
The latest project to land on my workbench are some fully sprung bogies for a pair of Bachmann class 47s. I thought it might be of interest to some of you who might be thinking about dabbling in the dark arts of diesel suspension to see how I go about them on a step by step basis. Each of the bogies is basically an 0-6-0 steam loco chassis with guitar wire springs connecting the wheels through hornblocks to the chassis. To this will be added some secondary coil springs to connect the bogies to the locomotive. A bolster flange and recieving plate made of telesocping brass tubes will keep everything where it should be. The original drive train on the Bachamann locos will be recycled to provide the power to the wheels. At the moment I intend the drive arrangement to be of a B1-1B configuration though with a bit of extra work a C-C is very possible. Hopefully it will all look simpler than it sounds.
Before the construction can begin there's a bit of theory to contend with. For each type of bogie that I've built the first thing that I've done is draw up a 'Data Sheet' outlining the basic dimensions of the sideframes and the arrangement of the primary and secondary suspension. On previous bogies I've used 'centre load on beam with two simple supports' principal as described on CLAG's website http://www.clag.org.uk/beam.html. This envolved a lot of faff cutting, drilling and then fitting twelve spring supports made from brass L section for each bogie. I'm going to try the 'end load on cantilever beam with single fixed support' method to try and simplify things. The final make up of the secondary coil springs and connection to the body will involve a bit of trial and error with regard to the dimensions and set up. I don't possess the engineering prowess to get too technical about coil springs. Given the choice I'd prefer to use the wire beams but there isn't anywhere to hide them on these sorts of bogies so coils it will be. I suppose you could dispense with the secondary suspension but I haven't figured out a way of satisfactoraly transferring the weight of the loco to the bogies without it. Perhaps others will have better thoughts on the subject.
The ingredients:
An all wheel drive wibbly wobbly bannana bogied Bachmann Brush type 4 (they definately didn't have P4 conversion in mind when they designed this)
Heljan cosmetic sideframes (the Bachmann ones are a bit 'weedy')
3 (2.95 actual) x 1.5mm and 2.5 x 1.5mm brass L section for the primary spring supports
1mm brass rod to 'rivet' the primary spring supports to the sideframes
2 x 1mm brass flat for a hornguide setting jig
1/8", 3/32" square brass tube and 1/16" rod for the secondary spring arrangement
0.010" and 0.018" nickel silver sheet
28swg phb wire for the coil springs
Gibson P4 frame spacers
High Level 2mm hornblocks
0.011" Guitar wire for the primary springs
Ultrascale 3'9" diesel disc wheels
There's probably something I've forgotten about but that's pretty much it.
The first thing to do is the most tedious and certainly the hardest on piercing saw blades, namely cutting out the sideframes. Sometimes though there's nothing for it but to get your head down and get on with it. It doesn't take too long with something half decent on the radio or stereo. I cut a strip of 0.018" nickel silver 9.5mm wide then cut that into 82mm lengths which were then soldered double to form a pair of sideframes. If there's one thing worse than cutting out four lots of sideframes it's cutting out eight!

More soon.