Large Scale Central

Improving performance of Bachmann Pilot Wheels

Modeling Rolling stock
#1

When running the Bachmann Outside Frame 2-8-0 or K27 on Aristo-Craft track, derailments of the pilot wheels often occur. When I worked with Bachmann on the C-19 we spend a good deal of time on the pilot to ensure the Pilot stayed on the track. I have now gone back to the outside frame 2-8-0 and K27 to see of some of the same techniques worked. There is often a poor transition from the rail to the frog of these turnouts or a bump at the points and the pilots pick these areas and often derail. Other places where pilot derailment occurs is when the track is not level. Two improvements were applied to the older models and in operations they seem to work well. Today the only pilot derailments we had on either model were due to Acorns and I am not sure there is any solution to thest. Improvement 1: the vertical side to side play on both these models is a little restricted. by rounding the mating surfaces you can increase the freedom of movement. Improvement 2: Bachmann has improved their flange over the years. I took the older pilot wheel and increased the angle of the flange in a grinder followed by smoothing with a file. Perhaps someone else could try to duplicate this and see if they obtain the same results. One caution grinding a wheel is a one way process so some care must be applied. In the below photo the origional wheel is on the left and the reprofiled wheel is on the right. Stan Ames

#2

Solution to Acorns…Squirrelguns!!!

#3

I would submit that the problem is that the old flange was so thick that it was impossible to meet NMRA targets for BOTH wheel gage and back to back… like Aristo wheels.

That’s why I think what you did works, because the contour is all wrong, from a historical modelling and prototype point of view.

You said vertical side to side… but vertical is up and down, so I’m not sure what you were saying… it seems that you meant horizontal, which would match with side to side, and also not having enough side to side would be typical with overly thick flanges… like the Aristo Consolidation that literally walks up out of the rails…

Greg

#4

Greg

You are absolutely correct that Check guage is critical. However in ths case I am not altering Check guage. Check gauge for the wheel is remaining the same.

For communication purposes if you look at

http://www.nmra.org/standards/sandrp/pdf/RP-25%202009.07.pdf

The check guage is from the back of one wheel to the intercection of R1 and R2.

For Large Scale wheels with deeper flanges, there is a flat area between R1 and R2 that is at an angle. I am reducing the steepness of the angle making the tip of the flange less as a result. The result is that the tip of the flange is further away from the rail and thus does not hit the areas of the track that stick out more then they should.

I think what I need to do is draw it out as I am not sure words are communicating this correctly.

Stan

#5

Yes please Stan, I do want to understand what problem you solved.

When you talked about the “vertical side to side” you lost me.

Also, if the check gage was ok, then I don’t see the reason for the radical change in the contour, and so far away from the proven contours.

Looking forward to more details, since it seemed to have solved your problem.

Thanks, Greg

#6

I had a similar problem with the pilot truck of an LGB mogul. It would just walk up and over the rails. The wheels were in spec for b-t-b and check gauge. What was happening there was that the pilot truck arm on the mogul is so short that the axle was riding significantly less-than-perpendicular to the rails as the loco rounded a curve (my minimums are 5’ radius–certainly not sharp). That skew was enough–given the steep flange walls of the LGB pilot wheel–to where the tip of the flange was rubbing the railhead. I replaced the pilot wheel with a new one with a shallower angle from the tip of flange to the tread. Now–even with the axle askew, the tip of the flange is kept away from the railhead. Problem solved. Here’s a drawing illustrating the changes in my situation:

(http://1stclass.mylargescale.com/eastbroadtop/misc/FlangeAngle.jpg)

It’s pretty much the same in Stan’s situation, though the wheel is more perpendicular to the rail and you’re just leaving more room for points or frogs that are uneven with the side of the rail:

(http://1stclass.mylargescale.com/eastbroadtop/misc/FlangeAngle2.jpg)

One suggestion, though; if you can chuck the wheel in a drill press, it makes it much easier to re-profile the flange. Later, K

#7

Kevin: Yep, I saw the wheels yesterday and thats exactly what Stan did with them, just shape the flange to have more of an angle. Seemed to work.

