Hi there,

As I build my fleet, I have been using 2-56 screws directly into the bolster to mount trucks. Recently, on a RCW GN car I’m completing, I noticed that the pivot hole in the truck bolster is a fair amount larger in diameter than the screw. It seemed to me that a small sleeve around the screw might improve operation. A number of ideas came to mind. But I thought it would make sense to ask here - what is the preferred method other folks are using?

Rob

Rob,

Many brands of model freight trucks have a large kingpin screw hole that will accommodate a boss on the bolster that helps keep the truck centered and acts as a stop for the truck screw.  The boss prevents the truck screw from being tightened up to the point where the truck no longer pivots. 

For my freight cars without a boss, I cut the center pivot off a Kadee coupler pocket lid and slip it over the screw.  It can also be glued onto the bolster centered on the kingpin screw hole, with CA if the bolster is resin, or plastic cement, if it is styrene.  The Kadee center pivot becomes, in effect, a shot tube which fits over the 2-56 screw, and allows the screw to be tightened up without binding the truck.

I hope this makes sense.  I'd be interested in others' solutions to the problem.

Todd Sullivan

Robert there are washers made for the situation you have described.  I have attached a photo; however, I do not know the manufacturer.

Lester Breuer

I just recalled that one of the plastic parts sprues in Bowser kits has four (I think) of these 'tube washers'.  They also work, as I have used them in assembling many Bowser kits.

Todd Sullivan

Thanks everyone.  I do not have a stash of Kadee No5 boxes to scavenge from, so i’ll pick up some 1/8” evergreen tube and go with that idea.   Appreciate all the suggestions.  it was reassuring to know it is a “thing”.

I'm surprised no one has mentioned Proto:87 stores' washers. I've used them and they do seem better than the "one screw tight one looser" method. (Admittedly not answering Rob's direct question, but answering his more general one.)

Steve 

I am a fan of those washers too.  They are very thin, so not much impact on car/coupler height, but they do provide a (at least a chance to achieve a) 3 point suspension.  

Hi Hudson - the link you sent went to the microfasteners webpage, but not to any specific product.  Can you point us to the item you were flagging?

Coming in late... A little bit of background on why HO scale trucks have 1/8" holes in their bolsters:

In the beginning...  models had wood floors and wood screws were used to hold the trucks on. This was ideal because wood screws aren't threaded all the way to the head, and that left a smooth shank for the truck to pivot on. A No. 2 screw had a shank diameter of .086" and NMRA RP-23 specified a .089" hole in the bolster (#43 drill) to provide a running fit. Still, to this day.

But Mr. Athearn had a problem. He wanted to use a two piece plastic floor and underframe to trap his steel weight between, so he increased the hole in the truck bolster to a running fit on the 1/8" diameter boss he molded on his underframe, and had the screw that threaded into the floor tighten against this boss to hold the sandwich together. Other manufacturers saw the advantage of having the screw tighten against a boss, whether they needed it to hold the UF to the floor or not, and it became the defacto standard.

But some trucks remained that had the .089" hole, and resin manufacturers left the boss off to allow the use of these trucks... aside from the fact that the thin walled boss is hard to fill.

If you are dealing with Accurail trucks a 4-40 screw won't work, because the counterbore in the bolster is too small for the screw head; I specifically sized the counterbore  to be a running fit on the HEAD of a 2-56 pan head screw, but other brands of trucks are different, so check before you drill.

And, someone mentioned the Proto:87 Stores car stabilizers... These also have a clearance hole to accommodate the 1/8" boss.

Dennis Storzek

Just mentioning a good place for small screws and hardware.

-Hudson


Hi Hudson - the link you sent went to the microfasteners webpage, but not to any specific product.  Can you point us to the item you were flagging? Hide quoted text

 

My local hardware store sells thin plastic washers.  I don’t know what resin they are molded from, perhaps Delrin (?).  




--
Ted Larson
Trainweb.org/MHRR   ---   GN in 1965   ---   NASG.org 

Got it - thanks!

When I need a special size head on a truck screw I run a 2-56 nut tight against the screw head, chuck the screw in a Dremel tool or lathe, then file or machine the nut to the required diameter.

Mark