapatalk

Yes, electrons do have a negative charge, and yes they are repelled by the negative battery terminal and attracted to the positive battery terminal, but that motive force is called "voltage", which as we all know is not the same as amperage. Amperage is energy transmitted by the actual movement of electrons, not the force trying to make the electrons move. You can have voltage without amperage -- that's what happens when the battery is charged but not connected to anything -- and if you work in a science lab where you get to play with superconductors, you can have amperage without voltage too. (no resistance = no voltage.) So again, the battery is providing a supply of electrons and the force to move the electrons through the motor, and the motor is resisting the movement of electrons -- NOT "drawing" them out of the battery. So no, you can't use the terms "push" and "pull" interchangeably. If you think otherwise, it must be very entertaining to watch you try to open doors.


Do you have any thoughts about the 5-pole vs. 3-pole question I asked repeatedly in this thread?

[DRTMI]

Originally Posted by scalemadness

Sounds more like a whining rant. You have been informed what the root of the problem is and instead of listening even to an expert you bi*ch and moan and pretend to be an expert. If you don't like being assisted with your issues then why post? Your asking for help posts always seem to go the same route basically you know better. Brings to question why post and ask if your already the "expert"

"Like"

[dirtman71]

Amp draw or amp pull who cares. The more load, the more weight you have to pull, the more drivetrain you have the higher amp load on the motor

I could care less that you smoked a motor. What I didn’t like is you came off as it was the motors fault. Everybody here is saying that motor probably would have been fine if it would have been geared properly for the load and if you wanted more speed put in a 3s

[Voodoobrew]

If your going to believe I said the motor draws power that's your misconception.
I can't control the assumptions of others.

As far as the torquemaster vs a crawlmaster... Well one has more torque and one has more crawl don't they. It's realy that simple, just pick which is more important to you. Neither is a bad choice, just a slightly different feel. Everyone has different preferences. Personally I'm happy with a 550 21t trailmaster geared down to 100:1 on 4s. At that gearing the difference to a 550 10t crawl master is barely noticeable on a 9lb rig to me. Besides I keep the punch turned down. Low gears add both smoothness and torque. Much more obviously then higher end motors do imo.

FYI I just run hw 1080's for brushed rigs with the pwm on high. I had a Holmes Hobby Ble, which could crawl slightly slower and smoother in silent mode but I traded it for other toys. I didn't notice a brushed benefit for the mamba x.

If you are concerned the 550 is not enough go with a magnum.

Sent from my SM-N950U using Tapatalk

[Voodoobrew]

And y45 magnets in the sport series motors I believe.

Sent from my SM-N950U using Tapatalk

[punkindrublik]

Wow...

[Voodoobrew]

Originally Posted by fyrstormer

3S isn't going to happen because I don't own any 3S batteries and don't feel like buying them just for one truck. I'll get a better motor instead, which I was already planning to do anyway. I know running 2S means more amperage is required to provide the same wattage to the motor, and I'm fine with that; all of my other crawlers run TorqueMaster Pro 540 or 550 motors with higher gearing than most people here would think is wise, and they all work fine.

let me see if I'm reading this right, You don't mind spending $100 on a nice motor that has a good chance of burning up because your other rigs are also geared high and don't burn up, to put in one truck.

But spending $50 on a 3 cell battery (which can also work in your other vehicles but I can play along and say it will make them to fast isnt going to happen) and $10 on a smaller pinion to cool down your motor, increase your low end slow crawling and increase your overall torque is just a flat no?

I am probably missing something critical.

Because you clearly stated that you know your planning on making it run hot
by choosing lesser voltage...
and higher gears...
On purpose...
I think it's awesome that your sending money to to the motor guys instead of just burning it directly, they can find some good use for it I am sure.

Edit: I am just going to add this little smiley face right here because I just couldn't not reply and I really don't want to piss anyone off, and as the OP said

Originally Posted by fyrstormer

My original post was mainly intended for entertainment value. I was sharing an experience I had. I wasn't actually asking for advice on how to not make the same mistake again, because I already knew the answer to begin with.

It's all in good fun right?

[fyrstormer]

I suppose the critical thing you're missing is that I enjoy a challenge, and challenges are created by constraints.

The constraint in question is that I want to run my entire RC fleet using the same batteries. I eventually compromised on this point to run my Summit and Electric T-Maxx on a single 4S battery instead of dual 2S batteries, because it simply got too irritating to balance-charge two 2S packs before I could run either of those vehicles. However, it still annoys me a little bit that I have two different battery types for my RC fleet, and I don't want to expand my collection of batteries that can only be used in certain vehicles. All of my other RCs run just fine on 2S, and I have no qualms about figuring out how to run my TRX-6 on 2S as well. I expected the TrailMaster Sport 550 21T would be deficient in this truck, but I used it anyway because I was in a rush and I was willing to sacrifice a cheap motor that was already halfway through its lifespan. I just didn't realize how deficient it would be.

I posted this thread with the intent to convey my amusement at how badly the motor performed in circumstances that I knew would be difficult for it. Somehow it got misinterpreted as a cry for help even though the very first line in my original post clearly stated I knew what the problem was. Obviously the motor was being asked to do more work than it could handle, and yes, it's my fault for overestimating the motor's capabilities, but since I'm the "boss" of this project, the motor will be getting replaced rather than the user.

Anyway, an upgraded motor won't burn up, not with 25.7:1 gearing in low gear. I've been running a TorqueMaster Pro 550 21T in my 2-speed Wraith for several years. My Wraith is heavier and higher-geared than my TRX-6, and that motor is still going strong. This isn't the first time I've gotten into a fight with people on RCC about the gear ratios I use; volt-up and gear-down is the easy way to skin the cat, but it isn't the only way to skin the cat.

I guess I'll just have to buy a CrawlMaster so I can test it and see how it actually feels compared to a TorqueMaster. At this point, I suppose my only real question is whether a 5-pole motor can inherently handle a heavier workload than the same-size 3-pole motor.

[durok]

fyrstormer...

You talk a good game Re: electronics, but the fact remains - you made this statement:

"So yeah, if anyone was wondering whether a TrailMaster Sport 550 21T is up to the task of moving a 9-pound TRX-6, the answer is "no"."

Only after that did you clarify - by adding "(at least, not on 2S.)"

After that you continues in the same vein - "I'm a little concerned that any 550-size brushed motor will be overwhelmed....(snipped as irrelevant to this conversation)"

And more:

"In any event, the moral of the story is: If you're going to run a motor in a high-torque/low-rpm setup, make sure it's a premium motor with the strongest magnets you can get, not a disposable motor with cheap magnets. If the armature doesn't have strong-enough magnets to push against, it will behave like an electric heater instead of an electric motor. I already knew this, but somehow I was still surprised by the result of this test."

You mention the model of a motor in a thread title, and then disparage its quality - yet you are misusing it by not following the manufacturers recommendations.

Let's dig in a bit here - stock TRX-6 gearing is 45t spur, 11t pinion.

You stated you were running a 39t spur, and a 20t pinion?

Nothing higher than 39/15 is recommended by the factory - and, sure - I know ignoring factory recommendations is what most of us do, especially when swapping in a motor that's likely a bit stronger - but you went WAY down the gearing chart (shown below)... and yet stuck with a 2S LiPo?

Sheesh.

Whatever.

I'll choose to ignore anything else you say about electronic anything, based on that behavior. You ought to be very happy if the Trailmaster Sport spins up for you after that treatment, and stop slagging its performance since you treated it like absolute shit.