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

Back to the day job!

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

We're finally starting make progress on the cannon boxes. Our major problem is that we have the British Railways drawings for the cannon axleboxes which are basically "rebadged" Timken drawings. Unfortunately all we have is the arrangement drawings which show the assembly and give the dimensions for the axlebox body. We don't have any of the manufacturing drawings for all of the internal components. So by deduction and interpolation, we have been able to create our own drawings. The NRM have been very helpful in that we have been able to get hold of the minutes for the Chief Draughtsmen meetings for the BR Standards. Some of the clearances are detailed in the minutes. Timken have also helped in that they have checked our drawings and have come back with minor recommendations for some changes of tolerances. The axles and tyres are now in stock at the South Devon Railway. Wheel bearings are in stock at CTL Seal. The wheels have been cast some time ago. Unfortunately we spotted what was a minor crack which turned out to be deeper that was first thought. This was fixed last week and the wheels will need some first stage machining before they are sent to SDR. We are about to place an order for all of the internal components with the aim of sending a "kit of bits" down to the South Devon Railway

 

Please could I ask if there is a real need to fit roller bearings for the mileage the loco will do in service?

 

Could you clarify, please? Do you mean at points other than where the original design specified them?

 

The locos when built by BR were fitted with roller bearings when you could buy the cannon boxes and bearings off the shelf from Timkin and SKF and in-service continuously apart when stopped for maintenance, with no issues of cost or downtime.
But now they will spend more time cold and only in steam on high days and holidays so would you be better off with white metal bearings that can fixed relatively easily, quickly and with far less expenditure and downtime?

 

If you are considering running on the mainline you want to eliminate what might be viewed as a weak feature. Having an overheated bearing inflicting hours of disruption to the network is not viewed in a favourable light. There are good reasons why the construction of 2007 features roller bearings, bearings which were available off the shelf from Timken.
It is strange how some enthusiasts are committed to doing things the way they believe things have always been done. You could have valve rings with a 50,000 mile service life, piston rod packings lasting nearly 1/4 million miles and so the list goes on. Any railway management will now be more acutely aware of increasing costs and pressure on income than they have been for a long time and it will be interesting to see the reactions to this.

 

I would say that most of the locos of the steam locos out on the mainline are running on whitemetal bearings and do not see they have issues with them very often.
Wheelsets with roller bearings will need the wheelpans pressed off if there is an issue with them, which could mean the loco is out of service and not earning for weeks or months plus the axle wheelseats may be damaged so the axle could need replacing.
Whitemetal bearings can be repaired in a few days at a nearby heritage railway.

Keep it simple stupid

Drawings are for fools and the guidance of the wise

 

Excellent progress, good to hear!

 

Dave

The problem is that the wheelsets are a critical item for main line running. We have a design for roller bearing axleboxes - there is no design for a plain bearing version as classes 5, 6, 7 and 8 shared the common design (drawing SL/DE/19545) that used roller bearings. If we wanted to change to a plain bearing design we would have to go through the main line design validation process which would probably cost more than reproducing the roller bearing design.

For the driving wheels, the case is slightly different. Although all of the Clans were fitted with roller bearing axleboxes, some of the Britannias were fitted with plain bearing axleboxes - and there is a design available - see https://www.theclanproject.org/design/Clan_Bearings.php. However, this was a Class 7 design and was not part of the design for Class 6 lot 242. So we would probably have to justify, and possible prove, our design change. Your comments about repair are correct and that has been part of the debate in our design documentation. However, it is very likely that we will go for roller bearings for the driving wheels. A strong recommendation for roller bearings has come from one of our consultants who worked on engines with roller bearings and engines with plain bearings in Crewe works.

 

So , if you were say a farmer, you would use the products of Marshall, Sons and Co, or Heinrich Lanz AG - single cylinder machines, nice and simple? You could have your computer built using the 4004, along with its associated 4001, 4002 and 4003, again rather simple? Your home electronics could be simpler, more robust and easier to repair too - but would come at a price beyond what most could afford?

