Gearing an 8xl Maxx - Wrong Motor?
 

I have a FLM Gorilla UE Maxx 3.3 truck I've put together over the last few years and am loving it. Just took it to the track for the first time (been bashing and breaking up until now - lotsa of mods = lots less breaks :yes: ) and I don't know why I didn't sooner. It was great. Anyways, while I've noticed my motor getting hot in the past, with many laps nonstop it is getting VERY hot, 200F+, hot enough that one of the motor leads de-soldered from one of the plugs. I am running a Feigao 8XL smooth can with the RCM Heatsink, Quark 125B w/heat mod RCM heatsink and fans, BEC, Gorilla single speed tranny (my racing ended when *something* stripped inside the transmission, maybe steel idler? haven't opened it yet), a 51 tooth Ofna Mod 1 spur with 20 tooth pinion (I've tried 18 tooth, motor gets 190F when bashing) with 2X 2s2p batts parallel, UE 8 Spider diffs, 40 bowties. I went up on the spur size thinking that would cool the motor. ESC always stays warm/good temp, runs a little warmer w/20 tooth but no problems, batts always stay cool. Should I go w/ a bigger pinion? Is this a problem that will only be fixed with a better motor e.g. Neu? I don't want to continue melting leads obviously. Any help appreciated. Thanks.

Here's what I'm running:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1.7222222222222223
Other Ratio: 1
Spur Tooth Count: 51
Pinion Tooth Count: 20
Total Voltage: 16.8
Motor KV: 2084
Tire Diameter (inches): 5.8
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.0073
Spur/Pinion Ratio: 2.55 : 1
Total Ratio: 14.52628 : 1
Tire Circumference (inches): 18.22 inches (462.82 mm)
Total Motor Speed: 35011.2 RPM
Vehicle Speed: 41.59 mph (66.8 km/h)
Estimated Adjusted Speed: 39 mph (63 km/h) - 5% loss
Effective KV Value: 2084
KT constant: 0.65 oz-in/A

rotor sounds de-magged, or there might be a short in the windings

A better motor such as the Neu will help w/temps. for sure..Many people have used the 8xl and most have had heat issues. Medusa has a 70 series motor you might check out.....http://www.rc-monster.com/proddetail...0&cat=20....on 4s, go with the 2200kv...on 5s go with the 1600kv...The 5s set up will be the more efficient set up...If you are running 6s...even better!

I run a similar setup and my 8xl gets really hot too, splashed on a teknoneu 1515/1y Waiting for it to come in the post. Should be good, and all accounts point to it running a lot cooler.

I would say that a neu 1515 1y would be your best bet to get temps down. The feigaos run hot no matter what gearing you run. The are ok bashing motors, but for a heavy truck and racing they will not cut it....

Try some gearing first of 18/40 you should have that around. I think your looking for the power too high in the Rpms. My 8xl was okay at 16/40.

the fact that it got hot enough to melt off a lead tells me you have demagged your rotor. Getting a motor too hot demagnetizes the rotor, and once that is done all you will get is heat. I belive you need a new rotor, or a new motor, if you are going to stay with cheap feigaos step up to a 9 or 10xl, a neu would give you trouble free performance

What would happen if I ran the 1600kv motor on 4s, or the 2200kv motor on 5s?

Similarly, what would happen if I bought a Neu 1515 1Y and then wanted to go 5s, would I need the other Neu motor 2D or 2.5D or something?

Thanks for the help!

The 2200kv on 5s would make the truck scream...the 1600kv on 5s would be a little slower, but more efficient

On 4s it would be a bit slow...5s is a better choice. The size of the motor depends on how fast you want to go

I run a 1515/2y with 10s and speed wise its comparable to a 1515/1y on 5s it just runs cooler. and this is with a converted 3.3 Revo

I run a 7XL geared 20/68 on an emaxx and it runs hot no matter what you do. I run mainly on the street, so its low stress compared to sand, dirt etc etc and it has gotton up to 180 degrees. I added 2 40mm fans and a heatsink to keep the motor cool. It is working for me and the motor doesnt go over 145.

If you check my picture, that was my first attempt to keep the motor cool. 80mm fan on a cheapie heatsink. Now I run 2 heatsinks with 40mm fans and it works much better. Even getting air over the can isnt enough. You really need a good heatsink and enough air through there to cool it down.

5s on a 9xl or 6S on a 10xl would be a better choice to keep the amps down and keep the motor cooler.

Ok, So I've just ordered a TeknoNeu 1515/1Y/F motor. Depending on gearing, this should be just right for 4s from what I'm hearing? and depending on gearing, I can do 5s if I want to later? What I would like to know is what temps I should shoot for in my setup. I don't want to run a fan but I don't want to hurt my new Neu. Without a fan, geared for ~40-42 mph, what kind of temps should I expect. I have a temp gun to check it. Thanks.

Dang I just ordered a 60mm 12 volt fan for my feigao motor :slap: I am going to see if it will last hooking it up to a 4s lipo(it all that I got) I hope it help enough to last until my castle combo comes in!