Gibson LMS 2P 4-4-0

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zebedeesknees
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Re: Gibson LMS 2P 4-4-0

Postby zebedeesknees » Wed Aug 25, 2021 10:24 pm

davebradwell wrote: If I jacked up the springs on the leading axle of the 4-4-0 to pinch some weight from the bogie (and the trailing axle) I would expect it to pull more and I've done it on a 4-6-0 which was reluctant to pull the required 10 coaches up a 1 in 100 so a little weight transfer from the bogie was required.
DaveB


Unless the bogie was taking some of the weight that should have been on the leading axle? It would be a great help if the relative weights carried by the bogie and each axle were measured.

I made a simple axle weighing jig and wrote it up somewhere, I thought it was on the CLAG site, but can't find it now.

Ted.
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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Thu Aug 26, 2021 10:41 am

davebradwell wrote:...I doubt if you could measure the effect uneven weight distribution has on haulage, Will. Apparently it does make a difference on the prototype, where once the first wheel slips there's enough inertia to knock the legs from under the others but I've never noticed it in 4mm scale where the greatest haulage is generated by turning the controller to full and spinning the wheels... (quoted out of order) Perhaps there just isn't enough weight in our models for them to behave like the full size.

Not convinced. The adhesion available from our chassis derives from the coefficient of friction between wheel and rail. The calculation is based on a linear equation so the implications are not affected by scaling and won’t differ between model and prototype. The static version of the coefficient of friction, which applies when the wheels aren't slipping, is significantly higher than the kinetic variety that applies when they are (0.6 as against 0.4), and it is this fact that leads to a slipping chassis having less adhesion, see this post to have it spelled out in detail.

...If I jacked up the springs on the leading axle of the 4-4-0 to pinch some weight from the bogie (and the trailing axle) I would expect it to pull more and I've done it on a 4-6-0 which was reluctant to pull the required 10 coaches up a 1 in 100 so a little weight transfer from the bogie was required.

Given the very real difficulties there are in judging exactly what the spring rate is for a individually adjusted spring, I don't see how you can know what the weight distribution actually was before or after such an adjustment. Clearly you achieved an improvement, but I don't think you can claim to know why it worked. The advantage of CSBs being that you do have some control of what the weight distribution actually is, and that is exactly why I prefer them to individually adjusted springs. We may need to agree to differ on this one until such time as we have available to us an accurate single axle weigh bridge that works in 4mm scale. This being a very tricky problem to solve as the late lamented Don Rowland demonstrated.
Don't the world's freight locos now use a 3rd type of friction when the wheel is just starting to slip in order to get massive loads under way?

My understanding, and I could be wrong, is that what modern locos do is to monitor each wheel/axle individually for slip and reduce the power to that axle so it stops slipping. That way they deliver the maximum available adhesion and take fully into account not just the weight on a particular axle but also the condition of the track under each wheel.

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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Thu Aug 26, 2021 2:46 pm

I wrote:The static version of the coefficient of friction, which applies when the wheels aren't slipping, is significantly higher than the kinetic variety that applies when they are (0.6 as against 0.4), and it is this fact that leads to a slipping chassis having less adhesion

Just think through the implications of that. What it means is a loco that can pulls 10 coaches up a 1 in 100 with all its wheels spinning, could pull 50% more without wheel slip it you can balance the loco to get equal weight on all wheels and hence the maximum adhesion. While I will accept that real world conditions may mean that the difference wont really be quite that big, but perhaps you can see why CSB users need not be too concerned about not being able to randomly pile weight anywhere on the loco. To take wisdom from a rather different world, it not the size that maters it what you do with it.

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Julian Roberts
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Re: Gibson LMS 2P 4-4-0

Postby Julian Roberts » Thu Aug 26, 2021 2:51 pm

Will L wrote:
Don't the world's freight locos now use a 3rd type of friction when the wheel is just starting to slip in order to get massive loads under way?

My understanding, and I could be wrong, is that what modern locos do is to monitor each wheel/axle individually for slip and reduce the power to that axle so it stops slipping. That way they deliver the maximum available adhesion and take fully into account not just the weight on a particular axle but also the condition of the track under each wheel.


