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Building my own tracks


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#1 Ira Ratner

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Posted 26 July 2008 - 03:18 PM

I'm just a hobbyist, but it has been driving me nuts looking at the prices they're asking for simple straight and curved dolly tracks. I'm going to need a basic 360-degree circle to start, 8-feet diameter, but damn if I can afford hundreds and hundreds of dollars for this just to use in my backyard with a K-3.

And even REAL filmmakers like you guys--students and independents and budget conscious--don't want t0 spend more on this kind of stuff than necessary anyway.

I work a a graphic artist in the engineering department for the Florida Department of Transportation (Florida's Turnpike SunPass/toll collection division), and I spoke to an engineer about the objective. Of course, I got advice that was way over-engineered for what I needed--and a pain in the ass to use. But I gleaned some ideas that I'm going to use for my plan, and that maybe would work for you too.

EMT stands for electrical maleable tubing--REAL inexpensive and light pipe that you can buy anywhere and that bends real easily. (They run wires through it and it comes in various diameters.)

So...

I'm going to get a pipe bender, do the math, and bend pieces to give me that 8' diameter circle. The circle will ultimate consist of multiple pieces about 2-feet long, filled with sand (for weight and stability)--and about 1/2" in from each end of each piece, on the inside, will be epoxied/capped/whatever, to hold the sand in.

And the pieces will connect to each other with simple dowels.

Am I brilliant or what?

Edited by Ira Ratner, 26 July 2008 - 03:22 PM.

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#2 Warwick Hempleman

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Posted 28 July 2008 - 12:09 PM

Do the math. What's your time worth per hour? What's the cost of the tools and parts?

Now, go to the Yellow Pages and call an equipment rental house and ask what it costs to rent an 8' circle (usually 8 pieces of track). Be sure to ask for some material to level the circle you rent. You'll want wedges, boxes, lumber nd a few other things that your rental house will recommend. You might want to add that material to the parts and labor estimate above while you do the math.
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#3 Warwick Hempleman

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Posted 28 July 2008 - 12:10 PM

Do the math. What's your time worth per hour? What's the cost of the tools and parts?

Now, go to the Yellow Pages and call an equipment rental house and ask what it costs to rent an 8' circle (usually 8 pieces of track) for a day or a week. Be sure to ask for some material to level the circle you rent. You'll want wedges, boxes, lumber nd a few other things that your rental house will recommend. You might want to add that material to the parts and labor estimate above while you do the math.
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#4 JD Hartman

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Posted 28 July 2008 - 12:52 PM

Yes, you can bend EMT (electrical metalic tubing) with an Electrician's bender, but it wont make the smooth continuous radius bend you need for circular track. What you should is go to a manufacturer of hoop style greenhouses. The will have the tubing, equipment and experience to roll the radius into the tube without kinking it. Or just rent the track as has been suggested.
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#5 Paul Bruening

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Posted 28 July 2008 - 01:27 PM

JD's right. I've got a big bender for other things and I can say it won't do what you want. The other thing is EMT. It's too soft and will warp in use so bad that you'll end up throwing it away.

If solidity and dolly weight isn't a big point for you (DV producers often only need just a tripod, small cam and skate dolly), the PVC systems seem to be doing a good job and can flex to your individual situations.

If you need something that can handle an old school dolly loaded with a few hundred pounds of camera and a few big fellas rolling along like a freight train, then you'll want to go with tube stock. You can use steel tubing in round or square but it needs frequent paint retouching or constant oiling depending on the surface. Chrome Moly tube is better as it's a low corrosion alloy. Stainless steel tube is best but costs like a *****. You'll need a grinder, mig welder and circular saw with lotsa' cut-off wheels. You can't make your circular bends without some serious table benders so that will have to be done at an industrial shop. There's a conveyor manufacturer down the street from me. They are exactly the kind of operation that bends tube to precise shape. You have to ask around at metal and welding shops since the big table benders can be under any name.

So.... here's the point: the people who build their own heavy track are usually into that kind of fabrication already. By the time you get the gear together and learn metal working enough to do the project, you coulda' just broke down, winced, and overpaid for the track. I'm not telling you, "don't do it". I love my welding gear and have used the hell out of it. I'm just saying.
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#6 Saul Rodgar

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Posted 28 July 2008 - 01:37 PM

What a lot of us don't realize is that there is a reason why the pros use certain equipment, tools and techniques: they are proven to work like they should, every time. It maybe tempting to try to reinvent the wheel, but more often than not it becomes a lot more expensive in the long run. There is a lot of money being put into researching and engineering the tools of the trade that work every single time. But of course, they can always be improved. Still, is harder when you are starting from scratch.

Not that I am suggesting you stop tinkering, you may find something the pros didn't think about. Just be realistic in your expectations . . .

Edited by Saul Rodgar, 28 July 2008 - 01:41 PM.

