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 Well, Hello Dolly! 
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Joined: Tue Aug 26, 2008 3:30 am
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Location: Sydney, Australia
Post Well, Hello Dolly!
At last I have gotten close to finishing my 'working in progress' monorail rig. :P :P :P

It has an adjustable dolly/cart that allows it to run on all sizes of extruded profiles in realtime and T/L.
This means I can configure it from a lightweight luggable for DSLR work, up to a grip assisted location dolly capable of carrying heavier production cameras.
I can swap motors, mount a 90 degree cheese plate if needed, to operate in elevator mode, and run underslung.

The larger profiles allow me to support the 'track' from one end only and 'arm' it out over water, cliffs etc., as well as providing increased stability when operating in elevator mode and the ability to rig cross arms for different camera mounting.
Planning to go 'outback' and shoot some demo stuff next month, after finishing up on a current project.
As pictured it is mounted on a small length of 100mm x 100mm (approx. 4" x 4") profile with an industry standard riser.
(The miniDv camera is purely for scale.)


Sun Jul 04, 2010 11:47 pm
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Location: Stockholm, Sweden
Post Re: Well, Hello Dolly!
Nice one, looks sturdy!

Was the choice of beam dictated by being able to carry heavy 35 mm film camera gear?

I've been looking around to see if anyone has built a monorail dolly rail from something more lightweight, such as a 2" x 4" extruded aluminium rectangular profile, with self-propelled dolly wagon, but can only find the more heavyweight rails.


Mon Jul 05, 2010 1:05 am
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Post Re: Well, Hello Dolly!
Yes, the dolly can be configured to run on light weight profiles as well as the heavy duty profiles necessary to carry 35mm cine cameras and the heavier HD digital cameras.

Some inventive members of this forum have built their own rigs in the style you were enquiring about, for example check out Andrew Curtis's clever design :

http://timescapes.org/phpBB3/viewtopic.php?f=30&p=16600#p16600

..... and there are other members rigs further down the page, as well as the soon to be released : http://timescapes.org/phpBB3/viewtopic.php?f=24&t=2363

EDIT: 03-03-11 The dolly details mentioned above : http://www.dynamicperception.com/


Mon Jul 05, 2010 1:20 am
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Location: Stockholm, Sweden
Post Re: Well, Hello Dolly!
Thanks for the links!

I have a couple of square aluminum tubes, a Basic Stamp, a Pololu motor controller, an LCD display and a couple of geared motors left over from a yet to be finished camera crane project. I'll try to convert those pieces to a time lapse rig!


Wed Jul 14, 2010 1:36 pm
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Post Re: Well, Hello Dolly!
That looks so awesome! Can you post more pics?

I think I'm going to loan some ideas from you ;)

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Wed Mar 02, 2011 7:06 pm
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Post Re: Well, Hello Dolly!
@ rikun, have you seen this clip? :

And here are some pics.


Attachments:
Mono Dolly A.jpg
Mono Dolly A.jpg [ 60.99 KiB | Viewed 7193 times ]
Mono Dolly B.jpg
Mono Dolly B.jpg [ 71.07 KiB | Viewed 7193 times ]
Mono Dolly C.jpg
Mono Dolly C.jpg [ 44.46 KiB | Viewed 7193 times ]
Wed Mar 02, 2011 11:08 pm
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Post Re: Well, Hello Dolly!
Yeah I've seen them all, looks kick-ass.

How big is your timing belt? I was considering a HTD 5-9MM, but it seems to have a Admissible Pulling Force of 208 Newtons. I don't fully understand physics and forces, but I'd guess it means that I could safely move a bit less than 40 pounds with that belt. Am I assuming correctly that the pulling force is theoretically my payload(N) in Omega-drive configuration?

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Wed Mar 02, 2011 11:38 pm
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Post Re: Well, Hello Dolly!
The belt width is 15mm ( 5/8th in.) with a good tensile strength.
Heavy duty timing belts are also available for serious loads - just ask your friendly rep for details. :)
Some can even suggest the correct type depending on speed required, load and motor/gearing, etc.


Thu Mar 03, 2011 12:27 am
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Post Re: Well, Hello Dolly!
Well... Looks like I was looking a particularly weak belt design. Seems that most of the HTD5-9MM belts can take a lot more force...

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Thu Mar 03, 2011 12:29 am
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Post Re: Well, Hello Dolly!
Thanks. Would a rubber belt reinforced with fiberglass work? That's the only thing my local dealer is offering, I'm having a gut feeling that it's going to be too elastic...?

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Thu Mar 03, 2011 6:41 am
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Post Re: Well, Hello Dolly!
My understanding is that the HTD range are of rubber construction for general applications.
You may have to make enquiries about industrial timing belts.
Some of these are manufactured "from high tensile steel cord tension members and wear resistant polyurethane" :geek: (from our local suppliers ad).
These offer dimensional stability, low friction, and high performance.
In other words they don't stretch or break that often. ;)


Thu Mar 03, 2011 2:18 pm
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Post Re: Well, Hello Dolly!
This is an example of the use of a Kevlar backed heavy duty timing belt on a modified and motorised Matthews wheel-set on a custom dolly base.
This motor adapter was built over 16 years ago for repeatable moco work and is still used now and then. (At the time the belt itself cost over$1,000! :o )


Attachments:
Narrow Gauge MoCo Dolly.JPG
Narrow Gauge MoCo Dolly.JPG [ 30.65 KiB | Viewed 7144 times ]
Motor Plate Moco Dolly.JPG
Motor Plate Moco Dolly.JPG [ 31.72 KiB | Viewed 7144 times ]
Thu Mar 03, 2011 3:13 pm
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Post Re: Well, Hello Dolly!
The rubber belt had a break strength rating of around 1500 Newtons, which would be plenty. But I'll have to ask them about the stretching, seems quite obvious that rubber stretchs way more than other materials...

