Ratio Midland Carriage bogies

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Neil Smith
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Ratio Midland Carriage bogies

Postby Neil Smith » Thu Feb 27, 2020 6:15 pm

Hi all,
I have been voraciously exploring this Forum for a couple of months, learning loads in the process, so thank you all for creating such a wonderful resource. And while I have made the odd post already, this is my first topic, so I better start by introducing myself.
I have been away from modelling for 3 decades, but having turned 50 last October I felt the time was right to scratch an itch that was becoming increasingly difficult to ignore! Back in my childhood I had a 00 layout, which was pretty much RTR with some scratchbuilt buildings, and a few Ratio kit coaches and wagons. In my teens I moved to SM32 in the garden, but I've done nothing in railway modelling since.
In deciding to (re)start, I knew that I needed to explore going down the finescale route and so here I am!
And one of my first projects is to pick up where I left off circa age 13 with a Ratio kit, this time one of the Midland Clayton clerestories. I realise these maybe do not represent the highest end of the hobby, but it is a chance to get my eye back in. However if I am to stand a chance of doing the job properly, I could do with picking the collective brains on here about a few things...
Firstly, I will be replacing the 10' bogies with etched, sprung ones (using the Ratio sides as cosmetic sideframes). It seems the choice is between the Bill Bedford ones (via Eileens) and Dave Bradwell. My questions are - what are the comparative experiences for building these, the running qualities etc. What do you gain from buying the secondary suspension kit for the Bill Bedfords, and if you do this, are there any instructions for this? All help would be welcome as if my magnum opus ever comes off I will need quite a few of these carriages!
Secondly I have some prototype questions that have not been answered by reading the Lacy/Dow Midland Railway Carriages book Vol 1. Does anyone have a drawing of the brake arrangements for these, at least as far as brake hangers are concerned as the kit has a V moulded onto the trusses/middle footboard section, but no corresponding V inside between which a rod would normally sit, and the kit has the gas cylinder on the opposite side - so no room for a V hanger there. Any ideas? Lacy/Dow does have pictures of earlier Clayton coaches with a clear view of the V hanger arrangement but I have no idea if he kept the same chassis design when he revolutionised the coach bodies on top come the 1890s. Also the Ratio kit - and indeed the Miscellany Models kit of the full brake 6 wheeler, both have/advise that the handle on the end of the carriage alongside the steps up to the roof has a gentle curve. But all the photos I have seen of these Clayton coaches (in Lacy & Dow and elsewhere) have a straight handle. Any ideas (again)?
And thirdly before I set up a jig to try and make the distinctive L shaped commode handles to replace the moulded ones (not sure I can get a crisp right angle by bending..), can anyone advise whether there are such things available to buy and whether this is a worthwhile investment?
Thank you in advance for your help...
Best wishes
Neil

billbedford
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Re: Ratio Midland Carriage bogies

Postby billbedford » Fri Feb 28, 2020 9:08 am

Neil Smith wrote:Secondly I have some prototype questions that have not been answered by reading the Lacy/Dow Midland Railway Carriages book Vol 1. Does anyone have a drawing of the brake arrangements for these, at least as far as brake hangers are concerned as the kit has a V moulded onto the trusses/middle footboard section, but no corresponding V inside between which a rod would normally sit, and the kit has the gas cylinder on the opposite side - so no room for a V hanger there. Any ideas?


The brake pull rod to the bogies had to be on the centre line of the coach (think about it). So the inn v-hanger was placed on a longitudinal stringer on the opposite side of the coach to the v-hanger on the solebar. This arrangement was universal for vacuumed braked coaches. See the plan of a six-wheeled underframe on p165 of L&D vol1.

Also the Ratio kit - and indeed the Miscellany Models kit of the full brake 6 wheeler, both have/advise that the handle on the end of the carriage alongside the steps up to the roof has a gentle curve. But all the photos I have seen of these Clayton coaches (in Lacy & Dow and elsewhere) have a straight handle. Any ideas (again)?


