Air wouldn’t be a good media, but could a light liquid, work?
My idea, is to have 2 syringes connected by tightly sealed hose, one syringe open and closed by the servo, the other in place of a linear actuator.
Just get some with a removable needle so a hose can be attached.
Let me know if any of you guys tried it, if not i’ll give it a try in a month or so, i don’t have syringes readily available to me, and deal extreme takes a month to ship, less time if i spend over $10.
The yellow is oil, and thats a hose between the two syringes.
Any ideas if it can be done?
If some of you are diabetic or something, you could save a couple needles and remove the tips if they are indeed removable, and then give it a try, Or trim the tips off. But please be careful.
If you guys try it, make sure to test it a hundred times or so.
I placed an order for syringes, but it’ll take a few weeks to get here from hong kong.
I’m going to need to find some small light weight hose now, smaller and finer than fish tank hose.
Hudraulics with syringes can be done! I did it for an animated model once, but not with servos…
A quick Google search for “syringe hydraulics” produced many useful references. From robotics with syringe hydraulics to instructions on making them. Like this one: teachergeek.org/hydraulics.pdf
Neat, I ended up buying four packs of these, dealextreme.com/details.dx/sku.22301
was like $5 and some change.
I only needed 2 packs, but i goofed up a little.
I went with 2.5ml ones because i want them small and hopefully with less resistance.
I just hope that my micro servos will be able to pull this task off without to much trouble.
I’m going to test 2 myself once i find some fine enough silicone or latex hose, if they don’t work, i’ll just give the rest of the unopened syringes to my cousin that uses them for arthritis medications, or someone with diabetes, as spares.
If it works out well, i may actually make part of my quadruped bot, using these.
The knee joints, so i don’t have big bulbous servers at the knees, on little craft stick legs.
I have just completed the design of a vacuum powered gripper. I’m still gathering components, but it should be ready in a few weeks. Here is an image of the thing.
When I decided to try this I went to my local CVS drug store. The nice lady gave me 2 5ml oral syringes for free. That’s in your price range eh? They worked well. I opted for the 10ml version for the production. It just has more pull. While I’m using air, I think it would work with a syringe on each end and a light oil. You may be able to amplify the force at the cost of throw by using dissimilar cylinder sizes.
Also be careful when ordering syringes. Some lock in place if plunged fully in.
Your vacuum gripper is what gave me this idea.
I may pick up a couple syringes at a local drug store, hopefully for free too.
Even though i ordered some, i’d at least like to get started on my quadruped bot.
I didn’t know some lock in, Now i’m sorta worried about that, Though i could just make it so it doesn’t go in all the way.
I just got my servos today, they were cheap, but no DOA’s which is nice.
They are much stronger and faster than i expecting. Which is a nice bonus. I just hope the plastic gears won’t be a problem.
If all works out, i’ll be making a hexapod eventually.
I need to get the rest of my budget for September before i can get started.
I’d luv to try a cable-driven hand w fingers, the smaller sizes look like they’d be perfect, and all the associated fittings and pulleys… all I need is funds!
Hydraulics tend to be heavy, and … they can leak. They DO leak. Transmitting any kind of force means that the hose will be under greater pressure.
If you do get one up and working, I’d luv to see the details.
Ya i wanted to do cables before.
I still haven’t gotten any syringes, i had to cancel the order i had placed earlier.
The timing just wasn’t right for my budget.
Right now i have a lot of projects going on, and not a lot of time.
But pretty soon i’ll have a page at the Basic Micro blog for all my projects.
Including an Atom Nano 18, mini botboard.
A gameboy advance SP controlled 2DOF hexapod using a mini botboard for the Atom pro 28.
I’ll have a video of that up as soon as i make the thing wireless. Need another bluetooth adapter for that.
Depending on the item being picked up, have you considered using a tacky sort of glue, with a servo-operated probe/plunger to get the item free when it is positioned? There are some excellent sticky substances that don’t leave a residue and are easily dislodged/unconnected. For cardstock or similar lightweight items, picking up ONE works great. And it is a whole lot simpler than vacuum or hydraulics.
'Course this only works on really lightweight objects, but it might be something to consider.
Well, it would be excellent for clean paper or even playing cards, but the whole syringe hydraulics was actually intended to be used as a narrow form of push/pull point, like the hydraulics on a farm tractor, back-hoe or shovel loader.
