Stanier 3P - Judith Edge Kit

bécasse
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Re: Stanier 3P - Judith Edge Kit

Postby bécasse » Wed Jan 27, 2021 8:56 pm

I'd make a couple of comments which relate to the original diagram.

Firstly I suspect that suitable coil springs are readily available as N gauge spare coupling springs, the cheapest seemingly being a set of 4 from Dapol for £ 1 (plus p&p), although I might be inclined to go for a pack of 10 Graham Farish ones from Peter's Spares at £ 4,95 as I have always found them jolly useful (even if they are very fond of the carpet monster).

Secondly I would use graphite - from rubbing a soft, say 2B, pencil over the plates or puffing lock graphite over them (or, even better, both) - as the lubricant between the rubbing plates, which would probably prove to be everlasting.

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ianpenberth
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Re: Stanier 3P - Judith Edge Kit

Postby ianpenberth » Wed Jan 27, 2021 9:09 pm

Hi Pete,

I'd say it looks promising.

This is the leading truck from my 1Co bogie, done as a radial truck (the real thing has a set of levers to make it rotate around some kind of virtual centre). Suspension-wise it seems to be along the lines of what you're suggesting. The radial top and bottom are constrained by three vertical sliding faces which provide the radial movement and prevent it from rotating about the axle - both of which would be provided by the pivot arm in your case. In terms of twist, a little extra clearance is provided (really no more than to allow the truck to slide freely without locking) and perhaps a degree of running clearance in your pivot would provide the same - amplified by the greater distance between the wheels.

The spring wires are equalised between the truck and the leading driving axle but the effect will be similar to what you have in mind - you would have a less eccentric load on the spring seat, if that matters.

Side control I guess comes from friction between the suspension plate and the truck itself, plus perhaps a bit from the vertical slides - it works well steering the bogie into curves. There is a loose fitting and very weak spring giving side control on the sharpest curves but it's as much to stop the bogie falling apart when you pick it up as anything else.

Image
Image
(the truck is upside-down in the above photo)
Image
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(Images lifted from my kit instructions at http://www.penbits.co.uk/Content/KitDoc ... embly.html)

Cheers! :D
Ian
PenBits Model Railways - Diesel bogie springing and detailing

davebradwell
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Re: Stanier 3P - Judith Edge Kit

Postby davebradwell » Thu Jan 28, 2021 9:24 am

All very sound I'm sure but the prototype put the springs in the pony so I always feel drawn to do the same. Be careful your frame mounted springs aren't compromised by reality - the pony has cosmetic springs on the ends and it's possible for these and constructional details to push the frame springs closer together which is very bad news. It all depends on how much swing you need and if your sprung plank is below the top of the wheels it gets shortened to clear the swing. I have a radial truck which is terrible because the frame mounted springs have ended up too close together.

Dave Holt has shown how to spring an LMS pony - is this no use?

DaveB

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ianpenberth
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Re: Stanier 3P - Judith Edge Kit

Postby ianpenberth » Thu Jan 28, 2021 9:43 am

Yes, it was a challenge to fit it all in to the available height. Whether you could get a long enough spring beam within the available space could also be an issue?
Ian
PenBits Model Railways - Diesel bogie springing and detailing

LenPinder
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Re: Stanier 3P - Judith Edge Kit

Postby LenPinder » Thu Jan 28, 2021 12:29 pm

PeteT wrote:
I thought I'd post the concept before trying it, to see whether anyone has tried something similar before - or can think of any potential pitfalls.

I haven't mentioned side control, but don't see any issues implementing that alongside this concept - and doing it as a separate system rather than trying to calibrate both to work with one spring.


Pete

For what it is worth, I attach a number of photographs showing how I incorporated the front pony truck of a LNER K3 2-6-0 into a CSB sprung chassis calculated as an 0-8-0.

61833 pony CSB front pivots.jpg


The CSB wire shown in these photographs is a temporary 0.4mm diameter brass wire to aid alignment, etc. This wire was replaced by 12thou guitar wire on final assembly.

61833 pony CSB front pivots 2.jpg


The rubbing plate is constrained from moving along the CSB wire by means of two pieces of 1mm brass angle iron soldered to either side of the frame.

The rubbing plate is 1mm narrower than the space between the frames to allow a little sideways tilt.

61833 pony CSB rubbing plate.jpg


The rubbing plate bears on the top of the pony truck and has left a faint witness mark showing the radial track as the pony truck pivots. Ignore the vertical wire in this photograph. This was a pretty naive attempt at providing some side control but the springing was too strong, causing the pony truck to derail. A pair of side-cutters quickly corrected that.
61833 pony.jpg


The assembly is relatively simple to construct and worked pretty effectively, as attested to by the comments of Ken Kirk in the minutes of the NAG meeting of 2nd and 16th July 2015.

https://www.scalefour.org/forum/viewtopic.php?f=78&t=4369

Len

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PeteT
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Re: Stanier 3P - Judith Edge Kit

Postby PeteT » Thu Jan 28, 2021 4:39 pm

Thanks for the thoughts!