Follow the photos -- always, except for vehicles known to be in preservation.
Bill Bedford
Mousa Models
http://www.mousa.biz

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Neil Smith
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Re: Ratio Midland Carriage bogies

Postby Neil Smith » Fri Feb 28, 2020 9:49 am

billbedford wrote:The brake pull rod to the bogies had to be on the centre line of the coach (think about it). So the inn v-hanger was placed on a longitudinal stringer on the opposite side of the coach to the v-hanger on the solebar. This arrangement was universal for vacuumed braked coaches. See the plan of a six-wheeled underframe on p165 of L&D vol1.


Thank you Bill - I will have another look at that drawing this evening. Generally what you say is what my thinking had been but wanting to double check. The other conflicting issue here is that the Ratio model has a gas cylinder located on the far side of the chassis to the sole modelled V hanger on each side. And it has two vac cylinders rather than just the one that you'd find on more modern coaches. Would there really have been two brake cylinders per coach? If there were then the gas cylinders were probably arranged as Ratio has them, but if only one brake cylinder I would have thought you'd have the brake cylinder with associated V hangars and rodding taking up the width of one half of the central portion of the underframe and both gas bottles taking up the other half? But can anyone confirm?

Also the Ratio kit - and indeed the Miscellany Models kit of the full brake 6 wheeler, both have/advise that the handle on the end of the carriage alongside the steps up to the roof has a gentle curve. But all the photos I have seen of these Clayton coaches (in Lacy & Dow and elsewhere) have a straight handle. Any ideas (again)?

billbedford wrote:Follow the photos -- always, except for vehicles known to be in preservation.


Hence my quandry - does Mark Tatlow or anyone have any photographic evidence to contradict this please?

Finally Bill - do you have any advice about the earlier question about secondary suspension of the bogies please?

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Noel
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Re: Ratio Midland Carriage bogies

Postby Noel » Fri Feb 28, 2020 12:07 pm

Neil Smith wrote:And it has two vac cylinders rather than just the one that you'd find on more modern coaches. Would there really have been two brake cylinders per coach?


I don't know about the Midland, but it was standard practice on BR, LMSR, GWR and LNER [and, so far as I know, SR] for bogie coaches, and bogie NPCCS vehicles as well, to have two vacuum cylinders. They were generally the heaviest VB single vehicles on the railway until the 1960s [when some VB freight stock started to have two cylinders as well, because of their weight] and one cylinder wouldn't do the job adequately. The rules changed when BR switched to the more efficient air brake.
Regards
Noel

billbedford
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bogie coaches

Postby billbedford » Fri Feb 28, 2020 12:33 pm

Neil Smith wrote:
billbedford wrote:The brake pull rod to the bogies had to be on the centre line of the coach (think about it). So the inn v-hanger was placed on a longitudinal stringer on the opposite side of the coach to the v-hanger on the solebar. This arrangement was universal for vacuumed braked coaches. See the plan of a six-wheeled underframe on p165 of L&D vol1.


Thank you Bill - I will have another look at that drawing this evening. Generally what you say is what my thinking had been but wanting to double check. The other conflicting issue here is that the Ratio model has a gas cylinder located on the far side of the chassis to the sole modelled V hanger on each side. And it has two vac cylinders rather than just the one that you'd find on more modern coaches. Would there really have been two brake cylinders per coach? If there were then the gas cylinders were probably arranged as Ratio has them, but if only one brake cylinder I would have thought you'd have the brake cylinder with associated V hangars and rodding taking up the width of one half of the central portion of the underframe and both gas bottles taking up the other half? But can anyone confirm?


All vac braked bogie coaches were fitted with an independent brake cylinder for each bogie, these were usually arranged diagonally opposite to each other, with gas tanks or battery boxes in the spaces directly opposite.


Also the Ratio kit - and indeed the Miscellany Models kit of the full brake 6 wheeler, both have/advise that the handle on the end of the carriage alongside the steps up to the roof has a gentle curve. But all the photos I have seen of these Clayton coaches (in Lacy & Dow and elsewhere) have a straight handle. Any ideas (again)?

billbedford wrote:Follow the photos -- always, except for vehicles known to be in preservation.


