ServoBlocks for KAP rig?

edited November 2011 in KAP Gear Sources
These look like they might be useful for building simple KAP rigs. It doesn't say what load they can handle, but they look like they could handle a light P&S if not too levered up. Easy to attach to other things too.

http://servocity.com/html/standard_hitec_servoblocks.html

(Unaffiliated)

Matt

Comments

  • I think a really nice horizontal / vertical axis could be built with one of those Servo Blocks. It certainly takes all the side load problems out of the equation. Hmmm! Need to think about this for my next rig.

    One thing with the Servo City pan/tilt heads: They're not balanced. I'm using one for another project, and it's potentially going to be a problem. The weight of the camera and lens is cantileivered way out in space, so the servos are under real load much of the time. Most KAP rigs are built to be balanced. This means the center of gravity doesn't change with the position of the servos, but it also means that the servos aren't loaded most of the time. It lets you use smaller servos, and leads to longer battery life.

    Tom
  • @Yaniv - you're right, I hadn't seen, but there is a bunch of other stuff that look useful on that site.

    @benedict - understood on the balanced part, which probably limits the ServoBlocks to being useful on a single axis.
  • Hey, I'm gonna have the chance to play with some of these!

    There's a project I've been working on for another photographer. Not strictly KAP related, but it uses a lot of the same hardware. They wanted to add a roll axis to a camera mount to level the horizon, and I remembered this thread. So I ordered two sets of blocks. One is for their project, and the other is to see if I can add a HoVer axis to my existing DSLR rig. Both of these will be for the Canon T2i, so they'll need to move similar mass and moments. I had good luck using the metal geared Hitec servo Brooks sells on my KAP rig's tilt axis, so I picked up two of those as well.

    I should be able to start putting all this stuff together next weekend. Pictures to follow.

    Tom
  • Ah, great, I look forward to hearing about them, Benedic. I've been meaning to buy one, but haven't had the time...
  • Just got word they shipped. I'll take pictures as the work progresses over the weekend.

    Tom
  • Everything arrived today! Sorry, no camera with me, so I can't show you any pictures of the bits 'n pieces yet. They come un-assembled -- slabs of aluminum and a bag of screws -- so some assembly required. Perfect for a KAP rig! Just from a first-impression, these things are beefy. They're bigger than I thought they would be, with plenty of meat on the final output bearing. There's a good chance these would make a good HoVer axis for a KAP rig. That's precisely what I had in mind for the one I got for myself, so I'll let you know how it goes.

    I probably won't have a chance to start construction until Wednesday, but I might be able to squeeze in a photo session of all the bits and pieces before then.

    Fun stuff!

    Tom
  • edited March 2012
    I went home at lunch, so I photographed one of the servo blocks being built out:

    Servo City Servo Blocks

    The upper left panel shows the Hitec servo as it came from Brooks, along with the ziploc bag of parts as they came from Servo City.

    The upper right panel shows the bag opened, with the parts spread out. They're made from some pretty chunky bits of aluminum. For the price, it would be tough to make something like this at home or even in a home shop and be competitive. This is a really good price for what comes in the bag.

    The lower left panel shows the servo block completed. This took about four minutes to do. Four screws hold the frame to the servo, eight more hold the frame together. The screw that came with the servo went down the barrel to hold it onto the servo. When ordering, you can specify Futaba or Hitec. This is because the output shaft is splined, and the two are not identical. It fit very very well. My hand fits a large glove. This should give you a sense of size.

    The lower right panel answered a couple of questions I had about how easy these would be to add to a KAP rig: You can see the vertical members have countersunk holes on the back side. So you can bolt that face to another part really easily, without causing interference between the screw heads and the servo shaft. The other question this answered for me is whether you could just bolt this to one of Brooks's parts, and still get clearance on all the screw heads and rotating bits. The answer is a resounding yes. There's actually plenty of room to work with. And finally, I wanted to know how tight their tolerances were, and how big that output bearing was. The answers are "tight" and "BIG". I honestly think this would work well for a HoVer axis with no real modification.

    In case someone other than me is taking a good hard look at this, yes: all the screws necessary to put it together came with it. But no washers. Let me put that a little more bluntly: NO WASHERS. And using this length of screw, there's really no room for washers. So if you use one of these on a KAP rig, installing the screws with a good thread locking compound is almost a must. No, take out that "almost". Use the thread lock compound, or expect to see parts falling off your rig some time in the future.

