Anyone have a solution for my problem?

[aminnich]

It has been awhile, but I have recently been working on drawing and designing a new project without the legos. I dont really have much time to work on any projects now, so im just designing it for now.

I do not want to say what im building, because A) it hasnt been done before B) Its gonna be epic haha

Here is my question;

I want to have a drive train for each wheel separately with variable speed (using train remote) BUT i also want to show the speed change with an actuator of some sort. I know, that does not make sense now, but it will later.

My original thought was;

m motor for powering the axle, mini LA hooked up to the motor. of course this wont work because the LA with just continue to extend/retract.

If the motor is at lets say 50% speed, I want the LA to only be 1/4 extended pass the half point. Half away point because then i can easily represent reverse.

Sure I could have a separate motor for each LA, but space is limited and id like to use as little motors as possible (less motors, less wires, less receivers, etc etc)

I know is very obscure right now, but i hope someone have an idea. Keeping in mind space is somewhat of a constraint for this build.

Thanks for any thoughts.

[Attika]

If you can afford to use a separate servo motor that could follow the exact position of the train remote "signal". With a simple link system on the servo you can achieve that linear movement.

Sorry if it doesn't matches your demands, you really left us in a mysterious enviroment..

[krtwood]

Have 4 (or more) liftarms connected around an axle. The faster the axle spins the further out the liftarms are going to go. The end of the liftarms passing through a window is your speed indicator. Balance the weight of the liftarms and the speed of the axle.

[syclone]

The servo is your best option, small and simple

Plus you can make an indicator with numbers connected to the servo axle

Edited September 17, 2016 by LXF

[Technic Jim]

I'm not really sure, but I think some sort of differential setup would do it.

Maybe, perhaps, possibly!

[Rascko]

Have 4 (or more) liftarms connected around an axle. The faster the axle spins the further out the liftarms are going to go. The end of the liftarms passing through a window is your speed indicator. Balance the weight of the liftarms and the speed of the axle.

It's possible to try something like this:

But not sure, whether this could be made compact enough to fit your MOC.

[Victor Imaginator]

Clever using of differentials seems logical for me. Some kind of comparer of torque and speed. I've seen automatic 2-speed gearbox somewhere based on differentials.

[Kristof]

Derived from your complicated description, I guess that you are seeking for a solution for mechanical speedometer/tachometer, is that correct? Real mechanical speedometers in cars use magnetic induction principle, thats something you hardly make with lego. The only other mechanicals solution I know all use centrifugal force, just like the contraption suggested by @Racksko. Nico71 has built one:

http://www.nico71.fr/centrifugal-tachometer/

I don't know about using differentials. In theory, you should have this torque/speed proportion on the output shafts but I don't know how well that actually works with lego pieces. The principle doesn't seem very beneficial, since such technology is not used for real tachometers (or is it?).

[Rascko]

Just one more scheme of mechanical tachometer, with spring inside - could be used for inspiration of some kind.

[TheMindGarage]

I think a centrifugal device would work best. The only problem with those is that they have a tendency to jump from fully closed (indicating low speed) to fully open (indicating high speed) very quickly, and they are quite large.

I'm not really sure, but I think some sort of differential setup would do it.

Clever using of differentials seems logical for me. Some kind of comparer of torque and speed. I've seen automatic 2-speed gearbox somewhere based on differentials.

Differentials can be used to measure torque (that's how the automatic gearboxes work), but they can't be used as mechanical tachometers.

[Rascko]

One more mad idea - I'm not very sure, whether it's possible by Lego pneumatic, - having kind of compressor, that is pumping air into some cylinder with piston, that loses air. The higher is rotation speed - the higher is piston lifted with pressure. But this seems an even more contraption-styled.

very quickly

Spring loading might help. Edited September 17, 2016 by Rascko

[dr_spock]

How about PF LEDs? Their brightness would be directly proportional to the speed if you connect them to the motor.

[Didumos69]

So you hide your Epic design from the crowd, but you need the crowd to make it Epic? That's not Epic, it's Brilliant! :laugh:

Edited September 17, 2016 by Didumos69

[Attika]

So you hide your Epic design from the crowd, but you need the crowd to make it Epic? That's not Epic, it's Brilliant! :laugh:

For me the riddle in this topic isn't to solve this problem, but finding out what purpose this solution is needed for...

I've got an idea or two but I won't be the one who ruins the game . I'm sure however this isn't a tachometer thingy...

Edited September 17, 2016 by Attika

[Didumos69]

For me the riddle in this topic isn't to solve this problem, but finding out what purpose this solution is needed for...

Which is exactly why it is brilliant. People are tempted to help because they want to know more.

I want to have a drive train for each wheel separately with variable speed (using train remote) BUT i also want to show the speed change with an actuator of some sort.

What is the purpose of showing the speed? Is it really required to be proportional to speed or is proportional to torque good enough? Does the actuator actually need to control another function?

[aminnich]

Holy Moly guys, you might be WAY over thinking this. What im looking to do isnt the main function, it is simply a part of the overall MOC.

Here is my plan (without giving away what im going to be building)

2 motors, separately driving a rear wheel, kinda like a skid steer.

Each of these motors will need this linear actuator design to show variable speed (does not have to be exact, just somewhat close)

The actuator will show, lets say 4, different speeds in the forward and reverse directions.

