Sprung chassis, principles and easy applicaton

[bertiedog]

That Varney is a good representation of a floating motor, the only attachment for the motor was a shouldered screw underneath at the back on which the motor pivoted.. Torque rods are needed, with floating motors, the screw on the Varney acted as one, it just needs a flexible but firm attachment at or near the pivot point.

 

 

Yes you can have the motor rigid to the frame, and a universal joint, but the gearbox or gear frame still has to have a wire to stop the casing rotating, and transmit torque to the chassis.. A suitably long wire will allow the springing to work, but take the torque force.

 

My favourite layout for goods and lager passenger tender locos is a tender mounted motor, with a large flywheel, driving under the footplate to the rear axle via a shaft, no boiler cut-outs, solid brass or lead boiler, and full backhead details. all the space under the frames available for the gearbox and springing components. If you add Mike Sharman s Floating tender, which transfers the weight of the tender,(with the motor and flywheel), to the main chassis, you will have a monster hauler on your hands.

 

A Q1 I did, from a k's kit, had full springing, with a tender mounted motor, a large flywheel on a Mitsumi, (yes Mitsumi), motor with ballraces, it had a weight transfer chassis as well, so the loco weighed more than the loco weight!!...(adding the tender and motor)....it was a monster, the pulling power was incredible, far beyound any test trains we could muster..

 

Stephen.

[bertiedog]

An example to demonstrate adding springing in Gordon Varney's fashion,, a K's 042 GWR chassis, from many, many, moons ago, with the U bearing chassis, 1/2 th inch width brass frames, cast whitemetal parts in it.

 

It is the type not liked today, pressings, not etchings, but in nicer thick brass. No bearings as such, the axles ride in the U shaped slots.

 

 

The keeper plate on the bottom retains the wheels which move up and down in the slots...useful!

 

 

 

Its got nickel silver Romford wheels and they run true, but need a good clean and polish to the tyre. The nickel silver side rods appear accurate, but the holes are big," opened up" is the expression I believe, in this case un-needed. The gear appears usable, quite accurate, but may be replaced on closer examination on striping down.

 

There are extra holes in the side frame for brake hangers, and they match the position and size for Hamblings cast metal brake shoes, made by Sayer Chaplin, vintage for the 60's when this kit dates from. They were cast whitemetal, plated with hard nickel. I will replace with scale brass hangers and shoes,

 

 

 

The frames are held on frame spacers by BA screws, and the frames are easily widened to more civilised standards for finer scale OO, this is not being converted to P4.

 

1/2 inch was often chosen as parts were made widely to this figure, and it allowed very generous sideplay. This equates to 12.7 wide, and the back to back should be 14.5, so a big gap of 1.8 mm to fill, a small washer each side frame spacer and some very thin washers on the axle should get it to about 14 mm wide, leaving .25 mm axle washers each side, still enough play for an 042.

 

 

 

The bearings will be tubular brass tube, I will turn them in a lathe, but plain brass tube is made, and easily available. It will need a cover over the gear, on the keeper plate, and a new floating mount for a small 5 pole motor.

 

The design will be fully floating, with a bogie for the rear, self centering and lightly loaded with a coil spring, to balance the weight at the front.

 

I'll strip and make the parts and re-assemble to show the springing, using 14 thou guitar steel wire, plus some coils spring on the ends with adjustable shackles to level the loco under load. with the body on.

 

To maintain a comparison, I find a K's standard GWR 042 will haul 12/15 wagons, normally weighted, in the past, I cannot test this one, it was bought as scrap on Ebay, without even a motor in place. We shall see what it hauls after springing etc.

 

Stephen

[bertiedog]

As a reference, a drawing of the GWR 1400 class 042, showing K's frames were accurate but disregarded the locomotive springs and the ashpan, the springs may still be left off, they are rather hidden, I may fit them later attached to the keeper plate.

 

 

The adjusters will go at the back end with the coil springs in the ashpan area., and a new frame spacer added above the rear axle position to take a coil spring that will bear on the trailing axle.This will be topped with a screw to adjust the down pressure, to level things when the main suspension is set. It should just be hidden by the back plate of the boiler.

