individually powering wheels with L motors

[aminnich]

Hey guys,

I have been thinking about an idea that a EB member told me to try, but im having trouble pondering how to apply it to my model. The idea is to take an L motor, gear in down 1:3, and power each wheel individually. Sounds like a great idea, but im not sure how you could do that in a small space.

I want to use this concept on a 4 axle semi truck (powering the rear 3 axles). So first I need to get 6 L motors, but I need some ideas on how I could do this.

I am use to running an XL motor to the drive shaft, but I have not had experience with L motors a lot.

If you can help me, that would be awesome, keep in mind it is a semi truck, so I don't want to make it too wide.

Thanks!

[Technyk32231]

Maybe longitudinally place the motors, then gear them down after a bevel?

[aminnich]

I have tried that (at least to what I think ur explaining). if you do it that way, their is too much room in between the axles and wheels and it doesn't look so great

[Blakbird]

I'm not sure I understand the question. Gearing down 3:1 only requires a single stage with a 24 tooth and 8 tooth gear. How could it get any more compact than that? Why are you saying you cannot do it in a small space? For example, just use the portal hub. Or look at some of the older portal hubs like in Sariel's Jeep Rubicon where he gears down 3:1 at each wheel.

[aminnich]

I want to have the motors in the rear of the truck, but Im not sure if their is enough room. I was hoping someone would have an idea, and maybe even LDD idea that I could look at.

[rollermonkey]

Why would you want the front wheel motors in the back of the vehicle?

And further, you're quickly going to find out why a differential is important as soon as your vehicle makes a turn.

[aminnich]

only the rear wheels will be powered. I just thought that powering all of the wheels would be an alternative for differentials, but I guess that it wouldn't know that i think about it. But what about the TATRA 8 X 8 vehicles? They usually don’t use a differential, what is the difference. In ZBLJ’s 8 X 8 X 8, each wheel is powered by a XL geared down 1:3. This is the idea I wanted to achieve. (but with L motors)

[BusterHaus]

Maybe this will help: http://www.bartneck.de/2013/05/03/race2/

It's direct drive, but 6 motors may be strong enough to move your truck.

[andythenorth]

And further, you're quickly going to find out why a differential is important as soon as your vehicle makes a turn.

In the case of both wheels powered by one motor yes, a differential is needed.

In the case where one motor is used per wheel, the differential is not needed.

@aminnich, my truck has the L motors offset either side of the centre line of the axle. Mounting them to a 5x7 square frame results in a very strong assembly. I have two sets of reductions, and the portal hubs, for a total width of 19 studs between the wheels.

You only need one reduction, and for the wheels you're using, you don't need such strong hubs. I think it can be done with 13 studs between the wheels. For comparison, the 8285 tow truck uses the same wheels you have, with 11 studs between the rear wheels (which are double-tyres). For a heavy haul truck, that would be ok. I think you could even fit in primitive suspension (oscillating axle or walking beams).

I don't have a good picture, but you can just see the L motors on the front axle in this picture.

Don't be misled by the huge tyres I'm using, they actually demand quite a narrow chassis, and the truck in the picture is not much wider than the 8285 truck.

I'll try and post better pictures later.

Edited December 23, 2014 by andythenorth

[Rockbrick]

direct drive the wheels but use the 'train set' remote with the variable speed as 'gearing', the L motors should have enough torque for this

Edited December 23, 2014 by Rockbrick

[efferman]

I think My big G is a good example for what you want. even when you want unsteered axles.

http://www.brickshel...ry.cgi?f=510957

101_9501 by efferman, on Flickr

but i have to ask which tires do you want to use and which power source do you want to use? for six PF-L i recommend two battboxes with servo operated switches.

Edited December 23, 2014 by efferman

[aminnich]

Thanks for all the recommendations everyone.

To answer efferman first, I am using the same tires that are on the 42009 mobile crane. I am going to use 2 battery boxes, but I don’t know what you mean by a servo operated switch. Your idea, looks like a good one and I will have it try it out.

Busterhaus, I also like your idea, I like that the motors are right at the wheel (sure I would have to move it up and gear it down, but ya well). The only thing im not sure about with it is how wide it is. The motor is 7 studs long, so 14 plus the wheels, that could be pretty wide. I will try it out though

Andythenorth, I like your design the best, have the motor kinda side by side. I cant quite make out how the gearing is done inside, so if you could post a more detailed pic, that would be awesome.

[efferman]

you are using the 62x20 tires also the width of the truck will be around 19 studs?

[BusterHaus]

Here's a quick build of what andythenorth was talking about. http://4.bp.blogspot.com/-yV2IVbYxGi8/VJmQdfKeU5I/AAAAAAAAAnI/_y_r68HFnkA/s1600/IMG_20141223_105235.jpg

I think you're better off with a beam on each side of the gear.

