CSB and tenders

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Andy W
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CSB and tenders

Postby Andy W » Thu May 17, 2012 10:58 am

I'm sure this topic must have been discussed either here or on the CLAG site, I've searched without success so if it has I'd be grateful if someone could point me in the right direction.

I'm building a couple of 0-6-0s and think it's about time I tried out this CSB business. On a beamed 0-6-0 I'd have a fixed rear axle on the loco with the tender having its rear axle running in top hats and the front two axles sprung/suspended so that extra weight is hung on the rear of the loco.

Am I right in thinking that with CSBs there is no need to do this, and that the loco and tender can be considered as 2 vehicles?

Thanks

Andy
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Russ Elliott
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Re: CSB and tenders

Postby Russ Elliott » Thu May 17, 2012 12:19 pm

Ealing wrote:Am I right in thinking that with CSBs there is no need to do this, and that the loco and tender can be considered as 2 vehicles?

Yes, Andy. Gravity doesn't care what the thing being supported by the axles is called. There is a Will Litchfield thread on this forum addressing a specific tender application using bespoke carriers. I'll dig out the reference if Will doesn't beat me to it. Tender wheelbases are usually symmetrical, so there are a number of plot options on the CLAG CSB page to explore for the symmetricals. A problem area of tenders can be frame length, and in extreme cases, a non-CSB solution might be necessary.

As for hanging tender weight on the back of locos, this is not recommended for 3-axle loco CSB applications. If you feel the need to maximise loco traction, the proper solution is to put the motor in the tender and cardan the drive through to the loco, filling the latter with lead.

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Will L
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Re: CSB and tenders

Postby Will L » Thu May 17, 2012 3:13 pm

Russ Elliott wrote:
Ealing wrote:Am I right in thinking that with CSBs there is no need to do this, and that the loco and tender can be considered as 2 vehicles?

Yes, Andy. Gravity doesn't care what the thing being supported by the axles is called. There is a Will Litchfield thread on this forum addressing a specific tender application using bespoke carriers. I'll dig out the reference if Will doesn't beat me to it.


For a bit of background, start reading from here, you get to the bit about tender chassis about 3 posts down.

Tender wheelbases are usually symmetrical, so there are a number of plot options on the CLAG CSB page to explore for the symmetricals. A problem area of tenders can be frame length, and in extreme cases, a non-CSB solution might be necessary.

Russ likes to keep the CSB as long as possible, but I think you should be able to get a perfectly functional CSB in unless the frame length is actually less than the distance over the wheel rims end to end. Some bogies are of this form and don't really suit CSB.

As for hanging tender weight on the back of locos, this is not recommended for 3-axle loco CSB applications. If you feel the need to maximise loco traction, the proper solution is to put the motor in the tender and cardan the drive through to the loco, filling the latter with lead.


No sprung chassis lends itself to the sort off centre weight distribution wheelbarrow tenders give. A CSB is at its best when the effective loco CofG is central on the chassis and the improved adhesion you get from a properly balanced chassis with even weight distribution out ways any advantage you might get by loading weight on just anywhere. Only if your planning the sort of monster trains that most of us can't fit on a layout anyway, will you need to start worrying tender mounted motors and solid lead boilers!

Will

Philip Hall
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Re: CSB and tenders

Postby Philip Hall » Thu May 17, 2012 5:57 pm

The comments about tender weight being unnecessary with CSBs are interesting. However, my main reason for hanging the tender on the back of an engine is not usually to do with haulage capabilities, although it certainly helps. I have found that many engines are simply heavy at one end: even simple 0-6-0s, never mind 4-4-0s and like animals, because we have a light motor at (usually) the blunt end and the potential for much ballast at the sharp end. Even a brass tube boiler can make it tip the scales the wrong way. Hanging the tender on the blunt end helps to even this out, and I have even been known to employ it in conversions of RTR stuff. The Hornby 28XX is a case in point, although that one is not too bad, but on a T9 it's a must unless you only want to pull a couple of light carriages. Apart from haulage capacity, I find that stabilty is much improved.

Philip

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Will L
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Re: CSB and tenders

Postby Will L » Thu May 17, 2012 7:57 pm

The thing is Philip, your CSB is designed around the loco CofG being in one specific place. Getting it wrong does have consequences see the section about The Crew here. If you can work out easily where the loco's effective CofG is when you've hung the tender on the back, that's OK, but I'm inclined to think that there are fare too many imponderables in there to be sure of the answer. Exactly how much weight is carried by the front two tender axles for instance?

I know some people see this need to get the loco balance right as an "extra complication" of using CSB, but actually:-

1. its only making you think about something that has always been an issue but that often went unconsidered. We are all familiar with locos who's pulling power has been surprisingly disappointing, probably because the weight distribution across the driving wheel has been left to chance.
2. It isn't difficult to achieve, all you do is weight the loco body till it's balance point is over the centre of the chassis. When balancing a loco, just remember that the point of balance is effected as much by a small weight at the extremity as a big one near the middle.
3. A properly balanced CSB( with equal weight on each axle) makes best use of the available adhesive weight, and will out perform a chassis where axle weights are significantly different, even where the total overall weight is greater.

As to stability, my conversion to CSBs was at least in part because these locos ran so much more smoothly than anything I've managed before. My last pre CSB loco was an 4-4-0 with wheel barrow tender. It has nothing like the pulling power of the CSB fitted 4-4-2 tank that followed it, and the quality of the rolling performance of the compensated chassis just isn't comparable with its CSB fitted sister.

