Scale size and actual size for 1-1/2" scale?

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rkcarguy
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Scale size and actual size for 1-1/2" scale?

Post by rkcarguy » Wed Dec 20, 2017 5:05 pm

I've got a question for all of you 1-1/2" scale guys.
What actual scale are you building stuff to, for 7-1/2" gage rails?
True 1/8 scale would mean the average 50' box car would be 15-7/8" wide and 83-1/4" long OAL, but at a more suitable width for people to sit inside them for example like a gondola, they probably need to be north of 20" wide. At 1/6th scale, that same boxcar is 21-3/4" wide and 111" long OAL, and that's a big difference between the two. One scale would use 4-1/2" diameter wheels, and I'm modeling in 1/6th scale which lands me at using 6" wheels.

Kimball McGinley
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Re: Scale size and actual size for 1-1/2" scale?

Post by Kimball McGinley » Wed Dec 20, 2017 5:21 pm

I have seen a lot of use of a scale of 1.6" /foot as opposed to 1.5"/foot. They say it is a better match for 7-1/2"gauge /46-1/2" prototype gauge.

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aopagary
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Re: Scale size and actual size for 1-1/2" scale?

Post by aopagary » Thu Dec 28, 2017 11:11 pm

it's actually worse than you think. 15.875" assumes outside dimension of 10" 7", but if you calculate for inside dimension of 9' 6" you'll get an even tighter 14.25" in 1:8 scale, stingier than even the airlines who stuff you into a average 17.5" wide seat. luckily the only parts of passengers confined to the inside of my riding gondolas are their feet, ankles and a bit of calf. the bulk of passenger mass is well above the gondola sides which allows for a standard fold-down boat seat.

true, 1.6"/ft will be more accurate for 7.5" gauge, but it will add less than an extra inch in car width with the downside of having to deal with a 21% bigger car.

cheers...gary
passenger gondola.jpg

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ALCOSTEAM
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Re: Scale size and actual size for 1-1/2" scale?

Post by ALCOSTEAM » Fri Dec 29, 2017 9:09 am

Kimball McGinley wrote:I have seen a lot of use of a scale of 1.6" /foot as opposed to 1.5"/foot. They say it is a better match for 7-1/2"gauge /46-1/2" prototype gauge.


If you are making your calculations off of 46 1/2" track gauge you will have problems. Standard gauge is 56 1/2" or 4' 8 1/2".

rkcarguy
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Re: Scale size and actual size for 1-1/2" scale?

Post by rkcarguy » Fri Dec 29, 2017 12:34 pm

^^^ This is true.
I guess I was asking more or less, if many of you build your rolling stock over-width in relation to scale, to suit your riders/cargo.
I'm building to 2" scale on 12" gage, reason being it's big enough that I can have 20" wide inside dimensions on gondola's and hoppers and such and be able to move some serious weight without being so tippy, yet I wouldn't look too out of place if I was to bolt on 7.5" gage wheel sets and attend a run at one of the clubs. I do realize that 12" gage is quite out of scale at my 2" scale.

1.6 scale comes out to a rail gage of about 7-7/16, while 1.5 is about 7-1/16", so that makes sense that if you go to 1.6, you get a little extra width and are more to scale with your rail gage.

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FLSTEAM
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Re: Scale size and actual size for 1-1/2" scale?

Post by FLSTEAM » Fri Dec 29, 2017 12:58 pm

So the simple solution is just build narrow gauge 2 1/2" scale. Width comes out to 20"
At least that's what all my cars are.

John B
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Re: Scale size and actual size for 1-1/2" scale?

Post by Harold_V » Fri Dec 29, 2017 5:00 pm

rkcarguy wrote:1.6 scale comes out to a rail gage of about 7-7/16, while 1.5 is about 7-1/16"
Nope. 1.593 scale (thus the use of 1.6 scale) comes out precisely 7½" gauge, not 7-7/16.

To build to "perfect scale" for 7½" gauge, prototype dimensions should be reduced to 13.275%

H
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Re: Scale size and actual size for 1-1/2" scale?

Post by Glenn Brooks » Fri Dec 29, 2017 7:57 pm

My first 7.5” train set had four plywood riding cars built 20” wide. They derailed constantly, with the slightest shift in weight by any passenger. No idea who built them, but they weren’t functional for commercial, indeed, any passenger hauling at all. I cut them down to 16” or 18” width- can’t remember now- but they became absolutely stable under nearly all passenger activity during a Christmas train ride one year - hauled nearly 5000 people in 3 weeks operation with no issues.

which gets around to the point that scale and gauge are really not meant to be directly related. Gauge is a convenience for carrying wide objects, and maybe more importantly, interchangeability of equipment and motive power. Or as Henry Greeley first wrote - a measurement that determines how wide your smokebox can be.

Scale is the ratio of a model’s dimensions to a specific full size prototype. As locomotives and rolling stock were built to nearly every imaginable size possible, for most all common track gauges, one can build in wide ranging scales for any given gauge, and be perfectly fine with the operating environment.

So dealing with scale and gauge, the only thing I ever really worry about is car width - is it stable for the given track gauge when fully loaded, under expected operating conditions, etc. if, so, and it fits within the operating envelope- go for it!

