Has anyone ever attempted working outside frames?

[mike morley]

I have two kits nearing the top of my "to do" pile.

One is a Blacksmith's Barnum (Possibly the last one ever made) that came with a chassis that is primitive to say the least, being made from thick slabs of brass with no provision for any form of suspension and cut-outs for a Triang X04 motor.

The other is a narrow gauge engine with a chassis intended for 14mm gauge, while my narrow gauge interests are in 12mm.

 

Rather than scratchbuild better replacement chassis for them I am considering (and the word has to be emphasised ) turning the cosmetic outside frames into working versions.

 

I suspect that the main problem is simply that they are intended to be cosmetic.  Beefing them up ought to be reasonably straightforward, but will the need to incorporate hornblocks cause problems?  I have a niggling suspicion in the back of my mind that it will, without quite being able to put my finger on why.

And how about the hornblocks themselves, bearing in mind that they would be far more visible than on an inside-framed loco?  Those that are intended to look the part as well as act it are, after all,

intended for use with inside frames.

The need for a neat seam along the joint between the frames and the footplate makes me feel it would be better to make the footplate part of the chassis, rather than the superstructure.  I don't see a problem with that, but that doesn't mean there isn't a problem I simply haven't foreseen.

 

Your thoughts, please.

[John_Hughes]

I think I remember Adrian Tester in his 4mm days working on a double-framed Kirtley Goods (but it may have been something else!) with working hornblocks in both the inner and outer frames (and probably working inside motion as well!); given his skills I presume it worked out, but I haven't bumped into him for a while now, and he's been in 7mm for years. Either way, I'm pretty sure that that nicely curved footplate was indeed part of the chassis.

 

And didn't Denis Allenden do something similar with his beloved Cramptons? I suspect that there were articles about them in the old MRN years ago, but that would have been in 7mm too

 

Like you, I can't see any reason why it ought not to work; but then, I tend to blunder into these problems all too often and end up putting projects on one side until a solution occurs, sometimes years later!

[34theletterbetweenB&D]

...Beefing them up ought to be reasonably straightforward, but will the need to incorporate hornblocks cause problems?  I have a niggling suspicion in the back of my mind that it will, without quite being able to put my finger on why...

 The great challenge wiill be the thickness of the working outside frame hornblock assemblies which have to be outside the wheelfaces. Those hornblocks will in turn define where the outside frames have to be positioned. The stack up - moving outwards - from the wheelface plus any side play allowance for the wheelset, hornblock thickness, position of the outside frame defined by the hornblock, outside cranks and crankpins; will demand scale thickness parts if the width is not to expand well beyond scale over both the frame faces, (which might otherwise lie outside a scale width footplate) and the crankpins and rods, which might well go out of gauge.

 

A solution might be to put the working hornblocks on the inside frames as usual, and free moving but non-loadbearing hornblocks simply riding on the axle ends - which can thus be scale thickness - in the outside frames.

[PatB]

Whilst I haven't tried to do this, so any advice I can offer is to be taken with a degree of scepticism, as an engineer I'd agree that it would be a good idea to attach the footplate to the top of the frames, not just for a neater seam but also to provide a more structurally sound shape.

 

I'm assuming you're working in 4mm, in which case, if you're building to 00 rather than EM/P4 you've got some extra room to play with, which the forefathers of the gauge cursed us with helpfully designed in for similar purposes . Presumably the narrow gauge kit also has a certain amount of fat in it, given that you have a 14 mm gauge chassis kit and will be regauging to 12 mm.