Need RPi case from Laser

[jta...@gmail.com]

Next time it is convenient for anybody to cut a Raspberry Pi 3 B case on the Laser, please do.  I need to present my awesome new RPi at a club meeting and I would like to advertise the ATX Hackerspace logo on the side if that is possible.  My bid for this work is 500 cents.  Thanks!

[Robert Ristroph]

I'm teaching a class on the red laser at 8:30 pm tomorrow, why don't
you take it and we'll cut your case as the class example ?

--Rob

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[jta...@gmail.com]

Can't make it tomorrow, but please do cut the case!  In any case (pun intended), please consider a class on some weekend.

Joe T.

[Robert Ristroph]

The class is also offered at 1pm on Saturdays.

Do you have a link to the case you want ? I usually cut this one or a
modification of it: https://www.thingiverse.com/thing:679809

[Joe Talafous]

1pm it is!  This weekend because Aug 21 I am chasing an eclipse.

Wow, that case is a thing of beauty.  I love the clear-ness.  Where do I get that beautiful material?  I can settle for opaque, but the lexan, acrylic, or whatever that clear stuff is... is striking!

Rob, I need to burn another 16 Gb microSD, mine died (my fault).  Could you bring in that microSDreader you had in case the one in the 3d printer computer walked away?

See you and all students at 1pm Sat!

Joe T.

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[Joe Talafous]

I did notice that the RPi case you linked to was not mine by name but it looks like mine visually... maybe typo!  Just in case, mine is Pi 3 Model B.

Thingiverse looks amazing.  I am also looking to make a gear box for pointing (something like) satellite dishes toward the sky with azimuth and altitude wormgears.  I have NO NO NO mechanical engineering experience, but some expert there said a stepper motor is a way to go, especially if it increases torque and also the resolution of the steps.  Just putting this message in a bottle in case some mechanical engineer knows gear boxes.  

[James Hughes]

Joe, I've built several things like that before. Not for anything as big as a satellite dish, but the general principles apply.

[Joe Talafous]

Thank you, I definitely would like to pick your brain.  I just disassembled a rotating fan to see how it does it... short answer is that their design is a rotating reciprocating one, sort of like a steam engine https://en.wikipedia.org/wiki/Reciprocating_motion

The dish will be small (say 25 lbs) but it would track a LEO satellite as it moves across the sky.

I am thinking of having a vertical shaft that rotates azimuthally.  On the top of this there would be a horizontal shaft to adjust the altitude.  It would form a T-shape. 

Do you recommend using a worm gear on a stepper motor?  What I am thinking for the azimuthal axis is a vertical shaft with a pretty big transverse gear that would be driven by a worm gear on a stepper. 

All these shafts would need bearings.  What would be the type of bearing I would need?

I am in the process of finding a used stepper motor and learning how to get the Arduino to control it. 

[James Hughes]

One of the machines I made is a pointing machine meant to track celestial bodies. The installation is a pair, with one machine always pointing at the sun, and the other always pointing at the moon. It has a construction similar to what you'e describing. It uses stepper motors and 96:1 worm gears.

You just need to figure out how much your dish weighs and find bearings which can support that with some wiggle room (preferably a lot of wiggle room e.g. 3:1).

We probably don't need to clutter up the mailing list with talk about this. Email directly.

[Riley Cassel]

Actually it's kinda nice to see constructive things on the list ;-)
If you guys go off list loop me in pls.


For pointing a 25lb dish I'd build a Dobsonian mount.

3 lazy susan bearings, some plywood, two stepper motors with pulley,
20' of mt2 belt, arduino with grbl shield & 2 stepsticks.

*fwiw, I've built a few of these for telescopes & such. for really
heavy stuff (radio telescope, solar tracker) automotive spindles are
cheap and plentiful


http://www.homedepot.com/p/Shepherd-6-in-Metal-Lazy-Susan-Turntable-with-500-lb-Load-Rating-9548/100180572

http://openbuildspartstore.com/gt2-2m-timing-pulley-30-tooth/

http://openbuildspartstore.com/gt2-2m-timing-belt/

http://openbuildspartstore.com/nema-17-stepper-motor/

http://www.ebay.com/itm/Arduino-GRBL-CNC-Shield-Kit-3-4-Axis-Controller-for-NEMA17-3D-Printer-Mill-/182228684875


http://www.instructables.com/id/BUILDING-a-DOBSONIAN-TELESCOPE-MOUNT/

https://stellafane.org/tm/dob/



-
Riley

[Albatross Hotel]

I'm with Riley on this. I'd use an automotive spindle/hub-bearing assembly. They're pretty cheap, accurate and very durable.

[Lloyd Ewing]

Joe,
Is this hardware intended to be exposed to the weather for an extended period of time?  You might want to consider the azimuth/elevation rotors that are sold commercially for ham radio for this purpose. They are likely to be less expensive, although not as interesting as designing one yourself.

[jta...@gmail.com]

Wow!  Thanks everybody for all the great ideas!  I'll check out all the links and come back with more specific questions.