My limited amateur understanding gleaned from Modern Railways over the years, is that wheelslip is electronically controlled and generally prevented. However in the case of such classes as the 60, 90 and 91 "creep control" provides a controlled wheelslip increasing haulage power. IIRC Roger Ford said it was possible to hear when it was in operation, a high pitch not unlike flange squeal. Pretty sure I could discern it on pre-Hitachi southbound ECML trains after the stop at Grantham if I went and stood at the back right next to the locomotive, and on northbound WCML trains after the stop at Oxenholme in pre-Pendolino times.

May I suggest a 4-4-0 haulage competition at a future Scaleforum to prove or disprove these erudite cogitations? :)

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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Thu Aug 26, 2021 4:03 pm

Julian Roberts wrote:... However in the case of such classes as the 60 and 91 "creep control" provides a controlled wheelslip increasing haulage power. IIRC Roger Ford said it was possible to hear when it was in operation, a high pitch not unlike flange squeal.

Now you've got me interested. You can try reading this Wikipedia article title Adhesion railway. This does say that when maximum adhesion is achieved, the wheel is actulay turning slightly faster than the loco is moving, the difference being taken up by molecular distortions in the contact point between wheel and rail. This is called "slip" but I don't think this is the same things as the uncontrolled and obvious excess rotation we would visually recognise as slip. Nor do I think it invalidates the idea of the static Coefficient of Friction being greater than the kinetic one, it just describes the mechanism which operates just before uncontrolled slipping set in. The "creep control" effect is achieved, as I suggested, by very carefully control of the amount of power being transmitted through each wheel set, it is done at at high frequency and as a result produces a distinctive whining noise. I don't think it equates to turning up your controller and letting the wheels whizz round. That said, modern model train controller circuits, which are actually controlling how fast the armature spins by varying the voltage seen by the motor, are playing the same game.
May I suggest a 4-4-0 haulage competition at a future Scaleforum to prove or disprove these erudite cogitations? :)

I too feel it is a shame we gave up on the Deputy Chairman's Cup, but I think it did tend to get too technical, probably driven by people like me, and as I said before Don was unable to find a way of accurately measuring the weight per axle which he needed to make sense of some of the results.

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Paul Willis
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Re: Gibson LMS 2P 4-4-0

Postby Paul Willis » Thu Aug 26, 2021 4:26 pm

Will L wrote:
Julian Roberts wrote:May I suggest a 4-4-0 haulage competition at a future Scaleforum to prove or disprove these erudite cogitations? :)

I too feel it is a shame we gave up on the Deputy Chairman's Cup, but I think it did tend to get too technical, probably driven by people like me, and as I said before Don was unable to find a way of accurately measuring the weight per axle which he needed to make sense of some of the results.

It's possibly the 18.83 equivalent of an Old Wives' Tale, but I am sure that I have been told that the Deputy Chairman's Cup folded after an RTR diesel with drop-in wheelsets performed far better than any of the etched brass confections with carefully calibrated axle loadings...

Possibly apocryphal - I was a member of the Society at the time, but not paying close interest.

The BS4 group this afternoon had a lively discussion in the park, where the idea of theoretically calculating the bearing spring rates for wagon kits was loudly shouted down in favour of trial and error :-) There were also chocolate biscuits though!

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Re: Gibson LMS 2P 4-4-0

Postby Enigma » Thu Aug 26, 2021 4:37 pm

I also remember that one year a plastic bodied Cl 37 with a scratch built chassis (made, I think, of brass strip and sections) and no weight at all won all the tests including the haulage.

I'm sure I have the 'result sheet' tucked away somewhere.

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Re: Gibson LMS 2P 4-4-0

Postby davebradwell » Thu Aug 26, 2021 5:19 pm

It's a very simple thing to test - take loco chassis, preferably with no carrying wheels, fix weight over centre and determine how many wagons it can pull. Move weight towards one end and repeat. This removes all other variables.