[bertiedog]

The stamped K's frames have the usual warp, they are banana shaped, cupped upwards at the ends, this would not have affected an 040 chassis too much!!!, but disaster on an 060 or bigger loco chassis, where the middle axle would below the correct line.

 

When brass strip has slots or keys stamped out of them the brass strip always warps, stress release and a bend forced by the punch, but could K's grasp this simple mechanical point?...No....

 

Modern brass etched sideframes do not suffer this. The thinner etched types can be assembled on screwed frame spacers, but you will have to make them yours self due to the thin frame they are longer. Soldered in frame plates are the norm now, but are a pain to adjust and keep square and depend on soldering skills, which screw in ones do not, and you can take things apart to get all things lined up and correct with screwed in ones.

 

The warp is easy to cure, given a 4 to 5 inch bench or woodworking vice, the frames are put in bearing on the edge, with packing on the cupped side in the centre, and the vice tightened till they are dead straight. Test against a steel rule or glass plate, and then turn to the spacers, either new longer ones or simply pack out with washers to get the frame out to just short of the back to back distance. EM would need 16.5 back to back, and really new spacers to increase this far..

 

The Varney spring wire buttons are simply screws tapped into holes, with an under sized washer to provide a "groove" for the wire to keep it in place. 10BA will do or 8 BA, with a drilled out 14 BA or 12 BA washer, as long as it's smaller than the head.

 

You can leave the washer out, but you will have to loctite the screw in to the threaded hole, just short of tight, leaving a gap under the head. The position is half way between the wheels and just below the top line of the wire running over the bearings, they should be about 1.5 mm lower, so that as the axle bearing moves up the slot the wire deflects. The position is not too critical as the tension can be adjusted.

 

This is similar to CSB suspension, but far easier to fit and you can adjust in use. You could off curse add this wire to a dead scale hornblock and bearing frame, but this chassis is a simpler K's type, typical of thousands made over the years from many makers, and it is far more likely that older locos would be candidates for conversion than modern ones, whose designers may have supplied springing in the kit design.

more coming soon,

Stephen..

[bertiedog]

Shows path of wire from adjuster at front to coil spring at back, for this loco the coil will be wound from the guitar wire, left solid with it, with a loop at the end to secure it to the frame.

[bertiedog]

There is plenty of space for a motor and flywheel, modern Canon or Mashima, with the gearbox as a unit with the motor via a subframe, pivoted at the rear, or a chassis mounted motor and a small universal joint at the front, to allow the axle, gear and worm to move against the frames. If a coreless type is used, then the joint is a must to prevent end thrust being taken by the motor. A torque wire would be attached to the gear frame and attached to the chassis. (Not needed with a unit motor and gearbox)..

[bertiedog]

The parts retrieved from the Keyser chassis, note the gap when the frames touch at each end, they are banana shaped, but fully correctable. Quite why k's failed to deal with this was astonishing, especially as so many people like me who made masters for them pointed it out!! It ruined many a model, and strained peoples patience having to put it right.

 

 

 

 

Oddly of course it does not affect a 4 coupled chassis much, but it should never have been done that way, the frames should have gone through second operator fettling, testing, and examination, before selling them.

 

This K's example has had attention to fitting a decent shim bronze plate to the cast keeper, which will be retained, even after the frame widening. The buttons for the springing will be fitted in 10BA tapped holes,and the front spacer altered to take the adjusters for the guitar wire springs..

 

A new rear spacer will be added at the end of the narrow frame section to secure the springs to.

 

These older frames are far more amenable to changes and improvements than modern etched ones and can be as detailed, but far, far stronger, and you can take them apart!

[ozzyo]

I will go along with most if not all that has been said about springing. The way that I do it is to have the two outer axles ridding against the fixed stops (screws) but able to be pushed down in to hollows, and the center axles able to go up about 25 thou. This works well for me in O gauge.

 

On tenders I use two methods. One has a cradle for the front two axles, see below.

The tube to the left will be cut as the one on the right, before fitting the center tube is also split, this may give 5 point suspension. But it works and woks well. this one is set up for split axle pick-up.

 

The second method is to spring the front two axles, see below.

This one was using one side live on the tender and the other side live on the loco, so I wanted to keep the tender body separate (electrically) from the tender chassis.

