Lego Hydraulics

[grindinggears]

***This thread continues the discussion about creating a hydraulic system by using the official pneumatics parts***

To take a look at what has been said before please take a look at this thread about benjiii712's excavator. The discussion about hydraulics starts on page 2.

http://www.eurobricks.com/forum/index.php?showtopic=51310&view=findpost&p=911899

In this post I want to sum up what has been said about the two most discussed solutions:

Number 1: Using a motorized compressor to power a system of valves and pistons like we know it from pneumatics

The main problem is: How do we get the liquid (water or non-aggressive oil) into the compressor) and how do we get it back there when it leaves the valves?

AllanP has pointed out a way to solve that:

Using a big watertight reservoir, eg. a boat hull, and filling it with the liquid. The compressor can be placed within the liquid while the attached motor remains clean.

The valves are placed directly above the reservoir, thus the liquid ejecting when changing direction gets back into the reservoir.

Read his post here: http://www.eurobricks.com/forum/index.php?showtopic=51310&view=findpost&p=912981

Number 2: Using pneumatic pistons to power pneumatic pistons

Brickshelf user Timo has used this solution for the steering and outriggers of his massive mobile crane Liebherr LTM1500.

For a detailed description of this technique you can read this post by me:

So join the discussion: Wouldn't it be incredibly awesome to have a hydraulics system that matches the advantages of the pneumatic system (load-balancing, easy to attach via hoses) with those of the LAs (precision, stays in place) ?

And we need some people who are keen enough to risk their Lego parts for the sake of advanced Lego science

[efferman]

could a big lego cylinder corrode? is it better to use olive oil or silicon oil to prevent the corrosion?

if corrosion is not a problem, the ydraulik is a really genius solution for multiaxle steering. But for a excavator or similar it has in my humbly opinion no sense.

i think i try a hydraulik suspension on my willys to get a proper axle load balancing

Edited January 28, 2011 by efferman

[allanp]

Thankyou, I was gonna start this topic but you have saved me the trouble

Yes this would be truly awesome and the more I think about it, probably not that difficult actually.

One thing I would like to add to discussed solution number 1.

You would need to have a method of recirculating the fluid if the compressor is on but no valves are open. The pressure comeing from the compressor goes to the valves but also directly to a release valve that goes straight back into the resevoir. The release valve is operated via a cylinder that has a resistance against it via a spring. Very similar in operation to a pneumatic auto shut off swith, accept it does not operate a switch to turn off the motor (although that is another option but there is no safety against a build up of too much pressure this way), instead it operates the pressure release valve, resulting in the fluid being allowed to freely flow back into the tank. This would result in the compressure being under full load when nothing is being operated (therefore slowed down) but then automatically speeding up as something is operated (how authentic is that!!!!!!). The power of the sytem is set to, or limited by what ever amount of resistance you have against the pressure valve control cylinder, so you can set it to be as strong or as delicate as you like (providing you can prevent the hoses popping off of course).

[Out of Sight]

Great, since I believe I was the one who mentioned silicone filled hydraulic actuators first on page 2 of that thread

I've rebuilt many 1/10 - 1/8 off-road type RC shocks, (not LEGO RC, but real hobby grade 'adult toy' which tops out 40-50mph). The shocks themselves are also 'hydraulic', which work by dampening suspension rebounds and hard landings by means of fluid resistance going through the piston holes.

Here's what I 'drive' LOL 1/10 short course truck. and what the shocks look like, I'm using high performance Traxxas's aluminum bigbore shocks. They come with titanium nitride coated steel shaft for low friction and scuff resistance.

,around 130mm fully extended:

Anyway the biggest challenge i think is to make a tight seal..tight enough to retain the liquid inside, but loose enough not to cause any binds. You can start looking for RC shock o-rings. But I do believe it's a LOT easier to modify RC shocks and ditch the springs,since the shafts and pistons are already precisely made to retain oil.

