Flexi Chassis an Appreciation

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grovenor-2685
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Re: Flexi Chassis an Appreciation

Postby grovenor-2685 » Thu Mar 02, 2017 8:15 am

What I am interested in though is something really easy to P4-ize a RTR wagon

Masokits do a fret for just this purpose, and if you do only one axle per wagon you will get twice as many for your money, and if you find problems with that you can always do the other axle later.
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Re: Flexi Chassis an Appreciation

Postby Will L » Thu Mar 02, 2017 4:20 pm

Julian Roberts wrote: On a large layout there are bound to be small track issues that may come and go with heat and humidity. A robust suspension system on every vehicle that really works as intended seems to me the sine qua non of realistic operating.

One has to agree. However, if converting a RTR wagon, I'm not sure I would go for springs at one end only. If not doing a "proper job", I would have though a compensation unit at one end would have been preferable as you could be sure you had got the wagon level the same at both ends. Instability due to using compensation on a 4 wheel wagon can be minimised by ensuring the wagon weight is as low as possible, which in a plastic bodied RTR wagon should not be problem. The other, near unmentionable, solution is the EM gauge wheels at P4 BtoB heresy.

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Re: Flexi Chassis an Appreciation

Postby allanferguson » Thu Mar 02, 2017 4:43 pm

In the Early Days, of course, it was an article of faith that all vehicles were compensated, on the "three legged stool" principle. I do remember some very abstruse discussion on whether it was better to have the fixed axle or the moving axle leading when being pushed, particularly round bends. Sprung buffers also came into the discussion, as I recall.

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Re: Flexi Chassis an Appreciation

Postby Allan Goodwillie » Thu Mar 02, 2017 5:30 pm

The use of wagons without any compensation is possible depending on how accurately they are made. I have a hopper train made out of 21T Airfix wagons to simulate one of the ballast trains which ran to Kingmoor yard during its construction. Tebay had two WD 2-8-0s for this role. None of the wagons has compensation and it runs fine on Grayrigg super-elevation et all. :)

I am curious to see how they run when I get a longer 20+ trainload going. After all, many modellers get diesel locos to run simply by a wheel change.

A while ago I was trying to get more and more wagons running up the 1in 70/5 gradients and dropped the individual wagon weight from 2oz to 1.5 oz. This was not a good idea as I could not get the wagons to run consistently and stay on. It was possible to make up set train loads placing selected wagons with 2oz loads at the front of the train with lighter wagons further down the train,this did work to a certain extent and allowed longer trains to run, but this was no good if my stock was going to exhibitions and being mixed with other wagons. In the end I have returned all wagons to the 2oz rating.

I understand Philip going for a simple solution at times if it works for him and the main thing is that the wagons run properly. I have something like 300 plus wagons for different companies and periods and maintenance can become a burden especially if you are taking stock to exhibitions and they are not just staying permanently in rakes on a layout at home.

I do believe that the key to running is producing good baseboards and track which is made with care and properly set up using uncompensated stock to check the running and without check rails being fitted during the testing stage. :)

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Re: Flexi Chassis an Appreciation

Postby Philip Hall » Thu Mar 02, 2017 7:10 pm

Thanks Allan. That was my main point, that it works by keeping it simple. It would be lovely to have everything with suspension, but I am concerned that on a large project time is of the essence! I have compensated vehicles at one end only many times, and it's quick and works, but then I found that in medium length trains at least I could get away with weight and dead true RTR chassis.

One solution I have used with success, which does push the wheels down rather than allowing them just to flop, is to arrange fine wire springs bearing on the axle just inside the wheel on one end if the vehicle. It doesn't impede the free running and can also be done at both ends, but I found little difference. The fine wire springs can be bent so that they don't show at all.

The maintenance requirement does bother me a bit, especially as the stock increases and the years pass. I remember many years ago visiting the late Ken Northwood to photograph the North Devonshire for MRJ. I had met him a year or two earlier and been impressed how well the layout ran. But on the photographic visit Ken had by that time become quite ill, and left a friend and I in the railway room to take the pictures. "You know how it all works" he said and left us to get on with it. It was during that session that we found out how the lack of maintenance, which he'd had to give up on, had affected things. It still ran well, but bits had dropped off and we had to put them right.

