Don Young L and Y Aspinall Class 27 - Not Midlands

[kipford]

Holiday's and family commitments have slowed things a bit recently. However things have been progressing. First I was not happy with the fit of the fire box wrapper to the front and rear plates. I found this was due to an error on the former for the ends. It was only slight but enough to need sorting out. So I needed a new former. This came in the form of a 3D printed one that proved more than capable of taking the hammering required to reshape the flanges. The picture shows all the firebox parts with the wrapper and end plate formers.

IMG_3108 by Dave Smith, on Flickr


Next I needed to start thinking about a drill jig to keep the boiler parts in their correct place whilst location holes are drilled. Not wanting to spend loads of time making a complex jig, I came up with a fixture that uses a laser cut (I have a friend with a biggish laser cutter) MDF base that forms a 'U' channel with features to assemble 3D printed parts that locate the various parts of the boiler. 

First picture shows the CAD model, then the basic parts and the assembled jig.

IMG_3088 by Dave Smith, on Flickr

IMG_3093 by Dave Smith, on Flickr

IMG_3094 by Dave Smith, on Flickr

Final pictures show the front tube plate located and then the parts that form the outer shell. I have not drilled anything off yet as some of the boiler parts still need things like tube holes, cutting to length etc.

IMG_3095 by Dave Smith, on Flickr

IMG_3109 by Dave Smith, on Flickr

IMG_3110 by Dave Smith, on Flickr

That is it for now

Dave

[kipford]

So we slowly progress. The outer casing has been drilled off on the jig and is shown in the first two photos. The third shows the drill jig set up to drill off the firebox. 

IMG_3113 by Dave Smith, on Flickr
IMG_3116 by Dave Smith, on Flickr
IMG_3114 by Dave Smith, on Flickr

[coniston]

Coming on great Dave, I'll have to get my Pansy boiler to the same stage so I'm not left behind.

Chris

[Cro]

Oct 12, 2021 21:28:12 GMT coniston said:

Coming on great Dave, I'll have to get my Pansy boiler to the same stage so I'm not left behind.

Chris

I need to do the City too! 

[stevep]

Tell me - what are those two big holes in the backhead for?

And are those tapped holes around the regulator bush hole?

[kipford]

Steve
The slotted holes either side are for a machined block that locates the clacks and steam valves for each injector. The holes around the regulator bush are clearance as there is a block silver soldered inside the backhead which is tapped to take the regulator assembly. All as per the DY design and a reasonable representation of the prototype. Picture below of my CAD model shows how it is arranged without any fittings followed by a shot of the backhead of the preserved loco
Boiler2 by Dave Smith, on Flickr
8094681638_ff3779e99a_b by Dave Smith, on Flickr
Dave

[davewoo]

Hi Dave

I don't know if this will be any help, but I cheated and bought my boiler from Western Steam, in the paperwork is this drawing by Helen showing a thickening plate she has put around the firehole door. Presumably to give something substantial to break a tap off in!.
Thought it might be of interest, seemed quite a good idea to me.

[jma1009]

I am not sure about Helen's backhead alterations. I would certainly add 2 additional stays each side of the fire hole (4 additional stays in total). The 3/16" plates don't provide support for the inner firebox doorplate in this area and leaves this area unsupported. Furthermore, the 3/16" plate will seriously reduce the water space and could easily affect the reading of the water gauges.

The Stroudley/Webb type firedoor that hinges inward from the top can easily be fixed in position via the stays above the firehole going through the tray. The tray forms part of the firehole door. I did this on my 'Stepney' terrier. (I should add that I don't recall ever seeing Don's drawings for his 5"g L & Y 'Aspinall').

Cheers,
Julian

[jma1009]

Hi Dave,

Having now looked again a little more closely at your first pic posted on 12th October, are there only 4 stays between throatplate and inner firebox tubeplate, or have you only drilled 4 so far?

[kipford]

OK some interesting comments. First some back ground on the evolution of this boiler. One of the boiler inspectors for my boiler has already built a couple of Aspinall Boilers so he has a bit of previous! The boiler design has also been modified with the BI’s agreement as follows.

A Reduction of the fire box length by 3 mm to provide sufficient clearance to the rear horn blocks, BI recommendation and he is correct, CAD model shows about 0.5mm.

