CSB for a Single Driver

David Knight
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Re: CSB for a Single Driver

Postby David Knight » Mon Oct 12, 2020 1:03 am

Horsetan wrote:None of your ".tif" files are visible here, unfortunately.

FWIW they do open with "preview" on a Mac.

Cheers,

David

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Will L
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Re: CSB for a Single Driver

Postby Will L » Mon Oct 12, 2020 10:28 am

Michael Waldron wrote:Well, I do have several singles to build!
Thought you might like to see the actual prototypes!
One is already built, though the chassis is not yet fitted with its motor - the unique no203 ‘Sussex’.
203-Sussex-a 2.jpg

Then three or four other singles - the small cylindered 325 ‘Abergavenny’, the large 326 ‘Grosvenor’, and two ‘production G singles 327 ‘Imberhorne’ and 336 ‘Connaught’ !
325-Abergavenny-f.jpg

151-Grosvenor-a.jpg

Grosvenor with early tender, later replaced by the same as Imberhorne.
Connaught looks the same as Imberhorne
327-Imberhorne-c.jpg


Mike


Their visible now.
Seems you have a fine opertunity to experiment with whichever approach you chose. Shouldn't need more than a couple of goes to get something your happy with. But lets not overcomplicate, we do have to remember that these loco's dealt with small light trains so its quite possible that on a flat layout an even weight distribution (i.e.33.3% per axle) will probably be enough. Somewhere in my past I had an LNER steam rail car made of white meat and which weighed an absolve ton, It was driven by a single axle and was even capable of pulling a tail load of a few waggons.

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Will L
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Re: CSB for a Single Driver

Postby Will L » Mon Oct 12, 2020 11:41 am

Ok I know I suggested not complicating things but...
davebradwell wrote:I wasn't thinking of anything non-linear, WillL just fiddling with the rate of the springs. In your csb all springs are deflected the same amount (-ish as axlebox may not co-incide with point of greatest deflection) so you can only increase the load by shortening the span of a spring which also increases its rate. By moving the fulcrum points downwards you can increase the load without increasing the rate (stiffness) - you're deflecting it more. It just sounded more straightforward than getting the anti-roll bars to work, never mind fitting them in.

Ok yes I do see what your getting at. Unfortunately the whole ideas of trying to do this with a single springy beam each side drives a coach and horses through the design methodology (those spread sheets) which is intended to allows a relativity simple way to design in a particular chassis performance without the need for an adjustment phase to get the required results. I assume it could be done with individual springs on each axles using the sort of spring system you provide, Dave, but I think some fairly precise modelling would be required and I'd want to calculate the required fulcrum point heights and spring lengths and draw/etch out the result so its accurate rather than try and build one from scratch.
My 200mph Tri-ang stretch-Caley single would tip on its nose during harsh braking so definitely something to watch with compensation. I bet a Lord of the Isles behaved the same.

But surely the Tri-ang Caley single (and the Lord of the Isles) had a bogie which didn't carry weight so wouldn't prevent any pitch forward (until something came into contact with the bogie). I still think an all axle compensated chassis won't do it.

Michael Waldron
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Re: CSB for a Single Driver

Postby Michael Waldron » Mon Oct 12, 2020 7:17 pm

That’s odd because I can see them!

Michael Waldron
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Re: CSB for a Single Driver

Postby Michael Waldron » Mon Oct 12, 2020 8:09 pm

Just by the by:

Axle weights for the Stroudley singles were as follows:-

Grosvenor: Leading axle 12tons. Driving axle 15 tons. Trailing axles 10 tons. Not quite equal.
Abergavenny: 11t 6cwt. 15t 0cwt 7t 18cwt
Production G: 12t 0cwt 13t 10cwt. 7t 18cwt
Sussex: 11t 2cwt. 14t 7cwt. 10t 0cwt.

Mike

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Will L
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Re: CSB for a Single Driver

Postby Will L » Mon Oct 12, 2020 9:12 pm

Michael Waldron wrote:Just by the by:

Axle weights for the Stroudley singles were as follows:-

Grosvenor: Leading axle 12tons. Driving axle 15 tons. Trailing axles 10 tons. Not quite equal.
Abergavenny: 11t 6cwt. 15t 0cwt 7t 18cwt
Production G: 12t 0cwt. 13t 10cwt. 7t 18cwt
Sussex: 11t 2cwt. 14t 7cwt. 10t 0cwt.

Mike

These are all close enough to a 30-40-30% weight distribution as I original suggested. Abergavenny is the outlier with 44% on the middle axle. I suspect that an attempt to reproduce these exact weight distributions would not produce a significantly different CSB plot or a better performing model.