I'm hoping that my basic ideas will help and keep it simple. TIme will tell...

Philip

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Re: Flexi Chassis an Appreciation

Postby Julian Roberts » Thu Mar 02, 2017 11:53 pm

grovenor-2685 wrote:
What I am interested in though is something really easy to P4-ize a RTR wagon

Masokits do a fret for just this purpose, and if you do only one axle per wagon you will get twice as many for your money, and if you find problems with that you can always do the other axle later.
Regards


Thanks for the idea Keith. So far I haven't had any luck with the Society link to the Masokits catalogue.

My first post on this Forum at viewtopic.php?f=23&t=693 was on the very same subject. The thread there got hijacked by a debate about the heresy of using EM wheels as Will mentioned earlier today, but I don't think much has changed these last seven years.

Since then I have completely proved to my satisfaction that MJT wagon compensation works, with adequate weight. I don't want to tempt fate nor sound overly boastful but as far as I know none of my my so equipped wagons have ever once derailed at an exhibition, unless for example a point has not thrown properly or some very obvious track fault has happened. Why I ask if there is an even easier way is that people seem so keen to persuade me that rigid will do because there isn't time to convert everything - yet people are happy to spend what surely must be at least as much time on elaborate weathering or other cosmetic work. Were I to get into the groove, I would think that the time taken to install the MJT inside bearing even in my elaborate way would be less than a morning's work.

I just think that the only acceptable standard for derailments (in a Society that professes to "Get It All Right") is zero, in the same way as Tony Wright said in the Snooze, some while back, is his standard.

I also readily admit that to have compensation or suspension of some sort applied to any vehicle doesn't mean it's not going to derail. It depends on whether the design and/or execution of that design is adequate, and I agree that a rigid vehicle is going to behave better than one with a poorly installed or designed suspension.

Anyway as Allan said, to divert the subject to wagon suspension is not sticking to the thread.

So to get back on topic here are two more videos (very short because I didn't have much space on my phone) of the Barclay Tank I showed earlier careering round an impossible reverse curve. Now it's finished except for a rather iffy paint job and here it is drifting over the 3 way of the Calderside Exchange Sidings that also got their first outing last weekend at Glasgow's Model Rail Scotland. It is equipped with a Flexichas suspension, with two longitudinal beams between the rear two axles and a rocking front axle, the rear beams optimized for roadholding as per my Snooze first article. It did not derail once this first weekend of revenue earning service, and again I don't like to boast but have to say that none of my stock derails despite some slightly iffy trackwork in some places on the layout that does catch other stock out, unless something goes out of adjustment like the B2B or a loose tyre.




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Re: Flexi Chassis an Appreciation

Postby grovenor-2685 » Fri Mar 03, 2017 12:22 am

So far I haven't had any luck with the Society link to the Masokits catalogue.

No idea why that would be, it always opens or downloads just fine for me, anyway I have downloaded it and attached it here if it helps.
michaelclark18.pdf
(1.19 MiB) Downloaded 92 times

The relevant items are in section 7.

The videos look good but I would add that the benefits of springing for trackholding don't really show up crawling around at shunting speeds. if fact for vehicles on 2 4 wheel bogies its pretty marginal anyway, can you tell which are rigid, which are sprung and which are compensated in this train?

or even here with wagons

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Re: Flexi Chassis an Appreciation

Postby billbedford » Fri Mar 03, 2017 9:53 am

Just the noise suggests that none of those coaches are sprung.
Last edited by billbedford on Fri Mar 03, 2017 1:39 pm, edited 1 time in total.
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Re: Flexi Chassis an Appreciation

Postby Julian Roberts » Fri Mar 03, 2017 1:34 pm

can you tell which are rigid, which are sprung and which are compensated in this train?


I don't think it matters so long as they stay on the track!

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Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Fri Mar 03, 2017 7:40 pm

Will L wrote:I feel an "are but" coming on

Proto87Stores wrote:But we have established that equalization keeps the weight per wheel the same while going over those small (or even large) perturbations in track flatness, as well as being unaffected by track twist.

