Multiple motor drive systems

[Seasider]

Got the PF bug now so thinking of making an MOC and I know a lot of people use multiple motors.

So excluding the rc buggy motor what is a good motor set up if I wanted to make a "fast" rwd vehicle, pictures most appreciated. I have multiples of most modern technic motors except the rc motor which I don't have at all. And I have a good selection of gears, suspension arms, u joints and hubs/knuckles (bits that attach the wheels)

So suggestions please

[DrJB]

If the motor runs too slow for your needs, the best/trivial approach is to 'gear-it-up' i.e., attach a large gear to the motor, and have that gear drive a smaller gear, attached to the wheel(s). Keep in mind though that, if you up the speed (with gears), the max torque will go down by the same factor. The change in speed is exactly the same as the ratio of number of teeth. Is this the kind of answer you're seeking or is that just too basic?

Edited February 19, 2015 by DrJB

[Seasider]

I'm aware of the gear torque vs speed issue. But I'd notice a few MOCs that use multiple motors for the drive. Curious how they are linked or not

[Milan]

You need to use more than one motor when the vehicle is heavy or needs more speed.

Such a drive setup is usually hard coupled, mostly to save space and keep drivetrain strong.

If you are worried about different rpms between same motors, you can check them by connecting two of them to a differential setup, in a way that you attach motors on the axles where the wheels should be and power them on. Driveshaft that powers the differential (which is loose for this test) should not be rotating, if rpms of the motors are same.

If you mean using two different drive motors, then you need to place differential between them to compensate their different rpms.

[andythenorth]

1 L Motor per wheel (not axle). Geared up or down 20:12 or 12:20 or direct drive, depending which wheels you use.

On paper (or rather, Philo's site) the L Motor is horrible. It's inefficient and not very powerful. But in practice it has a good balance of speed and torque, and is compact and easy to mount.

Edited February 19, 2015 by andythenorth

[Seasider]

Ok so 2 motors of the same type either side of an output shaft

Sounds perfectly simple thanks

Next q what's the best motor to use If I go for a twin motor system and don't have rc buggy motors ?

[andythenorth]

Forget about diffs, wastes space and breaks 12t gears Just don't physically connect the motors.

Design with 2 L motors, one per wheel: https://www.flickr.c...157649987860696

Edited February 19, 2015 by andythenorth

[__________________________]

Forget about diffs, wastes space and breaks 12t gears Just don't physically connect the motors.

Design with 2 L motors, one per wheel: https://www.flickr.c...157649987860696

That maximizes efficiency (since you have less gears, reducing collective backlash) and is parts-inexpensive, but it's not very realistic (compared to most 1:1 cars). I recommend looking at Sariel's http://sariel.pl/2010/07/scania-racing-truck/

Or this, cheap and fun: http://www.eurobricks.com/forum/index.php?showtopic=86276

[brunojj1]

I would highly recommend the double XL solution like in my Spider. It is very strong and reliable. The total gear ratio according to Sariels calculator would be2.143:1 At a weight about more than 2 kg it goes well, especially with 2 AAA batteries and V2 receivers. You cannot get much more out of it without gear scratching. The L motors were not so satisfying for me. And no comparison to RC motors of course - if you want real speed you have to buy Tamyia or sth like that.

Edited February 21, 2015 by brunojj1

[Seasider]

Thanks Bruno but I can't see where the xl motors fit in your picture

Edited February 20, 2015 by Seasider

[Coola1]

They go behind each of the 36t gears.

[__________________________]

I would highly recommend the double XL solution like in my Spider. It is very strong and reliable. The total gear ratio according to Sariels calculator would be2.143:1 At a weight about more than 2 kg it goes well, especially with 2 AAA batteries and V2 receivers. You cannot get much more out of it without gear scratching. The L motors were not so satisfying for me. And no comparison to RC motors of course - if you want real speed you have to buy Tamyia or sth like that.

Thank you for this pic. I will probably buy instructions for the 458 sometime.

