A favourite (model) loco

[Dave Holt]

First, a belated happy New Year to all.

Sadly, I seem to have been overtaken by a malaise recently and have lost all motivation to do any actual modelling, so I thought I might post something about one of my favourite existing models, which pre-dates my involvement on WT (although some of the photos did appear in a different loco thread, back in 2019). It also pre-dates my photographing of my loco builds, so I am relying on prints of photos taken by others who I'll credit where possible.

The loco in question is a Caprotti fitted BR Standard Class 5, No. 73129, which currently looks like this:

These were taken by David Clarke after he applied some light weathering.

I always quite liked Caprotti fitted locos because they were different and quite rare. The LMS Black 5 versions were rather ugly but had a purposeful look about them. The BR Standard variety were well proportioned, handsome looking locos and were fairly common around Manchester in the early 1960s after all the English allocated examples (including 73129) migrated to Patricroft shed. Indeed, the very last BR loco I cabbed was one of this type. I was awaiting a Liverpool to Newcastle train, at Exchange Station, in 1968 and found the loco acting as West End station pilot, simmering in the Horse Dock siding. After standing for a few minutes, I was invited into the cab, where the fireman was keeping an eye on things whilst the driver had gone off somewhere. We chatted for 20 minutes or so till my train was announced. I remember him saying that both he and the driver were going to quit the railway when steam finished as they felt that diesels gave no reward for skill or effort by the crew.

Anyway, to the model. The basis was a DJH etched brass and white metal kit from which most of the loco body and tender were built. On the chassis, only the cylinders, slide bars and return crank gear boxes are from the kit. Being a P4 model, the chassis is my own concoction with Alan Gibson profile milled frames and wheels. It has fully floating compensation (no fixed axle). Drive is by an Escap motor driving through a modified gear box using MJT side plates. All the Caprotti drive shafts and reversing gear, except the return crank gear boxes, were scratch built using various diameters of tube and rod/wire. The universal joints were represented by parts made from 1.5 mm tube, as shown below.

The valve gear was made as a set of separate sub-assemblies to facilitate construction, assembly and dis-assembly for painting, as shown in the following series of photos taken by Barry Norman (for a possible article in Model Railway Journal that came to nothing).
Cylinders:

Main drive shafts:

Reverser shafts (viewed fro the opposite direction):
And assembled onto the chassis:

Don't want to run out of photo capacity, so I'll post a bit more in a separate post.

Dave.

 

[Dave Holt]

A major difference on the Caprotti locos is the arrangement for the mechanical lubricators and the exhaust steam injector supply pipe, none of which showed up very well in photos or the published drawings I had. Luckily, on a visit to the Midland Railway Centre at Butterley, the preserved 73129 was being restored and a polite request to be able to take some detailed photos and measurements in the work shop was granted. A bonus was a print of a lubrication drawing, clipped to an easel, which showed a side view and section through the lubricator mounting bracket. This was also photographed and aided construction of a fairly accurate representation. After some thought about how/where to split parts between loco body and chassis, I decided to permanently fix the injectors, pipework and lubricators bracket to chassis, although a section of the exhaust steam pipe were fixed to the drive shaft sub-assembly, previously illustrated.
Here are some photos of the chassis mounted arrangements.


Having the injectors, pipes and lubricator bracket fixed to the chassis was not a problem as the driving wheels are retained by a keeper plate and can be dropped out from below.

The completed loco was painted, lined and numbered by Ian Rathbone and ran in an un-weathered condition for some years. Hopefully, he won't be too upset by the subsequent light weathering shown in the first photos.
Un-weathered:

Photo source unknown but might be Barry Norman again.
Dave.

 

[ullypug]

It never ceases to amaze me just how much detail you manage to put into your models Dave, especially as it’s 4mm. Fantastic work!

 

[jonte]

This is indeed a wonderful piece of craftsmanship, Dave.

Unfortunately, I’ve always struggled to understand compensated chassis’ so please forgive my ignorance when I try and run it by you, in an effort to see if I’ve got the basics right. I do hope you don’t mind.

It appears that to start with, you either cut a square or rectangle (closed on three sides) into the chassis (frame?) in line with the wheels. Then, into the slots go some form of bearing, unfixed so they can slide up and down, with either a flange on one side or perhaps a slot to stop the wheels flaring out, through which the axles are threaded?
To stop the wheels falling out when you lift up the model, it appears that a set of (two?) wires run the length of the chassis, which either have loops at each end into which screws can be threaded (and thence into tapped holes in the chassis) or soldered to a central plate which can be fixed to the chassis in the same way with screws?