While that may be true with a stationary wagon, I'm not so sure when the vehicle is in motion. As a wheel lift must accelerate the weight of the body upwards and by newtons third law.... So I'm not so sure that, once in motion, this distinction between sprung and equalised suspension is anything like so clear cut.

In the sprung wheel dynamic case, a short distance impulse (track bump) will compress a per wheel spring , and under Hooke's law, pass an increased upward force directly to that supporting part of the rigid chassis above it.

In the equalized wheels dynamic case, the same impulse will lift one wheel the same amount, but the connection to the rigid chassis will only be lifted by that amount divided by the ratio of the beams and fulcrums between the wheel and the rigid chassis support point.

But then that the amount by which chassis will be lifted in the sprung example will also be less than the amount the wheel lifts. When static, analysis on a 4 wheeled vehicle suggests 50% less. Could your equalisation improve on that? On individual wheels possibly but not on average over whole vehicle .

For our 4 wheel example, equalization will lift one side by half the bump height and the center by half that. So 25%.

Then when you consider the dynamic case with vehicle in motion, with equalisation, the vehicle body must lift by the full amount required instantly, where as in the case of the sprung suspension, the lift to the body will occur relatively slowly (because the weight of the wheel is small compared to the weight of the body and the body's inertia will predominate), and, unless the wheel remains raised over a relatively long period, will the never achieve the full amount of lift to be expected in the static circumstances.

The weight of the vehicle can't change just because the vehicle is moving along at a constant speed. If there is a bump on one wheel, then the differences are as follows.

Equalized: The impact on the chassis is that the chassis is lifted by the lever effect of the beam or beams and their fulcrums between the wheel and the chassis. E.g for a 4 axle bogie vehicle, the first wheel lifts the center of that bogie side frame by half the height, but with twice the force. Ditto for the end of the of that bogie bolster lifting the king pin of the bogie, ditto for that bogie king pin lifting the end of the body. The combined body /chassis end movement will be almost instantaneous, but very much smaller than the bump. (1/8th in this case) For a major track bump of the worst case 1/2 mm height, the end of the body would lift 1/16 th of mm. For the sort on minor track irregularity that Bill was talking about, the body movement would only be 1/16th of that. Probably undiscernable, and most likely undetectable, much as per Keith's posted you tube clip.

Sprung wheels, but otherwise rigid. : The first wheel spring tries to fully lift the entire end of the body by the bump height. But due to the inertia of the otherwise rigid system the spring will compress to some extent, and the usual F=ma applies to get the end of the body moving up at some slower rate. Given the that the inertia is significant, the energy not yet fully applied to the body is stored in the spring compression. This introduces a time delay factor as well as gradually reducing the weight carried various of the other wheel springs. To fully follow the exact body motion and the variation of the wheel weights would take a moderate computer program. But if nothing else changed changed subsequently, everything would settle down to the same effect of the static case offset movement and position.

Once we consider the delaying effect of springs due to inertia effects, the analysis and impact has to consider damping and the resonant frequency of the sprung system. The unfortunate result is that it quickly becomes obvious that the result of springing (good or bad) is not constant, but then significantly dependent on the vehicle weight and speed and the rate at which bumps occur. This was already hinted at in the posting talking about the highly "tuned" sports car suspension



If you want a more obvious example of that fact that direct wheel springing is worse at track holding than more equally weighted wheel following, then test drive a sports car. The harder the suspension, the better the handling.

billbedford wrote:But such suspensions don't always keep all four wheels on the road:

In case nobodies noticed high performance cars have sprung suspension, even in a FI car where its is mostly in the walls of the tyres. The difference in handling Andy describes is primarily the difference between short travel firm springing as against long travel soft springs.


I'm going to jump ahead and point out that I'm very much in favour of springing the "body". But treating the body as the heavily weighted high inertia item, that is siting on just four springs on top of a much lighter and simpler "chassis", which has only equalization. The result then is that the chassis has the maximum possible model track holding and traction, while the body has the simplest and least cost, symmetrical a stable 4 point springing, well isolating it from the track perturbations and giving the appearance of the heavy mass of the real vehicles.

Andy

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Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Sat Mar 04, 2017 12:59 am

Julian Roberts wrote:Thanks Allan. I wondered if anyone had seen my post. I rather think the whole discussion (as immediately above) has moved a long way from appreciating the elegant simplicity of Mike's concept, and shows good reason for his frequently expressed scepticism for the opinions of "experts".