They all have have a more weight on the front axle and less on the rear axle. This shows that the true loco CofG will be a little in front of the driving wheel. The model could be better balanced. It also makes one wonder if they found the connection to the tender was producing a little more stability at that end.

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Horsetan
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Re: CSB for a Single Driver

Postby Horsetan » Mon Oct 12, 2020 11:21 pm

David Knight wrote:
Horsetan wrote:None of your ".tif" files are visible here, unfortunately.

FWIW they do open with "preview" on a Mac.


Some of us don't use Macs.
That would be an ecumenical matter.

Stephan.wintner
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Re: CSB for a Single Driver

Postby Stephan.wintner » Tue Oct 13, 2020 2:02 am

Will L wrote: It also makes one wonder if they found the connection to the tender was producing a little more stability at that end.


I'm wondering if they were trying to balance out the weight transfer when pulling. It should tend to transfer fore to aft and even out the leading and trailing axles.

Stephan

andrewnummelin
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Re: CSB for a Single Driver

Postby andrewnummelin » Tue Oct 13, 2020 6:49 pm

I came across this whilst looking for something totally different but I thought it might be of some interest or amusement. It's not about CSBs but on the stability of single wheelers and is from Clark's "Railway Machinery" of 1855. His discussion may well give modellers some things to think about concerning track holding.
Clark p 195.jpg
Regards,

Andrew Nummelin

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Will L
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Re: CSB for a Single Driver

Postby Will L » Tue Oct 13, 2020 7:12 pm

Clearly agrees with Julian's view that you need to ensure plenty of weight on the front axle.

Michael Waldron
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Re: CSB for a Single Driver

Postby Michael Waldron » Wed Oct 14, 2020 7:54 am

Will I’ve tried to send a PM, but not sure if it actually sent.
Mike

andrewnummelin
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Re: CSB for a Single Driver

Postby andrewnummelin » Wed Oct 14, 2020 8:05 am

Will L wrote:Clearly agrees with Julian's view that you need to ensure plenty of weight on the front axle.

Most locos don’t spend all their time going in one direction...
Moveable c-of-g???????????
Regards,

Andrew Nummelin

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Will L
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Re: CSB for a Single Driver

Postby Will L » Wed Oct 14, 2020 9:56 am

Michael Waldron wrote:Will I’ve tried to send a PM, but not sure if it actually sent.
Mike

Sorry Mike I've received nothing. You could try the email option?

Michael Waldron
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Re: CSB for a Single Driver

Postby Michael Waldron » Wed Oct 14, 2020 10:49 am

I couldn’t get your name to stay in the box.
Must have been a glitch in the system this morning.
M

Michael Waldron
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Re: CSB for a Single Driver

Postby Michael Waldron » Wed Oct 14, 2020 12:07 pm

Tried once more then email.
M

Michael Waldron
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Re: CSB for a Single Driver

Postby Michael Waldron » Sun Nov 01, 2020 12:18 pm

Jeremy Suter wrote:Been watching this thread carefully I have already rebuilt the chassis on my GCR 422 Single.

When I built it many years ago I sprung the wheels although not CSB style I used Alan Gibson sprung hornblocks. The basic problem was tractive effort, it struggled to pull the tender. I got round it by changing to a fixed driving axle and rocking the rear axle giving the classic 3 point balance, Then I packed the boiler with weight making it front end heavy and weighting the tender onto the link with the loco to counter balance the boiler putting all the body weight onto the driving axle which I think gives the best tractive effort for a single.

The tender has a fixed rear axle with a beam compensation on the other two which are lightly sprung aswell

My problem now is that the front bogie needs to be rebuilt to make it heavy enough to stay on the rails and not affect the body weight which it did when the chassis was sprung.

What I am really saying is that I needed to get all the body weight over the driving axle

If I redo it again with the CSB style I would spring only allowing it to go down not up as in effect I'm driving an 022 with a loose 040 truck pushed along in front

IMG_5773 (3).JPG
Please could you elaborate on your thinking regarding weighing the axle? I’m not sure I quite follow what you’re saying in your final paragraph.
Thanks
Mike.

I made a small bucket of lead to go under the driving axle and gear box to give more un-sprung weight to that axle its still there and can be seen between the spokes.


What can it pull now, Jeremy? I forgot to ask when you posted this.
Mike

Jeremy Suter
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Re: CSB for a Single Driver

Postby Jeremy Suter » Tue Nov 03, 2020 9:56 pm

Hi Mike
The Loco now pulls the tender and 5 bogie coaches at least will take a film of it when I put the coaches back together after I finish painting and doing the interiors.

