To regauge or not to regauge that is the question

[TippTrainLad]

Hello there, new here, currently entertaining the delusion of a new layout (or multiple) and was contemplating the purchase of the MM class 141/181 (missed the A class last time around), question for the more well informed would this model be suitable for conversion to 21mm or is it a bit to much of a hassel and better to start from new..... basically everything else will be kitbashed or  mangled in someway just nice to have somthing presentable in the early days as if the decision to regauge is to be made best to make it early just wondering if this could provide a stopgap anyway nothing set in stone  and any and all input and other good conversion suggestions welcome.

[Mayner]

The question of re-gauging really depends on whether you prefer to spend your time model-making/modifying models or prefer to spend your time running ready to run models. A lot depends on the track and wheel standard adapted P4 will require replacement of existing wheels with P4 profile wheels and potentially greater care in baseboard construction and tracklaying than the coarser standards, EM profile wheels should be used if you adapt EM running clearances, existing NMRA RP25 profile wheels fitted to the majority of rtr models are suitable for use with OO (Double O Gauge Association) running clearances. https://doubleogauge.com/standards/

The original version of the MM 141/181 was easy enough to re-gauge to 21mm gauge by replacing the existing axles and re-using the existing gears and wheels if you adapt OO running clearances, or with some thinning down of the bogie sideframes if you retain the existing wheels and adapt EM running clearances

Hand laying track and points takes longer than using Peco but can result in a more realistic appearance both in terms of track gauge and overall appearance of the track.

The IRM Bogie wagons can be re-gauged by moving out the wheels on the axles, the IRM MK2 Bogie coaches are designed for the wider 21mm gauge, but the axles/wheel sets may require replacement. Earlier IRM and MM and Provincial Wagons stock require modification to the chassis/bogies to run on 21mm gauge.

I have worked in 21mm gauge for over 30 years, but haven't gotten round to building a layout as I get most of my enjoyment out of building locos, stock and buildings and haven't really had time to build a layout. Most of my locos and stock are CIE/GSR steam era were built from kits and modifying ready to run not really an option in the first place.

If you are seriously considering re-gauging the first step would be selecting a wheel/track standard which largely determine the level of care/precision required in baseboard building and tracklaying, but also determine the minimum radius of curve feasible the more accurate the wheel/track running standard the greater the minimum radius required, I have successfully used a minimum radius of 30" using EM wheel profile/running clearances, adapting Double O Association standards may allow a small minimum radius.

Another approach is to mount the layout at or close to eye level and use a finer track like Peco Code 75 or Bull Head both of which are closer to scale in appearance than the standard Peco Code 100 track, the eye level view point distracts the eye from the appearance of the narrower gauge. Possibly what I would do if I was starting out with a blank canvas in 2024.

Edited March 15 by Mayner

[Brendan8056]

Like John I have modelled 21mm Irish for 30 plus years and would not go back to the very narrow 16.5mm.  I have just worked out how to easily re-gauge the NIR coaches just released (where fitted with the Irish bogie). A small vice, an object to hammer with and a wheel gauge to make sure it is correct. The result is in the picture, one wheelset  at correct 21mm gauge. I had to remove the brake blocks/links but otherwise all runs freely.

For anyone new to Irish Railway modelling it is the easiest ever to model the correct gauge, of course you can still kitbash, scratchbuild and modify, that is the fun side of it.

[Galteemore]

Totally agree Brendan. It’s 7mm scale for me so pretty much all scratch but that 5’3” look is worth it and nowhere as hard as you might think.

[Horsetan]

40 minutes ago, Brendan8056 said:

Like John I have modelled 21mm Irish for 30 plus years and would not go back to the very narrow 16.5mm.  I have just worked out how to easily re-gauge the NIR coaches just released (where fitted with the Irish bogie). A small vice, an object to hammer with and a wheel gauge to make sure it is correct. The result is in the picture, one wheelset  at correct 21mm gauge. I had to remove the brake blocks/links but otherwise all runs freely.