What I am interested in though is something really easy to P4-ize a RTR wagon - and only one axle needs any work. I think the rigid 4 wheel wagon is just not good enough on P4 layouts running-wise, but my quest is to make it easy, VERY easy, to give it fool-proof-ly successful suspension - even easier than the MJT compensation, and possibly even more reliable in that the weight would not teeter around in the middle but bear down directly above the wheels in question if it was basically a pair of springs acting on the 2 wheels.

The issue in P4, it seems to me, is making trains that actually stay on the track and that can accommodate reasonable track faults given realistic speed control. Not pages of incomprehensible debate about indiscernibly minute differences of ride quality.


Mike was before my S4 time, but I support his intended simplicity, both for reliability and the implied lower cost. And all of your goals above. Although any elegance is of course in the eye of the beholder and not in my list of improvement objectives. I'm just happy that I've been able to take the simplification even further, and added several benefits as a result. Such as the list of tools required ( Needle nose pliers and two hands ).

I've now achieved the objectives for just about my bogie vehicles, including having some very easily modifed RTR Bo-Bo locomotives. The four wheel wagon is as yet un-attempted. My motivation is somewhat dampened as I admit to not needing any such wagons personally. And I'm not sure there is much cost saving to be mad on such small, simple vehicles. But the principles will work just as well.

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Re: Flexi Chassis an Appreciation

Postby Julian Roberts » Sat Mar 04, 2017 6:47 am

I put that video of my Barclay Tank up partly to show the smoothness you get with Flexichas if you don't have a fixed pair of wheels. I should have added that it weighs just under 300g. Obviously it really needs a comparator video showing other kinds of suspension in operation. One of our members has a CSB equipped loco and we have some appropriately prototypical (for exchange sidings) rough track joints so next exhibition I will take some more.

I'm certainly not going to bother putting springs between the chassis and body! Life is too short!

I made the step of realizing there are lots of
advantages to having no wheels fixed in the chassis after my last loco. Given that all will be in hornblocks, the added complication of two longitudinal beams is not so very great compared
with the standard front two axles and one central beam.

One thing I did not expect is that with the detachable brakes on this loco, these (because of their pullrods) keep the hornblocks in the chassis and there is no need for fiddly bits of wire at the bottom of each hornblock. Its much easier just springing the brakes off to get the wheels out. Thus the pull rods act as a keeper plate!

I must thank you Allan and Philip for your ideas on wagons. Allan you will be able to show me the Mike Gilgannon system but I wonder Philip if you can photo one of your wagons that has small springs acting downwards onto the axle? What I wonder is, how the wire is fixed onto the plastic vehicle at its other end.

And thanks Keith for your video. I wonder why 20ish wagons need a banker and 15 coaches need three diesels -albeit two of them are Type 1's? Nice steam whistle...

I will write to Michael Clark as it seems he has no email to get more info. Not that I am unhappy with my MJT wagons but in case this offers a quicker way of satisfactorily giving two wheels that follow the track vertically as well as horizontally.
Last edited by Julian Roberts on Sat Mar 04, 2017 11:07 am, edited 1 time in total.

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Re: Flexi Chassis an Appreciation

Postby grovenor-2685 » Sat Mar 04, 2017 9:46 am

And thanks Keith for your video. I wonder why 20ish wagons need a banker and 15 coaches need three diesels -albeit two of them are Type 1's? Nice steam whistle...

That run is on 1:20 uphill, and the WD/Jinty have about half the load each. The 3 diesels were not needed, just a consist trial, two of the locos were needed although one Co-Co can manage.
And the coaches are about equally divided between sprung, compensated and rtr bogies.
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Re: Flexi Chassis an Appreciation

Postby grovenor-2685 » Sat Mar 04, 2017 9:53 am

I've now achieved the objectives for just about my bogie vehicles, including having some very easily modifed RTR Bo-Bo locomotives.

