Alternative Suspension on Six Wheelers – but will it work?

Lindsay G
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Alternative Suspension on Six Wheelers – but will it work?

Postby Lindsay G » Mon Sep 26, 2011 3:07 pm

I’m presently nearing completion of a rake of Drummond 6 wheel CR coaches. Bodies are complete and just cosmetics to add to the underside. However, this is where I’m seriously thinking about changing the suspension on 4 of them.

The kits came with a suspension system that didn’t take my fancy, so I purchased a single Brassmasters Cleminson chassis for appraisal. This went together beautifully and quickly, a well engineering bit of kit (no connection at all). Another 3 were fitted with Cleminson’s, 2 of which were picked up cheap at Scalefour North (but had incorrect w-iron profiles which had to be replaced) and a home made version butchered from the original kit pieces. All ran fine but the time and effort in having to adapt the latter 3 is not to be recommended!

I was a bit uneasy about all of the movement within the Cleminson and tried out a home-grown sprung arrangement. This employs Bill Bedford sprung W-irons on the outer wheelers, and the centre W-iron suspended from a length of guitar wire, with fulcrums on droppers within the outer W-irons. The wire is only soldered in place at one end to allow maximum side-to-side and up-and-down movement. End-to-end movement is avoided by entrapping the W-iron within a U shaped bracket (same effect as the Cleminson arrangement). Some lead was added within the centre W-iron to help keep it in contact with the track. Ride height worked out fine first go. An image taken at an early part of construction is below :

6 wheelers.JPG

Experience to date? The sprung coach has ran as smoothly as the Cleminsons – if anything there was body wobble with some Cleminsons (maybe my setting up!). They’ve now ran over 3 different layouts with no derailments experienced (more than can be said for simpler 4 wheel stock being tested at the same time!). One of the layouts has curves well below the P4 recommended limit but this caused no derailment problems. Probably as you’d expect, I did notice that free running was compromised the tighter track was curved, but only on really tight radii which the coaches will not encounter unless guesting elsewhere.

When it now comes to adding the cosmetics, the sprung version would seem to have a number of advantages. The outer
W-irons will pose no problems for the addition of springs and axles (the centre springs and axleboxes I envisage being attached to the W-iron, with the J-hangers on the solebar). Plenty room is left elsewhere under the chassis for all the detail and weight to be added. Tie bars can also be added without worry (not attached to the centre W-iron). Maintenance should be minimal, if that.

With the Cleminsons there are problems. I can envisage springs attached to solebars getting caught up with axleboxes attached to the W-irons or else gaping spaces created between the 2. If everything is attached to the axleboxes, sweep of swing will be reduced as might other directional movement. Etched springs have been suggested and might overcome or reduce these problems but they will lack depth. Room to add other detail such as brake gear and gas tanks also gets compromised. Of course this may not happen with other coach designs and Cleminsons, perhaps these Caley designs add complications.

Whatever, experience to date suggests that the sprung version works, and that completing the cosmetics will not cause problems and can be effected very simply. So, I am now thinking of dumping the Cleminsons and springing all coaches.

Whilst the idea is home-grown, I can’t see that it is that radical or innovative never to have been tried elsewhere – perhaps quite the reverse. So, before I take the plunge, has anyone out there tried this method? If so, what was the outcome? Are there complications which should be avoided?

Lindsay
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David Knight
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Re: Alternative Suspension on Six Wheelers – but will it wor

Postby David Knight » Mon Sep 26, 2011 3:57 pm

Thanks Lindsay, I have a couple of 6 wheelers awaiting a round tuit and I had been considering what to do with the suspension. I also have the Cleminson and Bill B mix and had considered doing my sprung version using the Bedford spring with an Exactoscale 1mm axle and a 2mm OD sleeve to allow for sideplay in the middle. Now I have another approach to think about :-? Fortunately the coaches are not needed in the near future :D

Cheers,

David

Mark Tatlow
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Re: Alternative Suspension on Six Wheelers – but will it wor

Postby Mark Tatlow » Mon Sep 26, 2011 9:53 pm

Your solution is quite similar to that which has been used in the former Microrail kits for some time (and no doubt others, sorry if I do not know them). The previous method was to use a fixed axle at one end and a rocking iron at the other, with the middle one floating.

It certainly did work, as I am sure yours will.

There are a couple of theoretical difficulties with your solution though. Firstly, all of the play has to be taken up in the centre axle with your solution. In the Clemenson, it is shared between the middle axle, which moves one way, and the outer axles that move the other. Secondly, as the axles do an arc in their movement, the wheel stays in line with the rail as it follows the curve.

Your solution will make some of the attachment of springs easier, as your outer wheels will not need to move much. It will be more difficult to the inner though as the movement will be exaggerated.