I would highly recommend the double XL solution like in my Spider. It is very strong and reliable. The total gear ratio according to Sariels calculator would be2.143:1 At a weight about more than 2 kg it goes well, especially with 2 AAA batteries and V2 receivers. You cannot get much more out of it without gear scratching. The L motors were not so satisfying for me. And no comparison to RC motors of course - if you want real speed you have to buy Tamyia or sth like that.

Do you know the design ID for those hubs and steering links?

[brunojj1]

Thanks Bruno but I can't see where the xl motors fit in your picture

Sorry, I thought it is obviously. But no problem, here it is in a better view. I modified them with another idea I had long time ago. You want to make your PF RWD car faster? Use the useless L motors! I say useless because amongst many builders they are unloved "bastards" between XL and M. You can leave them out or add them behind the rear wheels - some milimeters space left for them

Combined they provide faster acceleration to the car. The max speed is also a little bit higher compared to the use of 2 XL only.

Total gear ratio of the L motor section is 1,191:1. The XL section has a higher reduction about 2,143:1. Due to the different speed and torque values of the different motors it is a good balanced gear ratio on my opinion.

If you want compare torques and voltages you should visit Philo´s homepage.

Thank you for this pic. I will probably buy instructions for the 458 sometime.

Do you know the design ID for those hubs and steering links?

Please check out rebrickable and the parts list there.

Edited February 21, 2015 by brunojj1

[750ACE]

I had no idea the L motors are hated and called useless amongst builders. I personally favor the motors and their mounting points.

[Graydingo]

Here's a dual motor drive setup I built for my tc6 moc but didn't end up using. It gears down the motor to 1:1677

Here it is with the L motors attached

I did not end up going with this solution though. Instead, I used the 4 prong drive sprockets in a 1:1 ratio

@Bruno, that is a fantastic setup. Heavier moc's really need 2 xl motors. The 2xl with 2L motors will probably be my next setup for the impala I'm building.

[andythenorth]

Use the useless L motors! I say useless because amongst many builders they are unloved "bastards" between XL and M

I dunno, I'll buy your useless L motors from you if you'll sell them less than Lego retail price.

M motor is gutless and has limited mounting points.

XL is a valuable motor, but over-sized and slow. You still need at least two for many vehicles, and they demand a gear train. Being geared so low, they provide excessive torque and will chew gears apart.

Eh, I've no desire for a flame war, just providing some balance. You provided a strong opinion against a specific part, and in a style that's irritatingly common in Eurobricks threads, someone else has taken a single negative comment and translated it to 'everyone hates this .

[brunojj1]

I had no idea the L motors are hated and called useless amongst builders. I personally favor the motors and their mounting points.

I dunno, I'll buy your useless L motors from you if you'll sell them less than Lego retail price.

M motor is gutless and has limited mounting points.

XL is a valuable motor, but over-sized and slow. You still need at least two for many vehicles, and they demand a gear train. Being geared so low, they provide excessive torque and will chew gears apart.

Eh, I've no desire for a flame war, just providing some balance. You provided a strong opinion against a specific part, and in a style that's irritatingly common in Eurobricks threads, someone else has taken a single negative comment and translated it to 'everyone hates this .

Ok, let`s say "some builders" like me who tried to find a good solution e.g. for a crawler. The official crawler set 9398 provided these L motors and everyone was asking what they would be good for if beeing invented for such model and so on. I built a MOC with XL motors and raced against the offroader - it was a pleasure to mount on the duplo bricks like crazy seeing the 9398 getting stuck quickly. They are not useless at all OF COURSE - it depends on the purpose, weight, gear ratio...

The words hate and war are only words on this forum . A fair comparison is a long debate. Concerning your critics about chewing gears - they don´t! And if they do while experimenting - who cares, I have enough of them. My RWD solutions shown above may look simple but took some experience for especially heavy load which need heavy torque. And believe me - it doesn´t chew gears apart in general. Another thing if you mount the parts differently or use older gears. I broke the small differential gears once in years when the 3 L cross axle got stucked in it. Happens some time.

Edited February 21, 2015 by brunojj1

[andythenorth]

Eh, this is the result from a truck with single XL per axle, via diffs.

And yes, I do need to re-engineer it, thin liftarms just aren't the right parts here