# Calculating tack length requirements



## jtutwiler (May 29, 2008)

First of all, I want to state that I am very bad with math. That having been said, I am in the preproduction stages of my railroad and I am trying to figure out just how many feet of track I am going to need for a 20 foot diameter circle. So, without ribbing me too much, would somebody be willing to help me out here? I vaguely recall something about pie and circles, but in high school as a growing boy, I think that I was focused on ... well, let's just say "other things" /DesktopModules/NTForums/themes/mls/emoticons/whistling.gif 

Thanks for any help


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## Semper Vaporo (Jan 2, 2008)

I remember the forumlas because of an old joke: 

The old backwoodsman sent his son to school to get some learnin'. The kid came home after a year of school and the old man asked him to say something to reveal his new learnin'. 

The son replied, "Pi R Squared." 

The old man, became quite agitated and said he' never let his son return to this school. 

"Pie are round, it be da' Crumb Bread are square!" 

Anyway, you don't want the Pi*R^2 formula... that is for the Area of a circle. 

You want the other forumla, Pi*D to get the circumference. 

So 20-ft times Pi (3.14159....) Equals about 62.83 ft. give or take a few inches for thermal expansion/contraction.


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## R.W. Marty (Jan 2, 2008)

Hi, 
The formula for the circumference of a circle is: 
pi (3.1416) times diameter or in this case, 
3.14 X 20 = 62.8 feet. there are other ways but this answers the question. 

You should always buy a little extra. 
Later 
Rick Marty


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## barnmichael (Jan 2, 2008)

Track is like desert, teddy bears and clamps. You can never have too much/many. 

You're going to tire of a plain circle real quick and want to do more. If you have access to a good rail bender (train-li), then I recommend you get all the track (at least 100 feet) you can afford or borrow for, regardless of straight, curved or whatever. Track prices are going up almost every day. You'll use it all eventually. 

Michael


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## jamarti (Jan 2, 2008)

Does Aristo track still come as one full circle in a box? Buy a box of 20' diameter track and you have the full circle. Buy a box of 10 ' diameter track you still get a full circle. It's just a smaller circle....


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## Torby (Jan 2, 2008)

And you don't need to figure to the millimeter. Track isn't very precise stuff.


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## jtutwiler (May 29, 2008)

Thanks for all the help. I am not putting down just a circle of track. I am installing a raised track (about 3 feet), I am going to have two ovals running in a space that is about 20' x 35'. I am also putting in a yard off of that and an additional section of track as a point-to-point railroad. That way I will get the best of both worlds. I just was trying to figure out how much track I needed for the curves. I didnt want to get started and not have enough! Thanks again


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## Torby (Jan 2, 2008)

Well, R.W.'s figure of 63 ft is a good place to start. Then add in the straights...


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## Joe McGarry (Jan 4, 2008)

BTW, Yes aristo track comes a full circle in a box. The larger diameter circles come 16 sections in a box. 4 sections give you a 1/4 circle or 90 degrees. Take a look at the Aristo catalog on the web. They have a track diagram showing circles, straights, switches ,etc. Hope this helps your track planning. 

Regards 

Joe Mc


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## Brendan (Jan 12, 2008)

Why not draw a scale plan or use a garden hose, make a full scale rep of your layout and measure the hose.


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## Pauli (Jan 3, 2008)

I have used a rope with 12 equal distance knots - in my case 1m. When you make a triangle 3x4x5 units, you get a very accurate large 90* angle, wich I found helpful, especially if you use sectional / pre-curved track. (This trick was used by the Egyptians building pyramids and stuff ;-) 
I put stakes in the ground, marking the layout. Then I assembled most of the track and trackbed, before I actually raised it, using 2 reebars every 0,5m (1,5 foot). 
The whole process was very rapid, and I got a track to run on in only a few days. You can se the whole process at http://web.mac.com/anders.grassman/iWeb/Topsida/Einfach_Garten_Gleisbett.html 
However, you have to use twice as thick wooden planks, than depicted, or they will sag in a few months... (I added iron angle underneath.) Also, I found electric cable straps to weak, and replaced them with the common soft iron wire normally used to join reebar. The track has remained stable and useful since. 
But, after a few derailments causing the trains to plunge 2,5 feet to the ground, I've decided to use the much wider (discarded) restaurant trays as roadbed for a replacement layout. The trays are of laminated (dishwashable) wood = extremely weatherresistant and incredibly stiff. 
I guesss I diverted some from the subject... ;-)


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