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Offline Mr. Ron  
#1 Posted : 31 December 2020 21:01:11(UTC)
Mr. Ron

United States   
Joined: 05/07/2020(UTC)
Posts: 311
Location: Mississippi, Vancleave
Why is HO scale 1:87 proportion? 1:87 is such an odd number to work with. It could have been 1:84 or 1:90, but why such an odd number?
Offline EMD_GP7  
#2 Posted : 31 December 2020 21:32:52(UTC)
EMD_GP7


Joined: 23/11/2010(UTC)
Posts: 192
Location: U.K. Midlands
Because H0 scale is 3.5 mm to the foot.
Therefore 1 inch = 25.4 mm x 12 = 304.8mm divided by 3.5 = 87.08.
So the scale is 1:87
Hope this helps.
Colin.
thanks 5 users liked this useful post by EMD_GP7
Offline Mr. Ron  
#3 Posted : 01 January 2021 19:34:55(UTC)
Mr. Ron

United States   
Joined: 05/07/2020(UTC)
Posts: 311
Location: Mississippi, Vancleave
Originally Posted by: EMD_GP7 Go to Quoted Post
Because H0 scale is 3.5 mm to the foot.
Therefore 1 inch = 25.4 mm x 12 = 304.8mm divided by 3.5 = 87.08.
So the scale is 1:87
Hope this helps.
Colin.

OK, but why 3.5mm to the foot; why not xxmm to the meter? why mixing metric with imperial?

Offline DaleSchultz  
#4 Posted : 01 January 2021 20:33:07(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,997
The arbitrary value came from O gauge tracks that were spaced 1-1/4" apart. Perhaps 1-1/4" just seemed a reasonable size and they felt that 1" was too small.

1.25" = 31.75mm

A track spacing of 1384mm / 31.75 = 43.59

HO is half of that
43.59 * 2 = 87.18

hence 1:87

Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline kimballthurlow  
#5 Posted : 01 January 2021 21:11:36(UTC)
kimballthurlow

Australia   
Joined: 18/03/2007(UTC)
Posts: 6,653
Location: Brisbane, Australia
Originally Posted by: Mr. Ron Go to Quoted Post
Originally Posted by: EMD_GP7 Go to Quoted Post
Because H0 scale is 3.5 mm to the foot.
Therefore 1 inch = 25.4 mm x 12 = 304.8mm divided by 3.5 = 87.08.
So the scale is 1:87
Hope this helps.
Colin.

OK, but why 3.5mm to the foot; why not xxmm to the meter? why mixing metric with imperial?



Hi Ron and all,

That is a very good question and I have pondered on this for 60 years, and believe I have the answer.
The mixture of metric:imperial occurred because German manufacturers in the ealy 1900s were contracted by British model outlets.
Think of names like Bassett Lowke. These people sold a lot of toys so they contracted the capable manufacturers like Bing, Märklin, Karl Bub and Carette.

When the British offered diagrams of models at 1/4 inch to the foot (a common imperial engineering scale), the manufacturers simply converted that to 7mm to the foot (O gauge 1:43.5).
This assisted the design and build process in their workshops where they worked in mm.

Kimball
HO Scale - Märklin (ep II-III and VI, C Track, digital) - 2 rail HO (Queensland Australia, UK, USA) - 3 rail OO (English Hornby Dublo) - old clockwork O gauge - Live Steam 90mm (3.1/2 inch) gauge.
thanks 1 user liked this useful post by kimballthurlow
Offline H0  
#6 Posted : 02 January 2021 17:57:44(UTC)
H0


Joined: 16/02/2004(UTC)
Posts: 15,254
Location: DE-NW
The model gauge is 16.5 mm.
The prototype gauge comes from imperial units and it is about 1435 mm. The ratio is 1:86,969696969696969696969696969697 if you take 1435 mm.
Regards
Tom
---
"In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS
UserPostedImage
thanks 1 user liked this useful post by H0
Offline Mr. Ron  
#7 Posted : 02 January 2021 19:55:11(UTC)
Mr. Ron

United States   
Joined: 05/07/2020(UTC)
Posts: 311
Location: Mississippi, Vancleave
Originally Posted by: H0 Go to Quoted Post
The model gauge is 16.5 mm.
The prototype gauge comes from imperial units and it is about 1435 mm. The ratio is 1:86,969696969696969696969696969697 if you take 1435 mm.


Thank you all for enlightening me; an inquisitive mind needs to know.
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