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Where To Mini Hydraulic Shocks For Arm Support?

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#1

As you may have seen my HD-7 arm in my thread. Im using a spring to assist the servo when lifting the hand/forearm up. spring works fine but I like the look of hydraulic shocks. any one know where I can get my hands on some?


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#2

Have you looked at hobby shops that sell R/C race cars? Particularly the off-road stuff? I am sure I have seen small functional shocks on the wheel sets of R/C all terrain vehicles.

Alan

#3

off-road shocks, 1/8 scale size, might be long enough but could cost quite a bit...

judging from the size of your robot you could possibly also look into rear tunk hydrolics for cars

#4

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something like this?

#5

i found some cheap 1/8 scale shocks made by my sponsor Team Associated. you can buy a pair for $20 and a set of 8 for $75. I'm not sure on length but this is a cheap option considering you can change the oil, dampening, and springs easily

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#6
#7

Hi, this is my first reply (been watching the site for a while).

An RC shock might not work in the configuation that @aameralis is showing because shocks with springs push back, not pull. You would either have to put the shock at the back of the arm (to use with no mod.) to push the elbow to bend or rebuilt the shock to have the spring in side the piston chamber so it retracts (like a single action pneumatic piston with a spring return).

Steve

edit- This shows the back of the arm push (sort of)
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edit2- Single action piston

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#8

I agree with above. He beat me to it. Smile

#9

In fact, won't a shock actually give resistance in both directions, just more in one? You may want to continue using a spring to assist with the lift, but fabricate it in such a way as it looks like a shock, just without actually providing any dampening (maybe two diameters of PVC pipe that telescope into each other, with the spring around the smaller one providing the compression tension).

Alan

#10

Im thinking of a compressed gas type like on lift assist units on trunks and car hoods.

Like this one. Except it is too much lift I think. On second thought, maybe not. If you look at the C3PO as an example, there is a lot of mechanical disadvantage to overcome. So more lift would be needed anyway. Once you know the total arm weight and the center of balance, it will be a snap to figure the length the attachment behind the elbow needs to be.

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Adding to Alan's suggestion, you could look at the spring mechanism used on screen doors that protect them from flying all the way open. Hide it in PVC to look like a piston. Essentially like Steve said in his Edit#2.