Southwold coach

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GTB
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Re: Southwold coach

Post by GTB » Mon Dec 07, 2020 1:51 pm

ge_rik wrote:
Sun Dec 06, 2020 10:14 pm
No. But I don't think the curves on the Southwold were as severe as on the PLR.
The model certainly looks like a Southwold passenger coach, so you've nailed that part of the project. I'm also impressed you managed to get it to work on R1 curves.

I can't find any mention of the Southwold minimum curve radius, but the book 'Branchline to Southwold' has a reprint of a piece printed in 'The Engineer' in 1878 describing Mr. Cleminson's brainchild. It mentions that North Wales Narrow Gauge Railway trains with these coaches were running on two chain curves and had safely reached the heady speed of 20 mph.......

What part of your track has problems with the model? Reverse curves by any chance, or are the problems on track with vertical curves?

I've always been intrigued that the diagrams of how Cleminson underframes work only ever show them on constant radius curves. Reverse curves are never discussed, nor what happens when passing from straight to curved track.

A thought experiment suggests that when running through a reverse curve the end axles will be trying to rotate in opposite directions and the whole shebang will become a very long rigid 6 wheel underframe as it passes through the transition from one curve to the other.

The Southwold Cleminson wagons have a much shorter wheelbase, so should be easier to get to work on your track I would think.

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Graeme

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Re: Southwold coach

Post by ge_rik » Mon Dec 07, 2020 3:02 pm

GTB wrote:
Mon Dec 07, 2020 1:51 pm
I can't find any mention of the Southwold minimum curve radius, but the book 'Branchline to Southwold' has a reprint of a piece printed in 'The Engineer' in 1878 describing Mr. Cleminson's brainchild. It mentions that North Wales Narrow Gauge Railway trains with these coaches were running on two chain curves and had safely reached the heady speed of 20 mph.......
Peter Paye's book says the sharpest curve on the Southwold was at Halesworth with a radius of 5 chains. Not sure how the NWNGR coaches compared in length with the SR coaches. I had to bring the outer wheels inboard and increase the width of the centre truck to allow it to negotiate my curves.
GTB wrote:
Mon Dec 07, 2020 1:51 pm
What part of your track has problems with the model? Reverse curves by any chance, or are the problems on track with vertical curves?

I've always been intrigued that the diagrams of how Cleminson underframes work only ever show them on constant radius curves. Reverse curves are never discussed, nor what happens when passing from straight to curved track.

A thought experiment suggests that when running through a reverse curve the end axles will be trying to rotate in opposite directions and the whole shebang will become a very long rigid 6 wheel underframe as it passes through the transition from one curve to the other.
The problems I'm encountering are with vertical curves - more particularly dips where the centre wheels lose contact with the track.
I've tried it through the R2 reverse curves at Beeston Market and it gets through OK, though I can feel resistance from the flanges just before and after the half way point. The coach wheelbase seems just right for R2 reverse curves as one outer wheelset is leaving at the other is entering the curve.

Peter Paye observes (p209)
The coaches advanced in a diagonal movement when in motion and tyre wear was above average especially on the outer pairs of wheels. The wheelsets were regularly sent ...... for retyring and deep tyre turning .....
Maybe I should buy a lathe ...... :?
GTB wrote:
Mon Dec 07, 2020 1:51 pm
The Southwold Cleminson wagons have a much shorter wheelbase, so should be easier to get to work on your track I would think.

Regards,
Graeme
I did wonder whether to construct a wagon first, but figured that if I could sort out the undercarriage for the coach then modifying it for the wagon would be easier than vice versa.

Rik
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Re: Southwold coach

Post by GTB » Tue Dec 08, 2020 11:56 am

ge_rik wrote:
Mon Dec 07, 2020 3:02 pm
The problems I'm encountering are with vertical curves - more particularly dips where the centre wheels lose contact with the track.
I've tried it through the R2 reverse curves at Beeston Market and it gets through OK, though I can feel resistance from the flanges just before and after the half way point. The coach wheelbase seems just right for R2 reverse curves as one outer wheelset is leaving at the other is entering the curve.
That's interesting, as an R2 curve is approx. 2'6” radius, which scales out to 50' on a real 3' gauge railway. The minimum design radius for a quarry Hunslet was 50' and I bet the flanges were squealing on that tight a curve. Somehow I doubt a Cleminson underframe would have got around the track in Penrhyn quarry.......

