Granite Granite Mega 4x4 Stock motor getting hot on NimH Battery

[Joceton]

Hey folks. Looing for some advice. The Granite 4x4 Mega that my daughter has seems to be having some issues. The Motor is getting hot on a 3300 mah NimH battery, to the point where it cannot be touched for more than a second for two. The wheels also don't seem to spin freely when the power is not engaged. With the power module attached in the truck, the front and rear wheels will not even get a full turn when I spin them before they stop spinning. If I remove the power module, the wheels will spin a bit better (maybe a full turn and a half). The spur gear seems to move freely inside the power module, and I meshed the spur gear and the motor using a thin piece of paper as a spacer.

Is this lack of free spin on the wheels normal? I wouldn't expect that the motor should get that hot either.

I have replaced the spur gear twice already, and I think this was a result of using a 2S lipo battery. I read here that the 2S is a bad idea for the stock motor, but do the spur gears go in these a lot?

 

[Exc3l]

Typical on the brushed line of arrma. I know it sucks but there are a couple of fixes. Getting a really good set of fans or switch to a brushless motor and esc. No the spur shouldnt go out that much from what I know. There was a thread on here a couple days ago that was on the same topic.

 

[Joceton]

Typical on the brushed line of arrma. I know it sucks but there are a couple of fixes. Getting a really good set of fans or switch to a brushless motor and esc. No the spur shouldnt go out that much from what I know. There was a thread on here a couple days ago that was on the same topic.

any suggestions on a fan? I didn't know I could add one? Also if you can suggest Brushless ideas that would be great.

Thanks

 

[Jerry-rigged]

This all sounds mostly normal. For the spur mesh, realize that with the power module out of the truck, the spur is only supported on the back side. When it is installed, and captured by the diff input, it will be supported on both sides. The moving spur makes adjusting the mesh tricky, as you have to kind of guess as the mesh. (I am guessing this is why Arrma originally had pre-drilled holes for the motor mount).

Free-wheeling - it will not free-wheel much with the motor installed. Without the motor, it should spin better, but it still won't have a 'spin forever' feel like a fishing reel. I just tested my Granite, I pulled the driveshaft, and spun the front wheels, they only spun about one second. But the bearings and gears are about as smooth as I expect.

Temps - yes, the Granite has an overheating issue, especially if you run in grass. If you can hold your finger on the motor for 1-2 seconds, then it is probably about 130f-140f, still safe. The danger zone for brushed motors is 200f, but you want to keep them under 170f. And yes, 170f will leave white burn marks on your fingers...

You can get a cheap IR thermometer from Home Depot (electronic tools dept.) or Harbor Freight for under $20. This will take all the guess work out of motor temps, and let you know if you really have an issue.

 

[Exc3l]

any suggestions on a fan? I didn't know I could add one? Also if you can suggest Brushless ideas that would be great.

Thanks

Here. Max10