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What are these thingies called?

  1. Nov 13, 2012 #1
    Sorry for the vague description. (I had to use Google to get the answer to the anti-bot question) I'm making a steadicam system and am wondering how to proceed with the arm. Problem is: I always scavenge rather than buy, so I don't know what anything is called. The arm kind of works like a race-car's suspension, but upside-down. the pivots are joined kinda like the pivot on a pair of scissors, but low friction/noise is very important. The arms are made of aluminium and I'd normally just drill through, cut a little thread on the end of a polished steel bar, push it through and put a nut on either end. (with lubed brass washers between the links of the arm where they would otherwise be in contact with each other. Surely there is a better way. For example, something like a skateboard bearing that can be secured into a hole in the aluminium somehow. Basically something that looks like a skateboard bearing with a flange on one end with some small holes in for attaching it to stuff. What would you call something like that? Does it have a name?
  2. jcsd
  3. Nov 13, 2012 #2
    Here's an interesting link for you. It's just a four-spring or four-bar arm mechanism. No special name, really.

    Very similar to an Anglepoise Lamp.

    What sort of load are you looking to hold with it? They aren't incredibly complex to build, but if the camera is light enough a stock lamp arm or a modified lamp arm (with stiffer springs) might be cheaper.

    Edit: Additional reading on balanced-arm lamps: here
  4. Nov 13, 2012 #3
    The lamp is fairly similar, except the steadicam has two arms, hinged in the middle. Each arm is rectangular and pivoted at each corner, with a spring stretched from one corner to the other. The idea is that, as the arm rises and falls, whatever is at the other end of the arm remains upright. No way a lamp arm could hold the camera, monitor, battery and counterweights.
    The design is no problem, all the aluminium parts will be easy to machine, and I'm sure I can get away with just a simple steel rod, threaded on each end, passed through the holes in both pieces, and nutted on the ends. I just think it would work better with some kind of bearing. I found something called a flange mounted bearing, which looks like it would work. But I can't find where to buy them in the appropriate size. Internal diameter would need to be 5 - 10mm. external diameter doesn't matter much...say, 10 - 25mm. The depth of the unit, IE, how far it extends beyond the flange is dictated by the thickness of the aluminium (3mm) It can be less than that, or a little more, but if it's too much more it forces me to use wider arms or a narrower hinge section.
  5. Nov 13, 2012 #4
    Sorry to double-post. After some Googling, I think the cheapest, easiest solution would be to insert nylon flange washers (1/4 inch bore. (I can cut off any unwanted length easily enough)) And brass washers.
  6. Nov 18, 2012 #5
    If I understand your question, you're (basically) just looking for an appropriate type of bearing to put into your arms? I think you're looking at a set of four normal roller bearings, but I don't understand what you mean about the flange or 'little holes'.

    To get what you're after (quiet, easy to move) I'd drill the initial hole slightly large for your threaded rod, countersink each side, and press in a roller bearing on each end. Your rod goes through that (needs to be a tight fit to work), with a washer between the arms.

    Nylon will work as you said, but they do tend to get a bit squeaky over time.
  7. Nov 18, 2012 #6
    I just decided to go with regular skateboard bearings. The problem was fixing them in place. I'm just going to slide spacers and washers onto the rod to stop the bearings slipping out of their position. I thought about shrink-fitting them, but decided a few bits of acrylic tube is cheaper than a stress-fracture. Maybe I'll use a little epoxy resin, but I really don't see the need now.
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