Cleminson 6 wheelers

Ken Tonge

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My 4-wheel coaches have a tendency to derail. I guess it is the length of wheelbase since short wheelbase wagons and bogie stock are OK. My plan is to convert the coaches to 6-wheelers with a Clemison type of chassis. Reading forums suggests that this might not guarantee success. I just wonder how important easement is on the tracks. I don't want to do all the work on the coaches and then find out that it is actually the track that is the problem. Anybody know about these things?
 

JimmyB

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Often track is the issue, most stock rolls over, but one item fails and derails, and though it would seem that the rolling stock is the issue, it may just be that that particular item is prone to failure due it its position in the consist, and poor track.
 
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DafyddElvy

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In 1:1 scale or our models, derailments rarely happen for a single reason, it normally takes two to three to cause a derailment.

First consideration before looking a a cleminson system might be to think about the length of the vehicle v the curve radius, if the radius is too tight the centre truck may need to slide out with the side of the vehicle to tackle your tightest curve.

I know I am going off topic from your question but, do the coaches always derail at the same location, is it always the same vehicle that derails etc etc..........

Back on topic, what is the make up of the coach floor, what is your tightest radius, and do your coaches have footboards, all of these things can influence the the best build of a cleminson system for your coaches. I have some six wheel coaches with the centre axle boxes fixed to the underframe, I also have two wagons where the axle boxes are fixed to the trucks.

Can you share a couple of photos and some dimensions.

David
 

JimmyB

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In 1:1 scale or our models, derailments rarely happen for a single reason, it normally takes two to three to cause a derailment.

First consideration before looking a a cleminson system might be to think about the length of the vehicle v the curve radius, if the radius is too tight the centre truck may need to slide out with the side of the vehicle to tackle your tightest curve.

I know I am going off topic from your question but, do the coaches always derail at the same location, is it always the same vehicle that derails etc etc..........

Back on topic, what is the make up of the coach floor, what is your tightest radius, and do your coaches have footboards, all of these things can influence the the best build of a cleminson system for your coaches. I have some six wheel coaches with the centre axle boxes fixed to the underframe, I also have two wagons where the axle boxes are fixed to the trucks.

Can you share a couple of photos and some dimensions.

David
David agree with all the above points, but another factor to add it weight, especially if it is in the middle of a rake.
 

DafyddElvy

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David agree with all the above points, but another factor to add it weight, especially if it is in the middle of a rake.
Jimmy,

You are correct sorry, I made an assumption regarding the weight and we know what an assumption can lead to, yes fitting a light vehicle with a cleminson system can actually make things worse.

Isn't modelling fun :)

David
 

dunnyrail

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All sound advice above particularly the assessment of what and where. I would suggest first up check the squareness of the vehicle, IE when you put it on a flat surface are all the wheels touching it? A big lump of flat glass is good for this but generally kitchen worktop should be pretty flat as well. If not then that could be your problem, slowly run the vehicle over the trouble spot if you can identify it, look with your eyes at track level to see what occures and you may well see your issue.
 

PhilP

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Perhaps we should ask the make, and model, of the stock in question?

How long is the train?

Where in the formation is the troublesome truck?
 

ge_rik

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I've been spending a fair bit of time recently experimenting with Cleminson six wheelers and come to the conclusion that a successful six wheeled coach or wagon is mainly down to the design of the chassis but also is dependent to a slightly lesser extent on the the quality of trackwork.

In effect, a Cleminson chassis is effectively a long four wheeler with a floating two wheel truck in the middle. The advantage of the middle truck is that, through the linkages, it swings the outer two wheel trucks to the correct angle when negotiating curves. I doubt that just adding a middle truck will solve your problems and might actually create more. What might help is adding compensation to one of the outer trucks.

If your can mount the axles for your coaches in two wheel trucks, the you could try adding a fulcrum (eg a strip of 1mm or 1.5mm thick plasticard) along the centreline of one truck and fixing it in place with a couple of self tappers also along the centreline so the truck can rock from side to side.You'll also need to raise the other truck by the same amount and fix it laterally so it can't wobble.

I hope that makes sense.

I've not yet blogged my experiments and builds of my Cleminson coaches and wagon builds but aim to get around to it shortly. In the meantime here's a blog post and and a video which touch upon what I've covered above.



Rik
 

dunnyrail

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Indeed as Rik has just said, compensation is a ‘get out of jail card’ for both dodgy track and vehicles. But first we do need to know what and the results of any investigations as suggested.
 

trammayo

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On tramways, it was not uncommon to widen the track gauge on curves - Leeds had particular problems with its' EMB Pivotal truck equipped cars. When worn, the single axle, coss-linked, trucks would not return to the correct position. Eventually, the trucks were locked in placed and the city became the operator of the longest rigid wheelbase two-axle trams in the country! Mind you, if you widened the curves, something else might drop in!
 