Some people are enthusiasts supporting the products of L Gardner and Sons, compared with newer engines they are dirty, inefficient and underpowered but have the reputation for not wearing out. They are kept going but you cannot buy a new one, time caught up with the company with the inevitable consequences, you might say that they were stupid for trying to keep things simple.

Dropping your watch used to be a serious matter causing damage to the arbor or its bearings. A system invented in the 1930s and in common use by the late 40s/early 50s largely solved this problem though it did make things less simple and more expensive. Welcome to the land of Universal Escapements Ltd, who you might better know as Portescap, and the invention is still used to this day and is known as Incabloc. It came about not from a desire to keep things simple but rather to address a problem and so improve a product. Improving bearings, where have we come across this before?

 

Nice to see so much "engineering" thought put into this project.

 

OTOH - engineering isn’t about designing the best thing, it is about designing the best compromise between often conflicting requirements and constraints.

For a start, if you simply want the best people mover, you wouldn’t start with a steam locomotive. So the very fact of building one in the 21st century is sub-optimal from the point of view of “best” design for the job: you know you are building something obsolete.

So then you are into how do you nonetheless optimise for 21st century conditions. You know that water is less available now; the track is completely different (largely continuous welded with heavy rail profile etc). More significantly, any repair will now be a cottage industry job; proper locomotive works like Ashford or Crewe don’t exist, and if anything goes wrong, you are likely looking for space in a small one or two bay workshop, with an overhead crane and wheel drop if you are lucky, and sending wheelsets away (to South Devon?) and probably waiting perhaps months in a queue for any serious issues.

So we aren’t in the 1950s: simplicity of repair and ability to repair in a relatively low-tech facility strikes me as worth exploring, or at least not dismissed out of hand. What was the best technological solution in the 1950s when workshops had a capacity to repair hundreds of locomotives every year is not necessarily the best answer now.


Tom

 

…… conversely you might prefer to go down the route of keeping it away from such facilities as long as humanly possible?


Sent from my iPhone using Tapatalk

 

Well yes, but how many mainline failures have there been in recent years caused by locos with plain axleboxes running hot?

Tom

 

I seem to remember 60103 dangling from three cranes on the Nene Valley to extract a coupled wheelset (an objectively hazardous operation that it is desirable to avoid), in very recent times. Obviously, if you have a wheel drop that sort of thing is much easier, but having bearings that can reliably be expected to last several overhaul intervals saves a considerable amount of risk.

 

Except that in this particular case the question in post #2282 was about a possible departure from the BR roller bearing design. There would be both pros and cons, well explored in the subsequent posts.

 

Does a new build not need a comprehensive design validation process even for design elements that are unchanged from what BR did?

 

Ian, what you don't point out , or possibly don't know, about the Britannias fitted with plain bearings is that they required re designed frames to accommodate the smaller plain bearing axleboxes.

 

std tank. Thanks - I wasn't aware of that change to the frames - and presumably the hornguides. Looking at the frame keep drawing SL/DE/21133, it only applies to the roller bearings Class 7 so I guess that the frame keeps are different as well

MellishR. Well, as engineers, we are creating design reviews for each of the major sub assemblies. I've just updated the Cannon Box design review document which is 46 pages long.

If we can show that a component

1. Is part of the original design
2. It is currently operating on the main line without any issue

then the design validation is straightforward. In the case of our bogie, it is almost identical to that fitted to 70000 and 70013 both of which have been passed for the main line. The one minor difference is that we are not casting in the bosses for the Western Region Automatic Control System (not the same as AWS) This change is covered in the design review and has a risk assessment.

If we were to modify a key item on critical items, wheelsets for example, the design validation would be more extensive.

 

Thank you. That makes sense.

 

Is there yet a solution for the bogie side control springs?