Flexi Chassis an Appreciation

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grovenor-2685
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Re: Flexi Chassis an Appreciation

Postby grovenor-2685 » Sun Feb 05, 2017 4:19 pm

A travel of 1mm is 3" in full sized. Are main line steam locos built to cope with 3" jumps in track height?

I would think that prototype axlebox movement would be in that ball park, (look for pics of 9Fs where the centre wheelset has dropped off the rail).
But its not jumps that are the concern, its primarily track twist which has to be designed in, as a cant gradient, to get from level track to a canted curve, and occurs randomly as track deteriorates under traffic, with jointed track joints move quite a lot under a moving train and not always equally on both sides. The springs also act a shock absorbers limiting the damage to either track or loco when discontinuities are hit.
This shock absorbing function can be quite important with our models when you move from pottering around to trying to run an express. Our track is proportionally far more rigid than the real thing and it takes only a small discontinuity to throw a rigid axle off the track at speed.
00 modellers can rely on their deep flanges to keep the wheels in line while they are airborne, we can't.
Regards

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grovenor-2685
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Re: Flexi Chassis an Appreciation

Postby grovenor-2685 » Sun Feb 05, 2017 4:27 pm

The US region of the hobby has very little history of individuals making model chassis with working suspension,

In spite of that a detailed article on building a compensated 2-8-0 in Model Railroader Sept 1972 was one of my inspirations,notable for how closely it followed the prototype suspension design.
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Proto87Stores

Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Sun Feb 05, 2017 4:39 pm

That was the "very little part" that I was referring to. It was a magnificent piece of work that hasn't been duplicated in the small scales since AFAIK.

Thanks for the links. My own records of that item seem to have become lost during past computer upgrades.

Proto87Stores

Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Sun Feb 05, 2017 4:52 pm

That was the "very little part" that I was referring to. It was a magnificent piece of work that hasn't been duplicated in the small scales since AFAIK.

Thanks for the links. My own records of that item seem to have become lost during past computer upgrades.

Nb. Following some issues non-member message to the forum are moderated so one of us has to hit "approve" before your messages appear, hence why you did not see it immediately, and sadly we are not watching all the time.
K
Last edited by grovenor-2685 on Sun Feb 05, 2017 8:17 pm, edited 1 time in total.
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jon price
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Re: Flexi Chassis an Appreciation

Postby jon price » Sun Feb 05, 2017 5:07 pm

grovenor-2685 wrote:This shock absorbing function can be quite important with our models when you move from pottering around to trying to run an express. Our track is proportionally far more rigid than the real thing and it takes only a small discontinuity to throw a rigid axle off the track at speed.
00 modellers can rely on their deep flanges to keep the wheels in line while they are airborne, we can't.
Regards


Keith, Thanks for the info on prototype, I guessed you might know about this. Of course a beginner such as myself might well begin with a rigid small engine pottering about shunting and only get to expresses running at manline speed after developing the skills (and the space, and the money!) needed to build a large layout. Of course pre-grouping unfitted goods aren't going to hurtle around either so I think there is still plenty of room for the less sophisticated approach to start with.

Maybe we should build more flexibility intio our track (my concern so far has, of course, been to make it rigid), though this may well not be possible.

The US example you posted is a great piece of model engineering, but I am never going to get to that level. I did like the provision of dimensions for Z scale, "for completeness" though.

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Allan Goodwillie
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Re: Flexi Chassis an Appreciation

Postby Allan Goodwillie » Sun Feb 05, 2017 5:25 pm

Chaps, :)

There is already a range of chassis kits that in S4 can be put together in a day - I have never tried to build one in an afternoon against the clock, (but I have one for a Jubilee which I have not made up yet as well as all the bits required). The range also includes pacifics.

You do require a few simple jigs which you will find in my beginners threads. It will take a couple of evenings to make up the jigs, but once you make them and get down to building you will find that they will save you time and money, especially the time lost in dealing with wheel problems etc.