Here's a link on RCmart...you can find cheap Chinese made aluminum RC shocks with many sizes to suit the required length. If you need a high-end shocks, that'll cost around USD 50-70 for a set, such as Traxxas Bigbores and Proline Powerstrokes

http://www.rcmart.com/catalog/damper-kits-damper-c-389_390.html

Here are the o ring seals:

http://www.rcmart.com/catalog/damper-kits-damper-accessories-c-389_690.html

And no people, silicone is not poisonous

[rien]

Also a nice hobbe out of sight!!!

i have a lot of that stuff

my greatist?

a schumacher fusion 2,8

Features:

- 80 mph top speed

- 2.85hp 33000rpm Picco built .28 (4.5cc) engine

- 3 Speed transmission

- Electric start system

- Tuned pipe

- High grip competition Japanese foam tyres from ATS

- 4wd transmission with an enclosed 16mm wide kevlar reinforced drive belt

- 4mm thick strong aluminium anodised chassis

- Ball differentials with steel outdrives

- Fully adjustable race developed suspension

- Oil filled purple alloy shocks with ground colour coded springs

- Prepainted and trimmed polycarbonate body.

- Enclosed radio and battery box.

- Standard 200mm 1/10th scale bodies will fit.

- Standard 12mm touring car wheel hex.

- Full range of option parts available

i run it on 25%nitro

[Tobbe Arnesson]

In solution number 2, LA's can be used to move the cylinders.

Solution 3: Custom made valves (with return line to the reservoir) and a real hydraulic pump. Next step hydraulic motors and different size rams. Who's good with the lathe and milling machine?

Here are a few sources for RC hydraulics:

http://www.bernett-modellbau.de/sites/en/presites/produktsites/hydraulik-en.html

http://www.damitz-modelltechnik.de/index3.htm

http://www.leimbach-modellbau.de/

http://www.stahl-modellbau.com/0000009d0014c2e54/0000009e2b13d5c22/index.php

And here's a demo of what can be achieved:

[grindinggears]

Sorry for not posting here in the last days, I was at the wedding of a friend of mine and didn't have the time to post here.

BUT I have made some thinking about how a hydraulic unit with compressor and valves could be built and how to make it watertight (or oiltight )

I will build a mock-up model of such a device in the next week, maybe you have a suggestion for me if there is a hull or tank piece by lego that fits the following specifications:

- made of one piece so it's watertight

- has a rectangular shape and is about 10 to 14 studs high

Maybe some bionicle boxes will fit that. Otherwise I have to use a non-Lego tank

On the 28th of January I got Timo's reply about his mobile crane and how the hydraulics were working.

First the biggest news: He is still working on the model! So we have a good chance of seeing it in motion sometimes in future

I have put the whole message from him in the attachment if anyone speaking german wants to read it in original.

He gave me the following hints:

• The plugs of the pneumatic cylinders are too narrow to provide a sufficient working speed with water. Hence he widened them to 1.2 mm using a drill. Too bad for the purist in me
  
• Considering rust: The new cylinders (maybe he meant the past 2003 cylinders by saying new?) do not corrode.
  
• He used silicone grease to tighten the cylinders.
  
• Instead of the original Lego hoses he used slightly narrower ones which didn't pop off ever.
  
• To improve the outrigger performance he supported the counter cylinders with rubberbands which give additonal pressure when extracting the outriggers.
  
• As a liquid he used a mixture of distilled water and alcohol. The alcohol was used to decrease the surface tension of the water. I'm not an expert in that field but I suppose the surface tension of the water would otherwise have caused additional resistance when running threw the narrow hoses.
  

So his solution (number 2) is not just a CAD idea but a real one which eventually works and has undergone some heavy sophistication.

That's it for Timo's hydraulics. He also wrote something about the progress of the rest of the model (see the attached text for more info). Maybe I should post these infos somewhere else (doesn't really belong to hydraulics)...

Finally I want to reply to the recent posts here in the thread:

@ efferman

For suspension the solution number 2 might work really good. Think of a vehicle with pendular suspension on all axles. Now attach hydraulic pictons on each side of every axle and connect all pistons on the left side to each other and also connect all on the right side together. If the left front wheel now goes up because of an obstacle the rear left wheel goes down because both are connected via hydraulics. Thus you eliminate the risque of tipping the vehicle over to the side.

@ allanp

That release valve idea is purely genius! I have incorporated it into my design.

@ Out of Sight

Thank you very much for the inspiration, yes you were the first to mention hydraulics :thumbup:

You could be right that the seals of the pneumatic cylinders will be a big problem for the lego version as noone wants to have a model that sparks oil all over the floor

@ Tobbe

Your idea of moving the counter cylinders with LAs might be not really right out. Think about an attachment for an excavator, e.g. a claw, that needs power and accuracy but is so far away from the engine housing that driving an axle through three moving joints to eventually move the claw is too complicated. Here you can use a LA inside the engine housing moving a counter hydraulic piston that transferres its motion via hoses to the claw!