#8

I understood exactly what Stan was eluding to based on the photos. The pretty clearly show an increased radius at the point where the flange meets the tread and the angle is significantly steeper, narrowing the rim or the flange. A drill press might work, but a lathe would work better. And the best scenario might be for Bachmann to offer them as replacements (free would be asking too much).

Bob C.

#9

Looks like I have to do something with my K. I have the same problem of the front truck derailing. I was trying to blame it on my trackwork and work diligently to try to fix that. I had gone through all my track and releveled and checked switches and I still was getting a derailment. Now I see it might have been the wheel.

I dont have a lathe, so I think I might have to try Kevin’s suggestion with the drill press.

#10

Another of my ‘round to it projects’ was to replace the stock spring on the pony truck with a spring of about 1.5 times spring rate to see if that would improve the tracking, but this looks like an easier answer.

I wonder what Rodney would charge to do a set up and machine a bunch of them if we were to send in a number at a time?

Bob C.

#11

Bob, if you remove the spring and stretch it out a bit, that will help in the downward pressure department. I also shimmed the underside of the pilot deck where the plunger rubs with some .050" styrene. That really helped in terms of the pilot pushing its way through the spring switches on my reverse loops. The pilot on my K still doesn’t like one switch on the track out at the Colo RR Museum, so I may have to look at trying this as well to see if that helps things.

Later,

K

#12

I’ve had good luck by substituting Sierra Valley Wheels in my BBT pilot.

#13

Kevin

Thanks for posting the excellent diagrams. That’s exactly what I had done.

There is really nothing wrong with the older pilots, this really is a track issue. On my railroad I have a ton of turnouts which I have not brought up to spec and my trackwork is not always level. While improving the track is the long term goal, one can also attack the problem by making the wheels less prone to pick up track problems.

On the prototype the pilot truck has an important purpose of guiding the boiler and frame around curves and distributing the weight of the boiler. On the model the pilot truck has no functional purpose and is simply pushed around the railroad.

Kevin has shown in his post how increasing the angle of the flange will help keep the tip of the flange away from the rail.

Equally important is the free play of the pilot truck. If the track is level you only need a small amount of play but if you have a lot of twisting in your track the locomotive body will rock and quite literly pick the pilot off the track.

On the C-19 the pilot is very flexible and sits on a bowl shape washer to allow maximum free movement. I posted a short youtube video of this movement. (Sorry I do not know how to embed this)

http://www.youtube.com/watch?v=R6uSFY0UvUA&feature=plcp

While it is difficult to get this amount of free movement on older models, it is possible to significantly increase the side to side movement by filling the top and bottom of where the pilot attaches to the locomotive both on the locomotive and on the pilot to allow more free play. This also helps keep the pilot on the track.

Stan

#14
Quote:
if you can chuck the wheel in a drill press, it makes it much easier to re-profile the flange
Quote:
One caution grinding a wheel is a one way process so some care must be applied.
As Stan points out - there is no going back if you go too far! OK if you have a few spare wheels - but I don't know how you get both wheels perfectly the same. I would consider swapping them - I got some for my C-16 pilot from Gary Watkins with one wheel pressed on and the other for me to fit when it was installed.

I believe the wheel guys have a lathe tool already shaped to the profile they want. You might want to make up a brass or styrene profile master before you start filing!

#15

Stan,

I have a solution which is in two parts, the first is an arm which replaces the “crescent-shaped” guide in the steam chest saddle, (Bachmann just incorporated it in the new Annie). The second part is an aluminum frame which flexes, allowing the wheels to guide themselves. Have several hundred out in service, with no complaints. Bachmann has not found this usable, yet. If you would like one, let me know.

Barry