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O gauge is 1:48 and HO was defined as Half O.  Thus HO should really be 1:96 (double the 48).  Is there a reason why HO was scaled as 1:87?  Motors too large to fit smaller engine shells, could not cast fine details at 1:96, track width derived from European trains metric sizes drove the HO 1:87 decision (this last would be my best guess), or

Have not read of an explanation but sure there is a reason for the 1:87 scale. 

 

Original Post

Actually, I believe HO's basis is 3.5mm to the foot...which probably comes closest to 1:87, rather than 1:96.

12"=304.8mm

3.5x87=304.5mm

3.5x96=336mm  

In the early days of HO, some manufacturers (notably Varney), treated O scale as 1/4"=1 foot and manufactured product at a scale of 1/8"=1 foot.....Half O,.......naturally!   Trouble is, 1/8" is undersized to the prevailing standard of 3.5mm to the foot.  1/8"=3.175mm.  My first HO set (going over to the Dark Side)......at the ripe young age of 12 was a Varney freight set....laid out on the ol' ping-pong table straddling the Lionel layout beneath.  When I ventured into building a Silver Streak boxcar, and placing it next to the Varney boxcar, I was puzzled....to say the least.  One of Dad's business associates...who had an attic full of HO...explained it through Dad to me, why the difference.  

As the lifelong hobby unfolded...O, HO, then a variety of G gauge scales, then back to O3R (traditional vs standard), the variety of scales and sizes throughout became the stuff of...

good grief.2

...and of diminishing consequence and concern.  

So, I tend to let the Pickers-of-Nit do their thing.  I do mine: Have fun.

KD

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Last edited by dkdkrd
@rrman posted:

O gauge is 1:48 and HO was defined as Half O.  Thus HO should really be 1:96 (double the 48).  Is there a reason why HO was scaled as 1:87?  Motors too large to fit smaller engine shells, could not cast fine details at 1:96, track width derived from European trains metric sizes drove the HO 1:87 decision (this last would be my best guess), or

Have not read of an explanation but sure there is a reason for the 1:87 scale. 

 

i guess you had to be there.

I think I remember reading somewhere (so, don't quote me!!) that O scale in England was (and may still be) 1:43.5 scale.  Thus, when Half-O was created (1/2 x 1/43.5), it came to 1:87.  On the European continent, 1:87 translated to 3.5mm gauge and O translated to 7mm gauge.  Also, if I remember correctly, in HO there is no difference between the scale size of pieces and track width (gauge), so the Proto87 guys are only worried about oversize flanges, oversized couplers, and other accoutrements that are intentionally oversized for ease of modeling and use.

Chuck

@PRR1950 posted:

I think I remember reading somewhere (so, don't quote me!!) that O scale in England was (and may still be) 1:43.5 scale.  Thus, when Half-O was created (1/2 x 1/43.5), it came to 1:87.  On the European continent, 1:87 translated to 3.5mm gauge and O translated to 7mm gauge.  Also, if I remember correctly, in HO there is no difference between the scale size of pieces and track width (gauge), so the Proto87 guys are only worried about oversize flanges, oversized couplers, and other accoutrements that are intentionally oversized for ease of modeling and use.

Chuck

I definitely remember reading this somewhere, too.  And since it makes perfect, logical sense, I would believe it to be true.

One small correction though, it's 3.5 mm and 7.0 mm to the FOOT, not gauge.  But I knew what you meant. 

If we trust Wikipedia on this one, it's based on being half of the smallest size Marklin made in that time frame, and was actually a zero, not an "O".  Supposedly Germans don't call it HO for this reason, they do call it H0.  Us crazy Americans often substituting "oh" when we mean "zero" since it rolls off the tongue easier...

Link here.  Though a long entry, this part is in the first 2 paragraphs.

-Dave

Last edited by Dave45681

Your mixing scale and gauge. O gauge isn't really correctly scaled for 1:48 first off. So any comparisons of scale is redundant.

Ho gauge is very close to half of O gauge.

