New Build Night Owl - 4709 Begins

So ... if the front end is a fixed unit how do you allow for a movement/ rotation of the whole unit to confer with a frame alignment, and then fix it in position ?

 

It is Swindon stuff. I try not to bother or understand.

 

Special Gouch hammers ?

 

Whatever way you want, as long as it is different to the way any other railway would do it.

 

Hey! There's the right way, and then there's the way other railways do it.

 

Swindon just holds the cylinder casting and expects the world to revolve round it...

 

There you go, i expected some thing along the lines of Bolted permanently in place and any minor adjustment required done by precision grinding of the horn guides but these answers are way funnier.

 

I was recently asked by Dinmore Manor Locomotive Ltd to assist them with the optical alignment of their new cylinder/frame extension assembly for 3850.

• The main frames had previously been set level on a set of adjustable steel stands.
• The new front end assembly consisting of the frame extensions and cylinders was moved into approximate place and mounted on an adjustable lifting frame.
• A pair of Taylor Hobson micro alignment telescopes were mounted, one in each cylinder, concentric with the front bell mouth of each cylinder. This establishes a 'line of sight' which is on the true centre line of the cylinder at the front.
• At the rear bell mouth of each cylinder a precision glass optical target was installed and set true to the centre of the cylinder using a rotating dial gauge. This establishes a point which is on the true centre line of the cylinder at the rear.
• The two telescopes are capable of being adjusted within their mounting frames for the direction in which they point, whilst maintaining concentricity to the bore. The two telescopes are now adjusted so that the cross hairs in the eyepiece are focused and aligned with the target in each cylinder rear bell mouth.
• From this time onwards any object seen through the telescope which lies on the intersection of the eyepiece cross hairs is also on the cylinder centre line, from the end of the telescope to infinity.
• A pair of datum marks were set up on the nominal cylinder centres line at the rear of the frames.
• It was now possible to adjust the whole assembly so that each cylinder centre line was not only at the correct height from the top of the main frames at the front, but that each cylinder centre line intersected the nominal cylinder centre line at the rear of the frames.
• Using either a precision level or a Taylor Hobson Talyvel on each telescope body it was also possible to confirm that the bores of both cylinders were horizontal.

Any errors in the measuring equipment are insignificant when applied to steam locomotive construction, building temperature changes and resultant frame expansion have a greater effect on alignment accuracy. The whole job from first setting up to clamping up the frames ready for reaming out the holes for the fitted bolts took only a few hours.

A few photographs taken of the process in action.

The new front end on an adjustable frame.


The two telescopes mounted in the cylinder bores.


The optical target mounted in a frame with a rotating dial gauge.


A view through the eyepiece showing the cross hairs and the central dot on a target, the dot is a few thou in diameter.


Andy.

 

So once the front frames are aligned with the datum on the rear frames 'clamping' in place and coincidental reaming of the joining bolt holes is what fixes the alignment...(?)

 

I suppose I could post a link to this again.
http://kesr-mic.org.uk/resources/The+Steam+Locomotive-A+Machine+of+Precision.pdf
Cook is quite silent on the means by which the cylinders were aligned to the frames. By the time of this paper he was working at Doncaster so there's nothing about the particular requirements of the Churchward extension frames.

 

I have to say that I for one have struggled with this description. If the extension frames are new and undrilled I can see that you'd just move them around until aligned and then drill and ream. But if one is recycling an existing set of extension frames, what happens if the hole alignment isn't quite right? Are the holes welded up and re-drilled? Or drilled slightly oversize till the alignment is ok then reamed?

 

Hi 61624
As Aberdare says at the end of his very informative post " The whole job from first setting up to clamping up the frames ready for reaming out the holes for the fitted bolts took only a few hours". So, hopefully, none of the holes are too far out of alignment.

 

Just stumbled upon this post, was good to work with Andy on the alignment of our new front end and more recently the further alignment work to enable us to carry out horn machining.

I note comment about lining up existing holes; due to a front end impact in pre-preservation days there was always a slight twist in 3850's front end, down to the left. As it was the l/h cylinder cracked top to bottom one would assume this impact had placed the cylinders under stress ultimately fracturing them with further service. Due to this twist it was deemed sensible to replace the extension frames with new items, machined from solid by Roach Engineering including the drilling of all holes. The quality and accuracy of their work is fantastic, they also machined the cylinders and a pair of shaped 'angle irons' for us. Once all three pieces were together, Cylinder, Extension Frame and Angle I used a reamer ground to just 3 thou above the nominal hole size through all three components to achieve a perfect hole, many wouldn't have even required that.

Having the new extension frames meant we could leave the main frame joint 'blank' for drilling and reaming to suit at the completion of the alignment work.



First trial fit of the new extension frames underway. We are fortunate to have a number of keen younger people within our group who have all enjoyed working on this project, I discount myself on the right as falling in to the young category anymore...!






All assembled awaiting the painters and turning over






Somewhere at Swindon??



Andy at work



Slowly easing the new assembly in to place, all 6.5 tons of it on greased up RSJ's and a hydraulic pusher...


Back to 4709, for my sins I have been asked to oversee/build up the front end for the loco, The cylinders (new) and extension frames (modified originals) are as good as ready for collection from the machinists so before long assembly can commence, with the benefit of the experience above for 3850 things should be a little more straightforward, I hope...!

Regards,

Mike

 

Has someone been reading a certain book by Rev Awdry again?

 

Is there an emoji for ' sharp intake of breath and concerned glance '

 

Absolutely right, if not Andy and Myself have got something rather wrong.......!!!

Regards,

Mike

 

Thanks for the photographs and updates - glad that it is all going together well.

 

Commenting on another page has made me think of this and to go online, no updates for nearly 12 months on either their website nor Facebook, and nearly 2 years on from the whole Thornbury saga is anything actually happening with this project, I don't recall it ever being mentioned in the GWS Echo in recent times either?

 

I don't believe they are flavour of the month at Didcot. In the circumstances it would make sense for them to keep their heads down and just get on with the funding they have.
What you need are eyes on the ground at Tyseley.
There's a recent photo of 7027 here:
https://www.flickr.com/photos/andrewkmurray/53780633355/
Makes an interesting comparison with this one from 2018
https://www.flickr.com/photos/47384914@N04/46086053692