Heavy duty dolly

T

tomfrew

New member
I recently built a jib from steel and it is very heavy, between 400-500kg and im trying to build track wheels for it.
The base is about 1.2m long and so i was think of using angle iron and skate board wheels in the v formation. I was thinking about 20 on each side of the platform.
Does anyone know is this would this be sufficient to support it? and also would this be too much weight, spread over 40 wheels over 1.2m, to be supported by pvc piping?

attached is my current design idea.

Thanks
 

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How big is the jib? How big of a camera is it set up for? If my conversion is correct you're talking about around 1,000 lbs? I think you're going to have trouble using skate wheels for something like that.
 
thanks for you help everyone.
I 500kg figure was the top end of a very rough estimate. i think it is probably around 300kg. but i would like to a track set up that could support some extra weight and the weight of someone standing on the base.
sadly i have no pictures as it is at school. i made it as a gcse dt project and have no room for it at home...yet. next term i shall take some pics. but i so have some footage from a short film i made which was film with it. The motorised head only has switches and so the video is not as smooth as it could be. (im currently building a joystick control and a remote focus and zoom.)
http://www.youtube.com/watch?v=jsx4Zrq5aew

Thanks again for your suggestions.
 
Try angle-iron for the track. Heavy, but lays perfectly and is easy to extend without gaps.

Also, you don't need so many wheels. I built a massively-heavy dolly and 16 hard rollerblade wheels were ample.
 
The skate wheels will take it aslong as you have enough of them and you arrange it in a way that devides the weight.

Lets say you had 8 along each side, so thats 16 on each rail and 32 in total.

Your 500kg devided by 32 = 15kg on each wheel which isn't a problem at all....
 
skateboard wheels can get expensive. 8 is ok, cost $40. but to do 40 wheels is another question. You might as well just use 8 better wheels instead. But if you still use all the wheels, im sure with all that weight it would be really hard to push the jib.

Instead of the pvc I would use a long angle iron. Like the ones you attach your skateboard wheels too. Since its a right angle the wheels would fit on it alot better then pvc. I know this because I made an 8 wheeled version of what you your making. very smooth
 
hmm I pay about 5 to 10 bucks for 8 wheels, nice ones with real bearrings, take a look at skate.com they sett them sometimes 8 for 5 bucks,

what is happening is skater punks buy the boards with nice wheels, but want nicer wheels, so the pay extra, and skate.com resells the old wheels (still new actually) for cheep. its win win win.

Jason
 
tomfrew. I really dig your footage. Very nice. What were you shooting on and to echo what reaktor asked, "what CC did you use?"
Cheers.
 
Hi - I am a mechanical engineer and your post caught my interest.....ok this basically boils down to a strength of materials type problem.

So you have a jib that is about 500 kg....on a 1.2 m track. Basically...this can be converted to a distributed load (which you already did by using a 6.5 kg/cm^2 load).

So - my advice would be to get some type of materials handbook - or look this info up on the net.....you really need to look at the material's strength to see if it can handle your weight....PVC may be able to do this depending on the diameter and wall thickness of the pipe you want to use. Also - I would investigate the radial strength of the bearings that are in the wheels you are using....too much weight/stress on the bearings could actually cause them to not be able to rotate.

As far as materials for the tracks/wheels....

I would look through McMaster Carr and Grainger - both are industrial supply companies that offer any kind of part imaginable for any type of job....they have extensive online catalogs and tech support that you can call with questions. I have used these for many projects....and they are invaluable.

PM me if you have any other questions.
 
i have a question. What do you guys usually use, wheels meant for skateboards or wheels made for rollerskates. The rollarskate wheels are a bit bigger and thinker compared to the skateboard wheels.
 
Thank you very much for everyone responses.

The footage was shot with a JVC HD100 on HD miniDV. It as CCed with look suit from red giant.

Jguentner77 thank you for you help, i'll have a look at the sites you recommended.

Thanks again.
 
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