B Any part threaded into the boiler to be attached using threaded phosphor bronze bushes. (this includes the fire door)

C Move single blow down valve from front to provide two one on each side of the firebox

D Change inner and outer wrapper material thickness from 2.0 mm to 2.5 mm (cost saving)

E Change from threaded side stays to copper rivets. The

F Replace the crown girder stays with rod stays.

The justification for the modifications was presented with respect to the Aussie Boiler Code. I also carried out a full finite element stress analysis (FEA) of both Don’s original design and the new one, although this was not formally presented to the BI’s (a step too far at this time) they are aware of its existence and the results it has produced.

Julian reference your comments. Totally agree about the 3/16” support plates they only add additional support to the backheada and my BI’s would freak over the roughly 30% reduction in water space around that region.

With regards to extra stays, The BI’s have no concerns in that area although we have added an extra row of stays where the outer wrapper necks in. My FEA shows that the stress distribution on the rear of the firebox and backhead is very similar and very low relative to some other areas, but more significantly the displacements are very even showing that additional stays would have no significant effect on the stiffness of the boiler and only present an additional potential failure point. So in summary there is no advantage to adding them.

Note the only stay positions drilled so far are those I have used as tooling holes for flanging.

Picture 1 shows the Von Mises stress distribution for the boiler. The analysis was carried out at the 1.5 Hydraulic test pressure of 930 KPa (135 psi). Note we are using 90 psi not 80 psi as the working pressure, again with BI acceptance. In terms of the a loco boiler like this although the resultant stress’s are important, I consider deflection or displacement results to be more important. The next four pictures show the deflection results. The first shows the whole boiler, note the largest deflections are around the dome, this demonstrates the efficacy of the Aussie code where open holes need to be reinforced and in this case we are adding an external doubler plate (see picture in previous post) as per the code. The area we discussing around the fire hole shows very even deflection. The next two pictures show the boiler sectioned so you can see that the backhead and firebox rear are very evenly deflecting showing the Firehole ring and the stays are adequate.

The FEA also showed that the crown stays needed to upped in diameter from the 4mm min of the allowed in the Aussie code to 6mm diameter. Note we are not looking for absolute values but trends.

Von Mises by Dave Smith, on Flickr
Displacement 1 by Dave Smith, on Flickr
Displacement 2 by Dave Smith, on Flickr
Displacement 3 by Dave Smith, on Flickr
Displacement 4 by Dave Smith, on Flickr

By the way prior to retirement, I was chief designer for an Aerospace Company and have been involved in the design of aircraft structures for over 40 years. The methodology used for the FEA was been checked by my former Senior Stress Engineer.

Dave

[jma1009]

Hi Dave,

That is a lengthy and detailed reply, but it doesn't answer basic stuff as to stay pitch and my query how many you are going to add to the throatplate to inner firebox tubeplate etc.

You also haven't replied to my method I used on 'Stepney' for attaching the fire door assembly. It is on my 'Boxhill' thread later on when dealing with the boiler after being silver soldered up. I will endeavour to provide a few links tomorrow if I have time and if others beat me to it - I am going to be a bit busy tomorrow and Monday as have family staying over.

[jma1009]

My 5"g terrier 'Stepney' has 12 stays on the throatplate of 1/8" dia copper rivets, and stays 15 on the backhead - though on the backhead these are 'specials' and of larger diameter hard drawn phos bronze, to suit my own methods. It is a much smaller boiler to yours. Perhaps overkill on my part, but I recall I think it was Nigel Bennet highlighting a paucity of staying on Don's 7 1/4g" Terrier 'Newport' boiler that resulted in deformation of the plates under hydraulic testing and additional stays being added to the throatplate.

Usually, Don Young was very good with his staying on boilers, and far better than Martin Evans and LBSC, but Don did have a few lapses later on. (My Terrier boiler for 'Stepney' is basically to the Martin Evans design but with much additional staying).

[kipford]

Julian
I was not aware I had to give chapter and verse, I stated I had not drilled all the stays! There are 6 in the throat plate of 4mm dia on 19mm pitch, same underneath the fire door hole at the rear. This meets all the requirements of the Aussie code in terms of diameter, pitch, edge distance etc and my own analysis confirms it is ok at 1.5 x hydraulic and 2.0 x shell test. The fire door is bolted to blind bushes in the back head, the three that can be seen above the fire door in my CAD picture.

