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I've searched for an answer to this for a long time, and I'm hoping I can get some help here. I'm working on a Technic car that uses PF motors to be a mobile vehicle. However, I've found time and time again that the model ends up being just too slow for my liking (if anyone has owned the 4x4 Crawler set, you know what I mean by slow). I own 2 L-Motors, 5 M-Motors, 1 XL-Motor. My question is: How do I make the model have faster speed without it looking like a skeleton car, and also, does adding additional motors increase power? For example, if I gear together 4 M-Motors so that they all end up on one drive axle, is their power combined?

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What type of vehicle are you thinking of building? - If you're building a normal car, then it should be easy to get enough speed (even just with a L-motor); however, if you're building a crawler, it will be harder to increase it's speed without decreasing it's crawling ability.

7 minutes ago, Shadow_ninja714 said:

if I gear together 4 M-Motors so that they all end up on one drive axle, is their power combined?

Yes, but they all need to be geared the same. (unless you use an adder mechanism)

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Just now, mocbuild101 said:

What type of vehicle are you thinking of building? - If you're building a normal car, then it should be easy to get enough speed (even just with a L-motor); however, if you're building a crawler, it will be harder to increase it's speed without decreasing it's crawling ability.

Yes, but they all need to be geared the same. (unless you use an adder mechanism)

I literally just saw this in another post about drivetrains for heavy treaded vehicles. Could you explain the adder/subtractor concept?

Also, it's a full-size car, similar to the post of the Koenigsegg One:1. The weight becomes a problem with speed.

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Just now, Shadow_ninja714 said:

Could you explain the adder/subtractor concept?

Put simply, a subtractor combines two (or more) motors in a way that makes it easier (and simpler) to control a tank; and an adder combines the speed and torque of two (or more) motors to increase power. (however it isn't as efficient as hard-coupling, and it's harder to workout the speed/torque of the output)

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A subtractor unit allows one motor to drive tracked vehicles in a straight line.

When second motor is used in conjunction with first motor it speeds up one track and slows down the other track to allow large radius turns

Second motor used on its own will run tracks in opposite directions so vehicle can turn on the spot. Sariels guide book explains.

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Something else to keep in mind is current draw. You can only efficiently run X amount of motors off of one battery box. Also I think adding motors doesn't necessarily add speed for that I rely on gearing. However adding motors will increase torque, allowing you to get to top speed faster.

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For a car of that size, M-motors will not work. L-motors at the least, XL-motors for the best results. If you could afford them, buggy motors.

For inspiration and to see how it works, check out Madoca's ICARUS Supercar one of the best models with good looks and performance. Plus, FREE instructions!

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4 hours ago, Johnny1360 said:

Something else to keep in mind is current draw. You can only efficiently run X amount of motors off of one battery box. Also I think adding motors doesn't necessarily add speed for that I rely on gearing. However adding motors will increase torque, allowing you to get to top speed faster.

I've tried a single XL motor with gearing down but it's still slower than I'd like.

When adding motors, should I try to just gear them together (such as the motors being next to each other so that they both touch the same gear), or is there a better approach?

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Just now, Shadow_ninja714 said:

I've tried a single XL motor with gearing down but it's still slower than I'd like.

When adding motors, should I try to just gear them together (such as the motors being next to each other so that they both touch the same gear), or is there a better approach?

You are describing hard coupling, this will work and effectively adds the torque. The issue is if the motors, have a difference in their speed, which they will, they work against each other which may in the long run break one or more of the motors 

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Just now, Shadow_ninja714 said:

I've tried a single XL motor with gearing down but it's still slower than I'd like.

When adding motors, should I try to just gear them together (such as the motors being next to each other so that they both touch the same gear), or is there a better approach?

For more speed you need to gear the motor up. However there is a point of diminishing return, where you need more torque to even getting the car to move. That is when you add more motors. Hardcoupling them together works for me just fine without causing damage to the motors, as long as they are the same size. It will not increase the top speed though, may even be slower due to current draw and one motor dragging the other down. Even identical motors often turn at slightly different RPMs.

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Hard-coupling isn't going to do any more damage to the motors than the resistance offered by the weight of the model itself. So unless you plan on running them for hours and provided you use the same kind of motors (e.g. all XLs) then you shouldn't have any trouble.

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