Will

Philip Hall
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Re: CSB and tenders

Postby Philip Hall » Thu May 17, 2012 8:42 pm

That all makes sense to me, Will, and I shall have a go one day. I still think in some cases (at least the locos I've built) that with the motor at one end and the boiler at the other there is some difficulty in ballasting so that the centre of gravity is in the middle. Often this isn't helped by the requirement (not of my choosing sometimes) to pull a massive train, when I have felt my way is the best solution.

Perhaps the best balanced engine I have come across is a LBSCR Atlantic, for which I have the DJH kit, the body of which was kindly assembled for me by Tony Wright. I can't handle whitemetal in any quantity, and he made a far cleaner job of it than I ever could have. But this one I am going to spring in one way or another, because if you lay a fulcrum across the footplate between the splashers, it balances perfectly. I shall have a go at CSBs on the tender and take it from there.

Philip

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Russ Elliott
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Re: CSB and tenders

Postby Russ Elliott » Fri May 18, 2012 12:36 am

Will L wrote:No sprung chassis lends itself to the sort off centre weight distribution wheelbarrow tenders give.

Whilst I agree with Will's later caveats, I think that generalisation is wrong. Any weighted tender can impinge on this 4-4-0 drawbar and the driver weights will still be equal, and will remain equal irrespective of the loco CofG placement:

4-4-0sp-eqs.png
4-4-0sp-eqs.png (2.41 KiB) Viewed 5883 times


If those drivers were on a 3-fulcrum CSB however, the CofG placement becomes critical (and regardless of whether a weighted tender is applied).

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randallb
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Re: CSB and tenders

Postby randallb » Fri May 18, 2012 9:23 am

As I am a completely newbee, without yet so much as an RTR conversion or otherwise under my belt, it may be a tad cheeky to throw my hat full of opinion into this ring.

I was completely bowled over by Chris Pendelton's deltic conversion - especially the comment about the axle boxes doing a mexican wave as they traveresed what he described as some of his "less good" track. At the time I was just thinking of getting started on a tender kit (for a fish engine from the John Bateson stable) which I had purchased to see if I was capable of working to any degree of proficiency in sheet metal.

Anyway to cut to the chase, I experimented with different forms weighting and holding said tender off the rails - and despite perhaps a natural inclination to use what might have been the case on any given prototype I am already sold now on CSB's. Having reached the point in the kit where I needed to make decisions (bear in mind - 1st one, thinkinh about this sort of stuff in advance for subsequent was one of the learning points ......) I did the research, ultimately settling on the decision to have each "vehicle" as a stand alone entity - from a weight perspective - and settling at 1g/mm over headstocks.

I then ploughed through the digest / CLAG site (and others); prior to doing which i'd attempted / perpetrated several monstrous attempts at springing - and arrived at the final solution of CSBs (which to be fair John Bateman had built the kit around in the first place !!!) however, I did recalculate fulcrum points, change the axle bearing holder length and settle on a free moving trapped CSB to end up with something which carried the weight of the tender (now not inconsiderable) but would easily ride upwards over one of herself's nail files - thus emulating Chris Pendleton's nifty trick - NICE !

.... All I have to do now is build some track, fininsh the tender kit, build some loco's .............. :D :D
Randall

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Andy W
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Re: CSB and tenders

Postby Andy W » Tue May 22, 2012 9:22 am

Thanks for all the advice and comments. I shall start dipping my toe into the csb pond.
Make Worcestershire great again.
Build a wall along the Herefordshire border and make them pay for it.

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David Thorpe
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Re: CSB and tenders

Postby David Thorpe » Mon Nov 05, 2012 3:11 pm

I'm just making my second CSB tender. Normally for this one I'd want tender wheel pickups, using p/b wipers on top of the wheels. Can this work with CSBs? Logic tells me it shouldn't, or that at the very least it should interfere with the CSB set-up, but when it comes to maths and physics I have no logic anyway!

DT

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Russ Elliott
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Re: CSB and tenders

Postby Russ Elliott » Mon Nov 05, 2012 4:27 pm

Tyretop pickups will be fine with CSBs, DT. The pickup force will be small compared to the wheel force. If you're worried about the pickup force, a good way of lessening it but maintaining a high pickup pressure is to use a stylus form or pick up off the flange edge with curly-wurly designs.

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Will L
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Re: CSB and tenders

Postby Will L » Mon Nov 05, 2012 11:11 pm

DaveyTee wrote:I'm just making my second CSB tender. Normally for this one I'd want tender wheel pickups, using p/b wipers on top of the wheels. Can this work with CSBs? Logic tells me it shouldn't, or that at the very least it should interfere with the CSB set-up, but when it comes to maths and physics I have no logic anyway!


It works and I have the running tender to prove it
csb 04 3.jpg

This has been wandering back and forth across Knutsford East behind my CBS fitted O4 without problems for about 3 years.

As Russ suggests the pick-ups are designed to be a lot softer than the CSB springing, though a did make sure the pick up springs were the same length and hence insured that they are balance and applying near equal pressure on each wheel. I would certainly be looking for a different solution if I couldn't achieve this balance. I used top wipers on the O4 too. Because I couldn't get them on all 4 axles, I stuck with a balance pair on the centre two axles. More pictures of this the loco and tender chassis in this post. Ever since I published that I've been waiting for somebody to question the use of top wipers as they clearly form part of suspension, so what took you so long.

Will


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