The chassis I am talking about are the Comet ones, although I adapt mine to have a keeper plate which means me cutting off the springs and assembling the brake gear so that they come off to allow for easy maintenance or future problems. So if I have a go at one I would reserve the little bit of extra time for the personal adaption.

I will have a go and see just how long it takes, maybe in a couple of weeks - as I have a building to push on with for Burntisland which is going to the Glasgow show and I would not like to let the side down. I have scenery to make and curtains to fit on the West Group's Calderside to complete it before then as well and at home an extension to finish - so I will be quite busy - however I will come back to this thread and maybe over a day photograph progress as I go along - it would be an interesting exercise to carry out. I will look out the bits!

Setting myself up here I know, but I have built S4 chassis from scratch in that time, it will not be a pacific, but a 4-6-0 tender loco chassis is near enough. It will be done using compensation by the way. It just takes a little longer to do a sprung chassis, whichever method is used. I will get back to this thread when I think I may have a day to spend to be able to have a go. :D

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jon price
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Re: Flexi Chassis an Appreciation

Postby jon price » Sun Feb 05, 2017 6:08 pm

I agree with Allan on the Comet chassis range. I havn't built any, but I have a Patriot chassis of theirs in the stockpile with a Bachmann body to put on top. I have a chassis jig as well. It would be a slight distraction from the current project, especuially as the valve and piston gubbins will need assembling, but the basics as you say are simple, and sprung.

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Allan Goodwillie
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Re: Flexi Chassis an Appreciation

Postby Allan Goodwillie » Sun Feb 05, 2017 10:07 pm

Hi Jon, :D

That's very interesting.

We might have had a go at them both and use skype to see what we are doing at different stages. Don't know if you use Skype on not, does not cost anything and great for chatting to family overseas. There are alternatives that allow for multiple video conferencing which would allow other parties to look on to make sure there is no cheating :!: I am just thinking of it as just an interesting exercise. If you have a pukka jig then I would be very interested to see if saved any more time than my rather basic affairs. After all it would only be one day lost so to speak,for either of us and it would, at the very least, get another locomotive near completion. :)

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jon price
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Re: Flexi Chassis an Appreciation

Postby jon price » Sun Feb 05, 2017 10:37 pm

Allan Goodwillie wrote:Hi Jon, :D

That's very interesting.

We might have had a go at them both and use skype to see what we are doing at different stages. Don't know if you use Skype on not, does not cost anything and great for chatting to family overseas. There are alternatives that allow for multiple video conferencing which would allow other parties to look on to make sure there is no cheating :!: I am just thinking of it as just an interesting exercise. If you have a pukka jig then I would be very interested to see if saved any more time than my rather basic affairs. After all it would only be one day lost so to speak,for either of us and it would, at the very least, get another locomotive near completion. :)


Well this sounds like a challenge, but our household IT probably isn't up to it, and it would contravene local regulations on hogging the IT equipment. I'm short the bogie wheels, motor and gearbox so will have to order and wait for them to be delivered. So a famous expert can build a running pacific loco chassis in 00 in a day (running or rolling? full valve gear?). Lets see what a beginner like me can make a hash of in P4. I have to confess that the tender chassis is partly complete already though the loco chassis etc is unstarted

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Will L
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Re: Flexi Chassis an Appreciation

Postby Will L » Sun Feb 05, 2017 11:41 pm

Enigma wrote:...But - I have been lured by the idea of CSB and have a couple of HL Pannier chassis to build. I'm sure that a compensated version would be a lot quicker and simpler - but I'll have a go


While I know when you use an unfamiliar it can seem more complicated than the method you are used to, having built both I would content that a CSB chassis is non more complex than a simple compensation and significantly easier to do than more complex compensation systems.

billbedford wrote:It really doesn't matter how many people found the introduction of Flexichas an inspiration, the fact remains that the majority of people who build loco kits do not use the system. ...

