Rail Tie Fabrication
The rail tie to rail joint (RTJ) is the most critical area of the coaster. With this we will be paying special attention to all aspects of it. From selecting material to staining, we will do everything possible to make sure it is as strong as it can be.
Attaching the Rails to the Rail Ties
As we just saw, one critical joint is the rail to tie joint (RTJ). Since we are going to do this many many times, we need to be sure that we are doing this one right. Each joint needs 2 screws per side. They must be pre-drilled, countersunk and use the right length screws for maximum load bearing.
Joining Track Sections
Joining track sections is difficult because we need to bond on the inside surface of the pipe rather than the outside. With 1.5″ PVC pipe, this is even more difficult because the ID is 1.61″ and there is no standard size tubing or pipe that can fit in here. The best option is to get a 1.25″ Schedule 80 PVC pipe and turn the OD down to 1.60″. This will get rather pricey unless you have your own lathe.
As a result, we will take 1.25″ sch 40 PVC pipe and make it a smaller diameter by cutting out a strip of it along the length so that it can squeeze into the rail pipe. It will then be secured with glue and screws.
After this pipe didn’t hold with glue alone, I skipped gluing all together. I added 4 screws on each joint, (2 on each side of joint) to secure the track pieces. I also switched to the #10 2.5″ long screws but plan to replace them with something shorter in the near future.
I speculate that the reason PVC pipe joins with glue so well is that normally there is no slit in either piece. In normal functions, the glue needs to resist a pure twisting or a pulling force. With the slit, the joiner doesn’t work together so a twisting motion does not evenly load the glue and shears off. This will be a subject of more investigation in the future.
Upon disassembling the Black Widow, I discovered that the joints take a longer time to cure. I now recommend using glue and screwing for a strong, long lasting joint. (01/12/23)