Rustler 8s/9918: gearing/cells?

[kulangflow]

Howdy!

I finally bought the 8s! Now I have a quick couple of questions:

(I've done a bunch of research on this site, but I haven't really figured out a definite answer to my exact situation, so here goes:)

1) For high speed runs, what's the hottest gearing (32P) and highest cell count I can use without blowing anything up? (I figured out that I'm pretty much limited to a 60T spur due to space limitations. Correct me if I'm wrong. Maybe I should switch back to 48P?)

2) Same question about gearing and cell count, only for bashing and long runtimes.

(Background info: I run GP3300 cells, and my Rustler is stock except for: MIP CVDs, RPM bearing carriers, UBEC, Swami Wheelie Bar, Road Hawg tires, M8 radio, and an aluminum idler gear.)

Thanks a ton for your help!

Brian

[captain harlock]

Well, you might need to get back to 48p so you can use a more precise gearing. How many cells are you going to use? What speed are you aiming at?

[kulangflow]

Thanks for your reply, Cap'n! :-)

Cell counts: anywhere between 1 and 30, I just need to figure out which cell count is most appropriate for this motor on this vehicle. Coming from a 12 lb e-maxx, I know that a 9L is best with 14 cells, while a 10L is best with 16 cells. I just don't know what's okay and what's too much for this 8S on a lighter weight rustler.

(If it helps, my rusty weighs 3 lbs, 13 oz w/o cells and 4 lbs, 13 oz with a 7 cell pack.)

What speed? Good question. I pretty much want to find this part out by pushing this motor to its limit, but without going over. I regularly hit 45mph with my e-maxx/9L. I'd love to see 55 w/ my Rustler.

Thanks!

Brian

[captain harlock]

Okay, use 9-10 cells with a gear ratio 11.8:1 and watch the temp of the esc and your motor. The motor should not go beyond 100 deg. Cels. and the controller would stay cool by using a 12 volt fan. Your 8s will take you beyond 58mph easily at 12 volts, so maybe 9 cells will keep your truck at high speed and under control as well.

[kulangflow]

Thanks again! I am definitely headed in the right direction now.

Got another question:

What gear ratio should I be aiming for with more conservative cell counts like 6,7, or 8 (for general bashing purposes)?

Should I stick to the 11.8:1 regardless or is that only for 9-10 cells? Is the 11.8:1 the tallest I should attempt regardless of cell count?

I don't mind experimenting to find out, but I'd rather learn from others' experience if it's already been determined what's best for this application.

Thanks again!

brian

[nbcaznmaster]

lol, 9918 is overkill for ur setup! good luck though! If u wanna get a diff esc, u could always sell me ur 9918! lol

[captain harlock]

Well, with brushless you can always gear higher, but you can only do that if you are mostly bashing and not racing. Once you notice that the esc is thermalling( does not work or deliver power) you must try things like cooling fans or lower gear ratios to keep the esc and motor in a moderate temp or slightly lower than -very hot- this way you will keep the setup safe and far from wrekage. BTW, the gear ratio that I gave you is a suggestion, but not a recommendation. I'm currently using 9:1 in my T4 with the 9918 and Lehner 1920/8 motor and 11 cells. My gear ratio should be gone a little lower, however.

[MetalMan]

If you want to hit 55mph, you need A LOT of space and good radio range. Back when my BL controllers weren't burnt up, I was using 4s Lipo (14.8v) on a Feigao 12s motor (so at full throttle the motor was spinning ~40,000RPM). I did many speed runs, and in a space of about 200ft., I got to 56.6mph (this distance included braking distance), and was GPS tested. So, if you want your Rustler to go really fast, you need a huge open area to it in where your radio won't glitch.

With the 8s, you should not exceed 9 cells for bashing. For better efficiency, 8 cells would be best. Whenever you change cell counts, you should change gearing to keep the motor in its good temperature range. To find the best gearing, it is best to just experiment, as differences from Rustler to Rustler can make gearing of one motor could make another motor heat up too much.

[kulangflow]

Thanks a ton for all the great info!

Today I tried 10 cells at 18/84 (12.7:1) and 20/84 (11.4:1). After several high speed passes at 20/84, the motor was 170F, while the 9918 was 130F.

At 170F, I couldn't keep my finger on the motor, but that's still less than 100C, so that's okay, right? If these temps are okay, does that mean I could possibly go to a higher pinion like 22 or 24T?

With that said, how hot is too hot for the motor and controller? What is a good temperature range to make these things last me a long while?

Thanks!

Brian

Hey kulangflow, how do you like that 9918? Can you post some pics of your setup? I have the 8s too and I am running the MGM 8012.

Josh

[kulangflow]

I really like the 9918. I've been running it with a 9L in my e-maxx for about a year now. The 9918 has never thermalled or given me any problems. I also have a Schulze 18.97KWF, but it seems to cog a lot more than the 9918, so I'm just going to sell it.

I'll have to come up with some pics.

Word.

[captain harlock]

No, dont go higher in gearing at all, but try to drop a teeth or two from the pinion and measure the motor and esc heat once again.

[kulangflow]

Originally posted by bigair78
Can you post some pics of your setup?

pics granted! :-)

[captain harlock]

Hey, Kulang, these are the Acer Racing battery connectors, right? does it feel any better than the deans connectors.

[kulangflow]

I've never heard them called Acer before ... usually Anderson or PowerPoles.

I really like them though. I've used Deans for a long time, but I'm converting everything over to PowerPoles. They're much easier for my fat fingers to connect/disconnect.

Also, they're ideal for brushless applications, because you can connect red to black to change cell counts in series without needing a y-harness. Like, for this Rustler, I have an 8 cell pack and a 2 cell pack built for it. When I'm just bashing, I use the 8 cells, and when I want to do a speed run, I can throw the other two in there in mere seconds.

Another great advantage is that they're cheaper than Deans, and you can buy as many as you want in one package. Also, I can solder them on much quicker and don't need to use any heatshrink.

Can you tell that I love these things? :-)

Can you offer me any suggestions on my set-up? Like, should I shorten the blue wires from the controller, or will that make a difference? Can I bend the three hard wires from the motor a little more, or can that cause damage? Also, is there a better way to mount my controller?

Thanks!

Brian