I accept that is probably true, and it certainly true if we exchange the work "buy" for "build". I take it we all except that less than half the kits that are bought ever have any attempt made to build them
...It is a commercial imperative any manufacturer of loco kits that they should be able to be built rigid...

Also true, I'm sure, form the point of view of the manufacture.
...using the traditional three rod method of squaring the frames, and all the evidence is that that is the method that the majority use.

Now I think we are drifting apart, While I'm happy to accept that many people faced with a chassis kit decide they can't manage to do anything more complicated than build a rigid chassis, whether the bulk of the ones who actually do start construction set out and buy the bits 1/8 silver steel rod I am rather less certain.

There is a more to be said on this but its getting late. perhaps tomorrow.

jon price wrote:...I don't know what amount of play there is in real steam locos, but our most sophisticated systems appear to allow .5mm either way.

When I first asked myself this question I was surprised to find that the 0.5 mm either side was in fact a fair approximation to common practice on the prototype

A travel of 1mm is 3" in full sized. Are main line steam locos built to cope with 3" jumps in track height? We put a lot of effort into suspension, but perhaps that effort would be more productive if it went into track that didn't have 1mm steps in it?

As Keith pointed out the issue is not steps in the track, it the degree of twist in the track across the length of the loco which is a great deal more subtle and harder to quantified or even spot. Many do try to avoid the problem by building perfectly flat track, which is certainly doable, if rather easier said then done. But then they discover that changes in level and even track super elevation are a feature of the prototype they would like to have on their layout.

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Allan Goodwillie
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Re: Flexi Chassis an Appreciation

Postby Allan Goodwillie » Mon Feb 06, 2017 12:00 am

HI Jon, :D

This could be good fun, if approached in the right way. I would not consider it possible to build a complete running chassis from a kit in an afternoon, but a whole day yes, it should be.

I have already cut away the springs etc.for fitting later, but most modellers probably would not bother to do that. Apart from that it is as it comes.

I think I have all the parts, but like you I would have to check and maybe like you I might have to buy one or two items. I could work out a plan of building if you are interested and if you have a laptop with a camera on it Skype is a piece of cake we could have a go at linking up sometime in the next few weeks just to prove it works and maybe talk about how we might tackle the construction in more detail.

If you do not want to rush it too much you could pre-manufacture the tricky bits and make a note of the time you took to do them. I have built a multitude of engines, but I am not a professional modeller and do not have any expensive jigs to help me. Just a few simple home made ones.

I tend to be better in the mornings when I can build the trickier bits ready for final assembly in the afternoon.

I would happily photograph the stages and my own timings and put them up on the forum while doing this and it may be an interesting exercise which will show my jigs in action when used on a commercial product. Let me know how you feel and the others may like to add things that they might think of, they may even join in to an assembly day. We are really only considering Comet chassis I would suggest.

Have you built any chassis at all yet, including 00?

What equipment do you have at your disposal that might help, like a wheel press or lathe, quartering jig, back to back gauge? A good vice?

I will maybe see if any of my own starters group would like to have a go with me on the same day - that is if they have a Comet chassis to build.

Chaps? :D Do you fancy a challenge?

Proto87Stores

Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Mon Feb 06, 2017 1:40 am

Will L wrote:As Keith pointed out the issue is not steps in the track, it the degree of twist in the track across the length of the loco which is a great deal more subtle and harder to quantified or even spot. Many do try to avoid the problem by building perfectly flat track, which is certainly doable, if rather easier said then done. But then they discover that changes in level and even track super elevation are a feature of the prototype they would like to have on their layout.


Here's where I would like to jump in.

