P2 Locomotive Company and related matters

Quick question - Sorry if this sounds a bit stoopid, I don't have my book on the P2s to hand at the moment...
What is the purpose of the two bulbous casings in front of the cylinder block on 2001, and which will be fitted to 2007?
Looking at the frames I can't see any apertures for large diameter steam pipes or suchlike, but they must have had a purpose...

Richard.

 

Boiler news:

https://www.p2steam.com/category/news/

 

Can't help feeling that to use the latest version of the Franklin rotary cam valve gear, a design with no 'in service' history, is taking something of a risk.

 

I suspect that some people said the same about Stephenson’s multi tube boiler when it first was mooted.

 

As I have written a few times previously the Americans were very good when it came to the mechanical side of locomotive design. The P2 team have been at one level fortunate, though the search for archive drawings is difficult in the USA as they freely admit, knowing and being in contact with enough people can allow you to come across a huge slice of good fortune.

One of the supporters of the project was able to introduce the team to George Carpenter (you can read all this in the design study) and so the journey of discovery took them to Santa Fe Railroad 3752. They now have drawings and manuals for the Franklin B gear fitted to the 4-8-4 which provide sufficient information to carry out the detail design required. A big thank you here to Charles Smith who loaned them this material.

Vernon Smith worked for Franklin and wrote about his experiences (another book on the wish list - not cheap though). He was also involved with the fitting of the gear to 3752, the engine did have a few teething problems but these were resolved and the end result was an engine that produced more horsepower at higher speeds with substantially less fuel consumption than other members of the class.

So they have drawings, manuals, CAD, CAM, access to newer materials. as well as capable people. David Elliot will let us all know about the work when all is certain and ready. Fitting the original Lentz gear into a restricted space was one of the main issues with 2001, Andrew Hardy should be thanked for finding the relevant correspondence, but this is not the original gear, the Americans moved it along quite markedly.

 

And Walschaerts would be so boring...!

 

Not if you applied the variable lead type.

 

Thanks for a very well informative reply 242A1

Knut

 

For the sake of the P2 I hope it does work out. However, even David Wardale had reservations in his book 'The Red Devil and other tales from the age of steam' on page 370.

 

I appreciate the reservations. I don't know if David was familiar with the work of Vernon Smith and the development of Franklin B. D.W. essentially equalled the cylinder performance of 71000 with his famous guinea pig, Porta considered poppet valve gears to lack robustness and so preferred piston valves particularly when they included all the refinements that he developed, Chapelon had success with poppet valves but reverted to piston valves. Adequate robustness and leakage are the main problems with the breed but the Americans could seldom be accused of lacking robustness in their locomotive designs and solutions exist to the seat leakage issue. So things should work out. An improvement over the original installation should be expected and there should also be an improvement over the piston valve types fitted to UK mainline locomotives to date. Matching the best that modern piston valves can offer is another matter.

 

For those that are interested in Caprotti valve gear (and have access to Facebook) The Steam Workshop posted a video a 7.25" gauge "Duke of Gloucester" chassis running on air at

https://www.facebook.com/video.php?v=279670096194605

. The loco was built by the late Dennis Evans.

 

What were the reasons for the rotary failures?

Is the design fatally flawed or was it yet another case of great design but poor execution?

 

Didn't he build two more, one in 3-1/2" gauge and the other in 5" gauge?

 

Are we going to ignore these then?

Gresley D49



It's virtually the same as that fitted on no.2001 in detail and most of these (if not all? no.365 excepted as it had Reidinger gear) ended their British Railways days with this valve gear type. Hardly "fatally flawed" given they worked a good twenty five years or more virtually unaltered.

You could argue we're not comparing apples with apples given the wheelbase/tractive effort difference but these had 6ft 8in wheels and were very capable machines in the right hands, fast running possible.

So it's not a case that it didn't work in its original application - just, as always, a trade off between different factors.

 

Did the original version of the Lentz gear on CotN have any flaw other than the stepped cams, which prevented small adjustments of cutoff? That limitation could surely be worked around by adjusting the regulator instead, as recently mentioned in one of the threads here in relation to the Bulleid Pacifics with their idiosyncratic valve gear.

 

So there is clearly precedence for the design working well then.

Just to be clear, I don’t see any reason why this wouldn’t work or even outperform Wascharts. The only thing I’d have reservations about is getting the same throat and flow numbers through the valves. The bigger surface area the vales the better.

As an aside, this Is strikingly similar to Hondas VTEC system. This is variable valve lift which is what the original VTEC system is. Rotate the pick up box angle on the crank and you have a full blown VTC system, retarding or advancing that lift to suit engine load conditions. K20A/F20C engine codes for those interested.

 

Are the poppet valves similar to the Caprotti design, which allow flow through the valves as well as around?

I though that the VVT systems adjusted the valve timings according to engine RPM rather engine load?

Dave

 

VTEC/VVT are not the same as VTC.

Load and RPM are somewhat functional but yes, extra lift happens at higher RPM. Get more calories through the system = more power.

VTC advances and retards based on load. Low RPM and WOT and you get the extreme where VTC makes the most difference. Adjust valve train for extreme engine conditions = optimise system for high and low RPM conditions.

It’s not an apples and apples discussion but the similarities are there. My key point is these designs are the very same principles that underpin VTEC/VVTI/Vanos/Variocam.

Anyway. There is no reason this can’t work well on the P2. It works well on DoG doesn’t it?

 

Thanks @W.Williams

Dave

 

As I understand it, the cam lobes wore very rapidly due to insufficient surface hardness, but this can be overcome nowadays by modern metallurgy.

Adjusting the regulator was a method that was used, but this had a negative effect on efficiency and contributed to 2001's reputation for heavy coal consumption.