Coach and DMU springing units for Mostyn

Richard Oldfield
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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Fri Jan 27, 2023 5:13 pm

Hi Paul,

Paul Townsend wrote:What is the etch thickness, it looks like 18 thou


It is 0.3mm / 12 thou.

Cheers,

Richard

Crepello
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Re: Coach and DMU springing units for Mostyn

Postby Crepello » Sat Jan 28, 2023 12:51 pm

Perhaps a small "T" for Top half-etched where the bogie pivot will cover it, would jog
the distracted/absent-minded into always starting with the correct side up?

Richard Oldfield
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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Tue Jan 31, 2023 11:55 am

Hi,

Crepello wrote:Perhaps a small "T" for Top half-etched where the bogie pivot will cover it, would jog
the distracted/absent-minded into always starting with the correct side up?


Good suggestion - which we may take up if the etch design needs further modification. Until then a Sharpie will do the job until the bogie pivot goes in (step 2).

Cheers,

Richard

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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Tue Jan 31, 2023 12:38 pm

Hi,

Moving a bit further along ....

9. Fold out the anti-rotation tabs 90 degrees and solder.
Coach Springing Unit anti rotation tabs.jpg


10. Place the bearer pads over the anti-rotation tabs and solder such that the raised bearer surfaces are not contaminated with solder.
Coach Springing Unit bearer pads.jpg


11. Fold out the bearing carrier retaining tabs 90 degrees. Do not be tempted to do this at an earlier stage as this fold is not soldered for additional strength.
Coach Springing Unit bearing carrier retaining tab.jpg


12. Feed the springs in from one end over the central four tabs (over/under/under/over) such that they are equidistant from each end.
Coach Springing Unit spring location.jpg


Cheers,

Richard
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Richard Oldfield
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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Tue Jan 31, 2023 1:03 pm

Hi,

Time for some cleverly-designed bearing carrier assembly .....,

13. Separate pinpoint bearing carriers from fret and fold them at 180 degrees with the half-etch to the outside. Insert a waisted pinpoint bearing in the carrier recess and then solder sparingly below the hook only so that the pinpoint bearing and bearing carrier halves are soldered together without any solder penetrating the upper slot. I can just about hold a pair of tweezers and a cocktail stick in one hand whilst soldering with the other.
Coach Springing Unit folded bearing carrier.jpg

Coach Springing Unit folded bearing carrier soldering.jpg


The bearing carriers are, of course, handed.

Please note that this was a test build using Markits bearings. In practice we have found it better to use a bearing with shallower coning (around 1.2mm depth) such as the Keen Maygib product - REMEMBER slop is our enemy!!

Cheers,

Richard
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Richard Oldfield
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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Thu Feb 09, 2023 4:15 pm

Hi folks,

I'm afraid actual modelling has had to take priority over writing about it on forums but here is the next part of the coach springing unit story.

The next step is to mount the wheelsets and I find it easiest to do this by putting two opposite-handed bearing carriers at the ends of a wheelset, locating the wheelset within the w-irons and then rotating the bearing carriers until they latch onto the anti-rotation tabs. If you are lucky this action will position the spring within the barring carrier slot but, if you are more like me, this is when the spring location tool earns its keep.

A couple of images follow without the wheelset in place in order to show the sequence:-

Initial position of bearing carrier.
coach springing unit bearing carrier1.jpg


Bearing carrier rotated to latch onto anti-rotation tab (without engaging spring in bearing carrier slot.
coach springing unit bearing carrier2.jpg


Use of spring location tool to push spring up and across to
locate it in the bearing carrier slot.
coach spring unit location tool.jpg


Bearing carrier fully installed.
coach springing unit bearing carrier3.jpg



Now with the wheelsets:


Wheelset loosely in w-irons before rotating bearing carrier.
coach springing unit wheelset start.jpg


A completed bogie.
coach springing unit complete bogie.jpg


Close-up of a bearing carrier showing the spring in the slot.
coach springing unit spring slot.jpg


And that is all there is to it. Taking the wheelsets out is a simple matter of lifting the springs up (using the spring location tool) and the wheelset drops out.