There may well be areas of subtly twisted track which are difficult to anticipate. But much of the twisted track issues are fundamental. I.e. Any curve on a gradient is twisted, including any from turnouts which exit from a straight grade. So the problem isn't a case of not laying track well enough. Perfect track laying isn't good enough in those circumstances. And the twist is in some proportion to both the degree of curvature and the extent of the gradient

Which leads me to another point. I have in the past seen statements here to the fact that a well balanced vehicle with individually sprung wheels will have equal weights on each wheel. That may be true while standing on absolutely flat track, but it cannot be so on twisted track. Hooke's Law links spring force to spring movement. On twisted track, individual wheel springing fundamentally gives uneven weighting. And of course any track bumps and dips are localized instances of twisted track, which also affects the weights on the multiple wheels differently.

Andy

Proto87Stores

Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Mon Feb 06, 2017 5:18 am

Proto87Stores wrote:That was the "very little part" that I was referring to. It was a magnificent piece of work that hasn't been duplicated in the small scales since AFAIK.

Thanks for the links. My own records of that item seem to have become lost during past computer upgrades.

Nb. Following some issues non-member message to the forum are moderated so one of us has to hit "approve" before your messages appear, hence why you did not see it immediately, and sadly we are not watching all the time.
K


My apologies. It was my mistake. After I had taken a break, I returned and saw the message stil sitting on my screen later and couldn't remember if I had clicked "Submit" or not, so I clicked it again.

Andy

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jon price
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Re: Flexi Chassis an Appreciation

Postby jon price » Mon Feb 06, 2017 7:50 am

Allan Goodwillie wrote:HI Jon, :D
Have you built any chassis at all yet, including 00?
What equipment do you have at your disposal that might help, like a wheel press or lathe, quartering jig, back to back gauge? A good vice?
?

hi Allan
I have built a Mainly Trains 0-6-0 chassis (P4), rigid, which works fine under a Hornby body. an Alan Gibson 0-4-2 LNWR Dock Tank chassis (P4) again rigid which is nicely square, though currently yet to be motorised, and a Craftsman fold up chassis for a Midland 1F which is 00 but has outside cosmetic frames for P4 but has yet to have wheels fitted because the Alan Gibson wheels that go with it need crankpin holes drilling. The unfinished ones are all awaiting completion of the bodies before I progress them. and essentially stalled as I had reached the limit of my then competence or confidence and put them away until I got better at it.

Currently actually being worked on is a fairly drastic kitbash of a CSP Manning Wardle which I eventually started after (mostly) completing the Craftsman 1F body at Missenden where Messrs Tatlow and Flymo got me safely on the road to sensible soldering, and after being inspired by your starter group postings, especially the idea of sticking a paper template on the sheet metal to cut round. As far as the chassis is concerned this has involved lengthening the wheelbase and con rods, and it is being built with CSB. This was going well before christmass but my workspace was also a table and so had to be cleared for the arrival of family, and has only just got re-established, but now in a permant position, so work has picked up again

I have no machine tools apart from a scary little electric drill which I have rarely used, preferring to use a pin vice so far. I have a pillar attachment for the drill, but havn't got round to using it. I have back-to-back guages; a GW quartering jig/press; a Bill Bedford quartering jig (yes I know to use one or the other on a loco;) and a Hobby Holiday chassis jig which works very well for me, apart from stripping the thread on a rod after I locked it in place but forgot and tried to adjust it; plus the usual range of broaches, files, piercing saw, and so on. And finally, since last week a watchmaker's vice in the new workspace

Jon

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Jol Wilkinson
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Re: Flexi Chassis an Appreciation

Postby Jol Wilkinson » Mon Feb 06, 2017 10:55 am

Has Flexichas put people off getting into P4 modelling? Possibly but I think the move into model making in general is more influenced by having to learn new skills and techniques, as well as buying suitable tools for the job. How many start out with cheap but inadequate tools and consumables (solder, flux, etc.) and give up because they can't get things to work?