If it's just dips in the track that are left as the main issue and if you aren't already using them, fitting LGB wheels with their deep flange in the centre truck would help, but calling out the track gang when the weather improves for a bit of track lifting and ballast packing would be a better way forward long term. ;)

Last resort would be to build in more vertical play in the steering linkages and lightly springing the centre axle with coil springs which would give the longest spring travel.
ge_rik wrote:
Mon Dec 07, 2020 3:02 pm
Peter Paye observes (p209)
The coaches advanced in a diagonal movement when in motion and tyre wear was above average especially on the outer pairs of wheels. The wheelsets were regularly sent ...... for retyring and deep tyre turning .....
Maybe I should buy a lathe ...... :?
That's a very interesting comment by Paye. One of the major claims by Cleminson was that his system would reduce tyre wear.

I have actually seen serious flange wear on brass wheels in HO scale after many, many hours of running. With steel wheels and brass track, I would expect to see rail wear first on my garden railway. Given how little running I do, I haven't even seen the tarnish worn off the rail so far. :roll:

A lathe is a useful thing in modelling, but one big enough to turn wheelsets costs about the same as buying 120 steel commercial wheelsets.......... That said, if you can figure out how to use a 3D printer and find a use for it, you can probably do the same with a lathe.
ge_rik wrote:
Mon Dec 07, 2020 3:02 pm
I did wonder whether to construct a wagon first, but figured that if I could sort out the undercarriage for the coach then modifying it for the wagon would be easier than vice versa.
Either way would work I think. The main requirement is to be stubborn enough to fight a recalcitrant project into submission. 8)

'Nil Desperandum Carborundum'

Graeme

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Re: Southwold coach

Post by ge_rik » Tue Dec 08, 2020 1:47 pm

GTB wrote:
Tue Dec 08, 2020 11:56 am
'Nil Desperandum Carborundum'
Thanks Graeme, as informative as ever.
The version I know is "Illegitimi non carborundum" which I think is self explanatory ...

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Re: Southwold coach

Post by River Lin » Wed Dec 09, 2020 2:19 pm

Hi All.
This is my home built NWNG railway Cleminson carriage.
IMG_20201209_132759.jpg
My difficulty was also trying to keep the centre truck on the track. I initially made it with a flexible coupling of rigid arms connecting the centre truck to the end trucks similar to the system below as used by DLT. On RM Web(His photo).
IMG_20201209_134128.jpg
This however did not allow enough flexibility for the lines I run it on. The problem was, as said, on reverse curves where a parallel siding left the main line for instance. When the first truck was turning onto the curve of the turnout the middle and rear truck were still on the strait track, but because of the front truck turning it was forcing the middle truck sideways which made it leave the rails. I then had to redesign my model with a more flexible system as shown below.
IMG_20201209_132828.jpg
I used a length of thin plastic coated steel wire to connect the centre truck to each end truck. It is screwed to the centre truck and passes through a hoop about half way along the end truck arm giving about 4cm of unsupported wire either side of the centre truck. This allows one end truck to turn while, due to the flexibility of the wire, the centre truck can still be on strait track. In the extreme case, while one end truck is on the siding and the other end truck is on the parallel main line, the centre truck can be going round the curve of the turnout.
I also allowed plenty of vertical movement in the centre truck guides to allow for the length of the carriage on uneven track.
David.
Last edited by River Lin on Fri Dec 11, 2020 11:53 am, edited 1 time in total.
David T.

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Re: Southwold coach

Post by ge_rik » Wed Dec 09, 2020 4:08 pm

That looks ingenious, David.

I'm still fiddling with my system. I've now given the centre truck a lot more downward movement to cope with the deepest dip on my trackwork which also happens to coincide with a curve and a point. I'm finding the outside wheel now sometimes lifts up off the track. I've piled more lead on to the truck but that's not cured it. The next job is to get the PW gang to sort out the track!

All good fun. I'm going to stick with it!

I've just examined the track layouts of all the Southwold stations and it looks like the coaches were never faced with reverse curves, even on the sidings where they stored the coaches. Not sure if it was deliberate planning or serendipity..... 🤔

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Re: Southwold coach

Post by GTB » Thu Dec 10, 2020 10:39 am

ge_rik wrote:
Wed Dec 09, 2020 4:08 pm
I'm still fiddling with my system. I've now given the centre truck a lot more downward movement to cope with the deepest dip on my trackwork which also happens to coincide with a curve and a point. I'm finding the outside wheel now sometimes lifts up off the track. I've piled more lead on to the truck but that's not cured it.
I've seen two wheel trucks on steam locos do that on curves, usually the lead truck.

