BR Standard class 6 No. 72010 'Hengist' and Clan Discussion Thread

Deleted - I managed to enter the same thing twice

 

Latest news on bogie centre slide here

https://www.theclanproject.org/Clan_News.php

Bogie Side Control Springs - "You have more chance of getting rocking horse droppings." - quite right! The side control springs play an important role in the riding of a locomotive. You can read about some of the background to the design here

https://www.theclanproject.org/build/Clan_BuildTopic.php?topic=BWA&description=Front Bogie

We have not been able to find a supplier who still manufactures rectangular section springs. The trapezoidal section material should not be a problem. We have BR drawings for the materials and the calculations are known. Forming the springs is the problem. Firstly because you need to make heavy duty formers to roll them, secondly as you have to do it quickly so that the metal does not cool down to much. We know of one supplier who stopped making them not that long ago. Rectangular section springs are available in smaller sizes.

We talked to a manufacturer in the West Midlands who came up with a round section coil solution which uses inner and outer springs to produce similar spring rates. You can see that Keith has built the solution into the 6th image down (excluding the main top one) on this page.

https://www.theclanproject.org/build/Clan_BuildTopic.php?topic=BWA&description=Front Bogie

We have seen pictures of locos that have been fitted with round section springs where the spring has distorted slightly. Keith has modified the distance piece and the spring guide (click on image 7) to provide a bit more containment for the spring. #

The preference is to try and find someone who can produce the rectangular section springs. If we have to adopt an alternative, it is likely that we would have to go through Vampire Testing in order to prove that the ride characteristics had not changed. The P2 project have gone through this testing.

https://www.p2steam.com/design/

Vampire Testing comes at a cost.

The better news is that the side control springs are not on the critical path and are not holding anything up. We can fit them later when we find a solution.

Ian

 

Round section side control springs are not new. The side control springs on the bogies fitted to the Royal Scots were altered to round section springs in 1953. See the arrangement drawing D53-21819 at the NRM (when it re-opens) or in the book "LMS Locomotive Profiles No 15 The Royal Scots"
The likely reason for any spring distortion on locos presently fitted with new round section side control springs is that the loco owners have not made new check spring spindles that take into account the different internal diameter of the new springs.

 

Engineering is brilliant.

 

It's really good to see you all and CTL Seal continuing to make substantial progress. Especially so since the Hengist project hit that very large bump some years back; it's very heartening to see yet more proof that it has fully recovered from that early set-back. I'm looking forward to more good news!

Noel

 

There is often a disagreement between 2 engineers about how a design problem can be overcome, and often they are both right!
A fascinating item about the P2 though. Not sure where it leaves us at the minute.

 

For any design changes that affect critical areas of the locomotive, we know that the Regulators (the Notified Body NoBo) are going to review. Therefore it seems probable to us that if we chose the round section spring design change we would need to confirm that the stability has not changed through Vampire testing. We do have a worked up specification for this solution. So we are still seeing if we can find a manufacturer who can make the original springs as that will not be a design change.

There's a lot of work going on in the background to ensure that our documentation systems will meet modern requirements. Design change is a key aspect with a need to demonstrate a through risk evaluation

Ian

 

Out of curiosity, (1) what type of spring do the existing mainline BR standards (Britannia / Oliver Cromwell / Duke of Gloucester) have (2) are they the same design as were originally on the Clans and (3) what would those owners do if they had to change a spring, for example if one broke?

In other words, if you had to make a design modification of the bogie, is that a modification that has been, or could be, faced by the owners of other similar locomotives?

Tom

 

1. Exactly the same spring is fitted to Class 6, 7, 8. Class 8 differs in that the centre slide is not quite as wide as class 6 and 7, i.e. same drawing but a bit more is machined off. This allows the centre slide to move a bit more and thus put a higher load on the spring (or vice versa!). Load at max movement on class 6, 7 is 4.38 tons, load on class 8 is 4.44 tons (detailed on drawing SL/DE/21002)

2. We understand that 71000 replaced the spring in the 90s but the company that formed the springs is out of business. We have been talking to the groups involved in 70000, 700013 and 71000 and may form a group to buy a reasonable quantity. A very similar spring is fitted to Class 5 4-6-0, Class 4 4-6-0 and class 4 2-6-4T who may join in a purchase

3. Faced by the owners of other similar locomotives - yes. Side control springs don't seem to break at the same rate as suspension leaf springs.

 

Thank you.

Tom

 

Getting my instinctive hat on , there may well have been sound reasons for preferring a square section spring, less space needed, less tendency to distort , simpler to 'house'. already had 6 dozem in stock... but if a square section spring is not mandatory in bogie slide control ( and i think its safe to say it isnt) then as long as a round ( or elliptical ? ) cross section spring exerts the same magnitude of resisting force then arent we ok ?
Vampire will only demonstrate riding characteristics based on the data its fed, and if you already have that data, and presumably some data about what the original was (supposed to be) doing is the simulation necessary ?. We are comparing Coxs with Braeburn, the P2 is very definitely apples replacing pears...

 

Has it been considered to turn the springs from solid?

 

The grain structure in the springs would be wrong if you turned them from solid. Rolling the wire/bar aligns the grain structure with the axis of the material. It would be fun to try but restraining the part machined spring would cause some interesting problems.

Sent from my SM-A105FN using Tapatalk

 

Start with a piece of seamless pipe of reactor grade and shrink or soft solder it unto a mandrel of lesser breed.
It is around 200 cubic inches to remove and a good lathe removes one cubic inch per minute per horsepower.I seem to remember

 

IIRC rectangular section springs are used in presses?

 

JOOI, how much (in approximate terms) would a Vampire study cost? If square section springs are no longer available, would it be worth all parties chipping in for the design validation. (with the selling point that no safety case ever gets cheaper, so getting a sign-off for the replacement spring case now is cheaper than if it goes ping! in ten years time)

 

Perhaps it is time to ditch the two pairs of short springs for two long springs, similar to what is on the Royal Scots. The spring lengths will be slightly different to what is on the Scots, but you have a start in a known and proven wire diameter and the outside diameter of the spring..

 

Take it that the design of the Royal Scot Bogie (Derby ?) and the way the springs interact with it is very similar to the standard pacifics

 

Thinking outside the box...round bar starts out as square/rectangle bar in a rolling mill

 

Not sure but I would have thought North British.