curved tracks

[Joel Arvidsson]

How do you calculate the degree you should use for the inner and outer track? Intresting get a curved steeltrack for my kessler k-pod.

 

[David Kuhn]

You'd need to drag out your highschool geometry text... given shooting distance, desired arc, and track spacing you can calculate the length and radius of curvature of both rails. OR... you could get the k-flex system that Kessler sells and lay it out to the curvature you need (If you do that let me know how it works out... I've got the k-pod & Pocket Jib and was wondering how well k-flex works).

 

[Terry VerHaar]

It's been a long time since my last geometry class but, the curvature of the inner and outer circles will be the same, so you just ned to know the distance you nned between the two tracks (dolly width) and the curvature you are looking for (i.e. what portion of the overall circle are you including). Then calculate the respective radii of the inner and outer circle.

I would think that if you get a supplier who has done this before they could be a big help. :smiley:

 

[Steve Das]

How do you calculate the degree you should use for the inner and outer track? Intresting get a curved steeltrack for my kessler k-pod.

They offer curved PVC track here in sections to make a full 360.

http://longvalleyequip.com/dolly.php

 

[Douglas Underdahl]

We offer inside radius of 4' and outside radius of 6'. One inside rail and one outside rail make one section. Each section is 45 degrees of turn; 8 section make a full 360.

My experience with the solid rubber flexible track is: it doesn't work unless you are on very smooth ground to begin with. No gravel, grass, big sidewalk cracks, dirt, floor to carpet, etc. PVC works great on all of this.

Douglas Underdahl
Long Valley Equipment

 

[Terry VerHaar]

Yeah - the flex track is sub-optimal. I wish I could say it worked well but, in my experience, it is just passable in a pinch. :-(

 

[David Kuhn]

Yeah - the flex track is sub-optimal. I wish I could say it worked well but, in my experience, it is just passable in a pinch. :-(

Kindof what I figured... though it sounds like for smooth floors it may be a good choice?

 

[Steve Das]

We offer inside radius of 4' and outside radius of 6'. One inside rail and one outside rail make one section. Each section is 45 degrees of turn; 8 section make a full 360....
Douglas Underdahl
Long Valley Equipment

Douglas how do you get the curved PVC track... is it custom made for you..?
The original poster was looking to use Kessler K-pod dolly skate-wheels on the track...I assume your 1-1/2" diameter PVC would work..but do you know for sure..?

 

[Douglas Underdahl]

How to curve PVC pipe:

Step one - build a seven foot long oven. Next, experiment for a year making rigid forms and clamping systems, then heat the pipe to different temps, testing each run, then . . .

I think our track will work with the Kessler track dolly trucks. Our trucks not only swivel, they slide from side to side on teflon coated UHMW bearing plates, so that the dolly will ride smoothly around our curves.

 

[Robert Ruffo New]

Kindof what I figured... though it sounds like for smooth floors it may be a good choice?

Better choice on smooth floor is just a doorway dolly as you will be able to dolly as far as the floor goes, will not need to lay down any track, and even steer to make circles - so flex track is essentially useless, it only works where you don't need track at all.

 

[Brian F Kobylarz]

How do you calculate the degree you should use for the inner and outer track? Intresting get a curved steeltrack for my kessler k-pod.

Not a direct answer to your question (one of those days I wasn't paying attention in math class), but from the practical side, perhaps this will help.
A number of years ago I purchased a lot of precision track manufactured by Matthews - including two different circles (10' & 20').

Both the straight and curved track measures 24.5" center to center.

It takes (4) pieces of the 90 degree track to make a complete 10' circle (10' is measured as the outside diameter).
4 pcs @ 90 degrees each = 360 degrees

It takes (8) pieces of the 45 degree curved track to make a complete 20' circle (again measured as the outside diameter)
8 pcs @ 45 degrees each = 360 degrees


Though I don't own any of this size, logic would say that a 70' circle would require (16) pieces of track curved at 22.5 degrees.


If considering attempting to manufacture your own, the real math trick is measuring the difference in length between the inner and outer rail - that's where the 24.5" comes into play in the formula...
It needs to be absolutely precise as any gap can affect the shot. This is where using sleds (aka centipedes) becomes essential.

 

[Brian F Kobylarz]

Better choice on smooth floor is just a doorway dolly as you will be able to dolly as far as the floor goes, will not need to lay down any track, and even steer to make circles - so flex track is essentially useless, it only works where you don't need track at all.

Or an Elemack if you can find one locally. They can move tighter than a doorway dolly, perform "dance floor" moves - many possibilities.
Repeatability is where curved track is great - even on a smooth floor, a doorway dolly seems to drift from take to take. If time permits, I'll go for the track.

Have one piece of flex track. Comes in handy less than once in a blue moon.
Sometimes however, you might need to do a strange "s" turn between objects on set - that's one of those occasions.
Other than those unique shots, agree with the feedback...