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  1. #1
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    What's the theory behind the dual motors?

    This has been itching my brain for awhile now, so just gonna ask.

    What is the benefit of twin motors driving a single spur gear such as on the E-Maxx?


    What I do know is that it doesn't magically double the top speed, just like how having a computer with two 2 Ghz processor cores doesn't mean you're processing at 4 Ghz.


    Does it provide more torque? Does it make it so they don't have to work as hard? Does it increase speed at all or just acceleration?
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  2. #2
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    it makes it more of a PAIN to set up pinions, i know that... i am just waiting for my titans to fry so i can swap in the 775.

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    Last edited by ksb51rl; 05-27-2010 at 04:40 PM.

  3. #3
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    im thinking its cost cutting personally. with how much issues the motors overall seem to have, and how as soon as you start upgrading those 2 motors are usually one of the first things to go. also... people need to buy replacements more with 'easily broken' parts so its a way to increase profits.

    but I could be wrong!
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  4. #4
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    dual motors gives you heaps more torque

    no extra speed

    just quicker to get to the top speed

  5. #5
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    oh yeah, and cos u running dual motors, it will suck the life out of your batteries like theres no tomorrow

  6. #6
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    So it's primarily just for a torque increase then. I suppose that also means it lessens the stress on each motor because they don't have to work as hard to get up to the speed they're capable of.
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  7. #7
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    I thought the 775 produced more torque than the dual 550's. True/false?

    Seeing how well the 775 performs in the Summit, if I had a brushed Maxx and wanted to keep it brushed, I'd make the conversion, too.
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  8. #8
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    Yes, a single 775 is much better than the dual 550s in every category.

    I was just asking in general. Like there's the dual 700 HOs or dual VXL systems in the E-Maxx. I've even seen a youtube video of dual Mamba Monsters. So I was curious what the real benefit of doubling up a motor is.
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  9. #9
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    i misunderstood the question lol.

    indeed, more torque with a lesser motor, by doubling it.

    speed is based on the power (acceleration) and rpm I believe.. so the motors max rpm and its ability to reach said rpm regulates speed, whereas 'torque' is just how powerful the motor is.

    or i could be retarded :-D
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  10. #10
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    Basically you are taking a motor that is to weak to power the vehicle itself and putting two of them in tandem to get the desired results. With a 775, Dewalt, or 1/8 bl system they have enough torque and are powerful enough by themselves. For Traxxas using 2 550's I think it is a price thing and I'm guessing that they get the dual 550's for less than 1 775, but I'm just guessing.

    I've heard of someone doing dual MMMs, but the results were hardly any better than a single. One by itself has so much torque and power that adding a second just spun the tires, wheelied uncontrollably, burned slippers, and broke drivetrain parts.

  11. #11
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    Voltage = top speed, amps = torque and acceleration. More voltage gives you more RPMs and more amps allow the motor to increase RPMs faster.

    This is just my opinion by I think the dual 550s were just part of the learning curve. The Emaxx is the only one that came with them. The Summit which came later and is heaver only has a single 775 motor. Like I said Jmo.

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  12. #12
    RC Turnbuckle Jr. streetdemon's Avatar
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    The E-revo that is brushed comes with the dual motor deal too. Having worked/working in a hobby shop for a while now, younger kids LOVE to see the two motors sitting in the truck. They think it's the coolest thing ever. And I have to admit I had an original E-Maxx and I thought the dual motor thing was so cool.
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    Like what streetdemon said, the Erevo has 2 motors. I'd like to add that HPI's E-Savage also has 2 motors. Tamiya trucks, some of them, have two motors, however it's 1 per axle, but it is still 2 motors. Some people love 2 motors, they think it is cool; it's a marketing gimmick. But to give credit where credit is due, two weak motors is better than one weak motor!
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  14. #14
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    Yeah I knew some trucks use one motor per axle, I was more concerned as to why you'd put two on one spur gear for the entire driveline. I guess one on each axle can accomplish the same thing with lessening the load and increasing torque output.


