Hi Colin, your question has prompted a first post from me on this forum. I've made three of Fred's diesel kits, and I'm a big fan of the ABC Diesel Bogie Gearbox, which I've used in all of them, and they save a lot of hassle meshing worm and gears. Brian Clapperton is very helpful advising on gear ratios depending on how you're proposing to run it, e.g. shed scene or garden railway, but he does get quite busy with orders.
Delrin chains are a fiddle to assemble on the axles with the motor as well, and really need a tapered pin (like those from Mark Wood) drilled through the axle to secure the sprockets. Lead weight also helps with traction, but it partly depends what you want the loco to pull. If you are doing a shed scene or a yard with just a few wagons, you can get away without a Delrin, but even here, I would advise some added lead for adhesion. If you can't fit this onto the bogies, it's best placed around the bogie pivot on the chassis above both powered and unpowered bogies. With enough weight, you should only need one motor as they are very powerful.
I want my locos to pull trains so two have a Delrin, and one of these has added lead, the other has very chunky cast white metal bogie frames which serve the same purpose. Both have only one motor. The third loco is a D600 with A-1-A wheel arrangement which doesn't suit a chain because the middle wheel is a smaller diameter. I also didn't like the idea of the chain being visible, so on this loco I have the extravagance of two DBGs, no Delrin, but an awful lot of liquid lead contained in boxes on the chassis, which means it pulls well.
So in summary, if Delrin really isn't for you, I would say definitely use lead, try one DBG or other motor of choice, and if it doesn't pull what you want, you may need to add a second to the other bogie.
I hope that helps.
Andrew
