Hi,

Can someone please tell me if there is a practical maximum hose length for a Lego pneumatic system?

The application I have in mind is for ‘remote switching’ of a railway track point. The track point is ~1500mm from where I want the switch.

I presume I would be best to use 3rd party hose at these lengths.

I’ve tried to search for an answer, but nothing has turned up. Can anybody here help?

thanks

david

edit: ps, I am probably going electrical, but just thought I’d consider a pneumatic solution, though it appears in any case parts for that may be difficult to source.

Edited March 11, 20186 yr by cptkent
Addition

There is probably a limit, but I don't think you'll be hitting it at 1.5 meters. Electrical should be easier to implement, though.

Edit: Tried it, had no problems.

Edited March 11, 20186 yr by Saberwing40k

3 hours ago, cptkent said:

Hi,

Can someone please tell me if there is a practical maximum hose length for a Lego pneumatic system?

The application I have in mind is for ‘remote switching’ of a railway track point. The track point is ~1500mm from where I want the switch.

I presume I would be best to use 3rd party hose at these lengths.

I’ve tried to search for an answer, but nothing has turned up. Can anybody here help?

thanks

david

edit: ps, I am probably going electrical, but just thought I’d consider a pneumatic solution, though it appears in any case parts for that may be difficult to source.

 No problem. A long tube is just like an air tank. The only thing... the longer the tube the more air in the system, and less contol over the piston

 

45 minutes ago, ben20 said:

No problem. A long tube is just like an air tank.

Exactly.

A longer tube only changes the dynamic behaviour of your system.

Waiting long enough, the pressure on your pistons is the same as with short tubes.

The main difference comes from the dynamic resistance a long tube has, so your system will react slower. Also, the elasticity of the tube means that you will need slightly more air for the same movement as the tube will expand with pressure.

 

If you switch early enough, you shouldn't have any problems :-)

There have been alot of pneumatically powered cars out there in the past.  I also build and drove a pneumatically powered Unimog which required about 5 feet of hose (more or less the same amount you are proposing).  The hose was not an issue.  And whatever delay there was supposed to be was more or less negligible.....

17 hours ago, ben20 said:

 No problem. A long tube is just like an air tank. The only thing... the longer the tube the more air in the system, and less control over the piston

+1

A long electrical wire may also have its own issues. The wire gauge TLG uses is so small that voltage drop may result in less power for the motor as power is wasted through what is essentially a long, thin heating element. 

Thanks to all those who replied.

I have a couple of 'electrical' solutions, but then started wondering about a pneumatic one. I may set up a testbed to evaluate it.

David

Check this out! This switch works great! It can easily be remotely controlled.

https://rebrickable.com/mocs/MOC-11841/1963maniac/pf-motorized-actuated-train-track-switch/#comments

I just tried the 10 foot piece of 3rd party tubing on my desk.  I used a small pump, and it was just like having a tank in the system.  Slow but worked perfectly.