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Cuiken

What is ‘mild brushless’?

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6 hours ago, nbTMM said:

So a motor that makes 480W of mechanical power at 8.4V will be using about 114A from the battery to do it (480/8.2/50%). Stall current or the current at 0% rpm will be twice that of 50% rpm - 114*2 = 228A.

Just slightly over what I thought.....!! 😳

To melt a lipo casing, was it closer to the 100A? 

 

6 hours ago, nbTMM said:

The claim that a saddle pack can maintain 330A continuous is unfortunately hog wash.

 

The ,'so should be', was kind of based on Stews 269.4A reading on the data log, running the Turnigy 5.0 60/120C (3s right enough).

Should really have a check on the Muchmore esc, and see if it logs amps aswell as Max Rpm.

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All good chat here and good bit of education. Thanks.

As an FYI, I had a reminder of the perils of brushed motors this weekend. I was running a torque tuned in my otherwise stock XV-01 with a 24T pinion which is just slightly larger than the 22T the kit comes with. After one pack (with plenty of breaks) I noticed it slowing down. Figuring it was the battery I swapped for a fresh pack went back out and the motor more or less instantly smoked.

Seems odd as there is no resistance in the drivetrain (freshly rebuilt) and the belt tension wasn't too high. Clearly it was overgeared but, wow, I'd forgotten how sensitive brushed can be. Or, at least, I've never managed to do this to a brushless motor.

I might consider trying to build a cheapo 17.5T combo for it instead.

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@Cuiken I had melted quite a few brushed motors with inappropriate gearing. The worse (or best depending on how you see it) is FDR of 2.4 on a silver can. Goes up in smoke after about 3 packs of lipo. 😁

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14 hours ago, alvinlwh said:

@Cuiken I had melted quite a few brushed motors with inappropriate gearing. The worse (or best depending on how you see it) is FDR of 2.4 on a silver can. Goes up in smoke after about 3 packs of lipo. 😁

Well, that's the thing. I got one pack of lipo with a final drive of ~7.4 (2.6 internal * (68/24)).

No idea why it was running so hot. I went over the car last night and the front and rear gearboxes were nice and smooth. Only issue I could guess at is that I'd over tensioned the belt.

I've slackened that off and will give it. run with a stock silver can and a stock 22T pinion and see what happens.

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31 minutes ago, Cuiken said:

Well, that's the thing. I got one pack of lipo with a final drive of ~7.4 (2.6 internal * (68/24)).

ZNLq9Im.jpg

60/50 (they are the smallest and biggest spur and pinions I can find) and IR of 2. Did managed to get 40mph out of a silver can though. 😁

  • Haha 1

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12 minutes ago, alvinlwh said:

ZNLq9Im.jpg

60/50 (they are the smallest and biggest spur and pinions I can find) and IR of 2. Did managed to get 40mph out of a silver can though. 😁

 

With a trail of magic smoke behind you :)

That's really impressive. I doubt I was hitting 20mph and still smoked the motor :( 

  • Haha 1

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1 minute ago, Cuiken said:

 

With a trail of magic smoke behind you :)

That's really impressive. I doubt I was hitting 20mph and still smoked the motor :( 

That is the fun of it, I got a bag of silvercans that I had no where to use, so I smoked them. In all seriousness, it was actually a really useful exercise as I learnt more about gear ratios by smoking them than ever. When I run out of silvercans, I will put something nicer in and run it at a sensible gear ratio. 

Now, in your case, just had a thought, what surface you were running it on? Just remembered the VX is a off road-able vehicle? 

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2 hours ago, alvinlwh said:

That is the fun of it, I got a bag of silvercans that I had no where to use, so I smoked them. In all seriousness, it was actually a really useful exercise as I learnt more about gear ratios by smoking them than ever. When I run out of silvercans, I will put something nicer in and run it at a sensible gear ratio. 

Now, in your case, just had a thought, what surface you were running it on? Just remembered the VX is a off road-able vehicle? 

Smooth tarmac! Really no easy explanation for it. Good news is that the ESC at least seems to have survived.

Maybe the motor was just a poor example. Tamiya motors are generally robust though (when used in spec).