Moving onto the motion, does it mean that the holes for the crank pins and rods have to be ‘sloppier’ than on rigid chassis’, and if so, how do you gauge the maximum sloppiness allowed before it looks too sloppy a fit?

Then, moving onto instances like with this wonderful model, Dave, do the tubes and cylinder bits need to be articulated too rather than fixed to allow for the flexing of wheels on poor track?

It all really does seem quite complex and a wonderful feat of engineering.

As I say, would you or any other member kindly be able to put me right on this, and respectfully, without too much technicality, due to my mentioned ignorance of most of this intricate mechanical engineering.

Many thanks.

Jon

 

[Bigjohn]

Favourite model locomotive depends on the criteria. Mine is a GWR 14xx. I’ve scratch built six of them. OO O G3.
my reason?? In the 1950s on holiday at Brixham a kindly driver let me spend the day going back and forth to Churston.
being allowed to open the regulator was magical, the rest of the controls remain a mystery. A magical day. Little did I realise that in a few years it would all disappear…….apart from the loco which was the now preserved 1466.
aged 14/15 years of age a wonderful day to remember.
bigj

 

[LarryG]

Happy New Year Dave. Neat looking BR Caprotti Five there, but I am sorry to hear about the lack of motivation.

Your Fowler Cl. 3 2-6-2T was a work of art and there is no doubt in my mind that its appearance was down to the P4 chassis. But how long have we mere mortals got Dave? Having read of the difficulties you have had with some of your excellent builds, I often wondered (secretly) why you hadn't moved to 0 gauge seeing as track and scale are more closely matched thereby making super-detail and reliability easier to achieve.

 

[Dave Holt]

Thanks for the kind comments.

Larry, I agree about the time concerns. I suspect most of us will not complete all our modelling ambitions, but it's generally fun just ploughing on till we can't. I'm far too heavily invested in P4 to consider moving up to 7 mm, although I do have one 7 mm loco kit on order.

Jonte, There's an awful lot of questions, there, but I'll try to explain in simple terms.
For a loco to have working suspension, as you say, the wheels need to be able to move up and down to accommodate track irregularities. This helps keep the loco on the track when using scale flanges, as in P4 or S7, and also helps with electrical pick reliability by keeping all the wheels in contact with the rails.
There are two principal methods for model loco suspension - springing or beam compensation. I have built some fully sprung locos - mainly Brassmasters kits that are designed that way, but my preferred option is full floating beam compensation, which is what was used on the Caprotti loco. By "fully floating", I mean there is no fixed axle and all the axles are free to move up or down with the coupled axles running in axleboxes sliding in horn guides (the slots in the frames), as you say.
I think you've slightly confused two ideas regarding stopping the axles falling out. There is a method of spring suspension called Continuous Spring Beam (CSB) which uses two continuous spring wires (normally steel guitar strings), passing through mountings attached to the axleboxes and the frames, so they act as continuous beam and also prevent the axles falling out. I've built some tender chassis with this and it works very well if the spring diameter and vehicle weight are well matched. In my compensated locos, the axles are retained by a keeper plate attached under the frames. This usually also mounts the cosmetic axlebox springs and, sometimes, also the sand pipes and even the pick-up mountings.
I didn't photograph the Caprotti keeper but here is a photo of the keeper from another model, which shows the idea.

The amount of vertical movement in the coupled axleboxes is very small, certainly no more than +/- 0.5 mm, so the change in effective wheelbase is less than normal running clearances needed for smooth running. However, it is necessary to articulate the coupling rods where there are more than two axles. This is best done by providing a prototypical knuckle or gradient joint although many of me earlier efforts simply used the centre crank pin bush as the pivot.
On the Caprotti, the drive shafts are not articulated because the return crank gearboxes are not actually attached to the return cranks. They just sit in front of the crank, supported by the drive shafts ans torque reaction rods.
Hope that helps answer your questions.

Dave.

 

[simond]

This is indeed a wonderful piece of craftsmanship, Dave.

Unfortunately, I’ve always struggled to understand compensated chassis’ so please forgive my ignorance when I try and run it by you, in an effort to see if I’ve got the basics right. I do hope you don’t mind.