Jeremy Suter
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Re: CSB for a Single Driver

Postby Jeremy Suter » Thu Nov 12, 2020 9:43 pm

Hi Mike

Just been playing with the single wheeler and been running it with 5 bogie coaches weighing about 225 grams each. Its only an end to end layout so can't run the train very far. There is a little bit of wheel slip but I probably have 95+% of the body weight on the driving axle. There must be some on the rear axle but nothing on the front bogie which has its own weight, just a brass block for now until I rebuild the bogie altogether. The loco and tender weigh 460 grams total and the loco on its own is 320 grams.

Video of it here.
https://www.youtube.com/watch?v=TDPm5w1 ... e=youtu.be

The wheels may have been smoothed a little over the years with slipping before I changed the design. and it does have to pull the tender as well.

Interestingly I have a Pannier tank weighing 130grams (waiting more weight to be added. ) That is approx. 44 grams per axle and although struggles it stops rather than slips but it will move the train. This show its not just weight to axle ratio but the number of axles to the total body weight.

IMG_5849.JPG




[youtube]https://www.youtube.com/watch?v=TDPm5w1Gtfw&feature=youtu.be[/youtube]

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Will L
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Re: CSB for a Single Driver

Postby Will L » Thu Nov 12, 2020 11:09 pm

You tube link corrected
Jeremy Suter wrote:

Michael Waldron
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Re: CSB for a Single Driver

Postby Michael Waldron » Mon Nov 30, 2020 5:13 pm

Very impressive Jeremy!

My singles will only be required to pull Roxey Stroudley LBSCR 4/6 wheelers, or Branchlines Billinton 6 wheelers, or a couple of my own Stroudley or Billinton kits (omitted from their ranges).

The Roxey ones have had their horrible inside bearings replaced with my own W irons, and are now pinpoints. The Branchlines ones have been fitted with my own cleminson chassis, not unlike the Brassmasters one.
The layout it not a long one, restricted by the shed size, so the train length will not exceed 8 carriages.... none of them bogie ones!

Mike

Winander
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Re: CSB for a Single Driver

Postby Winander » Sat Jan 16, 2021 1:30 am

Russ Elliot's treatise on suspension in Annex 12 (linked earlier by Will) discusses the effect of drawbar pull is that it shifts the centre of gravity. He suggests that for a tender locomotive which will invariably run with a load to the rear, the centre of gravity can be moved forward by an amount dependent on the relationship between the weight of the loco and its load, such that it is shifted to the optimum position by the drawbar pull. He concludes by stating "style of calculation is the same for any number of axles" [my emphasis].

I don't know if he contemplated a single when he made that statement, but would it mitigate pitching of a single to any extent?
Richard Hodgson

Stephan.wintner
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Re: CSB for a Single Driver

Postby Stephan.wintner » Sat Jan 16, 2021 2:00 am

That's a simple question but I don't think the answer is simple.

The position of the cg and the design of the loco suspension define the stationary stance of the loco. (Spring stiffness affects both height and pitch.)

The drawbar force applied to the loco does not care where the the center of gravity is. How the loco responds to that force is down to the spring stiffnesses and suspension arrangements. So the pitching - by which I mean only the difference between stationary and pulling stance - is not affected by CG position.

Perhaps I'm being too much an engineer here, but I would say biasing the CG cannot mitigate pitching. It can affect traction, by helping load the axles in an optimal fashion (or, conversely, suboptimal fashion.) And the effect on the stationary stance will of course also carry over to the pulling stance.

Stephan

davebradwell
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Re: CSB for a Single Driver

Postby davebradwell » Sat Jan 16, 2021 9:23 am

In this case with virtually bugger-all drawbar pull it's not going to do much to the c of g.

Isn't it about time we had a photo of progress so far? With no rods to worry about the chassis should be a quick job.

DaveB

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Will L
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Re: CSB for a Single Driver

Postby Will L » Sat Jan 16, 2021 11:05 am

Stephan.wintner wrote:Perhaps I'm being too much an engineer here....

Absolutely not, to get good results we need to understand what we are doing. Perhaps the only disadvantage of using springing is that this become more true.

davebradwell wrote:In this case with virtually bugger-all drawbar pull it's not going to do much to the c of g.

Isn't it about time we had a photo of progress so far? With no rods to worry about the chassis should be a quick job.

DaveB


I think Dave may have a point. And I too would like to see how your getting on.

Winander
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Re: CSB for a Single Driver

Postby Winander » Sat Jan 16, 2021 11:55 am

Stephan.wintner wrote:It can affect traction, by helping load the axles in an optimal fashion


It is, therefore, worth doing.

I will keep you advised of progress but the parts haven't arrived yet.
Richard Hodgson


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