Carriage ride height and springing

[David Thorpe]

Just as a matter of interest, you replaced the supplied D&S bogies with some rather complicated fully sprung ones. Did you ever assemble the D&S bogies and, if not, would it be worthwhile building one to see if it gives you the correct ride height?

DT

[Noel]

I wonder if part of the problem might be that the secondary springs are bend too close round the anchor points, making the spring stiffer? Here's the arrangement I've had until now, with the springs (not trimmed) bent hard up against the anchor points:

Probably. Springs have to be able to deflect, which affects the geometry of the spring. If held tightly at both ends, then in effect you have a rigid bar, which won't provide any springing at all. I'm not suggesting that you have that situation with your original set-up; there will be some movement, but probably very limited. If I've got the physics right [definitely not guaranteed] then the spring stiffness isn't affected, but its travel is.

[Daddyman]

Just as a matter of interest, you replaced the supplied D&S bogies with some rather complicated fully sprung ones. Did you ever assemble the D&S bogies and, if not, would it be worthwhile building one to see if it gives you the correct ride height?

DT

That's a very good idea, David, thank you. One of the carriages came part built/part wrecked from ebay, so I still have the bogies, and one of the carriages still has the original D&S base-plate. This is certainly worth a try. However, I'm thinking - and Noel confirms me in this (thank you, Noel) - that the way I have set up the secondary springs is not helping; my jig (or more properly "gauge", I suppose) shows me that on the clerestory at least, where there is more weight as a result of the metal roof (145g to the Dia 127's 125g), the primary springs are now right, so the secondaries are the issue now. The first solution I will try, though work is busy this week, is to lengthen the secondaries by 1mm or so in the way mentioned in my last post; if that doesn't work, the 7-gauge strings should arrive today.

Thanks again to all!

[Will L]

Just as a matter of interest, you replaced the supplied D&S bogies with some rather complicated fully sprung ones. Did you ever assemble the D&S bogies and, if not, would it be worthwhile building one to see if it gives you the correct ride height?

DT

That's a very good idea, David, thank you. One of the carriages came part built/part wrecked from ebay, so I still have the bogies, and one of the carriages still has the original D&S base-plate. This is certainly worth a try. However, I'm thinking - and Noel confirms me in this (thank you, Noel) - that the way I have set up the secondary springs is not helping; my jig (or more properly "gauge", I suppose) shows me that on the clerestory at least, where there is more weight as a result of the metal roof (145g to the Dia 127's 125g), the primary springs are now right, so the secondaries are the issue now. The first solution I will try, though work is busy this week, is to lengthen the secondaries by 1mm or so in the way mentioned in my last post; if that doesn't work, the 7-gauge strings should arrive today.

I have a rake of the clerestory coaches on the D&S complicated compensated bogies, and I think they ride at the right height. At the very least the footboard on coach and bogie line up. Could you not resolve this by further reducing the height of the bogie mounting plate? As a mater of interest these weigh about180 grams and I would have said up to 200gm isn't out of the way for a brass coach. Knutsford East ran 5 coach rakes of such things up a 1:100 gradient routinely with 4 coupled locos. Dick Petter, who built many of the coaches, ran 11 couch rakes up a similar gradient with a curve in it but he did use locos to suit. My G4 4-4-2 tank could only manage nine.

[Daddyman]

I have a rake of the clerestory coaches on the D&S complicated compensated bogies, and I think they ride at the right height. At the very least the footboard on coach and bogie line up. Could you not resolve this by further reducing the height of the bogie mounting plate? As a mater of interest these weigh about180 grams and I would have said up to 200gm isn't out of the way for a brass coach. Knutsford East ran 5 coach rakes of such things up a 1:100 gradient routinely with 4 coupled locos. Dick Petter, who built many of the coaches, ran 11 couch rakes up a similar gradient with a curve in it but he did use locos to suit. My G4 4-4-2 tank could only manage nine.

Many thanks for the input, Will. The idea of reducing the mounting plate was my first thought, but then Dave Bradwell pointed out that that might not be the issue, and that I needed to get the upper edge of the bogies frames at the right height first, which I've now done, before worrying about buffer height. I'm hoping that liberating the secondary springs from the stranglehold I had fixed them in will give me the last few fractions of a mill I need; failing that, the next solution will be to replace the secondary springs with 7-gauge wire; if that doesn't work, I'll attack the mounting plate.

[davebradwell]

Wrote this last night but it conforms where you're going.