Must say that I've driven steam engines down to 2 1/2" gauge and they all exhibited the prototype behaviour where once it slips you lose traction and might come to a halt. 4mm scale locos don't seem to do this and if cautious application of power doesn't move the train then spinning the wheels gives the best chance. It's probably something to do with the boundary conditions and I recall the steamers would lose the difference between static and dynamic friction if the track was greasy.

Will add that I've never calculated weight distribution, optimum centre of gravity, beam fulcrum positions or any of this. I just build the model, which usually involves drawing and etching, gradually add weight and tweak springs to achieve 2 things: it must stay on the track and pull the required train.

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Julian Roberts
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Re: Gibson LMS 2P 4-4-0

Postby Julian Roberts » Thu Aug 26, 2021 6:00 pm

Will L wrote: This is called "slip" but I don't think this is the same things as the uncontrolled and obvious excess rotation we would visually recognise as slip. Nor do I think it invalidates the idea of the static Coefficient of Friction being greater than the kinetic one, it just describes the mechanism which operates just before uncontrolled slipping set in. The "creep control" effect is achieved, as I suggested, by very carefully control of the amount of power being transmitted through each wheel set, it is done at at high frequency and as a result produces a distinctive whining noise. I don't think it equates to turning up your controller and letting the wheels whizz round.


Yes it was definitely along those lines, the wheel slipping very slightly. Obviously on a modern diesel electric or electric loco each wheelset can be separately controlled by the electronics, not like steam. I think the sound was the wheel on the rail, not electronic - but obviously I'm just an amateur, probably wrong.

Why not have a session of purely 4-4-0 haulage capability (or 0-4-4) - a fixed rake of coaches, see what hauls best? - not mixing it up with the generality of wheel arrangements - as it is always this wheel arrangement that provokes so much interest.

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Re: Gibson LMS 2P 4-4-0

Postby Philip Hall » Fri Aug 27, 2021 7:14 pm

Not withstanding the arguments about the merits or otherwise of suspension of whatever form, I once converted a Hornby T9 to EM with Ultrascale wheels. It wouldn’t pull much to start with, despite having modified the tender to bear a fair amount of weight on the rear of the engine. A bit of investigation revealed that Hornby had increased the stiffness of the spring over the front bogie since the last one of these I had done, and winding a new softer spring left the driving wheels more in contact with the track. I just lifted each driving wheelset in turn to see how ‘heavy’ it felt, as is my usual practice, after this adjustment I had it whirling nine or ten heavy kit built cartridges around a testing EM circuit, and on the straight it would have taken more.

The T9 is not known for being a heavy engine, despite the die cast boiler and smokebox, so I was quite pleased and so was the engine’s eventual owner.

Philip

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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Sat Aug 28, 2021 11:31 am

Philip Hall wrote:Not withstanding the arguments about the merits or otherwise of suspension of whatever form, I once converted a Hornby T9 to EM with Ultrascale wheels. It wouldn’t pull much to start with, despite having modified the tender to bear a fair amount of weight on the rear of the engine. A bit of investigation revealed that Hornby had increased the stiffness of the spring over the front bogie since the last one of these I had done, and winding a new softer spring left the driving wheels more in contact with the track. I just lifted each driving wheelset in turn to see how ‘heavy’ it felt, as is my usual practice, after this adjustment I had it whirling nine or ten heavy kit built cartridges around a testing EM circuit, and on the straight it would have taken more.

The T9 is not known for being a heavy engine, despite the die cast boiler and smokebox, so I was quite pleased and so was the engine’s eventual owner.

Quite, demonstrates that getting the loco balance right has a significant effect on how much it will pull, and hence how not taking it into account can result in very disappointing performance. What I don't understand why people prefer to guess and hope rather than take the trouble to try and understand what is going on. Anybody for an social media anti-sus(pension) campaign?

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zebedeesknees
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Re: Gibson LMS 2P 4-4-0

Postby zebedeesknees » Sat Aug 28, 2021 11:56 am

Will L wrote: What I don't understand why people prefer to guess and hope rather than take the trouble to try and understand what is going on.

Some of those that do understand have an agenda...
Anybody for an social media anti-sus(pension) campaign?

That's been running for decades Will, certainly since before the inception of this forum!