It appears that to start with, you either cut a square or rectangle (closed on three sides) into the chassis (frame?) in line with the wheels. Then, into the slots go some form of bearing, unfixed so they can slide up and down, with either a flange on one side or perhaps a slot to stop the wheels flaring out, through which the axles are threaded?
To stop the wheels falling out when you lift up the model, it appears that a set of (two?) wires run the length of the chassis, which either have loops at each end into which screws can be threaded (and thence into tapped holes in the chassis) or soldered to a central plate which can be fixed to the chassis in the same way with screws?

Moving onto the motion, does it mean that the holes for the crank pins and rods have to be ‘sloppier’ than on rigid chassis’, and if so, how do you gauge the maximum sloppiness allowed before it looks too sloppy a fit?

Then, moving onto instances like with this wonderful model, Dave, do the tubes and cylinder bits need to be articulated too rather than fixed to allow for the flexing of wheels on poor track?

It all really does seem quite complex and a wonderful feat of engineering.

As I say, would you or any other member kindly be able to put me right on this, and respectfully, without too much technicality, due to my mentioned ignorance of most of this intricate mechanical engineering.

Many thanks.

Jon

Jon

Start with the basics.

If your milk maid doesn’t want her stool to wobble, she will wisely choose one with three legs, because the only things that are flat are billiard tables and float glass.

Same principle - we need three legs, more accurately, we need three points of support to connect our wheels to the chassis, and if we don’t provide a mechanism, the chassis will settle with only one wheel on one side and two wheels on the other touching the track for 99.99% of the time - one wheel contact leads to poor pickup.

So we need the axles to be able to move independently, and a way of transferring the chassis load to them. Hence see-saw beams and axle boxes .

More to follow - lunch is served…

 

[Dave Holt]

Thanks, Simon.
I did rather neglect to explain how compensation works or can be achieved in practice.
I'll see what you come up with and then, perhaps, add some details of the specific arrangement on the Caprotti.
Dave.

 

[simond]

Hi Dave, I was waiting for a business meeting (in the pub , so filling in time, hopefully usefully…. Didn’t mean to tread on your toes!

our posts crossed, and happily we attacked the same question from different perspectives.

wholly agree with your point about fully floating compensation, and have been a proponent thereof for many years but I find myself a bit more inclined to CSB nowadays.

Love the loco. I don’t know where mojos go to hide, (they all do, sometimes, but I find they come home, eventually) but I’d be very happy to see more of your builds when you find yours!

cheers
Simon

 

[simond]

Jon,

part two…

ok, we need some means of allowing for imperfect track.

as we have seen, three legged stools sit without wobbling so we need the same effect. Three points of contact.

locos generally have even numbers of wheels, so the first trick is allowing an axle to rock across the chassis. This converts two wheels to one point of support. This is applicable to 0-4-0 chassis. One axle has fixed bearings (usually the driven one), and the other is allowed to rock from side to side by means of a fixed fulcrum in the middle of the axle. Some kind of guides are required to ensure the axle stays in the right plane - axleboxes and hornguides are perfect. Keeps can be used to ensure the “loose” axle doesn’t fall out.

0-6-0s present a number of challenges, and a number of possible solutions.

There’s an easy route: fix one axle (again, usually the driven one) and arrange a see-saw beam to rest in the middle of the other two axles. The see-saw beam can rock fore and aft (this is “pitch”) and the axles can rock from side to side (this is “roll”) and the combination of two axles in this way gives a single point of support at the middle of the see-saw beam. There are issues with this. It’s not fully floating, and the centre of gravity of the loco must fall well within the triangle defined by the two bearings of the fixed axle and the single point we have created. That might not work well in a 4-6-0 loco (assuming we ignore the potential load carrying of the bogie)

An alternative is to use a pair of close-to-the-frames see-saw beams to equalise the centre and rear axles, and a central pivot on the front axle, which moves the triangle forward by roughly half the front-centre wheelbase. It also ensures that all axles are fully floating. It’s more work, but much better, I think. The motor-gearbox needs to be floating to allow suspension movement, but constrained to avoid it rotating around the axle.

Four axle locos can be compensated by a combination of a central see-saw on the front two axles and a pair of close-to-the-frames see-saw beams to equalise the third and rear axles.

five axle locos are a pain. Use CSB!

hope this helps
Simon

 

[jonte]

Thanks for the kind comments.

Larry, I agree about the time concerns. I suspect most of us will not complete all our modelling ambitions, but it's generally fun just ploughing on till we can't. I'm far too heavily invested in P4 to consider moving up to 7 mm, although I do have one 7 mm loco kit on order.

