Suspending Radials

[Chris Mitton]

Hi all

Has anyone got any views on / experience of CSB suspension for a 2-4-2 loco? It's actually an ex-GER F5 (mostly Gibson kit) - Paul would call it an M15..... as in M fifteen not James Bond's outfit!

As I see it, I've a choice of four strategies:

Treat it as a four-wheeler plus separately sprung radial or pony trucks, as the prototype was;
Treat it as basically an 0-6-2, by hanging the front wheels on extended carriers and giving them lots of side play (basically what I did on my E4), plus a pony/radial truck at the back;
Much the same but in reverse, ie a 2-6-0 with pony truck at the front;
Or dispense with trucks entirely and build it as essentially an 0-8-0. This is probably the easiest to do without radical surgery to the milled frames, but I'm not sure what curves it will go round (mind you, as long as it will negotiate a B6 I'll be happy).

Any views welcome.....
Regards
Chris

[grovenor-2685]

Or dispense with trucks entirely and build it as essentially an 0-8-0.

i think you can safely assume that, if the prototype needed radials, so will you, a B6 is a tight curve in prototype terms. You can cheat with concealed Pony trucks but there are several articles around on how to build radial axleboxes. Neither version should prevent you using one pair of CSBs for all 4 axles.
Not speaking from experience in this case
Keith

[Russ Elliott]

Some thoughts here:

viewtopic.php?f=19&t=1275&p=12834#p12834

[Jol Wilkinson]

LRM do the radial truck from their later LNWR locos as a separate item. It is a fold up etch with 2mm turned bearings and includes two fold up radial guides to fit into a standard 6mm hornblock cut-out. Found at the bottom of this page http://www.scalefour.org/LondonRoadMode ... ssis/lnwr/

These might work if you could make up a csb "carrier" to sit on top of the radial truck and bear down on it, at the same time allowing the truck to slide radially.

Jol

LNWR radial truck.pdf

[nigelcliffe]

These measurements off the Gibson F5 in my work-pile. This is "number 2", with the chassis built by the same member of the Norfolk&Suffolk local group. As "number 1" runs beautifully, I expect the mechanically identical "number 2" will be just as good once it's finished. Number 2 runs OK at present, but is still under-weight as it's not finished.

Construction is split-frame, using 1.6mm double sided PCB for frame stretchers. Wheels look to be Gibson plastic centres with addition of shorting wires from rim to axle. Axles are split in centres (or split in three for the gearbox axle). Gearbox is a multi-stage spur gear, with worm drive to rear coupled axle. Motor is a Mashima in the boiler. We plan to weight it with lead in the water tanks.

The chassis is built without an radial trucks, so essentially it's an 0-8-0. The leading and trailing axles have 1.3mm of horizontal "slide" in their hornblocks. "Number 1" will negotiate the fairly fierce turnouts on Coldfair Green (I think they are B6's, but several have reverses over them which makes it quite challenging).

It's not strictly a "CSB" as there are two spring wires on each side, each connecting one driving wheel and one trailing wheel. The pivot points are U-shaped brackets (look like they may be a small piece of 1/4 inch U-section channel) with the wire going through two holes. The front pivot centre is 17.5mm behind the leading axle. The rear pivot centre is 16.5mm ahead of the trailing axle.


- Nigel

[Will L]

LRM do the radial truck from their later LNWR locos as a separate item. It is a fold up etch with 2mm turned bearings and includes two fold up radial guides to fit into a standard 6mm hornblock cut-out. Found at the bottom of this page http://www.scalefour.org/LondonRoadMode ... ssis/lnwr/

These might work if you could make up a CSB "carrier" to sit on top of the radial truck and bear down on it, at the same time allowing the truck to slide radially.

Thanks for pointing that out Jol, I too have a couple of GER 2-4-2s to do and that looks just the job. As the result of your last post I am in the process of investing in a LMR J68/69 kit, I think I'll add some of these to that order.

I've been thinking about CSB/sprung solutions for a 2-4-2. and I think I would tend to go for something like.

csb draw 13 2-4-2.jpg

The fulcrums to be set so that the static deflection on all axle boxes should be 0.5mm (although you would have to accept that it could be difficult to guarantee you got it exactly right),then try wires on the separate outer sections several sizes smaller than the main wires on the driving wheels on the front and back axles to reduce the weight carried on these axles as much as possible without sacrificing its ability to stay on the track. I think a reasonable aim to get 70% to 80% of the loco weight on the driving axles. The loco CofG will need to be dead centre over the driving wheels of course, easy on a gobbler with nice big side tanks

Then if you fix the CSB fulcrums on the radial truck so their centres are set slightly closer together than the distance between the fixed fulcrum points on the chassis frames, as shown exaggerated on this drawing...

csb draw 14 2-4-2.jpg

....you should get a spring control self centre effect as a bonus.

Will

[Horsetan]

Could be used for 0-6-2Ts as well, by the looks of things.

[Chris Mitton]

Thanks for all your very helpful suggestions -

My initial aspiration was for radial trucks fore and aft, for the reason Keith (and I dare say Mr Holden) identified, but didn't have a clue how my limited engineering skills could concoct such a beast - then along came Jol:

LRM do the radial truck from their later LNWR locos as a separate item. It is a fold up etch with 2mm turned bearings and includes two fold up radial guides to fit into a standard 6mm hornblock cut-out. Found at the bottom of this page http://www.scalefour.org/LondonRoadMode ... ssis/lnwr/

These might work if you could make up a csb "carrier" to sit on top of the radial truck and bear down on it, at the same time allowing the truck to slide radially.

Manna from heaven!

