7xl hot need better set-up? - RC-Monster Forums

phildogg · **7xl hot need better set-up? -** 01.20.2007, 03:11 PM

currently running a 7xl on 4s 6k lipo got hot today after running for awhile,wondering if a 8xl would be better on 4s with less heat? geared 18/66 now. might try dropping to a 16/66 gearing till I decide on the new motor whats evertone thoughts on this? motor ran up to 180 deg. today..too hot for me..lmk
phil

Serum · 01.20.2007, 03:19 PM

Yeah, an 8XL would run cooler. You could consider using the rc-monster heat-sink as well. The 8XL will give you a tad less power though.. It's geared okay.. that's not it.. Sure you have got no binding somewhere?

It's geared for about 30mph now, which is nothing to worry about. Perhaps if you geared it taller, the setup would run cooler.. you could try a 20T..

phildogg · 01.20.2007, 03:45 PM

you think it may be undergeared? I would love to be able to gear up and help it..might try that first..no binding anywhere as it rolls freely..I'll try and order some differant pinions for it. thanx
phil

jhautz · 01.20.2007, 03:56 PM

WHat controller? If you are using the MM or the Quark try turning the start power and timing down to the lowest settings. That makes a big difference in motor heat too.

phildogg · 01.20.2007, 04:06 PM

running the mm I know the timing is on low (lowest setting) .. start power is on 3 (highest) I'll turn it on 1 (lowest) and mess around with it more later. whats the thoughts on overgeared or not like serum pointed out?.. I was thinking maybe a 8xl on 4s and gear up..but if gearing up will help now then its even better..lol thanx bros
phil

01.20.2007, 04:16 PM

how hot is hot? A heatsink is not going to fix the problem, in many cases can add to it. Undergeared will do it for sure, how is the top speed?

phildogg · 04:24 PM

Quote:

Originally Posted by Bomb-Proof

how hot is hot? A heatsink is not going to fix the problem, in many cases can add to it. Undergeared will do it for sure, how is the top speed?

I posted it was running 180 deg in the first post.. I can't add a heatsink its the 7XL C can..the calculator says around 30 mph..

coolhandcountry · 01.20.2007, 04:55 PM

You could try a 16 and 20 to see which helps.
Do you happen to know temp on the esc?

phildogg · 05:13 PM

between 95-120 with fan.. depending on how hard and how long I have been running..thanx bros. 16t would drop me down to aroun 26-27mph..lol I'm getting slower than a stock maxx..lol I hope thats not the case..
phil

coolhandcountry · 01.20.2007, 05:23 PM

The temps on esc seem good. You could try a 20.

phildogg · 01.22.2007, 04:45 PM

well an update didn't have any bigger pinions so I thought I would try to gear lower and make sure .. well went with 18/70 gearing and esc temps were 70 deg. and motor temps were around 175deg with around 10 min runtime. so looks like I'm undergeared gonna pick up a couple differant pinions..
phil

01.22.2007, 06:58 PM

Yeah, the guy at StarluckRC, said (and I hope that I don't misquote him) that motors really have a sweet spot, in terms of current draw, that they like to run in. He said that a motor will run hot due to either overgearing or undergearing. It sounds like you're undergeared. Go ahead and try gearing up. If it makes the truck too fast for your application, you'll probably have to try a higher turn motor, which may not be a bad thing. It'll be easier on the drive train and you should get more runtime.s

coolhandcountry · 01.22.2007, 08:49 PM

You could try to go down on the spur to a 66 tooth. If you have one handy. Maybe cheaper than the pinion to.

BrianG · 01.22.2007, 08:55 PM

You are somewhat right to a degree. LMT has some diagrams of their various motors showing volts, amps, total rpm, and efficiency. I know these are LMT motors, but I would think most motors would follow a similar curve. As you can see, there is an ideal rpm for best efficiency, but even outside that ideal, it's not like the curve drops like a rock or anything, so you should be ok.