Ted.
(A purists' purist)

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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Sat Aug 28, 2021 12:31 pm

zebedeesknees wrote:
Will L wrote: What I don't understand why people prefer to guess and hope rather than take the trouble to try and understand what is going on.

Some of those that do understand have an agenda...
Anybody for an social media anti-sus(pension) campaign?

That's been running for decades Will, certainly since before the inception of this forum!


That's what we need a good bit of conspiracy theory. I was on E4um too remember

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Re: Gibson LMS 2P 4-4-0

Postby Tony W » Fri Oct 01, 2021 3:39 pm

As an advocate of springing for many years, and not wishing to enter the debate on this topic, I was able to video a couple of loco's at the weekend from the fleet referred to by Richard Dunning in his post of March 2012. Richard uses the compensation method as described in MRJ 126 by Roger Lycett-Smith, and I don't think you could complain about the haulage capabilities of either of the loco's shown below, neither of which was struggling with their respective loads. Like I said, I am a firm advocate of springing but neither of these loco's proved difficult over the entire layout including the complex fiddleyard pointwork.







I'm guessing this is one of those topics in this great hobby of ours that is neither right nor wrong. It's simply a case of, "if it works for you who are we to contradict!!"

Tony

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Re: Gibson LMS 2P 4-4-0

Postby Dave Holt » Fri Oct 01, 2021 7:42 pm

I've never built a 4-4-0 but to me, those videos show pretty impressive haulage and track holding capabilities, whatever the suspension method(s).
I have built both sprung (coil springs, a la Brassmasters) and fully compensated (no fixed axle) models and have found no significant differences in running quality or adequate haulage capacity.
Dave.

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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Fri Oct 01, 2021 11:22 pm

But Slattocks is flat isn't it, so trains of the length illustrate should not trouble any well considered loco, particularly given the quality of Dick Petters track work. For a real haulage challenge, lifting one of his heavy 11 coach rakes round Dick's Knutsford Junction layout with its significant grade surmounted by a tight curve comes to mind. My C12 (4-4-2 tank CSB sprung) was only good for 9. Regrettably this challenge is no longer a possibility since Dick's death and the sad need to remove the layout from his house. His locos (all wheel compensated) were built for the job so the ones that find their way onto Slattocks should be able to shift anything you can get into the fiddle yard.

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Paul Townsend
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Re: Gibson LMS 2P 4-4-0

Postby Paul Townsend » Sat Oct 02, 2021 5:38 am

Will referred to removing Knutsford from its home.
Was it a preservation move or destruction?

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Re: Gibson LMS 2P 4-4-0

Postby ralphrobertson » Sat Oct 02, 2021 9:14 am

Without wishing to change the flow of this thread I just want to briefly answer 2 points mentioned here that don't relate to 4-4-0s.

First, Dick had 2 layouts, Knutsford East which has gone to a good home, and Chelford Junction which was his own permanent layout which had to be scrapped. It appeared on the front cover of Scalefour News at least once as far as I know.

Second, not all Dick's locos would work with prototypical train lengths on the level grades of Slattocks. 2 of Dick's locos have so far been converted to DCC, one works superbly, the other has proved the opposite and will require some attention before we can use it. It is not just a case of cramming lead into the loco either, it is already full, but we will need work on the adhesion of the loco before it appears with a decent length train.

If you want to comment any more on what I have posted here please respond elsewhere, this thread is about the 4-4-0 and its hauling ability and Richard's work proves there are other ways to get a 4-4-0 running smoothly.

Ralph

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Re: Gibson LMS 2P 4-4-0

Postby David Thorpe » Fri Dec 31, 2021 12:16 pm

Recently I've been reading some old Scalefour News magazines and am finding those from the early '90s particularly excellent - no, they're not as glossy as those nowadays and they don't have colour pictures, but they reflect what I think was a more cohesive and go-ahead society than the one we have today. I may get on to that later in another thread which I'm sure you'll all look forward to.......

