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vpt
01-10-2012, 08:25 PM
Buddy of mine wants me to put together a moving camera mount like the one in the video but to his specs (to fit his equipment).

http://www.digitaljuice.com/djtv/detail.aspx?sid=608

My first thought is linear bearings for the bed. Can they be ran on aluminum though? He wants it to be fairly light because obviously it has to be carried all over. What is your guys professional opinion for bearing choice and bed material? Has to be smooth and dust can't effect it much.

Dragons_fire
01-10-2012, 09:25 PM
I would just do it the way people make the cnc router ways. Use angle iron or aluminum and some sealed ball bearings. ill see if i can find a picture of what i mean.

Dragons_fire
01-10-2012, 09:36 PM
If you scroll to the bottom, there is a post by Tekinika that shows what i am refering too.

http://www.instructables.com/id/How-to-Make-a-Three-Axis-CNC-Machine-Cheaply-and-/

vpt
01-10-2012, 10:00 PM
That is good but the camera mount can't fall off if turned upside down.

Dragons_fire
01-10-2012, 10:35 PM
That is good but the camera mount can't fall off if turned upside down.

put two on facing each other, then it will be rock solid but slide nicely each way. The last post sort of explains it.

This is sort of the same concept, but wouldnt be as light.

http://www.brusselsprout.org/cnc/Y-bearings.jpg

And here is another website that has better pics and explanation of the bearings and angle aluminum setup. I would build it out of aluminum box, and it would be super light weight, and still retain a lot of rigidity.

http://woodworkerbcncrouterproject.blogspot.com/2010_03_01_archive.html

elf
01-10-2012, 11:25 PM
Here's a readymade solution: http://www.igus.com/wpck/default.aspx?pagename=filmtechnology I just picked up one of these for a different application. Cost for 1 meter rail + carriage was $115 + shipping.

If you're building completely from scratch, you need to deal with:

Noise from bearings. (If you want to record sound while shooting. The Igus bearings do generate some noise while moving.)
Smoothness of travel. (Horizontal) (stick/slip can ruin a good shot)
Levelness of rail. (A few thousandths dip in the center will be visible in the shot)
Rigid support. (Simplest is two tripods)

daryl bane
01-11-2012, 10:35 AM
I'm in the film business, but not directly associated with the camera support dept. So I went back and pulled out some sliders to see how they were constructed. The old tried and true JB slider looks to be a piece of aluminum with a couple of linear bearings bolted on. The other one has a much more complicated track arrangement, with u shaped rollers riding in a matching track. Both of these "professional" units are very expensive and NOISY. If it were me, I would think about utilizing skateboard wheels, and configuring the wheels to work in some available type track, and supported so the camera can be under-slung if needed. We have used skateboard wheels/bearings in other applications and they are quiet, smooth and CHEAP.

rowbare
01-11-2012, 11:46 AM
Pacific Bearing has a number of rail systems that might work http://www.pbclinear.com/Gliding-Surface-Technology--Plain-Bearing-Linear-Motion

BishopWisecarver http://www.bwc.com/ has a lot of bearing based components. Their UtiliTrack rails are nice.

bob

vpt
01-11-2012, 06:25 PM
I'm in the film business, but not directly associated with the camera support dept. So I went back and pulled out some sliders to see how they were constructed. The old tried and true JB slider looks to be a piece of aluminum with a couple of linear bearings bolted on. The other one has a much more complicated track arrangement, with u shaped rollers riding in a matching track. Both of these "professional" units are very expensive and NOISY. If it were me, I would think about utilizing skateboard wheels, and configuring the wheels to work in some available type track, and supported so the camera can be under-slung if needed. We have used skateboard wheels/bearings in other applications and they are quiet, smooth and CHEAP.



Thats good information! When noise was mentioned I was thinking what the bearings could be put in or coated with. The skate wheels are great!

Toolguy
01-11-2012, 06:59 PM
How about skate wheels inside an alum. channel on each side and cross members to hold the channels together? It would look like a ladder and be very light.

vpt
01-11-2012, 08:45 PM
Do skate wheels take kindly to being turned on a lathe? Or do they gum up and tear or whatnot? Could concave the center of them and only have to run 4 on two tube tracks.

kendall
01-11-2012, 08:55 PM
How long does he want it to be, and is it intended for positioning a still camera or for video with camera in motion?

I used to have a camera set up so I could film from behind a guard that was mounted on a 24" full extension ball bearing drawer glide, in that case I had a couple of adjustable stops to I could retract it for removing the card, then slide it back in place for filming.
Would be easy to attach a tripod mount, and threaded rod/nut to it for accurate wide range positioning. Could also be stacked for more reach if needed.

daryl bane
01-11-2012, 10:05 PM
Its been awhile since we fooled with them(skateboard wheels). You would probably have to do some experimentation. Like maybe use a sandpaper cartridge roll on a toolpost grinder type of thing. Or maybe putting them in the freezer? I don't know.