If I indeed need an poly belt, I'll have to order probably from the States. What kind of actuators are you using? I'm trying to decide whether the 80/20 pads would be good enough, probably not... I've used them a bit on a different application in the past and they seem to have lot of play.

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Fri Mar 04, 2011 10:53 am
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Post Re: Well, Hello Dolly!
I'm using slot rollers - these are normally used to 'hang' heavy sliding doors and obviously travel in the slots.
To compensate for any play present, I tension one or two the rollers to keep a good fit, if necessary.


Sat Mar 05, 2011 10:16 pm
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Post Re: Well, Hello Dolly!
Looks like a very sturdy rig. Great work! What kind of motor did you use for this setup? (gear ratio / voltage / amps)


Sun Mar 06, 2011 4:50 am
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Post Re: Well, Hello Dolly!
Yeah I know the slot rollers, I guess using the pads one could achieve almost similar results. How big is your main pulley, looking at the pic it looks pretty small?

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Sun Mar 06, 2011 2:54 pm
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Post Re: Well, Hello Dolly!
Matt, who builds all this heavy duty stuff? Do professional photographers build their own or is the work farmed out to machine shops?


Sun Mar 06, 2011 4:00 pm
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Post Re: Well, Hello Dolly!
@aidanmaguire, the motor is a double-stack Nema 23, 1.7 volt, 4.7 amp stepper. The gearing is controlled via the software (which is either Kuper or Lynx, both proprietary moco software).

@rikun, the drive pulley is small - 2.5cm/1", as the motor drives can supply high current. When used on location the drives require 24v to 36v for efficient operation.

@jim, the custom equipment is generally fabricated by mechanically minded grips who have a great knowledge of the workings of all sorts of film gear through hands on experience,
or machine shops that specialise in film equipment repair and refurbishment. This is pro gear that can't afford to fail on a full on shoot.
There are of course photographers and DP's who know their way around inside a machine shop. :-)


Sun Mar 06, 2011 5:01 pm
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Post Re: Well, Hello Dolly!
Are you running a regular belt, or a "no backlash" type? I guess it's not necessary to get so fancy with the belt, I'll just order something that feels right :-)

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Mon Mar 07, 2011 11:24 am
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Post Re: Well, Hello Dolly!
I'm using a polyurethane timing belt - "used for high precision positioning applications" , is how the German catalogue describes it.


Mon Mar 07, 2011 4:12 pm
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Post Re: Well, Hello Dolly!
That would be AT or ATL belt in metric countries, I checked it up :) And if one requires ultimate precision, a pulley with "reduced backlash" or "zero-backlash" type should be used.

I see you have some weird device to adjust the belt tension. Adjusting the tension is the final thing to settle before I'll order my parts.

Do you know how tension plates work?

http://mulco.gwj.de/en/p_20369.htm

I assume somehow the screw at the end tightens the belt, but how? Is it attached to the belt somehow? That's the only way I'd think it would work...

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Wed Mar 23, 2011 12:36 am
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Post Re: Well, Hello Dolly!
The weird device is an adjustable and lockable toothed wheel that the belt passes through to allow the use of a longer belt on a shorter length of profile if necessary.
Like all prototypes it seemed a good idea at the time and is probably overkill for most applications.

An earlier 'belt-holder' was simply a machined template that matched the teeth of the belt with then another flat plate on top to hold the belt in position and attach it to the centre of the profile.
A version of this type holds the belt on the other end of the profile in the photos.
These attachment devices are usually sold or can be sourced by the timing belt manufacturers as per your example.


If you are familiar with turn-buckles you can place one in between your belt holder and profile attachment point and tension accordingly.
Or use a tension screw unit that you refer to. By turning the thread you pull the belt through the toothed template til it 'fits' in the matching metal template then lock it home.

EDIT: Photo insert (25-3-11)


Wed Mar 23, 2011 4:02 pm
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Post Re: Well, Hello Dolly!
Thanks for the tip about using a turnbuckle to set the tension! I was going to buy the tensioning-type clamps, but they are ridicously expensive. Now I can just get the normal versions and make my own tensioning system :)

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Thu Mar 24, 2011 3:03 pm
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Post Re: Well, Hello Dolly!
I was looking at the t-slot rollers... They seem to be rated for very small loads. Using at least four of them might be ok, but still...

Does your dolly have some kind of heavy-duty variants ;)?

Attachment:
tension.png [97.8 KiB]
Downloaded 212 times


This is how I'm planning to tension the belt. The tensioning bolt is missing from the sketch (and the threated hole at the end of the clamping plate for it).

The belt is first clamped between the clamping plates, but the clamping plate is not completely tightened down to the extrusion yet.

Then the tensioning bolt is adjusted until enought tension is present and the clamping plate is tightened down to the profile grooves.

The only problem I see is using the same holes for clamping the belt and for tightening the whole assembly to the profile. Tightening the belt enough, yet leaving the clamping plates loose enought might not be possible...

*edit*

I guess I need to make separate holes for attaching the clamping plates to the profile and to sandwitch the two plates together...

Any thoughts? Have I completely misunderstood everything ;)?

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Thu Mar 24, 2011 6:17 pm
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