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View Full Version : [Question(s)] Dumb question, not "robot" related but robotics component related.



DomoArigato
09-09-2011, 12:39 AM
Hi everyone. My name's Lawrence.
I have a question related to robotics components. The reason I'm coming here is because I used to hang out with some dudes who were into Robotics; they could basically make anything to accomplish any task. I know you dudes are all pretty much engineering geniuses, so perhaps you can help.

I'm into luthiery/guitar building and repair.
One thing I find myself regularly needing is some sort of small, remotely actuated internal 'jack' that I can use to raise collapsed archtops, support reglued braces, etc. I come to find out that a company already makes a product for that task but man, they're charging a lot for what amounts to a small, hand-cranked scissor jack. I imagine I could build something at least as good for cheaper, for for the same cost but better.

Here's the link to what I'm talking about.
http://www.stewmac.com/shop/Tools/Special_tools_for_Bridges/Scissor_Jack.html

What I need is to figure out what standard, off the shelf robotics components could be used to achieve that same, basic task. Basically, the idea is a simple, small, remotely actuated jack.

Anyone have any ideas?

Thanks.

LT

DomoArigato
09-09-2011, 12:44 AM
Crap. Posted this in the wrong forum. Meant to post it in general. If a mod could move it, it would be appreciated.

Sorry. Dumb new guy :tongue:

Quantum
09-09-2011, 10:16 AM
Jack style lift like the one you posted is extremly strong for its size. Making something comparable out of motors and then fabricating a frame for it will most likely cost 2X-3X as much.
You actually need a pretty strong motor/actuator for something like this. And size is an issue here.

But if you want to build something your self a custom setup. Hydraulic/air type system would work best in this case, small cylinders and with manifolds and seperate controls your not limited to how many you can have.
This would be costly.

cire
09-09-2011, 04:11 PM
Using a flexible shaft is probably the cheapest way to do that task, and unless there were major upsides to having a remotely controlled motor that does the jacking (Which I don't think you'd want, because you wouldnt be able to "feel" how tight it is). I'd say your best bet is mimicking their design. You could probably make one for a bit cheaper, but much more time consuming.

DomoArigato
09-09-2011, 08:14 PM
OK, so electromechanicals are out.

Can anyone think of off-the-shelf components (gears/linkages/screws) that might allow me to use some sort of sideset thumbscrew to create a vertical jacking action? I actually have a full Taig micro lathe/mill setup, but I'm away from it right now, so I'm trying to keep it standardized.

Elegance and stupid-simplicity are OK.

DomoArigato
09-09-2011, 08:31 PM
Think a Machinist jack, but with some sort of side-control.

Stobs
09-09-2011, 11:11 PM
Hi Domo,

How about an alternative? You could use a bicycle pump - similar to this one (http://www.target.com/p/Bell-Air-Stomper-Foot-Air-Pump/-/A-10407103), for under $10 to $20. I selected a foot operated pump with a gauge and valve-stem lever; might be able to utilize the lever in maintaining pressure <shrugs>. Just need to make a suitable bladder to inflate inside whatever you're working on.

Regards

Quantum
09-10-2011, 02:01 AM
Your not going to find a 5 dollar solution. Just buy the jack and call it a day.

Really think about the amount of stress involved.

I'll leave you with this.
When you work on your car do you use a tire pump to raise your car?

No its a screw type device since its able to handle the force needed!

Stobs
09-10-2011, 02:10 PM
http://www.youtube.com/watch?v=
http://www.youtube.com/watch?v=bBuv7M4qdBg&feature=player_embedded

@Quantum: Think. You know better. Unless you've never heard of an air jack or air brakes, which I seriously doubt you're that uninformed.

You can just as easily over torque a screw/scissor jack as over inflate a bladder. I'm not into sensationalism so I'm not going to post any links, but just doing a search on "tire explosion kill" will find numerous links on just how powerful - and, unfortunately, deadly - air pressure can be.

Regards

Quantum
09-10-2011, 06:18 PM
Stobs the guy is trying to make something under 90 bucks.

I agree with you point on over torque things.

He wants the most control possible and force needed. Jack fits the solution.

A bladder is sloppy as you cant control the point your expanding as a jack can.

Stobs
09-10-2011, 07:37 PM
@Quantum: hmmmm... I'm thinking the pump and home-made bladder could probably be cobbled together for under $40 <shrugs>. Depending on execution and diligence I'd hesitate to use the term sloppy but, I agree with you that the retail item (or a well designed and fabricated home-built version), would be more precise - and likely offer more repeatable results.

@Domo: With all of this I have to wonder if you're getting paid to do this work? If so, you're technically a professional. My Pop always told me that it's not only knowledge and experience that separates an amateur from a pro, it's also having the right tool for the right job, and quality certainly counts in that consideration.

Regards

DomoArigato
09-11-2011, 12:20 AM
@Domo: With all of this I have to wonder if you're getting paid to do this work? If so, you're technically a professional. My Pop always told me that it's not only knowledge and experience that separates an amateur from a pro, it's also having the right tool for the right job, and quality certainly counts in that consideration.
Regards

"Paid" as in the luthiery? Not on this job, no.
An air bladder may actually work. We're talking about wood here- no serious stresses involved. In raising an collapsed archtop, for example, it may actually be preferable to a metal jack of any kind.

cire
09-11-2011, 01:38 AM
Air bladders can lift tons of weight, since you have have a really large "bore" at low pressures, like a 100 square inch bladder at 90 psi will lift 9000 lbs. You would be limited on your "bore" size by how small you want your lift to be, and you can stack multiple bladders on top of each other to increase the total travel you want. I think the total travel distance would be your biggest issue. I am not sure where you can buy small ones, though.

Stobs
09-11-2011, 11:36 AM
Good points cire; knew about the low pressure but not about the bore ratio. Not sure that I'd consider 90 PSI low for an inner tube-based bladder - not that it has to be made from one but, it seems the easiest and likely handiest material to use.

In regards to the spacing issue, there's also another alternative to the stack of multiple bladders - a good choice, as cire has pointed out. If you cut two short chords from a bicycle tire (one with the valve stem centered in it's length), you could glue them together, forming a shape much like an elliptical spring.

http://www.iowavalleycarriage.com/sites/Files/ivcs/imagecache/product_full/seat spring.jpg

This would let you put various sized spacer blocks in the middle - just bore/notch them at least on one side like an arch-shaped child's building block so they'll hold position.

Three problems with this:
1) Left as is, the valve stem will protrude in the direction of greatest expansion - by sectioning the valve stem area you could rotate it 90 degrees (just ensure you've left enough length of tubing on either side of the valve stem to patch with).
2) Since this is cobbled together you're going to have a lot of patches, which adds bulkiness, stiffness and points of failure.
3) Might be a more sophisticated solution but, even to me, it's a bit over-thought; simpler to just have various sized bladders.

Regards