BadDog
01-12-2012, 01:23 PM
Its been awhile since we fooled with them(skateboard wheels). You would probably have to do some experimentation. Like maybe use a sandpaper cartridge roll on a toolpost grinder type of thing. Or maybe putting them in the freezer? I don't know.
Oddly enough, I turned one down just about 2 weeks ago for use in a gate guide repair. They are clear wheels with an internal rigid structure and came from some cheap in-line skates that were being thrown out. I needed it turned down to just above the skeleton and was afraid it would rip loose. However, it turned smoothly with sharp HSS and did not result in any problems at all.

macona
01-12-2012, 02:21 PM
You might look at using makerslide.

http://www.makerslide.com/

MaxHeadRoom
01-12-2012, 03:01 PM
For the wheels in a channel type I have used Rollon, nice stuff http://www.rollon.com/USA/rollon.htm
I have also used Pacific Bearing for Teflon lined slides.
Max.

Evan
01-12-2012, 04:13 PM
No way I would use rolling element bearings in this application. Too much noise and even the slightest contamination will produce rough motion. This is the perfect application for pure PTFE linear bearings. They have absolutely zero stick/slip, are self wiping and produce just a slight amount of sliding friction that makes it much easier to control the motion.

See this video I made to illustrate just how smooth they are. This small piece of PTFE is dropping under the very slight added weight on the polished shaft.

http://www.youtube.com/v/mOn6I7Yok2Q?version=3&hl=en_US

Oh yeah, no oil required.

macona
01-12-2012, 08:22 PM
The maker slide works very well with rolling elements:

http://www.buildlog.net/forum/viewtopic.php?f=30&t=820

http://www.youtube.com/v/xt77g-Zzdjs

There is also this one, it uses blue anodized 80/20 with one of their basic linear slides:

http://dynamicperception.com/index.php?main_page=product_info&cPath=16&products_id=26&zenid=270963207152226353106106c811d2e6

The speed controller for the rig is open source and is arduino based.

It was used to film this:

http://vimeo.com/29950141

vpt
01-14-2012, 09:39 AM
No way I would use rolling element bearings in this application. Too much noise and even the slightest contamination will produce rough motion. This is the perfect application for pure PTFE linear bearings. They have absolutely zero stick/slip, are self wiping and produce just a slight amount of sliding friction that makes it much easier to control the motion.

See this video I made to illustrate just how smooth they are. This small piece of PTFE is dropping under the very slight added weight on the polished shaft.

http://www.youtube.com/v/mOn6I7Yok2Q?version=3&hl=en_US

Oh yeah, no oil required.


What happens when dust and debris gets in there? Does look very smooth and nice in the video when all clean though!

Evan
01-14-2012, 04:43 PM
Dust and debris can't get in. It is a zero clearance fit. I use the same on my milling machine with no wipers or felts and the bearings are completely self wiping with no visible wear on the shafts even though I do some grinding.

Incidentally, the shaft it is on in the video is a hard anodized aluminum shaft which is why it appears so dark.

Your Old Dog
01-15-2012, 09:25 AM
I have seen angle iron turned on it's side with a bearing mounted on each wall. A pipe can then be pressed up against it for a very smooth roll. This setup was for a table saw panel glide. If I were building one that's what I'd use. When shooting TV news we used to just use a shopping cart and have someone push us. I find it hard to believe noise would be an issue unless something were dramatically wrong? I'll see if I can find my table saw plans that might give you something to work from.

edited to ad pic:
http://www.nextwavedv.com/wp-content/uploads/2011/03/CamDollyV2.jpg

vpt
01-26-2012, 05:30 PM
Having a bit of trouble turning the skate wheels. What kind of HSS grind gives the best finish on plastic/polyurethane/skate wheels?

The plastic turns nice but the finish has tiny little chunks of plastic either folded over, gummed up, or chunking out which gives the slide a tiny bit bumpy feeling. I don't think the "bumps" would even show up in a picture or effect the video while moving but I can tell its there and would like to get a nice smooth finish if possible.

I tried filing and sanding a bit but it didn't seem to help. I got a bit better finish using a flat edge HSS instead of a point.

I believe I remember reading that the tool should be a bit above center with plastic? Do I want a big negative rake or something more like the 45 degree sheer tool?

daryl bane
01-26-2012, 06:08 PM
It's been a while ago, and who knows what wheels were made of, but we fashioned a tool post grinder on the lathe with some sanding cartridges. Played around with speed of the lathe and the grinder to a get a smooth finish.

BadDog
01-27-2012, 02:13 AM
As I recall, I used a dead sharp 3/8 HSS bit with very positive rake provided by a 1/8" chip breaker and very small point radius with about 20* lead angle. Seems like I ran it pretty fast, with a slowish feed, but don't recall the number. This was on a cheap clear in-line skate wheel, and it made a very clean cut with a "nest" of thin ribbon.

Evan
01-27-2012, 03:06 AM
The plastic turns nice but the finish has tiny little chunks of plastic either folded over, gummed up, or chunking out which gives the slide a tiny bit bumpy feeling.

That is a common problem with milling polycarbonate. The solution is of course razor sharp edge and good rake with ample clearance. Also, though and very important is to not recut the same surface. You want shape and width of the cutting edge such that it doesn't overlap the area cut previously and the feed rate set to make that happen based on the width of the cut. Plastics build heat very quickly and it has nowhere to go because the plastic is a very good insulator.