Most model makers would welcome simple, easy to build, detailed and inexpensive loco chassis. Look at those who are happy to use a RTR model, leaving the running gear untouched while they modify the body to get a model of a particular prototype. While OO and the majority of EM modellers would probably be happy with a rigid chassis that doesn't require any work to accurately align the axles, those of us that have chosen P4 require something a little different.

It's that difference, between 4mm scale gauges and the need for working suspension of some sort, which creates the difficulty when designing a kit. 3D printing may provide a possible answer but the sort of prices quoted on Shapeways for a bare printed chassis, such as those designed by Knuckles, would probably end up with a total price from a small supplier who has bought them in, well above what most people would pay. OO modellers in particular have been conditioned by RTR prices to pay well below what a complete kit costs. Likewise I don't think that 3D printing doesn't yet produce surface finishes that many of us would accept for a loco, tender, carriage, etc. Most tyro kit modellers might also draw the line at putting a lot of work into smoothing/preparing the model with the danger of removing some of the finer detail, although that wouldn't apply to chassis.

Fold up etched chassis, rigid for 00 and EM and with a built in horn guide system for P4, would be another option. However, that trebles the tooling cost, which is probably why it hasn't been used for "multi gauge kits" in the past.

Perhaps a mix of technologies might work. Etched frames with 3D printed or resin cast spacers having etched holes and locating lugs allowing for screw together assembly (a bit like those OO chassis from various kits in the past that used turned brass spacers) or pinned together with one of today's high tech adhesives. The design would need to provide sufficient rigidity for a rigid frame as well as hornblock guide options. Those modelling in P4 would probably accept as now, a small amount of work to adapt the standard kit. However, the need for expensive jigs to ensure accurate alignment should be avoided. Perhaps a version of the laser cut Poppy jig, but in a more robust material than plywood, would be acceptable.

That approach would also make split frames easy and fold out CSB mountings could be readily included in the etched frames. However that raises the questions of suitable wheels as nobody (AFAIK) makes a readily assemble type that would suit - fitting shorting strips would put many people off. For "standard" pickups most 00 and EM modellers would again probably be happy with Markits, if a suitable version is available (often not the case for older prototypes). Other wise it's the usual suspects, unless someone can design/produce an acceptable alternative at comparable prices.

With the end of Mashima motor supply looming, there is a need to identify suitable replacements and allow for installing those.

What these points illustrate is that we don't have a consistent approach to 4mm kit components. Many of the ranges of products available today have grown up from a lower technology process, which were available and commercially viable several decades ago. So either complete new "systems" have to be developed or we have to adapt new technologies in some areas to match what we already have available and where, such as etching, the technique is ideal for some/many components.

Obviously kit production is more economic if they can be sold in all three 4mm gauges. Etched kit production has permitted that, albeit with the need for more input from the builder. We need to remember also that OO modellers are conditioned on pricing by the RTR manufacturers and by what "model making" techniques are actually shown in the mainstream magazines. Reading RM, BRM, etc. would almost lead you to believe that model railways only come in a Red, Green or Blue box, courtesy of Felixstowe container terminal. So any new developments have to be priced to draw the modeller into the wonderful world of model making. DJH do a complete "starter" kit for an O2 Diesel shunter at £155, but compared to £80 - £100 for a finished, painted small tank loco such as a LBSCR E4 or MR 1F, it's difficult to see how many people would be attracted to buying it.

Lest it be thought I am being negative, far from it. Some of the ideas that people are coming up with are great, especially for those of us that already make models. How attractive they might make it for newcomers to get interested, how commercially viable it might be and how competitively priced such kits can be, is something we don't yet know.

