I would like to get opinions from this group on what do you think is
the optimum HO truck bolster clearance hole for mounting the truck to
the car.

NMRA's RP-23 calls for a .089 diameter hole to clear #2 screws. Only a
few manufacturers follow this. Most have a hole larger than 1/8 inch.

It seems to me that the smaller hole would be best for resin kits. But
would it also be OK for plastic cars?

Tahoe Model Works currently has a clearance hole about .120" diameter.
Has anyone been happy with it? I'm willing to change it.

Brian Leppert
Tahoe Model Works
Carson City, NV

I'm fine with RP-23; the closer it matches the outside diameter of #2 threads the better. I
am concerned, however with the diameter of the "socket" for the screw head. Used to be,
the binder head screws I used fit just about every truck, now I'm being forced to buy round
head screws to fit. Since I bought about 4 pounds worth of #2 X 3/16" binder head screws
from a surplus outlet, you can see I have a vested interest in using them.

The binder head style has a much lower profile than round head, making them especially
useful in Kadee installation.

Brian Ehni

Brian:
The 2-56 screws I use to hold your Dalman trucks are doing just fine, so I
am happy with your trucks as is. Any thought to doing an ASF A-3 Ride
control. Kto's is ok, but I'd like to be able to get them without wheelsets.

Brian Carlson

I think a bolster that fits a pan-head 2-56 (e.g. Athearn) is just fine.
That is the size hole that I drill and tap for my resin cars.

Brian,



I would like to see the hole slightly larger. I, like many others who build resin kits, cut the "boss' off the bottom of the Kadee coupler box lid and use it as the swivel for the trucks. Right now I have to ream the hole in your trucks to make this arrangement work.

Not a big deal, but a slightly larger hole would make things a little easier.

Paul Lyons
Laguna Niguel, CA

Hello Brian,

I use more of your trucks on re-modeled Athearn cabooses than on anything else, and I
generally leave the truck-mounting boss on their underframes. That means the larger
kingpin hole has worked out just fine. Where I've used your Dalmann trucks on resin cars, I've
bushed the kingpin screws with short pieces of styrene tube.

It wouldn't bother me, though, if you adopted the .089" hole recommended in the NMRA's
RP-23. It's not that big a deal to slice off Athearn's plastic boss (and I already have more of
your caboose trucks than I have re-modeled cabooses).

So long,

Andy

Brian Leppert wrote:

I would like to get opinions from this group on what do you think is the optimum HO truck bolster clearance hole for mounting the truck to the car.
Tahoe Model Works currently has a clearance hole about .120" diameter. Has anyone been happy with it? I'm willing to change it.

It's fine with me, Brian, as it is. Like a couple of other responders, I actually like using a bushing on the truck screw, as it's performed well in my experience. (As my number of Athearn body bolsters shrinks, the use of the Athearn boss is decreasing accordingly!) But if you went to a smaller clearance hole, I'm sure it would still work.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@...
Publishers of books on railroad history

--- In STMFC@..., "Brian Leppert" <b.leppert@...> wrote:

I would like to get opinions from this group on what do you think is
the optimum HO truck bolster clearance hole for mounting the truck to
the car.

NMRA's RP-23 calls for a .089 diameter hole to clear #2 screws. Only a
few manufacturers follow this. Most have a hole larger than 1/8 inch.

It seems to me that the smaller hole would be best for resin kits. But
would it also be OK for plastic cars?

Brian,

Why would you want to pivot the truck around screw threads? What would
you tighten the screw against?

Tahoe Model Works currently has a clearance hole about .120" diameter.
Has anyone been happy with it? I'm willing to change it.

The de facto standard has become clearance (you get to define the
clearance you think you can hold) on a nominal 1/8" boss. Your truck
will be a .0035" interference fit on an Accurail body bolster. Looking
at my notes from years ago, Athearn used a .137" clearance hole, and
WKW used .132". Accurail trucks gage pin at .130" - .131"

Anyone who needs a "kingpin bushing" to adapt the nominal 1/8" hole to
a #2 screw can easily cut the boss off the inside of a Kadee coupler
box; most modelers have about a million of these laying around. These
are .124" O.D. with a clearance hole for a #2 screw, and are about
.060" long when sliced off the mounting plate.

Just in case anyone is still hanging around from the NMRA standards
discussion or a few weeks ago, THIS is why if they can't see their way
clear to updating RP-23, they ought to just withdraw it. It only now
serves to cause confusion.


Dennis Storzek
Accurail, Inc.

FWIW, a 2-56 thread has a .0813 - .0854 major ("outside") diameter.

Kl

If it fits the 2/56 Im fine.
 
Bill Vaughn

There is another way to do this: Make a thin "washer" which fits inside the "cup" of the bolster,
and in the center of that make a clearance hole for 2-56. Then put this on the screw shaft before
applying the truck.

SGL

Brian,

I would like to see the hole slightly larger. I, like many others who build resin kits, cut the

"boss' off the bottom of the

Kadee coupler box lid and use it as the swivel for the trucks. Right now I have to ream the hole

in your trucks to make

this arrangement work.

Not a big deal, but a slightly larger hole would make things a little easier.

Paul Lyons
Laguna Niguel, CA

-----Original Message-----
From: Brian Leppert <b.leppert@... <mailto:b.leppert%40att.net> >
To: STMFC@... <mailto:STMFC%40yahoogroups.com>
Sent: Mon, 16 Jun 2008 9:55 am
Subject: [STMFC] HO Truck Bolster Clearance Hole

I would like to get opinions from this group on what do you think is
the optimum HO truck bolster clearance hole for mounting the truck to
the car.

NMRA's RP-23 calls for a .089 diameter hole to clear #2 screws. Only a
few manufacturers follow this. Most have a hole larger than 1/8 inch.

It seems to me that the smaller hole would be best for resin kits. But
would it also be OK for plastic cars?

Tahoe Model Works currently has a clearance hole about .120" diameter.
Has anyone been happy with it? I'm willing to change it.

Brian Leppert
Tahoe Model Works

Dennis Storzek wrote:

Just in case anyone is still hanging around from the NMRA standards discussion or a few weeks ago, THIS is why if they can't see their way clear to updating RP-23, they ought to just withdraw it. It only now serves to cause confusion.

Maybe they could just mark it with a large stamp, "INOPERATIVE."

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@...
Publishers of books on railroad history