Cheers,

Richard
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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Sat Feb 11, 2023 5:39 pm

Hi,

Courtesy of the drawing skills of Colin Craig here are a couple of diagrams showing the springing system:-

8ft 6in wb coach bogies.JPG


Cheers,

Richard
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Will L
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Re: Coach and DMU springing units for Mostyn

Postby Will L » Sat Feb 11, 2023 7:36 pm

Richard Oldfield wrote:Courtesy of the drawing skills of Colin Craig here are a couple of diagrams showing the springing system:-


Thanks for that Richard. None of the previous pic's of the etches showed the half etch side of the bearing carriers leaving me wondering exactly how they were intended to work. This makes it very clear. Looks like a well thought through approach. Of course, the proof is in the use, but it certainly looks as if it should be a good system. I'd be interest to know which if any faces you leave unpainted?

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zebedeesknees
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Re: Coach and DMU springing units for Mostyn

Postby zebedeesknees » Sun Feb 12, 2023 3:24 pm

Richard Oldfield wrote:Hi,

Courtesy of the drawing skills of Colin Craig here are a couple of diagrams showing the springing system:-

Hi Richard, thanks for the diagrams, I think I can follow the ideas there now.
There is no doubt that they will work, the mechanical design is indeed clever, but I do have a few reservations about the performance and some suggestions.

From here:- http://www.clag.org.uk/beam.html the design of the spring fulcrum makes it effectively a cantilever spring over each wheel with a length L (scaled from my monitor) of approximately 10mm. Experience and the maths suggest that this could be 'a bit stiff' with the chosen wire diameter. If too stiff, and 'no slop', then there could be a danger of derailments on abrupt changes of cant or a vertical misalignment of a rail joint on one side.

There does not appear to me to be any kind of stop to prevent the spring wire moving longitudinally, unless the idea is that the wire is intended to have a 90°bend at one end to locate in the notch of one of the bearing carriers. Not both ends of course! This could be prevented by filling the hook part of the bearing carriers with solder. Experience again, the wires will 'walk' if not restrained.

Chris Pendlenton was aware of the importance of secondary springing with his bogie design of decades ago, and an alternative was produced that is not integral with the bogie by Bill Bedford, both descibed here:- http://www.clag.org.uk/beam-annex5.html. If the Bedford etches are no longer available, it looks from the pictures that a version with similar dimensions could easily be fitted to the body floor using good ol' Markits handrail knobs.

The proof(s) will be in the running, and if I may suggest, an idea would be to make up a pair of bogies slightly differently to test as follows; do not fold down the fulcrums that are just inside the brakes, and make up a fulcrum in the centre of the bolster with a piece of tube or handrail knob such that the wire can pivot about it in much the same way as the Johnson locomotive bogie design. This is in effect an inverted version of the design discussed here:- http://www.clag.org.uk/beam-annex2.html. For this a slightly thicker wire may be preferred, depending on the weight of the vehicle.

I hope you find this helpful as intended and look forward to progress in whatever direction..

Ted.
(A purists' purist)

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Re: Coach and DMU springing units for Mostyn

Postby grovenor-2685 » Sun Feb 12, 2023 4:41 pm

zebedeesknees wrote:There does not appear to me to be any kind of stop to prevent the spring wire moving longitudinally,............................]This could be prevented by filling the hook part of the bearing carriers with solder.

It is pretty clear in this photo, https://www.scalefour.org/forum/download/file.php?id=33361&t=1 that the hook part is not half etched and thus provides a stop.
Regards
Keith
Grovenor Sidings

Richard Oldfield
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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Sun Feb 12, 2023 4:57 pm

Hi Will,

Will L wrote: I'd be interest to know which if any faces you leave unpainted?


Thanks for your kind comments about Colin's design.

