aminnich

Question for building a semi truck, power functions

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My question is that if I am powering the axle with two XL motors, is it better to power 2 axles/wheels or just 1. Sorry if that is confusing. I need my truck to pull lots of weight. I am also building a low loader trailer that will be hauling the new 42030 Volvo front end loader. So, I am going to need it to have lots of torque, but on the other hand, speed is good too. If you have any other ideas to help me that would be great. Thanks

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If you are gonna pull stuff than you need traction. In order to efficently use the traction of all wheels, than yes all wheel drive is needed. Unless you have a very light front and a very heavy rear, you can maybe afford only rear wheel drive, but generally there are no such extreme weight distrubrutions in Lego models, so I'd go for AWD.

Edited by Zblj

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My question is that if I am powering the axle with two XL motors, is it better to power 2 axles/wheels or just 1. Sorry if that is confusing. I need my truck to pull lots of weight. I am also building a low loader trailer that will be hauling the new 42030 Volvo front end loader. So, I am going to need it to have lots of torque, but on the other hand, speed is good too. If you have any other ideas to help me that would be great. Thanks

I would say gear it down 1:3 or 1:4, that is good for pulling weights. The XL motors will be able to give you enough speed with that, but don't expect it to be fast.

As Zblj said, AWD is better that RWD,so if you can, power all the axles.

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The way my truck is set up currently, I would not be able to power the front axle, the servo and gears are in the way to try and fit in a differential and more gears. Right now I have 2 dual wheel axles in the back, should I make that 3?

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Do you want to haul on level ground, or on rough terrain / places where wheels might slip?

What tyres are you using? You might want to consider 2 XL motors. There is such a thing as too much torque though :)

I'd power both rear axles, if nothing else it distributes the torque across more parts, means less chance of twisting axles, breaking gears etc.

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I am using 2 XL motors and I have not run into the problem of too much power. I am going to be running it on a lament floor, so it will be flat.

These are the tires I am using.

post-60976-0-16201400-1403636736.jpg

Edited by aminnich

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Just FYI, if you're considering realism as an important goal, most semi trucks only have the front of their rear two axles driven. I think that most can drive the second, but think of it like 4WD, it isn't used unless you absolutely need it.

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Just FYI, if you're considering realism as an important goal, most semi trucks only have the front of their rear two axles driven. I think that most can drive the second, but think of it like 4WD, it isn't used unless you absolutely need it.

Where do you get this idea? To my knowledge, almost all semi tractors (at least in the USA) have both rear axles driven.

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I would run both XL motors to both rear axles. Madoca, Sariel, and others have done it this way, and it seems to be the standard setup for twin motor, tandem axle trucks.

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Where do you get this idea? To my knowledge, almost all semi tractors (at least in the USA) have both rear axles driven.

Oh, I think I was thinking of a differential lock, not drive. My bad

Edited by pluto7443

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To be honest, I am more concerned about what it can do rather than looks. But thanks for the tip.

Well in that case, just put an axle with u-joints spread across the top, thereby allowing you to make it AWD.

:laugh: :laugh: :laugh: :laugh: :laugh:

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As the others said, two XL. I asked about the tyres because it's a good guide to the size of the vehicle. For the size you're using 2 XLs on double-drive tandems should work well.

On smooth level ground you won't gain much by going to a tri-drive.

Doesn't really matter if you use one motor per axle independently, or both motors are connected together. The more gears you have, the lower the efficiency of the drive train though.

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This truck has 1 XL motor per rear axle, and 1 XL for the front 2 axles (so 3 XL in total). The wheels are a little larger than the ones you're using. It uses 2x AA battery boxes, positioned over the rear axles for weight. Rear axles have diff locks.

It will:

- pull a 15KG child on a scooter + a load of toys on a rough slate floor

- push a kitchen chair around a smooth wood floor

- climb a 5cm vertical obstacle (with the diff locks in)

Hope that's useful guidance :classic:

14085396420_0eac3bcfa7.jpg

8733756523_7cfbb75cd2.jpg

8733756723_446ace0a6b.jpg

Edited by andythenorth

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Thanks everyone for your advice for me and my truck. I'll be trying out all of your ideas sooner or later. But, I do have another question. If I were to independently power each axle (2 axles) is their another way of doing it other that having the motor on top of the axles like shown in the pictures shown above?? I have a hitch there and their is not much room. Any help would be great.

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Move the motors down and inline with the wheels. One will go in front of the lead axle, the other goes either between the rear and lead axle, or behind the rear axle (which might be too long). You can move motors further away, but this needs more transmission parts, which are a weak point.

You could also try the L motors. L motors are not nearly as powerful as XL but they are still pretty good. They are longer, but not as wide, so might fit better to your chassis.

Edited by andythenorth

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If I would put the Xl motor in between the axles I would want them to be long ways, so now I will have a bigger gap in between the axles. I like the idea, it will be tried. But will two motors powering each axle without gearing down be enough power to pull a heavy load?? I don’t know. My original plan was to have 4 total xl motors, 2 of them would be powering a differential and same for the other two. Then that output of a total of 4 XL (lots of torque with original speed) would power the two rear axles, also with differentials. The only problem with that is, I need more differentials. :hmpf_bad:

I will be testing out that new idea. Thanks again guys.

Edited by aminnich

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4 XL is overkill :grin:

You will either:

1. lose traction, with the wheels spinning (can be fixed with more weight above the drive axles, e.g. batteries or such)

2. if you can maintain traction, but you have a large enough load to stall the truck, the torque of the XLs will just destroy the drive train, most likely the 12t bevel gears in the diff.

If the trailing load isn't very heavy (and I would guess 10-20KGs as 'heavy' in this context), then there is less chance of stalling out and destroying the drive train. But it's still overkill :wink:

If you try and balance two XLs on either side of a diff (in theory this sounds good and gives variable speed), then the motors destroy the bevel gears in a matter of minutes. :wink:

Edited by andythenorth

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