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Speed Rail for Dolly Track


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#1 Steve London

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Posted 19 October 2010 - 11:19 AM

I'm a small scale gaffer and I often supply grip equipment as well so I've decided to make the best doorway dolly I can since it's a common request from my DPs. The dolly will at least permit the cinematographer to ride and perhaps the focus puller.

I'm not lowballing this project to ghetto levels -- I'm spending just under $1000 -- but I can't afford commercial stainless steel rail, so after doing my research and thinking hard I've decided to use 1 1/4" 6061 T6 aluminum pipe speed rail. It's strong and stiff and miles better than PVC pipe, which I never really seriously considered because it must always have full contact with the floor or whatever to support it, while speed rail has enough strength to bridge gaps of two or three feet. I'm making wooden ties with molded rubber pads on the end to keep the track positioned at the right separation and so I can use wedges and cribbing to level it on uneven terrain. I have the joints worked out so they are solid.

Do any of you folks ever encounter speed rail track something like this and if so, what can you tell me that might be useful in doing the best job possible? Pics would be really great. TNX.
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#2 Phil Rhodes

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Posted 19 October 2010 - 12:35 PM

Aha, an excuse to brag about my dolly!

Posted Image


The track we built has 1-1/2" tube with 1/4" thick walls sitting on 3/4" square U-section, which means it's a bit heavy but extremely tough and rigid. We built the wheel units with the idea that it would, if necessary, be capable of running on scaffold tube (speedrail being the alloy version of the same thing). If you were intending to run solely on speedrail you would likely prefer to space the wheels out a little more, as you won't end up sitting so much on the crown of the tube which obviously affects stability and your ability to take corners. Fixing this would be a simple matter of using slightly bigger angle to mount the wheels, or you could use longer bolts for each wheel and add spacers (an extra nut, probably) to provide variable wheel spacing that you can swap out in under an hour.

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#3 Stephen Murphy

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Posted 19 October 2010 - 02:26 PM

Aha, an excuse to brag about my dolly!

Posted Image


The track we built has 1-1/2" tube with 1/4" thick walls sitting on 3/4" square U-section, which means it's a bit heavy but extremely tough and rigid. We built the wheel units with the idea that it would, if necessary, be capable of running on scaffold tube (speedrail being the alloy version of the same thing).

Phil



great job Phil!
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#4 Sanjay Sami

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Posted 19 October 2010 - 03:28 PM

Aha, an excuse to brag about my dolly

Phil


That looks like a really well made setup.
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#5 Steve London

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Posted 20 October 2010 - 10:46 AM

Aha, an excuse to brag about my dolly!

Posted Image


The track we built has 1-1/2" tube with 1/4" thick walls sitting on 3/4" square U-section, which means it's a bit heavy but extremely tough and rigid. We built the wheel units with the idea that it would, if necessary, be capable of running on scaffold tube (speedrail being the alloy version of the same thing). If you were intending to run solely on speedrail you would likely prefer to space the wheels out a little more, as you won't end up sitting so much on the crown of the tube which obviously affects stability and your ability to take corners. Fixing this would be a simple matter of using slightly bigger angle to mount the wheels, or you could use longer bolts for each wheel and add spacers (an extra nut, probably) to provide variable wheel spacing that you can swap out in under an hour.

Phil


Oh beauty, that's really fine Phil. Thanks for giving me a look at it. You've done something far more sophisticated than my project but given me a lot of good ideas. If you can post any more photos of the details such as the bottom, that would be really nice. I'm a shameless thief of other people's good ideas :)

On the speed rail size, the 1 1/4" I'm calling mine is because that's how the pipe sellers designate it and the manufacturer has labeled it (I've also seen this tube marked 5/4") but the actual measurements are 1 5/8" O.D. ~3/16" wall. Nothing about this tube, including it's I.D. is 1 1/4". As far as I can tell the 6061 aluminum alloy T6 temper is the strongest material available to me and is often called aircraft grade. As this is a standard stateside is it by chance what you have used? There is indeed a larger standard speed-rail tube usually specced as 1 1/2" but bigger in any dimension, of course but it looks bigger to me.

Did you manufacture your own trucks? Are they skateboard wheels? They appear to rotate, yes? Do they slide inward and outward to accommodate curves? I bought the best I could find at reasonable price. They are these and they are rated for at least 250 lbs each, about $250 the set of four, but at half the number of wheels as yours they are obviously less robust:

Posted Image


Your track looks great. Reminds me of lumabeam a little bit. I hadn't thought of using the U-channel. How is it attached to the tube? Will the track scissor closed? Are the cross pieces, the ties, attached and if so how? I'm planning not to attach my ties but I was also making them out of hardwood or bulky 2X4 lumber.Al U-channel would be far more compact and lighter. Have to get back to the metals place and check that out.

What is the deck made of and how is it attached? Is it reinforced underneath? I'm using spendy 1" Baltic Birch 18 layer plywood and if I have to for rigidity I'll run two sturdy aluminum L-channel to stiffen it.

