# new build by a newbie



## jkstewart1 (Dec 14, 2005)

Building a trial track. Using MDF and tie wire for the rails. Can anybody tell me how tight a curve Luf's lexan strip will make? I have plans for two 3" hairpins, but I didn't know if the strip will curve that sharply. I wanted to find out before I invested in one. 

Thanks! John


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## wm_brant (Nov 21, 2004)

John --

I broke one of Luf's flexible strips laying out a 1/43 scale track three years ago. I know I was laying out the track when the strip broke, but I cannot remember exactly what part of the track I was drawing. I do know I was trying to use the strip on the inside of a curve when it broke. The curve might have been the inner lane, or it might have been the inside border, I just cannot remember.

I would guess the breaking point for one of Luf's strips is for a curve with a radius somewhere between 5" and 7", but that is only a guess.

Also keep in mind that the base of your router needs to go on either the inside or the outside of the turn you are routing. I used a Ryobi laminate trimmer with that track, and it had a 3" diameter base, which at the time was one of the smallest bases you could find on a laminate trimmer. 

With a 3" diameter base, to route a 3" radius turn you would either a) have a strip of something rigid but also have zero thickness and route around the outside of that, or have a 6" diameter circle, and run the router around the inside of that turn. Basically, what I'm trying to say is that a 3" turn is not something that I would try on my first track, especially an HO track where you not only have to route the guide slot, but two adjoining rail slots...

-- Bill


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## jkstewart1 (Dec 14, 2005)

Thanks, Bill. I bought the same Ryobi laminate trimmer based on reading your posts. The simplicity of routing the second lane by dropping a piece of sintra in the first slot was too appealing.

I figured that routing a curve of that tightness wouldn't be much different from routing other curves and routing the rails just takes a decent jig. But, I'm sure that there's more to it. There always is.

Would Luf's strip work for me if I could lay it to the six inch diameter? The board is approximately 4'x5' and I planned on using it to hone my skills while providing a fun little course for my son to have in his room when I'm done. I have an L shaped area that is 7'x14' by three feet wide in the basement to do a larger track in. I'm hoping to be able to get four lanes of racing in that space.

John


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## wm_brant (Nov 21, 2004)

John --

If you attempt to route a 3" radius turn using a 3" diameter base, you are going to have some funny results.

A 3" radius 180-degree turn would come out as a straight line ending 1.5" from the flexible strip.

A 3" radius 90-degree turn would come out as a right angle.

As a practical matter, the turn is going to have to be larger than 3" in diameter.

Also keep in mind the following: 

If using the Sintra copying technique, you will almost always have at least one lane of a smaller diameter than the lane you are routing
You will need to route the rail slots, one of which will always have a smaller radius than the tightest guide slot you have routed.

My recommendations:

Buy Luf's flexible strip and practice with it. See just how small a radius you are comfortable bending it into. You might plan on buying two strips if you are set on working with small diameter turns.
Practice on small sheets of MDF first!
Go with turn diameters larger than the smallest possible ones you can make. The tight turns are not only hard to create, they are hard to drive.
3mm Sintra is a snug fit in a 1/8" (equal to 3.2mm) slot. For a 1/16" slot, you will need to find a source of 1.5mm Sintra, which I'm not sure is available. You might need to use another material, or go with the template routing approach (which I think is the best way to go for HO tracks).

-- Bill


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## jkstewart1 (Dec 14, 2005)

I wasn't sure how tight a turn the cars would handle. I see what you're saying on the radii examples. Thanks for all of your help!


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