National B-1 Trucks
Proto:48 and 2-Rail Versions
The National Dual Control Truck
The National B-1 truck had a rate of 50 tons. This solid bearing truck has been designed for more reliability and lower maintainance costs by removing all unnecessary parts and surplus weight. Two main versions were produced, the premium “Dual Control” and the more standard “All Sprung”. The Drawings from the 1940 Car Builders’ Cyclopedia are the base for my design and I tried to follow it as closely as possible. Note that my version has Symigthon journal covers.
Materials Needed
8mm long set screws
M2 set screws with a lenght of 8mm. Those headless pins keep the side frames in place and allow for just enough play so the wheelsets can twist a little. The truck is self levelling and all wheels make perfect contact with the rails at any time.
sfr133zz ball bearings
These are my standard ball bearings that I use in almost all of my passenger and freight car trucks. It perfectly fits Protocraft wheelsets in P:48 and can be used with NWSL shouldered axles, as well. Good sources do change a lot so I can not give a recommendation of where to buy. It is a very common type and a set of 12 pieces should not cost more than $25.
4.8mm drill bit
I know you don’t want to hear about it, but folks! Go metric! That bit is the pefect reamer to make the ball bearings press fit into the side frames.
Assembly
The ball bearings have to be pressed into the side frames. To ease that procedure I strongly recommend to ream the sideframes with a 4.8mm drill bit. The brake shoes need no glue, they are kept in place with 1mm brass wire. Bend a slight curve and cut it as shown. Two on each side gently clamp the brake shoe in place.
The brass wire can be fixed in place with a drop of CA but I didn’t even do that because of a tight fit. The brake shoes fit tight but do not touch the wheels. Make sure to mask off the bearings when painting.
Insert the set screws through the sideframe slots into the truck bolster. You might need to clean the bolser’s screw hole a bit. The hole’s diameter is 1.4mm. Perfectionists use an M2 tap.
Files
Proto:48 for Protocraft Wheelsets
Files for a complete truck designed for Protocraft 33″ 50 ton ARA “D” rated, one wear thread wheels.
2-Rail for NWSL Shouldered Axles
Files for a complete truck using North West Short Line 33″ shouldered axle wheelsets, measurements 1/8″ x 1.810″ x 0.088″
2-Rail for Intermountain Axles
The popular pointed Intermountain metal wheelsets directly fit the sideframes. The resin is strong enough to withstand the friction of the pointed axle ends.