    I can also see the marketing standpoint on it. People do like seeing increased numbers between products, so that really helps sell things I bet.


    So basically, from the practical standpoint, how powerful or weak a motor is aside, it's meant to help increase torque more than anything.
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    One motor per axle has it's drawbacks. Say for example you what to wheelie. If you put the truck up on the back wheels, you're only getting the power of one motor.
    I like the idea of two motors working together through one spur better. If you have a 4WD 1:1 car, you have one engine powering front and rear wheels, not 2 engines - 1 on the front wheels and 1 for the rear. It just makes more sense to have the total power going to all 4 wheels from one source, ie spur.

    I think you're right, it's meant to increase torque more than anything. It doesn't increase top speed, unless you gear it to use the extra torque and turn that into rpm at the wheel.
    It probably has some effect on efficiency too. Two motors working at their optimal range is bound to be more efficient than one motor working flat out to achieve the same thing.
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  16. #16
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    Very good point actually, the rear axle motor would be almost constantly doing more work than the front. Acceleration makes the trucks lurch backwards, reducing the front wheel's grip on whatever surface. Sounds highly inefficient to me, not that I'm an expert on it.


    I definitely prefer single motors wherever possible. Less power usage, less weight, less complexity and less that can go wrong. I was very glad to ditch my 550s before they had a chance to kick the bucket.
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  17. #17
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    Quote Originally Posted by timie1
    Like what streetdemon said, the Erevo has 2 motors. I'd like to add that HPI's E-Savage also has 2 motors. Tamiya trucks, some of them, have two motors, however it's 1 per axle, but it is still 2 motors. Some people love 2 motors, they think it is cool; it's a marketing gimmick. But to give credit where credit is due, two weak motors is better than one weak motor!
    MOA - Motor on axle is more torque with two motors but not a marketing gimmick. The result is lower center of gravity (CG) and the ability to DIG without having to disengage the transmission from the axle feeding the free-wheels.

  18. #18
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    Quote Originally Posted by nitrochulo
    MOA - Motor on axle is more torque with two motors but not a marketing gimmick. The result is lower center of gravity (CG) and the ability to DIG without having to disengage the transmission from the axle feeding the free-wheels.
    I'm sorry, you lost me.
    What is DIG?

    About the gimmick, I meant two motors driving one spur. A motor on each axle is not a gimmick, it's actually a clever design, but it does have some drawbacks.
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  19. #19
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    For rock crawling (which nitrochulo is referring to with DIG) MOA is better. Say you are sitting on a steep slope and need to get up it. With full time 4wd if you were to "gas" it you could grab and then roll backwards if the slope was steep enough. With the options of two motors, you can engage ONLY the front motor and use it to safely pull the truck up and over the obstacle, or depending on how sophisticated the setup even get the front wheels turning pretty good and have the rear operating on a percentage of the front so they assist but won't over power the truck, causing it to flip. For Monster trucks I prefer the 2 motors on one spur (if one motor isn't an option) but for any kind of crawling MOA is the way to do it.
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  20. #20
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    That's one thing I hate about climbing objects with my E-Maxx. Being 4wd it loves to kick itself backwards instead of pull itself up with the front wheels.

    Would be pretty sweet to be able to selectively choose between front, rear and 4wd power.
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  21. #21
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    Quote Originally Posted by orion
    That's one thing I hate about climbing objects with my E-Maxx. Being 4wd it loves to kick itself backwards instead of pull itself up with the front wheels.

    Would be pretty sweet to be able to selectively choose between front, rear and 4wd power.
    Someone here rigged up their Summit to do just that. In stock form, the Summit has 3 settings for the lockers - open, front locked, and both locked. I can't think of the member offhand, but he has it rigged where he can either run with the diffs open or both locked, and the third setting actually disengaged the rear driveshaft to make the truck front-wheel drive. One of the servos was set up to physically disconnect the rear shaft.