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#7 Warwick Hempleman

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Posted 28 July 2008 - 03:27 PM

Sorry about the double dip earlier, serves me right for posting on an empty stomach :)

Ira, before you even start doing the math, contact those selfsame rental houses or manufacturers. Dollies have standard wheelbases, tracks have standard radii, and wheels and tubes have complementary diameters. All the other gentlemen's comments and suggestions are of course worth keeping in mind, too.

Speaking from the rental end of things, curves are a sort of "Loss Leader". you have to have them as a rental house, and they rarely pay for themselves.

There have been a few lightweight plastic extrusion track systems over the years, this may be what you're looking for.
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#8 Ira Ratner

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Posted 28 July 2008 - 06:14 PM

THANKS FOR THE REPLIES, GUYS!!!

As far as renting, not even an option:

Did you forget that I'm just a putz hobbyist playing around at home? And an OLD putz at that?

And yep--I was originally going to go the PVC route, because I learned online how to bend the stuff with a heat gun--filling the PVC with sand so it would absorb the heat and minimize/eliminate kinks. However, I was guided away from that idea by that "important" engineer at work who I told you about, and who pointed me to EMT instead. So both options are still on the table.

Yougotta realize that all I'm doing is setting up a dolly on a track to hold a tripod for a K-3. Not a lot of weight, but YES I realize that ANY kinks in the track which the wheels encounter will disturb the shot horribly. But I'm going to experiment anyway, and It need some help with the math. (Remember the old putz point here--because it's is an important one. Also throw in cheap and poor.)

Let's say I decide on a 10' diameter circle.The formula for circumference is P times R-Squared, correct? Which means 3.14 times 25' (radius of 5 squared). This means I'll need about a million feet of pipe. or around 80', which I can tell you exactly when I have a calculator in front of me.

So...

How the heck do I figure out the ARCH of the pieces--which should be the same whether I make this 10' diameter circle out of 8 separate pieces or 16 pieces? I would cut the pieces first, then build a jig to bend them.

Come on--you guys gotta encourage me. You're gonna laugh your asses off when I post pics.

Or maybe NOT!

But probably.

Edited by Ira Ratner, 28 July 2008 - 06:14 PM.

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#9 JD Hartman

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Posted 31 July 2008 - 02:51 PM

I believe that the formula you stated is for area. Circumference is Pi times D. For a 10' radius, it would require 31' of pipe or tube. The outer track would be a 12'1" radius, using the standard 24.5" (probably 24.75 on curves) dolly wheelspacing, you'll need approximately 37'. You can try and bend these yourself or find a hoop house manufacturer in Florida. They'll have the pipe, the machine, the skills and save you a lot of money.
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#10 Ira Ratner

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Posted 01 August 2008 - 06:04 PM

I believe that the formula you stated is for area. Circumference is Pi times D. For a 10' radius, it would require 31' of pipe or tube. The outer track would be a 12'1" radius, using the standard 24.5" (probably 24.75 on curves) dolly wheelspacing, you'll need approximately 37'. You can try and bend these yourself or find a hoop house manufacturer in Florida. They'll have the pipe, the machine, the skills and save you a lot of money.


Thanks, JD, And of course, you're totally correct:

My lousy math was pointed out to me yesterday.(In 1972, while all of the other kids in my high school geometry class actually went to class and studied, I SKIPPED class and smoked weed.)

I still might go the PVC route with this--it doesn't have to be a PERFECT circle, just perfect enough. And before I do the circle, I'll probably build the dolly and sand-fill and cap about 16 feet of straight track just to test the wheels. I already pulled a dolly design off the web that doesn't look all that difficult.

What would a decent and practical pipe/tube diameter be though? An inch? They didn't specify.
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#11 James Steven Beverly

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Posted 01 August 2008 - 07:35 PM

If you have a race car fabrication shop in town or in the area, they have tubing benders that are damn accurate and can fabricate the stuff outta seamless tubing (the same stuff the build roll cages and frames outta, Hell, if you got the cash, you could even go with chromoly tubing). It's doable but will cost you something per bend most likely plus stock. the problem with a pipe bender is it's hard to get a smooth continuous curve over a 4 foot section and the way the work usually screws up the diameter of the tube. You could also weld up a bending jig, fill the tubing with sand, clamp it at one end and use an acetylene torch with a rosebud tip to evenly heat the pipe and slowly curve the tubing around the jig without collapsing or distorting it. I'd use 6 ft pieces to create 4 ft sections.
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#12 Warwick Hempleman

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Posted 02 August 2008 - 04:21 PM

The standard OD for track in the US is 1 1/2". If you build a dolly, get wheels compatible to this. There are a few track manufacturers making things as small as 1 1/4", and there are a few oddball sizes as well, but a wheel for 1 1/2" tube will roll on any of the smaller sizes.

The standard track width (center to center) is 24 1/2", like JD mentioned. This is almost 62 cm, which has led to a few interesting issues fitting US-made and European-made stuff together. But I digress.

Incidentally, while this may be obvious, remember that you actually have two circles (inside rail and outside rail) and hence two radii to consider. This also results in the two pieces being of different lengths in order to make one segment.