The prices of professional RC-hydraulics are far beyond my budget

So that's it for this post. Maybe it's my longest post ever?

We have many ideas and concerns now so we should start building something and see how far we can get!

konversation.txt

[allanp]

Solution 3: Custom made valves (with return line to the reservoir) and a real hydraulic pump. Next step hydraulic motors and different size rams. Who's good with the lathe and milling machine?

I'm good with a lathe and milling machine and many other types of machinery. I could make the valves, pump, tank and everything given time. But I don't actually own or have access to any machinery without spending money ,you would not believe the things i'm expected to produce at work without such tools I usually design the thing and get it made out of house. I wonder if I can sneak in couple for myself. Hmmmm.

Here's the closest thing I could find on the net to a video of hydraulics made from lego pneumatics. Doesn't really show much but here it is anyway.

@ allanp

That release valve idea is purely genius! I have incorporated it into my design.

Thankyou!

Using hose with a smaller inner is a great idea, and so are his others. Makes me think it could work.

I'm a bit nervous about using any pre-made one way valve (such as those found in lego pumps and the distribution block) due to the slightly higher pressures. They could get very high but I will be limiting them to 60 - 100 psi probably, depending on the performance and how well everything works. A simple gear pump/compressor would be quite easy to make in Lego scale.

Edited January 31, 2011 by allanp

[DLuders]

As reported by Conchas on TechnicBRICKS, do you think that the upcoming Mindsensors "pneumatic control device for NXT" could be adapted for Lego Hydraulics? It says, "This Servo Operated Pneumatic Valve can be controlled from NXT using NXTServo-v2. The kit will include the valve, servo and necessary hardware and instructions to assemble the valve."

Edited February 1, 2011 by DLuders

[xsysiek]

I could use the last idea to make suspension for big mobile cranes like LTM11200 or for Buses like MB Citaro. Hydrokinematic suspension will be easy to build and could give fantastic resulsts. And no pump will be needed!

[Tobbe Arnesson]

do you think that the upcoming Mindsensors "pneumatic control device for NXT" could be adapted for Lego Hydraulics?

It's still the same LEGO valve, the only difference is that they've attached a non-LEGO servo to it.

[richthelegodude]

If anything pneumatic seals should be upto a liquid (air is a lot less dense) but the problem maybe pipes popping off.

I really do not suggest putting water in your pneumatic system. I tried that as a kid in the bath (I just submerged the whole system) but it ruined my cylinder as it went a bit rotten inside. If I remember right there is a little spring clip that keeps a rubber washer in place (which is actually the piston). If I remember the spring clip fell off, and I could never get it back on correctly after dismantling the cylinder. It was a long time ago and my memory is hazy, but it never worked well again anyway!

So there is a top tip, do not put your pneumatic system in the bath

[efferman]

the cylinder that you describe is the old one with one intake. the cylinders with two intakes have a X-ring which is pushed on the rod. the only probnlem which i could see is the popping off from the hoses.

[Zerobricks]

I've been followng theis thread a while now and it seems most of you are forgetting, hydraulics also requires return tubes, which current pneumatic doesnt have. When you open the valve in lego pneumatics, you also relase air from that valve (you can hear air hissing), and if you would fill the system with liquid it would simplay exit valve there resulting in a mess. The pumps would also have to be submerged in liquid. I have my doubts you can manage to do it with original parts.

[Tobbe Arnesson]

Yes, allanp has mentioned this already: http://www.eurobricks.com/forum/index.php?showtopic=51439&view=findpost&p=913081

[efferman]

we know, we know

the valves must be in the reservoir, that could it work like real hydraulics.

[allanp]

The problem of the ruturn circuit can be overcome by having the valve submerged in the resevior or by having them abouve the resevior. The fluid will come out as the cylinder pushes it out, as it was not compressed it SHOULD not spert out everywhere put just flow out nicely, depending on how much of an effect ballooning pips will have. Nethertheless they can still be submerged to prevent it sperting out.

As for submerging the pump, that is not a problem in itself, that's easy. But it has not been tested to see it the pump can actually pump the desired liquid reliably and without causing damage. It's understandable that it has not yet been tested here. But again, there are workarounds, like usuing one side of the small cylinder coupled to a valve in some way as to keep the fluid flowing in one dirction.

