4-4-0T csb

[Andy W]

Having been converted to csbs by Will and others I am looking to use them on my next loco - a 4-4-0T. I've now built several locos this way so I'm not a novice, and I haven't had a problem with the spreadsheet guides, but I can't find reference to anything like this. Maybe I've missed it? Or is it recommended that I treat as an 0-4-0 with the bogie sprung independently?

In "the old days" I would have built this with two side beams and a central pivot for the bogie. It would be good to explore the use of csbs on this loco. Any pointers gratefully received.

Andy

[Will L]

Andy

I covered a generalised way of tackling a any loco with a bogie which carries loco weight in the CSBs a question of Gravity thread. You need to read past section on CofG placement on a 0-n-0 to get to the bit you want. The diagrams show an 2-6-0 but the same approach works for a 4-4-0. If it need further explanation to make it clearer let me know. Like all these things the outcome is a lot less complicated than a detailed explanation can make it look.

Will

[Andy W]

Thanks Will. That was the thread I was searching for. I'll study it.

[Andy W]

That's very clear. Basically to get the % weight distribution between boogie and drivers I move the weight to shift the CoG forward or aft. The fulcrum points can be worked out as an 0-4-0 - or in effect as two 0-4-0s. Have I got that right?

[billbedford]

Having been converted to csbs by Will and others I am looking to use them on my next loco - a 4-4-0T. I've now built several locos this way so I'm not a novice, and I haven't had a problem with the spreadsheet guides, but I can't find reference to anything like this. Maybe I've missed it? Or is it recommended that I treat as an 0-4-0 with the bogie sprung independently?

Never spring a bogie. A sprung compensation beam on the bogie, copying the original, will work well, but so will just compensation. A compensated bogie will control the pitch and roll of the loco.

In "the old days" I would have built this with two side beams and a central pivot for the bogie. It would be good to explore the use of csbs on this loco. Any pointers gratefully received.

Just replace the two side beams with CSBs and it will work. For a two axle design, any symmetrical arrangement of anchors will work. The difficult part will be to balance the loco so the bogie takes enough weight to function correctly, but not enough to compromise the haulage.

[Andy W]

Thanks Bill. In the past I always compensated my bogies by having one side frame pivoted and the other fixed to the spacer. I think I'll do the same here.

[Will L]

Never spring a bogie.

Why? I agree it isn't easy to fit CSBs on a bogie because it's hard to get the outer fulcrum points far enough away from the axle. I learned this from your C12 chassis kit. But the C12 acquired secondary spinning too and the the result rides very nicely thank you.

[billbedford]

Thanks Bill. In the past I always compensated my bogies by having one side frame pivoted and the other fixed to the spacer. I think I'll do the same here.

It is better to pivot both sideframes rather than one, then the sideframes will mimic the original's compensation beams. The sideframes don't have to move very much, just enough to even out any track irregularities.

[billbedford]

Never spring a bogie.

Why? I agree it isn't easy to fit CSBs on a bogie because it's hard to get the outer fulcrum points far enough away from the axle. I learned this from your C12 chassis kit. But the C12 acquired secondary spinning too and the the result rides very nicely thank you.

As far as I can tell no steam loco ever had secondary spring suspensions. While some early locos, such as the C12, had only individual axlebox springs it was soon realised that a compensated bogie gave a much better ride by helping to control the pitch and roll of the rest of the frames.

[Will L]

Never spring a bogie.

Why? ..

As far as I can tell no steam loco ever had secondary spring suspensions. While some early locos, such as the C12, had only individual axlebox springs it was soon realised that a compensated bogie gave a much better ride by helping to control the pitch and roll of the rest of the frames.

Ok that makes sense although I still find the word "never" a bit hard to swallow. I didn't set out to provide secondary springs on the C12, it was unintended consequence of the way I implemented pick ups on the bogie wheels. I did register that the CSB springs didn't permit much movement of the axle because the outer fulcrums were too close to the axle. Given that the bogie frame was rigid and was designed to have a plain flat pivot allowing no freedom to rock for and after or side to side, I think I needed to do something. In any event the visible ride of the result is everything I would hope for from a fully sprung chassis. What it would feel like to somebody small enough to ride the footplate is anybodies guess.

Resonant frequencies are a key issue when considering the pitch and roll performance of undamped sprung systems. As time is a key factor in any frequency, and, as we know only to well, that time does not scale, it may well be that what proves necessary/practical the on prototype may not be on our models and visa versa. I would have though that the various forms of springy compensation beams with fulcrums at the centre only would give perfectly acceptable results but I'm happy that plain compensation will do the job too.

Where I personally don't want to go is to have a bogie, that ought to have a nice solid and visible front frame connecting the side fames together, but doesn't.

[Alan Turner]

As far as I can tell no steam loco ever had secondary spring suspensions. While some early locos, such as the C12, had only individual axlebox springs it was soon realised that a compensated bogie gave a much better ride by helping to control the pitch and roll of the rest of the frames.

Not quite sure what you define as secondary springing Bill but the Midland Bogie had a compensation beam that was attached to the frames using a leaf spring so that the beam could move against the spring as well as rocking.

regards

Alan

[grovenor-2685]

Primary springing is between axlebox (or compensating beam resting on the axlebox) and the bogie frame (or direct to vehicle frame). Secondary springing is then between the bogie frame and the vehicle body, ofter via a bolster turning with the bogie but connected to the body.
For the most part secondary springing is limited to passenger carrying vehicles, but some diesel and electric locos also have them. I don't recollect ever seeing a steam loco design with secondary springs.
Keith