January 2020 Workshop

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David Thorpe
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January 2020 Workshop

Postby David Thorpe » Sun Jan 12, 2020 4:12 pm

It's been a long time siince I last posted anout our monthly workshops, but it's still the same old crowd coming along to them. Unfortunately Colin Stephenson was unable to attend our most recent workshop, but the rest of us were here.

John Duffy was weathering and fitting glazing to his GNSR "R" class 0-4-4T loco. It's an O gauge model and looked very good indeed in 1947 LNER black livery which John was subtly and effectively weathering with a small variety of powders.

Peter Heald, true to form, was working on a couple of wagon kits, a Cambian Models M.R. van and a Colin Ashby GCR open.

David Jolley has for the moment abandoned the NSR and is building a new layout based onr Lauriston on the NB's Montrose & Bervie Railway. He was working on the station building, using bass (lime) wood for the main structure.

Tony Wickes, who invariably brings along extremely comples GWR kits, did not disappointon this coccasion. He is building a Southwark Bridge kit of a GW 4-wheel brake van. It appears to be incredibly detailed and fiddly, fully justifying the 15-page instruction booklet.

I started the Caley Coaches 57' brake composite kit I got for Christmas. Rather reluctantly i followed the instructions and started with the bogies which are of a torsion-wire type that I generally hate building. These were no exception but at least I have got the coach itself to look forward to.
UPDATE: The said torsion type bogies are now in the bin. Fortunately I've got a set of suitable Bill Bedford ones to replace them although I do think that far too much emphasis is put on compensating/springing short wheelbase bogies in P4 - my Bachmann coaches running on their Bachmann bogies run perfectly satisfactorily..

DT
Last edited by David Thorpe on Mon Jan 13, 2020 8:51 am, edited 1 time in total.

Terry Bendall
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Re: January 2020 Workshop

Postby Terry Bendall » Mon Jan 13, 2020 8:31 am

I think it is always useful to hear what area groups are doing and there are often useful snippets of information to pick up.

David Thorpe wrote:I do think that far too much emphasis is put on compensating/springing short wheelbase bogies in P4 - my Bachmann coaches running on their Bachmann bogies run perfectly satisfactorily.
.

The perceived wisdom in the early days of modelling to P4 standards was that everything needed some sort of compensation/springing. I think experience has shown many people that short four wheel wagons and bogies on coaches and wagons of RTR stock can usually be made to run without either. If it works to your satisfaction then don't change it. :)

Terry Bendall

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Le Corbusier
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Re: January 2020 Workshop

Postby Le Corbusier » Mon Jan 13, 2020 9:47 am

Terry Bendall wrote:The perceived wisdom in the early days of modelling to P4 standards was that everything needed some sort of compensation/springing. I think experience has shown many people that short four wheel wagons and bogies on coaches and wagons of RTR stock can usually be made to run without either. If it works to your satisfaction then don't change it. :)

Terry Bendall

Presumably this relates primarily to the conversion of RTR stock? When building a kit or from scratch it is often as quick and easy to spring/compensate if that is what things are set up to do ?
Tim Lee

Philip Hall
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Re: January 2020 Workshop

Postby Philip Hall » Mon Jan 13, 2020 8:36 pm

Tim,

Yes and no. I would not contemplate building a chassis for an engine that wasn’t compensated (or sprung or whatever you prefer) as getting it to sit absolutely flat on a surface plate is difficult. It doesn’t matter quite so much with EM as the flanges are a bit deeper than our turning burrs. A commercial chassis also has the kind of slop we would never entertain, which to some extent is why they work. Some commercial chassis are also not as dead true as you might think, so the EM flange thing applies here as well.

I am going to test this theory at some point because a rigid chassis fitted to a GWR 44XX (in 00) which I built for a friend some years ago has come back to me to run on my own railway, and I have no intention of taking it completely to pieces when it runs so nicely. That one is going to be a rigid conversion!

However, short wheelbase bogies and wagons are another thing, and I quite happily build some of these rigid, and they work well. The important thing, as always, is that the wheels are round and therefore don’t introduce any wobble or instability. RTR bogies and wagons are usually moulded true and square, so like Terry and David, that’s the way I go, albeit with a decent amount of weight - 50g at least for a wagon, 180g for a carriage.

Now before anyone says they don’t need to be that weight, especially if they are sprung, maybe, but weight and true wheels works for me and my vehicles glide around solidly. They react like heavy vehicles because they are heavy - like the real thing. Springing is nice to have, and vehicles look and feel nice as they go around, but I don’t think it’s essential.

Philip

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Noel
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Re: January 2020 Workshop

Postby Noel » Tue Jan 14, 2020 11:31 am

As one who commonly builds rigid vehicles I would add that a bogie wheelbase is no longer than that of a 10ft wheelbase wagon, and is often significantly shorter, so individually bogies are no more intolerant of local variations in the track than such a wagon. Bogie vehicles, however, may be much more affected by track defects, including changes of gradient, or twisted track, than shorter vehicles. It is advisable to ensure that one bogie can move in relation to the other [or that both can move in relation to the body, in which case the movements of the bogies will need to be separately constrained in direction, to prevent the body moving in an uncontrolled fashion]. Vehicles with sprung bogies may be less vulnerable than ones with rigid bogies, but the shorter the bogie wheelbase, the less the advantage derived from springing, potentially.

I'm not intending to advocate against springing in any way; I think there is very little doubt that it is better than compensation for longer wheelbase vehicles, and I know that the physics doesn't scale, but on BR springing didn't have the effect it does on the model. A Dogfish for example weighed roughly 35.5 tons loaded, 11.5 tons empty, a fitted Mermaid roughly 25T loaded and 11T empty. I once saw a train of mixed Dogfish and Mermaids, all empty, being accelerated through a station; the loco was running smoothly, as was the 25T SR bogie brake on the back. Everything in between was hunting and bouncing, and making quite a lot of noise in the process. Impossible to recreate in a model, of course...
Regards
Noel


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