Some testing data I logged last week. I was trying different pinions and I noted the temps of the motor with each pinion. The first was with a 13T and max temps were 120 degrees, the graph shows the temps with a 15T pinion (138) a little higher, but this made sense since it was higher gearing. Then the last graph shows the temps (176) with a 14T which surprised me because this was lower gearing (than the 15T) yet the temps were higher. I ran the test twice with similar results. 45T spur and Neu 4s 5000mah lipo used for all testing. Ambient air temps were mid 60's.

http://i142.photobucket.com/albums/r...k413/losi1.jpg
First run 13T, 120 degrees max after 10 mins.

http://i142.photobucket.com/albums/r...k413/losi2.jpg
second run with 15T, motor seems to reach operating temp (136 degrees) then levels off and holds steady.

http://i142.photobucket.com/albums/r...k413/losi3.jpg
Last run 14T temps start going up and keep going. I didn't let the motor cool as much as I did for the first two test but 176 degrees still sounded really high.

That is certainly odd. I had lower temps going from a 12 tooth to a 14 tooth, and also from 12 to an 11 tooth. It's hard to do different runs without changing variables (5s vs. 4s, running area), but this seemed to be the trend.

Did you go back to using a 13 or 15 tooth after using the 14 tooth? One loose connection from the motor to the esc can increase motor temps A LOT. So can bad gear mesh.

Yeah I agree if 13T runs cool and 15T is ok, why would 14T cause temps to go high. I am thinking your on the right track on the gear mesh. The only thing that was different was the pinion and gear mesh. The buggy, spur and batteries were the same. What has me stumped is I tried the test two different times and had similar results (14T caused higher temps), I find it hard to believe I messed up the gear mesh twice and only when I tried the 14T pinion. Well, I plan on running the test a few more times.

13/45T - motor=128 degrees, battery=88 degrees
15/45T - motor=142 degrees, battery=98 degrees
14/45T - motor=176 degrees, battery=103 degrees

Or you can just say "screw it" and run the 15t :lol:

You know that's what I was thinking. The 15T feels pretty good, faster than the 13 or 14T setup. I am just concerned that the temps (142) well pretty good, would be too high when summer gets here. I like the temps the 13T pinion was giving me but I like the speed the 15T was giving me. I figured 14T would be in the middle and be perfect, but for some reason I am seeing the highest temps with a 14T setup.

What was the kv of the motor in question here?

Dave, it is the MMM 2650kv motor.

I am a little worried because the Losi support site recommends a 13 or 14T pinion with a 45T spur on 4s and that is with there Xcelorin 2400kv motor, and I am using a MMM 2650kv motor which is even hotter.

Losi is not helping much either, in the Excelorin combo manual they say you should use a 14t Pinion with a 45T spur on 4s in a buggy using the 2400kv motor. In the 8ight-E manual they say you should use a 13T and finally the conversion kit comes with a 15 and 16T pinion (but with no recommendations on what to use). Kind of confusing. I think I will go back to the 13T just to be on the safe side.

Well I got the buggy out a few times to the track and I have been very pleased with the quality/durabilty of the Losi conversion. One thing that I am still having trouble with is motor temps, I again tried several pinions with my Eagle Tree hooked up and the lowest temps I got after 10 mins was 150 degrees which seemed on the warm side. So I decided to use a 47T spur which is closer to the stock buggy gearing (48T), instead of the Losi conversions 45T spur. This should give me a few more gearing options. I bascially had to open the hole in the plastic spacer a little bit and grind off a little area under the spacer (there is already a milled out area under the plastic spacer).

http://i142.photobucket.com/albums/r...3/DSC05546.jpg

http://i142.photobucket.com/albums/r...3/DSC05542.jpg
Using a Robinson Racing wide gear which is easier on the pinions because they are slighty wider and have more surface area.

http://i142.photobucket.com/albums/r...3/DSC05547.jpg
Hard to see, but I opened up the hole in the plastic spacer and milled out a small area under the spacer.

Going back to a steel spur?

Do you really think 2 teeth will make that big a difference?

Time will tell I suppose.

Dave, it's probably just me but I stripped the Losi plastic spur after about 5 packs. So yeah I think I will be going back to steel, the Losi spur cost as much as a hardened pinion and when using the Robinson wide spur the steel pinions last a long time. Without a slipper the spur takes a beating, both during acceleration, braking and I just had too many failures using the plastic spur which could cause a DNF during a race. Also, the 47T spur will allow me to use slightly bigger pinions which will last longer (more surface area/teeth).

That is unfortunate news. I just got my new 8T 2.0 and converted it ( http://www.rc-monster.com/forum/showthread.php?t=19101 ) with a Losi plastic Spur. I can't stand the sound steel on steel makes and was hoping the Losi would be as durable as my old Kyosho's were on my CRT.

Did you burn up only one? Any chance it was just some bad plastic?

Dave, the gear failure was kind of strange. I ran Kyosho plastic gears in my truggy/buggy and what would happen is I would knock off a few teeth from either landing with the throttle on or heavy braking coming off a big jump (both are mistakes). With the Losi spur it looks like it melted, or at least the plastic softened. I had an issue with my last run of the day (when the spur gave out) where one of my eagle tree sensor wires got caught in the rear drive shaft. This could have caused binding, heated up either the motor/center diff causing the spur to get soft. I didn't temp the motor on the last run because the sensor that got ripped out was the motor temp sensor, and by the time I temp'd it with my handheld Raytek it had been sitting for a while and cooled off. Until I hear more feedback on how the Losi plastic spurs hold up I will stick with my steel spur. I am also going to try a 2200kv motor to see if I can get my temps down to an acceptable range.

It was running cool before, wasn't it? For me I don't see how gearing the 2650 with a pinion larger than a 12 tooth (40 mph) would be suitable for racing, given the fact that most people like to run 2000 kv motors on 4s.