Bachmann Adhesion (Steam profile)

Many model steam locos are poorly balanced, so that not all drivers provide the same adhesion. The C of G of a steam loco should be at the midpoint of the driving wheelbase. Pony and trailing tracks should be heavy enough to hold the track without having any loco weight on them, if at all possible. Unfortunately, because of motor location, etc, it's not always possible to achieve the best possible balancing, but you should be able to improve it, and hence improve pulling power. As to how to do this -- well, that depends. Sometimes it entails both removing weight from one end and adding it at the other. You'll have to figure it out for each loco, I'm afraid.
If there is room, you could try to add springing.
HTH

I don't know these models because I do 7mm scale, but is it possible that the tender engines have springs to hold the bogie down? These have to be adjusted perfectly, with only enough pressure to hold the wheels to the track. More than that and the spring will try to lift the driving wheels. It won't show but it will take weight away from where it is needed.
IMO weight in the bogies is better than springing and shouldn't make any noticeable difference to the hauling power.
On the real thing the bogie carries the weight of the front of the engine directly, by rubbing plates. It also has sprung side control that steers the rest of the engine into curves.
A lot of kits can be built that way - my DJB Dean Single does this: it is equalised between the driving and trailing axle so it pivots forward onto the bogie, which has a nice lost wax casting for the bolster that forms the rubbing plate and also slots for two springs for side control.

Bachmann, on the 4 wheel bogies use coil spring around the fixing/pivot bolt. These are not really adjustable. The 2 wheel pony trucks use a leaf spring. I did modify a Hornby Black 5 to the double sided power take up from the drivers and changed the tender drive wheels to 4 wheel drive. This gives a formidable traction but lacks the smooth action of the bachmann flywheel motors.

[...]> for side control. Cut out one or two coils of the spring. It may be possible to eliminate the sporing. Glue a chunk of lead on top of the bogie. You may also be able to wrap some solder round the bogie axles. Aim is to increase the weight enough so that you don't need a spring. BTW, make sure the bpogie wheels are RP25 or as near as possible. They track better.

Try removing the spring completely, and using a sticky glue that doesn't completely set. That way you won't have done anything irreversible until you are ready. I don't know if Evostick is still available over there, but that would set to a rubbery consistency that could be pulled off.

I know youve had excellent suggestions but before you modify the bogies .. May I suggest making sure the chassis is nicely lubricated and free running. If you were to modify the bogies then perhaps first you could try removing them completely and check its pulling power. Should tell you straight off if modification needed !
Cheers, Simon

Well if only Bachmann had placed coil springs into the bearing bushes (as some have, carried over from Mainline ) and continued with the driven " Driver" having a tyre! My mainline Manors run like a powerful scrapyard and equally an untyred Scot is a superb performer.
So why do the Patriots, Scots all run well and yet the Jubilee slips (they all have identical chassis and weigh in at 320 gms). I will remove the bogie from Courageous and see what transpires but i will invest in some more fishing weights as a back-up.
One of the S4 members made a bridge type weighing machine to remedy traction failures on sprung chassis but it required a lot more resources than I presently have. My calculations lead me to expect that a max towed load on a 1:40 will be 2.4 x Traction unit weight on 6 wheels. This is the criteria which my failures cannot match. It could of course be worth roughing up the surface of the steel track on the inclines (med. emery paper) as it is easy to replace a piece of track!
Regards
Peter A

Well the answers have fallen out by perseverence: The Jubilee has a Fowler tender which has less lateral clearance than the Stanier and Stanier wheels had been fitted! This caused poor rotation friction figures and cornering binding due to lack of lateral movement. The Hall , Manor and 53XX were all simply under weight so, smoke box and cab loads and under bottom frame plates have cured that problem. As an add-on, the steel rail on the gradients has been roughed up with emory paper. The smoke box loads have also steadied the front ends and the bogies are not dancing quite so much.