I’ve always heard a good rule of thumb is to build car width up to 2x the gauge. Thus 12” ga track can work with car width up to 24”, maybe a bit more, with good design - proper center of gravity, reasonable turning moments, load height, etc... Same with 7.x” live steam stuff. 15” to 16” cAr widths typically offer exceptional stability, depending on the physics of the C.G., turning movement of the people sitting in the cars, weight of structure, etc.

Glenn
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....

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aopagary
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Re: Scale size and actual size for 1-1/2" scale?

Post by aopagary » Sat Dec 30, 2017 2:44 pm

10' 8", the typical prototype car width is 2.25x standard US track gauge, but when it comes to scale riding rail cars, although the passenger load may be typical of full scale (90 tons translates to ~350 lbs in 1:8 scale), if it is a matter of a determined passenger vs car stability, the passenger will always win. along with the room benefit of passenger mass being above the gondola sides, the ridiculously high CG along with immediate control over a shifting load, the passenger has all the advantages. specialized straddle cars with low LT car mass have the best chance at solid stability, but prototype designs require at least moderate passenger responsibility.

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BigDumbDinosaur
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Re: Scale size and actual size for 1-1/2" scale?

Post by BigDumbDinosaur » Sat Dec 30, 2017 4:54 pm

aopagary wrote:10' 8", the typical prototype car width is 2.25x standard US track gauge, but when it comes to scale riding rail cars, although the passenger load may be typical of full scale (90 tons translates to ~350 lbs in 1:8 scale), if it is a matter of a determined passenger vs car stability, the passenger will always win. along with the room benefit of passenger mass being above the gondola sides, the ridiculously high CG along with immediate control over a shifting load, the passenger has all the advantages. specialized straddle cars with low LT car mass have the best chance at solid stability, but prototype designs require at least moderate passenger responsibility.
Something else that helps in achieving lateral stability is a relatively high car weight coupled with a low roll center. The control (aka riding) car for my F7 has seating at a comfortable height for both engineer and conductor, yet has good roll stability. This was achieved with the combination of a low deck height and high car weight—approximately 300 pounds. The low deck height also makes it easier for lame, elderly engineers to get on and off. :D

The problem with using gondolas and flat cars as riding cars is they are not particularly heavy, which means the car weight is a fraction of the loaded weight with passengers. The exceptionally high loaded CG, as noted, compromises roll stability, making it relatively easy for a passenger to inadvertently cause a derailment by merely leaning to one side or shifting suddenly in his or her seat. It was for these reasons, as well as a bit of lameness on my part, that I designed my control car the way I did. I couldn't do too much about the CG, but I could make the car a significant part of the loaded weight. This has proved out in use: the car has yet to derail in service.

My opinion has long been if you are going to routinely haul passengers you should use cars designed for the purpose, and leave the freight cars in their role as freight cars.
control_car_rsfqv01.jpg
F7 Control Car
Above is the control car fresh out of the paint shop.
at_rr01.jpg
Locomotive & Control Car
Above is a side view of the F7 and control car. In this photo, it can be seen that the car's deck height relative to the railhead is quite low. Aside from making it easier to get on and off, in the event of a derailment the car is less likely to roll onto its side and dump the passengers on the ground.
ctl_car_under01.gif
Underside of Control Car
Above is an underside view of the control car. Note the "backbone" (center sill), which is fabricated from 11ga × 2 × 4 tubing in the middle and 11ga × 2 × 2 tubing at the ends. The sheet metal components were fabricated from 12 gauge hot rolled P&O.
ctl_car_truck01.jpg
Control Car Truck Assembly
Above is one of the control car's trucks. These were built up from some old Tom Bee side frames intended for EMD Blomberg "B" trucks. The wheels are also Tom Bee products. Each truck assembly weighs around 75 pounds, with all but the wheelset weight being sprung, giving good riding qualities on uneven track, as well as a low roll center for improved stability.
Science makes it known. Engineering makes it work.

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Erskine Tramway
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Re: Scale size and actual size for 1-1/2" scale?

Post by Erskine Tramway » Sun Dec 31, 2017 12:29 pm

My solution for stability is mostly a low center of gravity where the seats are. Admittedly, my equipment isn't 1-1/2" scale, but 'full size for the gauge', and 24" wide. Here's a picture of my unfinished passenger coach pressed into service on the occasion of our daughter's Wedding. When the coach is finished, it will have sides about as tall as the end boards of the loco, and a roof about 56" off the rail.
8-2-16 wedding party.jpg
As you can see, the seats are quite a bit lower than the seats on 'Sparky", aka Motor #1.

Mike
Former Locomotive Engineer and Designer, Sandley Light Railway Equipment Works, Inc. and Riverside & Great Northern Railway 1962-77
BN RR Locomotive Engineer 1977-2014, Retired

rkcarguy
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Re: Scale size and actual size for 1-1/2" scale?

Post by rkcarguy » Tue Jan 02, 2018 1:13 pm

I love the trucks BDD. Nice design to allow pivoting and a lot of "articulation" without allowing the car to lean.
My "plan" is to build a hopper car with an open front that I will sit *inside* for my engineer's car, and then a pair of 40' bulkhead flats which will haul firewood and have bench seat "modules" I can attach for riders.

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