Springing a front bogie

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steve howe
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Springing a front bogie

Postby steve howe » Sat Aug 06, 2022 2:05 pm

One of the locomotives in the Watermouth collection is a rather nice 'Grange'. 'Bucklebury Grange' was built by Pat English shortly after the kit was released.
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IMG_20220805_194308630.jpg (72.48 KiB) Viewed 1141 times

Although fully compensated over the drivers, Pat built it as a basic 0-6-0 with all the weight being carried on the driving wheels with the front bogie just "going along for the ride" I have subsequently fitted current collectors to the tender which has improved the loco's reliability no end, but the front bogie occasionally gives trouble on certain points. I know the classic solution is to add some lead to the bogie top, but I believe current wisdom prefers leading bogies to have some modicum of springing to share some of the weight and keep all wheels firmly on the rails. I'd be interested to know how this is done without compromising the swing of the bogie?

Steve

davebradwell
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Re: Springing a front bogie

Postby davebradwell » Sat Aug 06, 2022 3:49 pm

i've always followed the arrangement used on full size. Across the bottom of the loco frames between the bogie wheels is a plate and there is a corresponding plate across the top of the bogie frames to form a slide. The axles run in slots in the bogie frames (or can have proper hornblocks, of coourse) and there is a single spring each side bearing on the axles (or axleboxes) with a centre bearer attached to the frames. Load on bogie determined by initial deflection of these springs. Should add axles run in centre of frame slots so they can rise and fall.

Your question puzzles me - as this arrangement copies general prototype practice, there is nothing that impedes bogie movement more than in the original. The only change might be if you've done something to your model to increase movement. The springing only adds a slide and the wheels will hit something like the frame cut-outs or drain cocks as a limit.

4-6-0s can be front heavy and propping the front up with a sprung bogie can actually help the trailing drivers stay on course when going astern.

DaveB

David Knight
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Re: Springing a front bogie

Postby David Knight » Sat Aug 06, 2022 5:15 pm

You might find this useful, http://www.clag.org.uk/class2p-bill.html
Further details are available here- viewtopic.php?f=29&t=8217#p92654

Cheers,

David

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Will L
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Re: Springing a front bogie

Postby Will L » Mon Aug 08, 2022 9:26 am

steve howe wrote:...
Although fully compensated over the drivers, Pat built it as a basic 0-6-0 with all the weight being carried on the driving wheels with the front bogie just "going along for the ride" I have subsequently fitted current collectors to the tender which has improved the loco's reliability no end, but the front bogie occasionally gives trouble on certain points. I know the classic solution is to add some lead to the bogie top, but I believe current wisdom prefers leading bogies to have some modicum of springing to share some of the weight and keep all wheels firmly on the rails.

While I would strongly advocate that our model locos should be sprung as this improves their performance, the nature of the springing we need to get good performance from our loco differs from that fitted to then real thing, as the physics of the thing if affected by the 3rd power (cube) of the scaling factor.

The question you have to ask yourself is why your doing it.

If it pleases you to want to model your models so its chassis conforms as closely as possible to the prototype arrangements then yes you probably want to replicate the bogie support and side control arrangements as Dave suggests. But beware the relative forces which springs deliver mean that what on the prototype is a beefy multiple layer leaf spring, on your model will be a fine price of spring wire. Getting the balance of your springing right can require a fair bit of skill and judgment.

If your loco runs nicely and you just want to ensure your bogie doesn't fall off at corners a bit of weight on the bogie frame will probably do nicely.

davebradwell
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Re: Springing a front bogie

Postby davebradwell » Mon Aug 08, 2022 10:15 am

I never mentioned side control - a whole can of worms in itself.

DaveB

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steve howe
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Re: Springing a front bogie

Postby steve howe » Mon Aug 08, 2022 12:49 pm

Thanks for the useful info chaps, as the main objective is to keep the wheels on the rails, I'll try Will's suggestion first before I embark on small scale engineering!

Cheers

Steve

Philip Hall
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Re: Springing a front bogie

Postby Philip Hall » Mon Aug 08, 2022 2:26 pm

I have just converted a Mitchell 44xx from 00 to EM and the builder (unknown) had put a small slug of lead on top of the leading and trailing trucks and it seems to run fine. As Will says, leave it alone and I'm also with Dave and the can of worms that is side control!