Which reminds me, what are the finished dimensions of your dolly and the track lengths? From memory my deck is 44" X 28 1/2" with standard 24 1/2" truck spacing on centers to fit standard track for those rare ocassions when someone will have some. Mine will fit through a standard interior doorway here.

What are your track lengths and how do you couple them? The speed rail stock comes in 20' lengths and I had mine cut into two 8' and one 4' lengths, which I think will work okay in the typical interior.

I'm joining the lengths with some Modern Studio Equipment couplers and the pads for the rails are also from modern and appear to be molded silicone rubber. I couldn't find these in their online catalog which is a pity because they are simple and really effective. An old-timer tipped me off to them. I'll take some snaps and post them if anyone is intersted.

Thanks for any questions you can answer. Oh, and I'm jealous Phil :)

Any other comments welcome.

Edited by Steve London, 20 October 2010 - 10:48 AM.

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#6 Phil Rhodes

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Posted 20 October 2010 - 07:31 PM

Ah, there's nothing quite like the opportunity to discuss one's pet projects...

On the speed rail size, the 1 1/4" I'm calling mine is because that's how the pipe sellers designate it and the manufacturer has labeled it (I've also seen this tube marked 5/4") but the actual measurements are 1 5/8" O.D. ~3/16" wall. Nothing about this tube, including it's I.D. is 1 1/4". As far as I can tell the 6061 aluminum alloy T6 temper is the strongest material available to me and is often called aircraft grade. As this is a standard stateside is it by chance what you have used?


We got all the materials from a general metal stockist, so the sizes were as stated without any of the usual "pipe dimensions" complexities because it isn't specifically pipe, it's just normal, off the shelf extruded aluminium stock. I'm in the UK, so it would have been more normal for things to be in metric measurements, but I got inch-gauge stock for most of it because I wanted it to be standard dolly track once we were done.

You might want to be a bit careful with the type of alloy you use. I seem to recall it is 6061 but I could be wrong, it's that or a close cousin. I have quotes for doing the bending for curved sections but the rails will not be made out of the same material. High silicon alloys have a greater tendency to crack when worked. If you want consistent materials, research this up front.

Did you manufacture your own trucks? Are they skateboard wheels? They appear to rotate, yes?


Yes, yes, and yes. Wheels, bearings (two per) and spacers are easily obtainable. The trucks are each based around a machined block drilled to accept two pairs of wheels (which also hold on the angle that supports the other two pairs), because I couldn't find right triangular extrusion. They're supported on M12 (say, 3/8") threads which are supported by the two large box sections via a set of thrust races.

Do they slide inward and outward to accommodate curves?


No. Didn't think of that. D'oh. Good idea. You can remove the outer two pairs of wheels on each truck to allow for the negotiation of tighter bends, though. The wheel count was chosen to maximize loadbearing capacity and mitigate any roughness at joints; I think it works.

I hadn't thought of using the U-channel. How is it attached to the tube? Will the track scissor closed? Are the cross pieces, the ties, attached and if so how


Tapped and bolted through the thick wall of the round rail top with M8 (about 5/16") socket cap bolts; every nth bolt holds a tie (sleeper, in British English) on. The ties are drilled to clear the socket caps on the bottom, so the fasteners are hidden inside the 2x1" extrusion, which is why we used socket caps in the first place. There are nylon washers so it can scissor without shredding the metal surface. We had to build a jig to drill and tap the rail tops accurately enough, but it was doable with hand tools.


Resist the (understandable) urge to have it welded. Differential heat stress risks each section of your track forming a small, well, hill...

What is the deck made of and how is it attached? Is it reinforced underneath?


A chunk of about 1" thick MDF I had lying around from another project. It has angle brackets (hard to describe, I'll find a photo) made of the same stuff we used to make the trucks, so it just drops in between the two box sections and sits there. We saturated it with floor paint, but I suspect that if it gets wet under the paint, and this is the UK remember, it'll go the way of all particle board and explode into a huge soggy mess. Your ply won't have that problem. No reinforcement required, and the ply should be tougher still.

Which reminds me, what are the finished dimensions of your dolly and the track lengths?


Ehh, I dunno, dolly-sized. People have said the track is more like crane track, which apparently tends to be 1-1/2" OD as opposed to 1-1/4". The rails are on 24-1/2" centres. The dolly was built to go through a doorway; it's barely wider than the track (maybe an inch each side). If you forget and swap over the two box sections with their frame clamps, you end up with the clamps protruding a bit further, but you at least get the choice of either clobbering a door frame or barking your ankles on them if they aim inwards...

What are your track lengths and how do you couple them?


Long sections are 2500mm and short ones half that plus or minus the 1/8" width of the diamond cutter blade; that's the metric length the stock came in, and it seemed daft to cut it down four inches just to satisfy tradition. Pegs at the joints are 1" round bar, fastened with bolts that are obscured inside the U-section under the track. The couplers are just off the shelf turnbuckles.

Accessory kit includes enough wedges for one at each end of each tie, wooden mallet, spirit level, furniture polish and polishing cloth, tools to suit the frame clamps, laser pointer and clamp, spare clamps to mount compatible accessories, gloves, etc. It breaks down into parts that will go in a large car. Hilariously, we pulled in a favour to get the wedges made - by a friendly undertaker. Oh well, woodwork is woodwork, just don't call them the Wedges of Doom.