Jonte, There's an awful lot of questions, there, but I'll try to explain in simple terms.
For a loco to have working suspension, as you say, the wheels need to be able to move up and down to accommodate track irregularities. This helps keep the loco on the track when using scale flanges, as in P4 or S7, and also helps with electrical pick reliability by keeping all the wheels in contact with the rails.
There are two principal methods for model loco suspension - springing or beam compensation. I have built some fully sprung locos - mainly Brassmasters kits that are designed that way, but my preferred option is full floating beam compensation, which is what was used on the Caprotti loco. By "fully floating", I mean there is no fixed axle and all the axles are free to move up or down with the coupled axles running in axleboxes sliding in horn guides (the slots in the frames), as you say.
I think you've slightly confused two ideas regarding stopping the axles falling out. There is a method of spring suspension called Continuous Spring Beam (CSB) which uses two continuous spring wires (normally steel guitar strings), passing through mountings attached to the axleboxes and the frames, so they act as continuous beam and also prevent the axles falling out. I've built some tender chassis with this and it works very well if the spring diameter and vehicle weight are well matched. In my compensated locos, the axles are retained by a keeper plate attached under the frames. This usually also mounts the cosmetic axlebox springs and, sometimes, also the sand pipes and even the pick-up mountings.
I didn't photograph the Caprotti keeper but here is a photo of the keeper from another model, which shows the idea.
View attachment 231058
The amount of vertical movement in the coupled axleboxes is very small, certainly no more than +/- 0.5 mm, so the change in effective wheelbase is less than normal running clearances needed for smooth running. However, it is necessary to articulate the coupling rods where there are more than two axles. This is best done by providing a prototypical knuckle or gradient joint although many of me earlier efforts simply used the centre crank pin bush as the pivot.
On the Caprotti, the drive shafts are not articulated because the return crank gearboxes are not actually attached to the return cranks. They just sit in front of the crank, supported by the drive shafts ans torque reaction rods.
Hope that helps answer your questions.

Dave.

Jon,

part two…

ok, we need some means of allowing for imperfect track.

as we have seen, three legged stools sit without wobbling so we need the same effect. Three points of contact.

locos generally have even numbers of wheels, so the first trick is allowing an axle to rock across the chassis. This converts two wheels to one point of support. This is applicable to 0-4-0 chassis. One axle has fixed bearings (usually the driven one), and the other is allowed to rock from side to side by means of a fixed fulcrum in the middle of the axle. Some kind of guides are required to ensure the axle stays in the right plane - axleboxes and hornguides are perfect. Keeps can be used to ensure the “loose” axle doesn’t fall out.

0-6-0s present a number of challenges, and a number of possible solutions.

There’s an easy route: fix one axle (again, usually the driven one) and arrange a see-saw beam to rest in the middle of the other two axles. The see-saw beam can rock fore and aft (this is “pitch”) and the axles can rock from side to side (this is “roll”) and the combination of two axles in this way gives a single point of support at the middle of the see-saw beam. There are issues with this. It’s not fully floating, and the centre of gravity of the loco must fall well within the triangle defined by the two bearings of the fixed axle and the single point we have created. That might not work well in a 4-6-0 loco (assuming we ignore the potential load carrying of the bogie)

An alternative is to use a pair of close-to-the-frames see-saw beams to equalise the centre and rear axles, and a central pivot on the front axle, which moves the triangle forward by roughly half the front-centre wheelbase. It also ensures that all axles are fully floating. It’s more work, but much better, I think. The motor-gearbox needs to be floating to allow suspension movement, but constrained to avoid it rotating around the axle.

Four axle locos can be compensated by a combination of a central see-saw on the front two axles and a pair of close-to-the-frames see-saw beams to equalise the third and rear axles.

five axle locos are a pain. Use CSB!

hope this helps
Simon

Dave/Simon:

My sincerest thanks to both.

As I predicted, there is more to this than meets the eye and much to chew over. With the complexity involved and different variables to address, Dave has done extremely well to construct a model of this size that both performs fluidly, while accurately mirroring the prototype.

I think, Simon, I may have seen an example or two of the rocking beams, which I think I’m right in saying is usually a non-fixed length of brass tube, to which is soldered a length of brass wire running length ways, and hung on a brass wire between the frames.

As for the ‘three-points’ idea, I bought a handbook several years ago by a guy whom I think was called ‘Mike’, explaining the principle, much of which unfortunately went over my head………

Thank you both again.