Hence my quandry - does Mark Tatlow or anyone have any photographic evidence to contradict this please?


I've no idea what info Mark has, but photos tell you what was there, while authors tend to tell you what they think should have been there.

Finally Bill - do you have any advice about the earlier question about secondary suspension of the bogies please?


Secondary springing tends to be a personal thing. Some people think they are the bee's knees, others can't be bothered with them. I'm afraid you are going to have to do your own experiments and decide for yourself.
Bill Bedford
Mousa Models
http://www.mousa.biz

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Neil Smith
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Re: Ratio Midland Carriage bogies

Postby Neil Smith » Fri Feb 28, 2020 1:06 pm

Thank you Noel - I stand corrected!

So if there were indeed two brake pots, do I presume that the second V hangar was just past the centre line of the coach (i.e. between the centreline and the gas cylinder on the opposite side to the vacuum cylinder)?

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Neil Smith
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Re: bogie coaches

Postby Neil Smith » Fri Feb 28, 2020 1:14 pm

billbedford wrote:All vac braked bogie coaches were fitted with an independent brake cylinder for each bogie, these were usually arranged diagonally opposite to each other, with gas tanks or battery boxes in the spaces directly opposite.


billbedford wrote:Secondary springing tends to be a personal thing. Some people think they are the bee's knees, others can't be bothered with them. I'm afraid you are going to have to do your own experiments and decide for yourself.


Thanks Bill for all this.

Does anyone have any other views on secondary springing for coach bogies before I put an order in?

All the best

Neil

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Noel
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Re: Ratio Midland Carriage bogies

Postby Noel » Fri Feb 28, 2020 3:27 pm

Neil Smith wrote:So if there were indeed two brake pots, do I presume that the second V hangar was just past the centre line of the coach (i.e. between the centreline and the gas cylinder on the opposite side to the vacuum cylinder)?


The best advice I can give is - If you want to be sure that you have got it right, don't presume! I'm interested in post-grouping and BR, so don't know about Midland practices, but the LMS, which basically followed late MR practice, generally used symmetrical arrangements with offset cylinders in the same relative position at each end. Coach underframes had four main horizontal members, including the solebars, so the cross shafts were between the solebar and the inner member nearer the other solebar, so that the connections to the bogies were on the centre line.

There have been books about Midland coaches; none are in print currently, so far as I know, but may be available second hand, although at what cost I don't know. Alternatively, "David Jenkinson's Historic Carriage Drawings Vol. 2 - LMS and Constituents" [also out of print but more recent, I think] may be helpful [I don't have a copy, so I can't comment on its content; Vol. 3, NPCCS, only has MR 4- and 6-wheel stock]. There is also the Midland Railway Society http://www.midlandrailway.org.uk/, and various museums may have drawings.
Regards
Noel

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zebedeesknees
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Re: Ratio Midland Carriage bogies

Postby zebedeesknees » Fri Feb 28, 2020 5:15 pm

Neil Smith wrote:
billbedford wrote:Secondary springing tends to be a personal thing. Some people think they are the bee's knees, others can't be bothered with them. I'm afraid you are going to have to do your own experiments and decide for yourself.


Thanks Bill for all this.

Does anyone have any other views on secondary springing for coach bogies before I put an order in?

All the best

Neil


It's all down to perceived ride quality. As Bill suggests, it's subjective. For example, if you're happy with the ride of a compensated 6-coupled with a rigid axle, then don't bother.
Ted.

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Neil Smith
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Re: Ratio Midland Carriage bogies

Postby Neil Smith » Fri Feb 28, 2020 8:48 pm

Thank you Noel, I will follow up those suggestions.

And thank you Ted, that does make sense. I think I will perhaps do some experimenting and see what works best, or perhaps even just well enough, for me.

**writes note to self.. Better hurry up and make that test plank too....** :D

Final question for now (from in amongst my OP) does anyone make Clayton L shaped commode handles?

