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i have a dumb question

Old 10-15-2014, 01:56 PM
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aminnich
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Default i have a dumb question

I built a trailer for my RC car but it doesnt have enough torque. Right now im running a 4000 kv motor with a small (stock) pinion gear. I have a 20T motor laying around at home and was wondering if that would give me more torque. Now for another dumb question, if I put a larger pinion gear on with the 20T motor, would that just defeat the urpose of putting on a different motor???
Old 10-15-2014, 07:14 PM
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cumquat
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need to know what vehicle is pulling and what is on the trailer.
Old 10-16-2014, 05:07 AM
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aminnich
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the vehicle is a ruckus with a 4000 kv motor. the trailer is made of knex, weighs about 6 lbs
Old 10-16-2014, 11:38 AM
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well there's your problem. you're using a 4 pound truck to pull a 6 pound trailer with quite a lot of rolling resistance. not to mention the motor is good for 5 pounds max, yet it's being asked to move 10. that 20t motor will not do any better. you need something more along the lines of a <3000kv 4 pole. what makes the trailer so heavy?
Old 10-16-2014, 11:40 AM
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cumquat
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something you could try to do is add power to the trailer, but i dont know how well that would work.
Old 10-16-2014, 05:04 PM
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well...

its a combination of, power to weight and the final drive ratio....
by the sounds the power or weight can be changed with out spending but bucks or making thins lighter so the only other option is gearing.

those motors can be around 1hp... and 1hp is defiantly enough power to move the weight u want but... u will potentially loose a lot of speed

First thing I would check is what possible gear ratios are there for that vehicle?
because that will let u know if it can be geared low enough with just a new pinion and spur or will it require a external gear reduction unit.

just keep in mind, when its setup to tow it will loose most of its performance.... ie top speed will be greatly reduced
Old 10-17-2014, 05:03 AM
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yep, with a 4000kv motor and stock gearing you are trying to move double the weight intended. If you want to stick with the 4000kv motor, you will need to run a much small pinion (motor) gear. Not sure how small a gear can fit, but something as small as a 16tooth might work.

You will have the same issues if you use the stock 20t brushed motor. If you don't mind the truck being slow, you could buy a rock crawler brushed motor (which are cheap) A 35 turn brushed motor might be enough...maybe even a 50 turn. A higher turn motor has more torque but less rpm's. But you might be able to run a crawler motor with the stock gearing.
Old 10-20-2014, 12:05 PM
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aminnich
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sorry for not keeping in touch. The 4000 kv motor does pull the trailer with the stock pinion gear, but not so good. i understand that the tuck wont be able to go as fast. The rock crawler motor sounds like a good idea, but i'm not really looking to spend money, especially since i would never use than motor anywhere else. The small pinion gear is a good idea, but idk if electrix sells smaller ones. Right now im in contact with people that actually know what they are doing when it comes to knex, so maybe they will be able to make it lighter. For those of you that are interested, the trailer is a logging trailer, so that when i go camping i can pull sticks and what not around on my truck. Any other suggestions would b great!! thanks everyone
Old 10-20-2014, 03:06 PM
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I have been looking for different ideas, so i found this....
an axial 55T motor for $20, which is an ok price for me.
Old 10-20-2014, 06:09 PM
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i used to run their 27 turn and it had gobs of power. i was able to gear my evader up so much that it was actually slightly faster than stock (20 turn motor, 88 tooth spur/22 tooth pinion as i recall). i can only imagine how strong the 55 turn is.
Old 10-20-2014, 08:23 PM
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Fitting a lower turn like a 55t won't give u any more power... All it's going to do is give u a ever slight more torque down low, but not as much u think.

example, I had a 55t my scx10.... It was completely gutless and slow.... Turns out. To get decent torque u need to also run a higher voltage. Say 3s and 4s lipo's where I was only running 2s.

like I said the other day, u need to lower the garing. And depending on ur limitations u might need a GRU
Old 10-24-2014, 02:11 AM
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I think you you need something with the lines of a <3000kv 4 pole. what makes the trailer so heavy? what you have to do is that you could try to do is add power to the trailer.

Last edited by RobertHen; 10-28-2014 at 01:44 AM.
Old 10-24-2014, 07:25 PM
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Originally Posted by RobertHen View Post
I think you you need something with the lines of a <3000kv 4 pole. what makes the trailer so heavy? what you have to do is that you could try to do is add power to the trailer.
dude, why did you copy my responses?
Old 10-25-2014, 02:02 PM
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aminnich
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can I please have a definite answer, one person says go for the higher "T" motor, while another says that wont do anything.
Old 10-25-2014, 07:03 PM
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It's true, lowering the number of motor turns will increase torque...not by much tho... And the torque is not proportional in a linear fashion to the turn limit as people would suggest.... Example.... Most people will say a 55t has more torque than 27t.... Me personally. From my tests and experience say no it does not.... The only way it will have more torque is if u increase the voltage. We see this a lot with crawlers.. The common rule for crawlers is the lower the turn the higher voltage u should run to retain torque and rpm.