And, sorry, pads?

Hope this helps,

P

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#7 Warwick Hempleman

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Posted 21 October 2010 - 09:53 AM

I feel compelled to add a few words about track diameter, gauge and lengths. Standard Track diameter globally is an o.d. of 1 1/2" which is roughly 38mm. 1 1/4" is also common, but you'll find that most dolly wheels roll best on 1 1/2" as the manufacturers tend to build to that o.d. Standard Track Gauge is commonly 24 1/2" which is roughly 62 cm. A common length is 8', but as Phil says, use the lengths you get, especially when you are working with your own straight sections. The wooden sleepers work well, but bear in mind what your load rating will be on the sections. Spreading the sleepers too wide will certainly result in sag, bending or in a worst case scenario, breaking. Are you planning to construct curves? On that budget? As Phil says, get quotes up front.

Phil, your dolly and track system looks great. Your description of how you've set it all up is excellent. I second your note on welding - don't do it (Pads lost me, too, by the way).




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#8 Steve London

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Posted 22 October 2010 - 03:00 PM

Phil and Warwick, thanks a million, gentlemen. I really appreciate your going to all the trouble to supply such detail and the benefit of your experience.

Phil, your point-by-point response answered all my questions, now I just need to adjust a few things for my rig. I'm definitely going to look into aluminum for the sleepers. I haven't been able to find hardwood at decent prices so was considering 2X4 lumber but it is very bulky.

One of the sources I consulted in planning this thing is from the great Ron Dexter: http://www.rondexter...dolly_track.htm

Here are those pads for the ends of the sleepers that I didn't describe well enough. So far, I don't plan to connect my tubes to the ties, rather to simply set them in the pads, which are molded to cradle them and prevent lateral movement. I'll have to think more about that now that you've explained exactly how you did it, Phil. I might bag the pads and attach the tube to the ties.

Ah, here are several snaps. I thought I'd resized them small enough for the forum but no, so they're on FLickr. Excuse the photography.

Modern Studio Equipment's excellent coupler
http://www.flickr.co...N05/5105784586/

Its inside
http://www.flickr.co...N05/5105178435/

One of the tie end pads cradling a tube.
http://www.flickr.co...N05/5105773364/

Pad end detail
http://www.flickr.co...N05/5105178335/

Notch in tube end required to access set screw. This pic is of the track I'm half copying after running into it on a shoot last month. I can't do this notch accurately with a hand drill, you really need an end mill in a milling machine, so I asked a casual friend who's a machinist. "Sure, no problem." "Okay," I say. "That'll be just $180." Yikes, but what else could I say? And I just found out this hour he cut 3/8" notches instead of the 1/4" ones that I asked for and that are all you need since it's just the hex wrench that has to fit in the notch not the whole 3/8" set screw. Ah well . . . :)
http://www.flickr.co...N05/5105773426/

Together in a scrap piece of tube with no notch.
http://www.flickr.co...N05/5105784562/
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#9 Steve London

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Posted 22 October 2010 - 03:09 PM

I don't plan to construct curves. They're nice but not as interesting to me as plain vanilla straight track for now.

(This will all change instantly when the right project comes along, of course.)
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#10 David Schmidt

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Posted 05 April 2011 - 05:52 PM

Hi Steve. Does the notch have to be drilled in the middle of the two ends? Would it be the end of the world if you shifted the coupler over 1/2 inch and only had a hole in one end of the pipe? If the couple is 6 inches long I would think it will still provide enough support and a smooth enough joint.
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#11 David Schmidt

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Posted 07 April 2011 - 03:09 PM

This might be a better solution for joining the track as you don't need to have the end notched for the set screw. You can drill two separate holes. I'm not sure if these will hold the track together as smoothly as the Modern Studio Coupler.

http://www.wagnercom..._Connector.aspx
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#12 Steve London

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Posted 12 April 2011 - 11:47 PM

Hi Steve. Does the notch have to be drilled in the middle of the two ends? Would it be the end of the world if you shifted the coupler over 1/2 inch and only had a hole in one end of the pipe? If the couple is 6 inches long I would think it will still provide enough support and a smooth enough joint.

I hadn't thought of this but I don't see why it wouldn't work just fine. Why would you want to do it this way, easier to drill the complete hole (which would be true)?
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#13 Steve London

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Posted 12 April 2011 - 11:58 PM

This might be a better solution for joining the track as you don't need to have the end notched for the set screw. You can drill two separate holes. I'm not sure if these will hold the track together as smoothly as the Modern Studio Coupler.

http://www.wagnercom..._Connector.aspx

These look really good, thank you. I see they come in 6" lengths. I haven't been able to locate a price yet.
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#14 David Schmidt

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Posted 15 April 2011 - 07:27 PM

These look really good, thank you. I see they come in 6" lengths. I haven't been able to locate a price yet.


If you go here https://www.shopwagn...m/nxc/nxcli.nsf and get to the product page. Type 3372 into the search. They are only 6.95.
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