I suggest that you experiment to see what works for you, as I am sure both can work successfully.
Mark Tatlow

allanferguson
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Re: Alternative Suspension on Six Wheelers – but will it wor

Postby allanferguson » Mon Sep 26, 2011 10:32 pm

Lindsay, glad to see you're getting on with these coaches. You may recall that I made a contribution a while ago in which I suggested that the cleminson type arrangement was the most useful, and possibly the only, effective arrangement for our purposes, based originally on a minimum radius of 1000mm on our Bonnybridge layout. I found that (a) the sideways displacement of the centre axle needed to be about 1mm each side minimum and (b) if the end axles were not radial to the curve they had a strong tendency to climb over the rail. I have a number of 6 wheelers based on the Brassmasters cleminson system, or a home brewed equivelant, which run fine round these curves. However now I would prefer a sprung arrangement, but I still think it needs a cleminson type of arrangement to allow sideways movement of all three axles, and to ensure that the outer axles are as nearly as possible radial to the curve. I envisage using BB springing units on three axles, but I haven't worked out the practicalities of putting it all together.

My concern about your arrangement is the fixed outer axles which mean that you have effectively a very long wheelbase four wheeler. I do appreciate that you may be catering for larger radii of curvature on you own layout, and will await with interest practical tests!

Regards, Allan F

Chris Mitton
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Joined: Sun Aug 31, 2008 1:18 pm

Re: Alternative Suspension on Six Wheelers – but will it wor

Postby Chris Mitton » Mon Sep 26, 2011 11:56 pm

Coincidentally, I've nearly finished an ex-GNR six wheel luggage brake from a D&S kit. I still need to paint / letter / varnish the body, detail the roof and devise a way of fixing it on, and add some pipework - maybe I'll post a piccy when it's done.

The suspension, built more or less as Danny Pinnock designed it, looks tolerably similar in principle to yours, and to what Mark describes - one end fixed, one end rocking, the middle one floating, with inside bearings, the middle springs and W-irons being dummies attached to the solebars. As Mark says, all the side play is on the middle axle, but that objection is for me largely theoretical. My coach did get pushed (no couplings yet!) by one of Jim Smith-Wright's diesels (heresy!) for several laps of the West Midlands AG track without problem, except when it ran away on an almost imperceptible gradient! It can also negotiate all the pointwork on my layout that I've got round to building, a succession of B7 slips and tandems, without falling off or climbing the rails. However, it did take a bit of tweaking to get there - the middle axle has not much more than its own weight holding it on the track so maybe I'll try weighting it with some lead if I can cram any in. The coach currently weighs around 75 grams, which sounds about right until you remember the middle wheels don't carry any weight. Altogether though I'm quite happy with the solution.

I have got one puzzle about this coach. The only pictures I've found have it marshalled in a train so I can't see the end detail. My drawing only shows one hose connection, presumably for the vacuum brake - none for the steam heating, so if it were marshalled in the middle of a train any passengers behind would freeze! There is no sign of a stove outlet on the roof, so how did the poor guard keep warm? or didn't he? Or should it have steam heating pipes?

Regards
Chris

williambarter
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Re: Alternative Suspension on Six Wheelers – but will it wor

Postby williambarter » Tue Sep 27, 2011 8:07 am

I've tried out an arrangement for my own etched SER 6-wheelers that looks a bit similar to yours, except that the outer axles pivot to conform at least partially to the curve. It was suggested to me by a friend, and I am not sure where he got it from, so there are no claims to originality in this.

One outer axle fitting is designed with two ears that bear against the underside of the underframe pan, and a 10BA bolt as a centrepin - this can therefore pivot (yaw) but not roll, and so keeps the relationship between coach and axle. It could in theory pitch, but is restrained by the longitudinal wire

The other is mounted simply on a Romford wheel nut on the centrepin - this being of small diametr and slightly rounded off at the edges allows the axle to move in all three planes (although pitch is again restrained by the wire.

The centre axle floats on the wire, and can move from side to side with the curve. It is kept in its correct longitudinal location by a pir of 10BA bolts in the underframe, working with slots in the axle-carrier.

It works OK on a test track including A5 turnouts. The ride seems steady as in terms of carrying the weight it is a long-wheelbase 4-wheeler, but the tendency to get flange-climbing on curves is if not eliminated very much reduced.