For anyone new to Irish Railway modelling it is the easiest ever to model the correct gauge, of course you can still kitbash, scratchbuild and modify, that is the fun side of it.

Not workable for those using P4 profile wheels, unfortunately. Requires new wheels bushed down to take the 1.5mm stub axles, and quite likely longer insulating muffs to prevent the wheelset going wobbly.

[Mayner]

B141 conversions using original Bachmann wheels top photo, Ultrascale EM profile wheels lower photo.

It was necessary to thin down /reduce the thickness of the Bogie sideframes using the Bachmann wheels with the  wheel Back to Back measurement set at 19.3mm based on EM running clearance, there is sufficient clearance and no need to reduce the thickness of the sideframe when using EM profile wheels available from Ultrascale or Gibson. Ultra scale supply 21mm gauge wheel sets to order in both P4 & EM profiles, better wheel than Gibson but longer lead time to delivery.

I used 26mm plain axles available from a local supplier for the Bachmann Conversion

Setting up Ultrascale wheelset with Bachmann axle brushes and gear, the top hat brushes between axle brush and wheel are basically spacing washers to minimise side play. The steel object is a Back to Back gauge bought from TMD the predecessor of Studio Scale Models ,many moons ago.

The Crude Hornby but it works old type Stanier bogie converted to 21mm gauge

Piece of .60 Thou plasticard used as replacement bolster.  2mm bore brass tube used to sleeve standard axles cut in half, wheels are PC Models a long discontinued brand bought at a clearance sale about 30 years ag.

Same principal but more sophisticated. MJT "Suspension Units" packed out to accept 21mm gauge wheel sets used under a Laminate coach assembled using a Worsley Works set of parts. Wheels appear to be Gibson EM profile wheels on locally sourced 28mm pin point axles.

Purpose design of 21 or 16.5mm gauge  Studio Scale Models GSR Bredin Coach.

Dapol ESSO Tank wagon. Solebars packed out to accept 21mm wheelsets. Similar principal used to convert Parkside BR Van and Pallet Wagon to 21mm gauge Irish models

 

[David Holman]

Nobody should think 21mm gauge requires P4 standards. 00/EM finescale (ie existing wheels) should be fine. However, do not expect to use sharp radius curves or points - they will need to be at least 3 foot radius, unless you are using short wheelbase stock and even then two feet will be pushing it.

 Also, while modern diesels seem easy enough to convert, steam outline models are not.

[Mayner]

David put it succinctly 21mm gauge can be laid to OO/EM profile wheels and running clearances, but not really suitable for sharp/small radius curves (I use 2'6" as a minimum on plain track) and points need to be at least 3' radius.

Its important to understand that EM/OO fine wheels are to a finer/narrower profile to wheels fitted to RTR locos and stock and importantly that critical dimensions such as wheel Back to Back and Flangeway Clearance vary between EM and Double O Association Intermediate Track and Wheel Standards.

I use EM profile wheels set with a Back to Back of 19.3mm for the majority of my locos and stock with a Flangeway Clearance of 1mm while Brendan 8056 uses existing (NMRA) profile wheels with the B-B set at 19mm presumably with a wider flangeway clearance.

It was necessary for me to reduce the thickness of the bogie sideframes of  a B141 re-gauged with the original Bachmann wheels as the wheels rubbed on the sideframes with the B-B set to 19.3mm. Clearance between wheels and side frames was not a problem on my B141s fitted with narrower EM profile wheels.

While diesels and stock are relatively simple to re-gauge, a 21mm gauge steam outline loco is basically a scratch or kit building exercise in sheet metal due to the very tight clearances between wheels, splashers, outside cylinders/valve gear on the full size locomotive. 

I think Stephen or Fran from IRM/Accurascale pointed out that it was not practicable to produce an EM gauge variant of the Accurascale GWR Manor due problems achieving sufficient clearance given the characteristics of the material used, on of the reasons British OO exists.

Edited March 17 by Mayner