Frh076

Slash 4x4 heat on 3s.

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Are there any cheap motors that I can fit into my slash to make it run cool on 3s? Should it have low kv -what are the drawbacks of this? And should it be capable of running ex 6s- will this make it cooler on 3s than something that is limited to 3s?

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Your geaing and how long you ae running your truck is causing your heat issues.

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also when's is last time you maintained your truck?

Trouble with Velineon is ppl think Traxxas are "waterproof" so they think they can Put It Away Wet :( 

Do it more than once & every bearing would be rusted & jammed. Rebuild usually needs a full set of bearings for chassis and motor... every time it's never properly dried after a wet run. 

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The motor and car is well maintained. It has fans, and I have low gearing. The heat comes after about 5 minutes, and I am wondering what I can do to prevent by buying a new motor.

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1 hour ago, Frh076 said:

The motor and car is well maintained. It has fans, and I have low gearing. The heat comes after about 5 minutes, and I am wondering what I can do to prevent by buying a new motor.

How hot is hot - are you meaning it's just too hot to touch... dont suppose you've got an IR temp gun? :) (I do! Vestige from nitro days :P)

Too hot to touch is barely 50degC.

If the motor can is getting to only 80-100degC I think that's normal, shouldn't be any problem for the motor

if motor is getting hot enough to smoke and start de soldering it's wires then yeah, you've got a problem

brushless motors can get damaged too, it's not just jammed bearings. Motor that gets hot fast without doing much work can be windings shorted out, or the magnet has unglued from the shaft that drives the pinion etc

 

Back when I had Velineon in Slash 4X4 (early first batch) it didn't get that hot afaik, but we mostly ran it on 2s only anyway. It was plenty fast for what/where t got to run. 

Why do you want to use 6s anyway?!

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1 hour ago, WillyChang said:

How hot is hot - are you meaning it's just too hot to touch... dont suppose you've got an IR temp gun? :) (I do! Vestige from nitro days :P)

Too hot to touch is barely 50degC.

If the motor can is getting to only 80-100degC I think that's normal, shouldn't be any problem for the motor

if motor is getting hot enough to smoke and start de soldering it's wires then yeah, you've got a problem

brushless motors can get damaged too, it's not just jammed bearings. Motor that gets hot fast without doing much work can be windings shorted out, or the magnet has unglued from the shaft that drives the pinion etc

 

Back when I had Velineon in Slash 4X4 (early first batch) it didn't get that hot afaik, but we mostly ran it on 2s only anyway. It was plenty fast for what/where t got to run. 

Why do you want to use 6s anyway?!

I don't want to use 6s. I want to use 3s, perhaps 4s but unlikely, without it being warm. 

By hot I mean that the plastic on top of the esc is melted.

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2 hours ago, TwistedxSlayer said:

Low KV = more torque. What Terrain are you running it on?

Does love kv give more speed in that case? I drive it on asphalt or on gravel, it becomes hot on both.

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A low kv motor will have less torque than a high kv motor on the same battery. A lower kv motor will be slower in every way. The only advantages of a lower kv motor is that it runs cooler and doesn't drain the battery as fast, and well... it is slower which is advantageous if you want to crawl or run an entry level racing class. 

As far as high kv low voltage vs low kv higher voltage, it doesn't make too much difference as long as kv*volts is the same. More important is the overall power output and gearing. Motors have horrible efficiency down low in their rpm range so if you have the car geared for 100kmh unloaded wheel speed, but spend most of the time full throttle at 20kmh the efficiency will be terrible, probably less than 20%. That means that 80% of the power coming from the battery just gets turned in to heat. If you change your gearing so the unloaded wheel speed is only 50kmh then it'll ran way cooler when you're driving at 20kmh due to operating the motor at much higher efficiency, perhaps 60% - now only 40% of power is turned into heat and everything runs much cooler. The sacrifice is in top speed.
A high power setup (higher kv, lower turns, more cells battery) will run hotter than a low power setup, so it makes sense to try to operate it at higher efficiency to manage heat. That is why with a high kv / low turns motor, it is usually recommended to run a higher FDR than a low kv / high turns motor. If you want to run a high power setup with a low FDR, either you need to increase the amount of cooling (use a physically larger motor e.g. 550 size motor instead of 540, ESC with lower resistance MOSFETs and/or larger heatsink/fan), or just accept that it's not going to be able to run for very long before it overheats.