All the best,

Neil

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Mark Tatlow
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Re: Ratio Midland Carriage bogies

Postby Mark Tatlow » Sat Feb 29, 2020 10:28 am

Hi Neil,

Coming back to you on a couple of the points.

End handrail

I have taken another look at this and as you say, the Ratio kits have this on a gentle curve and I copied this in my build. Looking at both the Midland Railway carriages and my other big source book (Carriage Modelling Made Easy by the late David Jenkinson - very well worth it I suggest) I tend to agree with you that they were straight on at least the majority of the Bain clerestory and arc roof stock. There is a model in the NRM of the full brake I have produced a kit for and this has straight handrails too.

NRM MR Full Brake.jpg

One caution I would make is things did change over time and some of these coaches were in production for quite some time, so things changed. To illustrate this, take a look at this coach at the NRM that does show a gentle arc to the end handrail:

https://images-wixmp-ed30a86b8c4ca88777 ... lOTUzeR294

The problem is that we are at the stage where nobody truly now knows due to the passage of time and limited people with the interest in the topic. If you have studied this point at length in the photographs, you could well now find yourself as the foremost expert on end handrails on Midland coaches!

I share Bill's stance that if you have a photograph of it, you know it was right at least one point in time and that can be better than drawings/writings. Certainly this is the case with the full Midland full brake, the Slaters kit is different to the drawing in Dow and both are different to the photograph in Dow! Then when you look at the model in the NRM (which may be a contemporary model) it is different again. I followed the the photograph in Dow with the overall dimensions from the drawing in the same source and left it at that!

Secondary Springing

There is no right and wrong answer to this and preference comes into it. I didn't really get on with Bill Bedord's secondary springing but I like his primary springing solution so I don't both with the former. Conversely, I do like the Rumney Models bogie springing which includes primary and secondary springing and I do think the vehicles glide realistically as a result.

So try one way with one and the other with a second one to form your own view.

Hope this helps?


Mark
Mark Tatlow

MPR
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Re: Ratio Midland Carriage bogies

Postby MPR » Sat Feb 29, 2020 11:54 am

Building and modification of the Ratio Clayton kits are covered in Stephen Williams’ “The 4mm Coach” books published by Wild Swan. There are drawings and some prototype photos also.

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Neil Smith
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Re: Ratio Midland Carriage bogies

Postby Neil Smith » Sun Mar 01, 2020 10:00 pm

Mark Tatlow wrote:End handrail
I have taken another look at this and as you say, the Ratio kits have this on a gentle curve and I copied this in my build. Looking at both the Midland Railway carriages and my other big source book (Carriage Modelling Made Easy by the late David Jenkinson - very well worth it I suggest) I tend to agree with you that they were straight on at least the majority of the Bain clerestory and arc roof stock. There is a model in the NRM of the full brake I have produced a kit for and this has straight handrails too.
One caution I would make is things did change over time and some of these coaches were in production for quite some time, so things changed.


Thank you Mark - this is most reassuring, I had been fretting that you may have access to some stash of information unknown to me (and my stash is fairly limited tbh)!

Mark Tatlow wrote:The problem is that we are at the stage where nobody truly now knows due to the passage of time and limited people with the interest in the topic. If you have studied this point at length in the photographs, you could well now find yourself as the foremost expert on end handrails on Midland coaches!


This made me laugh out loud... The "foremost expert on end handrails on Midland coaches" ??!?! :o

Mark Tatlow wrote:I share Bill's stance that if you have a photograph of it, you know it was right at least one point in time and that can be better than drawings/writings. Certainly this is the case with the full Midland full brake, the Slaters kit is different to the drawing in Dow and both are different to the photograph in Dow! Then when you look at the model in the NRM (which may be a contemporary model) it is different again. I followed the the photograph in Dow with the overall dimensions from the drawing in the same source and left it at that!


Yes at some point you just have to pin a tail on a particular donkey and decide that this is how it was, and how it should be modelled, I think I am at that point now, so thank you.

