[sigipa]

Hello All,

I need to build a pan / tilt unit for a security camera project I'm working on. I originally had a mechanical engineer that was supposed to take care of the mechanical stuff, but he flaked out on me and left me holding the bag. I am new to this kind of thing and I could sure use some good advice on a few issues. If some kind hearted soul has a moment to spare, I would be very grateful.

Info:

Pan / Tilt Unit
Enclosure weight: 200lbs
Enclosure dimensions: 14" square
Enclosure base dimensions: 14" x 14" x 4"
Azimuth shaft size: 1.5" dia.
Azimuth shaft material: Stainless T-316

Camera Unit
Enclosure weight: 85lbs
Enclosure dimensions: 8" x 8" x 22"
Elevation shaft size: 1.5" dia
Elevation shaft material: Stainless T-316

1. Stepper motors

I have spent several weeks trying to get up to speed on stepper motors for the purpose of selecting the right motor for the job. I was initially very happy to find that a lot of the stepper companies have an application support group that are there to help customers select the right product. However, after many phone conversations, I have received many conflicting recommendations. I have tried to understand the issues and come up with my own spec. Could someone let me know if I have selected the right motor?

NEMA34
Holding torque: 1702 in oz
Gearbox ratio: 2:1

I was planning to use the same motor for both the pan and tilt.



2. Bearings

I'm also having some problems selecting the right bearings for the unit. I figure that I need one radial and one thrust bearing for azimuth rotation and two radial bearings for elevation adjustment. There are a lot of different types of bearings in those categories and I could sure use some good advice on the best choice for my application

I have not managed to come up with anything on this yet.

3. Formed vs. milled

This is probably a dumb question, but I haven't been able to find the answer. What are the strength properties of a milled bracket versus a bracket bent on a brake, if they are made of the same material?



Any and all opinions will be much appreciated.

Thanks,
-S

[harryn]

You have a lot of design challenges to overcome, and really need an integrated approach, IMHO. If I were in this situation, I would do one of the following

- Post in the cnczone section for RFQ / jobs http://www.cnczone.com/forums/forumdisplay.php?f=74

- Post in craigslist or similar jobs / gigs wanted kind of forum.

A project this large needs a real designer / engineer for the project. There are a lot of good, under employed people out there, you should have no problem finding some. Depending on your area, 5 - 20% of the US is unemployed, so getting a consultant should be no problem.

Just a general question though - Do you have an idea on how to use one motor to pan and tilt ? I assume some kind of gearbox ?

[sigipa]

Hi,

I've made a fair bit of progress on this since my post. When I said "use the same motor", I meant a second identical motor not just a single motor. Anyway, I have managed to figure out most of it. I am currently looking into shafts and the various factors that need to be considered for material selection and fabrication. Someone on one of the other forums pointed me to the "Machinery's Handbook". Wow.. what a resource. I wish I would have known about it sooner. It would have saved me a lot of time.

I appreciate your suggestion. If the budget allowed, I would definitely have chosen the consultant route. However, it's now become a personal challenge. I feel pretty good about the design at this point. Now I've got to get my head around CNC fabrication ;-)

BTW: If you leave out the pressure to get it done, I'm actually starting to enjoy the project a little bit!

Thanks for your advice,
-S

[mxtras]

If at work, there is always pressure.

If there is no pressure, it's called a hobby.

Scott

[jrrdw]

Click here for bearings, as for the rest, i've found it's best to dry fit as you go, that way if your going to run into building problems, you can catch them as they come. As for the step motors, your camra will need to be balanced for smooth operation, you probly knew this allready, i hope it helps. Thats a heavy duty box your building, will it be subject to abuse?

[sigipa]

Hi,

jrrdw: Yes. One of the requirements is that it needs to be bullet proof to UL 752 level 8. The bullet resistant material adds a fair bit of weight (approx. 40lbs.).

Thanks for the advice,
-S

[jrrdw]

Kevlar or Dragon Skin? All bearings i've gotten (all 4 of them), have been nice and on time. I'de like to see the pivet your building, think you can post or send a picture or two?

[billblack]

Since I've never contemplated what it takes to "bulletproof" anything other than a bullet trap for target shooting, I had to look up the standards mentioned. If anyone else is interested take a look at http://http://www.closefocusresearch...s_summary.html which gives the various international and domestic standards.
Then these fine folks http://http://www.armortex.com/products.html are kind enough to explain what it takes to meet said specs.
Interesting project.
Good luck.

[fatal-exception]

What are you planning on using for remote connection/control of the pan and tilt unit? Will you have a PC near the camera?

Milled bracket vs bent bracket? There would not be much difference in strength as long as the bent one was stress relieved after bending (and possibly heat treated properly). You could obviously make a fancier bracket if it was milled from a billet of material, but the cost would be much higher.

P

[ssbowtie1]

Any updates/pictures on your setup? Have you considered using a lazy susan bearing and a simple friction drive for the azimuth control? I'm working on a similar project.