45 minutes ago, Frh076 said:

By hot I mean that the plastic on top of the esc is melted.

Melted as in warped, or just discoloured? If the former, it sounds like something has gone horribly wrong. Plastic doesn't melt until >120*C, and I would think the velineon esc should go into an overheat protection mode before it gets to that. Perhaps your motor and/or ESC have been damaged.

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Motor too hot is totally different to ESC too hot. BiTD if motor overheating then you'd be overgeared (pinion too big) whereas if your ESC got too hot you'd be undergeared... dunno if that rule of thumb still works today, but hey.

Is your Slash totally stock or have you changed anything at all?

when I had my Slash 4X4 runner, the VXL system ran perfectly... more than enough power for mucking about in big open areas, yet didn't complain about driving real slow (it was a great car for camera carrying!) following other cars around a tight track. The ESC & motor stayed cool, barely ever got too hot to touch & never needed any fan. (Fans would die when they got hit by mud anyway. The Slash was fun running in the wet)

Only minor things broke... think I broke a UJ shaft, driveshaft tip broke & the Traxxas pinion shattered. Stock gearing was spot on for my use on 2s so it just got replaced by a steel pinion of same size.

Great fun car, that Slash 4X4. Got a bit tired of full strip & rebuilding every time it got wet, so it got used less & less until a local friend offered to buy it. Still got another one but it's only progressed to body painting stage... :ph34r:

 

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btw are you in the U.S.?

i hear Traxxas takes good care of their U.S. Customers, they've got a decent exchange program if/when ppl blow up their Velineon systems

 

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6 hours ago, WillyChang said:

Motor too hot is totally different to ESC too hot. BiTD if motor overheating then you'd be overgeared (pinion too big) whereas if your ESC got too hot you'd be undergeared... dunno if that rule of thumb still works today, but hey.

Is your Slash totally stock or have you changed anything at all?

when I had my Slash 4X4 runner, the VXL system ran perfectly... more than enough power for mucking about in big open areas, yet didn't complain about driving real slow (it was a great car for camera carrying!) following other cars around a tight track. The ESC & motor stayed cool, barely ever got too hot to touch & never needed any fan. (Fans would die when they got hit by mud anyway. The Slash was fun running in the wet)

Only minor things broke... think I broke a UJ shaft, driveshaft tip broke & the Traxxas pinion shattered. Stock gearing was spot on for my use on 2s so it just got replaced by a steel pinion of same size.

Great fun car, that Slash 4X4. Got a bit tired of full strip & rebuilding every time it got wet, so it got used less & less until a local friend offered to buy it. Still got another one but it's only progressed to body painting stage... :ph34r:

 

On 2s it is fine,  but I want to drive it on 3s

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6 hours ago, WillyChang said:

btw are you in the U.S.?

i hear Traxxas takes good care of their U.S. Customers, they've got a decent exchange program if/when ppl blow up their Velineon systems

 

I'm in Norway. But the problem is not that the veleneon is bad, it's just that I want something better- perhaps a 1/8 motor.

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Back 6-7yrs ago there were a rash of owners trying "big block" motors... usually after blowing up their Velineons :P and afaik they usually talk about Castle Neo 2200 & Mamba Monster or similar from HobbyKing. Pretty sure you'll need to get a new ESC for the big block motor too.

If you're lucky the motor might just drop in without needing mods; very likely need a different pinion to suit the bigger shaft size. 

