Is it possible to speed match motors

[Andalo_an]

Hello,

I have stared the initial designing for a project that is a very long and specific consist, around 26/27 cars long, currently measuring just over 15 yards at 46’ 9” (there are a couple unknowns that I still need to find measurements for). While everything will have ball bearings there will also be a lot of interior details. Given this I will need additional motors. The locomotive will likely be powered by 2 L motors and controlled by a FxBrick. I will probably be looking to add a couple extra train motors throughout the rest of the train. Would there be any way to have it set so that when I control the main motors in the engine with their driving wheels, the train motors adjust to the same speed? Is there a simple way to do this or would it need to be a separate additional control circuit of some sort?

[XG BC]

53 minutes ago, Andalo_an said:

Hello,

I have stared the initial designing for a project that is a very long and specific consist, around 26/27 cars long, currently measuring just over 15 yards at 46’ 9” (there are a couple unknowns that I still need to find measurements for). While everything will have ball bearings there will also be a lot of interior details. Given this I will need additional motors. The locomotive will likely be powered by 2 L motors and controlled by a FxBrick. I will probably be looking to add a couple extra train motors throughout the rest of the train. Would there be any way to have it set so that when I control the main motors in the engine with their driving wheels, the train motors adjust to the same speed? Is there a simple way to do this or would it need to be a separate additional control circuit of some sort?

that depends on the types of motors and the gearing attached to them if you have equal gearing in the loco and the cars you are good to add more motors by just stacking the plugs of the motors at the pfx brick but if you are using different motors you need to dive into programming/rpm matching with powered up or with something like an arduino to controll the motors of the loco independent of the cars inorder to have the same output rpm

[Toastie]

3 hours ago, XG BC said:

you are good to add more motors by just stacking the plugs of the motors at the pfx brick

I believe this is not as straight forward as stacking them: The FX brick has a 3A max output per channel, as per their website. However, the 3A need a source that can sustain that amperage.

Let's say you operate with a 9V battery box, again, as shown on the FX website: At 3 A/per channel = 6A total, that means you need to manage about +50 W total. The battery will drain in a very short time, and your wiring may very well dissipate a good fraction of that wattage as heat.

I believe you would need additional power sources to manage all that energy should you add more motors. @Haddock51 has some nice threads here on EB. He operates >multiple< 9V motors moving one train powered directly from 9V track.

Best regards,
Thorsten

 

[supertruper1988]

Couple thoughts here, it is not very easy with LEGO to match motor speeds across types without also diving into the world of custom programing. It could like like be accomplished with a custom app running pybricks or some combination. 

As a side note, if you can gear the L motors at 1:1 then 45 feet of train on an appropriately sized, and flat layout, will not be an issue. If you can swing a second locomotive also with two more L motors, it will not be an issue at all. I have pulled ~20 feet of train on a single L motor.

[Lok24]

This possible with motors that can  be set to rpm, like the Powered up technic motors.
And there it is very easy to adapt different gear or type of motor.

But much better is it to use a second loco

[zephyr1934]

20 hours ago, Andalo_an said:

I have stared the initial designing for a project that is a very long and specific consist, around 26/27 cars long, currently measuring just over 15 yards at 46’ 9”

That's a pretty long and heavy train and with your numbers it sounds like you are building about 72 stud long cars. No matter what you are building at this length it will probably take some trial and error to get it to work and you will need a massive layout to even fit it, much less not have the train take up most of the loop of track. I assume you already know all of that.

Have you built a train even 1/3 this length? There are all sorts of problems you run into with long trains- drag from being in a curve (or worse, multiple curves), drag from uneven track, etc.. Your couplers are likely to become your weak point. Or if you use something stronger than magnets (e.g., BMR Kadee couplers) their attachment points. The train might be heavy enough that it could stringline on a curve if all of the power is at the head end.

All of these challenges can be surmounted, but it will take trial and error, with some of the failed trials potentially being expensive and time consuming. Still could be fun to undertake and even more satisfying once you get it mastered.

A couple of thoughts,

1) a good "if all else fails" backup plan might be to be prepared to make 1 or even 2 cars be a hidden locomotive, so maybe there is no interior or you only show a portion of the interior on those cars. Using the covered space to hide the motors and batteries. Your audience probably won't notice that they can only see the interior of 24 out of 26 cars.

2) Personally I would try to power all of the units the same way as the lead unit to mechanically avoid having to compensate. Even if you use rotation sensors, wheel slip could throw your coordination off. But I would think through trial and error you could come up with sufficiently matched gearings. I just wonder what happens when you have part of the train in a curve and part on a straight, distributed power could cause problems by compressing the slack or increasing the drag.

3) Build about 1/3 of the train as if that were all you were going to build. So make cure you get all of the critical cars necessary to capture the essence of the full train. Then use that as your test base to see what you can do for the rest of the train. Presumably if you have the track and experience to build a 50' train, you probably have enough cars around to simulate the remaining 2/3's of the envisioned train. This will let you experiment to see how the full train will perform and then after experimenting a bit, you can calibrate what want to do from here. Having built the key cars, you have covered yourself in the event that you need to cut something back.

Whatever it is, I bet it will look amazing