Well, since you have cracked it perhaps you could favour us with some details. You did show off some coach bogies a while ago but I can't find them on offer on your website anywhere or I would have sent in an order to give them a try.
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Re: Flexi Chassis an Appreciation

Postby Julian Roberts » Sat Mar 04, 2017 11:29 am

Andy
Although your last post was around 1am and mine after 7am it had not appeared when I wrote mine.
The debate here re 4 wheel wagons boils down to a time issue, so that for many or most people the improvement versus time trade off, then factoring in cost, says leave the wagon rigid.
I put what might be a tiny improvement in reliability above time and the small cost, but readily admit I only have about 15 wagons, plus 7 locos and 4 coaches, to show for my 10 years modelling in P4 - though I do still work for my living too.

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Re: Flexi Chassis an Appreciation

Postby Philip Hall » Sat Mar 04, 2017 1:13 pm

Julian,

Can't provide a photo right now I'm afraid but the fixing is very simple, I just melted the end of the wire into the plastic floor with a soldering iron. The thin wire just rests on the axle. If it shows in a side view I just bend it around a bit until it doesn't.

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Re: Flexi Chassis an Appreciation

Postby Philip Hall » Sat Mar 04, 2017 7:31 pm

Julian,

Just found an old Airfix vehicle, top picture, and you can see the spring wires either side of the lead weight, melted into the floor. The lower picture is of a Bachmann SR Pillbox van, with a single spring wire soldered to the brake cross shaft. In this case I did it at the opposite end as well, and it works as well as the earlier vehicles. Some twenty-five years separate the scruffy early effort from the slightly better new one!

Hope this helps.

Philip

IMG_1404.JPG


IMG_1403.JPG

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Re: Flexi Chassis an Appreciation

Postby Julian Roberts » Sun Mar 05, 2017 10:26 am

Many thanks Philip. Soldering plastic is still something I haven't ventured into but obviously is the thing to do here.

Not sure I would fix AJ coupling wire ends in this way though...I glue and screw a bit of copperclad for them to be fixed to..overkill?...wandering off topic...!

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Re: Flexi Chassis an Appreciation

Postby Julian Roberts » Sun Mar 05, 2017 6:04 pm

Before this thread is quite dead:
Any chassis assembly has always required a modicum of skill and making them run after that requires a bit more, and it is true that either the skill or the patience to develop it isn't given to everybody. None the less my experience is that Fexi chassis significantly extends the group of modellers able to produce a satisfactory working chassis.


So said Will at the beginning of this thread and I just wanted to say hear hear to that and express my gratitude to Mike for his ideas. And to Will for your thread in appreciation of them, even though you are obviously committed to promoting CSBs as a natural progression and improvement.

I had another look at Mike's book and to my surprise found the following second paragraph:

So what is the required result? What it is not is just to keep our trains on the track, as long as the wheel flanges are deep enough, our old rigid chassis have done this fairly well for years though with the fine scale wheels and systems now available, this does become part of the story. The main point is to achieve better electrical pick up, adhesion and therefore performance, and get rid of finger poking and baseboard bashing as a means of starting locomotives.


As I said in my Snooze articles, I think in P4 a little bias to the outer wheels of a fixed wheelbase better guarantees trackholding where the track might be less than perfect - which seems to me a more realistic pragmatism than expecting the track to be and stay perfect.

Allan Goodwillie said;
Most of the bigger engines came to grief on the test track with bogies and pony trucks and trailing wheels giving most trouble. :shock: A consequence of all this was that a simple 0-6-0T seemed to win the trophy each year, perhaps not too surprising.


It seems to me this illustrates a problem: it is not necessarily at all easy to organize trailing wheels to take a share of the load as per Mike's diagrams without them at times being caught up with fixtures like the loco mainframes, when we expect our models to take sharper curves and quite possibly bigger track irregularities than the prototype. Even if they don't take a share of the load they can come to grief for the same reason and/or if they are not sprung downwards to hold the track sufficiently strongly.

Next project for me is a simple Comet P4-ization of a Bachmann Crab where the pony wheel will be my uncharted territory, and I may try making the loco mainframes in front of the cylinder a trompe d'oeil and part of the pony wheel, not fixed to the loco, with the pony able to move up and down relative to the frame which will be able to curve independently of the loco. As per what I was trying to express re the LMS Compound at
viewtopic.php?f=19&t=5277

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Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Mon Mar 06, 2017 8:25 pm

grovenor-2685 wrote:
I've now achieved the objectives for just about my bogie vehicles, including having some very easily modifed RTR Bo-Bo locomotives.