Mark Tatlow wrote:Secondary Springing
There is no right and wrong answer to this and preference comes into it. I didn't really get on with Bill Bedord's secondary springing but I like his primary springing solution so I don't both with the former. Conversely, I do like the Rumney Models bogie springing which includes primary and secondary springing and I do think the vehicles glide realistically as a result.
So try one way with one and the other with a second one to form your own view.


As of yet Rumney Models don't do a 10' bogie, so that option is not there for me in this instance. I do think that some experimentation is in order, but before I send off an order to Eileens, may I just ask you Mark what it was about the secondary springing that you "didn't really get on with" - was it something to do with the making, or the results from using this secondary springing unit, or indeed something else please?

All the best

Neil

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Neil Smith
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Re: Ratio Midland Carriage bogies

Postby Neil Smith » Sun Mar 01, 2020 10:01 pm

MPR wrote:Building and modification of the Ratio Clayton kits are covered in Stephen Williams’ “The 4mm Coach” books published by Wild Swan. There are drawings and some prototype photos also.


Thank you MPR - I had spotted reference to this in the Other Place, and getting hold of a copy is on the wish list!

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Re: Ratio Midland Carriage bogies

Postby davebradwell » Mon Mar 02, 2020 11:30 am

A neglected line of reasoning in favour of all springing occurs when propelling sufficient vehicles for those next to the engine to be held by their buffers and hence prevented from following any dips in the rails. Only springs can maintain any pressure on the wheels to keep the thing from climbing over the rails. Just increasing the coach weight also increases the buffing forces and doesn't help, assuming all coaches weigh the same, of course. Secondary springs increase the range of travel as they are usually quite a low rate so should give a greater resistance to derailment. Gangways, too, are a major factor in all this as even when very lightly sprung they tend to discourage bodies from moving with respect to each other.

You need some sort of suspension between body and bogies even if it's just 3 point in order to allow the thing to follow track twist and secondary springing can be as simple as any other arrangement.

DaveB

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Neil Smith
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Re: Ratio Midland Carriage bogies

Postby Neil Smith » Mon Mar 02, 2020 12:36 pm

davebradwell wrote:A neglected line of reasoning in favour of all springing occurs when propelling sufficient vehicles for those next to the engine to be held by their buffers and hence prevented from following any dips in the rails. Only springs can maintain any pressure on the wheels to keep the thing from climbing over the rails. Just increasing the coach weight also increases the buffing forces and doesn't help, assuming all coaches weigh the same, of course. Secondary springs increase the range of travel as they are usually quite a low rate so should give a greater resistance to derailment. Gangways, too, are a major factor in all this as even when very lightly sprung they tend to discourage bodies from moving with respect to each other.
You need some sort of suspension between body and bogies even if it's just 3 point in order to allow the thing to follow track twist and secondary springing can be as simple as any other arrangement.
DaveB


Hi Dave

That is a good point that yes I hadn't thought of or seen expressed before - I was already convinced that springing was the way forward, but from the often expressed views that it produces a gliding rather than bouncing vehicle and therefore looks more prototypical, especially given that the bounce will be at a different vibration to what you'd see in the full size version.

I am now even more convinced to go down this route!

All the best

Neil

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zebedeesknees
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Re: Ratio Midland Carriage bogies

Postby zebedeesknees » Mon Mar 02, 2020 6:57 pm

Neil Smith wrote:
I am now even more convinced to go down this route!

All the best

Neil


Neil, this might be helpful:- http://www.clag.org.uk/beam-annex5.html

The 'planes of freedom' diagram is important, and the application of the rotations of the bogie frame relative to the carriage body can make a difference; in the yaw plane it's obvious that it should be free, but the bogie frame should be free to move in both the other rotations subject to the limits of space under the body. It is tempting to fit a good bearing to the pivot, but if it causes inhibitions in those freedoms the secondary springs will not work well. The bush pictured is a loose fit in the pivot hole in the bogie frame to enable this. It was cut from 3mm o.d. tube, 2.4mm long, and held with an M2 set screw.

The picture below shows my application which I found provided exactly the glide quality mentioned by Mark, using in this case .014" wires 17mm (a) apart, and Bill's secondary mountings packed by 1.3mm (c). This is going to be individual to the carriage design and weight, of course.