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Re: Flexi Chassis an Appreciation

Postby martinm » Tue Feb 07, 2017 7:41 pm

Enigma wrote:
...But - I have been lured by the idea of CSB and have a couple of HL Pannier chassis to build. I'm sure that a compensated version would be a lot quicker and simpler - but I'll have a go

There is help at hand on http://www.clag.org.uk/pannier-csb.html - a slightly expanded version of the one first appearing in Scalefour News 182.
It shows where additional material needs to be removed for the wires - it should help with other similar adaptations.

regards,

martin

Proto87Stores

Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Thu Feb 09, 2017 6:08 pm

Proto87Stores wrote:Which leads me to another point. I have in the past seen statements here to the fact that with individually sprung wheels will have equal weights on each wheel. That may be true while standing on absolutely flat track, but it cannot be so on twisted track. Hooke's Law links spring force to spring movement. On twisted track, individual wheel springing fundamentally gives uneven weighting. And of course any track bumps and dips are localized instances of twisted track, which also affects the weights on the multiple wheels differently.

Andy


So far, given a few days to allow for extra consideration, no-one seems to have found fault with the above Physics.

However, if instead we consider the methodology of pure Equalization, the static weight carried on each wheel of a similar well balanced vehicle remains constant, regardless of track twist or any combination of bumps/dips in the track. Flexi-chas is of a course a methodology based on equalization, but was somewhat affected by the limited range of practical and economic options and parts available to modellers back at that time.

Quoting from the suspension section of the Digest:
. . . .
"2 Introduction

The term 'better running' may be looked at from several viewpoints; of these, the most important is freedom from derailment, followed closely by controllability of locomotives and their performance in terms of balance, stability and haulage capacity."
. . . .

My ongoing concern is why almost all the other threads on this forum are heavily into recommending some form of chassis springing, when equalization clearly and fundamentally is better at providing consistent wheel weighting over less than perfectly flat track, and meets the primary goals of better running as expressed above?

Andy

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Re: Flexi Chassis an Appreciation

Postby Armchair Modeller » Thu Feb 09, 2017 11:11 pm

Proto87Stores wrote:My ongoing concern is why almost all the other threads on this forum are heavily into recommending some form of chassis springing, when equalization clearly and fundamentally is better at providing consistent wheel weighting over less than perfectly flat track, and meets the primary goals of better running as expressed above?
Andy


Looking through the options at the back of the Flexichas book, it is surely very challenging to achieve equal weight distribution on every wheel for a compensated steam loco. The position of the fulcrums, the number of wheels attached to each branch of the suspension etc. will all have a significant and complex effect on how the weight of the locomotive is spread out. With Flexichas, is difficult for me to visualise how you could easily achieve anything approaching equal weight distribution on every wheel, even on dead level track. Therefore as I see it, even if an equalized chassis minimises the change in weight distribution on rough track (I will have to take your word on that), it gives no absolute guarantee that weight distribution will be good - or better than a sprung chassis.

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Re: Flexi Chassis an Appreciation

Postby Julian Roberts » Fri Feb 10, 2017 9:04 am

Proto87Stores wrote:
Proto87Stores wrote:Which leads me to another point. I have in the past seen statements here to the fact that with individually sprung wheels will have equal weights on each wheel. That may be true while standing on absolutely flat track, but it cannot be so on twisted track. Hooke's Law links spring force to spring movement. On twisted track, individual wheel springing fundamentally gives uneven weighting. And of course any track bumps and dips are localized instances of twisted track, which also affects the weights on the multiple wheels differently.

Andy


So far, given a few days to allow for extra consideration, no-one seems to have found fault with the above Physics.

However, if instead we consider the methodology of pure Equalization, the static weight carried on each wheel of a similar well balanced vehicle remains constant, regardless of track twist or any combination of bumps/dips in the track. Flexi-chas is of a course a methodology based on equalization, but was somewhat affected by the limited range of practical and economic options and parts available to modellers back at that time.

Quoting from the suspension section of the Digest:
. . . .
"2 Introduction

The term 'better running' may be looked at from several viewpoints; of these, the most important is freedom from derailment, followed closely by controllability of locomotives and their performance in terms of balance, stability and haulage capacity."
. . . .

