Bachmann Class 40 running quality issue

[Waverley81]

I've recently been track laying on my layout and I've built a 4' round spiral of track to gain height at the end of a straight which will send trains back around the layout at a much higher level. All my other models have been tested successfully on the 'spiral' but when I came to test the Bachmann 40s that I have they appear to have difficulty negotiating the curves without derailing. There's no consistency over which wheel comes off, it can be any of the 3 main wheels, driven or non-driven but it is rarely the pony truck. There are 2 tracks on the spiral, the inner having the tighter radius and this is made up of standard peco curves (8 to a complete circle) The locos seem apt to derail on the outer as well which is obviously a less severe radius. The incline is modest with only two complete circles used to gain 18cm. My old Lima 40s are fine and no other chasis present the same problem. Any thoughts gratefully received.

[Dan Griffin]

i have this issue with a couple of mine, especially the split box one. there appears to be not alot of play for the drive wheels upwards or sideways, unlike the pony truck, and mine derail sometimes, not always at the same point on the layout but it is always the drive wheels. the slightest uneveness will throw them off. try removing the bottom of the bogie plate and clean away any overspill grease and crud away from the wheel arches/axel runs and see if that helps.

 

Bachmann forties will go around 1st radiuse curves without derailing (i test all my locos to see what their limits are), but they sometimes derail on the fourth rad curves on my layout, but by keeping regular checks on the bogie wheels, and runs inside the casing every couple of months or so has helped alot. so give them an exam every so often just like the real thing!!

[Waverley81]

Thanks for that Dan. I had come to the conclusion, after many observations, that there was perhaps limited articulation in the wheel sets and I wondered whether anyone had tried to file away some of the inner bogie to allow the wheels a greater range of movement? I'm not convinced it will help but I might give it a go because it's limiting what I can do with these locos at the moment.

[34theletterbetweenB&D]

The track on the spiral inevitably has a 'wind' on it ( on straight track this would be clearly visible as a twist) and the chassis as a whole may be just a little too rigid to cope. Can both bogies roll (rock side to side) relative to the body? If not slacken off the bogie securing screw a half turn at a time until the chassis becomes flexible enough. I doubt it is lack flexibility in the bogie wheelbase, since these will negotiate first radius on the flat, and the inside (undriven) axle of each bogie is sprung, with quite significant travel.

[Platform 6]

Maybe a search on the Bachmann class 47 problem re. pivoting on the centre axle will help? Solutions used on that issue may be relevant (and as per Dan's comments). The added off-centre weight at the front of the class 40 bogie could possibly exacerbate such a problem (or lack of weight - if a pony wheel tries to ride above the outer rail).

 

Just a thought to ponder as requested. ? I'd be interested to know if you solve this - my 'Big Ds' have only met a rolling road yet? 

 

 

[34theletterbetweenB&D]

Further thought on this. Unclip the bogie frames and remove the carrying wheels fore and aft so that only the powered wheels are left, and test it as a Bo-Bo to see whether it is a fundamental limitation with the powered wheelbase.

 

 

[Waverley81]

Further thought on this. Unclip the bogie frames and remove the carrying wheels fore and aft so that only the powered wheels are left, and test it as a Bo-Bo to see whether it is a fundamental limitation with the powered wheelbase.

 

 

 

 

Interesting thought. I'll give that a go this weekend. Cheers

[sulzer27jd]

Maybe obvious but have you checked the back to back gauge. I had problems with mine and when I sorted the gauge problems i was left with poor running on DCC. My track in the problem area is curved and banked. I found adding extra pick-ups worked really well and have done this to the three class 40's I run.

 

 

 

 

hope you get it sorted.

 

john

[37114]

Having had similar problem with a Bachmann 40 I would definitely do as suggested and slacken off the screws that hold the bogie pivot, and have also done the extra pick up mod above, I also lowered the body by trimming down the bogie pivots. It is now one of the best running locos in the fleet.

[Mallard60022]

I've just found this and wonder if my 'problem' might be similar?

I've rewheeled a Baccy 40 with EM Ultrascales (normally excellent running follows such a conversion) and am having problems with the trailing axles (the inner wheel-set). They are derailing as the loco moves forwards (thus this axle is the 4th set of wheels to get to the 'point of derailment) on track-work that other loco's negotiate well. These inner axles pivot and seem very lightweight; could that be the problem?

Any suggestions as to how to investigate/test/ cure this would be most welcome as this is a great looking DCC Sound machine that I would like running sweetly by mid November.

P @ 36E

[34theletterbetweenB&D]

Check they are not fouling on the loco underside, especially if the model has been lowered for a scale ride height. There may even be witness marks on the underside showing contact to indicate exactly where the problem is. The plastic undertray bottom surface on several of my Bach diesels are not planes, I have had to cut 'wheel arches' in some following cutting down the ride height, to allow the bogie to swivel freely.