 So close you can in fact sometimes run an HO engine on the center rail and one outer rail of some 3r O track.

Ive done it.

Curves weren't real great but fwd/ rev was no issue (tube track and scalish ho flanges and it still worked, lol) Something like GG or other T profile 3r track might work like a charm for HO too.(except for turnouts, etc )

 

HO at 3.5mm to the foot comes from Europe where the scale originated in the early 20's and true O scale is 1:43.5 as opposed to what we use in the US as OW5 or 5' between the rails at 1:48.  That war was fought in the 30's and 1:48 won.  Who knows why, but 1/4" to the foot is easier to calculate than 17/64" to the foot.

Originally 4mm and 3.5mm were considered HO, but eventually it got sorted out in the mid to late 20's that HO was 3.5 mm to the foot and 00 was 4 mm to the foot.  

Confused yet?

O gauge 1/48 was originally 0 (zero or zed) gauge.  Number 1 gauge was 1/32 and number 2 was 1/24.

Because of the smaller sizes or European and English trains they went and turned O into 1/45 and 1/43,5 respectively in order to fit motors then available.  When the English created HO it became 1/87, but then they discovered the trouble of fitting motors in their locomotives and created OO 1/76, using either 16.5 mm HO track, or the correct 18 mm OO track.

Stuart

 

And then there's the international foot versus the United States foot which are different by a tiny, tiny percentage.  Who knows why there is a difference at all?  Although it surely can make life interesting for surveyors or bridge or highway builders.  It's not relevant for us modelers, though, but I threw in in here just for grins.

@PRR1950 posted:

I think I remember reading somewhere (so, don't quote me!!) that O scale in England was (and may still be) 1:43.5 scale.  Thus, when Half-O was created (1/2 x 1/43.5), it came to 1:87.  On the European continent, 1:87 translated to 3.5mm gauge and O translated to 7mm gauge.  Also, if I remember correctly, in HO there is no difference between the scale size of pieces and track width (gauge), so the Proto87 guys are only worried about oversize flanges, oversized couplers, and other accoutrements that are intentionally oversized for ease of modeling and use.

Chuck

That’s correct. European O Gauge was, and still is 1:43.5, 7mm/ft on 32mm or 33mm Gauge Track. HO was, and still is half of that, 1:87, 3.5mm/ft on 16.5mm Gauge Track. British HO never really established itself, and British OO became standardised at 1:76, 4mm/ft on 16.5mm Gauge because of various practical aspects of making models of British outline locomotives and stock.

For various reasons, when modelling British outline it’s easier to be under-Gauge relative to scale, whereas for American outline stock it’s easier to be over-gauge relative to scale. 

As mentioned before by others, I believe it originated because the British O Gauge is 1:43.5.  Still doesn't explain the precise 1:87.1 that HO is, but the 0.1 is always rounded down to 0 to be 1:87, or that the British HO is 1:76.  But then, to use another example, N Scale in the US is 1:160; 1:150 in Japan, and 1:148 in the UK.  The wonderful world of model railroading!!!

Last edited by Amfleet25124

As mentioned before by others, I believe it originated because the British O Gauge is 1:43.5.  Still doesn't explain the precise 1:87.1 that HO is, but the 0.1 is always rounded down to 0 to be 1:87, or that the British HO is 1:76.  But then, to use another example, N Scale in the US is 1:160; 1:150 in Japan, and 1:148 in the UK.  The wonderful world of model railroading!!!

That's because HO scale is exactly 3.5 mm to 1 foot.  Do the math with a scientific calculator, and even 1/87.1 is a rounded off figure.

Matter of fact, British O-scale is exactly 7.0 mm to the foot.  And likewise, 1/43.5 is also a rounded off figure, even it is not exact.

But to heck with the math, we're just splitting hairs at this stage.  My advice is to go run our 3-rail, 1/48 scale (sorta' kinda', more or less) O-gauge trains and let the HO and N-scale guys squabble over exact dimensions with their micrometers and their rivet counting.   

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