looking for suggestions for a pan tilt mechanism

As of now I am at a loss as of any design to do this that isn't too difficult to build to make it worth the bother. I want a pan tilt
mechanism, to pan and tile a small bullet camera on top of a radio tower. The tower has a 2" diameter mast and I want the camera to pan around the mast. The camera is 3/4" in diameter and 2 1/2" long. The main difficulty I am having is how to make a housing that will connect to the mast using set screws and then the outer part will rotate around the mast. For Tilt I was planing on having the camera mounted on the end of a small shaft with the other end coupled to an RC servo. For the pan I thought I would use a simple DC gear motor with limit switches to stop it from moving too far. The part I can't seem to get any ideas for is the housing and panning mechanism. Any suggestions? I will be happy to share all 3D models and detail drawings I make once I get this figured out if anyone wants them.
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Chris W
KE5GIX
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Just some quick thoughts here...
I'd perhaps move to use the same mechanisms for both pan and tilt. Us a converted RC servo (as used for drive wheels in play robots) as your drive motor, make it so that it drives with friction (rubber tire on it) around your "track", so that it will freewheel against a track stop at each end. You can then input accurate pan movements using the same software/hardware as for your pan mechanism, and recover from accumulated error by driving against a stop once in a while to reset your known position...
I'd bend a piece of T section as my track... Clamp to pipe with top of T facing outwards (shaft of T horizontal, risers to clamp, or set-screw blocks against pipe... build a cart that rides around this, Small wheels on top and bottom inside surface of the T, and one servo friction wheel as the lower (outer) support and drive ... Gravity will compress your top inner wheels against the inside of the T, and your lower outer drive wheel against the outside bottom... On the cart you can mount your tilt mechanism and camera.
I'd not bother with a "housing" assuming the bullet camera is waterproof. Grease up the servos and with the pan one mounted upside down, perhaps a rain shield on top of the cart for a bit more protection, you should be good to go with only minor weather proofing for any electronics you mount on the cart.
Aluminum parts would be one bent T section hoop, bar sections to use a risers... thicker bar sections to use as set-screw blocks. bit of plate (taller than top of T section) to use as your cart, with little blocks screwed on to mount your wheels to... other little bits as required.... Use sealed bearings as wheels, RC Aircraft wheel to mount to servo as friction drive...
I suck at ascii art so if you want more graphical input on this, get me your email addy and we can talk...
Al...

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Looks like you are the only one that read the part about how I wanted the camera to rotate around the mast. Interesting idea. The reason I was going to use simple DC motor for the pan part is because i can't think of any way to set up a limit switch to stop the servo motor from going one way and still let it go back the other way. If I have 2 STDP NC limit switches that cut the power going to the motor from one set of wires on one side and a second set of wires on the other side, I can then use a DPDT (on) off (on) switch to send the power to one set of wires or the other, wired to have the reverse polarity. Seemed like the easy way to me.
All that said I am reconsidering my rotating around the tower idea. The reason for rotating around the mast, was to prevent the mast from being a blind spot, but even with that, the ooax going to the antenna(s) would have been a blind spot and more than one as antennas were added (up to 3 potentially). If I just have the pan off the side of the mast, then the only blind spot will be the mast. And if I ever get a directional antenna up there and a rotator I can rotate the whole mast if it gets in the way of the camera. On top of that, I just found out hitec has a new servo designed to be used as a winch for sail boats that will rotate 3.5 turns instead of the standard 90 degrees that most servos do. Combing that with the 3:1 gear reduction drive that servocity.com has, and I have the perfect way to pan a full 360 plus a little. I will put that servo with the gear mount in a box with the electronics. Maybe have the tilt servo exposed the elements. You can get servos pretty cheap so if that one fails it won't be a big deal. I am debating just putting a little RC plane receiver up there so I don't have to run as many wires back down then when I want to pan and tilt it, I just turn on the power and use my airplane transmitter.
I did finally come up with a very bad design. The housing wasn't for the camera it was for the servos, pan motor and electronics. Here is a screen shot of it.
http://www.thewishzone.com/priv/PanTilt.jpg
Alan Adrian wrote:

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Chris W
KE5GIX
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An extremely rugged pan and tilt can be made from elbow pipe fittings with threads doped with silicon grease. You are left with attaching two shafts internally to provide the drive.
Brian Whatcott Altus OK
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Chris W wrote:

I haven't read it in detail, but the latest issue of PCMagazine has one of these as this issue's DIY project (oddly enough, to put a remotely-controlled pan & tilt cam on one's doghouse). IIRC, it has a store-bought component that is the bracket for the servomotors, but I am sure it is something that can be made without too much difficulty. It may be on pcmag's website. www.pcmag.com -k wallace
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On Mon, 09 Oct 2006 11:54:45 -0700, k wallace

Sure enough, a tilt servo perched on a pan servo with an eyeball webcam on top - pictures here....
<http://www.pcmag.com/article2/0,1895,2021380,00.asp
This doesn't seem specially ruygged nor waterproof though. Around $120 apparently.
Brian Whatcott Altus OK
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