On Heather's Workbench - going wide

[Heather Kay]

Finally, back where I was on Friday.



Bit of a piggy to get the frames square again, and one of the folded-over buffer beam ends came adrift, but I can now begin contemplating the actual running gear again.

 

[Heather Kay]

This morning's task is to work out the centrelines for the suspension units, and work out the ride height.



The Connoisseur units are neat fold-up things, provided with simple but comprehensive instructions. Two units are for the outer wheelsets, with a slightly narrower unit for the centre wheelset in a six-wheeled coach. This is to allow some sideplay on the centre, which may or may not be necessary for this build.

Note the various triangular and diamond holes, which are designed to help alignment of the unit when fixing to a coach floor.



I do worry that some of my measurement techniques are a bit slapdash, relying on offsets and alignments aided by the Mark One Human Eyeball. Then again, I can't see how I can do it otherwise in some situations. Having fitted the "floor" plates over each axle (they are not actually fixed yet, which isn't helping with alignment issues) I needed to find the vehicle's longitudinal centreline. A length of 1mm brass rod run through the coupling slots on the buffer planks helped, followed up by some vernier measurements.

I suppose it doesn't really matter if the units are a little off centre, provided the wheel sets are parallel across the coach. But that's not the point.



I formed up one suspension unit as Big Jim intended, so I could do some eyeballing for ride height and general orientation. I haven't fitted the sliding bearing surfaces yet, but this crude assemblage is enough for me to see how things fit, and for me to work out how far apart the bearings need to be to suit the broad gauge. This unit will be hacked apart, but the unbuilt ones can be split before forming up.

The ride height isn't a million miles out, but I can't confirm that until the proper bearing units and springs are fitted.

What became apparent is there is precious little space between the front of the wheel and the back of the axleguards. I do not think there will be any sideplay in the centre axle at all. Future builds will need to take this into account when thickening up the solebars, and this build will need some careful insulation placed to avoid shorts.

After the fairly rapid progress on this build, even allowing for the rebuilding yesterday, I am now finding patience waning and frustration building. I guess I ought to firm up the various mods required on the suspension units before I pack it all away again in favour of another of the growing pile of part-built commissions!

 

[Heather Kay]

Another stumbling step forward, and now I've stalled.



Looking rather incongruous with the BG wheelset flopping about, I've built up the sliding and sprung parts of the suspension unit. This was partly to make sure I knew how it all went together, and partly to help hold the wheelset for the eyeball alignment routine.

You can probably work it out, but in case it's not obvious, there's a length of fine steel wire which acts as the spring. The "bearing" is a hole, reinforced and thickened by a selection of etched washers. The bearing hole has to be opened out with a broach for a freely running axle. Depending on the model and gauge (I am talking O and S7 here, not BG) more washers are added to restrict sideplay.

It's all very neat, I have to say. While the sliding bearing unit is only retained by the wire spring, it is free to flap about at the axle end which causes binding. Of course, for narrow gauge, it's fine because the back of the wheel keeps the unit in place, and the same will be the case once I've worked out where it goes for the BG wheels. I was tempted to add a little restraining strap of brass wire or scrap etch across the retaining hooks to prevent the flappiness, but it's unnecessary.

Fitting the suspension unit to the floor will be done by bolts of some size or other (TBA … sorry!). There will probably be four per unit, and a selection of washers used to set the ride height.

Having got so far, my brain cell gave up working out how to keep all the axles parallel during construction. I suspect some kind of jig will have to be created. For some light relief I shall consider spending some time on the Mk1 RMB build, or possibly return to the WD tender for a spell. Or perhaps I shall go and begin to disassemble my old car so we can extract some valuable hydrocarbons before it gets scrapped…

 

[OzzyO]

Hello Heather,

looking at the sliding bearings could you fit a length of wire through the two holes in the folded over tags at the bottom end?