For me right now the main concerns are can it be done without damaging parts (like the one way valves inside certain pneumatic elements) and what is the best fluid to use.

[grindinggears]

After disassembling my excavator I could use my only compressor piece to build a mockup for a hydraulic system containing these components:

• compressor
  
• 4 valves (only two are used)
  
• piston to adjust the working pressure
  
• ungeared M-motor to power the compressor
  

more pics in higher quality on my flickr account

The system is supposed to sit in a containment that is filled with a liquid about 5 studs high. I had the idea to build a cover plate using these two elements: 1 2 but at first I didn't focus on that.

The system has four valves but uses only two of them. One is a pressure release valve which is powered by the piston at the top (credits to allanp for this idea!) The other one can actually be used to power a cylinder. It has a blue lever on top.

The system is expandable to as many valves as you like and in a six valve version there would be enough space to contain four compressor pieces.

The crucial part now is the choice of the right liquid:

silicone oil?

pure water?

distilled water?

I will ask Timo for an advice. He has used distilled water and alcohol for his hydraulic system.

And then we will see how it turns out!

(The purist in me screams: "No! You could lose your parts for nothing!" But my curiosity is bigger...)

[allanp]

Awwwwww please be careful with your parts, I hope you don't do any damage!

[efferman]

good evening, or should i say not so good?

Hydrauliks didnt work. The cylinder is leaking at the piston rod

maybe this is the only leaking cylinder, but i think using hydraulics for steering is no good idea.

[allanp]

good evening, or should i say not so good?

Hydrauliks didnt work. The cylinder is leaking at the piston rod

maybe this is the only leaking cylinder, but i think using hydraulics for steering is no good idea.

Oh dear! Well thanks for showing us the results. What fluid did you use? Looks like it was water.

I'm wondering if these cylinders are no good for this. Air is thinner and so it should seal a liquid, but then I guess you wouldn't really notice a tiny bit of air leaking, whereas you obviously would with water/oil.

[efferman]

The Fluid was pure german drinking water

well, the sealing of hydraulic and pneumatic cylinders is a little bit different, because they are completely different mediums. i had hoped that it works, but i have calculated with a fail

Edited February 12, 2011 by efferman

[grindinggears]

Great news: It works!

This evening I decided to test my hydraulic system (I built a smaller version to spare some parts).

It's only powered by a single compressor pump and an M-motor so we need some major testing until we have a concept that can be implemented by everyone.

The liquid is distilled water.

The system kept tight even when the top seal had to struggle with high pressure. As you see above efferman had some problems with a leaking top seal. I investigated that issue and tried to cylinders: One from the 2003 Backhoe and one from the 2010 Log Loader. The older one kept tight as long as there was only the compressor's pressure applied but some drops of water emerged when I pulled at the piston's rod. Even after I put some grease on it the piston remained leaky.

But the 2010 cylinder kept perfectly tight in all situations without any grease!

So the age of the seals matters when it comes to tightness. That's nothing new and you could still use the old cylinders for low torque applications or you could only use the bottom part (like in 8421).

The pressure regulator from allanp worked very nice. Let's see what happens when I put more rubberbands on it...

I have to test now what happens when the water pressure further increases. A second pump would come in handy here but unfortunately I don't have one :(

[efferman]

thanks for your test. i think i must select my fourteen pneumatic cylinders for the four new ones and test it again

[allanp]

This is excellent, well done.

Remember tho increasing the number of pumps will not increase the pressure, but it should increase the speed. Putting more rubber bands on the pessure regulator will increase the pressure. In fact, using a large cylinder as the regulator means the amount of resistance you put against it there will be the amount of power the hydraulics will operate at. If you have 4 kgs of spring pressure the cylinder should lift about 4 kgs. Alternatively you could use a small cylinder as the regulator. I believe it's pressure area to be about 1/4 the size of the large cylinder. This means that putting 1 kg of pressure there will translate to 4 kgs at the hydraulic cylinder, not accounting for the switch stiction.

The weights memtioned are only examples. Before doing any further testing to see what performance is possible personaly I would do some tests to see what pressures are being achieved. If it's 10 psi then go ahead and improve it, but if it's peaking at 70 psi then stop! We know that the pump (and it's internal one way valve) can cope with pressure of maybe up to 50-60 psi (which some of my MOCs have run at and depending on the cylinders, valves used). I've not seen these parts run at any higher pressure than 60 psi and so I can't tell you how they will cope.