P4: 3' Radius with Gauge Widening OK?

[Lacathedrale]

Sorry for the rather small question - I realise having gone back over a templot plan for a future layout that the minimum radius is not 4', but 3' - and there's no way at all to get around that in the space I have available. I had/am considering building this in P4 over EM or 00, but clearly this might be a problem.

 

I see that Exactoscale supply gauge widened track bases, and of course it can be done with a triangular gauge too - but I'm just wanting to confirm that small, pre-group locomotives  (2-4-0, 4-4-0, 0-6-0, inside valve gear, etc.) will be able to handle this without undue concern?

 

EDIT: This page suggests a 0.2mm gauge widening should be sufficient for a three axles if no endfloat is possible at 900mm: https://www.scalefour.org/forum/viewtopic.php?t=5030

 

Edited December 2, 2021 by Lacathedrale

[johndon]

With small locos like that you would likely be OK depending how much side play there is in the wheels.

 

I believe that, if built with the relevant side play, even Dave Bradwell's 9F 2-10-0 chassis can make it round a 3' curve in P4.

[Stephen Freeman]

The minimum radius is perhaps slightly misleading. A turnout will/should have various radii in it. The minimum radius is usually over a short section, that's why commercial turnouts quote an overall radius as there will almost certainly be a small part with a small radius.

 

The only way to know if a loco etc will go through OK is to test it as all depends on how much sideplay etc has been built into the chassis/valve gear. The real problem arises with outside cylinder locos and stock with restricted side play (especially bogies), so you may be OK.

[Izzy]

I have always made it a policy that any loco I made/converted to P4 would easily traverse an A5 crossover. This is to ensure that whatever they run on they should be able to cope. A 'standard' A5 in templot with REA switch has a radius of 31". I don't build the pointwork with gauge widening (although using a 3-point gauge would no doubt help) and find that it is only really longer wheelbase types that need extra care with construction to go through. Most normal locos of the type described will be fine even without any GW. But I do tend to allow a modicum of sideplay with all my chassis whatever.

[Gordon A]

Inside valve gear will restrict any side play on that axle.

When converting locos or building chassis you need to ensure that there is sufficient side play and clearances in the splashers.

Are you talking about the minimum radius on plain track or in points as well.

Building a section of test track including a point to 3 foot radius may answer your question.

On plain track consider following the prototype approach by fitting a continuous check rail.

 

Gordon A

[Lacathedrale]

Buliding a section of test track is a great shout. I am not planning on modelling inside valve gear, rather simply that I don't need to worry too much about outside valve gear when it comes to side-play, just connecting rods and splashers/steps/etc.

 

 

[Siberian Snooper]

Tim Venton's Clutton has 3 ft radius return curves on it in P4.