Modern Flexible HDPE Ladder Roadbed, Wood Trestles & Bridges

[John_Carmichael]

Modern Flexible HDPE Ladder Roadbed, Wood Trestles & Bridges

- YouTube

This how-to video describes our modern flexible HDPE (High Density Polyethelyne) ladder roadbed, redwood timber trestles and bridges for the Cholla Patch Railroad in Tucson AZ. I highly recommend this type of roadbed for its ease and speed of construction, low cost, durability and beautiful curves.

Our non-traditional flexible roadbed is made from 3/4" thick HDPE house siding ripped into 20ft. long thin strips. I made the roadbed by attaching two HDPE strips together using short pieces of composite wood that I call “brownies”. Video has useful design plans, graphics and assembly photos, and shows the advantages of this modern roadbed construction design. All the wood pieces are redwood, stained and sealed with Minwax dark walnut stain before assembly, then glued together with Titebond III secured with solid Brass Escutcheon pins (brads). I made printed templates of the pieces needed for everything. I attached the template drawing of the biggest trestle to particle board, making a sturdy wood jig for easy assembly. Wood is re-stained about every four years. I think you’ll also enjoy seeing the detailed and extensive wood trestles and cool wood Bridges.

Feel free to copy, use or modify any of the images or video shorts you see here. I highly recommend this type of roadbed. I hope this helps you make your decision on the type of roadbed and materials you’ll use for your own garden railroad. - John Carmichael

Side Note: I beg your pardon as I must admit a big mistake. I’m not a chemist, and I’m old, so I mix up chemical names- I previously told you incorrectly that I used HDPVC (High Density Polyvinyl Chloride), but it was actually HDPE (High Density Poly Ethelyene). I just plain forgot the name. Please excuse me! I’ll try to fix this error by editing my previous posts & video.

TrexTrim is the material I used. It is PVC lumber but is very similar in all ways to HDPE lumber. It’s very flexible, but I don’t know if it is more or less flexible than HDPE. I bought this size: SKU: WW010618B. This measures: 3.4” thick x 5.50” wide x 18 ft. long (actual). It’s white with wood grains. I had the supplier rip each board into 1.75” strips for the stringers. Wider boards are available but all will need ripping. The supplier delivered the ripped strips to my home for a small fee. Website: Trex trim brochure - Trex Inc. - PDF Catalogs | Documentation | Brochures

See my other projects here Cholla Patch Garden Railroad Design & Construction Series:

[Pete_Lassen]

Do you bend curves before attaching the second side to the siding ???

[John_Carmichael]

Pete Lassen:

YES! absolutely. I start by laying a single side of the highly flexible roadbed (with browines pre-attached) on the ground. After bending it to the perfect desired curve, I attach the other side.

With both sides attached, the roadbed become inflexible and retains the curve you wanted.

After the curves are correct, and both sides of the stringers attached, I raised the roadbed to the desired heights.

[Pete_Lassen]

Thanks John, I appreciate the info, I MIGHT be Making a track from back yard into the front yard and it will have to be elevated to match up to the back yard.
What brand of siding and do you have to buy a bundle or can a can they be purchased individually. Probably only need 3 or 4 , depending on how much front yard I am allowed to use

[John_Carmichael]

Websites on Post & Ladder Open Stringer Roadbeds:

This 4 part article series is the best online information I can find on ladder stringer roadbeds. It describes inventor Paul Logan’s flexible stringer and post construction method. It’s often called the “Post & Ladder” method. This was the basis for my own railroad. I modified slightly Mr. Logan’s design and construction technique to improve strength, facilitate cutting, and allow a hidden place to run electrical lines:

https://familygardentrains.com/primer/roadbed/ladder1.htm
https://familygardentrains.com/primer/roadbed/ladder2.htm
https://familygardentrains.com/primer/roadbed/ladder3.htm
https://familygardentrains.com/primer/roadbed/ladder4.htm

See the following video showing the great load bearing strength of one man’s post and ladder roadbed. Note the wide 4 to 6 ft. spacing of the support structures. The HDPE ladder roadbed between supports doesn’t even sag under the heavy weight train engine! Even so, a closer maximum spacing of 2 ft. would be much better. Also note the unsightly placement of the electrical conduit line tied to the bottom side of one of the stringers. A much better place to place the electrical lines is to hide them between the rails just under the ties in the small ¼” space above the stringer connector/spacer blocks in my design:

- YouTube

[John_Carmichael]

Hi Pete: Now I can answer your question.

TrexTrim is the material I used. It is PVC lumber but is very similar in all ways to HDPE lumber. It’s very flexible, but I don’t know if it is more or less flexible than HDPE. I bought this size: SKU: WW010618B. This measures: 3.4” thick x 5.50” wide x 18 ft. long (actual). It’s white with wood grains. I had the supplier rip each board into 1.75” strips for the stringers. Wider boards are available but all will need ripping. The supplier delivered the ripped strips to my home for a small fee. Website: Trex trim brochure - Trex Inc. - PDF Catalogs | Documentation | Brochures

[John_Carmichael]

HDPE (high-density polyethylene) roadbeds are made from very flexible high-density UV-treated PVC sold for house siding. UV-treated vinyl can also be used, but is less flexible. It’s available with faux wood grain and is ¾” thick. The lumber yard ripped many 18 ft. long 1 ½” wide strips for me. Two 18 ft. stringers screwed together back-to-back form an 18 ft. section of ladder roadbed by screwing 2 ¼” x 1 ¼” x 1 ¼”” composite wood spacers (we call them “brownies”) between the stringers every 6”. Its flexibility automatically forms perfect curves of the desired radii between any three points.

Before joining with brownies, a single stringer can be bent into almost any curve, even tight R3 radii. After joining, both stringers become rigid and hold the desired shape. Stringers are connected end-to-end with 8” long pieces of HDPE screwed to abutting stringers. Position and join all stringers on the ground, then raise the entire joined roadbed little by little to the correct heights indicated by SCARM. Temporary vertical posts support it every 6 feet. Now paint the roadbed. Sun eventually destroys plastics, even UV-protected ones. For extra protection and aesthetics, paint HDPE with primer and with two coats of desired color. After painting with Krylon flat dark brown spray paint for plastics, I removed the temporary vertical posts and replaced them with wood trestle bents using steel angle brackets. Then I bent the rails and attached the track. The roadbed is 3 ½” wide, matching LGB ties which are screwed to it. Use countersunk waterproof deck screws for the ladder brownies and joiners, and ¾” stainless steel tiny rounded screws for ties. Note: For strength, do not put stringer abutment joiners across from each other. Stagger them.