Well, since you have cracked it perhaps you could favour us with some details. You did show off some coach bogies a while ago but I can't find them on offer on your website anywhere or I would have sent in an order to give them a try.
Regards


The coach bogies won't be available for sale until I organize a steady supply of nominal 2mm dia. axle material that is a moderate force fit for the 2mm ball bearings. I also have to complete the bearing press tool, so that I can supply the bearings pre-assembled on the axles. The other "tooling" item to do is an assembly instructions video. For those used to soldering lots of tiny brass bits together, assembling these is going to somewhat different

Delivering on all the above is hampered by my current heavy workload of non model tasks. E.g. A heck of a Honeydew list and working on a Intestate Probate with 34 unknown overseas beneficiaries.

The detail/benefits of construction I can mention hopefully clearly prior to having video are:

No hornblocks. Wheel up-down movement is simplified by mounting the wheel bearings on the equalizing bars. Axles with bearings (with or without wheels fitted) can be hand snap fitted at the end of construction, and removed later if needed just as easily.

Bogie body and bolster combined is a simple folded open sided box, of top and bottom "U" pieces that when assembled aligns and clamps the very short side frames in place with the equalizing bars locked inside them. The box is held together by an internal torsion plate which has twist tabs to lock the ends. (That's the part that needs the needle nose pliers).

Body springing is optional, using your choice of 2 or 4 precision steel coil springs set into the top of the bolster box with plastic bushes, which provide some friction damping. A vertical 2mm screw is also set into the box top top act as the bogie pivot. A rubbing plate for the springs to bear against the underside of the car floor is optional if needed.

All the above except the bearings, springs, bushes and screw is comprised of one or two small standard box etches and a separate small equalizing bar etch which is specific to the wheel base required. Some tabs are provided in key places to ensure that incorrect assembly is (almost) impossible. No particular skills, measuring, adjustment, soldering or filing are required. Assembly time is just a few minutes.

Andy

Proto87Stores

Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Tue Mar 07, 2017 7:28 pm

Julian Roberts wrote:Before this thread is quite dead:
Any chassis assembly has always required a modicum of skill and making them run after that requires a bit more, and it is true that either the skill or the patience to develop it isn't given to everybody. None the less my experience is that Fexi chassis significantly extends the group of modellers able to produce a satisfactory working chassis.


My goal, which appears to be quite easily possible, is to reduce the modicum of skill to merely mounting the wheels on the ends of their axles. All other aspects of chassis construction could be almost as simple as per my bogie construction example in my prior post.

So said Will at the beginning of this thread and I just wanted to say hear hear to that and express my gratitude to Mike for his ideas. And to Will for your thread in appreciation of them, even though you are obviously committed to promoting CSBs as a natural progression and improvement.

Nature's way of evolving gradually from existing success has very little to do with suddenly switching out Mike's beams with a single vehicle length piece of springy wire. Particularly if, as Will said, none of the design tools worked on so far, include any dynamic analysis.

The clearly recognized CSB success to date is based on many modellers experience of improvement (running and construction) over basic Flexichas or the construction and adjustment complexity of "simple springing" than a progression from Flexichas principles. And for those CSB systems that have been built, or under currently under construction, I'm not suggesting that they should be replaced. But AFAIK CSB's have yet been compared with the simplified construction and running of advanced model equalization, with or without separated body springing, which I'm proposing. If that type of suspension turns out to be much simpler, cheaper and easier to make, then it can become a useful additional method in the Scalefour arsenal of ways of recruiting more novice modellers to P4.


I had another look at Mike's book and to my surprise found the following second paragraph:

So what is the required result? What it is not is just to keep our trains on the track, as long as the wheel flanges are deep enough, our old rigid chassis have done this fairly well for years though with the fine scale wheels and systems now available, this does become part of the story. The main point is to achieve better electrical pick up, adhesion and therefore performance, and get rid of finger poking and baseboard bashing as a means of starting locomotives.