I think my problem with the concept of off the shelf springs is the need to allow movement up as well as down, while taking enough weight in the middle for road holding. However the system seems, in my mind, quite easy to retro fit if plan A doesnt work so I'll keep them in mind.

Len/Ian thanks for the photos - Len's seems very much in line with what I had in mind. I was thinking of a wider pad to reduce friction/wear, but this could be a T rather than a U - as a straight beam has worked well by the looks of it. The straight beam allows tilt which a T or U would need 'play' to allow, but without the ability to jam - so I'm tempted to follow your lead.

I think the length of spring beam is ok - slightly shorter than a wagon W iron (though I think the RCH1907 ones are a bit shorter anyway? though I don't own any to check, I may be misremembering...) but at 18mm against 21mm I think can be sorted with the wire gauge.

Dave I agree with you trying to replicate the prototype. I have used Dave's method for the Ivatt/BR pony, and these do seem to work well - I'm not sure how much weight they actually take though, nor how repeatable my coils are. Also, they seem less easy to build using off the shelf pony parts from rigid kits. Therefore my thinking is to try and make a system which works, but is also useable in the future when not designed in.

davebradwell
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Re: Stanier 3P - Judith Edge Kit

Postby davebradwell » Fri Jan 29, 2021 10:24 am

PeteT, at least your scheme allows some adjustment of weight on pony. There'd be no point for a bogie as these are so easy to spring. Must admit I've never seen the point of extending csbs to cover carrying wheels except to prove it can be done. I always fiddle with weight distribution when testing a new model and it's especially important when operating on lines with gradients.

I'll add that I find pony trucks much more difficult to tame than bogies which normally just glue themselves to the track. I'm thinking the height of the slide has a lot to do with it (my current design has a high slide) so there's a tendency to tilt.

Back to a Cartazzi - the most challenging of all.

DaveB

davebradwell
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Re: Stanier 3P - Judith Edge Kit

Postby davebradwell » Sat Jan 30, 2021 9:57 am

Thinking more about your sprung stretcher, Pete, mostly to understand if my discomfort with it is rational or not, I realised that lifting a wheel involves the slide moving - there's a sideways component to this basic action. The further away the spring the greater this component. Does that sink it? No, because the bogie is made to slide but there's much more friction than in the hornblocks and it's another thing to fight when the wheel meets a difficult situation. I'll keep putting my springs in the right place while trying to lower my slide.

DaveB

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Noel
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Re: Stanier 3P - Judith Edge Kit

Postby Noel » Sat Jan 30, 2021 11:27 am

davebradwell wrote:No, because the bogie is made to slide but there's much more friction than in the hornblocks and it's another thing to fight when the wheel meets a difficult situation


Apologies if this is a silly question, but the photos posted so far show the rubbing plates as metal on metal, apparently unlubricated, which is not a recipe for low friction. Lubrication is possible, but probably messy. Is it not possible to use a low friction material [PTFE comes to mind] on one or both surfaces if friction is an issue? I assume at this scale the vertical loadings would not have a deleterious effect?
Regards
Noel

Julian Roberts
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Re: Stanier 3P - Judith Edge Kit

Postby Julian Roberts » Sat Jan 30, 2021 2:36 pm

This may be missing the modelling point! Apologies if so...
Screenshot_2021-01-30-14-30-57.png
DO NOT OIL BOLSTER SLIDE

From this loco at NRM
Attachments
Screenshot_2021-01-30-14-34-45.png
Last edited by Julian Roberts on Sun Jan 31, 2021 11:35 am, edited 1 time in total.

davebradwell
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Re: Stanier 3P - Judith Edge Kit

Postby davebradwell » Sat Jan 30, 2021 2:48 pm

You can work hard to improve it if you wish but I'll avoid the struggle and stick with the safer solution. I can't see any benefits from springing the stretcher, there's a bit more space to fit the springs but there's a potential downside so why bother - there doesn't appear to be much of a trade-off. There'll always be more friction in the top slide than the hornblocks (usually just axle in slot), unless the weight on the pony is reduced to near zero, of course.

Regarding the oiling of the slide, I find this just dries up with time and ends up gluing the parts together. I'm thinking that the common n/s on n/s is a bad choice and use of dissimilar metals would be a good start. Interesting photo!

