Steam Loco Drivetrain

[SD100]

I might be over thinking this but i wanted to see if anyone else had any ideas. Normally I'd have a standard steam loco with one driven axle and rely on the siderods to power the other axles, but I'm thinking it might be better to put some gears in to power both the rear and front axles, as there is usually a fair amount of slop in the siderods, and I'm starting to think that slop may be detrimental. Obviously the gears may have some slop too but I'm thinking it will be less. What are your thoughts or solutions?

SD

[Commander Wolf]

Always depends on implementation, but I think in general cranks should be fine. I have at least one fairly heavy duty engine with one powered axle and the rest cranked, and I have not had any problem with the cranks. 

[coaster]

I prefer connecting the first and last set of drivers via internal gearing.  Probably increases rolling resistance, but it ensures the drivers don't get out of sync.  The connecting rods are purely decorative.

[SteamSewnEmpire]

I try to power 2 axles on any 6-driver loco, with the rods powering the third.

Generally speaking, I always aim to keep the number of unpowered axles at no greater than 1.

[supertruper1988]

I drive all the flanged drive axles. the rods only serve to move the blind drivers. 

[zephyr1934]

The key thing in either case is to only put traction bands on the powered axles. In which case you could do either.

My hunch is that it would be best to have one powered axle for a small locomotive on R40 curves (to reduce the resistance due to the large relative difference in the radii of the two rails). For larger locomotives or heavier trains you might need more powered axles, but you can tell if that is the case if you find your wheels slipping, in which case having additional wheels with traction bands (connected by hidden gears) would increase your friction with the rails. On the other hand, if the motor is struggling to move the train you probably need more motors or fewer cars. Meanwhile, the larger the radius curve you have, the smaller the relative difference between the radii of the two rails, and thus, less resistance from the wheels on opposite sides of the locomotive fighting each other, thereby reducing any negative impacts of having multiple powered axles on the curves.

Ultimately though, if you are happy with how a locomotive performs that is all you need, i.e., no point in redesigning an existing engine unless it has problems running. Whereas for a new build, it can be fun exploring new techniques.

[Glenn Holland]

I have had success with powering only one blind axle and using traction tires on the flanged wheels. The connecting rods keep everything in sync.

[Paperinik77pk]

2 hours ago, Glenn Holland said:

I have had success with powering only one blind axle and using traction tires on the flanged wheels. The connecting rods keep everything in sync.

It worked also for me - one driven axle (blind, flanged, whatever it is) and then connecting rods at 90°, never had a problem.

[Cale]

I have never powered more than one axle on a steam locomotive, always relying on the rods to do the job they were intended for, transmitting power to all axles. I've never had an issue with this. I firmly believe that the less gears you can have in a transmission the better. Every gear introduces more friction.

 

Cale