Operating 7 1/4 and 7 1/2 gauge locos on 7 1/2 gauge track !

[keyrouteken]

Hi Everybody-- As my good friend Dave from Mercer Locomotive Works has brought up very interesting topics on this Forum from the past several years as has Bill Shields and a number of other oldtime Eastern Live Steamers, I thought you might ponder this article that was written a couple of years ago by "Nick Edwards" down in Texas. I thought it was very interesting.
Your comments are graciously solicited !!
Ken Shattock
IBLS
www.ibls.org

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Wimberley, Blanco & Southern RR

Nick Edwards wrote this description on 3 August 2014:

"For those of you interested in building and operating a railroad to handle 7-1/4 inch and 7-1/2 inch gauge equipment on a 7-1/2 inch gauge track, I submit the following. As a background, we did this for 10 years in 7-1/4 inch country in New Hampshire and have been doing it for over 12 years in 7-1/2 inch country in Texas. A few comments follow.
We started dual gauge operations in 1980 in New England on a small 2000 foot track in Nashua, New Hampshire on an acre plus of land with a 35 foot minimum radius. The track was laid on pressure treated Southern Yellow Pine ties (2x4’s with the 2 inches exposed) using #10 sheet-metal screws to hold down the rail. We gauged the track at 7-1/2 inch as most of the equipment that would be running would be 7-1/4 inch gauge. We had many skeptics, and some of the engineers felt they could feel their locomotives “hunt” the track and complained about it. We could not feel it “hunt” on 0-4-0 switchers. Other than these complaints, we had no derailment problems. Locomotives as big as a Pennsy E-6 (4-4-2) and small consolidations had no trouble with the radius. Of course, these were mostly 7-1/4 inch locos with plenty of tolerance to run on the 7-1/2 inch track. We also ran Pacifics with no difficulty on the 35 foot radius. The diesels had no trouble that we ran.
When we moved to Texas, we thought that we would duplicate what we did in New Hampshire on the track gauge and Southern Yellow Pine ties to a 60 foot minimum mainline radius. We learned that these Southern Yellow Pine ties would expand and contract “lengthwise” up to 1/4 inch per foot depending on the weather, which was a surprise to us. Research with Glen Conrad at Ethan Allen led us to Gene Wengert at the U. of Wisconsin (Woodweb), which then led us this knowledge of this longitudinal tie shrinkage. With a gauge overlap tolerance of around 1/8 inch for the 7-1/4 inch equipment, we learned that you need very dimensionally stable ties such as concrete or plastic ties (Trex) so that gauge would not be compromised. We are still fighting this gauge change battle, as plastic ties cost over $1.50 each, and with around 15,000 feet of track, it would cost us over $60 K (at 3 ties per foot) to convert this railroad to plastic ties, OUCH! Of note, we only use plastic ties on areas that the ties may expand and contract extensively in shaded areas that might stay wet over time and then shrink in dry weather. Now for what we did for the track.
We use West Coast rail (I formerly owned a part of Railroad Supply Corp.) which has a curved railhead profile on 1 inch high rail and 15/16 inch foot. This helps center rolling stock assuming the rolling stock has tapered wheels. The only change we had to incorporate into the 7-1/2 inch track was in the switches. Here we had the points set at a 3/4 inch gap to allow for the back-to-back clearance of the 7-1/4 inch gauge equipment. We also milled out the frogs to 0.480 (+0.000, -0.005) flangeway width. Finally, we adjusted the gap in the guard rails to have the 7-1/4 inch trucks just skim the widened flange-way and the 7-1/2 inch trucks just miss the point in the frog. By having the guardrails assembled to the switch with horizontal bolts, we can adjust the gap if there are problems. It goes without saying that the IBLS standards should be strictly adhered to on wheel profile and gauge with some suggested changes, all within the IBLS specs. For example, we prefer to have the wheel flange radius profile at 1/8 inch instead of 3/32 inch minimum as specified in the IBLS standards. Also, we like to have 7-1/4 inch equipment wheels machined to a minimum of 0.800 inch wheel width instead at 0.750 inch as that is what a 1.6 scale wheel width would be. Otherwise, on troublesome track, some of the 7-1/4 inch equipment would fall between the rails if the wheel width was at minimum. Also, we cannot handle the old British 7-1/4 inch spec where the back-to back spec was 6-3/4 inch not 6-7/8 inch.
If you want to see pictures of this RR, we are on YouTube and can be accessed as WB&S. Also, since we widen the flangeway on the aluminum frogs, they wear a little faster than on the rest of the track. Les Geddes in Black Hawk, CO has inserts to replace these frogs. We use RRSC frogs for # 4, 6, 7 & 9 switches and diamond crossings, and Cannonball frogs for # 8 and # 11 switches. Les also mills out custom curved frogs if you need them.

Cheers!

Nick Edwards
Wimberley, Blanco & Southern RR

[Bill Shields]

I have personally tried my 7-1/4 riding car on a 'normal' 7-1/2" track and in many places it fell through...

No doubt a 7-1/2 that is gauged 'tight' would work (assuming you can get through guards and frogs), however a track that is wide enough to pass a 4-8-4 in 7-1/2 would probably be trouble for 7-1/4.

Had I thought about this a little more 30 years ago when I started my 7-1/4" engine, I would have put very W I D E tires on everything so that it would have a chance....but then I really do not travel south of where I live to run...so it is a moot point.

I WAS smart enough to build the frames to work with 7-1/4 and the cylinders to handle 7-1/2 in case someone purchases my loco and want a different gauge without TOO MUCH trouble.

Best solution is the 'screw on' tires that can be re-gauged in a few minutes....take out a set screw, rotate the tires 1/2 a turn and put he set screw back in.
Jump on the other size track with a couple of hours of work

Naturally it is easier on a Shay...

[pat1027]

Bill Fitt built his railroad with the intent of accommodating both 7-1/4" and 7-1/2" equipment (and demonstrating it could be done). He stuck with 100' radius curves to avoid conventional wisdom or widening the gauge slightly in curves. I believe he used a spring loaded guardrail at his switches. His ties we concrete make from Harry Herder's molds. I'm sure he wrote about in either Live Steam or Modeltec. He had a few visitors with 7-1/4" equipment though not as many as he'd hoped. But Cadillac was a bit off the beaten track for the 7-1/4" guys..