Motorized Cable Trolley - Page 2 at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > Support Your Local Camera > Dolly / Track / Cable


Reply
 
Thread Tools Search this Thread
Old March 22nd, 2007, 06:19 PM   #16
Inner Circle
 
Join Date: Feb 2004
Location: switzerland
Posts: 2,131
50 lbs is huge. if you can accept to go with a 110v AC motor, you can take any motor (from a drilling machine for example or washing machine).
if you need to go on battery, it will be pretty difficult to find one.
http://www.surplusshed.com/pages/item/m2556.html
http://www.surplusshed.com/pages/item/m2237.html
but for the specs you mentioned, you will need a really bigger motor than that.
(do forget you have to move 2000' of cable either)
Giroud Francois is offline   Reply With Quote
Old March 22nd, 2007, 06:58 PM   #17
Regular Crew
 
Join Date: Apr 2003
Location: CA
Posts: 41
How about this

http://www.baldor.com/products/detai...GeneralPurpose
Jeremy Teman is offline   Reply With Quote
Old March 22nd, 2007, 07:22 PM   #18
Major Player
 
Join Date: Mar 2006
Location: Los Angeles
Posts: 439
I hate to be the bubble-buster, but this idea has red flags all over it.

How often will this system be used? If its a one-time thing, it'll be a LOT cheaper to rent. Also, if its an all-the-time thing or you're hiring it out, you should be careful of patent infringement. Checking patents on existing systems can help you figure out methods of implimentation, while also informing you of how you could possibly get in trouble. Believe it or not, you can infringe on a patent without ever selling/renting your construction. I believe Garrett Brown still has the patent on this technology. Just giving a heads up.

On the safety front, make sure that ALL liability is thought of. Cable can do nasty things under tension, things can fall, etc... And make sure to mount a stress indicator inline with the cable so you can monitor the forces going through it - safety first.

That said, sounds like a fun project. Good luck!
Jaron Berman is offline   Reply With Quote
Old March 22nd, 2007, 07:46 PM   #19
Regular Crew
 
Join Date: Apr 2003
Location: CA
Posts: 41
Renting is not an option, as we will be in many different locations and many different set-ups. A that price we could have ended up buying the $250,000 SuperflyCam. I believe their patents expired in 2004 actually.

I am aware the dangers of cable under tension.

Thanks
Jeremy Teman is offline   Reply With Quote
Old March 23rd, 2007, 02:18 AM   #20
Inner Circle
 
Join Date: Feb 2004
Location: switzerland
Posts: 2,131
the motor you mentionned look very nice.
It runs under 90V (not specified if AC or DV, nor if it can runs in both direction).
The power should be ok.
The only problem i see with our specs is the length of cable.
1000' is very long in one shot and you will need a huge tension to keep it straigth. Huge tension = big cable =really heavy weight.
you will have to make very precise calculation to know if the cable will be able to support its own weight + the weight of sled + effort on start and stop.
i am living in switzerland, so such installation (basically a small skilift) is not uncommon.
You should try to contact somes companies selling skilift for small place, you could get an almost ready made system for cheaper than in video systems.

look here, there is almost all what you need
http://skilift.nashacanada.com/
Giroud Francois is offline   Reply With Quote
Old March 24th, 2007, 08:09 PM   #21
Regular Crew
 
Join Date: Apr 2003
Location: CA
Posts: 41
The weight won't be bad. I'll be using a polyethylene synthetic rope with a breaking strength of close to 20,000 lbs for a 3/8" rope weighing only 3.5lbs per 100'. The rope only has a 4-5% stretch at the breaking point. So less than 1% at working load.

I wouldn't use a 3/8 at 1000', I'm just showing that it doesn't weigh much. The tension at about 400' is only near 1000lbs with weight on cable.

here is a link to an expample of how it may be made www.aptosproductions.com/example.htm
Jeremy Teman is offline   Reply With Quote
Old March 24th, 2007, 09:39 PM   #22
Inner Circle
 
Join Date: Feb 2004
Location: switzerland
Posts: 2,131
i think you will need to use a design of sled where there is no part hanging over or under the cable.(a flat box with cable running on the side) this will prevent balancing due to wind, acceleration and decceleration.
http://www.giroud2.com/divers/image1.gif
the cable in the middle is for support, while the 2 other cables is the cable loop for displacement.(that is not a good design because difference in tension will induce rolling, so i would prefer to have the support cable outside and the motor cable inside, with the motor in the sled, but this is ok for light design only because small motor and small battery)
you can even make the camera being static inside the box and make a small turret with a surface mirror that can be oriented.
so the mechanism becomes very small an light.
I think a 10 to 15 HP motor will be enough.
Giroud Francois is offline   Reply With Quote
Old March 24th, 2007, 09:44 PM   #23
Regular Crew
 