Next thought was to hang the radial trucks from the single beam on each side, somehow allowing for its side movement: maybe the beam could double as a side control spring, but it would have to be angled in to stop the support colliding with the frame and thus restricting movement.

But on reflection I like Will's solution as the most elegant . It gets round the height difference between the leading and driving axles; it allows the trucks to swing and thus do their job; and allows for a more sensible weight distribution. (I'd already twigged about the possibility of filling the tanks with solid lead, eleven times heavier than water!)

So I think that's more or less what I'll do - eventually! I'll order a couple of radials (OK so they're LNW, but out of sight so what?), and hope for the best that Jol also supplies copious quantities of Round Tuits......

Thanks again to all,
Regards
Chris

[Jol Wilkinson]

Chris,

pleased to be of help to both you and John Redrup of London Road Models. One word of caution, although not specific to LRM radial trucks.

I have found that with pony trucks and radial trucks care is needed with the amount of "side force" in relation to the vertical loading. It is easy to overcome the resistance provided by the wheel flanges, so you may have to consider giving the radial truck a bit less lateral force.

As for Round Tuits, what we lack is a consistent set of standards for them. As this is the S4Society, surely somebody can work out a specification.
What is the correct unit for a RT? Should they be available in liquid, gaseous or solid (chocolate coated) form? Should they carry a health warning and be regulated by the committee?

Jol

[Russ Elliott]

I share Jol's qualms about the lack of separation between vertical and side force in Will's suggested 'combined' pony truck arrangement, and I suspect it will prove too difficult to set up to satisfy both directions. I think it will be easier to provide a separate side control spring, e.g. something like this, whose strength can be changed to optimise the steering.

[Will L]

I share Jol's qualms about the lack of separation between vertical and side force in Will's suggested 'combined' pony truck arrangement, and I suspect it will prove too difficult to set up to satisfy both directions.

On mature reflection I think you and Jol are right. I did spend an hour trying to defend my idea but I lost when it occurred to me that the maximum sideways deflection of the radial truck would be comparable with, if not greater than than, the upward deflection under the loco's weight. I also needed to remember we were talking about a loco with one of these at both ends!

Having come to that realisation, I now think that any form of captive fulcrums on the radial truck will have the same problem, so a bar fulcrum along the top of the radial, allowing it to slide side to side under the spring wire, is probably the way to go. At that point I expecting that friction will do all the steering we need, but the LRM radial truck comes with an eye in the middle for a steering spring as Russ suggested should anybody feel the need.

I guess we will only really know the truth when somebody has tried it, so, about those chocolate coated RTs you were mentioned Jol....

Will

[John Bateson]

Did the original F4/F5/F6 have a radial truck or were they designed essentially as 0-8-0s (as supplied by Gibsons). This cropped up in discussion at a recent CAG meeting and I have to admit that I don't really know.
The F6 I built so many years ago certainly has problems on curves and has had all sorts of squidging to the front and rear.
John

[dcockling]

Did the original F4/F5/F6 have a radial truck or were they designed essentially as 0-8-0s (as supplied by Gibsons).

Hi John,

So far as I'm aware there is no facility in the Gbson kits F4/F5/F6 or F7 for the the front or rear carrying wheels to be sprung or compensated, the kits didn't contain any etches to create radial boxes or even pony trucks and they are 'designed' to be built as 0-8-0s.

The Original i.e. the real GER M15, M15R, G69 and Y65 2-4-2 tanks were all radials, leading and trailing, whereas the larger C32 (LNER F3) tanks did not have radial axle boxes; but Gibson never did a kit for those.

All the Best
Danny

[Russ Elliott]

Owing to our model curves, it's probably better to build these things as though they were radials.

[John Bateson]

Russ and Danny
Thanks - I can feel another project coming on - the F6 has had more changes than a 6 month old!
John

[Will L]

Did the original F4/F5/F6 have a radial truck or were they designed essentially as 0-8-0s (as supplied by Gibsons). This cropped up in discussion at a recent CAG meeting

Did it, I can't have been listening.

GER 2-4-2 tanks. LNER classes F3 to F7.

All except the F3s had radial trucks at both ends, the F3s had no radial trucks at all.

The original F4 design was built first by T W Worsdell who was from Crewe, so fitting LRMs LNWR radial truck isn't to far from prototypical.

The F3s were designed built later by J Holden and just had a lot of free play on the carrying axles which had in both inside and outside bearings. This was a tank version of the E4 2-4-0 tender loco which had developed from assorted other 2-4-0 and 2-2-2 tender loco's

The F4/5/6's were all variations on a theme. A few F4 were built first but didn't work very well, acquiring the nickname Gobblers due to the appetite for coal. Stratford then built the F3s. Then they fixed the F4, by changing the valve gear and built a lot more F4 then F5s and F6's. F4s had 160 lb boliers, F5s had 180 lb boilers but were otherwise identical to the F4s. The F6s are F5s with a rather more commodious cab larger tanks and a slightly smaller bunker, ending several tons heavier.

The F7 were the same basic radial tank idea built on an all together smaller scale, except in as far as the got the commodious cab.

Will

P.S sorry Danny didn't notice you got there first. I'll have to laern to type quicker.

[dcockling]

P.S sorry Danny didn't notice you got there first. I'll have to laern to type quicker.

Hi Will, it's always good to hear from another true (ultramarine blue) believer

All the Best
Danny

[Great Westen Man]

Will have to try out the settings for the CSB springs when the test etch that is on order comes for the new Cooper Craft F3 chassis as it will be built in S4 to test it out fully.

[Will L]

Will have to try out the settings for the CSB springs when the test etch that is on order comes for the new Cooper Craft F3 chassis as it will be built in S4 to test it out fully.

Do keep us informed, it could be very interesting.

Will