Bachmann Northern 4-8-4 3783 (#58152) - CONTINUED

[grahament]

I thought I would start a new thread since I believe that I have found something rather important. My loco is very sporadic, one day its OK then a few days later it runs really erratically. Today it ran very badly I so I took it apart and cleaned the axles and axle sockets for the 1000th time it seems. Just for the heck of it I put it together with the 2nd from the front wheel set missing. This wheel set comes out easily and is not connected to any of the con rods. It also has the traction tyres on it. It ran SUPERBLY with that pair of wheels missing, smooth as silk, never faltered, even when run very slowly. It never hesitated even on the points. I have never seen it run this well. I had it running all day like this. I put back the wheel set and it ran erratically and jerky all over again.

So it appears that there are other reasons for very poor performance on this loco other than poor pickup. This wheel set has a gear wheel in the center and connects together two other gear wheels on this loco. Its almost as if connecting together these two gears binds and ceases the motion now and then. I now need to get it running this well with that wheel set back in the chassis. Anyone else see anything like this?

[grahament]

Correction - its the 3rd set back from the front:

http://www.bachmanntrains.com/home-usa/dwg/dwgs/58052.pdf

Remove the back boggies and the small Philips head screw on the plastic gear cover. Once removed the wheels and gears are exposed. The 3rd set back from the front lift off....they are just set in there and not connected to anything unlike all the others.

[skipgear]

That is because the traction tire makes the driver slightly larger in diameter than the other wheels to insure that it makes good contact for pulling power. This lifts the other drivers off of the rails and they don't contact the track as well and as a result you see weak electrical performance.

It can be solved by moving the traction tired driver to the #4 (rear most) location. This allows the weight of the loco to ballance between the front axle and the rear axle, improving pickup on the front axle and others. It also as a side benefit gives the loco much more pulling power. The only issue is when you start getting into long trains, it will cause the loco to nose and lift the front drivers up and over the rail on tighter radius corners.

[grahament]

Thanks for you insight "skipgear"...I'm sure you are right 

[grahament]

Skipgear: To prove your point I took off the traction tyres and put the wheels back on..she's still running perfectly...no jerk, no erratic and no hestitation over the points as before. As I type she's pulling my longest train with 17 goods wagons..and no wheel slip. I will leave the traction tyres in my spare parts box

THANK YOU!   ..you're a life saver....I have fought with this thing for way too long....now its better than ever...

[skipgear]

Adding tender pickup will solve your problems also and make a better all around running loco. Look up Richmond Controls for a conversion kit or there a few tutorials on how to make your own floating around the web. It is mandatory that any one that I add DCC to get tender pickups.

[grahament]

Agreed - however it does appear to me that the traction tyres are really not doing a whole lot if they a) lift the other wheels up so that the electrical contact is poor since b) this will also decrease the traction from the other wheels too. It appears that they are really defeating the purpose.

[Desertdweller]

Tender pickup is easy to add.  I used the lighting pickup wipers from an old Bachmann 60' heavyweight passenger car.

Make sure your insulated tender wheels are on opposite sides.

I used very light wire, and soldered the wires directly to the brass brush contacts on the motor.

Now, if I can only get the lead truck to stay on the track......

Les

[skipgear]

Agreed - however it does appear to me that the traction tyres are really not doing a whole lot if they a) lift the other wheels up so that the electrical contact is poor since b) this will also decrease the traction from the other wheels too. It appears that they are really defeating the purpose.

If you have electrical pickup, all that matters is that the traction tired drivers contact the rails. The other drivers are just along for the ride at that point. They are not adding to the tractive effort one bit as long as the traction tired driver is doing its job.

Look at the Kato GS4, the only geared driver is the traction tired driver. The rear driver is spring just to maintain ballance of the loco and the front drivers are along for the ride.