SWITCH MACHINES

[NW Modeling List]

Don:  Your description of the Scale Shops drive sounds very familiar to me
as this method was used in early CNC machine tools to rotate tool turrets to
expose a different cutting tool.  To prevent the 'overdriving' from going
past the desired stops, you might try mounting the motors in rubber blocks
or isolation mountings ( little rubber o-rings might be the answer).  By
softening the mount, the overdrive may be able to be turned into a 'squish'
back into the desired alignment.   We also used rubber angular mis-alignment
couplings to provide the necessary absorption of the overdriving forces with
wind-up motion in the coupling- a small, stiff coil spring in the shaft line
might work here.

 

Yes, these were band-aids and were replaced with turrets that lifted up out
of face gear couplings (see CURVIC or HIRTH), rotated, then clamped back
down on these very accurate couplings to lock into position.  Incredibly
strong and essentially 100% reliable rotation ( unless you goofed the
indexing count).

 

Gary Rolih

Cincinnati

 

From: nw-modeling-list-bounces at nwhs.org
[mailto:nw-modeling-list-bounces at nwhs.org] On Behalf Of NW Modeling List
Sent: Sunday, May 15, 2011 6:36 PM
To: 'NW Modeling List'
Subject: RE: SWITCH MACHINES

 

I'll throw in my 2 cents Ed.

 

I help build, maintain and operate a large HO layout (Tom Enloe's Pacific
Northwestern). Typically I operate as yardmaster in a 12 track double ended
yard with station facilities off one end and engine facilities off the
other. I would say that there are approximately 50 switch machines in this
portion of the layout. They are roughly split between Circuitron Tortoise
machines and Scale Shops switch machines. 

 

Tortoises: Once installed, the Tortoise machines are very durable and
reliable. Care is required in the installation in order to get them centered
and set parallel to the throw of the points, but is not difficult. They are
quiet and realistically slow in operation. In the years that I have been
with this layout I have not known a Tortoise to fail. Tortoises are used in
all new construction and most of the modeled railroad has been built with or
retrofitted to them. I am also retrofitting my own much smaller layout with
them from Caboose Hobbies hand throws and would note that they are much
easier to install centered under the points as the turnout is installed (or
at least drill the hole for the throw wire) rather than retrofitting them to
the side or with bent wire mechanisms after the turnout is in place.

 

Scale Shops: These are threaded shaft motor drives where the moving dolly
throws the turnout and makes/breaks a set of contacts, some of which are
part of the motor wiring and stop the motor at the end of the throw. They
are not as precise regarding the mounting as we used all bent wire throws
which left us some adjustment after mounting. Unfortunately I do not rank
them as high in reliability. Since there is some momentum to the motor and
dolly, they can slightly overrun the cutoff point of the contacts. Then when
thrown to the other direction they just whine at very high frequency. Some
of the more senior members can't hear this whine and don't know why the
switch didn't throw. We have also had the contacts get bumped (they are
exposed) which misaligned them or pushed one contact set into another. On
one or two occasions we have had the motor come loose from the base and had
a 50/50 success rate reattaching them. Another observation is that they are
somewhat noisy for the short time they are active and don't contribute to
the realism of the layout (but it's easy to tell if they are working).

 

Twin coils: The PNW staging yard was built with approximately 20 twin coil
solenoid switch machines. I have not peeked under there to see which brand
they are. A few have been replaced but most are still working after 20 years
or so.

 

This layout has been in existence for many years and all 3 of these switch
machine types have served well. Given a choice I have gone with the Tortoise
on my layout.

 

Don Trettel

Roanoke native now living near Seattle.

 

 

  _____  

From: nw-modeling-list-bounces at nwhs.org
[mailto:nw-modeling-list-bounces at nwhs.org] On Behalf Of NW Modeling List
Sent: Sunday, May 15, 2011 7:26 AM
To: NW Modeling
Subject: SWITCH MACHINES

I sent out a note a while ago about anyone with positive experiences with
switch machines (HO).  Don't recall if anyone wrote back but if you've had
good luck installation, operation and mainteance wise would sure like some
tips.
 
Thanks!

Ed Svitil
Norfolk & Western Railway
 
  




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