The implications of the 'top box' dimension (b) was the subject of some research (okay. trial and error!) resulting in the change from 5mm in the case of the Pendlenton bogie to 9mm, and also the idea (Bill's) that the spring wires ride on the edges of the box rather than a plank so as to minimise friction in the yaw plane. The effect of this increase is to control the rate of change of pitch in the bogie frame, which gives the primary springs time to do the job they are supposed to do. A knife edge here defeats the function of the primary springs to some extent, and does not provide enough control of the roll freedom of the body.

Secondary springs.jpg
Bedford bogie and secondary springs under Bachmann Mk1


It is my contention that the benefits in trackholding and ride quality far outweigh the time and effort.

But then, I would say that, wouldn't I?

Ted.

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Re: Ratio Midland Carriage bogies

Postby DavidM » Mon Mar 02, 2020 9:47 pm

That’s very interesting Ted, and most helpful.
Are you adding much extra weight to these coaches? And what do you regard as the ideal final weight using this approach?

David Murrell

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Mark Tatlow
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Re: Ratio Midland Carriage bogies

Postby Mark Tatlow » Mon Mar 02, 2020 9:59 pm

Neil Smith wrote:As of yet Rumney Models don't do a 10' bogie, so that option is not there for me in this instance. I do think that some experimentation is in order, but before I send off an order to Eileens, may I just ask you Mark what it was about the secondary springing that you "didn't really get on with" - was it something to do with the making, or the results from using this secondary springing unit, or indeed something else please?
l


Hi Neil

As you say, Rumney do not produce a 10 ft bogie - maybe we should petition Justin at Scalefour North...……..

His secondary springing is achieved by springing a bolster that telescopes in a socket in the bogie. As such the bogie is self contained and the bolster simply rotates with it and transfers the loads by a rubbing plate that is fixed (or even part of) the chassis. Although this is my Fox bogie, this is based on the Rumney bogie (it is part designed by Justin) and you can see the bolster - the wires that you can see poking out are the suspension springs.

IMG_0445 (3).JPG


Whilst you can't see the springing in the second picture, the projecting bolster is quite visible.

IMG_0525 (3).JPG

As Ted's picture shows, the secondary springing on the Bill Bedford bogies is attached to the chassis and the top of the bogie bears on this. I found it more difficult to set up and get level/straight and then the bogie could get caught on it. It may well be that I just never got the hang of it, as I can see Ted has but I stopped using them!

I do agree with Dave's comments that you need to allow the bogies to rock; springing can do this or a simple piece of wire on a bearing plate that the bogie can rock on like this.

Bachmann Coach.jpg
Mark Tatlow

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Neil Smith
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Re: Ratio Midland Carriage bogies

Postby Neil Smith » Mon Mar 02, 2020 10:14 pm

Hi Ted,

I second DavidM's praise! OK it took me a while reading your post, and the CLAG page which I had stumbled across a week or so ago, but now lights have gone on! So thank you. I have a feeling that once the bits of brass arrive in due course I will be referring back to your post and pictures as I start prodding the soldering iron about!

I too would be interested to know the weight (sorry Bachmann Mark 1s are about 40 years too late for me and no idea what they weigh from the shop, nor what extra may have been added)?

All the best

Neil

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Neil Smith
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Re: Ratio Midland Carriage bogies

Postby Neil Smith » Mon Mar 02, 2020 10:24 pm

And while I was writing my last post, Mr Tatlow was busy publishing too! Thank you Mark for so fulsomely answering my question about the various options around secondary springing. I can see the potential for the top box to snag on the secondary wires on the BB bogie, I would guess particularly if the yaw of the bogie was greater than the maximum rotation that would keep the top box edge within the constraints of the spring wire - and equally looking further back in this thread, for secondary suspension to work well, the two sides need to be set at a greater distance apart -so this is a balancing act. Much food for thought!

EDIT forgot to also say: I do intend to be at Scalefour North on the Sunday (presuming it hasn't been banned by the Government by then) so yes lobbying Justin about a ten footer may be on the cards!