 

Then again, if I were looking at a $500 brushless combo + needing lots of DIY work... that new X-Maxx for $900 sure starts looking tempting :D 8s! :ph34r:

 

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6 hours ago, Frh076 said:

I'm in Norway. But the problem is not that the veleneon is bad, it's just that I want something better- perhaps a 1/8 motor.

The slash will do 60-70mph on the stock systems with 3s. Traxxas kit is very good. 

Sounds like a fault somewhere or binding in the drivetrain causing this. They do run hot on 3s though especially high discharge packs.

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13 hours ago, WillyChang said:

Motor too hot is totally different to ESC too hot. BiTD if motor overheating then you'd be overgeared (pinion too big) whereas if your ESC got too hot you'd be undergeared... dunno if that rule of thumb still works today, but hey.

 

 

I've read this in other areas of the inter-web to be the other way around:

 

Under-geared (pinion too small), the motor is spending too much time at top RPM's so it's overheating.

Over-geared (pinion too big), the amp draw to push the motor is too great so the ESC is overheating.

 

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1 hour ago, Mahjik said:

 

I've read this in other areas of the inter-web to be the other way around:

 

Under-geared (pinion too small), the motor is spending too much time at top RPM's so it's overheating.

Over-geared (pinion too big), the amp draw to push the motor is too great so the ESC is overheating.

 

yours might be for Brushed...? Think they reacted opposite.

 

Much of a muchness anyway, electric motors in RCs have only a very narrow "efficient" band - gotta try to optimise your setup to match your running conditions so it runs efficiently, otherwise you'll waste energy to heat. We would test run everything without fans and monitor temps via IR gun or telemetry sensor.

I don't change 2s to 3s etc in the same car without changing a lot more than just the battery. Usually easier to just have another car for 3s.

Or just run nitro :)

Or crank up the Baja :P 

 

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2 hours ago, Prescient said:

The slash will do 60-70mph on the stock systems with 3s. Traxxas kit is very good. 

Sounds like a fault somewhere or binding in the drivetrain causing this. They do run hot on 3s though especially high discharge packs.

The high speed gearing is not fitted, but I have read that the velineon system is not good for 3s, so I wa t to upgrade it

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11 hours ago, WillyChang said:

yours might be for Brushed...? Think they reacted opposite.

 

 

I've seen that mentioned with brushless (as well as the opposite).  However, it does seem to be more involved as there are other variables to consider (wheel/tire size and weight which adds more load on the motor, spur gearing, and so on).  Probably the best advice is to get a temp gun/checker to verify any change for the better or worse for each situation.

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9 minutes ago, Mahjik said:

Probably the best advice is to get a temp gun/checker to verify any change for the better or worse for each situation.

haha yeah, I bought a Raytek 20+ yrs ago to help "nitro tuning" and it's been great since. Probably there's smaller keychain size units today that do same job for cheaper too. But you've gotta do it "immediately" after car stops running, plus where exactly are you meant to measure etc etc... different motors have different layers of insulation between windings & can.

Plus back in brushed era, motor always got hot. :P wouldn't worry about overheating until the wires unsoldered themselves off the motor. In a race you just wanted the motor to last long enough to finish... some teams would chill their motors on ice for a colder point to start from. 

Whereas nowadays... ppl expect a hyper powerful brushless motor to stay cool "forever" running humongous battery packs that can run all day. Maybe when you have superconductors or watercooling :) otherwise the laws of physics/thermodynamics still rules.

 

Brushed ESCs got reasonably warm too, hot enough to melt shrinkwrap. Fans can help or better still a giant heatsink with big thermal mass. The only ESC that I've used that never got even warm was Novak Cyclone - testament to their good quality FETs & design. Got a fleet of those, only 1 ever got warmish & lacked punch so it obviously had a fault... sure enough, brake FET had stuck on making a short. Perfect working again after an airmailed visit to its maker. 