DaveB

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PeteT
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Re: Stanier 3P - Judith Edge Kit

Postby PeteT » Sat Jan 30, 2021 6:59 pm

Thanks for the thoughts and continued discussion!

I do agree that putting springs where the prototype did would ideally be the way to go. You mentioned before Dave Holts method for the Ivatt pony, which I have used and seems successful (though that has hardly been fully proved in my ability to implement it, which rolls but hasnt pulled anything as yet!). Aside from creating that cantilevered spring repeatably, the lack of a hornblock is another down side for it - though the High Level miniblock could be fitted with the spring acting on that rather than directly onto the axle.

I keep being tempted to built the WD pony, but am holding off starting yet another kit with others on the go. My reasons for looking at frame mounted springs are :
- That there is a longer length between anchors available (bufferbeam is in front of the front of the pony frame, and the rear is as far back as you like).
- The main frame and rubbing plate seem easier to modify, than the pony sides designed for a 2mm bearing. The Minibloc jig and frame makes cutting out for a hornblock repeatable though, so if hornblocks are used maybe this one goes away.
- I've ruled out in my mind 'single ended' springs (ie fixed at one end, with the pony axle at the free end). But bogie springing tends to use this method, so am I overthinking that issue?

These are the out of the box pony sideframes:
20201216_181334.jpg
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One thing I don't understand is how the effects of the rubbing plate is considered a potential issue? Surely the interaction is the same between those plates, regardless of whether the spring effect is above or below it?

(ps Dave B I sent you a PM a few days ago about J39 castings, could you have a read please? or am I best using your store page message box?)

davebradwell
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Re: Stanier 3P - Judith Edge Kit

Postby davebradwell » Sat Jan 30, 2021 10:03 pm

Just to tidy up your queries - I've never used an axlebox on a carrying axle and just file a slot for the axle to rise and fall in as fore and aft forces are small. To take the weight I have just rested the spring wire on the axle (as original B1) but it's a bit nicer if there's a brass pad soldered to the wire first (as A1). You can also make little brass V or U brgs and solder the wire to these (as K1, V3) and they also prevent the wire slipping out. Axleboxes and horns just seem a lot of effort where it's not needed - they look nice if you want a posh job, that's all.

You hit the nail on the head when you mentioned testing - plenty of folk have great sounding ideas but if nothing ever goes very far or very fast they never really know if it was any good or not. Most things can be made to work, it's just that after a while some seem to work better. Sometimes, of course, the constraints of the prototype mean you have to choose a non-ideal solution.

Sorry, I'm a bit slow with PMs, it's best to use the email facility. I've had a quick look and will attend in the morning.

DaveB

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Will L
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Re: Stanier 3P - Judith Edge Kit

Postby Will L » Sat Jan 30, 2021 10:26 pm

LenPinder wrote:
PeteT wrote:
I thought I'd post the concept before trying it, to see whether anyone has tried something similar before - or can think of any potential pitfalls.

I haven't mentioned side control, but don't see any issues implementing that alongside this concept - and doing it as a separate system rather than trying to calibrate both to work with one spring.


Pete

For what it is worth, I attach a number of photographs showing how I incorporated the front pony truck of a LNER K3 2-6-0 into a CSB sprung chassis calculated as an 0-8-0.

I was interested in this, I've never implemented a CSB sprung pony truck, but what Len has done is the the method that, when I've discussing it with others, has seemed the best way to go. Therefore I was pleased to note comments on the quality of its running in the NAG meeting Test Running Notes as follows.
Ken Kirk via RobM wrote:...
LEN PINDER: Gresley K3 2-6-0. South Eastern Finecast kit. CSB chassis including front bogie, making, in effect, an 0-8-0. Machima1628 motor with High Level Load Hauler 60:1 gear train. Tender has CSBs also. This was Len’s first attempt at a motorised locomotive and it runs superbly. Well done that man!


I would personally wish to be sure that the sprung stretcher should be held clear enough of the frames to ensure it couldn't jam between them at the maximum displacement on one wheel and none on the other.. However we must also consider that the actual amount of differential displacement in use on anything but the worse possible track would not exceed a few tenths of a mm, and that the CSB wires will be doing a good job of keeping it central.

Noel wrote:...the photos posted so far show the rubbing plates as metal on metal, apparently unlubricated, which is not a recipe for low friction. Lubrication is possible, but probably messy. Is it not possible to use a low friction material [PTFE comes to mind] on one or both surfaces if friction is an issue? I assume at this scale the vertical loadings would not have a deleterious effect?

