Steam & Excursion > Shay locos: How many teeth om the Pinion gears?

Just wondering>>>

Did Shays use one gear ratio, or did the number of pinion teeth vary from a set of 'choices'?

The 3-cylinder engines on the 4-trucks Shays (pictured) seem to be relative 'monsters'.
Any comments?

Wes C.

Wes,

You could order Shays with different numbers of teeth so that the gear ratio would be taylored to the buyers needs.

Martin

The WM Shays were supposedly capable of near 40 mph, pretty high geared for a Shay.

Out

If that's true, and I'm not saying it isn't, but why buy a Shay?

Posted from iPhone

Because it would also run much slower than a diesel on a continuous basis. I'm not completely sure
on the mph thing, I've heard it several times, once at 45 mph (which I dismissed) but would like
someone to say for sure.

Out

Below are a couple of cuts from my 1925 Shay catalog. They describe the standard shay gearing and the alternate gear that Lima provided and the reasons for the alternate gearing. Notice also the gear ratio and that no where is it less than 2-1. This was pointed out to me recently and it means that for every revolution of the drivers, each cylinder makes two strokes, or effectively 8 power strokes per revolution, twice as many as a rod engine for the same number of revolutions.

Thus a rod engine with 48" drivers moving at 30 mph, requires 210 rpm or 210 strokes from each piston per minute (roughly 3 per second). To achieve the same speed with a large shay would require 420 rpm or 6 strokes per second. At that same piston speed your 48" drivered rod engine would be going 60 mph.

Since most shays have drivers smaller than 48" and gear ratios higher than 2, it appears to me that speeds over 30 mph would be virtually impossible for a shay without simply having the engine tear itself apart.

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WM6 has a non-stock gear ratio (it is shown in the nice soft cover book published on it) which is a somewhere around 2.45:1. It has been pointed out to me that even though WM 6 has 48" drivers, her lower gearing makes her about the same speed as a "normal" Shay with 36" drivers. Pacific Coast Shays had a lower than normal gear in the same range. If you can get 18mph out of a fast geared Shay, you are looking for trouble (and for the parts that are ejecting themselves).

That certainly makes more sense, still those speed rumors have been around for years.

Out

Martin can tell you top speed of two Shays, Mt. Emily No. 1 and Graham County 1925, which had a "drag race" at Railfair 99. I am pretty sure the top speed was 18 mph.

nycman Wrote:
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> Martin can tell you top speed of two Shays, Mt.
> Emily No. 1 and Graham County 1925, which had a
> "drag race" at Railfair 99. I am pretty sure the
> top speed was 18 mph.

Shay racing sounds like a dry land version of Submarine races.

callum_out Wrote:
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> The WM Shays were supposedly capable of near 40
> mph, pretty high geared for a Shay.
>
> Out


Perhaps that's how fast WM 5 was doing when it ran away and wrecked in the early 1940's