 

I think that this is the same chassis with all the bits on.

 

OzzyO.

[Buhar]

That Varney is a good representation of a floating motor, the only attachment for the motor was a shouldered screw underneath at the back on which the motor pivoted.

 

Stephen.

 

Sorry Stephen, I'm struggling to get this, possibly having confused myself over the past several months trying to work out a method on my own.

 

So the motor/gearbox is located by the gearbox bearings on the driven axle and then secured at a single point at the rear of the motor in a way that allows the drive system to pivot up and down a little on this fixing, to rotate a little, and to do both at once. So we're after something like a fine countersunk screw where the V shape of the head allows that movement. The bearings in the hornguides would prevent any tendancy to twist side to side.

 

Edited to try to use the right words!

[bertiedog]

The Varney screw simply went up into the motor block, and screwed tight which left the head clear ! Nothing complex is needed, just a restraint from it wandering about, torque reaction is not high enough to raise the motor anyway. Some Super Pacific's had a spring on the screw, but this was simply not needed, and mine runs with the screw out!

 

 

It is firmly held by bearings in the gearbox, originally Lindsay specified ball races, and costs overtook the design by the 1950's and plain bearings were used in later models. The motor was ball raced on the armature, a single ball at each end, one adjustable like the Hornby Ringfield, which shared the design in lots of ways.

 

The driven axle on the Varney has two sleeve bearings, one each side, and bearings in the walls of the gearbox. I fact this is un-needed, as the motor bearings could act as the sleeve bearings as well, but it would be more difficult to disassemble .

 

The Wheels are retained by the keepers, including the driven axle, which when it drops, followed by the nose of the motor, is then twisted at 90 degrees and comes out of the top, (with wheels removed).

 

With modern motors they can be un screwed from the mount to take apart, from the gearbox, and the gear box drop with the wheels still on the axle..

[Horsetan]

Did the Varney drivetrains ever use bevel or crown-and-pinion gears?

 

 

----> Loads of Varney service sheets here

[flubrush]

It was 1948 when produced, long after the war,..... the 1945 reference was to an article in the US model press, even in the UK a full model press ran throughout the war.and UK makers were waiting to resume production only to be stopped in the UK by Board of Trade rulings that forbade new model production till about 1950/51.

 

 

Despite knowing of the US designs, the UK makers cut costs or decided they knew best, which drove Hornby to some odd designs.which became too expensive to make. Even Gordon Varney got caught with costs, but the demise was due to his retirement., and Japanese made brass locos took up springing across the board in the 1960's....in the UK there were none.......

 

I think you might be glossing over the economic situation at the time. Even if Hornby or whoever had brought out a locomotive with full suspension, would there have been anyone willing or able to pay for it? Our RTR manufacturers were producing for a juvenile market and their price had to be aimed at what people would pay in that market, and that would have reflected back directly on the costs of manufacture. You state that Varney got caught with costs and that is probably not a surprise. Producing chassis to the Varney specification would not have been cheap.

 

I remember looking at Japanese brass H0 locomotives in Bill Eaglesham's shop in Cumbernauld in the 1960s and admiring the quality and the sprung chassis. But the prices were way out of my league. I can't remember exactly what they were, but probably a multiple of my monthly salary at the time, so definitiely not produced for your average modeller.

 

When etched kits started in the UK the designs tended towards the complex when springing was fitted, Varney's design seemed to have escaped notice.

 

It applies equally to the use of scale horn blocks and hornways by the way, and works in very fine scale chassis, it does not foul brakes etc, and suits plate framed locos like most British outlines, and it is completely hidden from view., the same as the CSB system., which is a version of the same idea, but based on compensation ideas as well.

 

I suspect that modellers were more influenced by Mike Sharman's Flexichas principles since my experience in the 1970s and 1980s was to build compensated chassis, rather than sprung chassis. In fact, I was more influenced by other modellers who had been applying some form of compensation before Mike Sharman published his ideas. I did try apringing using Alan Gibson axleboxes and coil springs with limited success and dropped the use due to the difficulty of adjustment (swapping Alan's springs out with N scale coupler springs was one attempt at adjustment ). I think we were probably influenced by the practices in larger, live steam scales where springing close to protoype methods was normally fitted. Quite when springing by wire came along, I'm not sure, but it has been a welcome development and achieves what Varney achieved but with less complexity. If the chassis is designed properly, adjustment by replacement of the CSB with a wire of a different gauge should be a quick and easy operation.