Join Date: Apr 2003
Location: CA
Posts: 41
The upper balance would be for a ken-lab gyro. I do like the idea of having a cable on each side. I've seen that design before and its works pretty good. Only thing is set-up times get much longer.
Jeremy Teman is offline   Reply With Quote
Old March 24th, 2007, 10:09 PM   #24
Trustee
 
Join Date: Nov 2005
Location: Sydney Australia
Posts: 1,570
Ideally you'll probably need two gyros. I'm told these things suck a fair amount of power and then you might have another issue. They obviously will resist all afforts at moving the rig so acceleration will be limited. Good controllers can be programmed to factor that in.
Quite apart from the mechanics the control logic could be quite a thing to engineer depending on if you want absolute positioning of the camera or not.
I'd also figure in some effort at the aerodynamics of the rig, at 35mph you'll have quite a wind load to contend with.
Some critical frequency analysis of the whole system might be warranted, a long cable with a moving load in the middle could get into a very nasty oscillation either excited by it's own motion or wind. Dynamic tension control might help or else magnetic dampers on the cable tensioners.
Bob Grant is offline   Reply With Quote
Old March 24th, 2007, 10:34 PM   #25
Regular Crew
 
Join Date: Apr 2003
Location: CA
Posts: 41
Wow, really you think it will take a 10-15hp motor? To the wheel that turns the cable I will only need about 850rpm with a 12" wheel. And I calculated the 50lbs of weight being pulled at a 45 degree angle and it came out it be about 35.4 lbs.

I was thinking about a 5hp motor geared properly would be fine, but I may be wrong
Jeremy Teman is offline   Reply With Quote
Old March 24th, 2007, 10:41 PM   #26
Regular Crew
 
Join Date: Apr 2003
Location: CA
Posts: 41
Bob, Those are some good points

The controls for the camera will be from a wireless remote head stystem that we're going to buy so that will make things a lot easier than making our own.

I think with the points you made Girouds recommendation of having two cables would be a much better idea
Jeremy Teman is offline   Reply With Quote
Old March 24th, 2007, 11:05 PM   #27
Trustee
 
Join Date: Nov 2005
Location: Sydney Australia
Posts: 1,570
I'd be looking at a cable to the camera for camera controls and power etc.
The batteries to run the camera, gyros and head are going to get heavy, really depends on how long you need to run the thing for. That does however add the complication of needing a cable winder with sliprings, messy for video but so is RF over that distance and very expensive if you're after a good live feed from the camera. Plus worse still all the RF systems have a big delay in them, the vision is encoded to mpeg-2 and then decoded in the receiver, something like an 8 frame delay.
Big problem during the Olympics down here, I think everything had to be delayed to match the roving cams on RF links.
Now that's fine when the camera operator sees the vision in RT but if you're trying to control a camera remotely with such a big delay, you'll have a problem.
Bob Grant is offline   Reply With Quote
Old March 25th, 2007, 08:15 AM   #28
Inner Circle
 
Join Date: Feb 2004
Location: switzerland
Posts: 2,131
Hmmm...
Dynamic tension control ,magnetic dampers, gyro, remote control, moving head, wireless transmission...
it iseems it will cost more than 10.000.
For the motor, you are right, 5 HP would be just enough, but it will suffer during acceleration.
for positionning on the cable, you put a simple wheel + a some reset mark on the cable (to prevent slippage) , it should cost almost nothing
you will find everything at http://www.totalrobots.com/access_fi...m#wheelwatcher
Giroud Francois is offline   Reply With Quote
Old April 3rd, 2007, 07:15 AM   #29
Regular Crew
 
Join Date: Oct 2006
Location: Victoria, Australia
Posts: 42
synthetic rope/wire, were would the best place to buy this be? I am in Australia so would it be better to buy local or from overseas which I am happy to if it is cheaper.
Andrew Fraser is offline   Reply With Quote
Old April 3rd, 2007, 01:44 PM   #30
Regular Crew
 
Join Date: Feb 2007
Location: Manchester, UK
Posts: 82
[QUOTE=Jeremy Teman;645249]Mostly action, sports, outdoor shots over canyons, events. Things like that.

QUOTE]

For that type of jobs I'd use a large RC Helecopter, except for covering stadiums that is. There is one available for around that price and they even include a HDV camera :-)
Andy Harding is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > Support Your Local Camera > Dolly / Track / Cable

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 07:59 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network