I think that I would look at splitting the bearing units down the centre line and mounting them on some 1" X 0.025" (these sizes are a guess) brass strip. Doing it this way would put the bearing and springs closer to the wheels which should help with the ride of the coach.

OzzyO.

 

[flexible_coupling]

Ahh, so it's using CSB principles... cool! I like that.

 

[Heather Kay]

I ought to make it clear, I think, that the plan has always been to split the suspension units to support the wider axles properly. I wanted to build one up as intended for my own satisfaction, and help me gauge the fit, ride height and so on before I built the rest for the wider gauge. As you say, Paul, mounting the units on some brass strip would be ideal.

Plans are for a jig to help me align and space the axles out on this and future builds.

 

[mickoo]

Ahh, so it's using CSB principles... cool! I like that.

Indeed, looks like a very neat mini CSB set up per axle.

The only issue I can see with the coach being a three wheeler is that all CSB mounts will be exactly the same, I'm assuming all the etch work is identical for each axle? I had the same set up on the 08 where each axle took 33% of the load, on paper it was fine, but in practise the loco tended to nod and rock fore and aft when travelling.

The result was to change the weighting to a 35-30-35% ratio and it was more stable. With all these being the same the coach may nod and rock on the centre axle a bit. Because all the fulcrum points appear the same one possible way around this will be to apply slightly thinner CSB wire to the middle axle only and thus reduce its tension and load bearing capacity.

I have been toying with the same idea for loco wheels, I.E. individual CSB per axle rather than one long wire, especially for locos with open and exposed frames.

 

[Dog Star]

... all the fulcrum points appear the same one possible way around this will be to apply slightly thinner CSB wire to the middle axle only and thus reduce its tension and load bearing capacity.

When Exactoscale was a separate business one could buy, from Len, spring steel wire in different thicknesses and that was a "necessary" to tune the Exactoscale wagon springing units to the weight of plastic / etched / whitemetal kits. Worth calling C&L to see if those products are available now.

regards, Graham

 

[Heather Kay]

The only issue I can see with the coach being a three wheeler is that all CSB mounts will be exactly the same, I'm assuming all the etch work is identical for each axle?

I suppose this might be an issue. Mention is made of varying the strength of the spring wire in the instructions.

To be honest, I'm more worried about adequate sideplay on the centre axle!

 

[JimG]

Indeed, looks like a very neat mini CSB set up per axle.

You will incur the wrath of the CLAG group. CSBs are supposed to be continuous wire beams between two or more axles which impart a certain amount of compensation as well as springing. Single springs on each axle are just springs.

Jim.

 

[mickoo]

You will incur the wrath of the CLAG group. CSBs are supposed to be continuous wire beams between two or more axles which impart a certain amount of compensation as well as springing. Single springs on each axle are just springs.

Jim.

I suppose it should be called ISB 'Individually Spung Beam'

 

[mickoo]

I suppose this might be an issue. Mention is made of varying the strength of the spring wire in the instructions.

To be honest, I'm more worried about adequate sideplay on the centre axle!

Heather, for such a short wheel base I'd say 0.5-1.0mm will be more than satisfactory side play. 0.5mm per axle will give a total of 1.0mm over the whole wheelbase, though that does depend on the severity of curvature the stock has to work over.

Your issue looks like the external W irons will be the restriction, I've something similar on the Peppercorn 8 axle tender which will employ split axles, this makes the hub on each side effectively live and through a tight curve it is possible that the intermediate axles will touch one side of the frame work and the outer axles will touch the other side and short it all out. I may have to skim down the hubs by 0.5-1.0mm to give better clearance, the wheel rim is fine, it's the brass hub that's sticking out too much, you may not have that issue as your axle will be insulated by the plastic wheel from the rim.

 

[Heather Kay]

After a spell away from this build, I have been wrestling with the running gear.



I spent a while working out where the newly-split suspension unit fitted. There are many variables in this build, which makes it hard for my brain cell to work out which datum to use for axle alignment. Eventually a synapse made contact, and I added some brass U-section to bind the three stretcher plates together. Some visual alignment, followed up by some measurements, and some more thinking, and I think I have it worked out.