But instead of using a fluid pump and valves, it would use a secondary syringe as the pump itself along with the servo.
The point would be to bring the mass of the servo into the center of the contraption. So you don’t have this large block sticking out of the knees of your robot for example.
This wouldn’t be as much of an issue if they made stronger low-profile servos though.
My hexapod is small, infact i had to redesign it 3 times because of servo positioning, and the fact that the servos were so close together they would bump into eachother.
By bringing the servos into a center point, and using hydraulics, i could create these push/pull points without the issue of servos bumping into eachother.
I know just what you mean. I’m not wild about the ‘huge knee-bone’ servos make either, and I did put some thought into how to slim down the legs and bring the center of mass way up into the hip. Never got anywhere with this, but I did consider cables, linkages, and just about everything else except hydraulics.
My final position was that cables/pulleys offered the most promise, but I haven’t had the funds to explore this option. That small company (see above link somewhere in this thread) seems to have the hardware to do it. This does require a very stiff aluminum exoskeleton - not a real big problem with a jigsaw and a vise.
To me, hydraulics sounds like it is better suited to a non-mobile bot. Hell, get an AC motor/pump, make a custom manifold, add in some valves, and you have some real power at hand. And alot of weight. Perfect for a stationary bot, not so perfect for a mobile bot. I think that hydraulics don’t scale down very well, while cable/pulley systems do scale down rather well. A linkage system, while it may work, seems overly complex.
I haven’t played around with muscle-wire or nitinol, and while they are cool and small enough, I question whether it has enough power to be useful.
Hydraulics kinda falls into the same catagory, way cool but (at the small scale) questionable power.
I’d love to be wrong about this. Integrating standard servo use with linkage, cables, and hydraulics might make it more of a Rube Goldberg device, but you’d have the coolest fragile robot on the block!
Legs without the bulging knee syndrome… Of course it has the bulging hip syndrome. lol We never got around to making a smaller chassis to hid the hips.
I think what we all need, are powerful low profile servos. robotcombat.com/products/0-HRC31077S.html
The size is right, it’s the torque that isn’t. Though i’ve seen some other stronger low profile servos around too, i just didn’t bookmark those, one did 8kg/cm at 6v.
Hey RobotDude i think i found something you might be interested in. Full turn servo
Not to be mistaken with a continuous rotation servo.
You posted a thread about smooth servo control. viewtopic.php?f=6&t=4362
But you kind of abandoned it, there was never any follow ups or how-to guides.
You mentioned a wrist servo, where there you go, a full turn servo. It would also be good for the base.
rotation servos don’t need anywhere near the torque of a lift servo, but even then that full turn servo offers roughly 7kg/cm at 5v.
They are currently out of stock, but you probably have the resources to find them. Hobbypartz.com offers some sailboat winch servos that will do 3 full turns.
The problem is I had the project in two threads. I went back and added the instructions for moding the servo. It’s a simple hack…
I have experimented with sail winch servos with less than impressive results. I have not tried the single turn servo, but it has the futaba spline, so it won’t fit into our injection molded base.
It was an old thread, but i found it now. So the pot trick doesn’t look to hard.
The single full turn servo caught my attention because it would offer good turning radius, and should still be easy to control.
I haven’t tried any of these special servos, for obvious reasons. It’s just something i might do for the basic micro blog at some time. Except wireless.
Now if I could just shorten up the stack-up (shorter spacers). I’ll probably just make a custom offset C bracket that’s wide enough to take the Blackfin boards.
I’ve already designed a wide C bracket to take the line camera.
I’m not sure about that particular servo, but keep in mind, many full turn, or multi-turn servos like sailboat winch servos, still use pulses between 0.5 and 2.5
Which means the pulse differences have a much greater difference in how far it turns.
IE you’ll need to make smaller changes in turning, and possibly at a lower speed.
I looked into it a bit, like i seen some 3 turn winch servos that still worked off of 0.5 to 2.5 for the range of all 3 turns.
That’s true, the pan may not be as smooth with the extended range.
The 180 range for a pan is not bad a camera on a 'bot, but if one was implementing a SLAM sensor, then the full rotation would be wanted (actually continuous would be better). I think I’d go for a DC servo motor with an encoder (with index) in that case.
They worked well. I opted for the 10ml version for the production. It just has more pull. 
While I’m using air, I think it would work with a syringe on each end and a light oil. You may be able to amplify the force at the cost of throw by using dissimilar cylinder sizes. 
