Suspension design for a 2-4-0, CSB?

[MarkS]

Russ, as you well know, one of the joys of CSB's and H/L gearboxes is that it takes a mere a moment to pull the spring wires, unscrew the motor and drop the wheels(with gearbox).
Which is what I did, although I did pull off the wheels before soldering the swing arm with a dab of (2% silver) electrical solder.
The motor is constrained with my usual 2-sided foam tape on the bottom of the motor and a single sided piece on the top of the motor. When the body is tightened down the foam is just squeezed enough to hold it all in place with no vibration noise.

[David Thorpe]

As I mentioned a little while ago on Paul Willis' blog, I've just embarked on my first P4 loco - an Alan Gibson E4 - and decided, having followed these threads for some months, that CSB is the way to go, using as a basis the High Level gizmos.

I was wondering how you got on with this, Chris. Did you go for CSBs and, if so, how did it all work out? I've built an E4 with Sharmanesque compensation on the loco and CSBs on the tender and it runs well enough though I'm a bit concerned about the occasional wayward behaviour of the pony wheels.

DT

[Chris Mitton]

Hi Davey

I did in fact take a few steps - the frames are built, complete with High level hornblocks, the handrail knobs are in position, gearbox and motor assembled, some of the body (footplate and cab) got built and a couple of pixs got posted on this forum ( http://www.scalefour.org/forum/viewtopic.php?f=20&t=1305#p9067 ).

At that point progress regrettably ground to a halt. I got sidetracked between building a rake of Danny Pinnock's ex-GER coaches, the demands of cardiac rehab and the arrival of two more granddaughters (to make sure they don't fall victim to gender stereotyping, they'll soon be running their first trainsets!).

However your prompt is timely - I did get the E4 out of its box last week to remind myself what comes next, and I've just acquired a variety of guitar strings so I can try out various weight / spring combinations. I'm fairly confident I can get it running with the CSBs eventually, my big reservation is that the final drive gear doesn't have a grubscrew boss so will need securing to the axle. This seems pretty permanent so I'll take a very deep breath before applying the Loctite.

Hopefully, then, I'll have the chassis runnable this side of Christmas - I'll keep you posted. Thanks for the interest!

Regards
Chris

[Paul Willis]

However your prompt is timely - I did get the E4 out of its box last week to remind myself what comes next, and I've just acquired a variety of guitar strings so I can try out various weight / spring combinations. I'm fairly confident I can get it running with the CSBs eventually, my big reservation is that the final drive gear doesn't have a grubscrew boss so will need securing to the axle. This seems pretty permanent so I'll take a very deep breath before applying the Loctite.

Hi Chris,

Good to see you at Scaleforum - you should have brought the E4 along with you

Don't forget that anything that can be stuck can also be undone. Just not necessarily in a way that is re-usable...

scrap 002 (Large).jpg

You may remember from Beer and Buckjumpers that those are the remains of the gearwheel and axle from my Pug when I loctited the gear in the wrong place

But a new axle and gear, and it runs beautifully now

Good luck!
Flymo

[Will L]

Alternatively Loctite can be undone by applying heat. Not enough to unsolder things but you might want to remove the plastic centred wheels and plastic spur gears first. Actuality by the time you've cut the axle with a cutting wheel it was probably hot enough to be slid out of the gearwheel with a gentle tap.

Will

[David Knight]

As an aside, Bill seems to be making progress on his version of the Midland 2-4-0 frame which is now "in preparation". See;

http://www.mousa.biz/frames/lms_loco_frames.html

Cheers,

David

[Russ Elliott]

I was asked a few days ago for a plot for an GER E4 2-4-0. This has a nose-heavy axle weight distribution (thanks, Paul) of 14.25T, 13.75T, 12.5T. The prototype CofG for these static weights is exactly over the leading driver:

continuous-e4-3.png

This weight distribution changes when drawbar pull takes effect. Assuming a typical drawbar pull of 20% of the tractive weight, i.e. in this case approx 13% of the loco weight, the drawbar couple over the 66mm loco wheelbase will lighten the front axle by 2.75% and increase the rear by 2.75%, which gets the drivers into equality on a reasonable length train. This is equivalent to the CofG being shifted a maximum of approx 1.8mm to the rear of the front driver.

The fulcrum positions are determined in the normal way using the asymmetric weights plugged into a Wyatt/Litchfield spreadsheet. Although the distance between the rear driver and the loco rear fallplate is a bit tight (4'3"), there should be sufficient space for the rear fulcrum position in the frame:

continuous-e4-2.png

As a drawbar pull check, plugging in a max 1.8mm CofG shift to the spreadsheet indicated a negligible chassis slope, but a rear driver that was a bit too soft. The outer fulcrum positions were therefore moved in slightly to slacken the front driver, and this seems to give a reasonable compromise setting between the light engine and loaded engine states, although CofG achievement (directly over the front driver) remains fussy. Alan Turner's spreadsheet was very useful at this finessing stage.

continuous-e4-1.png

I'm not convinced a CSB over all the axles of a 2-4-0 or 0-4-2 is a particularly good idea, so the above reflects what what requested of me. Notwithstanding the challenge of accommodating the different height setting of the leading axle hornblock, my personal view remains that a springy equaliser for the two driving axles (see diagram in my post toward the top of this thread) remains a better strategy because the drivers will always be equally loaded regardless of CofG placement and loco direction and chassis horizontality. In either case though, the paucity of space for traction weight makes it a good case for a tender-mounted motor cardanning through to the loco.

[Horsetan]

As an aside, Bill seems to be making progress on his version of the Midland 2-4-0 frame which is now "in preparation". See;

http://www.mousa.biz/frames/lms_loco_frames.html

"Not Found
The requested document was not found on this server.

Web Server at mousa.uk.com"

[grovenor-2685]

Try http://www.mousa.biz/fourmm/loco/frames/lms_loco_frames4.html#mr-1347-class-2-4-0
Keith

[Alan Turner]

Bill's web site has been like that for the last three years.

Alan