HO to On30 Questions

I know that HO is half of O scale, but does that mean if I take a BLI 2-8-2 and put a new cab and detail parts on it, to make it On30, since they have 63 inch drivers, does that mean that they now have 31.5 inch drivers?

Yup, that´s the way it is!

On30 resembles 2´6" narrow gauge in O scale (1:48), so it is roughly twice the size of HO scale, albeit running on HO track.

Thanks, just wasn’t sure.

Also would a 48 inch radii be a 96 inch radii in HO?

No, it´s the other way around. A 48" radius in On30 is roughly equivalent to a 24" radius in HO.

The true ratio is 55.1%. O (North American) is 1/48 and HO is 1/87.1 So, using your 63" drivers as an example, the drivers would be 34.7" in O. This would be within wear limits for 35" or 36" prototype drivers. The problem with your suggested conversion is that chances are nearly eveything above the drivers is significantly out of scale and/or era. You would have to look closely at the boiler diameter, length, and shape. Obviously, the cab, tender, domes, headlight, and stack would be way of whack. Even if the cylinders scale reasonably, most narrow gauge engines had slide valves, while standard gauge engines made after 1910 (or so) had piston valves.

I guess I’m not seeing the point - there are plenty of good narrow gague model engines available for On30. If you have a BLI 2-8-2 in decent shape, sell it, and use the proceeds towards something more accurate to begin with. If you want to bash a Bachmann On30 model into a specific narrow gauge engine, it’s a lot easier starting point than a BLI HO 2-8-2. There are even conversion kits already available to fit on a Bachmann On30 mechanism (Backwoods Miniatures is one vendor).

It’s in the scales/gauges that don’t have good support that folks do the crossover conversions. For instance, the HO Roundhouse Shay and Rivarossi Heisler are often used for Sn3 or S starting points. They were rather large models in HO, so they work fairly well as a basis where there are no competing models.

my thoughts, your choices

Fred W

If you were to arbitrarily decide that your HO scale layout would henceforth be On30, that nice tract house would suddenly become some lucky little girl’s playhouse - and you could quarter her large dog in the doghouse that used to be a garage.

Likewise, that MW shed is now a coal bunker for the bigger (in size) MW shed you’ll have to build. Just add hinges at the high side of the roof…

There were 762mm gauge 2-8-2s, but they were built in Japan, ran on the East Coast of Taiwan and didn’t even resemble an American 2-8-2.

Chuck (Modeling Central Japan in September, 1964 - in HOj, 1:80 scale, with 2 prototype 762mm gauge feeders to the 1067mm gauge main line)

So, to have a 48" radii, I just have a 24" radii curve? WHAT?

You are getting a few things mixed up here.

A 48" curve is a 48" curve, regardless of the scale. In HO scale, this is a pretty broad curve, in O scale, this is a pretty narrow curve, being equivalent to roughly a 24" curve in HO scale.

I don’t get it cause you are using HO track, so you’d use a 24 inch curve. I don’t get it.

I’m going to go at this from a slightly different angle.

If the prototype you are following uses a 192 foot radius;

  • The 1:48 (O) scale curve will have a 48 inch radius.
  • The 1:87.1 (HO) scale curve will have a 26.45 inch radius.
  • The 1:160 (N) scale curve will have a 14.4 inch radius.

Track gauge makes no difference. Scale is everything.

Turning that around, the prototype radius of a 24 inch radius model curve would be:

  • O scale - 96 feet
  • HO scale - 174.2 feet
  • N scale - 320 feet.

Incidentally, there is nothing intrinsically `HO’ about a 24 inch radius. It would be a streetcar-going-around-the-corner radius in G scale, a tight tramway curve in O scale, a minimum mainline curve in HO scale and Acela country in N scale. It can be laid with any gauge in any of the above scales, not to mention S, TT or Z scale. In TTT (1:450) scale, it’s suitable for Shinkansen and TGV.

Chuck (Modeling Central Japan in September, 1964)

So how nice would a 36" radii be in O scale?

About 65".

Take it easy, quite a few folks mistake gauge for scale…

It also doesn’t work exactly using HO track. HO ties are about 9 ft long and about 8-9" wide and about 18" centers. When you go to O scale the ties become only 5 ft long and about 4-5" wide and on about 10’ centers.

I have seen some people who cut out every other tie from HO track to make On30 track and live with the short/narrow ties.

Another consideration is track spacing. You can’t just use an HO track plan. The On30 cars may be wider than HO and may be as tall or taller than HO. So tracks have to be on wider spacing and vertical clearance will be more, meaning grades may be steeper or need to be longer.