My main problem with the 44 was that the builder had used J69 wheels - about the right diameter and number of spokes, but crank in the wrong place and too short a throw - which threw up (sorry!) all sorts of problems with crosshead travel and vacuum pump travel!

Philip

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45609
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Re: Springing a front bogie

Postby 45609 » Mon Aug 08, 2022 10:00 pm

Philip Hall wrote:….and I'm also with Dave and the can of worms that is side control!


Yes, certainly agree with that. All of my experience with side control springing on either my own or trouble shooting on other people’s locos has led me to an empirical conclusion of “don’t bother with it”.

Morgan

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Will L
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Re: Springing a front bogie

Postby Will L » Tue Aug 09, 2022 10:30 am

45609 wrote:...Yes, certainly agree with that. All of my experience with side control springing on either my own or trouble shooting on other people’s locos has led me to an empirical conclusion of “don’t bother with it”...

As do I, I only brought it up at all because when Ive tried to suggest that it is likely to cause more problems than it solves in the past it has proved contentious, particularly when people start trying to replicate on the model the prototypical structure of bogies and pony trucks.

Then again locos with long overhangs back or front (typically 0-4-4 and 4-4-0 prototypes) do need something, although my personal preference would be a fixed weight carrying bogie pivot and side play on the driving axle next to the bogie.

Philip Hall
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Re: Springing a front bogie

Postby Philip Hall » Tue Aug 09, 2022 3:18 pm

I should say that I have had some success with bogies on a 4-4-0 and a 0-4-4T in that the bogie is taking some of the weight. There is the usual slot in the chassis bogie mounting which enables the bogie to drift from side to side around the bends, but it seems that the slight resistance to movement provides a degree of side control to stop the engine yawing about as it enters the curves.

My curves are 4'6" minimum, which helps no end, but I should perhaps be a bit reluctant to admit that all of these engines so far have been RTR conversions; Bachmann Dukedog/City and a Hornby M7. The principle, even without any suspension, clearly works. Yawing about also depends to a large extent on perfectly concentric and wobble free wheels, but I've banged on about this before...

Philip

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Julian Roberts
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Re: Springing a front bogie

Postby Julian Roberts » Tue Aug 09, 2022 5:55 pm

Would not Dave B's sliding bogie attachment impart some simple side control? My three 4-4-0 or 0-4-4s rest on a roller on top of the bogie and I've always thought even that fairly frictionless connection must impart a modicum of side control.

If the bogie is pivoted to the loco nearer the driving wheels with a fixed arm the amount the loco is steered can be reduced according to where the pivot is placed. Don't know if any of this would be useful in 4-6-x context as unlike my locos it seems you don't need weight on the bogie other than enough to keep it on the rails.

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Jol Wilkinson
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Re: Springing a front bogie

Postby Jol Wilkinson » Wed Aug 10, 2022 7:22 am

London Road Models have a LNWR sprung bogie in their range, designed for the LNWR 4-4-0 locos. This is 25mm wheelbase and although is of the standard LNWR design with outside compensating beam and spring, might be adapted for other locos with the same bogie wheelbase. The design has worked satisfactorily and was introduced as a separate item following requests from modellers who had built the kits of which it was a part. The same concept was also used in the LRM NER G1 class 4-4-0.

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Horsetan
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Re: Springing a front bogie

Postby Horsetan » Mon Aug 15, 2022 9:46 pm

Jol Wilkinson wrote:London Road Models have a LNWR sprung bogie in their range, designed for the LNWR 4-4-0 locos. This is 25mm wheelbase and although is of the standard LNWR design with outside compensating beam and spring, might be adapted for other locos with the same bogie wheelbase. The design has worked satisfactorily and was introduced as a separate item following requests from modellers who had built the kits of which it was a part. ....


Would there be any possibility of adapting it for different wheelbases?
That would be an ecumenical matter.

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Jol Wilkinson
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Re: Springing a front bogie

Postby Jol Wilkinson » Tue Aug 16, 2022 7:43 am

The etched bogie side frames don't have any length "adjustment". Originally designed for the LRM LNWR Jubilee kit and subsequently used in the Renown and Precursor Tank kits, the bogie was made available as a separate item following request from a number of LRM's customers.

The same concept was use in the NER G1 4-4-0 kit, with 26mm bogie , wheelbase but was not produces as a separate item.


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