DF03 burning out motors

[Joe Boy]

Evening all, 

so my DF03 keen hawk has burnt out its 3rd motor in as many weeks

The first two motors where old and well used, a titan clash and a team Orion. Both burnt out quite quickly after installing. I found an old silver can that seemed like it hadn’t been used and that has lasted at least 3 sessions of driving, giving up today whilst we where driving on rough dirt. 

my question is have I just exhausted the life span of my old motors, or is this something I can prevent? Or would a slipper clutch prevent this?

I plan on getting a Tamiya torque tuned motor, but can’t find a slipper clutch in stock anywhere!
Im running hobbywing 1060 with 2s Lipo.

[BuggyGuy]

What kind of gearing are you running - how hot are the motors getting.

TBH I expect DF03 cars and parts to gradually be phased out now the TD4 has been released (though nothing has been announced officially yet as far as I know)

[Joe Boy]

It’s all stock gearing, 26t pinion and 78t spur

[ThunderDragonCy]

Sounds like something binding to me. Check all the wheels and diffs spin freely with the drive shafts removed. 

[Joe Boy]

That’s a good shout, I have spun the wheels by hand with the motor removed and all seems good, it could do with a strip down anyways so would be a chance for a bit more of a in depth look

[Juggular]

Have you installed bigger tires? 

 

[alvinlwh]

1 hour ago, Joe Boy said:

It’s all stock gearing, 26t pinion and 78t spur

That gives a FDR of 9.18, should be fine for most motors. I had used a silver can on a different chassis with a FDR of 2.91 and it took few runs to kill the motor. As someone else had suggested, check for binding. I once had a car with a jammed bearing killing the motor. Nearly took the diff along. 

[Joe Boy]

1 hour ago, Juggular said:

Have you installed bigger tires? 

 

Nope there stock also, over ten years old, but still stock…

[Juggular]

hmmm... I'm guessing something's got to be binding?  

Perhaps you could do a roll-test?  

A non-binding 4x4 chassis would roll 5-6 feet on a flat surface, if you push the rear bumper with your foot from behind.  With a brushed motor installed, unpowered.  Obviously, if the motor is taken out it would roll much farther, like 10-15 feet.  I assume ball bearing installed chassis, of course.  

==========================

The last thing that could bind, is the gear mesh between the pinion and the spur gear.  For decades, Tamiya instructed us to use a piece of paper between the gear. Not some fancy resume paper. Thin newspaper would be the best choice as a gap measuring device. (In other words, teeth shouldn't be binding. There should be some play.)  Hopefully one of these tests would reveal the source of the problem...

 

[WillyChang]

RC brushed motors weren’t designed to run for 40-60mins nonstop... 5-10mins max then let them cool down. 
 

but lipo packs now have too much capacity for long runtimes

worst still is DF03’s motor gets terrible airflow, really needs forced air cooling 

[El Gecko]

1 hour ago, WillyChang said:

RC brushed motors weren’t designed to run for 40-60mins nonstop... 5-10mins max then let them cool down. 
 

but lipo packs now have too much capacity for long runtimes

worst still is DF03’s motor gets terrible airflow, really needs forced air cooling 

I'm regularly doing 60-120mins nonstop on one of my brushed motors (except 5-10mins cooldown during battery change halfway through) so it's not the length of time that the motor is running necesarily, it's more how long the motor is running at W.O.T. (wide open throttle), the difficulty of the terrain (strain on the motor), and how much juice it's being fed.

Totally agree about lipo, even 2S has a higher nominal voltage (7.4V) than NiMH or NiCd (7.2V) which automatically increases the speed, but also increases the heat. In addition, the amperage on lipo is exponentially higher, so there ends up being a LOT more juice fed into those old motors.

Racers would run 7-cell NiMH/NiCd (8.4V) back in the day, but usually only for short 5min heats, which limited the damage. I'm building some higher-voltage NiMH packs like that, but they'll only be used for speedruns this summer--not long distance/long runtime because they would cook the motors that way.

[Wooders28]

I've ran tall gearing , in rough terrain, and not managed to burn out a motor in the DF03 (melted battery plugs and wires, but not motors).

Having gone through ,and checked nothing is binding (removed motor, pushed along the floor, and on lock to lock) ,I'd maybe go for a cheap new motor, and take it from there.

I'd probably go for a new 15t firebolt, they have a built in fan, quicker than a torque tuned, and cheaper! 

[Joe Boy]

Thanks for all the feedback and advice. I’ve done a bit of investigation and would say the rear gearbox probably didn’t help the cause. It felt notchey to spin by hand. I’ve stripped it down and a few of the bearings are suspect. 
the front seems fine, but I’ll strip it down when I’ve rebuilt the rear just to be on the safe side. 
amazingly I found almost a complete set of bearings in my parts bin, so will rebuild with all new.  
 

[Joe Boy]

I’ve rebuilt my Df03 now with all new bearings and new diff balls. All gears degreased and regressed and I made sure to have backlash on the spur and pinion gears, new firebolt broken in and fitted,

 Had a good session this morning, racing with my lad, never missed a beet and stayed warm to the touch!

thanks everyone for your help and suggestions