P2 Locomotive Company and related matters

I'm in the dark of the current situation and it seems so are others, perhaps ? The main problem is not looking at all the current data, including Dave Elliott's brain dump, it is trying to place yourself in his thinking train, which is difficult now after his passing. It's not engineering it's, in a way, phsychological...a very difficult situation.

 

Morse made the chains, that’s for sure.

 

At this point, I'm out of my depth, so I won't comment on potential pitfalls, but I will say this, It really does need for a model to be made up, and for that model to literally be tested to destruction, to find out how the mechanism reacts to every potential scenario and then for changes to design to be tested before any metal is cut, or machined .

 

No they don’t and the model is over three years late!

 

All that can be created in FEA Martin, you don't need physical models.. I'm not trying to belittle you... you'd be amazed at FEA, you really would...

 

I thought Hans Renold, a Swiss engineer invented and patented the chain way before Morse... I stand to be corrected btw..

 

Have read Brian Read about 50 Pennsylvania T1 that had oscillating cam poppet-valve gear Franklin A that were difficult to maintain.


A single set of rotating cam called Franklin B was tried on a Pacific K4 in 48 .

A T1 was rebuilt in 49 with Walschaerts and piston valves.

None of the freigth duplexi had anything but normal piston valves and Walschaerts

 

I think the Franklin poppet valve gear on the K4S 5399, the first loco to be fitted, was the so-called "Type A" i.e. oscillating rather than rotary (Type B). The paper given to the ILocoE in 1943 by a representative of Franklin reads a bit like a sales pitch but that also seems to emphasise the oscillating version. I don't know how extensive the use of Type B was.

 

I'm lost.... truly...

 

So am I. The P2 material leaves more questions than answers. A mystery which no-one seems to explain is how the cams worked. I think in Caprotti gear there were two identical inlet cams (which are a bit like shaped disks, or more abstractly, profiles), which could be "fanned-out" to provide a longer valve opening (on Caprotti, the valves always moved the same distance unlike piston valves, the cut-off being determined by how long the valve stayed open). No info on how this is done in Franklin gear.

 

I'm not religious...but thank god.. I was just about to reach out for the Tanquerry...

 

Like I said, This goes above my level of knowledge The reason I prefer to see a solid model is that you get to see things like how the wear lines, happen, use, at which point it becomes an issue, mk 1 eyeball, whilst FEA is very good, theres a lot to be said for observing moving masses. And, i'm fine with this type of reply, keep things sociable and everyone will get on, we all have days when we can snap over what might seem nothing, i have a lot on my plate, and some days i cope better than others,

 

One question that bothers me is this, we have 71000 and an Capriotti valve std 5, and extensive knowledge of the system, Caprotti works on 3 cylindered engines, 71000 had quite an extensive research over what worked and didn't, during its mainline ticket, so why wasn't Capriotti valve gear and poppet valves, used for the P2?

 

But it was Caprotti modified gear by British engineers, not pure Caprotti... maybe there's more room for improvement Martin.. let's see what develops eh ?

 

I'm afraid I couldn't work with the current regime, though, from what I've observed I am sorry to say.

 

The presumption here seems to be that David Elliot knew what he was doing and it is only after his passing that the Trust has lost its way. If that is so, why are doubts now being cast on the valve gear design?

 

I'm not knocking David Elliot, I have a lot of respect for what has been achieved, but anyone is fallible, Whilst The valve gear is well known on the continent, and in the US, it never was widely used over here, I don't know why that was, Simplicity of design I would guess, why change what's been proven to work, or an element of not done here sticking with old trusted designs, I think the chosen design , or what the options were should have been subject to further work, and prototype modelling , not just on CAD, but by building mock ups to establish pros and cons.

 

The plan is (or was) to build a prototype of one side of the valve gear, then test that extensively under real-life heat and stress conditions to iron out any faults before going ahead with the final construction. Last I heard they were inviting tenders to develop the prototype. David had already built mock-ups by 3d printing.

 

AFAIK drawings for the gear and even some kind of operating manual were fortuitously found and copied from the US. As the ultimate development of that gear, i dont recall any other modifications being mooted other than to adapting the dimensions to fit and adapting the materials to modern availability.
Think the nearest we had to it in this country was the Reidinger variant of Lentz(rotary) which was tried out on a couple of Crabs - the reason Caprotti rather than this found its way onto the standards was as much to do with 'golf club connections' as merit. There is little doubt in my mind (possibly due to Mr Elliott) that the gear does work and its similar in principle to the original Lentz and does have some advantages over walshaerts, although for this loco i would have been happy with either as Earl Marishal was imo aesthetically superior to CotN

 

"Beauty is in the eye of the beholder"