Brixham

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It may prove fruitful to examine the cleminson arrangement on a Piko 6 wheel coach. It tracks nicely through curves of varying radii and pointwork. There seems to be just enough play to cope with uneven track.

For long wheelbase 2 axle cars there is an aftermarket solution to cross couple the two axle pivots to enable better steering through curves. It’s here somewhere in gsc!

Malcolm
 

Ken Tonge

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Jimmy,

You are correct sorry, I made an assumption regarding the weight and we know what an assumption can lead to, yes fitting a light vehicle with a cleminson system can actually make things worse.

Isn't modelling fun :)

David
Thanks to all for comments. The details are that the vehicles are about 12" long over buffers and have 6" wheelbase (4 wheelers). The track radius is 3 to 4 feet on the curves and I have put something of an easement on all of them - but perhaps not enough. There ARE wobbly bits but every thing copes except the 4-wheeler coaches. I did add lead weights under the bodies but this did not help very much (brought the weight of each coach up to about 1kg). Derailing is unpredictable in terms of where (but always on a curve) and which vehicle in a train does it. I put bogies on one coach and the problem is solved but it makes coach look a bit "toy-like". From the comments above I guess I should make an experimental chassis on which to try out the suggestions for pivots and compensation before attacking the coaches themselves. Will post the results after the experiments are completed .
Thank you all.
 

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JimmyB

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I have found curve to be the worse area for derailment, especially if the wagon does not have compensation. If hand push the wagon around the curve, check to see if all 4 wheels remain in contact with the rail, a bit of hand "wobbling" as you push it around, you may find a spot where the flange just clears the top of the rail, and this is you issue. The wheel base, axle compensation, flange size and position in the rake will all help determine if a wagon derails.
 
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Rhinochugger

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Bogeys every time for me :nod::nod::nod::nod:
 

meiningen8

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I have several Magnus 6 wheel trucks and have found that the centre axle not only needs to smoothly move from side to side but also have some vertical movement to cope with uneven track hope this helps
 

ge_rik

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I have found curve to be the worse area for derailment, especially if the wagon does not have compensation. If hand push the wagon around the curve, check to see if all 4 wheels remain in contact with the rail, a bit of hand "wobbling" as you push it around, you may find a spot where the flange just clears the top of the rail, and this is you issue. The wheel base, axle compensation, flange size and position in the rake will all help determine if a wagon derails.
I was about to say the same thing. I found lying on the ground watching the wheels closely as they negotiated the offending curves to be very informative. What tends to happen with long wheelbase four wheelers is two diagonally opposite wheels act as fulcrums allowing the other two to rock. If the size of the rocking is greater than the depth of the flanges then off she comes ..... The rocking will also happen at places on straights but the coaches will stay on the tracks as there's no sideways force. Adding simple compensation makes a world of difference.

Rik
 

Northsider

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Having the inner/outer rail of a curve higher or lower will always cause problems; other posts have already described how to feel for 'rock', when one wheel may skip over the rail. Packing sleepers to avoid this should mean four-wheelers negotiate curves successfully.

To revert to the original idea, Cleminson six-wheelers need enough room for the centre truck to 'throw' side-to-side and a degree of vertical movement to accommodate high/low spots on the permanent way; getting this right takes quite a bit of trial-and-error testing. An easier solution might be to follow the Isle of Man Railway's principle, and mount two four-wheeled coach bodies on a bogie chassis...
 

ge_rik

British narrow gauge (esp. Southwold and W&LLR)
24 Oct 2009
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Having the inner/outer rail of a curve higher or lower will always cause problems; other posts have already described how to feel for 'rock', when one wheel may skip over the rail. Packing sleepers to avoid this should mean four-wheelers negotiate curves successfully.

To revert to the original idea, Cleminson six-wheelers need enough room for the centre truck to 'throw' side-to-side and a degree of vertical movement to accommodate high/low spots on the permanent way; getting this right takes quite a bit of trial-and-error testing. An easier solution might be to follow the Isle of Man Railway's principle, and mount two four-wheeled coach bodies on a bogie chassis...
When I was experimenting with my Cleminsons, I spent ages figuring out how to give the centre truck support when swinging out round the tight curves on my railway. At last. I thought I'd cracked it! But then I realised it was equally important to ensure the centre truck had enough room to float up and down to stay on the track when coping with my undulations, particularly with the long wheelbase of the coaches which needed the centre truck able to rise and fall by over 10mm!

I figured it out in the end but it took several iterations of the design to get there.

Rik
 

DafyddElvy

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On my 7mm scale models I think I have used 2 different 6 wheel chassis systems, I'll try and remember to get down to the workshop over the weekend and photograph them.
Both systems are very different but work equally well.
One use just a simple rod between the outer and inner trucks bent slight to give some downward pressure the other just relies on the weight of the centre truck to hold it down on to the rails.

What I did find with both systems is that it's good to give the centre truck plenty of slop when not on the rails, once adjusted they run perfectly happily over rough track and curves down to 1.2m, limited only by the step boards.

David