Steph, forgot about the darn cooler group! You might get a cardan shaft under that but it'd be tight and would need a low slim tower, probably bespoke.
Pitch centres, yes that's what I meant LOL, been a long week already!
Decoders, perhaps I'm being dumb here but why two decoders for four motors? I'm presuming current draw, but four small motors would only be the same as one big motor surely and if all four are connected to individual axles it'll be a hard task for one to draw excessive current or to overload the decoder surely? I havent fired up my DCC set up yet but seem to recall track supply is AC and thus supply to motor must be choppered DC, that being the case it must be possible for the output from the decoder to drive a power circuit that directly feeds the motors and obviates high current draw on the decoder, failing that it shouldn't be too hard to break out the power transistors on the decoder to more meatier ones. As I say not fired up my DCC so could all be a crock of
but I work with crane control power transistors (all be it a bit bigger at 1600A) so I should be able to work something out.....just not right now as utterly brain dead LOL Needless it could be an option to explore, which I do intend to when I get down that road I.E. increasing the current capability of a DCC decoder.
Still, back on track, I'll have to dig my class 60 kit out but I am guessing that if it follows the 57 and 56 then middle and outer axles are compensated and float vertically which all but eliminates cardan shafts and multiple worm sets, unless there were UJs in there but that just mounts up the complexity 10 fold.
The only other option and probably the one I'd favour is a large single motor in the fuel tank area but half buried in the floor so the drive shafts are close to the underside of the floor and via UJs drive a worm gear box on the middle axle (minimise UJ angles) and thus from there Delrin to the inner and/or outer axles, more like a pseudo Warship or V160 drive layout as opposed to a Western/ V200 drive layout. Failing that a tower where the fuel tank is and the motor within the body (pure V90 & V160 drive arrangement) and that'd allow for a big flywheel too....but it does eat into the speaker cavity. Drive shafts, worm drives, towers and UJs do all mount up the friction but it would allow for a big motor in there which would help overcome some of those forces and the bigger the motor the less current it would draw....in theory!
Slaters do a
tower and a enclosed axle worm drive FD01
https://slatersplastikard.com/assets/pdfs/MotorGearboxFlyer.pdf , looks like the tower has been removed, though it would not be hard to make up a simple pair of plates with corresponding gears in to make an input/output shaft aligned tower gear box. Or even use delrin chain set up to transfer the drive below the floor. I can see UJs on the Slaters list as well.
I seem to recall that the FD01 will just fit into the bogie without protruding through the top but have a niggle that I might have been considering a small hole and a raised bogie pivot point by a few mm with the corresponding reduction above to maintain correct body height.
It does really depend on what sort of grunt you want, if it's to haul along all those steel slab trains we spoke about then your going to need some serious HP LOL, but if for a shunty plank then you'd probably get away with just one motor on one or two axles.
Option 5 is intriguing, one presumes the motor shaft is parallel to the bogie axles, that may well work quite well if you could ensure that the chain does no slip, your only issue there is finding a way to match the small motor shaft with the larger Delrin cog bores but I like the train of thought.
