raze44

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Hi, I am thinking about scratch building a crawler. I want to put a rc4wd transmission in with two motors but with one esc, I have a esc yhat has a 21-27t motor limit and was wondering If i could run thes in series. Would two stock motors(27t) have enough tourque for a super class crawler? Would the ESC fry? How many batteries can I use.

gotrice

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what esc?

raze44

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a duratrax sprint

gotrice

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That is a lowend esc and i would have to assume that it would fry.

K_B

Running two stock motors in parallel, which the common configuration for running dual motors, is equivalent to running one 13.5T motor (27/2 = 13.5) so the speedo would most likely fail.

raze44

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isn't it the opposite (27 x2=54)?

raze44

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sorry, I meant series

raze44

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Can I run two 12 turn motors in series (12x2=24)? Would it be a bad idea for crawling? Or two 45 turn motors in parallel (45/2=22.5)? Could I also use two 7.2v batteries in parallel? Also, the transmission I am thinking about buying has a 45:1 gear ratio with the supplied pinions, will I need a certain amount of motor turns. Any suggestions? Thanks.

K_B

2 12T motors in series would be a bad idea. 45T motors in parallel would work. But who knows for how long. Two 45s would be pushing the limit of that ESC. If you got your tires in a good bind, the motors could possibly draw enough current to blow the ESC. After all, it is a lower-end speed control. Also, the BEC on that ESC is probably not all that great, so steering will suffer. For that tranny, anything around 45-55T would work well.

You could run two batteries in parallel since the voltage would still be 7.2V. But for crawling, running two batteries is usually overkill since you can get around 1.5-2 hours out of a 3000mah sport pack. The extra battery becomes dead weight.

drevil

My Feedback: (5)

No, running two 27 turn motors is the same as running a 13t motor.


I think you're going backwards about this. What you want is alot of torque, so you'll want a higher turn motor for crawling. 12t motors won't have enough low down torque for rock crawling.

If your esc can handle 21t motors then yes, you can run two 45t motors, though you may want to play it safe and go with 55t motors.

You can run two packs in parallel because the voltage will be the same. However if you were to run them in series the voltage would be doubled and you'd need an esc that could handle 14.4 volts.

sheograth

In either series or parallel, you'll be exceeding the limits of the ESC. In series each motor will only be getting half the voltage drop, and will in turn create a smaller back EMF and thus draw more current. In parallel you're increasing the load as the RPM drops. At load x each motor will be able to turn proportionately faster and thus draw less current, but you loose this effect when the load increases. At any given RPM 2 motors will draw more current in parallel than one motor because the equivalent circuit resistance is the reciprocal of the series resistance. So yeah - either way bad idea if the ESC is not rated for that current.

On a side note I wish more ESCs would simply be spec'd out in terms of current instead of turns, it would make it a lot simpler for those of us who don't think in terms of turns. I design motors and ESCs (non RC), and we'd never speak in terms of turns because of the all the other factors of a motor that affect its current draw. Current draw itself is absolute and has no strings attached.

k, done

s7jstep1

if you really want to run two motors, i say get a dual esc like the novak superduty

raze44

My Feedback: (1)

Thanks.

guver

My Feedback: (325)

2 12's in series or 2 45's in parallel should not overwork the esc.

raze44

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I am not extremely worried about frying my esc, I dont want to end up paying for a hundred dollar novak, or traxxas esc when I can just use my 30$ duratrax esc (it also has reverse). If in chance it dosn't overwork my speed control, what would be better for crawling: 2x 45t-55t motors in parallel, or 2x 12t in series. (The crawler I am planning on building will have a 45:1 ratio transmission, and the Diffs will have appx. a 3.5:1 ratio).

K_B

45-55 in parallel would be best performance wise. If I'm not mistaken, with the motors in series, there will be a voltage drop across the first motor, so the second motor will not get an equal amount of voltage. Without the same amount of voltage, the motor won't spin as fast as the first. And since they're on the same spur gear, that could cause problems.

With around 150:1 final ratio (I think) you could probably get away with one 55T motor.

sheograth

2 identical motors in series will each receive half the total voltage drop.

raze44

My Feedback: (1)

what is a cheap single motor esc that will accept two high turn motors. Also, would it be easier, or worth my while to get another esc, and run two of them with one bettery. The reason Im asking is that the crawler I am going to build will be enough money alone, so I dont want to spend alot on electronics, but at the same time I dont want to sacrifice performance for cash.

gotrice

My Feedback: (5)

I think you would be better off gettting another $30 ecs and a "y" harness to connect them.

raze44

My Feedback: (1)

if i had two ESCs, would two stock motors be ok with a 150:1 gear ratio roll out. Would it take up more power?

603kid

My Feedback: (35)

If you want to run dual motors off 1 ESC you need to use a heavy duty type like the Novak Super Duty, EVX, Rooster Crawler or a Tekin Rebel 2. Most others simply can't handle the draw...look for a minimum BEC rating of 6V 3A or higher. The best way to wire it up is to run the motors in parallel. I wired my rear motor first to the ESC, then wired a jumper from the rear motor to the front. You can either reverse the timing of the rear motor, or simply wire the rear end of the jumper backward. There are theories that if you wire the rear motor first, it helps with Clod stall, but the only true way to get around that is to set up dual ESC's. The Super Duty I ran last season is very smooth, and will handle anything you can throw at it. If you need to run a single battery with the Super Duty you simply remove the positive wire from the first battery lead, and jump the negative lead to the open positive terminal. Keep in mind that if you run lipo the only ESC that has voltage cut off is the Rooster CE. Keep an eye on your run times if you don't use an external cut off with the others.