RC-Monster Forums - Gearing/Battery choices; gear up or increase voltage

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Gearing/Battery choices; gear up or increase voltage

So I have settled on the ESC/Motor combos to use on my vehicles. Thanks to those that posted in my other thread.

Now I need help on gearing and battery selection.

1. SC10 with Sidewinder SCT system
-was thinking 2s initially, but playing with the speed calc it won't be fast enough on stock gearing. Castle's gearing guide does recommend anything higher than 18t pinion. Should I jump to 3s to stay within Castle's recommendation or can I gear up?

2. Mini STe with MMPro SCT system
-was going to run on 3s, but playing with the speed calc it would not be fast enough for me. To get the speed I'm looking for it would take an 19t pinion which is way out of Castle's recommendation of 10-13. Should I jump to 4s to stay within Castle's recommendation or can I gear up?

I know the line of thinking is higher voltage is better for the ESC in terms of reduced amps. The only concerns I have are battery dimensions and capacity/runtime. For example I can get a 3s 5300mah battery that will fit in the STe. If I want to go 4s I need to go down in capacity, from 5300mah to 4000mah. What kind of reduction in run time am I looking at?

In the SC10 I need to go down in capacity as well if I want to keep the stock battery retention system, although some slight mods and I should be able to use the 5300 3s pack I had planned to use in my STe.

Both will be used for bashing in fairly open areas so the trucks will be able to stretch their legs. I was wanting 35-40 for the STe and on 4s a 14t pinion will get me 37mph and 16t yields 42mph. To hit 37mph on 3s I need to use a 19t pinion.

The SC10 RTR brushless stock should be good for 23mph, well if what I saw was 23mph I need something a good bit quicker. I thought the bump in kv from the castle motor would satisfy this, but it seems that extra 500kv only equates to another 3mph for 26mph, not enough. Going up to 3s will get me at 39mph on stock gearing, perfect.

http://www.scriptasylum.com/rc_speed/power.html

Enter in the battery you are currently using, and the approximate runtime you get, and the calc will output info on what to expect with batteries of different voltages and capacities.

Quote:

Originally Posted by simplechamp (Post 397597)

haha don't know how I missed that. :oops:

Thanks for the link. I see that a 3975mah 4s pack yields equal runtimes as the 5300mah 3s assuimg weight and speed are kept equal.

Yeah I had been using that calc because I'm kind of looking at a similar situation as you right now. My 1/8 GT is setup to run a saddle setup with 2 packs. I can run two 2S 5000mah, but if I want to run two 3S lipos I will have to go down to about 3000-3300mah max capacity for the packs to fit.

The calc says running the 6S 3300mah setup should give me the same runtime as the 4S 5000mah. And that makes sense as the packs have to be about the same physical size and weight to fit the lipo trays, and because of that they have the same amount of lithium polymer "media" inside, storing the same amount of overall energy. At least I think that is why? Makes sense to me at least.

For now I'm sticking with the dual 2S setup just because I have a bunch of matched 2S packs already. But eventually (most likely once the 2S packs start to lose their punch) I will try some 3S packs. Dynamite has some 3S 3200mah hardcases that I would like to try, but I also want to try Gens Ace.

Stolen from Drknow on rctech

Quote:

To run high wattage (power) on 2S it's going to be a high amperage situation. Watts equals amps times volts. You need to use the larger Mamba Monster ESC. ROAR nonsense pretty much dictates that your going to be running some poor ESC right on the ragged edge of fire no matter what ESC you use if you want to put down high power on 2S.

You could do the same wattage at a higher voltage (3 to 6S) with the MMP, but it doesn't have the amp rating to do high wattage on 2S. You could gear down and run a ROAR legal can with less wattage than the 1410 or 1415 on the MMP. Seems like a lot of guys are using the 5.5 550's on 2S with the MMP, but it's less power than a 1410.

I think I need to put this in my signature... example

watts (think horsepower), amps (think heat)
1000w at 7.4v (2S)= 135amps (hot)
1000w at 11.1v(3S)= 90amps (medium)
1000w at 14.8v(4S)= 67.5amps (low)
1000w at 22.2v(6S)= 45amps (cold)

This is why ROAR needs to allow 4S. You could run a 4S 2650mah batt that is the same weight as a 2S 5000mah batt (but it would need 1/2 the C rating), run a 2300kv motor that is the same size as a 4600kv motor, and use the same ESC but it won't run hot... making THE SAME POWER WITH THE SAME WEIGHT AND RUN TIME!
This is why so many tracks are not sticking strictly to ROAR BS.

I would go with 3s on the sidewinder sc system. The sc10 is 2wd, correct? If so it should be similar weight to my pede 2wd, and I run 3s with the sidewinder sc. I am geared for about 45mph and nothing even gets warm. The esc is anout 80f and the motor is no higher after 30mins. This is a great 3s setup for a 2wd 10th scale and would be killer in a 10th 4wd tc. Way to go castle!!!

As for the other truck, I am sure 3s and higher gearing will be fine. I ran mine with a 1509 neu on 2s lipo with a MM. Not sure on gearing but it was a 6500kv motor and I geared for mind 40s. You really want to keep the weight down in the ste, it is not a really heavy duty truck, and the suspension works better if it is keep light weight. A 3s 5000mah pack should be just fine.

Quote:

Originally Posted by lincpimp (Post 397687)

Yea the AE SC10 is 2wd, glad to here the temps are so low on 3s with the sidewinder SCT.

Intially I planned on gearing up with the STe esp. with the 1415, but once I saw Castle's gearing PDF for the hyper 10SC, very similar gearing wise to the STe, I started thinking I might be over gearing jumping up 6 teeth.