Murphy Models 141/181 21mm re-gauge and pointwork

[Mayner]

I thought it would be useful to add a re-gauge of the MM Baby GM and and a comparative space required for pointwork in OO and 21mm gauge.

My 21mm gauge work is based on using EM profile wheels and running clearances (back to back 19.3mm) which is a good compromise between S4 and OO wheel profile and running in terms of a trade off between appearance and ease of use.

Murphy Models B141 with OO/EM profile wheelsets with 19.3mm back to back gauge. Wheels fit within the MM bogie sideframes without modification.

The wheels and 21mm axles were supplied as a custom order by Ultrascale.

B141 re-wheeled with original Bachmann wheels and new axles. It is necessary to reduce the thickness of the Bogie Sideframes by grinding/filing to re-gauge the model to 21mm using the original wheels to 21mm gauge with a 19.3mm b-b.

Brendan of this parish gets around this problem by setting the back to back to 19mm and presumably using OO gauge running clearances.

I body mounted the Kadee's on my baby GMs by removing the coupler pockets from the bogies and gluing to the pilot infill panels supplied with the MM models.

A direct comparison between a 21mm and OO gauge crossover. The A switches and No 6 crossing angle is pretty much minimum the minimum for main line locos and stock in sidings and secondary trackage when working to EM or S4 standards.

The 21mm gauge crossover is 500mm long the OO Gauge using Peco small radius points 370mm

The OO gauge Timesaver layout and traverser fiddle yard occupies a space 2300mm long, I was unable to fit a similar layout with a fiddleyard and run round loop in the same space in 21mm

The original 2012 dock layout.  The inspiration was the North Wall Granaries area with the Dock lines straight a small marshalling yard for dock traffic on the left with the main running lines curving around past industrial buildings to another yard depot.

The main problems were that I could not get the double slips to work and that I did not allow enough clearance between the yard tracks on the left and the running lines.

Visually the abrupt transition from straight to curved track did not work, operation was likely to become tedious as I could not stage trains off line without a fiddle yard.

 

 

 

 

 

[murphaph]

John, what is the wheel profile of the wheels you supply with the brake vans? You may be pleased to hear that the very first item of regauged stock I own is one of your brake vans  I'm using it to push through my first set of 21mm points. I'm using P4 gauges (roller and triangle types) so true 21mm between the rails and at present just judging the flangeways by eye as I practice my technique. I have your turned brass back to back gauges as well as a 3d printed gauge supplied by EDM Models, all 19.83mm.

I'm wondering is it worth replacing the wheels on the baby GMs with EM gauge (I don't intend going as far as P4 throughout as I think I'd regret it on the large layout I have planned). What is the profile of the original Bachmann wheels? The brake van wheels strike me as being a bit narrower and thus maybe not requiring the filing back of the baby GM bogie side frames?

 

[Noel]

10 hours ago, Mayner said:

I thought it would be useful to add a re-gauge of the MM Baby GM and and a comparative space required for pointwork in OO and 21mm gauge.

My 21mm gauge work is based on using EM profile wheels and running clearances (back to back 19.3mm) which is a good compromise between S4 and OO wheel profile and running in terms of a trade off between appearance and ease of use.

Murphy Models B141 with OO/EM profile wheelsets with 19.3mm back to back gauge. Wheels fit within the MM bogie sideframes without modification.

The wheels and 21mm axles were supplied as a custom order by Ultrascale.

B141 re-wheeled with original Bachmann wheels and new axles. It is necessary to reduce the thickness of the Bogie Sideframes by grinding/filing to re-gauge the model to 21mm using the original wheels to 21mm gauge with a 19.3mm b-b.

Brendan of this parish gets around this problem by setting the back to back to 19mm and presumably using OO gauge running clearances.

I body mounted the Kadee's on my baby GMs by removing the coupler pockets from the bogies and gluing to the pilot infill panels supplied with the MM models.

A direct comparison between a 21mm and OO gauge crossover. The A switches and No 6 crossing angle is pretty much minimum the minimum for main line locos and stock in sidings and secondary trackage when working to EM or S4 standards.

The 21mm gauge crossover is 500mm long the OO Gauge using Peco small radius points 370mm

The OO gauge Timesaver layout and traverser fiddle yard occupies a space 2300mm long, I was unable to fit a similar layout with a fiddleyard and run round loop in the same space in 21mm

The original 2012 dock layout.  The inspiration was the North Wall Granaries area with the Dock lines straight a small marshalling yard for dock traffic on the left with the main running lines curving around past industrial buildings to another yard depot.

The main problems were that I could not get the double slips to work and that I did not allow enough clearance between the yard tracks on the left and the running lines.

Visually the abrupt transition from straight to curved track did not work, operation was likely to become tedious as I could not stage trains off line without a fiddle yard.

 

 

 

 

 

Beautifully made 21mm trackwork. Sublimely precise and authentic looking

[Mayner]

1 hour ago, murphaph said:

John, what is the wheel profile of the wheels you supply with the brake vans? You may be pleased to hear that the very first item of regauged stock I own is one of your brake vans  I'm using it to push through my first set of 21mm points. I'm using P4 gauges (roller and triangle types) so true 21mm between the rails and at present just judging the flangeways by eye as I practice my technique. I have your turned brass back to back gauges as well as a 3d printed gauge supplied by EDM Models, all 19.83mm.