I think the concerns here are misplaced. Many a loco has run perfectly well with similar metal to metal sliding contact between bogies and frame spacers with some side play allowed by an oval hole hole round the pivot pin. Why should it suddenly become a problem here? The photo shows some polish on the contact surfaces suggesting it has seen some running and it is running quite happily according to Ken Kirk.

davebradwell wrote:... Must admit I've never seen the point of extending csbs to cover carrying wheels except to prove it can be done. ...

And I'm inclined to agree with him, although my reasons and his may differ. Of course there are prototypes where carrying weight on a bogie/pony truck is necessary because of huge overhangs (Most 4-4-0s for instance), but most don't, so I would be inclined just to weight the actual Bogie/Pony truck and let it get on with it without trying to carry body weight.

I know this feels wrong to many people but who are trying to model as close to the prototype as possible but we have to ask ourselves what we are trying to achieve. The mechanical proprieties of our track and chassis are really very different from the prototype e.g. we replace heavy leaf springs with a single piece of spring wire which is scale terms is no bigger than a the torsion bars on your car. The problem is that the the Physics doesn't scale so a representation of the prototype may be a satisfying modelling challenge but wont perform anything like the real thing. So you get the choice of building it like the prototype or building it so it works.

While your at it, ask yourself the questions, why do locos have carrying wheels at all, and what is the purpose of side control springs on bogies and pony trucks. .

bécasse
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Re: Stanier 3P - Judith Edge Kit

Postby bécasse » Sun Jan 31, 2021 9:44 am

Will L wrote:I know this feels wrong to many people but who are trying to model as close to the prototype as possible but we have to ask ourselves what we are trying to achieve. The mechanical proprieties of our track and chassis are really very different from the prototype e.g. we replace heavy leaf springs with a single piece of spring wire which is scale terms is no bigger than a the torsion bars on your car. The problem is that the the Physics doesn't scale so a representation of the prototype may be a satisfying modelling challenge but wont perform anything like the real thing. So you get the choice of building it like the prototype or building it so it works.


It isn't just the motive power and rolling stock which don't perform like the real thing. One of my endearing memories of a rare train-spotting visit to Paddington as a (SE London-based) youngster was just how much vertical movement there was in the rails as they were slowly traversed by a heavy 94xx 0-6-0PT on ECS duty.

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PeteT
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Re: Stanier 3P - Judith Edge Kit

Postby PeteT » Mon Feb 22, 2021 5:38 pm

A bit of progress to report - some of which will definitely fall into the pointless category once hidden inside the cab, but it was useful to do some of these twiddles in a place it doesn't really matter to practice for similar things in visible locations.

The pony trucks have been assembled, this is the rear one - and Dave Bradwell long tender spring hangers fitted (I had them spare in a 4200g tender kit, which will be built using the shorter ones - but they are available separately). These need bearings and a representation of the actual springs, alongside a bit of other detailing still to do.

20210210_184943.jpg


The bunker front/cab back has been detailed (one handle is bent in the photo but has been rectified):

20210221_134718.jpg
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and the other 3 sides of the bunker have joined it. The rear is in need of a strengthening strip adding at the bottom of the hopper.

20210221_204208.jpg


20210221_204146.jpg


The cab front and sides are tacked onto the footplate, but the bunker assembly is still loose at this stage. I need to assemble the frames, and sort out the body fixing and motor locations before fitting that.

20210221_204133.jpg
20210221_204133.jpg (279.54 KiB) Viewed 1265 times


So aside from the frames, and detailing the pony trucks, the next steps are the boiler, smokebox and saddle. The firebox assembly went together well, and I've done some initial forming of the smokebox and boilers. The smokebox isnt far away, but I haven't annealed it yet so that should help sort it out. Likewise the boiler.

20210222_165551.jpg
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I've curved the smokebox saddle, and that shape looks ok against the supports. What I haven't quite worked out is the half etched line on the sides - but assume this is to allow a small foot/lip at the lower/footplate edge. I haven't quite confirmed this from photos yet.

20210222_165748.jpg
20210222_165748.jpg (303.17 KiB) Viewed 1266 times

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PeteT
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Re: Stanier 3P - Judith Edge Kit

Postby PeteT » Sun Feb 28, 2021 9:50 pm

The current state of play, includes the smokebox - I'm pleased with how this has turned out, so am confident that the boiler barrel will end up looking good too. The frames are together, but need the pony sprung rubbing plate assembling and fitting.

This will probably go a bit quiet though, as the weather has been very spring-like this weekend I want to get the J39 detailing done so it can enter the paintshops.

20210228_204701.jpg


20210228_204126.jpg

Dave Holt
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Re: Stanier 3P - Judith Edge Kit

Postby Dave Holt » Sun Feb 28, 2021 10:12 pm

Coming along very nicely, Peter.
I suspect on the saddle there's a very short vertical section below the sloping side pieces - hence the half etched line.
Dave.


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