Mike's paragraph was also referring to EM as well as P4. So the reliable track holding of deep flanges could be taken for granted as one of the higher priorities. Although some his "finger poking" concerns could also be laid at the door of the crude and cheap 3-pole motors that abounded in RTR mechanisms then.

As I said in my Snooze articles, I think in P4 a little bias to the outer wheels of a fixed wheelbase better guarantees track holding where the track might be less than perfect - which seems to me a more realistic pragmatism than expecting the track to be and stay perfect.

Allan Goodwillie said;
Most of the bigger engines came to grief on the test track with bogies and pony trucks and trailing wheels giving most trouble. :shock: A consequence of all this was that a simple 0-6-0T seemed to win the trophy each year, perhaps not too surprising.


It seems to me this illustrates a problem: it is not necessarily at all easy to organize trailing wheels to take a share of the load as per Mike's diagrams without them at times being caught up with fixtures like the loco mainframes, when we expect our models to take sharper curves and quite possibly bigger track irregularities than the prototype. Even if they don't take a share of the load they can come to grief for the same reason and/or if they are not sprung downwards to hold the track sufficiently strongly.

Next project for me is a simple Comet P4-ization of a Bachmann Crab where the pony wheel will be my uncharted territory, and I may try making the loco mainframes in front of the cylinder a trompe d'oeil and part of the pony wheel, not fixed to the loco, with the pony able to move up and down relative to the frame which will be able to curve independently of the loco. As per what I was trying to express re the LMS Compound at
viewtopic.php?f=19&t=5277


If I might offer a suggestion re: unpowered bogies and pony trucks and trailing wheels. It should be possible to achieve maximum track holding by weighting those independently, rather than having them a too complicated part of the overall springing or equalizing mechanism. Some creative indirect weight placement would likely be necessary, but the results should be worth while. E.g. a significant independent extra weight hidden in a smokebox, could be supported solely on a leading pony truck via a vertical post.

Finally, I did notice Mike's aversion to "fancy technical stuff", but checking the dates, I wonder if he might have been referring to the then current "Magna-desion" ideas coming from the major RTR firm of the time. Clearly something that would not be possible to emulate with simple "4mm home Blacksmithing" tools.

Andy

Philip Hall
Posts: 1500
Joined: Mon Aug 10, 2009 7:49 pm

Re: Flexi Chassis an Appreciation

Postby Philip Hall » Wed Mar 08, 2017 11:01 pm

I have built a few engines over the years which seem to have Magnadhesion. Accidentally, so I hope Triang's patent has expired. It simply occurred by putting a motor with a big magnet next to steel tyred driving wheels.

I think it did actually assist with traction a bit. The drawback is picking up an engine when the track, if not fixed down, comes up with it!

Philip

Proto87Stores

Re: Flexi Chassis an Appreciation

Postby Proto87Stores » Mon Mar 13, 2017 6:31 pm

I'm going to be etching a batch of my new chassis for my LNER Liverpool St. N7 0-6-2's. I was wondering if anyone knows it that would also be dimensionally correct (or near enough for RTR 00/EM fans ) for the Kings X N2's as well? If so, they might be of use to others.

I'm also looking at buying a dozen or so of the Dapol 16 ton wagon kits, and etching up a wagon chassis for those, as a proof of concept. The couple of lower price on-line suppliers I seen so far don't keep very much stock. Any recommendations for where I could best obtain those?

TIA
Andy

David Knight
Posts: 678
Joined: Sun Jul 20, 2008 6:02 pm

Re: Flexi Chassis an Appreciation

Postby David Knight » Mon Mar 13, 2017 8:49 pm

Andy,

Not sure how prices compare but http://www.modelrailwayimports.com/ is a good dealer. Most wagons are around $22 CDN which should work to your advantage. I've had good service from Steve over the years.

HTH

David

User avatar
grovenor-2685
Forum Team
Posts: 3370
Joined: Sun Jun 29, 2008 8:02 pm

Re: Flexi Chassis an Appreciation

Postby grovenor-2685 » Mon Mar 13, 2017 9:02 pm

Note that there are already several etched chassis available for the 16T Mineral wagons of varying degrees of sophistication/complexity so another one is unlikely to be a big seller.
Regards
Regards
Keith
Grovenor Sidings


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