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#1
09-10-2011
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Hot centre diff
I am running a Losi 8ight-T brushless with 10,000 in centre diff. After about 7mins I got a reading of 210F for the centre diff, is that too high ? Would upping the oil to 15,000 help ? For info the motor and ESC were also warm/hot and the car was obviously squating and spinning out the front tyres a lot.
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#3
12-10-2011
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Yes your front wheels are spinning up, basically the centre diff is getting a work out! I had a crt.5 that I put mamba 2650 in on 4s, The centre diff (5k oil) got so hot it melted the rubber boots on the propshafts. I had to run thin oil to stop the wheelies but in the end dropped to 3s. Anyway, as your centre diff works it generates heat, so long as its not melting anything it wont matter., but if you can go a bit thicker without upsetting handling then thats less power lost in heat and more on the track.
It has nothing to do with gearing, why would it.
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#4
12-10-2011
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Quote:
The motor is bolted to a metal plate (motor diff mount) which bolts to the centre diff. The motor will use the motor diff mount like a heat sink which in turn will heat the centre diff. If you run a thin oil in the centre diff it will allow the diff to transfer drive to easily which will heat up also, but wouldn't explain a hot esc and motor. the truck is more than likley over or under geared.
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#5
14-10-2011
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Yep, when My motor is doing about 180'F My center is at 125'F or 30% cooler. If your Center is 210F what is your motor running? EKK
If your center diff is Hotter than your motor then you could have some gear problems. The oil thickness shouldn't make any differance on your temps, unless your running some super think diff locking 50,000wt that will all but lock your diff down. Infact if your motor is running cool and your diff is still hot and you can't figure it out, ask someone who has a revo or would carry a little 50-100k wt diff oill so you can try that and rule out inner gear mess issues. Also, what motor are u running and what are the motor/esc temps?
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#6
15-10-2011
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If center diff is hotter than the motor, the diff is surely diffing out. 10K is a little light for a e-truggy. I run 10k in my e-buggy. I would go up to 15K and see how it feels, IMO it has nothing to do with the gearing.
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#7
15-10-2011
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Quote:
I got a Castle Mamba Monster / 2650kv combo thinking I wanted the fasted motor for 4s running. However it was running about 180F on 13/46t gearing (40mph top speed) on grass after 7mins with a twin fan heatsink which is too high. The ESC was above 150F as the fan was on. I have since obtained a Castle 2200kv and changed gearing to 15/48t with a new centre diff running 15000cst. I will do another run in similar conditions and check all temps again. I suspect if I try running a 6s pack I will need 20,000 or higher.
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#8
16-10-2011
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no, don't run a 2200kv with 6s on your buggy. Your tires will flair out like saw blades down the straight and throw your tires off by the 2nd qualifier . I'm not sure what kinda tracks your running where you live but but if its a technical track you should not need more than 1700-1900kv for 4s. I'd only run 1900 to max 2200 on a huge very fast track. Also, how is your body's ventilation? Many of those ESC/motor fans only have rating of 7mph of air. If you think about the avg. buggy speed being 15-25mph, having better more directed air flow in your body is actually more effective. That can't explain your hot diff but great air flow will help.
Side note: Most truggies running 7-10k center's especially with 2200 to 2650kv motors have alot of unloading on the front, which works the center diff alot (hence your possible heat issue). I run a castle 1800kv truggy motor and had to get the center to 15k just to stop the crazy front tire flairing when gunning it out of turns or down the straight. 20k for that high a kv motor might be an option if 15k still unloads to the front too much. Unloading in the front can feel like a stabilizing thing when exiting a corner but keeping power to the rear really shoots you out faster. Thats why you don't see front wheel drive drag cars. Plus if you are flaring or unloading rpms to your front tires things get very unstable if you are trying to turn or correct at that RPM.
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#9
16-10-2011
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Quote:
I did a run today on a grass playing field and got better temps - Motor 120F Diff 140F Battery 100F ESC - less than 150F (no fan on) Ambient temp 45F Diff still a little high so I might try 20,000 and see how it handles. Edit: Found the Hudy setup guide which states in the centre diff oil 'thinner' section - "If a high-power engine is used you could waste too much power and sometimes “cook” the oil in the center differential because it overloads". I am sure that is what was happening.
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