K8s Gearing, beating a dead horse.

[fredw90]

So I've gotten about 10-12 packs through my k8s EXB. Setup is as follows, Max5, spektrum 1100kv 5687. Ive tried multiple different gearing setups now and have gotten the following results. Outside temp from 80F-95F, running in cut grass with 1 server fan on the motor, one on the ESC.

Pinion/Spur
1.30/39-Stock Tires-Ran great till it got too hot, motor hit around 200 so I figured I needed to take it easy or adjust gearing for the 1100
2.30/47-Stock Tires-Went from one extreme to the other, motors temps were much better but was still getting too hot for my taste.
3. 30/39-Duratraxx Six packs-Temps were much more acceptable but still to hot for me.
4. 27/39-Stock Tires-Motor was hot and ESC went into thermal protection mode.

To be honest I think I like the way the truck drives much better with the belted six packs than I do with the stock tires, plus it seems to be less strain on everything, electronics AND Drivetrain. The stock tires just make it feel clunky.

Am I that far off with my gearing??? Or is it really all the grass causing the overheating, like I said I'm not running in crazy high grass. Ill try to attach a video of where I run.

One more thing... the rear diff with the stock plastic cup likes to loosen itself up and eat the gasket every handful of packs or so. So this time I replace the cup and gasket, and jammed some m4 screws into it. It was snug but the plastic seemed to take it just fine as long the holes don't have any fluid in them. Will report back...

I have a O8S EXB thats brand new with another max5/5687 that I haven't even run yet because I think I'm partial to the long wheel base.

 

[Matt05]

I would think right around 30-34/47 is where you want to be. I run my max5/980 kv in my Outcast at 30/39 and it stays cool with no fans and tons of power. My Kraton I have a max5 with a tp 1270kv geared 30/47 and that gets a little warm with no fans.

 

[fredw90]

I would think right around 30-34/47 is where you want to be. I run my max5/980 kv in my Outcast at 30/39 and it stays cool with no fans and tons of power. My Kraton I have a max5 with a tp 1270kv geared 30/47 and that gets a little warm with no fans.

I tried 30/47 and felt like it was geared too low, it did get hot because I had the thing pinned at full throttle like 90% of the time.

 

[Matt05]

I tried 30/47 and felt like it was geared too low, it did get hot because I had the thing pinned at full throttle like 90% of the time.

Well, you kind of just have to pick a happy medium some place between “not fast enough” and “gets too hot pinned at full throttle 90% of the time”. There isn’t going to be a magic gearing that gives you both unfortunately.

 

[fredw90]

I’m going to try the 27/39 tomorrow with the duratraxx tires, weather permitting. We will see how she does.

 

[Dales396lt4]

27/39 is my preferred gearing on my 1100kv K8s. But grass is hard on temp's, there is so much rolling resistance working against you.

 

[fredw90]

27/39 is my preferred gearing on my 1100kv K8s. But grass is hard on temp's, there is so much rolling resistance working against you.

27/39 seems to be the sweet spot on grass with the duratraxx belted tires. Too bad they stopped making them.

On stock copperheads the esc thermaled.

 

[IRONWORKER]

If you run WFO in grass (90% of my rc’ing) you’ll need fans, period…. I’ve found the stock esc is pretty much maxxed out, I’ve had much better results with a Max5 & my xlx2.

 

[fredw90]

Yea I’m running a max5 with the 5687.

Temps were good today in grass with the six packs. Too bad the rear diff started crunching lolol

 

[Moirae]

over a year with my 8s rigs and I've still yet to hear a diff crunch. I run 39/47 with a 1070kv and 2 fans. I bash without checking the temps at this point.

 

[Dales396lt4]

If your differential is defective, this could be part of the problem, it can create a lot of drag and or binding same with bearings.

 

[fredw90]

Drivetrain is free. I am having an issue where after about a handful of packs, the 4 m3.5 screws holding the ring gear to the diff cup will start to back out. Scrolled across someone on here saying they shoved some m4 screws in there. Worked great till the plastic cup cracked.

Pulled it early enough spiders look to be in good shape still, either way I have new ones on the way and an aluminum diff cup. I’ll make sure everything is clean and fresh throw a little thread lock on and hope for the best.

Now to find some new six packs. It’s a shame they don’t sell them anymore.

 

[Moirae]

Drivetrain is free. I am having an issue where after about a handful of packs, the 4 m3.5 screws holding the ring gear to the diff cup will start to back out. Scrolled across someone on here saying they shoved some m4 screws in there. Worked great till the plastic cup cracked.

Pulled it early enough spiders look to be in good shape still, either way I have new ones on the way and an aluminum diff cup. I’ll make sure everything is clean and fresh throw a little thread lock on and hope for the best.

Now to find some new six packs. It’s a shame they don’t sell them anymore.

Get some mx57 or mashers. Higher quality than duratrax and will give you the driving style you like.

 

[Matt05]

39/47?? What TP is that?

over a year with my 8s rigs and I've still yet to hear a diff crunch. I run 39/47 with a 1070kv and 2 fans. I bash without checking the temps at this point.

 

[SrC]

I tried 30/47 and felt like it was geared too low, it did get hot because I had the thing pinned at full throttle like 90% of the time.

Yeah even too low gearing ( small pinion) , will cause the motor to always spool up to its max RPM's and Hot temps results. Motor is always being maxxed out. Need the right gearing to allow the motor to run its best in both RPM and Torque range. The sweet spot.
Might want to consider swapping to Hybrid Ceramic BB's for the Motor, while you are at it.
And I highly suggest you drop ESC Motor timing all the way down. Advanced Timing creates much motor heat. Double check that. Maybe even trim down some of that Punch while you are at it. Then evaluate from there.
Don't use a Motor Heatsink, if you are. Just a fan "mount" with the fan(s) blowing directly at the the Motor. Best way.

 

[Moirae]

39/47?? What TP is that?

5860 1070kv. It's in my outcast 8s and that motor is 12s capable too. I only did that gearing because I had m2c motor mount which supports it and I was too lazy to put on a 39t spur