Why dual motors? other than front/rear dr.
 

I've seen a few pics of guys w/ dual motors on their trannys. I come from the old days of RC, so would someone get me up to speed?
To put it in perspective, my first RC car was a Tamia Sand Scorcher. They had been out maybe 6 months when I got it. Talk about totally water proof cars..... I drove mine under water when it fell through the ice.
Anyway, I raced an RC10 in the late 80s and had my share of monster beetles and bruisers ect.... SO, what's with duals?????:shock:

The board needs a thread called Old Farts how to.:flipoff:

Yeah, I've tried to search threads and figure it out. There's only so many ways to search dual motors......
G

It depends on the turn of the motors, the gearing, and the weight of the rig. A big ole heavy rig can do fine with one low wind motor with a 150:1 geardown. A 55t lathe motor geared 60:1 wont quite cut the mustard in a heavy rig, so two can be used. In a lighter rig, say sub 8 pounds, one 55t motor can do pretty well.

So if I turn my tmaxx into a crawler, I will need duals. But my TLT won't.
I have a integy 65T lathe motor for the TLT. But I digress.
So how do you know the two will be running the same rpms, amps ect, how do you balance them? I'm assuming you would run them in series?
thanks
G

since both motors are conected to the same spur gear they will have to turn at the same speed so there is no worrie there, its not much different than the way a clod can run two motors, there just on seperate gear boxes. Now hears a question, can you wire two 27 turn motors in series and get the same effect as 1 55t or will it have more torque. I think you can run series if both motors are forced to turn at the same speed, without the stalling that a clod would have.

^No. I've tried dual 27's Parallel and series. Neither way has the grunt my 55 lathe does.

Possibly but it depends on weight and if you run more voltage like a 8 or 12 cells v.s a 6 cell pack. More voltage means more power and speed. Integy lathe motors are designed for 12V so running them on 7.2V cuts down on their power and speed.
Correct
As stated above they have to run the same speed because they are turning the same spur gear. They seem to be made well enough not to worry about matching them. Wiring two motors in series will cut the speed in half. It would be better to wire in parallel.

The problem I see is that when you have two motors, one may be trying to turn at 25000 @ 6v and the other at 22000 @6v (power being supplied by esc) The 25000 is going to be dragging because of the 22000 motor. There will be an increase in resistance on the 25000 motor. The extra resistance will cause heat.... At least that's the way I understand the physics involved. Is that something the ESCs can handle or do people have them burn out more when running dual motors?
I get the whole reasons to run them now. Thanks.
Greg

simple solution to the problem, get two motors and two ESC's. use one esc for each motor, simple. if you are going to run two motors with one esc then wire in parallel and make sure you have a enough cells to have enough power.

^ Thats a big waste of money.

If you get two motors of the same wind and contruction, the +- 1% difference between the two motors wont amount to a hill of beans. I am referring to brushed motors.

Two brushless motors cannot be connected on the same spur.

Ahhhh, very cool. I didn't know they only had that close of tolerances. Good to know.
So I'm going to hijack my own thread a moment.
Why brushless? What do you gain from that in a R/C that doesn't see the hard pounding a race truck takes? Also, why can't they use common leads? I know absolutely nothing about these. Other than full size ones..... A little....

Greg

PS, Since the 55T & 65T lathe motors are so cheap, would it be a good idea to have spares sitting around? Or do they last a long time?
I'm really tempted to make my t-maxx a crawler. But man, the money I spent on it seems like it would be flushed down the crapper. Has anyone else done this?

Hey Kamikazi,
have you figured out what the "theoretical" gear ratios are for your 55T/65T combo? I assume the 55 turns a decent amount faster than the 65 does. That's kind of like a real 4wd does. Something w/ a 4.11 ratio in the rear typically has a 4.10 in the front. I am only pointing this out so the non hard core wheelers in the bunch understands my rabbit trail. It's something I am considering if I do the tmx build. That stupid thing always flops over backwards climbing a steep hill.
G

Since the brushed esc's only see a straight dc voltage there is little issue having two on the same spur when they are closely matched (even 5% differences). The slower motor will become a bit of a generater, but the esc can handle it.

With a brushless motor there are three phases to deal with. the slightly slower motor will still act like a generator. The biggest issue arises when one esc gets out of synch with a motor (it happens but it isnt noticable). The still synched motor will keep running while the out of synch motor becomes a full blown generator- pushing three phase dc back into the connected esc (less any motor inefficiencies). A few thousand rpm's (a split second) is plenty of cycles to totally fry an ESC.


Why brushless? Stronger magnets than the ceramic mag'd motors, better power to weight ratio, and the cool factor. You could get a brushed motor that rivals the power to weight of a brushless, but it will be more expensive because of the added manufacturing. Efficiency is a factor too, but a cheap brushless motor is on par with a nice cobalt brushed motor in that department.


I made my t-maxx a crawler. Never looked back.

You guys are killing me...... I'm going to have to do the max now.....

So if I go w/ two brushless on it, I will need two escs - ok, so will I need two battery packs? Is there a splitter "Y" harness for the escs to Rx or is that a custom thing?
If I go w/ the brushed 55 or 65T lathe motors, the Rebel 2 should do fine, correct?
I hate to ask all these questions..... I don't have access to a group of people here that have "been there, done that". Or at least I haven't run into them yet...... I have spent lots of time reading threads too, but my time is up for another three weeks. I'm heading out of state tomorrow.
G

Two brushless requires two esc's, but a clodbuster is the only platform that two are usable. You are better off to get one larger motor and esc, price is around $250 for a nice 2820 outrunner and mamba maxx system.

The Tekin R2 works just fine with two 55t or 65t motors in parallel.

You can always run from one battery, and a y harness works with multiple esc's.