So, if the cutting edge is .0625" wide you want the tool to advance the same amount per turn of the work. A tiny bit of overlap is OK to insure it doesn't leave a ridge. In a milling situation it means a very aggressive feed rate.

Black_Moons
01-27-2012, 03:48 AM
That is a common problem with milling polycarbonate. The solution is of course razor sharp edge and good rake with ample clearance. Also, though and very important is to not recut the same surface. You want shape and width of the cutting edge such that it doesn't overlap the area cut previously and the feed rate set to make that happen based on the width of the cut. Plastics build heat very quickly and it has nowhere to go because the plastic is a very good insulator.

So, if the cutting edge is .0625" wide you want the tool to advance the same amount per turn of the work. A tiny bit of overlap is OK to insure it doesn't leave a ridge. In a milling situation it means a very aggressive feed rate.

One of the gotchas in plastics is sometimes the SFM required to do such acts can be *lower* then steel.

This also makes it easyer to obtain the higher feed per tooth rates your talking about.

I mean, you think plastic, no problem with the tool dulling due to SFM/heat, No problem with the chips melting, But the higher the SFM, the more cuts per second results in more heat in the work and less time to disipate it. Also can slowly heat up the bulk of the cutter to high tempatures (Compairable to the melting point of plastic that is) and result in diffrent cutting action from when the cutter is at room temp

vpt
01-27-2012, 09:00 AM
The strings I have been getting off the skates act like rubber bands. I know because after each cut I have to use a pick to pull the rubber bands out of the V in the skate. I may have had to slow of feed, I will try some stuff out today.

vpt
02-07-2012, 09:33 PM
Ok I am having trouble holding the skate wheels (concentric?) with the bearings in the lathe while cutting.

Live center and strait bolts used for every test.
So far I have tried:

Bolt threw the bearing with a big washer on each side of the wheel and a nut tightening up the washers against the side of the wheel.

Tried bolt threw bearings and smaller washers that tighten up against the outer bearing race, chucked and tailstock like before.

Tried all 4 wheels on one shaft, tried both big and small washers. Chucked and tailstock like before.

Tried chucking the bolt threw the bearings in the jacobs on the tailstock then lightly pressed it up against the lathe chuck to turn the wheel on its bearings and taking light cuts. So the wheel was spinning on its own bearings which I would think should be concentric with itself?

I'm out of ideas, every time the wheels come out wobbly when spun on their bearings. I think after all these attempts I may have 1 wheel I could call strait.

The wheels themselves don't seam to spin strait so when I clamp them up strait like with the washers when they relax they are wobbly.

Pics

http://img833.imageshack.us/img833/3302/cameraslide001.jpg

http://img59.imageshack.us/img59/1620/cameraslide003.jpg

And since it was there I tested my camera on it. You can see how wobbly it is. It is fairly loud yet, I still have to add a tripod mount in the middle which should help a bit and feet and get it off the metal table.

http://www.youtube.com/watch?v=CMI6ggGTQtg

Maybe I should just make the wheels from scratch out of delrin?

BadDog
02-08-2012, 06:29 PM
I did it with in-line wheels, so not quite the same. But I just popped out the bearings and made an arbor to mount with light hand "press" into the bearing recess with bolt and fitted "washer" on the outside. After finishing I tried it mounted on it's own bearings, just spinning and sighting across. If it could have been any more dead concentric, I couldn't see it, which made it easily good enough for my use. If I think of it (doubtful actually), or someone expresses interest, I'll put an indicator on it to quantify any error this weekend.

Evan
02-08-2012, 10:48 PM
Time to try some teflon slides. :)

darryl
02-08-2012, 11:53 PM
Yup. Teflon slides. And spray those rods with Bostik top cote.

Video Man
02-09-2012, 12:00 AM
Home-made video and film production equipment is a pretty popular topic with a lot of independent producers...when I was working for a video website we found a ton of "how I made my slider/mike boom/jib crane/u-name-it" articles on YouTube. Some were quite well thought out, maybe some inspiration to be found there....:)

PS: a lot of DIY rigs at this site: http://www.softweigh.com/video/diy.html

vpt
02-09-2012, 08:35 AM
Thanks much for the link video man, some neat stuff there!


After starring at the skate wheels for awhile yesterday I pulled the bearings out of them and started turning up some delrin wheels. Much better material to work with than the skate wheels! I already have the bearings in the new wheels and just started making the V groove in them yesterday. I can already tell they are coming out strait and should work much much better! The material turns real nice on the lathe, no gumming up, no deformation, so far so good!

Now the noise isn't a huge concern because almost all of the guys films have music or something in them but I do want to make it as quiet as possible. In the video I posted I mentioned that it is louder than it will be because of some factors there. But I am thinking of also filling the tubes with something like great stuff to dampen the sound as much as possible. I also think the new smoother delrin wheels will also be quieter.

vpt
02-11-2012, 08:39 AM
Finally no wobbly.

http://www.youtube.com/watch?v=yD7gwYD4xB8&feature=youtu.be