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When I think of mild brushless I think of "finned 540" motors which I believe are 380-sized rotors in a 540 can.

https://www.amazon.com/GoolRC-Surpass-4370KV-Brushless-Waterproof/dp/B07RMJDCYS/ref=sr_1_4?crid=2CSDBMV5QF6E8&keywords=brushless+finned+540+motor&qid=1663351773&sprefix=brushless+finned+540+motor%2Caps%2C144&sr=8-4

I like these a lot - you get the benefit of relatively high RPMs (if you want them) without the massive current draw or power of a true 540. Most Castle motors (even the 1406, which i think is the smallest 540 sized) are way to powerful for my taste and I end up tuning them so far down that I may as well use a smaller motor entirely.

 

 

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On 9/16/2022 at 7:16 PM, smirk-racing said:

When I think of mild brushless I think of "finned 540" motors which I believe are 380-sized rotors in a 540 can.

https://www.amazon.com/GoolRC-Surpass-4370KV-Brushless-Waterproof/dp/B07RMJDCYS/ref=sr_1_4?crid=2CSDBMV5QF6E8&keywords=brushless+finned+540+motor&qid=1663351773&sprefix=brushless+finned+540+motor%2Caps%2C144&sr=8-4

I like these a lot - you get the benefit of relatively high RPMs (if you want them) without the massive current draw or power of a true 540. Most Castle motors (even the 1406, which i think is the smallest 540 sized) are way to powerful for my taste and I end up tuning them so far down that I may as well use a smaller motor entirely.

 

 

That's a good tip. My mate runs a brushless 380 motor in his TA03RS and it's a great match for the car. The thing absolutely flies and doesn't have 'too much' torque.

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I've noticed a massive difference between motors while running my speed run project which is the quick drive Thunder dragon. 

This uses the smaller 1/18th scale brushless system. (Now!, Not originally)

And the difference between the smaller 2030 7800kv ezrun motor and the bigger 2435 gool RC 8200kv motor. 

The gool RC motor had no where near the rev range of the EZRUN.

The EZRUN consistently ran over 40mph,

Whereas the Gool RC motor struggled to get past 35mph but on paper, should have been much faster.

You'll know yourself when you find a motor that you are happy with.

I believe this was the fault of the Gool RC motor.

Warning, video may contain swearing.

The aftermath

TnzxPkR.jpeg

EZRUN ESC ran faultless for years until I tried a Gool RC motor. ( May have been a surpass hobby, memory fails me)

YOxmySj.jpeg

I think it'll polish out.

The battery actually survived the apocalypse believe it or not.

XHRsbcJ.jpeg

Protected by it's silicone jacket.

xhjVpz4.jpeg

I still blame the Gool RC motor. :( although it may have been surpass, I can't remember.. it's probably in my speed run thread.

  • Sad 1

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1 hour ago, wolfdogstinkus said:

I still blame the Gool RC motor. :(

I'll agree.

You really do ,pay your money, take your chance' with the cheap stuff. 

I got the combo to try, it's in a boomerang atm and on 2s (a bit gutless), but ran 3s for ages, and it's been fine....so far 😳

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1 hour ago, wolfdogstinkus said:

The battery actually survived the apocalypse believe it or not.

XHRsbcJ.jpeg

Protected by it's silicone jacket.

You are going to reuse that??? 

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35 minutes ago, alvinlwh said:

You are going to reuse that??? 

Meh!. Tis but a flesh wound. 

I've used lipos in far worse conditions. 

This was unscathed despite appearances, it was mostly just discoloured by smoke damage and still balances perfectly.

I stopped using this one, after this swelling.

4EY7jbG.jpeg

 

XNAlddR.jpeg

 

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7 minutes ago, wolfdogstinkus said:

Meh!. Tis but a flesh wound. 

I've used lipos in far worse conditions. 

This was unscathed despite appearances, it was mostly just discoloured by smoke damage and still balances perfectly.

I stopped using this one, after this swelling.

4EY7jbG.jpeg

 

XNAlddR.jpeg

 

And people are wondering how dangerous lipos are. 🤣

I had a powerbank that started swelling like that, threw it out immediately. 

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5 minutes ago, alvinlwh said:

And people are wondering how dangerous lipos are. 🤣

I had a powerbank that started swelling like that, threw it out immediately. 

Yeah, I did throw that one out immediately but if they puff up like pillows but still balance, and still fit in the car, I still use them. With extra care of course.

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