William Barter

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Will L
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Re: Alternative Suspension on Six Wheelers – but will it wor

Postby Will L » Tue Sep 27, 2011 9:31 am

Chris Mitton wrote:Coincidentally, I've nearly finished an ex-GNR six wheel luggage brake from a D&S kit. ...The suspension, built more or less as Danny Pinnock designed it, looks tolerably similar in principle to yours, and to what Mark describes - one end fixed, one end rocking, the middle one floating, with inside bearings, the middle springs and W-irons being dummies attached to the solebars. As Mark says, all the side play is on the middle axle, but that objection is for me largely theoretical. My coach did get pushed (no couplings yet!) by one of Jim Smith-Wright's diesels (heresy!) for several laps of the West Midlands AG track without problem, except when it ran away on an almost imperceptible gradient! It can also negotiate all the pointwork on my layout that I've got round to building, a succession of B7 slips and tandems, without falling off or climbing the rails. However, it did take a bit of tweaking to get there - the middle axle has not much more than its own weight holding it on the track so maybe I'll try weighting it with some lead if I can cram any in.


The two GNR/LNER 6 wheelers that were in the Chairman's cup cabinet are of this ilk. The centre axles carry a reasonable slug of their own weight. They have both done a lot of exhibition running before moving up a class and getting P4 wheels. In the narrower gauge they were good reliable runners doing 2'6" curves no trouble, so I think the concept works. They don't suit the current layout so they don't get run and the jury is out on their running qualities in P4. The little running they have done suggests that I will have to do more than just drop in p4 wheels, but I doubt if this is insurmountable given their previous good character.

How I'd build them now given I'd want to spring them, that is an interesting question. I've still got one to do...

Will

Lindsay G
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Joined: Thu Aug 07, 2008 2:16 am

Re: Alternative Suspension on Six Wheelers – but will it wor

Postby Lindsay G » Tue Sep 27, 2011 4:57 pm

Chris Mitton wrote:Coincidentally, I've nearly finished an ex-GNR six wheel luggage brake from a D&S kit. I still need to paint / letter / varnish the body, detail the roof and devise a way of fixing it on, and add some pipework - maybe I'll post a piccy when it's done.



Here’s my method of attaching roofs to the 6 wheelers :

IMG_1619.JPG


The bar along the roof is just spare fret brass folded into a U to stop the roof sagging when the screws are tightened. 2 nuts are soldered within the U. The strips between the compartments are also bent into a U for rigidity to ensure a nice tight fit. The screws are tightened via a drilled hole in the floor of the body which isn’t noticeable at all – a bit of a fiddle to fit but the roofs shouldn’t be on and off once completed!

Lindsay
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Chris Mitton
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Re: Alternative Suspension on Six Wheelers – but will it wor

Postby Chris Mitton » Wed Sep 28, 2011 10:08 pm

Hi Lindsay, thanks for the pic....

Slightly off-topic (the other end of the coach from the title of this thread!)...I can't do this with a styrene roof with some quite sharp curves, and as it fits quite well I don't see any point in trying to make another from brass - anyway the damned thing is heavy enough already! I'm toying with the idea of some shallow brass channel joining the top flanges of the sides, with a captive bolt pointing upwards onto which the oil lamp tops can screw down to hold the roof on (with a tube spacer to stop distortion) - but with some trepidation as to whether my skill level can do that sufficiently accurately. Drilling and tapping these tiny castings 12 BA promises to be fun, also involving some wallet damage as my smallest tap is 10BA - a virtual visit to Eileen beckons!

Regards
Chris

Michael Waldron
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Joined: Tue Jan 30, 2018 11:01 am

Re: Alternative Suspension on Six Wheelers – but will it work?

Postby Michael Waldron » Fri Jul 01, 2022 6:22 am

It’s a long time since this thread was initiated, but no one has mentioned anything about Branchlines carriages - which most of my LBSCR Billinton carriages are. They use the four wheel rocker-at-one-end rigid arrangement with floating centre axle, as described above (or similar). I don’t like the idea in model form either.

Roxey do a simplified version of a Cleminson truck for their Stroudley 6 wheelers, but they’re mounted on the older design of rocker strip with twist tag restrained W irons on the the top, which is sloppy, and, while I like the idea, I don’t care for the slop.

Brassmasters kit is excellently manufactured, but very complex with all the calculation and mounting decisions to make relating to wheelbase dimensions. Also the centre axle attachment parts can show viewing the carriage from the side.

I tried asking why all the maths, but didn’t get an answer, as I was told they didn’t understand the question.

Can anyone enlighten me as as to why all these decisions have to be made? I’m no mathematical genius!!

Mike

davebradwell
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Re: Alternative Suspension on Six Wheelers – but will it work?

Postby davebradwell » Fri Jul 01, 2022 8:05 am

I think compensation sank itself with its own sums. I've never seen a Branchlines coach but why not just spring the things? No sums required, just slot the bearing holes 1/2mm up and down in the axleguards and arrange a wire leaf spring. Make the centre one a bit longer and fit a Tatlow axle for the slide. Simpler, cheaper, quieter.

DaveB


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