For towing it's all about the gear ratios..... If u look at a kids ride on car they use brushed motors that have far less power than ur brushless motor and they only run on 6v. They do it via gearing.

so I'm 100% sure, no doubt about it. u could do it via lowering the gear ratio.

Because this is fresh water, it's going to be a little it of trial and error.
Old 10-25-2014, 07:09 PM
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This is what u need.... It will make the pinion gear spin 1/4 slower, and will give u a ton on mechanical torque on top of what the motor currently has. And then u will be able to fin tune the gearing like normal with different spur/pinion combinations

http://store.rc4wd.com/41-Ultra-Comp...or-_p_782.html
Old 10-28-2014, 09:38 AM
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how does something like that work?
Old 10-28-2014, 10:31 AM
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It's a gear reduction unit. output shaft will turn 1/4 as fast as it did with just the motor. Yer gonna have tons of torque, just no top speed.
Old 10-28-2014, 12:36 PM
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ok, but how do u mount it. And I not really looking to spend $40 just pull a trailer I made. I understand I need the gear reduction, but for $40, idk.
Old 10-28-2014, 02:46 PM
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this hobby is not cheap....
Old 10-28-2014, 04:44 PM
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Originally Posted by phmaximus View Post
this hobby is not cheap....
no kidding. my sister-in-law just got a new (to her) Jeep Grand Cherokee for less than what a savage octane costs!
Old 10-29-2014, 10:44 AM
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If you don't want to spend the $40. for the gear reducer, take as many teeth off the pinion and put as many teeth on the spur as you can. phmaximus said it in post 15. "For towing it's all about the gear ratios..... If u look at a kids ride on car they use brushed motors that have far less power than ur brushless motor and they only run on 6v. They do it via gearing.

so I'm 100% sure, no doubt about it. u could do it via lowering the gear ratio." That's where I'd try first.
Old 10-29-2014, 12:06 PM
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aminnich
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I understand that this isn't a cheap hobby, but I don't want to pay $40 on something I'm going to use twice. I'm going to try the gear deduction.
Old 10-31-2014, 12:49 PM
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Not sure how much of this was covered, I skimmed through responses, but here goes my experience:

Higher turn brushed motors will give you more torque, but not in a way that it will matter much. They are much slower speed, which is a drawback in it's own right. For our crawlers most people tend to look for a solid combination of torque and wheel speed, through motor turns, gearing, and voltage. That's why the most common combination seems to be 35t and 3s for an SCX10 (just an example, calm down lol).

If you kept the same battery the whole time, say, a 2s, a 55t or higher will be torquier but will lack the wheel speed to make the most use out of the extra torque, unless you input more volts or run taller gearing, which, taller gearing will negate the torque benefits without the higher volts to offset the losses. Basically, the only benefit to a higher turn motor on the same truck with the same battery will only give you an ever so slight bit of "low-range" power to keep your wheels from getting bound up as much in tight spaces. But not much.

A lower turn motor will basically do the opposite, give you more wheel speed and slightly less torque, which all also has to be offset or modified by other means.

If you still think a different motor will make it all better, then look some more, that Axial 55t can be had for half that price all over, about $10 each is what I paid for my two backup motors. Or, if it will fit and your ESC will run it, look into a Traxxas Titan 12t 550, for under $20 as well.

Anyways, we will use my trail truck for an example. I needed torque for crawling, but wheel speed for trails, and, my favorite, mud. Not puddles, but thick soupy mud. I didn't want the extra weight of more battery cells, as a 2s is just where I like it, so, I went with slightly lower diff gears in the front and rear and ran helical cut instead of straight. Then, I switched from 48p spur and pinion to MOD-1 gearing, and lowered the ratio there, too, so it's actually my driveline itself turning power into torque instead of the motor, and I run an Axial 20t brushed motor. Now, it crawls and muds great, both only dependent on how far you push the throttle. This setup, this past weekend, pulled a 8 pound pulling sled with skid front and 15 pounds weight full pull.

Another truck, stock SCX10 with 27t and weighted wheels, went nearly full pull, as well...

My two questions, though:

1) Why is your trailer, made of kinex, nearly as heavy as our full-steel pulling sled

2) By 4000kv I can only assume you are brushless. Why would your brushless truck have enough problems pulling that trailer that you found your way here? Something doesn't seem right. Your trailer is lighter, and has less moving resistance than our sled with a skid front.
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Old 11-03-2014, 12:40 PM
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aminnich
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I make the trailer out of k'nex because they are easy to use and were available. You are correct to assume that my motor is brushless, but my truck does not have enough power to pull the trailer. I loosened the spur gear and did't move, so a tightened it and stripped the gear clean. So their is definitely a problem somewhere. I asked on this website, because I knew someone would be able to help me, although i know pretty much about gearing and motors and what not, i wanted to make sure with the lower turn ration for the different motors. Thanks to posting!!

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