My ongoing concern is why almost all the other threads on this forum are heavily into recommending some form of chassis springing, when equalization clearly and fundamentally is better at providing consistent wheel weighting over less than perfectly flat track, and meets the primary goals of better running as expressed above?

Andy


I don't have a view on the merits of Flexichas against CSBs, having used only the first, but what you write here surely demonstrates why it is the case that we can't get REALLY decent runnning with the idea that is widely promoted (to make it seem more accessible) that P4 works perfectly well by simply taking 00 stock and replacing the wheels. I feel that this is bound to lead to disappointment for people who "try out" P4 following this advice.

I wrote in the Snooze 199 why I think that the problem with models is their lightness so weight needs to be concentrated on the guiding wheels of the fixed wheelbase. I think CSBs may slightly do the same(?) I don't buy the idea that all wheels have got to be exactly evenly weighted unless ultimate haulage power is what you need. In my limited application of fairly short train lengths and no higher speeds than scale 30mph or so, but over a fairly complex exhibition layout, I have found my ideas work in practice for me.

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Re: Flexi Chassis an Appreciation

Postby billbedford » Fri Feb 10, 2017 2:06 pm

Proto87Stores wrote:
So far, given a few days to allow for extra consideration, no-one seems to have found fault with the above Physics.

However, if instead we consider the methodology of pure Equalization, the static weight carried on each wheel of a similar well balanced vehicle remains constant, regardless of track twist or any combination of bumps/dips in the track. Flexi-chas is of a course a methodology based on equalization, but was somewhat affected by the limited range of practical and economic options and parts available to modellers back at that time.

Quoting from the suspension section of the Digest:
. . . .
"2 Introduction

The term 'better running' may be looked at from several viewpoints; of these, the most important is freedom from derailment, followed closely by controllability of locomotives and their performance in terms of balance, stability and haulage capacity."
. . . .

My ongoing concern is why almost all the other threads on this forum are heavily into recommending some form of chassis springing, when equalization clearly and fundamentally is better at providing consistent wheel weighting over less than perfectly flat track, and meets the primary goals of better running as expressed above?

Andy


After 15 or 20 years of explaining to you why springing is superior to 'equalisation' you still don't get the point, and I suspect that most people that have tried to help you have just given up.

To recap: Springing is a dynamic system, and while the static loads may vary within small limits, the benefits of the absorption of minor perturbations in the ride height due to irregularities in the track or wheels gives a smoother ride.

Flexi-chas does not provide any equalisation, except in the case of four wheeled vehicles, and even then sprung or rigid systems provides better road holding than rocking 3-point suspensions. Flexi-chas is compensation system where the proportion of weight carried by each axle is fixed by the geometry. So in the case of a flexi-chas three axle loco frame one axle carries as much weight as the other two combined.

For equalisation both springing and compensation are used so that loads are shared and averaged between springs. This is evident on US designed bar-framed locos where springs are linked together by compensation beams, or on many diesel loco bogies.
Bill Bedford
Mousa Models
http://www.mousa.biz

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zebedeesknees
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Re: Flexi Chassis an Appreciation

Postby zebedeesknees » Fri Feb 10, 2017 6:16 pm

After 15 or 20 years of explaining to you why springing is superior to 'equalisation' you still don't get the point, and I suspect that most people that have tried to help you have just given up.


True here..

I have just tested the drawbar pull of a rigid Bachmann 24 with a sprung one. Rigid - 14% of weight, sprung 21% of weight. So 50% more pull!

Ted.

