8 replies to this topic

[Hopey]

Hiya. So I've gone and ordered myself an 8043 for all the awesomeness it contains, and while I wait for it to be delivered, I've been thinking about what I can do with the parts it contains.

I'll end up having 6 PF-M motors, and 4 IR output channels, however if I piggyback two motors together on two of the outputs, I can use all 6. For example, I might make a pair of small RC cars, each with one motor for steering and two for drive, the two drive ones wired together and geared something like this:




Does this work? Are there any drawbacks?

How does the power compare to a single XL motor?


Cheers.

[roamingstudio]

Others may correct me... but if the motors turn slightly different speeds this might cause a problem. Rather I would load them through a differential to ensure they are both working maximally

[Crazydance]

roamingstudio, on 09 July 2012 - 09:20 AM, said:

Others may correct me... but if the motors turn slightly different speeds this might cause a problem. Rather I would load them through a differential to ensure they are both working maximally

I have seen this construction more or less on a small RC tri-wheeler.
But indeed if one of the motors is slightly slower or reacts slower than the other it may cause a problem.
You can correct this with a differential which can actually catch the difference between the two motors.



Another question. WHY do you need this construction specifically? You could use a L or XL motor with some gearin instead.
However this might be a solution for making your RC car go fast.

It it possible to use the M motors with two gears to make it move even faster?
I don't have LDD here right now but I believe we should make a small powerful and fast base for RC cars.

[Hopey]

Crazydance, on 09 July 2012 - 09:43 AM, said:

... But indeed if one of the motors is slightly slower or reacts slower than the other it may cause a problem.
You can correct this with a differential which can actually catch the difference between the two motors.
...

Another question. WHY do you need this construction specifically? You could use a L or XL motor with some gearin instead.
...

I don't know the exact mechanics of it, but my intuition is that issues with slight differences in speed would only occur if it's running unloaded. As soon as there's a load applied, it would sort of force them to work at the same speed. Kind of like how having multiple engines on a single train works. If A goes a little bit faster, it takes the load off of B, which is then unloaded and goes faster, catching up with A. Negative feedback ftw.

As to why, I've reached my budget for the forseeable future, and plan to build what I can with what I've got before I go buying anything extra, including XL motors.

Currently I've got:

• 8110 Unimog
  
• 8109 flatbed (+ 6 extra wheels)
  
• 8043 excavator (on it's way)
  
• My kids' moderately sized collection of System lego, including a 7685 dozer

This gives over 4000 technic parts to play around with, including 2 IR remotes, 6x PF M motors, pneumatics, 4 linear actuators, 3 diffs, many uni joints, a bunch of tank track, 4 big wheels and 12 small ones, etc, and I've already got quite a few ideas:

• A pair of simple RC cars
  
• A pair of simple RC tanks
  
• A big RC tank with suspension of some sort and controllable turret
  
• A big 4wd RC car, of similar design to the 9398 crawler in terms of motor placement and suspension, using the unimog wheels and possibly paired motors for drive (4xM total for drive!)
  
• Some kind of halftrack maybe.

When I get through all of that, I might think about buying some new parts :)

[Crazydance]

Hopey, on 09 July 2012 - 10:07 AM, said:

*story cut*

Well maybe you can try to build the mini three-wheeler first just to check if your theory is spot-on.
I'm guessing you'll be done with that pretty fast ans you'll have a funny car at the same time.

[andythenorth]

Combining two motors in a gear train should be ok I reckon.

However it gets interesting if the connection to one is interrupted causing it to stall.  This will put a greater load on the other motor, I think the PF receiver would cut out before this causes damage though.

It gets really interesting if the connection to one is reversed.

I have unintentionally connected two XL motors to the same gear train, with rotation in opposite directions.  This causes you to own fewer gears, but more small pieces of gear.

Worst case?  Broken motor(s), broken gears.  Mostly a question of what you can afford to break  

Edited by andythenorth, 09 July 2012 - 06:40 PM.

[pluto7443]

I've actually done this before I got my XL-motors, and it doesn't work near as well as an XL-motor, however, the M-motors don't have the strength to break gears very easily. Maybe the 8-tooth gears or half-width gears, but nothing else.

[gti180]

I use two or more motors together quite often, the model in the link below uses 4 xl motors 1 per axle and two medium motors linked in the same way you suggest but for the steering. These are all powered from one receiver.



I've also tried 6 medium motors 1 per wheel on a small version of a six wheeled dump truck - this didn't work very well as the motors didn't have enough torque.

[goldsun]

Hopey, on 09 July 2012 - 09:14 AM, said:

Hiya. So I've gone and ordered myself an 8043 for all the awesomeness it contains, and while I wait for it to be delivered, I've been thinking about what I can do with the parts it contains.

I'll end up having 6 PF-M motors, and 4 IR output channels, however if I piggyback two motors together on two of the outputs, I can use all 6. For example, I might make a pair of small RC cars, each with one motor for steering and two for drive, the two drive ones wired together and geared something like this:




Does this work? Are there any drawbacks?

How does the power compare to a single XL motor?


Cheers.

Hi
I'm using these solution in my robot "number six" to pull up upper body, weight 3.5kg

http://www.brickshel...y.cgi?i=5527362

But, I'm using z24 Clutch instead of z16 because of "possibility" of different speed of the motors.
Working well for me.

--
Łączę różne wyrazy i pozdrawiam
Grzegorz "Goldsun" Ludwiczek

Edited by goldsun, 10 July 2012 - 08:38 PM.