Overpass

[MD-Z1Rider]

Daufderh,

I know this tread is a few months old, but just in case you are still looking for 3/8" MDF... I'm just over the river from you in Maryland and am also starting a routed track. I called Chesapeake Plywood in the Baltimore area. They are a distributor, but they referred me to a dealer in my area. E.F. Johnson lumber just south of Annapolis can get 3/8" MDF for you. It's around $85 a sheet. Depending upon where you're at in NoVA, that could be less than 1 hr drive. Chesapeake Plywood's website says they serve the MD/DC/VA area. You might be able to call and find a closer dealer as well. 84 lumber was another dealer they mentioned.

I've been experimenting with bending 1/2" MDF for banked curves and elevation changes. It can be done, but I'm still going to bite the bullet and buy the 3/8".

Part of my experiment has been using steam. I used a hand-held cloths steamer. My dad built wooden boats and steam boxes were standard practice for bending boards around around the bow. I know MDF isn't real wood and everyone will tell you water and MDF don't mix. It will swell and fall apart if gets wet. However, I used steam with no issues. I didn't soak the board, but the steam was enough to change the color to a darker brown. I also tried it on routed sections to make sure the outer layer wasn't acting as a protective barrier. I had no swelling issues. From some internet research, it appears the heat is a big factor with MDF. It softens the resins or glues which then form to the new shape when cooled. All I know is that it took much less force to bend with less creaks and snaps and seamed to hold the bend better when the force was released.

[HO RacePro]

There is a shop in Annapolis that will CNC rout and cut out track sections for you if you give them CAD drawings of what you want. They'll supply the MDF. I used them when I built my 1/32nd slot track.

Their name is Chesapeake Light Craft, 1805 George Ave, Annapolis, MD 21401, 410-267-0137. Yes, it costs more money, but they do all the awkward and messy stuff for you. They're good people.

Also, you don't need to heat or steam MDF to make banked corners. All you need to do is make the curve less than 180 degrees and pull it into a tighter radius. The MDF will naturally twist into a bank. It is easiest if you can include a bit of straight at each end of the curve -- like a letter 'U', except it will be more open at the top, a bit like a letter 'V'. How much less than 180 degrees? Try 178 or 176. You can work it out with math and geometry, but if you slept through those classes just make scale models out of poster board and experiment. A model really helps you visualize what you're planning.

You do not want to make too steep a bank. I don't recommend more than 20-degrees. Otherwise cars can slide down the banking going into or out of the curve.

Ed Bianchi

[daufderh]

I'm slowly but surely moving towards starting this build with a bridge. I'm pretty sure this is a dumb question but dumb questions are about all I have...

Routing a track with no bridge is relatively easy. You lay the wood down and route it as if its one large piece. You only have to be careful at the seams and such. Is there a trick to routing out a bridge section? Let's say I need a two foot long straight that is my bridge overpass. Do I just measure, cut, and pray? What's the best way to get the length such that it fits but there isn't a huge gap on one or both ends? Seems like it would be really hard to cut the length down so that it fits perfectly into the rest of the track. And if this piece carries the ramp up/down of the over pass, I assume it would need to be a fraction longer than the total distance to compensate for the up/down bend???

Thanks
Dave

[HO RacePro]

If you're making a two-foot long overpass the bridge section you need will not be much longer than that -- only a fraction of an inch longer. I'd say start with a 26" straight, lay it in position, mark it and cut to size. At the very worst you'll need to fill a small gap with Bondo. But really, you should be able to fit things up exact.

I recently built a routed 1/32nd track with an overpass. I closed up the gap in the main straight, not the overpass itself. But I used the method I just described to make up the difference and it came out perfect.

Stay calm. Take your time. Measure twice, cut once. You'll do fine.

[RichD]

If it was me I would cut a piece of cardboard to fit, then use that as a template for the MDF bridge section.

[Bluezephyr]

Haven't read through the whole post to see if you had routed your overpass track. But here is a pic of what I had made from 1 sheet 4x8 mdf.

[Bluezephyr]

Race ready. I used viper rail.

[Bluezephyr]

Used relief cuts in sheet. Overall size is 3'x7'. So I had 12" wide section to make the bridge. Tried to get some more pics to upload but for some reason they won't.