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Regauging a MDC Shay

From Tobias Giles
Tue, 19 Aug 1997

>I am interested to learn if anyone has modified an MDC (Roundhouse)
>2-truck, 3 foot Shay to run on HOn30" gauge.
>If so, I would be very interested in any specific modifications that
>need to be performed to make this work.  I have researched this and it
>appears that the conversion is possible.

Although I am upscaling the MDC HOn3 shay into a Sn3 shay (using a V&T conversion kit), down-gauging to 9mm *might* be a problem (and I’ll check tonight). The housing, for the inner (and real) drive shaft & worm gear and truck axles & gears, seems to be about 9 or 10mm wide. If it is this wide, then it going to be tuff to reduce the width (not much material there). It’s also made of Delrin.

There is also the metal electrical pickup plate that goes between the wheels and the side of (this) housing which adds to the total “thickness” of things between the wheels. Of course, the electrical contact plate could be redesigned and eliminated.

Later info as it becomes available.



Greetings gang,

I went home for lunch and took a few measurements. I’ll have to correct myself. Technically, it’s not a problem to narrow the “power truckhousing(s)”. The outer housing dimension is only 8.3 mm wide with the outer walls a thick 1.4 mm. The flanges roughly measured to .8 mm (add a little more for smooth running on curves), so by sanding down a little over .5 mm from each side, you could squeeze in the wheels. You would still have to forgo the kit-provided electrical pick-up plate, but from what I have read and seen, some (re-)work is required anyway.

I presume you know that this “narrow gauge” shay is just the standard gauge MDC shay with smaller trucks? This kit shay is a fair size beast even for standard gauge (I have the 3 truck NG version) and when place over or near a 3ft gauge track, it’s just down right BIG. I found the visual difference
laughable for 3ft. At the time, a friend had leant me his 2 cylinder, 2 truck brass shay (joe works?). It “looked” right for the gauge. The MDC was a whale. Period.

Although visual appeal is subjective (and to each his/her own !), you may have a center of gravity problem. The boiler is solid metal and you may not know for certain until you build it. If you do get it to work, please tell me (and the list) about it.

On this project, I will have to wish you “best of luck”.



>I did regauge one HO Shay to Sn3.  Tobias, I think this would be easier than
>starting with the HOn3 model.  You do have to cut off part of the "ears" on
>either side of the main truck center piece that holds the gears.  I seem to
>remember that for HOn3, the "ears" would have to be completely gone, so HOn30
>may be a problem.
>Dave Heine

You are correct in remembering the “ears” (for the rest of you on the list, these are stand-off spacers that hold the truck frames out to the correct spacing depending upon the gauge) for the HOn3 are completely gone. As per the instructions from V&T, one needs to remove 1/32 (or 1/16? can’t remember now) from the standard gauge housing spacers.
Actually, according to the V&T kit instructions, one needs to start with a standard gauge kit. In my case, I order two power truck housings and a standard gauge frame (all of about $14.00) to bring my original NG shay kit back to a standard gauge kit.

>I am currently building (the project that lasts forever) somewhat slowly the
>MDC shay as an Sn2 model.   It would be estremely difficult to modify this 
>model to HOn30 as the truck gear box casting which delivers power to the >axles is too wide to allow reducing the gap between the wheels.

Humm, if Brian is talking about the vertical gear assembly (and it’s housing) that drops down thru the cab floor, he may have a point. But I think everybody on the list now knows this shay might (again, to each his / her own) be too big for this project and we’re talking trival now. . . .


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