 

Another thought might be that you could dispense with the springs in the Varney method if the wire itself had elasticity - maybe mono-filament fishing line?

 

BTW, there was an article in the Sept/Oct 1962 MRN by a Mr. Jamal describing the construction of a sprung chassis very much along the lines of the Varney methods, except that he only spung the outer axles of an 0-6-0 chassis using fine Bowden cable. These were tensioned by two vertical springs attached to the cables by bell cranks. The chassis was for a diesel so the vertical springs could be accommodated within the superstructure. The motor and gearbox were nose hung on the centre axle, so a proportion of that weight provided the downward forces on that axle.

 

Jim.

[bertiedog]

The only part of Varney's design I was advocating was the tensioned wire suspension, note, tensioned, as that's the difference with CSB, which is not tensioned and depends on the wire diameter to adjust it., with quite complex calculation, and a wide availability of wire diameters to work. Because locos don't vary that much in weight, people get away with compromises a lot in CSB, thinner for light, thicker for heavy!

.

The Varney method does not even require a particular wire diameter, Guitar wire at 14 thou is all that is usually needed, plus a small coil spring, which can usually be wound from the same wire, 20 thou would be better for a bigger loco, it is the adjustment t being available that makes the vital difference. Sometimes the coil spring can be dispensed with on heavy locos, the spring movement is only 1mm. A hair spring can be used, or a leaf spring.made from phosphor bronze shim

 

There's no point in using anything more complex, monofilement might work, but would need experiment, and for what advantage?

 

The layout of the wire is simplicity itself, unlike CSB, even the pivot heights do not matter that much, as I said it is adjustable.

The wire does not have to be straight, and can wind up and down to get around frame spacers etc within reason., quite unlike CSB

 

Gordon Varney had the first dedicated factories making Model Railroad equipment, and many designs went through his hands, Some were good, some bad, some awful, (aero train), and he got caught up in the post war economic problems, this is why the expensive sprung versions had a cheaper copy with a plain chassis.

 

I don't think they used contrate gears, but did use spur on diesels, most of the steamers were worm drive, at first with his own design motor, he was one of the first to use 12 volts, or post war designed by Robert Lindsay, who supplied the expensive "super" motors. Later Pittman supplied motors as had Mantua pre war..

 

Varney wrote many articles, pamphlets, and catalogue talks, outlining HO, (and American 00 (19mm)), but he came into the business later in life, and retired during the mid 1950's, and the later Varney products were poor in design due to cost cutting. Lindsay also retired, and the better designs they made faded before the onrush of cheaper Japanese brass locos....and these were cheap for the quality offered.

Stephen.

[JeffB]

Stephen,

 

Thanks so much for this... Very informative. Being a relatively young "Yank", I didn't know about Varney's early efforts at springing (I was born in 1966). I recall reading an article in a old Model Railroader, where the individual built a fully equalized HO scale 2-8-2 mechanism (rigid beam, no springs). This was sometime in the 1950's (I bought a collection of old MR's at a local shop back in the late 1980's). I hadn't realized that CSB, or something like it had been done even before that, and that it had been done in mass produced locomotives, is even more interesting. Thanks again for the history lesson.

 

I've been building rigid beam, partially compensated mechanisms for HOn2 (7mm gauge) and HOn30 (9mm gauge) for about 13 years now. I was heavily influenced by Russ Elliott of the P4 Society. I've found that even rigid beam compensated mechanisms run much better than comparable rigid framed mechanisms. In some instances, the difference is night and day.

 

The downside of rigid beam compensation is what I call the "dive and jump"... Even through turnout frogs constructed to fairly tight flangeway clearances (0.031"/0.8mm), the rigid axle will "dive" into the gap at the frog point, then "jump" up onto the frog point itself. This is more prevalent on turnouts with higher frog numbers. I put up with it, because the operational benefits over rigid framed mechanisms are too good to ignore. This condition is most evident on 4 and 6 wheeled mechanisms, where one axle is fixed. On the 8 wheeled diesel mechanical mechanism in the photos below, it is much less noticeable, as all the axles float, with the gearbox and motor also floating. Overall axle movement is set at about 0.030" or +/- 0.015", and this seems to be sufficient for my track, which I take great care to make as good as possible.