I haven't really got round to thinking about painting them yet but, given that they come apart so easily, I dont envisage any issues (famous last words?!).

Cheers,

Richard

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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Sun Feb 12, 2023 5:43 pm

Hi Ted,

Thanks for your interest and suggestions :thumb , my comments are inserted below:-

zebedeesknees wrote:From here:- http://www.clag.org.uk/beam.html the design of the spring fulcrum makes it effectively a cantilever spring over each wheel with a length L (scaled from my monitor) of approximately 10mm. Experience and the maths suggest that this could be 'a bit stiff' with the chosen wire diameter. If too stiff, and 'no slop', then there could be a danger of derailments on abrupt changes of cant or a vertical misalignment of a rail joint on one side.

The spring wire diameter included in the 'kit' is only a suggestion and smaller diameters can easily be substituted. The coach springing units are going to be tested on (and intended for) Mostyn's well-laid trackwork, they are not trying to solve issues that we dont have.

zebedeesknees wrote:There does not appear to me to be any kind of stop to prevent the spring wire moving longitudinally, unless the idea is that the wire is intended to have a 90°bend at one end to locate in the notch of one of the bearing carriers. Not both ends of course! This could be prevented by filling the hook part of the bearing carriers with solder. Experience again, the wires will 'walk' if not restrained.

Keith has covered this in his posting - the spring wire cannot pass beyond the notch.

zebedeesknees wrote:Chris Pendlenton was aware of the importance of secondary springing with his bogie design of decades ago, and an alternative was produced that is not integral with the bogie by Bill Bedford, both descibed here:- http://www.clag.org.uk/beam-annex5.html. If the Bedford etches are no longer available, it looks from the pictures that a version with similar dimensions could easily be fitted to the body floor using good ol' Markits handrail knobs.

For the time being we are going for the simplest possible solution for our requirements. Based on experience gathered with our extensive fleet of 80 freightliner flats (which only have primary springing), we are cautiously optimistic .... but I will keep some humble pie to hand just in case!

zebedeesknees wrote:The proof(s) will be in the running, and if I may suggest, an idea would be to make up a pair of bogies slightly differently to test as follows; do not fold down the fulcrums that are just inside the brakes, and make up a fulcrum in the centre of the bolster with a piece of tube or handrail knob such that the wire can pivot about it in much the same way as the Johnson locomotive bogie design. This is in effect an inverted version of the design discussed here:- http://www.clag.org.uk/beam-annex2.html. For this a slightly thicker wire may be preferred, depending on the weight of the vehicle.

The top priority, for now, is to get some miles of testing done on Mostyn (which we have not even started yet). Will bear your suggestion in mind.

zebedeesknees wrote:I hope you find this helpful as intended and look forward to progress in whatever direction.

Your contribution is very much appreciated. :thumb

Cheers,
Richard

Crepello
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Re: Coach and DMU springing units for Mostyn

Postby Crepello » Sun Feb 12, 2023 10:41 pm

Hopefully the spring arrangement sketch was not pasted from the design drawings, as it suggests
the brakes only line up with the wheels when the bearings are bottomed in their slots?

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Re: Coach and DMU springing units for Mostyn

Postby davebradwell » Mon Feb 13, 2023 9:58 am

I had intended waiting to see how coach is mounted on bogies before commenting on this design but I see others have started.

First point is it will be a waste of time pulling a few coaches round the layout as an evaluation - re-wheeled Bachmanns would pass this test so it's a very low bar. The whole point of springing is to get superior track holding when propelling stock so you'll need about 10 coaches and push them over pointwork into sidings, preferably with Pullman gangways in contact and buffers retracted as this is what coaches must do, but perhaps not on Mostyn.

Is the top of your bogie strong enough? It's recorded that heavy coaches will splay out an MJT unit so will they not do the same with yours? The frame looks very flimsy and I'm wondering if with stiff springs it will just work like an MJT. Why not put a mark on outside of axleguards to indicate correct ride height? How do you plan to adjust this?

