ABS GW coach bogies and how to spring them?

[chrisf]

I have some unassembled kits made by ABS for GWR 9 ft wb pressed steel bogies. What makes them stand out from other representations is the correctly modelled end frame, comprising a bow shaped girder with holes. Forgive me for not knowing its proper name! As I offer up the parts to unmade springing units of various designs I ponder how they could be married together without causing serious and destructive damage. I wonder if I might pick the brains of the collectied wisdom. Has anyone here attempted to spring these fine bogies?

Chris

[Mike Garwood]

Chris
Having just built a pile of 9 ft bogies, I never thought of ABS for the castings...any chance of a photo? I used Bill Bedford and Justin Newitt bogies (http://rumneymodels.co.uk/7.html) for my collection of vehicles (4 * D117 ).

Mike

[Tim V]

Chris

Are you sure it's worth the bother? Some coaches run very well with no springing.

[martin goodall]

Tim beat me to it. I was going to say exactly the same thing.

But it helps to arrange one bogie so that it can tilt laterally, and to mount the other bogie so that it can't do that. This will eliminate any tendency to wobble. It is a very crude (but nevertheless effective) form of three-point suspension.

[Russ Elliott]

Chris - what do you estimate the distance between the sideframes is? IIRC, ABS bogie sides are quite thick.

[chrisf]

Good morning gentry! I am gratified by the level of response to what was potentially a silly question.

Mike G - I'll see if I can rustle up a photo later today. Meanwhile, if you have access to volume 1 of Stephen Williams's book on coach building, there are pics of the pressed steel bogie around page 15 with illustrations of the prototype nearby. I have a small stash of Bill Bedford bogie frames and look forward to trying out one of Justin's in due course.

Tim and Martin - the simple answer is that I don't know yet if it is worth the bother. Yes, some coaches do run very well with no springing and I know that Tim's experience with it has not always been happy. Others have had good results. Some people have better track than others, I guess.

Russ - you might be on to something. The approximate length of the end stretcher - the proper name for the girder with holes in that I could not bring to mind yesterday - is 24mm. So, of course, is the inside distance between the sideframes of a BB bogie. As you say, the ABS bogie sides are quite thick, even chunky, approx 2mm plus details. This would give the advantage, if advantage it be, of added weight low down, but against this I guess that drastic thinning would be needed to keep the overall width close to scale. I suppose I'm hoping that there is a method of springing which would not necessitate major surgery to the ABS castings.

Chris

[grovenor-2685]

I suppose I'm hoping that there is a method of springing which would not necessitate major surgery to the ABS castings.

IIRC Masokits have one with inside bearings for this sort of problem, but you would have to accept the increased rolling resistance.
(Item 9.01, page 6 of his catalogue)
Keith

[Russ Elliott]

Chris - looks like you've got three options:

- Lengthen the bearing holes downward in the ABS sideframe into a slot, and use a couple of phosphor-bronze wires bearing down on the axles between the wheelbacks (this would be 'spring-assisted'). The rolling resistance of this is not as much as an internal bearing system.

- Put an inside bearing system in, say Peter Denny or Maso.

- Thin down the ABS sideframes to cope with an outside sprung system. A BB frame will require at least 24.9mm clearance, and the B4 type is probably the most useful, being IIRC the shortest (54mm??) he does. The endframe shape of the BB unit will not match the ABS bow-shaped girder, so some major surgery will be required to get them to match.

Whatever you choose, even if doing nothing, the overall width of these bogies will always be problematic. At 24mm between ABS frames, and say 1.5mm each to the outside of the frame, gives 27mm, say 80+". The prototype frame was 70" over plates.

[John Fitton]

I have assembled the ABS parts onto MJT compensated units with 100% success, cutting the end frames so the MJT unit functions properly. I agree that the end mouldings look very nice, although breaking the 3 foot viewing rule is necessary to see them. The main difficulty is the bolster springs: very fiddly to get them to work. I used them under a pair of Lima Siphons. The extra weight helps them ride beautifully. I left the brakes off.

JF

[chrisf]

As promised and requested, here is a photograph of the key components of one bogie.

