Very noisy after a hot motor cool down. Did I burn up a motor or a transmission?

Ramjet

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My 1/10 EXC Ruckus Monster truck has been upgraded to support 3S. Besides the battery and aluminum wheel hexes, only the ESC has been upgraded because the stock ESC Horizon Hobby limits its ability to 2S, even though the ESC's manual says it supports 3S. I'm not happy about the forced upgrade I had to do, however, this thing is fast with 3S! I've clocked it at 41 mph.

Today, I was bashing around a big field, mostly wide open. I was letting the motor cool every 5-10 minutes. The motor is the stock, Dynamite Tazer 3300Kv 4-pole 540-size Brushless motor. It got pretty hot at one time, so I turned the ESC off and let it cool for 20 minutes. When I powered back on, the drive train was very noisy when I started rolling. I knew right away that something wasn't right, so I stopped bashing and went home. When it is powered off, the rear wheels feel like they have jittery torque on them when I manually spin them, as if there is a motor brake applied. I tested it at very slow speeds, and the truck does run, but it runs very, very loud. Something isn't right.

Does this sound like a burned up motor or a damaged transmission?
 
Hard to pinpoint it from your description, but it sounds more like you have stripped the spur gear. I would start there and see what you find. I stripped out the stock spur in my Ruckus when I switched from the 15 turn brushed motor to a 3900kv brushless motor on 2S. Would not be surprised if you stripped the spur on 3S.
 
Also, 2 side notes -

get a thermometer. I use a $12 harbor freight pocket thermometer. your motor can handle up to 160f fine (180f is danger), but 120f-130f is 'scalding hot'. Know what your motor temp really is can help you keep it alive long term...

Which leads to #2 - if you want to run 3s most of the time, you will probably need to run a smaller pinion, to keep heat down. Monitor temps, and if they start getting above 160f, then drop a few teeth on the pinion. Also watch the ESC temp - you want it to stay below about 150f. And the battery (lipo) should stay below 120f.
 
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My 1/10 EXC Ruckus Monster truck has been upgraded to support 3S. Besides the battery and aluminum wheel hexes, only the ESC has been upgraded because the stock ESC Horizon Hobby limits its ability to 2S, even though the ESC's manual says it supports 3S. I'm not happy about the forced upgrade I had to do, however, this thing is fast with 3S! I've clocked it at 41 mph.

Today, I was bashing around a big field, mostly wide open. I was letting the motor cool every 5-10 minutes. The motor is the stock, Dynamite Tazer 3300Kv 4-pole 540-size Brushless motor. It got pretty hot at one time, so I turned the ESC off and let it cool for 20 minutes. When I powered back on, the drive train was very noisy when I started rolling. I knew right away that something wasn't right, so I stopped bashing and went home. When it is powered off, the rear wheels feel like they have jittery torque on them when I manually spin them, as if there is a motor brake applied. I tested it at very slow speeds, and the truck does run, but it runs very, very loud. Something isn't right.

Does this sound like a burned up motor or a damaged transmission?

Welcome to the world of RC'ing Ramjet! If you like speed 3S is the way to go. My son and I have 17 rc trucks between us and half are brushless motors (me), my son is Driving Miss. Daisy!!! My fastest brushless is 75mph and my slowest is 45 (it's 4wheel drive). I'm not to familiar with the Dynamite brushless motors, I'm pretty much a Castle fan. However, I would think that setting the ESC would be somewhat the same. What I'm about to say, you can do with a Castle Bruhless motor, hopefully you can do the same with your Dynamite: you can (or should be able to) set your ESC to shutdown at a desired temp so as not to damage the ESC or motor. You should also be able to set the ESC to shutdown when the Lipo battery reaches a certain low voltage (usually around 3 volts) as not to drain it completely. If you drain it completely your in big trouble; as the saying goes you can't charge a depleted Lipo, however there is a work-around but that's another story. I would also recommend that you put a fan on the ESC to suck all that heat off of it. Don't blow the air on it, as you are just blowing hot air back on to it.
I would also recommend that you replace your spur and pinion with a hardened spur gear and pinion from Hot Racing. Also, change your gearbox to metal gearing. I know this all sounds like a lot of work, but it's real easy. There is a lot of other upgrades you can do, but I think the above is a good start.
 
Thanks for the advice on the temperature monitoring tool.

I finally had the time to inspect the gears. The spur gear (I think that's what it's called) is definitely stripped. The pinion gear has evidence of wear too, so I will need to replace both. Pictures are attached. Since my stock battery is a 8.4 V NiMH and I've upgraded to 3S LIPO, what gears do you recommend that will hold up better with the changes I've made?

If you could provide part numbers or links to a spur gear and smaller pinion gear, that would be greatly appreciated. Thanks!
 

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Yup. Dead Spur.

And - wow, tiny pinion! Not gonna gear down much from there.

For pinions, I like Robinson Racing, although there are other good gear makers too.

Also - Might plan on a new bearing kit. Rusty bearings will probably need to be replaced.
 
I would also recommend that you replace your spur and pinion with a hardened spur gear and pinion from Hot Racing. Also, change your gearbox to metal gearing.
In your pictures, your pinion is 18t and your spur is 87t. My dead spur was 48t. I understand that I should get a metal spur gear, but how many teeth spur and how many teeth pinion? Top end speed isn't as important as durability.
 
I don't have the 4wd ECX, just the 2wd, so I am not up on all the cross compatible parts, or what the needed tooth count is. Google is your friend here...

But for ECX branded replacement parts - the spur -
https://www.amainhobbies.com/ecx-mod-1-spur-gear-2-45t-ecx232019/p276035
Seeing as they sell this gear in a 2 pack, I am betting you need to get good at swapping them out...