I feel you're missing a trick with the secondary springs - correctly implemented you can dump the primaries. Others miss a key part of the design of the Pendlenton bogie. We've all seen the coach with a wobbly wheel, given away by the body trembling about a horizontal centre of rotation about half way up the body. With short secondary springs on top and a high bogie pivot, there is still a danger of this occurring. The Pendlenton bogie, which I believe was developed within the West of Scotland group a decade or so before it appeared in MRJ, forces the body to sway about a point low down so it's like an inverted pendulum rather than an oscillating balance wheel and crucially, with long springs, any oscillation is much slower - a sway rather than a wobble and well damped. The centre spacer is a box section so prevents the frame twisting. Throw in steps with supports and Jackson coupling mounting and nothing has come close.

DaveB

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Will L
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Re: Coach and DMU springing units for Mostyn

Postby Will L » Mon Feb 13, 2023 4:47 pm

davebradwell wrote:...It's recorded that heavy coaches will splay out an MJT unit so will they not do the same with yours? The frame looks very flimsy and I'm wondering if with stiff springs it will just work like an MJT.

The tendency for the MJT bogie to splay was down to the fact that the two sides were not rigidly connected to each other. The lack of a rigid end bar across the bogie ends was always the reason I didn't like them. The Dick Petter's modification (avaible from Palatine Models) which got away from a dependence on a couple of solder joints at either end of a single torsion bar solved the problem under his coachs on Knutsford. And these were all brass and a good 200 grams a piece (i.e. significantly heavy).

I would expecte that the "angle iron" end crossmembers and the fold along the top edge of the sides in the bolster area was quite sufficient to keep the bogie frame rigid. Experience with sprung W irons, which contains very little metal, under heavy white metal wagons would suggest that the spreading effect from the pin point axles bearing combination would not be sufficient to flex the bogie side frames.

Edited to un-mangle (clarify) my last sentence which was written while also trying to supervise a couple of small grandchildren. Clearly doing two things at once is now beyond me
Last edited by Will L on Tue Feb 14, 2023 12:32 am, edited 1 time in total.

davebradwell
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Re: Coach and DMU springing units for Mostyn

Postby davebradwell » Mon Feb 13, 2023 8:23 pm

You're certainly right about the outward force on pin points being a weak area of design, Will. Exacto tried to avoid this by using parallel bearings but we seem to get away with the standard brg most of the time. Always worth bearing in mind, however.

DaveB

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Re: Coach and DMU springing units for Mostyn

Postby Chris Pendlenton » Tue Feb 14, 2023 7:52 pm

I have gone on about the importance of secondary suspensionfor coaching stock, particularly with touching gangways several times in MRJ (200) so won't repeat myself. They need to be long and low for the right dynamics. As Dave says, propelling a long rake of mated up gangwayed coaches through the road is the acid test unless your operations can avoid this sort of move.
The other point about splaying is well brought to attention. Applicable to wagons as well I found thin etched and folded brass w irons to be far less satisfactory in this regard to the original tinned steel Studiolith design which was stiff enough to avoid this issue. I am attracted to the Exactoscale plain journals but suppose there might be a rolling resistance penalty on long wagon trains. They have the additional advantage of being oblivious to varying pin point axle lengths and the effect they can have on axles running at slight random angles to the horizontal. They also need a lesser overall width which is useful for tender frames.

Chris

Richard Oldfield
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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Wed Feb 15, 2023 2:47 pm

Hi,

Crepello wrote:Hopefully the spring arrangement sketch was not pasted from the design drawings, as it suggests
the brakes only line up with the wheels when the bearings are bottomed in their slots?


I have just checked a number of the made-up bogies and can confirm that the brakes line up before the bearings are bottomed in their slots..

Cheers,

Richard

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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Wed Feb 15, 2023 3:58 pm

Hi Dave,
davebradwell wrote:First point is it will be a waste of time pulling a few coaches round the layout as an evaluation - re-wheeled Bachmanns would pass this test so it's a very low bar. The whole point of springing is to get superior track holding when propelling stock so you'll need about 10 coaches and push them over pointwork into sidings, preferably with Pullman gangways in contact and buffers retracted as this is what coaches must do, but perhaps not on Mostyn.