Jon

 

[Dave Holt]

Jon,

It was Mike Sharman - a great exponent of beam compensation, advocating a system known as "Flexichas".
I'll explain how I applied the principles outlined by Simon to the 4-6-0 Caprotti loco in a further post.
Dave.

 

[Terry]

A wonderful model of which you should be rightly proud. Referring back to your opening post, I always find that the answer to the inevitable lack of railway mojo is to take on a small totally unrelated project. In my case I usually resort to adding more bits to the small Micromodel Houses of Parliament card model, which has been under construction for some time. I have just taken delivery of a card bird kit for a Merlin which will be constructed next time the lack of railway mojo strikes. I find that after a week or two of non-railway modelling, the mojo soon returns. Just a suggestion.

Terry

 

[Ian@StEnochs]

Four axle locos can be compensated by a combination of a central see-saw on the front two axles and a pair of close-to-the-frames see-saw beams to
five axle locos are a pain. Use CSBs
Simon

When I started building locos in P4, in the early 70s!, I used the simply sprung horn box and guides designed by the MRSG and marketed by Studiolith. These were very simple to use and were available for carrying as well as driving wheels. This isn’t full springing, the model rides on adjustable screw stops, with a small spring which pushing wheels down into dips ensuring good contact. Other manufactures also produced similar horn boxes.

I did try Flexichas when it was written up in the press but found it just a bit too complicated on anything bigger than an 0-6-0 plus the beams got in the way of the valve gear.

Having moved onto S7, I am out of touch with the 4mm scene now, but still use the individual sprung axlebox in most of my locos. The only difference being that in 7mm scale the greater mass and bulk permits the use of full springing with the loco riding on the springs with wheels able to rise over bumps as well drop into dips.

Incidentally I still have a few Studiolith 1/8” units left in stock and will use them on the bogie of an 0-4-4T.

Ian

 

[jonte]

Jon,

It was Mike Sharman - a great exponent of beam compensation, advocating a system known as "Flexichas".
I'll explain how I applied the principles outlined by Simon to the 4-6-0 Caprotti loco in a further post.
Dave.

Mike Sharman, of course.

Many thanks, Dave. I shall look forward to it.

Jon

 

[Dave Holt]

Jon,

Hopefully, Simon and Ian have explained the basics of three point beam compensation and a simple part sprung approach to keeping all the wheels in touch with the rail head. These systems can be applied to any scale and wheel/track standards. However, in P4, with its scale flanges only 0.5 mm deep, keeping the wheels in touch with the track is even more critical. All my locos have some form of working suspension, mainly compensation. That said, quite a few P4 modellers successfully run re-wheels RTR loco that have nominally rigid chassis, but that does require track laying of a very high standard.
My first couple of P4 locos used the traditional Flexichas arrangement with a fixed driving axle and a single central beam between the other coupled axles. The front bogie on the 4-6-0 was just along for the ride and was not part of the suspension. All seemed well till the loco was run round an oval layout at express speed. On the end curves, the inner rear (fixed) wheel was seen to be lifting off the track and the loco was on the cusp of toppling over to the outside of the curve, rather like a kiddies tricycle turning too fast.
A thorough re-think came to the conclusion that, with the white metal boiler and cylinders ahead of the drivers, the loco centre of gravity (CoG) was too near the apex of the pivot point triangle that Simon mentioned. On taking the curves at speed, the centrifugal force had moved the effective CoG outside the triangle, causing instability.
The solution was to move the pivot points forward so that the loco CoG (roughly near the middle driving axle) was approximately 1/3 up from the base of the triangle. This gives both the best combination of weight distribution and stability against lateral forces.
This was achieved by moving the rear pivot to half way between the rear two axles, which had independent rocking beams, and the front, single beam, pivot to between the front axle and the centre of the front bogie. The front end of the beam rests on the top of a plunger inside a hollow bogie pivot, the bottom of which rests on a tube linking the bogies external compensating beams. This arrangement is rather more complicated than most people use, but has the advantage of enabling the bogie wheels to take a prototypical share of the weight. Indeed, I calculate the exact pivot points to give the same weight distribution as the prototype (ignoring the axle hung motor/gearbox effects).
I didn't take any photos of the Caprotti showing these arrangements but, as this is my standard arrangement for 4-6-0s, a photo of the chassis for my LMS Black 5 Caprotti illustrates the arrangement.