Another thing you may not yet have thought about is joining the two rails to one another using crossties. Put simply, you'll need to this if you want to track on anything other than a brand new warehouse floor.

So what's it cost to rent a circle for a week from your local equipment house? I'm guessing under $80 and if you ask nice they might even throw in a box of wedges.

Edited by Warwick Hempleman, 02 August 2008 - 04:22 PM.

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#13 Ira Ratner

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Posted 03 August 2008 - 09:49 AM

For a 1" straight solution, this looks like an okay deal with the dolly:

http://cgi.ebay.com/...1742.m153.l1262
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#14 Bob Hayes

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Posted 04 August 2008 - 11:27 AM

Another thing to consider is that circular track is very tricky to level. Both rails need to be connected to each other and you will need wedges to achieve a stable level base.
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#15 Ira Ratner

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Posted 05 August 2008 - 05:35 PM

Another thing to consider is that circular track is very tricky to level. Both rails need to be connected to each other and you will need wedges to achieve a stable level base.


Why is this different than straight track? Because unlevel circular would be more obvious? Or because straight is simply by its nature easier to level?
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#16 Darryl Richard Humber

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Posted 06 August 2008 - 01:30 AM

Why is this different than straight track? Because unlevel circular would be more obvious? Or because straight is simply by its nature easier to level?


Straight track is intuitively easier to level because you are levelling between two points. Circular track also tends to "walk" more as you travel around it. Often, as the weight is on one side, the opposite side will rise up and float somewhat until you come back around to it, depending on how level your surface is. You mentioned that you were making it in 2' sections (unless I misunderstood). I think this is asking for trouble and will cost you much more time and headaches. The more joints you have, the more opportunity for bumps and the harder it will be to level individual sections.
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#17 Warwick Hempleman

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Posted 06 August 2008 - 06:44 AM

As you can see there's a lot more to making curved track for moving a camera than one would think at first. Depending on your point of view it's part of why grips a)don't get near enough money for the knowledge we wake up with every day or B) get far too much money for the knowledge we wake up with every day.

I see Coral Gables is near Miami. Track rental costs (according to an online Miami price list) about $10/day and $40/week for an 8' section or for 1/8 of a standard radius circle. A doorway dolly is about $80 / day. Granted, you'll need a vehicle to move it, but you'll need that sooner or later anyway. Do yourself a favor, call a rental house and see what they have. Ask to come up and let them show you what's involved, for a basic overview of what we're describing with leveling track. The guys there will be friendly and have some time for you if they're not in the middle of turning around ten jobs at once. If the first place you try isn't friendly, try another one.
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#18 Bob Woodhead

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Posted 06 August 2008 - 07:28 AM

I've done the PVC route, built a dolly using purchased wheel kits. Decided not to go totally from scratch, as I'd read many posts as to the best wheel formulation (soft/hard) so wanted someone ele's experimentation results, and didn't have the tools to machine the bearings, swivels, etc. Platform's same size as standard doorway dolly, with spring-loaded tie-downs, removeable pushbar, and built up from 3 layers of 3/4 ply. (very rigid that way)

Track... using 1" pvc, as the wheels run fine on it (though they'll also run on standard metal track also), and the 1" takes up less room than the 1.5" in the carry bag (an old ski bag). Got a bunch of 10' pipe cut to 5' to fit ski bag. I use a very fine-toothed miter saw to cut the PVC, as the ends need to be as straight & smooth of a cut as possible for best joint. There are a few ways to keep the track joined, but the only way I've found that works are the track connectors seen at glideshot.com - but I made those myself for a fraction of the cost. Curved track? I'd rent it. lol. Though if a 10' bit of curve is enough, it's easy to bend the PVC on the spot & tack it down with a screw or nail to scrap wood.

So far I've had 2 people, sticks, HPX500, and a few acc's on it, and it runs fine. Just 1 person & cam isn't enough weight for a silky glide, so I throw a bunch of sandbags on to help.

Works really, really well on any fairly level floor. Very smooth. Very fast to set up. Easy to transport. The dolly platform, upside down on a transport cart (Magliner, RocknRoller) makes a great larger area to carry stuff. Track weighs nothing. Used on rough surface, like a street, you need to lay down felt to keep the PVC from "skittering" around. Not as easy to shim as metal track, esp. on uneven terrain (hillside).

For uneven terrain, though, I reach for my Steadicam FlyerLE. :lol:

Edited by Bob Woodhead, 06 August 2008 - 07:31 AM.

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#19 Bob Woodhead

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Posted 06 August 2008 - 07:40 AM

It won't let me edit my post.... hmmmm....

Anyway, for 1 section of curve, it's easy to bend a 10' section using rope or whatnot for a temporary arc. That's another nice thing about PVC track.... if you need another 30' of track, just find your local hardware store.
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#20 Ira Ratner

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Posted 06 August 2008 - 07:08 PM

Thank you, Bob. The adventure begins soon.

And yeah--the edit post restrictions here drive me nuts!

Edited by Ira Ratner, 06 August 2008 - 07:08 PM.

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