Spectrum 2-6-0 center driver dropping off rails with guide pins removed

[MarkP]

Forum Members and Bach-man.  Does Bachmann have a recommendation for alleviating a problem I am having with my Spectrum 2-6-0 Mogul center flangeless driver dropping off the rails creating a wobble which I am sure creates extra stress on the drive line.  I had to remove the guide pin assembly from the frame between the center driver because the locomotive would hang up and stop when going through diverging paths on switches and would also jump going through the straight path of the switches (switches are USAT solid brass).  So now removing the pin assembly has created the situation where the flangeless center driver drops off the inside rail going around curves.  (even 20' diameter curves). 

Would fabricating and installing a plate the same size as the original plate removed - but without the two pins, resolve this issue, or do I need to shim the axles with nylon washers to take up the slack, or is there a better solution to this problem?  Other than this center driver issue, the locomotive is tracking and running great on the USAT track and switches (8' to 20' dia switches and curves). Any advise is appreciated.  Thanks!
Mark 

[Loco Bill Canelos]

Hi Mark,

I noticed that you had no answers to your query. I have no idea why your 2-6-0 is derailing.  Mine, without the pins , runs on a mix of track brands, and most of my switches are Aristocraft.  I have had no problem similar to what you describe.  It does make me wonder why the flangless drivers drop off. As I said I have no problem, but why you are is hard to explain.  I have read over your post several times and can only come up with the following:

1. Is it possible the center drivers are in some way out of gauge, or are the flanged wheels slightly out of guage? Loose??  Doubtful, but worth a check.  Do you have any other Bachmann locos with the pins removed, and do they also drop off the inside rail?  If they do not, try to compare what is happening by running the locos around your tightest curves at the slowest possible speed and observe any differences, and see if corrections can be made. 

2. The only other solution I can think of is to reinstall the pins, and run the loco dead slow and observe what happens when it hangs up. See if the pins hang too low. If so you might consider carefully filing them down a little.  Are they too fat??  Again consider thinning them down a little with careful filing.

This problem is extremely hard to diagnose with out observing what is happening.

I wish I could be of more help, but right now the above are the only things I can come up with.


Loco Bill

[Greg Elmassian]

I agree with Loco Bill, I'm befuddled too.

Also, check your track gauge. Having a driver drop inside the rail on a 20' curve makes no sense.

My first instinct would indeed be gauge of the drivers.

So please report back driver gauge (all of them) just inside the fillet (the transition area between the flange and the tread), and the track gauge, through your switches.

Something does not make sense yet.

Greg

[Kevin Strong]

If you pull the retaining pins, you have to restrict the lateral play of the center axle. Insert 1/16" (ish) spacers between the bearing block and the eccentric cranks on both sides to keep the center driver from moving side to side within the frame. That will keep the blind drivers in contact with the rails on curves as tight as 5' radius. Somewhere on the interwebs I have a photo of this, but darned if I can find it right now. I used slivers of (I think) 1/2" diameter Evergreen plastic tubing.

Later,

K

[Hunt]

If you pull the retaining pins, you have to restrict the lateral play of the center axle. Insert 1/16" (ish) spacers between the bearing block and the eccentric cranks on both sides to keep the center driver from moving side to side within the frame. That will keep the blind drivers in contact with the rails on curves as tight as 5' radius. Somewhere on the interwebs I have a photo of this, but darned if I can find it right now. I used slivers of (I think) 1/2" diameter Evergreen plastic tubing.

Later,

K

K,

This contains the photo you cannot find? -- Click Here

[Greg Elmassian]

I think you can also take some nylon washers, take a small notch out just enough to snap over the axle but not so much as to allow it to come off.

[Joe Zullo]

[MarkP]

Thanks for the input and ideas to resolve this issue guys.  I have not had a chance to try adding spacers/washers to the center driver yet, but hope to get to it tomorrow or sometime this week.  I will update you all on how it goes.

Mark

[MarkP]

Update: 

Bachmann Forum friends, when I flipped the locomotive over and examined the blind driver set, I found one of the screws under the wheel center cap had backed out of the end of the axle.  So the only thing holding the wheel on was the side drive rods which have a huge amount of side play slack in them (like about 3/16" +/-).  So that was why the center blind drivers were not staying on the rails.  After I reset the wheel on the axle and re-installed the axle end screw (now with green loctite applied to both sides), I still noticed there was enough side play in the center driver assembly as to allow the wheels to drop off the rails. So after determining the diameter of the axle, I acquired some slick thin nylon washers from the hardware store (appr. 3/64" thick - a little less than 1/16" thick - each washer) with the correct center hole diameter, and installed one washer on each end of the axle between the valve gear eccentrics and the side frames.  I did the trick of cutting out about a 1/8" piece out of the washers (creating sort of like a piston ring gap), then I could pop them onto the axle with needle nose pliers without removing the drivers from the frame.  This took about half of the side play out of the center driver set.  When I laid a piece of 8' diameter curve on top of the end drivers with flanges, and played with the side play of the center driver.  I could see that there was still a likelihood of the center driver dropping off one rail on the 8' radius curve (it would track the 20' diameter curves fine).  So I added one more nylon washer on each side and it took out the rest of the side play.  Another test with the 8' dia. curved track and this time the center driver stayed on top of both rails.  So I lubricated everything per Bachmann lube recommendations and lubed the new nylon washer spacers as well and test run the locomotive.  So far it appears this has remedied the problem.  I will know more after making more lengthy runs on the outdoor layout, but so far, so good.  Thank again to all for your consult on this little problem.
Mark