I cannot imagine where you dreamt up the idea that we might be testing just a few coaches as an evaluation. Why would we do that when our formations run to up to 15 hauled passenger vehicles, 10 DMU cars or up to 22 parcels vehicles? The whole point of springing has very little to do with propelling stock and is driven, especially in our case, by the need to demonstrate beautiful smooth running at a range of speeds. We do not need to propel hauled passenger stock in normal operation (although we always check it in testing) but you are overlooking Mostyn's bi-directional roads which have lengthy DMU formations which we expect to run reliably at line speed (75mph) in either direction including through complex pointwork in the fiddle yard.

New bogies awaiting their call to action.
coach springing units for testing.jpg

davebradwell wrote:Is the top of your bogie strong enough? It's recorded that heavy coaches will splay out an MJT unit so will they not do the same with yours? The frame looks very flimsy and I'm wondering if with stiff springs it will just work like an MJT. Why not put a mark on outside of axleguards to indicate correct ride height? How do you plan to adjust this?

I note your concern about the strength of the bogie but think your fears are groundless. We do not have heavy coaching stock - 140gm is occasionally achieved - personally I regard the addition of excessive weighting as a means of masking failure to construct the vehicle or trackwork correctly. The last thing we need is to be carting unneccessary weight around the country. Empty 60ft Freightliner flats run perfectly happily at line speed using this springing principle with weights of 70-75gm. Adjustment of ride height is simple = change the spring and/or alter the bogie mounting height.

davebradwell wrote:I feel you're missing a trick with the secondary springs - correctly implemented you can dump the primaries. Others miss a key part of the design of the Pendlenton bogie. We've all seen the coach with a wobbly wheel, given away by the body trembling about a horizontal centre of rotation about half way up the body. With short secondary springs on top and a high bogie pivot, there is still a danger of this occurring. The Pendlenton bogie, which I believe was developed within the West of Scotland group a decade or so before it appeared in MRJ, forces the body to sway about a point low down so it's like an inverted pendulum rather than an oscillating balance wheel and crucially, with long springs, any oscillation is much slower - a sway rather than a wobble and well damped. The centre spacer is a box section so prevents the frame twisting. Throw in steps with supports and Jackson coupling mounting and nothing has come close.

A much simpler solution for the problem you present, with this new springing unit design, would be to change the wheelset. The whole point of Colin's design is that it is relatively simple to build and very easy to maintain. We will no doubt learn some lessons as testing commences but it is very unlikely that overly-complicating the design will be a solution.


Cheers,
Richard
ps We may have overlooked the expanding market for heavy coaches being propelled in 10 coach rakes but we'll have to live with that regret. :)
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Re: Coach and DMU springing units for Mostyn

Postby davebradwell » Thu Feb 16, 2023 9:22 am

Apologies, Richard, as I hadn't made myself clear. My emphasis should have been on propelling - I'm no stranger to the problems encountered when running long trains at high speed but re-wheeled rtr will do this when pulling, given sensible couplings. The problems start when pushing them back into the siding if they have gangways and/or buffers touching as it is the contact between adjacent vehicles that is the cause of all ills as one coach tries to upset or lift it's neighbours. You haven't mentioned gangways which are part of a system including the coupling. I had assumed you have Mk 2, 3 or 4 coaches on Mostyn so still in the world of the Pullman gangway.

I agree completely about coach weight but if you're releasing them to a wider public then others won't. Kit coaches can be a problem and I think an MJT Gresley comes in at about 250gms! Those brought up on compensation seem unable to run anything under 200gms.

My wobbly wheel story was just to show that the resonant frequency of a standard coach body is within the range of frequencies we are using and how secondary springs can be arranged to shift this resonance out of our range. Gangways in contact can also be beneficial in getting the bodies to ride smoothly. I hadn't intended to suggest use of sub standard wheels.