ABS bogie.jpg

The example illustrated has the shorter style of bogie steps, making it equally suitable for a parcels van such as the Siphon G and a Centenary coach. The distinctive end stretchers are at left and right and I would prefer not to sacrifice them. Note how thick the sideframes are! The kits are listed in the ABS catalogue as "Coachmaster" and I hate to think how old they are but clearly they predate most modern thoughts of compensation or springing.

Thanks to all who have contributed advice so far!

Chris

[Andy W]

I expect you've considered this approach, but you could try fixing one side to a central spacer while pivoting the other to it thus creating 3 point compensation. Then, as Martin said, if one bogie can rock laterally and the other can't it might just do the trick.

[grovenor-2685]

The main difficulty is the bolster springs: very fiddly to get them to work.

Not surprising since the ABS bolster springs appear to be solid whitemetal and the MJT units are, as you said, compensated not sprung. Am I missing something here?
Regards
Keith

[Will L]

I trust you have noticed the Bogie Design thread which has also just sprung back to life.

Will

[Philip Hall]

I have recently had some Rocar (Rodney Cooper) P4 GW carriages of 1990s vintage in for minor repairs, and these seemed to have exactly the cast metal bogies you illustrate. They are unsprung, and I can say that they ride beautifully. Two observations: the wheelsets are perfectly concentric, and they are extremely heavy, about 240 grams.

I actually visited Rodney last week, and thought to ask him about this in the light of the repairs I had carried out, and found that his current standard is for a sprung bogie of his own design, which is for the bogie frame to be sprung to the bolster. I think a rigid version of this frame is available from Comet. In some cases, I believe, he has also sprung the wheelsets. Again, all these ride perfectly and are very steady.

I think the simple solution is for a rigid bogie, possibly with slightly thinned sideframes, with the form of three point suspension that Martin describes. With gangways sprung against one another, and sprung buffers and couplings, there should be no wobble and the whole train would move as one and be quite steady. I quite like the idea of springing the frame, though, and will have to give this a try some time when a suitable vehicle presents itself.

Philip

[John Fitton]

The main difficulty is the bolster springs: very fiddly to get them to work.

Not surprising since the ABS bolster springs appear to be solid whitemetal and the MJT units are, as you said, compensated not sprung. Am I missing something here?
Regards
Keith

Sorry Keith, my error: I really meant to say it was difficult to assemble the bolster springs onto the MJT brass structure.

JF

[Mike Garwood]

Chris
I reckon you could adapt a pair of Bill's sprung bogies to accommodate those castings, without too much stress. There must be a bout a 2mm over hang from Bills bogie to the end of the Comet casting - the casting is longer by, is what I'm trying to say.

regards

Mike

[chrisf]

That's better. I tried to post a reply earlier but got booted out by an error message. Now what was I going to say? Ah yes ...

Good afternoon and thank you all for the continuing responses. They certainly show that there is more than one way to skin a cat!

Obviously the simplest way to proceed is to agree with Philip, whose thoughts are backed by considerable experience, and go with rigid bogies, one of which would be allowed to rock and roll to give a form of three point suspension. I'm not at all sure that I want to go with any form of MJT style compensation, since I wish to retain the distinctive, elegant and even ornate end stretchers, noting carefully the point made by 'jf2682' about the three feet rule. Will L has pointed to the bogie design thread where we are reminded that Peter Denny made inside springing work almost 60 years ago - and, of course, Mike Clark more recently as Russ suggests but with the caveeat of rolling resistance.

Mike G - I offered up the relevant castings to a BB frame. This has possibilities if I can bring myself to accept that the cast end stretcher may not go quite where it should without a bit of surgery to the etch. If it does go where it should the brakes on the BB etch would have to be redesigned, replaced or omitted but look, there comes the three feet rule again!

I am moderately alarmed by Russ's point about the width of the bogies as cast but I guess that we have to live with this given the widespread use of castings on bogies - unless we are clever enough to etch our own. (I'm not!) Let's keep the lid on that particular can of worms for now!

All contributions very gratefully received

Chris