In the cases I've seen the truck side control forces were applied above the axle, which meant that when the flange was against the rail the side control force tilted the truck using the flange as the pivot and the other wheel lifted off the rail.

If the side force is applied below the axle, the wheel that was lifting is pushed down harder instead........ The fix we made was to move the side control springs down so they were acting below the axle centre line and I now always do that with two wheel trucks on locos. I build.

Since the control arms in every cleminson model I've seen are tucked up out of sight behind the side sills, it may be that the centre axle is running out of travel and is being tilted by the steering forces from the other axles. The lever ratios are presumably high enough that they were able to lift the added weight as well.

If this is what's going on, lifting the track won't stop the axle tilting when the centre truck runs out of travel. Something like David's flexible wire connections, fitted so that they act below the axle on the centre truck might do the trick though.

Graeme

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Re: Southwold coach

Post by ge_rik » Thu Dec 10, 2020 12:19 pm

GTB wrote:
Thu Dec 10, 2020 10:39 am

I've seen two wheel trucks on steam locos do that on curves, usually the lead truck.

In the cases I've seen the truck side control forces were applied above the axle, which meant that when the flange was against the rail the side control force tilted the truck using the flange as the pivot and the other wheel lifted off the rail.

If the side force is applied below the axle, the wheel that was lifting is pushed down harder instead........ The fix we made was to move the side control springs down so they were acting below the axle centre line and I now always do that with two wheel trucks on locos. I build.

Since the control arms in every cleminson model I've seen are tucked up out of sight behind the side sills, it may be that the centre axle is running out of travel and is being tilted by the steering forces from the other axles. The lever ratios are presumably high enough that they were able to lift the added weight as well.

If this is what's going on, lifting the track won't stop the axle tilting when the centre truck runs out of travel. Something like David's flexible wire connections, fitted so that they act below the axle on the centre truck might do the trick though.

Graeme
Thanks Graeme. Another really comprehensive answer.

I did wonder about using some sort of springing system. It's interesting that the outer wheel only lifts when the coach is travelling in one direct but not when it travels in the opposite direction. I've tried turning the coach around in case it was something to do with the leading outside wheel truck, but the lifting was unchanged, Ok going forwards, wheel lifting in reverse. It's odd. As you surmised though, if I give one of the outside trucks a poke the middle wheel drops back on to the track.

I'll keep tweaking .... I won't be defeated. ..... (Yet!)


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Re: Southwold coach

Post by GTB » Fri Dec 11, 2020 12:31 pm

ge_rik wrote:
Thu Dec 10, 2020 12:19 pm
I'll keep tweaking .... I won't be defeated. ..... (Yet!)
That's the spirit......... ;)

I used to get similar behavior with HO models, especially the older scratchbuilt ones......

There could be some asymmetry in the track curve at the problem place. The couplings may be involved for that matter, as the forces steering the outer trucks will act differently between pushing and pulling.

Graeme

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Re: Southwold coach

Post by ge_rik » Wed Apr 07, 2021 7:16 pm

It's been a while since I revisited this project. If you recall, I designed and 3D printed a Southwold 6-wheel coach and took a while to tinker with the underframe until it worked reasonably reliably. However, there were a couple of places on my railway where the coach sometimes derailed. At Bulkeley station it was because there was a dip in the track which meant the centre truck floated above the rails and at Beeston Castle it was the opposite - there was a hump which meant the coach see-sawed on the centre truck and one of the outer sets of wheels left the track.

Rather than yet another redesign of the coach underframe, I ripped up the track at these two stations and have just finished relaying it to eliminate the offending undulations. It was worth it, because I also ironed out a few kinks in the track at the same time and, as I also had to remove and replace the island platforms, I installed some wiring for gas lamps beneath them.
Merged by bc upgrade.jpg

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Re: Southwold coach

Post by philipy » Wed Apr 07, 2021 7:26 pm

That seems like time well spent Rik. Looking forward to the finished installation.
As an aside, the castle has weathered in really nicely now.

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Re: Southwold coach

Post by ge_rik » Wed Apr 07, 2021 8:43 pm

philipy wrote:
Wed Apr 07, 2021 7:26 pm
That seems like time well spent Rik. Looking forward to the finished installation.
As an aside, the castle has weathered in really nicely now.
Thanks
Yes, it's mellowing nicely. In a couple of years' time I may have to attack it again with the cement dyes
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