All the best

Neil

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zebedeesknees
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Re: Ratio Midland Carriage bogies

Postby zebedeesknees » Tue Mar 03, 2020 4:40 pm

DavidM wrote:Are you adding much extra weight to these coaches? And what do you regard as the ideal final weight using this approach?

David Murrell


Ahhh, weight of our models... we did this to death on the old E4um... a can o'worms lined with bones of contention...

Few, I suspect will agree, but I 'scale' weight in order to try to keep everything proportional. An imperial ton converts to 1016Kg, dividing by 76.2 cubed results in 2.3g. For both practicality and convenience I try to make all my locos and stock weigh 4g per prototype ton. Emphasis on try...

The Bachmann Mk1s weigh 140g with bogies, so for me that's just about right, hence nothing added.

Neil Smith wrote:Hi Ted,

OK it took me a while reading your post, and the CLAG page which I had stumbled across a week or so ago, but now lights have gone on! So thank you.


Most welcome..

I have a feeling that once the bits of brass arrive in due course I will be referring back to your post and pictures as I start prodding the soldering iron about!
All the best
Neil


Thanks both. There is a lot more theory we could get into, but that should be in a new dedicated thread. One point though - the supports for the secondary wires could be made up from handrail knobs in the same way as the original CSB supports on the CLAG site. (sorry Bill!) It would then be easy enough to vary the length of the wires to suit whatever weight they need to carry. But be cautious about going too far from the specs given, there are implications and possibly unintended consequences...

Ted.
Last edited by zebedeesknees on Tue Mar 03, 2020 7:48 pm, edited 1 time in total.

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Re: Ratio Midland Carriage bogies

Postby davebradwell » Tue Mar 03, 2020 6:02 pm

I feel the piece on the CLAG site introduces some misconceptions with the Pendlenton bogie so would make the following comments:

We've made a number of small changes to the Pendlenton bogie, mainly to improve assembly and I'm about to commit to new tooling for the 8ft 6in. Other stock has been run down. The secondary springs are now a little further apart - they were narrowed in the original commercial version to make it suitable for 00 and this reversion improves body stability. We've never seen a reason to control pitch directly (but see later), in another world it would be called equalisation, and the working part of the bolster is now narrower as a result of other improvements. They've been run at well over a scale 100 so it doesn't seem an issue. Also you'd have to explain to me why a knife edge support has less friction than a flat plate - I was always taught it was essentially independent of area, if dry.

The analysis on the CLAG site misses an important feature of the Pendlenton bogie which is the low point of contact with the centre pivot. This makes your quoted secondary spring spacing misleading as the effective spacing is greater - the body rocks about this low point rather than mid way between the wires. This feature gives a lower roll frequency as it's a longer inverted pendulum. It also introduces damping into the pitching as the bolster has to slide on the secondary springs. It's possible to introduce damping into the roll by setting the bolster low and restoring correct coach height by tightening the retaining nut, although I can't understand which is the damping element in this case. If you just rest the body loosely on a pair of secondary springs there is a real danger it will just sit there and wobble. You want a slow sway.

Newtons, bah! Can't we just assume we're on planet Earth?

DaveB

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zebedeesknees
Posts: 93
Joined: Mon Jul 12, 2010 5:15 pm

Re: Ratio Midland Carriage bogies

Postby zebedeesknees » Tue Mar 03, 2020 7:55 pm

Hi Dave, the original question was, I think, about whether fitting secondary suspension to carriage bogies was worth it, and I feel that we have agreed that it is. If you wish to discuss the pros and cons of different designs, such as the Bedford or Pendelenton ones, I would suggest that you start a new thread on the subject, where I will consider whether to engage.
Regards,
Ted.

davebradwell
Posts: 259
Joined: Fri Jan 18, 2019 3:48 pm

Re: Ratio Midland Carriage bogies

Postby davebradwell » Tue Mar 03, 2020 9:05 pm

I wasn't aware I was entering a discussion about types of springing, merely correcting some mis-information about my product. I'd kept out of it so far.

DaveB


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