    The screw that comes with the Hitec ball bearing servo Brooks sells does come with a lock washer. (It would be a bad idea to use thread lock compound on a servo screw, anyway.) Nonetheless, I'm the paranoid type who always flies with a safety lanyard. In the event the servo screw fails (which I've never seen happen) and the spline comes loose (which it shouldn't since it took main force to install it in the first place), a lanyard between the camera and the main frame of the KAP rig would keep things from falling off.

    All in all I'm impressed with the quality and heftiness of the Servo City servo blocks. Next step: Install one of these on a Brooxes Utility Frame, and see if I can make a direct-drive HoVer axis out of it.

    Tom

    P.S. The full size image, available on Flickr, is about 3000x2000 pixels, so if there's something you wish you could see better in the photos (like the hairs on my knuckles), there's plenty of room to zoom in.
  • edited March 2012
    Thanks for the great write-up and pictures Tom. Do you know how much these components weigh?

    (Nice hands)
  • edited March 2012
    I recently got a few of these for pan/roll/tilt rigs (Canon Rebel and Sony Nex-series). I got the Futuba type with hub and am also pretty happy with the construction.

    With the GS1 servo the assembly is 79 grams. So by subtraction I get ~ 40 grams for the aluminum servo block (the website says 1.3oz or 37g). As the rest of my rigs are carbon fiber I'm thinking of this as something I will replace at a point in the future. In fact I'll probably model the carbon fiber replacement part after one of these.

    I agree with the need to replace the machine screws with longer ones + lock washers.
  • I'm going to do the work on these this weekend. Pictures to come.

    Tom
  • Did this project ever get forward? Servo blocks look definitely interesting, just wondering if they've been already been proven in flight.
  • Indeed, the Servo Blocks look interesting but there the story stops for use in KAP, I think. These blocks are way too strong and thus very heavy. There are several ways to get the same result cheaper and lighter. Like with the Brooxes Better Gear Guide.
  • edited November 2012
    Sorry I never posted on this again...

    They do work. I used a set on a camera rig that sits on top of a robot platform, and it worked quite well. I needed more rigidity in that setup than the BBGG is designed for. It also made for a slightly more compact package than the BBGG, which was also important in this case.

    The real benefits of the servo blocks are that they're relatively compact when compared to the BBGG, they have no additional play in the axis because there is no additional gearing, and they are rigid enough to be used as a cantilevered axis without any additional support (e.g. a tilt frame that's only supported on one side.) For that robot application, it was a really good fit.

    But I think Peter's right that it's not necessarily a good match for KAP. There are two main reasons why:

    First, even though a servo plus servo block is a more compact arrangement than the BBGG, most of the weight pokes way out in space. This can make balancing more challenging. It also makes for clearance problems if the servo needs to swing inside some other part of the rig. Here's the HoVer axis on my A650 rig:

    Subtle as a Dump Truck

    To make this work with the servo block, I'd have had to add extensions to the main frame on my KAP rig. There just isn't enough room in there.

    The second reason is that I don't think KAP benefits from ultra-rigid setups like the servo blocks. And when a rig comes down hard (I won't say "crash") the more flexible rig wins over the ultra-rigid rig because it does a better job of dissipating the impact forces. Ultra-rigid rigs tend to carry those forces straight to the camera.

    KAP Rig Crash 1

    This was from my Flow Form 16 inverting and power-diving into the ground. The KAP rig was pulled, upside-down, onto hard asphalt from about twenty feet. The rig was bent all to hell. But because all that energy was absorbed by the rig, the camera survived just fine.

    There's one thing the servo blocks do very very well that could be pretty neat on a KAP rig, though: they provide an axis that doesn't need any other support. Most KAP rigs are design as a U within a U, with the tilt axis being supported on both sides. Given something like the servo block you COULD make a rig that uses half the framing a normal rig would. I don't know if you'd WANT to, but you certainly could. It would be a neat experiment.

    Tom

    P.S. After that crash I was able to strip the rig down, bend everything straight, and put it back together in about an hour. I don't think you could do that with something like the servo blocks. Chalk another point up for bendy KAP rigs.
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