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16 hours ago, Mahjik said:

 

I've read this in other areas of the inter-web to be the other way around:

 

Under-geared (pinion too small), the motor is spending too much time at top RPM's so it's overheating.

Over-geared (pinion too big), the amp draw to push the motor is too great so the ESC is overheating.

 

Both esc and motor both have resistive losses which increase with the square of electrical current (if current doubles, heat quadruples). In the motor, the resistance of the windings, in the esc the resistance of the MOSFET transistors. Current is highest at stall, so the slower the motor is turning the hotter BOTH motor and esc get. When you increase the FDR (smaller pinion), the motor rpms increase for the same road speed and acceleration increases so you spend more time at high motor rpms where the current is low, therefore both motor and esc run cooler.

Additionally, the esc has switching losses, which occur due to the transistor resistance being at an intermediate value between on and off resistances. Technically if operating at higher RPMs, more switching is occurring therefore there are greater switching losses in the ESC and it heats up a bit more, although I suspect this effect is negligible compared to the current as long as the ESC is designed properly and doesn't spend too much time with the transistors 'half on'.

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Amen, can't avoid physics :) 

Also the spec rating (internal resistance, current capacity) of Field Effect Transistor is done at a set temperature (25degC I think) and if component is hotter than this then all bets are off.

 

Dont know if there's as much these days, but back in brushed era the sponsored racers would be asked to test out "special" units direct from factory. We peeked into some of these and they'd differ either by running at higher frequency or often they'd have different MOSFET to retail versions. Or the FETs might've been "matched".

 

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56 minutes ago, WillyChang said:

 back in brushed era the sponsored racers would be asked to test out "special" units direct from factory. We peeked into some of these and they'd differ either by running at higher frequency or often they'd have different MOSFET to retail versions. Or the FETs might've been "matched".

Interesting. As any audiophile weirdo will tell you, the quality of the switching is everything 🤓 You can probably bet those ESC's were running matched FET's. Back then you didn't have the processing power available now to make real-time feedback analysis and adjustments. Instead you had to squeeze out performance from analog components by doing things like matching FET's or adding capacitors & Schottky diodes (cat's whiskers LOL), and even then you still had a relatively inefficient amplifier. It wasn't until processors got smaller and cheaper that they could be considered for the application, which in turn gave us the brushless revolution. B)

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this was mid 90s brushed era, when NiMH appeared and now racers could go from 2400 SCRC nicads to 3300 GPs :D overnight they had 50% more current to burn, which taxed existing ESCs beyond their design limits... the Blue guys often went up in flames. Orange didn't & were the ones in front. Nosram (red) & Tekin (black) held their ground. 

 

As for power amps... Recently got dragged into "Class T"... Whats that all about then? Class A with discrete components is what it should be... not integrated chip transistors. Ah well... the toobs take too long to warm up :) 

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1 hour ago, WillyChang said:

the Blue guys often went up in flames. Orange didn't & were the ones in front

Surprising tbh... weren't LRP made in Germany back then? Figured they'd be all belts and braces :huh: I'd blame the entire culture of "overclocking" that was so popular at the time. Treating components like wear items probably made sense to the racing set :lol: As a kid in the early 90's I managed to save enough money to buy a Novak and distinctly remember being relieved that the actual quality was proportional to the price tag. I still eventually burned it up anyhow. Novak really made some nice stuff though. Sad that they are gone -_-

 

1 hour ago, WillyChang said:

As for power amps... Recently got dragged into "Class T"... Whats that all about then? Class A with discrete components is what it should be... not integrated chip transistors. Ah well... the toobs take too long to warm up :) 

Class T is just class D but configured to allow real-time modulation. They are integrated because 1) cheaper, and 2) signal processing fixes all of the crosstalk/latency/distortion, which enables the engineers to just cram everything together and let the processor sort it out.

Tubes avoid all of this by being purely analogue. ¯\_(ツ)_/¯  Just get tube warmers and you're good to go ;)

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