Why Plastic

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Bruce Mowbray

Springville & Southern RR

From Archive.org

Why I'm Using Recycled Plastic For Ties

Pre-drilled and pre-slotted plastic tie.
  1. Plastic will last forever. I live in an area where the soil is mostly clay. Even though I have a lot of ballast and drainage around my track, the ground stays moist. Since this is my personal track, I did not want to replace any rotted or split ties....ever. I have seen pressure treated wood ties rot out after 6 years. Sooner with ties that were ripped from 2x6's as this opens the "less preserved" center of the board to moisture. Ripped plastic ties are unaffected in this way. The plastic is also UV stabilized and is unaffected by the sun.
  2. Recycled plastic ties will not split, warp, crack, check, expand, or shrink when driving screw in place or at any other time. In fact, the plastic holds screws better because plastic will not shrink and expand with moisture, therefore causing the screw hole to become loose fitting (like old furniture). Plastic has no grain or knots like pressure treated wood. Both of which reduce screw holding power. No worry about putting nicks in the grain which allows moisture to enter regular wood. Plastic is unaffected even when nicked.
Pre-slotted rail for rail-jointer
  1. Cost. I payed 54 cents each for my 2"x2"x16" ties. This may seem a little high at first but remember reason 1? I will never have to replace any ties. Not only is this a material savings but a labor savings as well. For reference, a quality pressure treated 2"x4"x 8' costs $3.50each, cut into six, 2"x4"x16" ties, it would cost you 58 cents per tie. (Savings??)
  2. Size. My 2"x2" ties are a full 2" by 2". Not 1 1/2" x 1 1/2". I like to build 2 1/2" scale equipment and these ties are a little closer to my scale. They also give a good support "foot print". I use 3 ties per foot which allows a 2" space between each tie. Its easy to tamp the ballast in this size opening and the ballast performs well.
  3. Holding Power. Not only do the screws hold well in the plastic, but the ballast holds the ties tight. Since the plastic is soft, the sharp, 3/4" crushed rock that I use for ballast "bites" into the ties when tamped providing a good stable track.
Custom-made tool for pre-drilling holes in plastic ties for the Springville & Southern RR.
  1. Recycled plastic is good for the environment. By using recycled plastic, not only do I reduce land fill burden (it takes about 300, 2 liter soda bottles to make one, 2"x4"x12') the recycled plastic doesn't leach harmful carcinogens and arsenic into the surrounding ground. It is perfectly safe to work with. No worry about breathing toxic sawdust or absorbing nasty chemicals through the skin when handling.

In addition to the above reasons, recycled plastic lumber is very easy to work with. I am using a fast cutting, carbide tipped saw blade to cut the ties. A little spray of silicone lubricant on the blade between cuts helps to keep the plastic chips from sticking to the blade. I am pre-drilling and pre-slotting the ties (see photo below) to ease the on site building of the track. The holes are spotfaced with a home made tool to a specific depth in relation to the slot depth. This way, even with the screw fully tightened, the rail foot will slide under the head of the screw instead of cutting into it. The slotting of the ties to correct gauge will eliminate the need for track gauges. Slotting and drilling the ties was done on my CNC Milling machine at a rate of 9 ties in 2 minutes. This could have also been done with a simple router jig and drill press. Another reason why I am using the "on site" track building method is, these ties are very heavy and a ten foot track panel would be next to impossible to move single handedly. "On site" track building also lets me get full use of a ten foot length of rail without cutting and the ability to stagger the rail joints more than the usual 1 foot amount. With this method, I was forced to slot the ends of the rail while it is still in the shop instead of slotting the rail joiners (see photo below). I believe this will allow the joint to move more freely as the screws used for the joint will not have to slide on the joint bar as well as the joint bar sliding on the rail. Only the rail and joint bar will slide and the screws will remain in stationary on the joint bar.

I was asked a couple of interesting questions about the plastic tie material and decided to do some tests to get the answers.

Expansion/contraction from heat and cold:

Using a 16 inch tie at room temperature, I took a precise measurement of it's length. I then placed it outside on a dark surface (to over emphasize the heat factor) in direct sunlight. The outside air temperature was 78 degrees. At the warmest time of day (mid afternoon), I quickly took the tie and once again measured it's overall length. The tie had grown .054" over it's 16" length. This would translate to a .024" increase in the 7 1/4" track gauge. (7 1/4" is 45% of 16", therefore, 45 % of .054" is .024"). Next I took the same tie and put it in the freezer overnight. The temperature in the freezer was 10 degrees F. Again I measured the tie and this time it was .030" shorter. Translating to a .014" reduction at the 7 1/4" track gauge using the same formula as above. Total difference in track gauge from 78 degrees, to 10 degrees, is .038".
With this result I may consider making the track gauge 1/32" wider. However, I'm not too sure if I'll ever run my steam engine when the temperature is 10 degrees F. Also, the temperatures of the ties may be less extreme once the ties are placed in the ballast keeping them cooler in the summer and warmer in the winter.

Fire resistance:

For this test I used a plastic tie and a sun dried pressure treated wood tie. To simulate a grass fire around the track, I used a propane plumbers torch. With the two ties close together, I put the flame on the corner of the wood tie and the plastic tie at the same time. The wood tie caught fire first and sustained a flame. The plastic tie melted slightly at first and finally caught fire but did not sustain a flame as well as the wood tie. When the flame was extinguished, the plastic tie remained the same color. The wood tie was charred and black. When the surface of plastic cooled and hardened it seemed to regain it's normal properties. The wood tie turned to ash and crumbled.
The next test simulated a hot cinder dropped on a tie. Since I didn't have any hot cinders handy, I substituted with a droplet of hot steel slag from a cutting torch.(this is much hotter than a coal cinder) The slag droplet was approximately 3/16" diameter. On the plastic tie, The slag melted into the tie slightly and a small flame appeared. It burned with a small flame for about 5 seconds and then the flame went out. It smoked for another 5 seconds and then stopped, leaving a small crater about 3/8" in diameter, 3/16" deep . On the wood tie, the slag caused a small flame. This flame continued until I extinguished it. It would have continued to burn if I had not done so, resulting in a total loss of the tie.
With this result, I will continue to use a closed ash pan on my steam locomotive. My trestles are made of wood.