The suspension units have oval holes in their bases, and I will use four bolts to fix them to the stretcher plates. The bolts will allow a little adjustment for alignment, I hope.

To aid my usual bodgery in getting the axles parallel to themselves, if not the whole underframe, I concocted a jig from styrene.



The uprights and pegs at each end fit over the underframe buffer beams reasonably snugly, while the slots along the base fit an axle each.



Here it is with the underframe fitted. With a fair wind, this will let me adjust the suspension units to get the wheel sets aligned.

I had better drill the bolt holes, and construct the other suspension units.

While I had planned on a solid floor for this model, the stretcher plates are easier to fabricate. The gaps will help me locate and fit the brake gear, and I can fit a false floor before the roof goes on. Modelling by the seat of my pants: a sometimes enjoyable pastime.

 

[Heather Kay]

Today I set myself the target of getting all three suspension units mounted on the floor.

Two 8BA bolts hold each half unit.



The concept works, in that I can individually adjust each half to get everything square and as true as I can. I need to get a stock of bolts in, because I don't have any slot-head ones, so this is temporary to let me at least see if the wheelsets fit! With the right bolts, I plan to solder the nuts in place to make it easier to fiddle about with things.

With my target met for the day, I will spend what's left of the afternoon chasing off down one or two rabbit holes on other projects.

 

[OzzyO]

Try this fellow, you normal get them next day and the prices look very good,




A very nice man to deal with,

OzzyO.

 

[Ressaldar]

Heather said -

With my target met for the day, I will spend what's left of the afternoon chasing off down one or two rabbit holes on other projects.

it's much too hot for that, you should be getting the white wine out of the fridge and enjoying it in the sun in the back garden

cheers - hic

Mike

 

[Heather Kay]

it's much too hot for that, you should be getting the white wine out of the fridge and enjoying it in the sun in the back garden

You've not seen the building site that passes for my back garden!

Paul, thanks for the lead there. We were going to order from Just The Ticket Engineering Supplies. We had a nice chat with him at the ALSRM show at Reading, and he seems to know his onions.

 

[OzzyO]

You've not seen the building site that passes for my back garden!

Paul, thanks for the lead there. We were going to order from Just The Ticket Engineering Supplies. We had a nice chat with him at the ALSRM show at Reading, and he seems to know his onions.

Have you got a contact for him? Email, web, etc.

OzzyO.

PS. but does he know his nuts?

 

[Heather Kay]

Chap's name is Roger Melton, based in Salisbury.

He has a web site: http://www.justtheticket.tv
Email JustTheTicketEng@gmail.com

Telephone 01980 610058.

His main business is supplies and kits for larger scale and live steam. Very taken by his G1 SR Q1…

 

[Heather Kay]

It's like two steps forward, one back, with this build. There was a moment yesterday when I was seriously questioning why I agreed to take it on!



The state of play is the stretcher plates are now fitted permanently, axleguard tie bars are fitted, all step brackets are fitted. I have refitted the outer wheelsets while I scratch my noggin over the brake gear.

According to Russell, the narrow gauge version of this van had brake shoes on all wheels. It also appears to have tie rods from the outer axleguards to the buffer beams, which throws more spinners into the works. Anyway. Back to the brake gear… other six-wheeled stock doesn't appear to have the centre wheelset braked, but that may simply mean the brake vans were a special case, kind of obviously. The only photo I can find if an NG brake (V13) also shows what appears to be the Dean Churchward form of hand brake at one end! If I wasn't confused before, consider me confused now.

To further muddy already murky waters, there were two kinds of brake gear, one the wooden brake shoes had been upgraded to cast iron ones. The newer variant is the familiar inner brake rigging, but an earlier variant is a nicely complicated mess of outside and inside gear. I plan to use the later inner brake variant, to save my sanity.

I think I'd better consult with the client. What time is it in Australia?