Calling all math gurus of circles!

I'll get you started... The formula for a circle's circumference:  C = pi * d, where d is the diameter, and you can estimate pi as 3.14.

 

Now you just need to account for the various diameters of the inner rail, the center rail, and the outer rail... and you should be good to go.  

 

David

David -

That's pretty much where I started. Somewhere i think I have it twisted in my head as the result I am getting just doesn't 'seem' right. Working with 16 pieces I get a circumference (i.e.  16 x 39.75" = 636), that result divided by Pi....then divide by 12...to yield a diameter of 16.871 feet.

 

For a 40" piece of track....well, it just doesn't seem "large" enough.

 

FWIW - this isn't all in vain. I'm trying to plot post positions for an outdoor setup. Flex track might/should/could be a bit more forgiving to work with (and yield a larger turn) than pre-defined track.

hang on...I found my twist!

 

16 pieces for a FULL circle...yet in my head I was visualizing 16 pieces to a half circle.

 

And...thank you!

Assuming that the outer rail is not cut and each section is 40", your first question is what diameter curve can you get.Your first hurtle is bending the track without kinking it.

 

2 sections 80/pi = 25.46

3 sections 120/pi = 38.19

4 sections 160/pi = 50.92

(I wouldn't even try these)

 

5 sections 200/pi = 63.66 maybe

6 sections 240/pi = 76.39 probably

 

O gauge track is spaced at 1.25". So 76.39-2.5 = 73.89 (inside diameter)

 

73.89*pi/6 = 38.69 the length of the inside rail on each section.

 

There's the math. If I'm wrong on any of my assumptions, I'm sure we'll hear about it. Good luck.

 

Gilly

 

BTW, there are benders you can buy for use with flex track. If I were doing it, that would be my first purchase.

So--Your question is- 

If you cut one inch off the inside rail of a 40" piece of flex track, what size curve will it produce?  

 

Your diameter of 16.871 feet for 16 sections seems right to me.

Gilly, I take it O gauge flextrack is significantly different from HO gauge flextrack in workability? I've seen comments saying ScaleTrax flex is easier to work with. Is that true or do you recommend a tool for that too? I assume the tool is only needed if bending it for curves rather than just for sweeping curves on straight runs?

Mark - that's what I also got. Somehow i co-mingled (synapse mis-fire!) the number of pieces and the diameter...and well, my visualization hit a snow bank.

 

Still. 16 pieces to the full circle is based on 22.5° bend for each piece. I don't know that I am on the right path in that regard.

 

Ultimately, I am trying to get to about 30 feet diameter on the one end of this loop. The area of yard is a curved cone shape and lies between a retaining wall and a brick pathway. The wide end is about 35 feet and the narrow end is about 10 feet, with an overall length of about 80 feet. Hence the need for the cut measurements for each piece for the end loop backs. Once I know the lengths of the loop backs, I can then plot the post placement based on X distance between posts for support.

Dave,

 

My limited experience with flex track is Atlas solid rail, nickel. It is a bugger to bend. I would assume that everything else is probably easier to handle. And yes, if I were doing it, I'd invest in a bender. Kink or mess up just a few pieces of track and the bender is "free".

 

Gilly

Gilly - are the benders so equipped that you can set a degree of bend, or are they more of the variety of trial and error? I should note that all of the track is Atlas.

 

I had considered buying a planetary bender for the support structure but opted out due to the expense of it.

Mark,

 

The more common approach to track bending is to mark out the position of the centerline of the track as desired on your property. Some large plywood templates of the desired curve may help with the accuracy of the plotting. The curves themselves are "drawn" using string of the required length (radius) as a compass to swing the arcs.

 

Then bend your curves to follow this arc. The number of track pieces is immaterial since you will be cutting and bending as required to follow the centerline you plotted.

 

Very often, the last couple inches of each flex section cannot be bent accurately and should be cut off to achieve a smooth curve and avoid kinks. Trying to use every inch of every track section may be an exercise in futility.

 

Jim

This one looks pretty trial and error, if this is what he's talking about.

Good point, Jim. I was edging toward being able to pre-cut the pieces for easier assembly/controlled waste rather than piece-by-piece custom cuts. The support structure will force some conformity...and I still have concerns about the ends of each piece.

 

As for the exercise in futility, I'm one of those guys who - at leisure - can get covered up in analysis paralysis...and all so that the hind site isn't quite so regrettable! The former costs me only time, while the latter has chewed up more than I would mention! I guess it comes from an old boss who drove home on every project to plan for what we don't know for certain.

Mark,

 

I totally understand the "analysis paralysis" syndrome!

 

I was a victim for quite a while until I adopted a more practical - plan less, just get going with it - mentality. I have been getting much more accomplished that way in recent years.

 

Just an added note on rail benders - these require you to remove the rail from the ties for bending, then reinsert back into the tie strip. This is not always possible with some brands of O gauge flex track. For example, the tiny plastic nibs holding Atlas rail are prone to breaking when this is attempted.

 

Jim

 

 

I will toss in that ScaleTrax does not need a tool to bend, the stuff is like a noodle compared to other brands.  I can bend it down to O-20 with my hand.

I highly recommend the Videos at  www.toytrainsontracks.com for working with flex scaletrax. I have the first 2 and they make it look easy. There are lots of other layout tips in them as well.  And some decent video of trains running on ScaleTrax to see if you like it.

Russell, are those the Black Diamond videos you are talking about? That was all done in ScaleTrax? $80 for RR-Track and $50 for videos, $30 for the DCS book, when do I get to lay some track? 

Jim -

It took me awhile - but I was finally able to work through the issue. The key was the desire to be able to mate up to pre-defined curves from Atlas O - all of which are at 22.5° or 11.25°...which dictates either 16 or 32 pieces of track for a circle. From there, the rest was an easy formula.

 

And while just forging ahead has validity - these days i am more apt to plan..and plan some more. I really like just taking steps forward.

Yep. Besides the lifetime supply of motor grease, ijust picked up for $4 and the coal I glued to a coal car last night, I haven't found the inexpensive part of the hobby yet . I do think track planning software pays for itself, in extra track not bought though.

Ok, ordered the vids. I'd order the others too, but I'll wait until we return from FL. Maybe I'll get the vids before we leave on the 15th.