SOO (by the way this should give away what im building) if the "machine" is moving forward and turning to the right, the left actuator would be farther extended than the right one (showing that the machine is turning to the right)

Likewise, if the machine was turning to the left in reverse, the left actuator would be farther out than the right one, both in the reverse direction.

If you want to take guesses at what im building, you may gladly guess

Im hoping to build a moc up of the design set up of actuator/drive. If i get the time, it wont be small enough for the moc, but if will give u guys a better idea of what im looking to do.

[Kristof]

Ahh, now I know exactly what you mean! And conveniently, I know a PERFECT way to implement this! I can't simply show you or even tell you comprehensibly, but I can give you great confusing and chaotic sort-of-description, so here you go: You need to make this kind of linkage, it uses some gears and certain other parts, including friction pins. It works similarly to the... ouch, I can't tell you this... Well, anyway, you then connect this between your drive train and the actuator and it's done!

Understood? Little bit obscure and hard to follow but with a little bit of fiddling around, you should be good!

:wub:

[allanp]

Holy Moly guys, you might be WAY over thinking this. What im looking to do isnt the main function, it is simply a part of the overall MOC.

Here is my plan (without giving away what im going to be building)

2 motors, separately driving a rear wheel, kinda like a skid steer.

Each of these motors will need this linear actuator design to show variable speed (does not have to be exact, just somewhat close)

The actuator will show, lets say 4, different speeds in the forward and reverse directions.

SOO (by the way this should give away what im building) if the "machine" is moving forward and turning to the right, the left actuator would be farther extended than the right one (showing that the machine is turning to the right)

Likewise, if the machine was turning to the left in reverse, the left actuator would be farther out than the right one, both in the reverse direction.

If you want to take guesses at what im building, you may gladly guess

Im hoping to build a moc up of the design set up of actuator/drive. If i get the time, it wont be small enough for the moc, but if will give u guys a better idea of what im looking to do.

Sounds like you are building a racing wheelchair with tilting driver! If it's just for indication purposes could you just not just use a weight that swings side to side due to the centrifugal force of turning round a corner?

Edited September 17, 2016 by allanp

[aminnich]

alan, close, but not quite. The counterweight idea would work for that, but not for my problem. Good guess tho, what i need would definitely work for that tho.

Kris, Wow thanks for the helpful hints there, but ya thats not gonna help me at all. I have been tinkering with different ideas and cant figure it out.

Since it will be easier for you guys to understand exactly what im looking for, ill tell you what i want to build.

Im buildings an Exmark Lazer Z zero turn mower. The drive is obvious (like a skid steer, like i said), but the actuator idea would be for the handles, the farther out they are the faster the mower goes. Get it??

I just built a system that would work, ill post pictures later. The system involved; m motor (stepper) to the train remote (variable speed) to XL motor (drive), then servo to switch (turn on and off the actuator) then switch to L motor to actuator. The XL motor was connected to a receiver with train remote and the m motor and servo were connected to another receiver (i controlled that one) That is a lot of stuff and i would need double that for each wheel. AKA thats not gonna fit in the space.

Im sorry, i know that is confusing, but i am unable to post pictures right now.

[Kristof]

Now that's interesting! I can't remember seing any mower moc. Really looking forward to it.

About the system, are you sure it needs to be that fancy, like proportional to the speed? Wouldn't it be enough for it just to tilt forward/backward - that would be much easier to pull out.

[Rascko]

Hmm, why do you need all these actuators and so on there? If you have train remote (I mean this one - https://sh-s7-live-s...d=0&printRes=72) - isn't it possible just to connect levers to actual driverings of a remote with just a couple of bevel gears? Will need some gearing down, but should work. So you will need just two motors per wheel - one for rotating controller and one for drive itself?

BTW, I've just got the idea, that I've never considered remote as a valid part of moc for doing something specific. So, there appears very interesting question - what part could be used for connecting to remote channel switch? :)

Edited September 17, 2016 by Rascko

[Captainowie]

I have a number of thoughts here:

Firstly, asking for help but then deliberately hiding relevant details is not "Brilliant", it's rude. All the usual guidelines relating to asking for help apply just as well here as they do to other forums, particularly using a helpful and specific subject line.

Secondly, you aren't going to be able to construct a speedometer-like device using differentials. Differentials do ADDING (and SUBTRACTING), whereas measuring the rate of turn of an axle requires DIFFERENTIATION, a fundamentally different operation.

Thirdly, be very careful about making claims that something has never been

before. If it's a physical machine, there's a pretty good chance someone has reproduced it in LEGO.

Finally, while connecting directly to the train remote might work (as suggested by Rascko above), I am concerned that it'd be too easy to get the position of the control knobs misaligned with the state of the motors - e.g. if you turn the knobs then press the button, the motors will be off but the levers will not be reset to their origin. A better approach would surely be to link the "control" levers directly from a servo motor (bypassing the LAs entirely), with the servo motor connected to the same receiver as the XL motor that drives the wheel. Then you can just hold the train remote directly, rather than mess around with a stepper motor, and instead of having to find space in your MOC for a train controller plus 2x(stepper motor, drive motor, LA+motor, IR receiver, servo, switch), you only need one receiver, and 2x(drive motor, servo), which is surely not too much.

Owen.