It would be such a step backwards to remove the nicely designed sprung bogies with their smooth ride and replace them by compensated just for the sake of working out how to adjust them. After all on the full size they would have had to go round with their spanner to get the steps to line-up. Anyway the side profile is incorrect on the D&S bogies - DavidA and I had already established this. It would seem reasonable to make all coaches the same weight as the clerestory so that common settings can be used and it sorts the primaries out and saves me pleading for wire bending. We adjust the secondaries on my bogies by moving the bolster up and down essentially as WillL has suggested so this is certainly a sound option.

Just a little on springs, generally. There's a number of ways a leaf spring, which is what we have here, can be used. There's textbooks with all the variations and you just pick the case that applies and use the formula to determine the deflection. The case chosen here has the spring simply supported and the diagram shows knife edges to make this clear. If the spring is not as free, either because the holes are a little tight on the wire or the ends of the spring are bent over tightly or catching another part, then different formulae apply and you are probably hopping from one formula to another as the spring is defected. The spring action should be linear - twice the weight should give twice the deflection - but this all goes out of the window if the basic rules aren't being followed.

I feel you're getting there but slowly.

DaveB

[Daddyman]

I feel you're getting there but slowly.

Well, thanks to your - and everyone else's - help. Couldn't have done it alone...

[Daddyman]

Model:

Swearbox:

Only another 4 bogies to go...

[Neil Smith]

Well done!

What was the solution that worked in the end?

All the best

Neil

[Winander]

David,

Persistence pays, literally!

An interesting and informative discussion and I imagine your satisfaction is tempered by the trials and tribulations but better for getting it 'all right'. A lovely looking model, be sure to post pictures when they're painted.

I am curious about the handrail, would staff had to go up there so often to need one? Was it to do with oil lamps?

[Daddyman]

Well done!

What was the solution that worked in the end?

All the best

Neil

Listening to Dave Bradwell! And lots of jigs (the caption here was written for a more general audience - please excuse that):

The 8-gauge wire was a dead end which wasted months: the carriage just wouldn't keep still, so it was virtually impossible to set up the footsteps- footboard alignment: even something as small as a whitemetal gas tank on one side and not the other caused the coach to lean! Dave kept saying I should use thicker wire and bend it on a jig to get the correct ride height, which as he said, "for some reason you don't seem to want to do." Please shout next time, Dave! So the solution was 9-gauge secondaries and 10-gauge primaries.

The other thing was finally abandoning the packing height recommended in the instructions - I went with 1mm plasticard (total) in the end (can't remember if the instructions said 1.5 or 1.8 total (etch plus PCB)- too much anyway).

I am curious about the handrail, would staff had to go up there so often to need one? Was it to do with oil lamps?

I noticed it very late in the game and have never seen it modelled, so was going to let myself off. But Dave egged me on... It's visible here, and, yes, presumably for access to gas lamp tops (these never had oil) - possibly when they were gas proper (as built in 1895 - photo 3) and had hoods on the main roof, rather than gas mantle (after 1906 and as modelled here - photos 1 and 2).

[Mike Garwood]

That is a cracking bit of coach work!

Mike

[Daddyman]

Thanks, Mike!

[DougN]

Have to agree the carriage looks fantastic. Yes I have one (no where as nicely done as yours) in the snag pile! Can't remember what the snag was To push it forward?

[Neil Smith]

Thanks for the detail - duly stored away for future reference!

All the best

Neil

[Daddyman]

Thanks for the detail - duly stored away for future reference!

All the best

Neil

I'll try and get some pointers for navigating the bogies' foibles put up in the next few days, Neil. There are quite a few areas where you need to be careful.

Have to agree the carriage looks fantastic. Yes I have one (no where as nicely done as yours) in the snag pile! Can't remember what the snag was To push it forward?

Yes, there are a lot of potential snags on these, Doug. If you can find what it was, let me know - I may have a workaround for the snag in question.

[Chas Levin]

Here are some pretty pictures for anyone who's getting bored. You can see how crucial it is to get the ride height right, as the bogie steps have to line up exactly with the long footboards between the bogies - several days' work even with the rigid bogies fitted here:
10.JPG
20200927_101222.jpg

David, I wasn't getting bored but I very much enjoyed the pretty pictures nonetheless: beautiful rake you have there!

[Daddyman]

Thanks, Chas. I'm currently having a blissful two weeks off the carriages at the moment, and undergoing some North British therapy. Back to the NER grindstone next week....