ECX branded pinion set - 9t and 12t -
https://www.amainhobbies.com/ecx-mod-1-pinion-gear-set-9t-12t-ecx232028/p276218
Guessing one of these is your stock pinion, maybe the 9t?

Here are the RR pinions - select the tooth count above the "add to cart" button. no 9t option, though, that is very small.
https://www.amainhobbies.com/robins...n-gear-w-5mm-bore-19t-rrp1219/p454463?v=25024

Last - Hot Racing makes steel gears and aluminum parts for lots of cars - a quick google "hot racing ECX 4wd spur" gets me this steel spur -
http://www.ebay.com/itm/like/292083184414


Again, I have the 2wd truck, not the 4wd truck, so you need to read the descriptions carefully to make sure they are for your truck before buying...
 
I can't seem to gear down with metal from stock, because the the stock pinion is 9t and the spur is 48t. The lowest pinion with a 1/8 (3mm) bore is 8t 32p, but the only 32p metal spur that I can find that Hot Racing's Mod1 45T Steel Spur Gear SECF45M1 at http://hot-racing.com/?partnumber=SECF45M1;c=900

So, my effort to upgrade my gears by going to hard metal and gearing down has been unsuccessful. Does anyone else know where to get a compatible spur gear that is 32p and greater or equal to 48t?
 
Seeing as you can't gear down, the next option would be to "KV down" - that is, buy a motor with a lower KV. This will slow down the truck, though. http://www.hobbypartz.com/96m06-car-3650-2230.html

Option 3 would be to get a long can motor low KV motor. The long can give big torque and lower heat, so you should be able to go bigger on the pinion without getting too much heat. Then get that Mod1 spur, and a mod1 5mm bore pinion - long can motors are nearly all 5mm shaft, and most 5mm bore pinions are Mod1. So if you want the long motor, getting the mod 1 spur will make life much easier, plus it will never strip. The next possible problem - will the diffs handle the extra torque?

At some point, you get to the limits of the chassis. Then, if you still want to go faster, you need the "Kraton" upgrade.
 
Then, if you still want to go faster, you need the "Kraton" upgrade.
Yup, understood. I purchased an Arrma Kraton a few days ago. Can't wait for it to arrive!

Question: If I go with the larger, long can motor with the 5mm bore, I understand that pinion will need to be changed to accommodate this larger bore, but will the motor mount fit properly and will the spur gear still fit?
 
Congrats on the Kraton! I love mine (v1)...

be sure to measure how much room you have in front of your motor. If you current motor is a standard 3650, a 3670 will be 20mm longer - almost an inch. Again, I don't have that truck, but from your picture, it looks like you should have room. As long as you stick with a 36xx motor and not a 40xx motor, it will be the same diameter, so you will be good there. Last - what ESC do you have? a 3670 motor will need a 80a or 120a ESC. If you bought the dynamite 3300kv combo, I think it comes with either a 45a or 60a ESC, so that would be an issue. Another possible 'got-ya' - a 120a ESC will be larger. So read specs carefully, and make sure you have room for both the bigger motor and bigger ESC.

For the pinion, most all the '550' motors (meaning 36mm diameter, but longer than 50mm) have a 5mm shaft. For pinions, you can find 32p and mod1 in 5mm bore pretty common, but your stock spur is 48p, correct? And plastic. So buying the Hot Racing mod1 steel spur (you linked it above) kills 2 birds with one stone - it gets you to a easy to find pinion pitch, and is a very tough gear - should never give you a problem. But it might be loud - steel on steel.
 
If you bought the dynamite 3300kv combo, I think it comes with either a 45a or 60a ESC, so that would be an issue.
I upgraded to the Tazer 45A v2 ESC, because the stock ESC wouldn't run 3S (the factory limited it to 2S). What would be the issue with an underpowered ESC?

For the pinion, most all the '550' motors (meaning 36mm diameter, but longer than 50mm) have a 5mm shaft.
My stock motor is a 540 with a 3.17mm shaft. The small shaft really limits what I can do with gearing.

For pinions, you can find 32p and mod1 in 5mm bore pretty common, but your stock spur is 48p, correct? And plastic.
Correct, it's plastic. I bought it in March 2016, so it's not that old, but the specs on this truck don't match what's displayed on Horizon Hobby's website. I'm not sure if it's 32p or 48p, but I counted the teeth and it's 9T/48T.

So buying the Hot Racing mod1 steel spur (you linked it above) kills 2 birds with one stone
In my ignorance, I thought I could mesh a 32p pinion with a Mod 1 spur, but it's not working out. Or, maybe the excessive noise from metal on metal is making me think that it's not meshing. So, I haven't run the truck with the new metal gears yet.

The problem is that I can't accomplish all three of these items with the 3.17mm shaft.

  1. Change to all metal gears
  2. Gear down on pinion
  3. Gear up (or the same) on spur
I have new 3650 3900Kv motor with a 5mm shaft on the way. Now, all I need (hopefully) is a metal Mod 1 pinion.
 
In your pictures, your pinion is 18t and your spur is 87t. My dead spur was 48t. I understand that I should get a metal spur gear, but how many teeth spur and how many teeth pinion? Top end speed isn't as important as durability.
Keep 87 tooth spur but go to steel. Your pinion can be what ever u want more teeth more speed, less teeth less speed. You can also put bigger tires on the back and pickup a little more speed and pop some wheelies. Keeping everything cool is very important, the higher KV motor, bigger pinion and bigger tires will cause more heat and less torque off the line. The less of the above will be reversed. I recently installed a 2x2 12volt brushless fan running on it's own 3S 50C Lipo pushing 24.0 CMF. My motor and esc is now running at 85 degrees and 82 for e esc. Checkout the pics.

20180110_154821.jpg 20180110_154802.jpg 20180110_171524.jpg
 

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