MH technology ?

Falk · Post by **Falk** » Mon Nov 15, 2004 10:15 pm

Plop^^

In the making of the CG phantom, I'm stuck looking at the resin kit arms.
The way they're done doesn't see to able all the human movement, particularly the front arm rotation (front arm is made of 2 bones, so it can rotate at about 160° I think), on the kit, the front arm is made of only one "bone", with several "power cylinder" mounted on it, so it can't turn that much, or the power cylinder would twist and break

(unless the power cylinder are made to turn slightly around the arm bone, and well combined, they can rotate as well as oriente the hand).
There's also a problem with the shoulder rotation. On the kit, the arm armor hasn't enough place to rotate in the big shoulder armor. I can correct that in 3D, but the joint is weird anyway, my guess is that all the shoulder power cylinder (3 on the kit) work together to orientate the arm. There's not much place in it, but there's the shoulder armor, so if everything intersects when it moves, I won't care much as long as it's not visible

.
If you look at smokewalls, he cheated a bit as the bende arm has

But before I think of how to change that so it can move, I need a bit more knowledge about the power cylinder system.
Does it works like some pneumatic jack ? Just with another energy ? (btw, what flows in the by-pass cables ?)
Or is it something more complex ?
Is it all metal ? Or may there be some mysterious hard material that can bend anyway ?

Nu Soard Graphite · Post by **Nu Soard Graphite** » Mon Nov 15, 2004 10:21 pm

I remember reading a little about the Power Cylinders on the old Wax Trax message board and basically, the difference between Power Cylinders and Hydraulics (used today) are that Hydraulics do not work on both the push and the pull...there has to be different Hydraulics oriented to do either work...but a single Power Cylinder does work on both Push and Pull. I'd also imagine that the power-to-work ratio is extremely efficient.

RO3159 was working on the Internal Structure of MH article for us, but has taken a break and he hadn't gotten to the part about Power Cylinders yet, so we don't have all that information yet.

Hydra Mirage · Post by **Hydra Mirage** » Tue Nov 16, 2004 1:20 am

I think there is a reason why most of Nagano's designs are fixed pose kits....

Most MH's seem to have very limited joint movement.

But then again, I don't think mobility should prevent a great MH design.

cobywan · Post by **cobywan** » Tue Nov 16, 2004 5:57 am

Modern hydraulics work on both the push and the pull. You are just pushing from the other end of the cylinder.

Nu Soard Graphite · Post by **Nu Soard Graphite** » Tue Nov 16, 2004 11:08 pm

cobywan wrote:Modern hydraulics work on both the push and the pull. You are just pushing from the other end of the cylinder.

Yes, I found out today that sometimes this is the case. They use vacuum power to "pull" in the oposite direction...

cobywan · Post by **cobywan** » Wed Nov 17, 2004 1:19 am

I'm thinking in farm tractor terms here. They literally push oil into either end to make the cylinder move.

Nu Soard Graphite · Post by **Nu Soard Graphite** » Wed Nov 17, 2004 3:35 am

cobywan wrote:I'm thinking in farm tractor terms here. They literally push oil into either end to make the cylinder move.

Yes, thats what I was thinking, and technically, thats not working on the Push and pull...thats pushing from opposite ends. A good example would be pushing a car down the street. If you and a buddy were each on opposite ends of a car, one of you could push it one way, then the other could push it the other way as needed. Even though you can go both directions, the initial action is still a "push". Dual sided hydraulics work in this fashion as well...it pushes in opposite directions to get the desired work.

Animal muscles work in the opposite fashion. They "pull" to do work. On the human arm, the Biceps contract to pull the arm inward. Then the triceps contract to pull the arm back into the straight position.

Back on Wax Trax, someone said that the Internal Structure of MH article stated that Power Cylinders work on both the push and the pull. I was thinking that Hydaulics only work one way (unless its a double set-up, which some of the Forklifts I use at work have that) on the push, but a friend of mine today (who is a mechanic) told me that some rare hydraulics can use the vacuum created as the hydraulic fluid is withdrawn to pull the piston back into place, so yes, some hydraulics can work on the pull as well. Unless my friend was completely off base...

Anyone here an expert on mechanical/hydraulic systems? I got some training on them in the navy (we had to learn all the systems on the Submarine in sub school and hydraulics was included) but that was 17 or so years ago for me, so I don't remember much.

SteamTrooper · Post by **SteamTrooper** » Wed Nov 17, 2004 1:22 pm

[quote="Nu Soard Graphite
Yes, thats what I was thinking, and technically, thats not working on the Push and pull...thats pushing from opposite ends. A good example would be pushing a car down the street. If you and a buddy were each on opposite ends of a car, one of you could push it one way, then the other could push it the other way as needed. Even though you can go both directions, the initial action is still a "push". Dual sided hydraulics work in this fashion as well...it pushes in opposite directions to get the desired work.

Anyone here an expert on mechanical/hydraulic systems? I got some training on them in the navy (we had to learn all the systems on the Submarine in sub school and hydraulics was included) but that was 17 or so years ago for me, so I don't remember much.[/quote]

SteamTrooper · Post by **SteamTrooper** » Wed Nov 17, 2004 1:40 pm

Well I am no expert - I have used them and know a little - but in laymans terms - the push n pull thing is best classified by the source of the fluid or `power` - on a dual hydraulic system the internal structure is such that it is quickly altered to allow the fluid to be re-directed into the opposing chamber but still from the same source - so rather than your analogy of two people on opposing ends of a car - both of which can push - it is probably better to think of it as one man with very long arms who can choose to pull the car or push the car.

Alternatively - a system of two chambers - one at each end of the Piston can be used - this requires a mechanical linkage from the piston to the area to be moved but is an economical and powerfull way to use hydraulics - eg. take two open pringles tubes and place a smaller closed ended cyclindrical tube inbetween - if the fit is tight but not too tight - you should be able to gently squeeze either tube and have the inner tube move away from you - add to this the vacumm created in the tube and when you let it go, the inner tube will move back - this is how the two chamber principle works - the fluid is naturally drawn to where it is required by the force of the other chamber action.

Hope that helps a little in things and wasnt too boring.

Shadowbrooke · Post by **Shadowbrooke** » Wed Nov 17, 2004 7:37 pm

If you guys want to I can ask the guys at work, I work with NDT lvl II stuff in the oil industry and we have lots of hydraulic systems on our ROV's and their support systems. They probably think I am crazy for asking though

I took a Navy class back in -98 as a commercial diver but I don't remember squat from that class, it was one of those required classes that we needed for our cert but we never actually used it so...

Shadowbrooke