[andythenorth]

Picture quality is poor, but I disassembled the Rolligon a bit to show the structure:

https://www.flickr.c...57649485436319/

- you don't need the portal hub with 8:24 gear

- you do need the 12:20 gear in the triangle half-stud liftarms

- the half-stud liftarms are the key to keeping it strong whilst keeping the gears meshed.

- not visible in the photos are half-pins which attach the motor to the nearest triangle liftarm. http://www.bricklink...tem.asp?P=32002

- also not easily seen, but these parts are used to mount the motors http://www.bricklink...tem.asp?P=48989

You'd need to adapt my design a bit, but not a lot. You mount the wheel on the same axle as the 20t gear, with a liftarm (dunno which part) braced from the 3x5 L liftarms.

Mine has two axles on parallel walking beam suspension, which gives it a high rough-terrain capability, but you don't need a lot of suspension for heavy haul (and it will tend to hop under load if it has too much suspension).

EDIT, oops, you may find you don't have enough ground clearance with this design in combination with your wheels (wheels may not even touch ground) Probably solvable with more thought (move the motors to the bottom of the rectangular 5x7 frame, instead of the center?).

Edited December 23, 2014 by andythenorth

[aminnich]

wow, u guys are great

efferman; I am using the same tires as on the 42009 crane (not sure what the number are tho)

busterkhaus; that is the idea i wanted to use

andythenorth; thanks are taking apart your model to show me. I will have to modify your design because of ground clearance, but it is a good source for an idea. Brickhaus's picture is more what i was thinking.

I also noticed that you gear it down 1:3 twice, do you think i have to?

Edited December 23, 2014 by aminnich

[andythenorth]

I don't think you need the second reduction with your wheels. They're 62mm vs. 106mm on the wheels I'm using. Smaller wheels = lower rotational speed, higher rimpull torque, no need for the extra reduction. I didn't do any maths to check it mind. You can try 12:20, 8:24, or 16:16 gearing to get the best combination of speed and torque you want (it will always be a compromise between the two). I'd build a rough test rig when you get the motors and see what it pulls.

Brickhaus's mockup is much simpler than mine, which is good. If you don't need suspension, then you don't need that kind of super-strong live axle.

If you can use thin liftarms though either side of your gears, you'll save 2 studs width.

Edited December 23, 2014 by andythenorth

[aminnich]

ok, this is going to sound like I have know idea what im doing, but I only really know 1:3 gearing. and what do you mean by using thin lift arms on either side? if I do that I wont have much room to connect the motors to the rest of the chassis and body. I mean sure the 2 studs would help, but I am not sure that it would be beneficial. unless you have a solution. THX again

[andythenorth]

Gearing: so you have a range of gears available. 3:1 is the 8 tooth gear with the 24 tooth gear. You can also use the 12 tooth with 20 tooth (1.667:1), or 16 tooth with 16 tooth (1:1). All of these fit the same stud spacing.

The thin liftarms: if you look at my pictures, there is reduction with a black 12t gear and a tan 20t gear. These are trapped between two yellow triangle liftarms, which are 'think' or 'half-width'. You do need to trap the gears between two liftarms (or they'll slip), but you don't need to use 'thick' or 'full-width' liftarms.

In this picture one of the two yellow triangle liftarms is removed so you can see the gears https://www.flickr.c...157649485436319

It would normally trap the gears, and be held in place by the red 2-long axles (which are poking out the back of the yellow liftarm that is left in place).

EDIT I've ordered some L motors, because I might try and build a truck like this now you've got me thinking on it. Won't be until after christmas though.

Edited December 23, 2014 by andythenorth

[aminnich]

Ok, but their is not much to connect to if you are using thin liftarms. I understand what u r saying, I am just not sure how to apply it.

Haha, i have to order my motors yet. hopefully Christmas brings some

I looked at the picture, i see that you can connect the chassis to the red 7 long liftarms that you have at the ends of the thin liftarms.

Edited December 23, 2014 by aminnich

[pcfw]

If you have the Lego Wedo hub and software or MIT Scratch software, you can control individually 2 or more motors. Details with screenshot, photo and video explain how to at

How to label and control separately 2 or more Wedo motors

I don't yet have Lego Mindstorms but you can do the same without wire

[Boulderer]

If you have the Lego Wedo hub and software or MIT Scratch software, you can control individually 2 or more motors. Details with screenshot, photo and video explain how to at

How to label and control separately 2 or more Wedo motors

I don't yet have Lego Mindstorms but you can do the same without wire

I don't believe that Wedo or Mindstorms are applicable to this particular thread, which is relating to PF vehicle design.

[aminnich]

You are correct, this is strictly a pf vehicle design.

[pcfw]

Sorry i am new around here. I just read that part about controlling 2 motors.

[Boulderer]

Sorry i am new around here. I just read that part about controlling 2 motors.

No problem :) It's always good to see a new view point brought to forums. I, for one, had not really been aware of the Wedo range until you started posting so, thank you.