The top of the LH rear beam can be seen linking the rear two axles and the front, single beam can just be made (partially obscured by a representation of the train heating pipe) out between the centre of the bogie and the front coupled axle.
Here's the front bogie frames for the BR Caprotti, showing the hollow pivot tube for the plunger, the outside compensation beams and the frame side bearer plate.

And here's a sketch explaining the front beam/hollow bogie pivot principle.


Besides distributing a prototypical share of the weight to be carried by the bogie, it also allows the bogie frames to be independent of the suspensions system and pivot/slide, without bobbing up and down, exactly as per the prototype.
I don't expect anyone to take up this arrangement but hope it helps explain my thinking and I like to think it is a significant factor the smooth track holding of my locos that are equipped with it.
Dave.

 

[40057]

That is an awesomely good piece of work. I don’t know how you do it in such a small size. Fantastic.

 

[jonte]

Jon,

Hopefully, Simon and Ian have explained the basics of three point beam compensation and a simple part sprung approach to keeping all the wheels in touch with the rail head. These systems can be applied to any scale and wheel/track standards. However, in P4, with its scale flanges only 0.5 mm deep, keeping the wheels in touch with the track is even more critical. All my locos have some form of working suspension, mainly compensation. That said, quite a few P4 modellers successfully run re-wheels RTR loco that have nominally rigid chassis, but that does require track laying of a very high standard.
My first couple of P4 locos used the traditional Flexichas arrangement with a fixed driving axle and a single central beam between the other coupled axles. The front bogie on the 4-6-0 was just along for the ride and was not part of the suspension. All seemed well till the loco was run round an oval layout at express speed. On the end curves, the inner rear (fixed) wheel was seen to be lifting off the track and the loco was on the cusp of toppling over to the outside of the curve, rather like a kiddies tricycle turning too fast.
A thorough re-think came to the conclusion that, with the white metal boiler and cylinders ahead of the drivers, the loco centre of gravity (CoG) was too near the apex of the pivot point triangle that Simon mentioned. On taking the curves at speed, the centrifugal force had moved the effective CoG outside the triangle, causing instability.
The solution was to move the pivot points forward so that the loco CoG (roughly near the middle driving axle) was approximately 1/3 up from the base of the triangle. This gives both the best combination of weight distribution and stability against lateral forces.
This was achieved by moving the rear pivot to half way between the rear two axles, which had independent rocking beams, and the front, single beam, pivot to between the front axle and the centre of the front bogie. The front end of the beam rests on the top of a plunger inside a hollow bogie pivot, the bottom of which rests on a tube linking the bogies external compensating beams. This arrangement is rather more complicated than most people use, but has the advantage of enabling the bogie wheels to take a prototypical share of the weight. Indeed, I calculate the exact pivot points to give the same weight distribution as the prototype (ignoring the axle hung motor/gearbox effects).
I didn't take any photos of the Caprotti showing these arrangements but, as this is my standard arrangement for 4-6-0s, a photo of the chassis for my LMS Black 5 Caprotti illustrates the arrangement.
View attachment 231157
The top of the LH rear beam can be seen linking the rear two axles and the front, single beam can just be made (partially obscured by a representation of the train heating pipe) out between the centre of the bogie and the front coupled axle.
Here's the front bogie frames for the BR Caprotti, showing the hollow pivot tube for the plunger, the outside compensation beams and the frame side bearer plate.
View attachment 231158
And here's a sketch explaining the front beam/hollow bogie pivot principle.
View attachment 231156

Besides distributing a prototypical share of the weight to be carried by the bogie, it also allows the bogie frames to be independent of the suspensions system and pivot/slide, without bobbing up and down, exactly as per the prototype.
I don't expect anyone to take up this arrangement but hope it helps explain my thinking and I like to think it is a significant factor the smooth track holding of my locos that are equipped with it.
Dave.

Thank you, Dave.

I shall sit down later this evening and thoroughly assimilate.

Jon

 

[Dave Holt]

Thanks for your kind comments 40057.
Not sure if your tag is an EE type 4 or Fowler 3MT 2-6-2T. Just in case it's the latter, here's my attempt at 40056. Here the chassis is compensated as an 0-6-0, with twin beams at the rear and a fixed, single rocking fulcrum at the front. Both pony trucks are sprung.

The loco was built from an Alan Gibson kit and the body was painted, lined and numbered by Ian Rathbone and weathered by David Clarke.
Dave.