Custom Pneumatics and Air-powered Motors Idea

[powerwindows83]

Hello all! I don't know if this is in the right place or not, but it's quite an outlandish topic so I'm gonna assume this is right!

The pneumatics system has gone through many part additions and changes over the decades. One component that never showed up is the hydraulic motor. Now, I'm aware that hydraulics and pneumatics are very different things, but the operational differences would fade in higher speed applications. What I mean by that is if there were to be a very high speed (due to the differences in how air and liquid drive these motors) gear type or axial piston type motor for example, and you coupled them to the existing planetary gear trains found inside most PF motors, the results in theory would be fairly decent torque and roughly normal lego motor speed inside of a roughly lego motor-sized housing.

So why haven't they done this? And how come no one else has done it on the internet so far as I've seen?

I know you can make rotary motion using pistons in an "engine" application, but that method has some obvious limitations barring it from actual use in an MOC usually due to size and/or switching inefficiency. Let me know what you all think of this as an idea, and fill me in if you know why this wouldn't work in practice if it doesn't!

[mocbuild101]

1 hour ago, powerwindows83 said:

And how come no one else has done it on the internet so far as I've seen?

Because they build LPEs (Lego Pneumatic Engines) instead:

 

Edited March 9, 2019 by mocbuild101
we don't make things, we build them :)

[allanp]

6 hours ago, powerwindows83 said:

Hello all! I don't know if this is in the right place or not, but it's quite an outlandish topic so I'm gonna assume this is right!

The pneumatics system has gone through many part additions and changes over the decades. One component that never showed up is the hydraulic motor. Now, I'm aware that hydraulics and pneumatics are very different things, but the operational differences would fade in higher speed applications. What I mean by that is if there were to be a very high speed (due to the differences in how air and liquid drive these motors) gear type or axial piston type motor for example, and you coupled them to the existing planetary gear trains found inside most PF motors, the results in theory would be fairly decent torque and roughly normal lego motor speed inside of a roughly lego motor-sized housing.

So why haven't they done this? And how come no one else has done it on the internet so far as I've seen?

I know you can make rotary motion using pistons in an "engine" application, but that method has some obvious limitations barring it from actual use in an MOC usually due to size and/or switching inefficiency. Let me know what you all think of this as an idea, and fill me in if you know why this wouldn't work in practice if it doesn't!

I think there is a couple issues with a high speed pneumatic motor which is then geared down. Firstly there is the air supply. These motors require vast volumes of air and Lego compressors are not up to it. Secondly they are very noisy, and in small Lego scale it would be like a dentist's drill, not very pleasant to play with. However, I do wonder if a low speed axial piston type motor is possible. Having 6 pistons in a 3 stud diameter barrel would be fairly compact and could also be used as a very compact 6 piston compressor when back driven by an electric motor. So it could work both as a motor and as a compressor. But I think the challenge to overcome with that one is internal friction. In real life, worm gears can indeed be back driven due to their smooth precision ground metal surfaces and literally being submerged in oil. Real life axial piston type motors and pumps also rely on highly polished precision metal surfaces and lots of lubrication. So while I think it's certainly possible for Lego to release something like that in miniature, weather or not it could be made to work reliably I really don't know. Perhaps if the ends of the pistons were fitted with tiny rollers made of the same plastic as the rollercoaster wheel. I think it could work, but now we are talking added complexity. This single motor/compressor would require a new rotating barrel, a new housing,  a new housing end, a new swash plate, new piston, new piston roller, new seals, and if it can't be assembled by us it would require assembly at the factory. This would be an expensive part. So would you be willing to pay, let's say 75 euro for such a motor/compressor? Well of course I would, especially if you can adjust the angle of the swash plate, but that's just me!

[powerwindows83]

9 hours ago, mocbuild101 said:

Because they build LPEs (Lego Pneumatic Engines) instead

there isnt a reasonably sized MOC anywhere that can house that comfortably, and they usually require a very large volume of external air. also unless you use a tube pinching design (which i dont personally like) youre losing a ton of efficiency in the amount of friction the switches make.

[powerwindows83]

3 hours ago, allanp said:

...I do wonder if a low speed axial piston type motor is possible. Having 6 pistons in a 3 stud diameter barrel would be fairly compact and could also be used as a very compact 6 piston compressor when back driven by an electric motor. So it could work both as a motor and as a compressor... I think it could work, but now we are talking added complexity... This would be an expensive part. So would you be willing to pay, let's say 75 euro for such a motor/compressor? Well of course I would, especially if you can adjust the angle of the swash plate, but that's just me!

The gear type motor would require a grease lubrication to keep noise down, but it wouldn't require a large volume of air. The purpose of the gear train in this case would be to dampen the visible effects of the compressibility of air over true hydraulics; the slowing of the output is just an added benefit. If there were no gear train the operation would be rougher, but it would only use as much air as you put into it, plus leakage. It would be a much simpler and smaller design than the axial piston type, but it would be harder to implement it in a build.

I agree it would take a lot of new parts and special engineering. But: (1) I think, even if for some reason it were never to be included in a kit, it would have just unique enough a function to be worth such a price (75 seems a bit high, but that's not important until manufacture costs are determined :P) and worth lego's time to engineer. The existing lego motors come in all shapes and sizes, especially the robotic ones, and I imagine an axial piston motor would fit into a PF M- or L-motor case with a modified 45* front piece so it wouldn't be too terribly radical-looking. And (2) lego parts are already designed with incredible precision, so that's definitely not going to be an issue for them. With respect to fitting the components into a 3-s diam. circle, I think that would work pretty well. Their 1-s width piston plunger and seals would be perfect for this application. The gear train already exists, and they can use the small technic ball joint components to make the swash plate and pistons interact since they're also 1-s wide. The only thing in this motor that would really need to be heavily engineered is the valve system for the pistons, but I'm sure lego's up to the task.

It's an interesting idea. It just can't be 3D printed and work effectively, and most people don't have the ability to mold things at home, so no prototype can be built right now.