I wish you every success with your testing but as our group have been here before it seemed decent to offer the results derived from 40 years of trying to get coaches to ride smoothly and keep them on the track under all conditions. If conditions are easier on Mostyn then you may well arrive at a simpler solution for home use.

DaveB

Richard Oldfield
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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Thu Feb 16, 2023 1:57 pm

Hi Dave,

Thanks for your reply and expansion of the issues. For my part, apologies, I omitted to answer your question about gangways and will now cover it.

Mostyn's passenger stock (both loco-hauled and DMU) plus appropriate parcels stock is fitted with expanding gangways of various designs and with retracted buffers where called for. We dont normally have a problem propelling these vehicles in full-length formations under test so I did not immediately grasp the challenge that you have faced. It may be coupling-related in as much as Mk1, Mk2 and Mk3 coaches have buckeye couplings in real life which we have represented through Kadee couplings. We also use Kadees at intermediate ends of DMU vehicles as there is limited fun in using screw couplings under gangways in exhibition conditions. These will cushion the effect of compression on the gangways/buffers and this might be why we have a simpler challenge than your own.

I would have to admit that the practice of 200gm plus vehicles is unknown to me but, if that was the design of the kit at the time, then fair enough. Mostyn has just under 300 bogie vehicles so any avoidance of added weight is a significant bonus and I work to the traditional 25gm per axle where possible.

I can be categoric that, as the new design stands, it cannot cope with very heavy vehicles for a simple reason - the etch is in 12thou brass which means that the width of the half-etched slot in the bearing carrier is 12 thou and this will not be stiff enough. There is a straightforward solution of etching the bearing carrier in thicker brass but that can wait for now.

The sharing of your experience is very much appreciated and our motivation for this thread is also to share our particular journey. Mostyn lives its life on the exhibition circuit so smooth stress-free operation is a minimum standard.

Cheers,
Richard

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Re: Coach and DMU springing units for Mostyn

Postby davebradwell » Sat Feb 18, 2023 10:24 am

It would seem that upgrading stock with body mounted couplngs, usually Kadees, is an international practice. The slack in Kadees does make keeping Pullman gangways in contact more difficult if the gangways are not to become the buffer when propelling. Our group don't have a common answer to this limitation and we have gone in different directions or ignored it. I have a couple of coaches with the scale Sergent couplings but this is hardly a useful test. Chris uses his own boxhead coupling with essentially zero slack and this would seem the ideal situation. I have never had a chance to see how the H0 rtr coaches manage the trick as they are advertised as having "diaphragms in contact".

Whether secondary springs are an extra complication depends largely on their design. We require a lowered centre spacer and this means an extra part which somehow morphed into 2 bits, possibly just to fit the fret. After that there's just the 2 spring wires which sit on the end cross members of the bogie and that's it. Trying to fit them to the body must produce a more complex solution. Latest setting procedure is to pull down the bolster onto the springs to improve damping so they only deal with body roll and this gives the added bonus that the coach height can be adjusted with the bogie retaining nut.

DaveB

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Re: Coach and DMU springing units for Mostyn

Postby Richard Oldfield » Sat Mar 04, 2023 3:22 pm

Hi folks,

Further postings on this topic will be delayed by our preparations for Macclesfield exhibition but I have remembered this old youtube video showing the same springing principle in use on freightliner flats - including a lengthy propelling move.

The running performance of primary springing only solutions cannot really be in doubt.



Enjoy!

Cheers,

Richard

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ChrisMitchell
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Re: Coach and DMU springing units for Mostyn

Postby ChrisMitchell » Sat Mar 04, 2023 5:35 pm

A scale 136mph!!!

Can’t really fault anything

Best regards, Chris

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Re: Coach and DMU springing units for Mostyn

Postby iak » Sat Mar 04, 2023 6:34 pm

Whooooosh! :shock:
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