New Build Night Owl - 4709 Begins

Unless they want to go down the route of how they were originally and unsuccessfully designed with the same boiler as the 28xx it'll be a new big ticket item. However, alot of the other big ticket items seem to have been covered with the spres recovery from the other locos.

 

Deleted, used wrong quote.

 

I seem to recall reading an article many years ago where a footplate inspector was very critical of the riding of the 4700s and attributed it to the sideplay in the REAR axle.

By the way, as a matter of interest following on from the above, can anyone tell me was the rear axle sideplay controlled by Cartazzi slides?

 

Found this on the Didcot website.
The cylinder block from 2861, with outside steam pipes, is identical to that of the 47XX and this will be used for the rebuild. A simple solution has been provided for the different saddle radius to take the Swindon No 7 boiler and this is currently under review by the VAB.

 

Thanks David (and others above).

 

answer already given

 

The no7 bolier was unique and was a big one at that. The no 8 boilers on the Castles are smaller, the 7 having been hoped to be able to be fitted to them, but having been found to be too heavy a lighter alternative had to be found.
Hopefully, the group will find enough support to pay for a new one. They have had a fair bit already, and I will be contributing sometime when I had more money.

 

That is a self contradictory statement. They are not identical if they need to find a solution to the different saddle radius that is acceptable to the VAB.

 

Many Thanks for your answers to my question Gents. That makes it easier to understand! I hope the group are successful in having a No.7 boiler manufactured, it looks like being a very impressive machine indeed when completed.

Richard.

 

On the question of the engine ' wagging at speed' We have side control springs at the front that may allow a resonance to build, and a cartazzi style arrangement on the rear axles which would resist this, but clearly not enough at higher speeds... Seems that some kind of damping needs to be introduced to the system
A bit off the subject but... Most locomotives ride on leaf springs with Rubber pads somewhere in the system to provide an elemnent of damping...Havent we come up with anything better than rubber in the meantime ?

 

Friction between the leaves is likely to be the main damping force with leaf springs. Rubber isn't a good damper - after all, classic minis had rubber cone springs. It's possibly used to eliminate shock loadings to the loco springs due to rail irregularities.

For bogie or pony truck side control damping some locos have friction grip side control as damping, with springs to provide side loading which eases the loco into the bends.

 

Didn't some Ivatt and BR standard engines have rubber between the ends of the springs and the bracket/hangers they ride on?

 

Possibly, and Lord Nelson definitely has rubber blocks there, but they don't provide damping. They ease the application of load to the springs, and in the case of minute changes they may act as springs without disturbing the metal springs themselves, but they won't damp the movement of the metal spring when it occurs.

 

Thanks L plus, as Lingus points out thats what i thought the rubber was there for. hence my query as its not a great damping material. Even so; the leaf springs action is controlled by how tightly they are 'clamped' and the conditions of the surfaces of the 'leaves' will have a bearing, but all in all its a pretty crude system. How does modern rolling stock approach this ...? and is there scope for fitting this to 4709 ? !

 

I'm no expert but, Out of interest how many spokes does a night owl have in its wheels ?
I was comparing a pkp ol49's 18 spoke wheel diameter (175cm), to a 47xx's 5'8" ... My maths I get 173cm...

Reason I say this is there's many ol49's around, and at least 2 going for scrap.. If the 2 cm's ( 5/8 of an inch) difference could be managed within the tire thickness they could get a full set of wheels for a few hundred quid. ( the whole ol49 currently up forsale on pkp's website is only £8k).
Balance weights can be changed so Is there more to it than that ?

 

Nice idea, but I can't see the copper-capped mob approving the somewhat glaring differnces in wheel spoke detail ...... http://rfe.railclub.ru/pix/pl/steam/Ol49/69/kg0750.jpg

 

Last I looked a Ol49 was a driving wheelset short.

 

Ypu also need to look at the cranks pins, both the location and size. I don't know if they are the same but I doubt it.

 

They already have 3 wheelsets from 4115. I believe discussions are well advanced for a pattern to be made to construct the 4th, which means there will also be a pattern available afterwards for a 5'8" wheelset (43XX / 5101 / 68XX / 78XX).