 

The photos below show a proof of concept mechanism for a compensated 0-8-0. It features a Mashima 1220 motor, flywheel, and custom 50:1 gearbox, built using NWSL 0.3Mod gears. It runs very smoothly at super slow speeds, and doesn't hesitate thanks to all wheels being solidly on the rails. It pulls like a scalded mule too! The compensation is evident in both photos. The torque arm that stabilizes the motor/gearbox from rotating around the axle, is between the inside frame. The mechanism has a false outside frame. The newer designs I've been working on feature a functional outside frame.

 

The mechanisms are built from laser cut parts (I work with industrial lasers). Mostly 0.015" and 0.020" thick cold rolled steel, and 0.031" and 1mm thick brass.

 

 

 

 

Jeff

[goodmayes]

 

The downside of rigid beam compensation is what I call the "dive and jump"... Even through turnout frogs constructed to fairly tight flangeway clearances (0.031"/0.8mm), the rigid axle will "dive" into the gap at the frog point, then "jump" up onto the frog point itself. This is more prevalent on turnouts with higher frog numbers.

Jeff

 

Beautiful mechanism and metalwork! As far as 'diving", you should review your track and wheel dimensions. The US NMRA publishes standards for most scales, which all rely on the wheel width being twice the frog flangeway. (plus about 10%). Then the wheel is carried across the gap, without dropping, by resting on the wing rail for the duration. Works the same way on the real thing too. And any frog angle.

 

Ted

[JeffB]

Beautiful mechanism and metalwork! As far as 'diving", you should review your track and wheel dimensions. The US NMRA publishes standards for most scales, which all rely on the wheel width being twice the frog flangeway. (plus about 10%). Then the wheel is carried across the gap, without dropping, by resting on the wing rail for the duration. Works the same way on the real thing too. And any frog angle.

 

Ted

 

Thanks Ted...

 

The wheel tread itself is significantly narrower than twice the frog flangeway (which is built to the NMRA N scale standard of 0.031"). I'll have to build a test chassis with wider tread wheelsets to see if that helps. I see the 'diving' more on the longer points (higher frog numbers), because the gap between the frog point and the heel or toe (can't remember what it is) of the frog is longer. I also see it more (much more pronounced) on Peco 009 points, which have pretty generous frog clearances and a very blunt frog point...

 

Jeff

[goodmayes]

You should include the whole wheel width in the 2 x measurement, flange an' all. The NMRA has a brief but good explanation on the "standards" (general) part of their website, www.nmra.org.

 

Ted

[Popopo]

I applied the sprung/CSB approach in my chassis. I can confirm it's perfect!

- ensures contact with rails - adhession and electric pickup

- tolerates a certain level of inacurracy of manufacturing and assembly

 

The basis is a wormgear gearbox fixed in a "pocket" by steel wires.

 

Pictures of my chassis are at http://picasaweb.google.com/pavel.gulich

 

[goodmayes]

Something doesn't look quite right on the 4 wheel bogie. Without seeing more of the rest of the suspension, I suspect most of the weight is carried on the LH axle.

 

Ted

[Popopo]

The supports are symetric. More pictures are here: https://picasaweb.google.com/Pavel.Gulich/4640?authuser=0&feat=directlink

 

 

Another try:

 

[Ian J.]

I need to remember this thread, as I will need to come up with an effective but quick and simple to assemble system for the chassis for my RTR Terrier chassis.

[mogman1969]

amazed !

[goodmayes]

Maybe the wire showing at the front is a pick-up wiper wire?

 

Ted

[Popopo]

The wire at the front and back are the ends of the springy 0.3mm wires - there is a sort of a lock to secure them in position.

 

A 4-8-4T with the CSB applied. It is a chassis for the Czechoslovak 477.0. Wheels are Scalelink, Markits crankpins and Brassmasters hornblocks. The gearbox is of my own design using Ultrascale gears.