Minimum Track Radius for Kozo's 3/4" Engines or Similar

[steamrobot]

I notice that many people have a Kozo engine or two listed in signatures. This question is for those who have 3/4" engines of this or similar variety.

What is the minimum track radius that you have been able to use with good results? Larger radius is obviously better but as I am landscaping the backyard, I am debating putting in a small loop.

I am specifically interested in the Shay and A3 but suspect the answer would apply roughly to all Kozo's geared loco designs as well as any 0-4-0 or similar low-driver locomotive.

Thanks for any input you might have.

[Doug_Edwards]

I don't remember seeing a minimum listed, but for perspective, a 3 truck 1.6" scale Willamette takes a 13.5 foot radius, so for the Kozo geared locos, you should be good with a 7 foot or larger radius. This means that if you have a 14x14 living room, you could run one indoors in the winter! Or at Christmas, put the tree in the center of the room, and run the train around it.

Regards,

Doug

[Harlock]

I don't remember seeing a minimum listed, but for perspective, a 3 truck 1.6" scale Willamette takes a 13.5 foot radius, so for the Kozo geared locos, you should be good with a 7 foot or larger radius. This means that if you have a 14x14 living room, you could run one indoors in the winter! Or at Christmas, put the tree in the center of the room, and run the train around it.

Regards,

Doug

Not on coal I hope! Heh. Butane maybe.

[Postwarbob]

I have a Kozo 0-4-0 for sale very cheap. It needs finishing. PM me if your interested for the details Bob....................

[Kimball McGinley]

The old Little Engines (Lomita CA) catalogs had minimum radius listed for all the various locomotives. Anybody have a copy and willing to look up a 3/4" 0-4-0? Ought to be pretty similar...

[Ghettofab75]

I looked in my "old" catalog I got in the mid 90s and there was no mention of a 3/4 scale 0-4-0. It did list the minimum turn radius as 30ft for the 3/4 scale hudson and northerns however.

I doubt that helps though.

Kevo

[dampfmann]

Resurrecting this post. I am looking for an answer to the original poster’s question. I don’t see it answered in the thread. Also, what about locomotives such as a Hudson or Pacific? 3/4” scale. I am considering a small layout for my yard.

Thanks,

Marty

[Bill Shields]

A 3/4" hudson takes quite a large radius...not just for the drivers but for the leading and trailing trucks.

My little tom thumb 040 will go around a 20' radius but struggles to pull the tender and riding car without having them derail

[Andy R]

Kozo's 3/4" Engines or Similar:
My late father's elevated track had 17.5 ft radius curves.
The Kozo-designed Heisler negotiated that quite well.
The LBSC-designed 4-4-0 "Virginia" and the Bill Morewood-designed "Raritan" also traversed it with no derailments.
Andy

[Glenn Brooks]

As with the larger gauges, also consider how to loosen up the coupler jaws and widen the swing radius of the draw bar/ coupler shank between cars and the loco. Quite often folks only think about wheel base and turning radius of the drivers, when considering short radius curves.

However if the couplers have no clearance in the jaws, to allow vertical movement, cars can derail quite easily on un-even track. Similar problem if the couplers can’t swing wide enuf on tight turns...

Glenn

[James Powell]

3/4" Hoffman Hudson ran fine on 30' radius, as does my Britannia and Caribou. I'm planning around 30' for here.

The TSME and Hamilton tracks are both 30' radius. I think (ha) that Toronto Live Steamers was 22', and the Britannia went around that OK. I understand that Ted McJanet's home track was rather less than 30', and that the P7/President's had difficulty with it (Pacific's). I don't think my Brit ever ran at Ted's, and I know we never tried the Hudson.

30' seems a good radius for most 3/4" locos. As you get into smaller locos, I am sure you can go tighter. That being said, there is going to be a point at which the resistance will increase, or you will run into problems with stringlining, especially if you have 2+ cars. (and full sized passengers on the 2nd car...)

Gauge widening is important. The TSME (ex Art Ellis) track had been cut and an insert welded in each spacer it to increase the gauge at some point in the 70's. I understand the reason TSME was given the track was that Art thought it wasn't worth the work involved, and he had a 2nd lot made instead.

[dgmarklin]

I too was curious about the radius options a while back. I'm looking at engines similar to the Kozo 3.5" narrow gauge K27 so I went to the DRGW books I have. K36s were designed for as tight as 26 degree curves at 15mph, emergency speed of 25. That equals approximately a 222' radius. I'd assume a k27 can do the same, so scale it (.0972 ratio), and as long as the curves are 22' or more it should negotiate it. I was looking at doing somewhere along the lines of 25' to 30' radius for a minimum though.

I've googled map measured many tracks and found most UK elevated railways with 50 foot radius curves.

Additionally, Martin Evan's book list railway curves out for 3/4" engines at speed. Believe they were close to 50' radius.

Dean