Philip Hall
Posts: 1284
Joined: Mon Aug 10, 2009 7:49 pm

Re: Flexi Chassis an Appreciation

Postby Philip Hall » Fri Feb 10, 2017 7:02 pm

I am perfectly convinced of the merits of both springing and compensation. I just haven't got around to some springing yet. However, Julian speaks of really decent running and I have to say this has always been my goal; as friends will tell you I am very fussy! Some of my conversions have had to earn their keep, not just shuffling up and down, and so I can say quite happily that quite excellent running has been had from a Hornby T9 dragging nine carriages around an undulating EM layout, and my own one in P4 will be expected to do the same. In the same vein a Hornby King Arthur conversion was intended to pull a decent length train around at respectable speeds on a big P4 layout and has been a success. Both these (and many more) have glided around without a shimmer or a shake. This is dependent, even more so with a rigid chassis, on truly concentric wheels, about which I have banged on about many times before!

So whilst I prefer some kind of suspension it is also possible to have excellent running with a conversion. Telling people this to encourage them into P4 is not misleading them, but hopefully they will try building things as well once they are amongst us.

Philip

Enigma
Posts: 236
Joined: Tue Aug 13, 2013 2:49 pm

Re: Flexi Chassis an Appreciation

Postby Enigma » Fri Feb 10, 2017 9:23 pm

martinm wrote:
Enigma wrote:
...But - I have been lured by the idea of CSB and have a couple of HL Pannier chassis to build. I'm sure that a compensated version would be a lot quicker and simpler - but I'll have a go

There is help at hand on http://www.clag.org.uk/pannier-csb.html - a slightly expanded version of the one first appearing in Scalefour News 182.
It shows where additional material needs to be removed for the wires - it should help with other similar adaptations.

regards,

martin

Thanks Martin. I've read that article a couple of times and it sort of makes sense but I've not had the actual kit with me at the time. When I make a start on it I'll read it again!

Proto87Stores

Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Sat Feb 11, 2017 5:02 pm

zebedeesknees wrote:
After 15 or 20 years of explaining to you why springing is superior to 'equalisation' you still don't get the point, and I suspect that most people that have tried to help you have just given up.


True here..

I have just tested the drawbar pull of a rigid Bachmann 24 with a sprung one. Rigid - 14% of weight, sprung 21% of weight. So 50% more pull!

Ted.


Two quick points:

1 Please don't confuse Equalization with rigid chassis. Rigid chassis is the problem, chassis equalization is one of the major cures. Wheel springing in various forms, is another. Correct equalization however, should give the maximum [possible TE before wheel slip. You would likely get slightly more pull with chassis equalization than with any form of chassis springing.

2 What Bill omitted to mention was that the above, even in only Flexi-chas compensation form, has been tried, tested and proven by the S4 Society. IIRC, Around the 2000-ish time, maybe 8-10 years prior to your membership date, there was an annual competition event called the Deputy Chairman's Cup. This competition tested several member submitted models locos to assess their degree of track holding and the best possible pull.

At the last event under that name, well known designer member Ted Scannell, apparently with Bill Bedford's "help", and with great fanfare at the time, submitted one of the very first "CSB" based models. This was well publicized in order to prove the good value, if not "superiority”, of that then new form of springing over other chassis suspension methods. The outcome was actually good and showed that CSB is definitely a good workable solution, as the model came second in the competition.

The loco that took first place was however, one that used the standard Flexi-chas form of chassis. . . .

Actual or supposed "superiority" of wheel springing in either theory or practice, for model track holding, is a very difficult process to demonstrate in practice, and I suspect even more so to prove in theory. But it does has a very nice warm fuzzy feel to it.


Andy

billbedford
Posts: 680
Joined: Tue Oct 02, 2012 2:40 pm

Re: Flexi Chassis an Appreciation

Postby billbedford » Sat Feb 11, 2017 5:44 pm

Proto87Stores wrote:1 Please don't confuse Equalization with rigid chassis. Rigid chassis is the problem, chassis equalization is one of the major cures. Wheel springing in various forms, is another. Correct equalization however, should give the maximum [possible TE before wheel slip. You would likely get slightly more pull with chassis equalization than with any form of chassis springing.


Please do tell us just we should 'equalise' six wheeled without using springs.
Bill Bedford
Mousa Models
http://www.mousa.biz


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