Micro hydraulics/gear/servos for moving crane arms

tomstaf

Western Thunderer
Hi,

I'm wanting to get 2 connected small crane arms to move and having been mooching around online, (particularly over at Japanese stuff and other areas of modelling) looking for a suitable mechanism but haven't come across anything suitable yet. So if you've got any ideas please fire away.

The larger crane arms works out approximately 74mm long, 4.5mm heigh and 4mm wide. It needs to move on 2 axis - up/down and left/right.

The smaller connected arm which only need to move on 1 axis (up/down) is 17mm long x 4.5mm wide x 4.5mm heigh.

The connection is a bit like the human arm - both are permanently connected to each other, and the 2 are permanently connected to a body.

Any ideas?

Cheers

Tom
 

auld_boot

Western Thunderer
Not sure if you could get enough movement or if it would be controllable enough but may be worth checking out memory wire, nitinol wire.
 

Osgood

Western Thunderer
Tom - are you are talking about a hydraulic crane here?

One lateral thinking option (if you can find something small enough) might be a rotary actuator with screw thread incorporated into the hydraulic ram - so the ram actually works.

Another option would be to use flexible but axially rigid wire threaded through the main boom and ram to push/pull the outer arm, attached to the ram pin. the wire would run within the ram and then through the main boom to the body - where you should have more room to locate a push/pull actuator. Rotation could be accommodated in the design of the actuator link to the push/pull wire, so the actuator can be even fixed in relation to the crane base not the main boom.

Tony
 

Pugsley

Western Thunderer
How about actual hydraulic rams controlled by some sort of hydraulic system based around a small syringe? You could hide it under the bed of the wagon and actuate it with a servo. That way to extend and retract the arms, you'd only need to push or pull the syringe as appropriate, you wouldn't need a full hydraulic system, where fluid is directed to one end of the ram, or the other, to move it.

You'd need to make the rams, the most difficult part of which would most likely be sealing the piston inside the ram.

Do it! :)
 

tomstaf

Western Thunderer
Thanks everyone:thumbs:

Tony - I'll have a look at mini actuators :)

Pugsley - I like your thinking and it may well be an option. Depends how big a syringe I'd need but I'll look into it.

Jim - That creations by the Germans certainly gives me something to think about. The small cylinder looks like it might just fit but the feed pipes on the side might be a problem. But perhaps I could make something similar and reduce the size even more...

Plenty of investigation to do

Cheers

Tom
 

oldravendale

Western Thunderer
Thanks everyone:thumbs:

Tony - I'll have a look at mini actuators :)

Pugsley - I like your thinking and it may well be an option. Depends how big a syringe I'd need but I'll look into it.

Jim - That creations by the Germans certainly gives me something to think about. The small cylinder looks like it might just fit but the feed pipes on the side might be a problem. But perhaps I could make something similar and reduce the size even more...

Plenty of investigation to do

Cheers

Tom
Hi Tom.

This may be of no help at all but I remember when Steph was a boy (cue violins:p) he had Lego which used a hydraulic system in plastic cylinders. At the time it worked extremely well and if still available may be worth considering, although the size may be too large for your needs. It is possible that Steph can comment and we may even still have these in the huge box of Lego we retain should you want photos and sizes. I've no idea whether these are still available.

Best.

Brian
 

Pugsley

Western Thunderer
Pugsley - I like your thinking and it may well be an option. Depends how big a syringe I'd need but I'll look into it.
The size of the syringe will depend on the size of the final cylinders and the travel required, not to mention the fluid capacity of the system. It doesn't even need to be an actual syringe - if you can design and build a square cylinder, to better fit under the wagon, then you could do that, although sealing the piston would be a bit tricky.

Here's a couple of links that will give you food for thought:
http://www.jalopyjournal.com/forum/threads/hydraulic-clutch-master-and-slave-size.660293/
http://www.buckeyetriumphs.org/technical/clutch/ClutchCalculations/ClutchCalculations.htm

Ignore the bits about pedal travel, as that's not strictly relevant to what you want to do, but the principles are there. The second link is particularly useful, especially the bit under the 'Hydraulics' heading, under the second set of pictures.

HTH
 
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