I'm wondering is it worth replacing the wheels on the baby GMs with EM gauge (I don't intend going as far as P4 throughout as I think I'd regret it on the large layout I have planned). What is the profile of the original Bachmann wheels? The brake van wheels strike me as being a bit narrower and thus maybe not requiring the filing back of the baby GM bogie side frames?

 

The JM Design wagons use Markits blackened brass wheels on 28mm pin point axles to simplify conversion to 21mm Gauge, the wagon chassis are designed with enough room between the axleguards to re-gauge the wagons to 21mm gauge with the existing wheels set with a maximum back to back of 19.3mm.

Markits wheels are closer in profile to the NMRA RP25 110 wheels used by Chinese rtr manufacturers than the finer OO/EMf profile used by other British manufacturers such as Alan Gibson Works and Ultrascale

You may have difficulty in achieving reliable running through pointwork with NMRA Code 110 or OO/EMf wheels set with a B-B set at 19.83mm which is very close to the min B-B for 21mm gauge built to P4 Standards.

It may be a better option to follow Brendan Gashes example and reducing the B-B to 19mm and adapting Double O Gauge Association https://doubleogauge.com/  Intermediate or Fine Standards to 21mm gauge may be a better option to achieve reliable running without having to replace existing RP25 110 wheelsets used in the current generation of high quality rtr models.

The biggest challenge is developing an Irish Broad Gauge track system that appealing enough for the 'average" Irish modeller to consider adapting the wider gauge, developing an "Irish OO"  possibly at 20mm or EM gauge rather than 21mm with OO running clearances would both allow the modeller to build a layout within a smaller space than a layout built to P4 or EM standards without the expense of having to replace the excellent NRMA 110 wheels used with the majority of Irish rtr stock. The slightly narrower gauge both eliminates the need to modify the bodies and chassis to fit broad gauge wheel sets and like OO provides additional running clearance or slop to allow models to run round smaller radius curves than practical in P4 or EM

Using P4 or EM profile wheels was and largely still is the only workable option for steam outline locos in 21mm gauge both as a result of difficulty in achieving adequate running clearance for driving wheels in the majority of Irish steam locos with low running board and splashers and the prohibitive cost of comissioning Markits to produce a 21mm driving axle for their excellent all metal loco driving wheels.

Three of the four British 'fine scale" wheel manufacturers adapted different profiles for OO/EM wheels Markits (formerly Romford) appear to have continued with wheel profiles adapted by the EM Gauge Society and an industry association in the late 1940, Brian Rodgers the founder of Ultrascale developed a finer EM profile in association with Pendon Museum during the 1960s which was later adapted by the EM Gauge Association and currently commercially available through Ultrascale and Alan Gibson Works, Mike Sharman an engineer and esoteric modeller developed an excellent range of finescale driving wheels during the 1970s his OO/EM wheel has a narrower thread than the Markits, Gibson and Ultrascale as a result of which I set the B-B at 19.5mm to achieve reliable running in 21mm. 

The majority of my steam locos are fitted with Sharman wheels at the time very attractive for 21mm gauge as the wheels were supplied with an axle long enough for GWR 7' gauge, you simply cut the axle to length for OO,EM,S4 or 21mm gauge.

[murphaph]

The path of least resistance (and cost) is definitely to adapt the B-B gauge so I can use the NMRA 110 wheelsets as provided by IRM etc. I don't have a problem with the out of scale tread width/flange depth and it's a lot of expense to re-wheel everything for something that doesn't bother me in the first place. It's the out of scale track width only that bothers me about 00. I don't even particularly mind the overscale flanges in pointwork in 00.

I'm going to build my track to 21mm with the P4 gauges and EM tolerances for point etc. flange widths. Then I will see how the NMRA 110 wheelsets handle the track at different B-B's. If the check rails are too tight, I will ease them out to closer to 00 clearances I suppose.

It's good to know your Markits wheels are NMRA 110 25 (or close) as that's my test bench right now (using 19.83 B-B for the moment, but we'll see if that stays like that)

[David Holman]

 While I applaud anyone willing to use P4 standards, I also fear it is the biggest barrier to more folk going broad gauge. Irish EM, or similar is as Mayner says, a far more pragmatic approach. You can do 4mm fine scale, without needing P4 wheels or clearances, as Andy Cundick has shown with Valencia Harbour.

 My Fintonagh model, though 7mm scale, used 21mm track and 4mm, finescale clearances, which means  one millimetre flangeways in the point frogs/crossings. In other words, exactly the same clearances as on Peco code 75. I use standard 4mm wheels too.

 EM gauge track is less than 0.7mm narrower than 'dead scale', but looks so much better than 00, especially using code 100 rail. Irish EM, which Templot has track plans for on line, is 20.2mm, clearly light years better than 00, even with code 75 track.

 I can certainly understand why folk would want to stick with 00, especially if there is lots of stock and a big layout already available. Equally, with new models, especially diesels, easily converted to 5'3, along with innovations in 3D printed track bases, the time has never been better to convert - especially if you are planning a new project.

 Come on in - the water's lovely!