I've converted three older MTH center beam cars from hi-rail to 2-rail, partly because the original truck locations on the cars were incorrect, partly because I'm a not-so-closeted 2-railer running at a 3-rail club. The conversion technique I used was a combination of how Brian Biggs converted early MTH auto racks, Dave Branum's conversion article from O Scale News several years ago, and a tweak I did to better support the trucks.
First, the photos:
Burlington Northern car before conversion. I had dumped the original loads in favor of some wood lumber loads I picked up off eBay. About 30 seconds after I had the loads in I knew I had to convert it -- those trucks just looked WRONG where they were mounted. The newer hi-rail cars have the trucks in the right place, but they haven't released a lot of them. The older ones show up periodically on eBay, which is where I got the UP cars. The Burlington Northern and the Tobacco Railway are "opera window" Center Beam cars (which is why there are only two rows of loads). The opera window cars are hard to find.
UP Car post-conversion. I took the weight from the second car (identical number) and added it to this car so I could run it empty.
The cars in a scale-wheeled consist on the club layout.
Loaded UP car.
The technique is actually pretty simple.
- Remove the screws holding the underframe detail on the car.
- Cut the underframe at the center sill edge of the bolster. (For the newer cars, they properly located the trucks, so you just need to remove the trucks and replace them with the MTH 2-rail trucks and mount the Kadee couplers and you're done.)
- Cut approximately 1 1/8 (as I recall) of frame away. from each end of the under frame center section.
- Cement the bolster to the underside of the car body with the ends aligned with the jack pads on the body (correct location).
- Cut a 1/4" piece of 3/8" wood dowel and cement it into the truck mounting hole on the bolster. Your Weaver truck will screw into this.
- Glue three 3/8" washers to each bolster around the dowel This supports the truck cross beam and keeps the car level. It's invisible (you can paint it black to be more invisible).
- Notch the end sill "bump" where the coupler draft box should be to accommodate the Kadee draft box. I used a razor saw to make two small cuts down the sill, then an X-Acto to score and snap the horizontal cut at the bottom of the body.
- Drill 1/16" holes to mount the Kadees. I used a small shim to level the couplers.
- I used Weaver Plastic trucks with 33" Intermountain metal wheels and the coupler heights were right on target.
Here's a close-up of the bolsters. I made the ones for the BN car. I got lazy (or smart) and cut off and reused the MTH bolsters with a small dowel inserted for the UP cars. With the washers installed, it supports the trucks well. The cars ride nicely and track well.
To convert an older MTH Auto Rack, you use exactly the same technique -- i.e., cutting out part of the chassis and putting in bolsters. I opted to re-use the MTH parts and wood dowels as it took less time. I actually made bolsters for the Burlington Northern car.
Weight wise, the loaded cars are a bit heavy at roughly 27 ounces because of the loads, but they track well in a train. My understanding is that technically I should have used 36" wheels but in this configuration, the cars are more tolerant of the uneven spots on the club layout. The new wheelbase will allow the cars to handle 36" radius curves (O-72 in hi-rail speak). I'm going to do a conversion on several older MTH Auto Racks I have in my collection.
Hope this helps. If you need some detail photos, I'll take one of the cars apart and get some more photos.