A minimum radius for premium sector RTR

[34theletterbetweenB&D]

One of the problems with producing scale model locomotives and coaches is trainset curves. There are probably many hundreds of modellers using them for convenience and space reasons, but they are undoubtedly holding the hobby back at this stage of the game. If everyone moved out a little and adopted something like 24" radius minimum, it would at least give manufacturers of RTR and kits a bit more leeway...

This is definitely overdue, but the question has to be asked: if 'moving up' from the second radius point as the anchor that fixes RTR at second radius capable, what should be selected as the larger minimum radius?

 

This may of course only be a reflection of my own track laying skills, or lack thereof; but by experiment with the current generation of RTR, and my own kit builds with equivalent wheel standard running gear, I arrived at a 30" minimum radius for OO using current Peco streamline. This was measurably better, the smallest radius at which running became effectively perfect, by which I mean doing anything the real railway could, such as reversing a full size train slowly through a point network with no concern for a derailment.

 

It proved to have other advantages too: vehicle to vehicle spacings can be to scale with all the advantage that brings to appearance, track centres spacing can be scale for the 11' minimum of a pair of running lines, (although not tested against the longest contemporary stock as I have none) compromises like notches in cylinder heads to clear the swing of bogie wheels are unnecessary.

 

The real question though is just how much of the prospective customer base is lost if a model were produced to this standard? Anything more than 50% kills it stone dead would be my feeling.

[Bernard Lamb]

Ask FIA Trains?

36" has been regarded as "fine scale minimum" for kit and scratch built stock for as long as I can remember.

None of the big players have shown the slightest interest of going down that road so I can only assume that the sums do not add up.

Bernard

[Colin_McLeod]

People who use small radius track (no 1, 2 & 3) are either modellers without the space for larger radii, or else the train set market.  That is a lot of people to walk away from expecially when the competition would be very happy to take over.

[34theletterbetweenB&D]

I was expecting 36" when I started experimenting, from foolings around with EM and P4 in my finer scale yoof, but it appears that with the narrow gauge you can get away with 30". Very helpful for concealed trackwork.

[Michael Woolford]

Ask FIA Trains?

36" has been regarded as "fine scale minimum" for kit and scratch built stock for as long as I can remember.

None of the big players have shown the slightest interest of going down that road so I can only assume that the sums do not add up.

Bernard

Is that 36" over a certain distance? Surley a short length of tight track is managable; say for example at the end of a curved platform where it needs to tie in to the S&C.

[Andy Reichert]

Older tram protoype min radius for street corners is about 35 ft.  Modern flexibles, about 75ft.  Same radius works for prototype and models and fine or coarse standards. So a lot of realism ina small space.

 

Andy

[Richard Lee]

A 30" minimum radius seems achievable for more rooms than a 36" minimum radius, even if you allow space for transition curves.  My largest room is about 4 metres square, approximately 13' by 13'.  (Sadly, I can't have all of it, just a bit round a couple of walls.)  I had intended to use 36" minimum radius curves, but that would have really eaten into the space available.  Considering that the points that I used are nominally 36" radius, which means that they are a little tighter in part, 30" seemed a reasonable compromise.

 

There is no doubt in my mind that 30" radius curves are better for running than the sectional track radius 2 curves that I used on my first layout.  Improvements include the fact that varied types of tension lock coupleings for shunted goods wagons no longer cause derailments.  If you happen to use 0-4-4T locomotives for passenger trains, you can take them round bends, pushing or pulling, without the risk of wheel slippage.

[34theletterbetweenB&D]

This is really the point: what I see as the logic in a choice of a larger minimum radius is that it would enable the manufacture of an OO model uncompromised, other than by the enabling factor of the narrowed gauge to accomodate commercial wheels that is the OO compromise. That's what 30" minimum radius plain track appears to deliver in my experience. (The smallest points I use are the nominal 36" radius Peco medium and SMP plastic kit types, there isn't a 30" nominal radius OO point other than the curved Peco unit -unless someone knows differently.)

 

Is that 36" over a certain distance? Surely a short length of tight track is managable; say for example at the end of a curved platform where it needs to tie in to the S&C.

It all depends on the model, both from prototype characteristics, and the way in which the model running gear is designed. For example a vehicle like a coach with two x two axle trucks and no external features limiting the bogie swing will be untroubled, but an overall shorter CoCo or 0-6-0 could be in trouble if the all flanged wheelsets are constrained with only sufficient sideplay for the specified minimum radius; also wheels inside body work on the CoCo might foul, and in the case of the tender loco the scale spacing between loco and tender may limit their ability to swing sufficiently relative to each other.

 

Using the 30" minimum I have adopted, I would guess that provided the average radius is 30" in any 6 inch long section, then part of that curve could be as small as 24" radius. Not sure that would gain very much though, I would prefer to run the curve at a constant 30" radius

[woodyfox]

The main issue, regardless of geometric consideration, is that there are 2 types of consumer serviced by one type of major supplier.

The consumer that accepts the most compromise in terms of quality and accuracy are best catered for. The ones that demand more accuracy have to turn to small suppliers and all appear to accept (often quite gratefully) the lack of reliability and quality enjoyed elseware globally.