Anyway, there was for a short time a column for "Help Wanted and Given" and in issue No. 93 David Lane asked for advice rergarding the running qualities of a "King Arthur" class 4-6-0 loco he had built. I gained the impression that up until then David had normally built locos using a fixed driven axle and three-point suspension, but in this instance he had tried a method recommended by Iain Rice with "the driven axle also suspended in sliding bearings in hornblocks with the motor suspended as opposed to being fixed, and that axle compensated by using twin beams between it and the other drivers...." Unfortunately this all resulted in a slight but annoying rocking motion that David had been unable to eliminate. He asked for any help or suggestions.

And lo and behold, in the next issue he advised that he had indeed had a suggestion. The person involved strongly recommended the need to maintain the driven axle in fixed bearings so as to get the real benefit from the three point suspension concept. The person giving that advice was none other than Bob Essery. Now if it was good enough for Bob.....

DT

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Re: Gibson LMS 2P 4-4-0

Postby grovenor-2685 » Fri Dec 31, 2021 1:33 pm

Tony W wrote: I was able to video a couple of loco's at the weekend from the fleet referred to by Richard Dunning in his post of March 2012. Richard uses the compensation method as described in MRJ 126 by Roger Lycett-Smith,

From a suspension viewpoint that appears to be the standard flexichas arrangement espoused by Mike Sharman, ie fixed rear driving axle and everything else on a central beam. The only slightly unusual feature is the pivot arrangement for the bogie.
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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Fri Dec 31, 2021 1:37 pm

David Thorpe wrote:...The person giving that advice was none other than Bob Essery...

Which all goes to prove that the most illustrious of us may occasionally talk b... say things with which the wise may wish to disagree.

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Re: Gibson LMS 2P 4-4-0

Postby davebradwell » Fri Dec 31, 2021 2:44 pm

Back in the '90s there was really only one regularly promoted way to design a P4 chassis but some have advanced a long way in the 30 years since. I'd never use a rigid axle on a loco, let alone compensation, so I'm sorry if that's less cohesive.

DaveB

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Re: Gibson LMS 2P 4-4-0

Postby David Thorpe » Fri Dec 31, 2021 3:43 pm

It was maybe a bit naughty of me posting that! In fact, I'm just rebuilding a chassis for a 0-4-4T loco and it isn't going to have a fixed axle, driving or otherwise. I'm currently trying to make up my mind whether to do twin beams on the drivers, or CSB them as an 0-4-0, leaving the bogie to look after itself.

One problem I've had with hornblocks in the past is their tendancy to stick. Has anyone any ideas as to how that can be avoided or resolved? Obviously one wants the hornblocks to move freely in the hornguides, but at the same time lateral movement should obviously be kept to a minimum.

DT

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Re: Gibson LMS 2P 4-4-0

Postby Rdunning » Fri Dec 31, 2021 4:58 pm

For the sake of clarity/completeness the Lycett-Smith arrangement for 4-4-0's is a bit more than "standard Flexichas". It also involves restricting the lateral movement of the bogie by siting the pivot for it in line with or close to the rear bogie axle and only permitting vertical movement of the beam which carries the pivot. Weight is also transferred to the bottom bogie spacer by the compensation beam, i.e. to a plane underneath axle centres, which aids stability somewhat.
As the videos posted by Tony demonstrate, prototypical loads can be hauled at realistic speeds by the two locos featured.

Compensation works, but if I build another 4-4-0 it will be sprung, in line with most of my more recent efforts as I find the improved ride and reduced noise levels of sprung chassis compelling.

A Happy New Year to all!

Richard

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Re: Gibson LMS 2P 4-4-0

Postby Winander » Fri Dec 31, 2021 6:35 pm

David Thorpe wrote:One problem I've had with hornblocks in the past is their tendancy to stick. Has anyone any ideas as to how that can be avoided or resolved?


If the bearings are too loose in the guides they can stick because I think they rotate slightly. I use High Level hornblocks and bearings and on first assembly only fettle them if the bearings refuse to move. When I have them fully assembled I use an axle in the bearing which gives me better feedback of how freely the bearing is moving rather than just holding it and it enables me to keep the bearing orientated square to the guide. So far I have only ever used wet and dry sandpaper to make them move smoothly. Don't forget that they need to rock axially.
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