    I'll look around for the thread.
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  22. #22
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    That's pretty cool. Makes me wonder if Traxxas might consider doing that in the next revision of the Summit.
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  23. #23
    RC Turnbuckle Jr. Emaxx2.0's Avatar
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    Dual motors also can handle more weight. The E-maxx is a heaiver truck then it's smaller 1/10th scale bothers(rustler and stampede). 2 550 can easy pull move the heavy weight of an E-maxx vs a single 550 using the same power(duh). And also comparing a 775 to a 550 is like comparing a grapefruit to a kiwi. Now a V-Twin(2VXl) running on 2 2s lipo was very enjoyable and gave me amazing runs. Ran cold to the touch on 17/86 and had over 30min of runtime. It works alittle different b/c each motor is on it's own power source while a stock 2 550 titans share the same power source.
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  24. #24
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    whats the average time a battery last,before it dumps?How many batteries do I need on hand,to have a couple hours of fun?

  25. #25
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    I have just bought a used 3906 Traxxas E-Maxx with the two motor set up-its all stock,and came with 4batteries ,and two chargers.The batteries dump real quick,one back flip,when I hit full throttel,one wheelstand off the driveway,and one drive through the ditch, and then dump,I'm done!And thats with the new pair of batteries-( Wolf Pack 3000mAh 6cell ) I have not even tried the used batteries that came with the truck-( Pirana 1500mAh 6cell )

  26. #26
    RC Turnbuckle Jr. Emaxx2.0's Avatar
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    Quote Originally Posted by GRAMPAJIM58
    I have just bought a used 3906 Traxxas E-Maxx with the two motor set up-its all stock,and came with 4batteries ,and two chargers.The batteries dump real quick,one back flip,when I hit full throttel,one wheelstand off the driveway,and one drive through the ditch, and then dump,I'm done!And thats with the new pair of batteries-( Wolf Pack 3000mAh 6cell ) I have not even tried the used batteries that came with the truck-( Pirana 1500mAh 6cell )
    you're batteries are still too weak. shotgun (aka stick pack) battery construction is sooo nikko. they have alot of resistence and can't suplly full power to the motors. they heat up fast and and give yu lower runtime. The best is side by side construction. They have lower resistence and can supply the motor with more power while giving more runtime and running alot cooler. BTW... upgrade to a higher mah Nimh and go 7cell....you'kll love the power and runtime. Just make sure is a high quality Nimh pack and it being a 3906 E-maxx...you'll have to place the seventh cell in a special location.
    Simply the best. The beautiful Traxxas SRT and TCP

  27. #27
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    I think the dual motors on the e-maxx is just tradtion. The truck has been out ofr a good while. When it came out electric wasn't what it today. everything mostly had a single 540 motor. They just make an electric t-maxx. As the monster trucks are heavier than the smaller trucks onthe market a dual 550 worked best at the time. It gave good mix of cost and performance.

    Remember that RTR are really for new people. Alot of have been in so long the sticker shock is gone. I have spend the better part of the price of an emaxx on upgrades, tires, and bodes in the past few week for my upcomming beach trip.
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  28. #28
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    i think the dual motors are really cool
    Wow how fast is Nitro? Oh WOW..Really..That slow?

  29. #29
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    Cool Just wanted to say thanks

    Quote Originally Posted by Emaxx2.0
    you're batteries are still too weak. shotgun (aka stick pack) battery construction is sooo nikko. they have alot of resistence and can't suplly full power to the motors. they heat up fast and and give yu lower runtime. The best is side by side construction. They have lower resistence and can supply the motor with more power while giving more runtime and running alot cooler. BTW... upgrade to a higher mah Nimh and go 7cell....you'kll love the power and runtime. Just make sure is a high quality Nimh pack and it being a 3906 E-maxx...you'll have to place the seventh cell in a special location.
    Thank you for your time.-jim shaw-(AKA)-grampajim58

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