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[hazmat]

I've got an old air powered retractable undercarriage off a plane (Rams, control unit, pipes).
I'm trying to make a working Hiab rig for my tug and would like to try and go hydraulic.
1/32 scale, 11 inches over all, tin plate, 300gms
Air pressure was about 40psi but that just lifted 120gms.
Does anyone know of a design for a tiny 12v hydraulic pack?
Note: Peristaltic pumps not strong enough.

Paul

[Umi_Ryuzuki]

Drop your plastic card here...

Garden Trucking...

 

[hazmat]

Thanks for the link Umi_Ryuzuki  but $355 for a pump! I'd need the lottery numbers before spending that much money!

I have come up with a belt powered oil pump for a kit car, 75psi, 100 ml/sec  @ 1500 rpm. £35 GBP
Much more in line with the budget. Now phoning round car scrap yards as I've got a part number.

Same question though, any inventors or boffins out there got any bright ideas??
I don't need a lot of fluid, just enough to move a 1/4 inch piston 3 1/4 inches.
Closed loop system suggested 40psi?

Paul

[peter.dwight]

Greetings.
Like you I think the price charged for miniature hydraulics is ridiculous. You were asking for alternative suggestions on how to activate a cylinder. A syringe like we have in our tool boxes for sucking the water out of the bottom of our boats held in a frame and operatd by a lead screw driven by an electric motor. This would give pressure in one direction and suction in the other. Also is very cheap.
Just a suggestion that might get the old grey cells going.
Regards.
Peter.

[hazmat]

Nice. Never thought of using a lead screw and a syringe.
I'll have a play with that idea but it 's looking like it might be easier to generate compressed air than pressurize oil
and if by magic my pal found one of those little tire compressors in his garage which still works.

[tobyker]

Didn't Lego do a miniature hydraulics set-up some time ago?

[derekwarner]

"Nice.  Never thought of using a lead screw and a syringe" ....interestingly...Rexroth-Bosch...a world leader in industrial hydraulics is suggesting that electrical servo actuators will be the newer form of achieving linear movement [over conventional hydraulic cylinders] ...Derek

[hazmat]

.interestingly...Rexroth-Bosch...a world leader in industrial hydraulics is suggesting that electrical servo actuators will be the newer form of achieving linear movement [over conventional hydraulic cylinders] ...Derek

Mmmmmm.  Not being funny Derek but the Lego idea makes more sense to me than the above .

Anyway I tried the syringe idea with a 140ml plastic size but couldn't force the syringe plunger in hard enough to generate enough pressure either with air or liquid. Could be the size of the pipe I'm using.

 Tobyker, I think the Lego thingy was pneumatic not hydraulic but something else to look into, thanks.

Finally, there's always plan B i.e. give up on hydraulics and use snakes (flexible push rods)

Paul 

[Umi_Ryuzuki]

Set up a test bed with your syringes.
You should have the the line full of water as well as your loaded syringe(resevoir).
When you compress your resevoir the fluid should transfer easily, and proportionally to
the other syringe.

The reason electrical and linear actuators are the potential future, is that optical readers
can meter the movents down to the thousands of an inch... It is strange to sit in with
a bunch of machinists, and hear them saying things like,...

I have a lead screw that will move 1/100th of an inch per turn, and it has a
1:5 geared connection to a stepper motor that can has 250 steps per turn...

Or something like that... I think they are saying that they can make really fine and accurate cuts...

 

Which is why they like stepper motors, and linear actuators...

[derekwarner]

As Paul says .... "but couldn't force the syringe plunger in hard enough to generate enough pressure either with air or liquid".....Paul...air is not a friendly medium as it is compressible & you can suffer from stop/start due to stiction or loading of the mass ....or a combination of both.....

The tube size has no bearing on the force or reaction exerted.....just the speed in which the force is applied....... Derek

[Mankster]

There are plenty of hydraulic model cranes on youtube operated by syringes. Heres one... http://www.youtube.com/watch?v=Qeg0y5AAmtI&feature=related

[Umi_Ryuzuki]

There are plenty of hydraulic model cranes on youtube operated by syringes. Heres one...

 http://www.youtube.com/watch?v=Qeg0y5AAmtI&feature=related

That is a much better example than the two syringes I connected together, and video taped...  

The reason the water may not be working for hazmat is that there may be air in the lines.
Just like your brakes lines on a vehicle, you want to bleed the air out of lines on your syringe hydralics.

 

[chingdevil]

As other have said air is compressable while any fluid is not, be carefull when playing with any type of hydraulics. Pascals law states "pressure applied to a confined fluid is transmitted undiminshed through out the confining vessels of the system" Meaning any pressure you put on the fluid is being put on the walls of the syringe, be careful. Been there seen it done it on aircraft hydraulic systems.


Brian

[peter.dwight]

Greetings.
Further to the interesting comments below I recall that the Gauge 0 and Gauge1 outdoor model railway devoties used to use a pnuematic system for operating points and signals. It's obvious appeal was no electrics but mechanical movement in 2 directions was available anywhere on the layout from your control point (garden shed). I do not know if such equipment is still available? but it was very effective and quite small. Maybe someone has some experience with this equipment and can enlighten us further.
Regards to all.
Peter.

[hazmat]

OK folks, thanks for all your input. Things are getting a bit too theoretical though.
The utube syringe powered crane is an impressive "school science project" and not very practical for a 730mm LOA tug.
The technical theory is way above my head and I always thought Pascal was a computer language or something you sucked  (or is that a Pastille?). No offense meant to the brainy but I'm a basic nuts and bolts, bodge tape, kind of guy.

All I'm after is an "off the shelf purchase idea "  (but not costing a fortune) source of power, air or liquid, I'm not fussy but something small, neat, 12 volt, guessing 40 psi, which I can couple up to the bits and pieces of my RC retractable U/C I've got.

Thanks, Paul.




 

[Umi_Ryuzuki]

You might hunt up something small here then...
We use the valves and other fittings in our combat warships.

 

[catengineman]

Just a thought have you considered the use of a car fuel pump
One that is for an injection system should give you the required pressure and flow rate and to get a small one then look at a Fiat or any one with the in-tank system (I think).
The only issue I see is your control of the ram pressure to expand the ram/rod then will you rely on gravity to compress the ram/rod if so the "exhaust" side will need to be larger then the pressure side to assist in the removal of the pressure.