1.5" versus 1.6". What's the difference?

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PRR5406
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1.5" versus 1.6". What's the difference?

Post by PRR5406 »

Just curious about this. So many people build their equipment in 1.5" scale, yet some of the very productive experts in teh field swear by 1.6" scale. Okay, it's a multiple that's one-tenth of an inch larger. There must be some reason for the difference. Would anyone put forth an explanation?
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LivingLegend
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Re: 1.5" versus 1.6". What's the difference?

Post by LivingLegend »

If you're building for 7.5 gauge track, 1.6 scale makes the model proportionate to that gauge.....

The correct track gauge for 1.5 scale is 7.0625. So, for the purist, 7.25 gauge track makes the model proportionately smaller.

Other than that, it doesn't matter much either way.

LL
Last edited by LivingLegend on Sat Oct 13, 2012 12:23 pm, edited 3 times in total.
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Re: 1.5" versus 1.6". What's the difference?

Post by Fender »

An exactly scaled standard-gauge track in 1.5" scale would be 7.0625" between the rails. Many of the tracks in the US are built to 7.5" gauge. So the track is about 6% too wide for this scale.
To compensate for this discrepany some builders make their locos about 6% larger, to match the track. And 1.6" scale is about 6% larger than 1.5" scale.
(Yeah, what LL said)
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Re: 1.5" versus 1.6". What's the difference?

Post by RichD »

I'm building my 1887 Schenectady tenwheeler to 1.6" scale which is correct for
7-1/2" gauge. That additional .1"/ft adds up quick.
With todays calculators, computers, CAD, etc. why stick with even fractional rule dimensions.
Uh, actually, rules come graduated in tenths too!
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VO4454
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Re: 1.5" versus 1.6". What's the difference?

Post by VO4454 »

The technical amount of difference per inch is .00774 of an inch. While that does not sound like a lot, as an example, the GS-4 I am modeling is 110 feet knuckle to knuckle. In 1.5 scale it is 13'-9". In 1.6 scale, or technicaly 1.593, it is 14'-7". That small difference adds up to 10 inches. In my very humble opinion, unless you are going to build something by using commercially available castings, that are only available in 1.5 scale, I would model in 1.6 scale, only for 7-1/2 track gauge. If you work from prototype blue prints there is also no having to compromise things like cylinder center to centers or thinning of rods, drivers or valve gear for clearance reasons. The conversion is as follows 7.5 inches divided by 56.5 . One inch now eqauls .13274 inch. Some will round that to .133 inch. I personally do not. Got to agree with Rich.

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Re: 1.5" versus 1.6". What's the difference?

Post by FLtenwheeler »

Due to the fact that a lot of the high detail parts, are being made to 1.6 so I will be building the CNW J to 1.6 scale. The only problem I am having is finding cylinder casting that I can use. I need cylinders with a 4.266 stroke.

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Re: 1.5" versus 1.6". What's the difference?

Post by Doug_Edwards »

Vic touched on one of the more practical reasons for modeling in 1.6 if you are scratch building from prototype data: You can build from the prints with out having to redesign the locomotive to account for the 7/16" difference in width between 7 1/16th and 7 1/2 track gauges. And if you do make the adjustments, you can end up with a loco that is 1.5" long and tall, but 1.6" wide anyway!

An interesting example of compromise is the Little Engines Atlantic/pacific design. For some reason, the cylinder and valve bores were held to 1.5" center lines, and allowances were made to compromise for this. However, the lead truck flanges cut into the cylinder covers when the locos are built to 7.5" scale (not sure if they do in 7 1/4 as well). If I remember correctly, the radius rod also has a dog leg in it to bring it back to the valve center line, as the link has to be off set enough to be out side of the drivers, and does not line up with the valve chest.

The Saturated Steam Atlantic was built to 1 9/16" to the foot in what is in my opinion a better thought out compromise to accommodate both 7.5 and 7.25" gauges. The scale falls between the .1283 per inch for 7.25 and .1327 for 7.5, being .1302 per inch. I am told however, that the drivers on the particular engine end up very close to the jacketed boiler in 7.25" gauge.

It is unfortunate that the the track gauge was screwed up in the beginning, as it would have been much easier just to build to scale to 7.0625" gauge, and have 1/8" equal a full sized inch, instead of ending up using an odd decimal. I personally have ended up using .13333 per inch, and do end up with a small error on the back to back of the wheels that I have to account for, but the ease of having 3 inches scale out to .4" rather than .3982 seems worth it.

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Doug
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Re: 1.5" versus 1.6". What's the difference?

Post by LSGOD »

One thing I noticed real quick while I was building my cab forward was that I had to design the trailing truck for 1.6 width and 1.5 length. Also the cylinders are outside the running boards. My SP&S Z8 is being built to 1.593 scale. Much easier.

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Re: 1.5" versus 1.6". What's the difference?

Post by aopagary »

from a more pragmatic viewpoint, i would rather live with a 0.22" over-gauge error vs having to deal with the 21% increase in mass.
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Re: 1.5" versus 1.6". What's the difference?

Post by Fender »

Of course, you could choose to build a Russian (i.e. five foot gauge) locomotive, and no compromises are required....5 feet = 60 inches, 60 inches in 1.5" scale is 7.5".
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LivingLegend
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Re: 1.5" versus 1.6". What's the difference?

Post by LivingLegend »

Hmmm.... A Russian 4-14-4?

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Re: 1.5" versus 1.6". What's the difference?

Post by Pontiacguy1 »

LivingLegend wrote:Hmmm.... A Russian 4-14-4?
YIKES! They couldn't get it to run on their track, so imagine trying to find somewhere, anywhere, where you could actually run something like that!

How about just building yourself a Russian Decapod? They actually had a 2-8-4 that they built which was basically a carbon copy of a Van Swearingen Berkshire.
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