Light-duty (and cheap?) pan and tilt: any interest?

Phil Pilgrim (PhiPi)

I've come up with a light-duty pan and tilt mechanism that relies on a pair of GWS Naro (Parallax Pico) miniature servos. It's made of laser-cut 0.093" clear acrylic and assembles easily with lock-tabs and screws. It can be configured in two different pan/tilt modes and one pan-only mode. The various configurations are illustrated in the attached photos. The zip file contains a video that shows it in action mounted on a Boe-Bot.

The base is designed to mount to a vertical surface and has two vertical slots for #4 screws an inch apart. The top piece includes a 1/4" center hole and various peripheral holes and slots for #4 screws.

Is there any interest in such a thing? If so, how much would you be willing to pay for a hardware-only kit (excluding the servos) that includes the twelve acrylic pieces and the fasteners required for assembly? 'Loaded question, I know, but an honest answer will tell me whether it's worth pursuing further.

Thanks,
-Phil

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Post Edited (Phil Pilgrim (PhiPi)) : 1/17/2010 7:21:59 AM GMT

Ken Gracey

Excluding the servos: $20-30 seems about right. With servos $39-49.

Those particular servos cost Parallax about $8 each, just so you know. . . penguin actuators.

Would sell reasonably well, but I'm wondering if this is better done in sheetmetal. Such a design idea has floated around our office for quite some time though we never acted on it. But nobody has made the design and here you are with a solution.

We'll take 50 units. Anything that mounts on the Boe-Bot is usually a winner. It's probably the second most popular hobby-education robot (I imagine Mindstorms is first).

Ken Gracey
Parallax Inc.

Phil Pilgrim (PhiPi)

Ken,

I can't disagree that sheet metal could be the more appropriate material for this. But, as you know, I've got a new hammer, and I'm looking for nails to pound with it. If it were done in sheet metal, I presume you'd use servo horns to get the splines, right? If the splines were broached in the metal, there'd still have to be a second layer of sheet metal to hold it in place. Anyway, I'll mull it over, see what kind of feedback comes from the forum, and maybe send a sample down Rocklin-way for an eval. (If you can't already tell, I'm really on the fence with this thing.)

Thanks,
-Phil

kf4ixm

I think these would be a great idea, both the acrylic (for light duty) and sheet metal or machined aluminum (for standard/heavy duty) using the word heavy loosely here, all relative to the servo. these would be great for the ping))) module, the 10 deg fov ir therm., and especially the small 2 channel wireless bullet camera system i have just chompin at the bit to be married to a servo p/t.

Scope

I'm not a big fan of acrylic anything but I love the idea of a micro P&T outta sheet metal

I've been using these - and at less than $3 each . . . I'm thinking of using a metal Altoids box and making something similar but I don't wanna buy any Altoids . . . yes, I'm incredibly cheap . . .

www.hobbypartz.com/topromisesg9.html

Post Edited (Scope) : 1/17/2010 3:11:21 PM GMT

Phil Pilgrim (PhiPi)

I've discovered an issue with these tiny servos that bears on any pan/tilt mechanism built with them, whether it be from acrylic or aluminum. While they have plenty of torque to move a static load, they lack sufficient stiffness to move an inertial load without jerkiness. Part of this has to do with the small diameter of the output shaft and its torsional flexure. The solution appears to be damping. Viscous damping would probably be the best, but it's hard to implement cheaply, AFAIK. I resorted to frictional damping instead. To do this, I went to the hardware store and purchased a self-adhesive felt pad, the kind you'd put on the bottom of a table lamp, for example. To add some resiliency, I applied a layer of light-duty open-cell foam behind it, plus a layer of double-stick tape. These were cut to shape on the laser cutter. The resulting sandwich was pressed onto the servo side of the tilt mechanism (photo attached). The sandwich was a little too thick, though, even with the foam compressed, so I was not able to tighten the servo shaft screw all the way. But the extra friction helped immensely to smooth out the jitters.

-Phil

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Post Edited (Phil Pilgrim (PhiPi)) : 1/18/2010 4:06:40 AM GMT

mikediv

Phil I would interested if you could make it work with full size Parallax servos

Franklin

Phil, most of the pan/tilts I've seen use a u-bracket with support on both sides of the servo to reduce the side load. You could also apply the damping on that side.

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- Stephen