[davewoo]

Hi Dave

Apologies if my post, re the pads in the boiler, has stirred something up, it was not meant as any criticism or comment on your boiler in any way, I must admit to not being a deep thinker and assumed the pads were there just to give something to fix the firehole door to, which seemed like a good idea to me but obviously isn't.

Thought it might be of interest as you built your boiler, which seems to be coming along very nicely, very impressed with all the design work you have put in, absolutely beyond me to even attempt.

My drawing experience was four months of my apprenticeship spent bored stiff sat in the drawing office with four grumpy old gits, who on reflection were younger than I am now, and probably just wanted me to go away!

Dave

[kipford]

Dave
No apologies required your post was in good faith and I appreciate the thoughts. Our BI's are very hot on not reducing water space, which I appreciate. I actually altered the shape of the narrow part of the firebox to take into account the 0.5mm increase in wrapper thickness to maintain the nominal water gap.
Dave

[springcrocus]

Oct 16, 2021 22:19:00 GMT kipford said:

Julian
I was not aware I had to give chapter and verse, I stated I had not drilled all the stays! There are 6 in the throat plate of 4mm dia on 19mm pitch, same underneath the fire door hole at the rear. This meets all the requirements of the Aussie code in terms of diameter, pitch, edge distance etc and my own analysis confirms it is ok at 1.5 x hydraulic and 2.0 x shell test. The fire door is bolted to blind bushes in the back head, the three that can be seen above the fire door in my CAD picture.

But you did give chapter and verse, Dave. It's just that Julian didn't understand the answer.

Even I can see that there are six stays to the front throatplate and six under the firehole. Keep up the good work.

Regards, Steve

[kipford]

For further avoidance of doubt and as the boiler is symetrical,  the following two pictures show the position of all the stays for the final design iteration. It also shows a doubler plate around the dome hole to restore the stiffness lost as a result of the hole and follows the Aussie code guidelines for this (which also roughly tally with my industrial experience). The flanges of all the bushes were tweaked where required to ensure code compliance. So if any of our Antipodean friends want to build an Aspinall I have all the drawings for a fully detailed Aussie code compliant boiler available.

Dave

Boiler 4 by Dave Smith, on Flickr
 Boiler 3 by Dave Smith, on Flickr

[ettingtonliam]

OK, you are working to the Australian Code, even though you are in the UK. Is there any known instance where the Aussie code doesn't comply with UK requirements?
I've seen a recent Northern Association newsletter which warns that at least one UK boiler inspector has announced his intention of inspecting and testing boilers in accordance with the Australian code. Northern Association warns that this should not happen and that testing in the UK should be in accordance with the MELG Boiler Test Code 2018, and no other.

[kipford]

I am using the Aussie code for the design requirements, physical testing obviously has to be in accordance with the UK Boiler Test Code. However the boiler test code is just that, it has NO design requirements or guidance on how to meet them unlike the Aussie code. In my opinion as a professional engineer the UK test scheme is acceptable for testing boilers of existing design where grandfather clauses rule. However it should include a section with design requirements and how to demonstrate they have been met in a similar vein to the Aussie code. We should not have to leave it to the Boiler Inspectors who may or may not have relevant competency and their own interpretation of what is an acceptable design.
Dave

[Deleted]

Oct 18, 2021 11:08:40 GMT kipford said:

I am using the Aussie code for the design requirements, physical testing obviously has to be in accordance with the UK Boiler Test Code. However the boiler test code is just that, it has NO design requirements or guidance on how to meet them unlike the Aussie code. In my opinion as a professional engineer the UK test scheme is acceptable for testing boilers of existing design where grandfather clauses rule. However it should include a section with design requirements and how to demonstrate they have been met in a similar vein to the Aussie code. We should not have to leave it to the Boiler Inspectors who may or may not have relevant competency and their own interpretation of what is an acceptable design.
Dave

I agree Dave, I have no experience in building boilers but from what I have been told, the Aussie code allows a safer/stronger design so I can't see why any boiler built to this code should have any issues here in the UK. My own professionally built boiler is built mostly to Aussie guidelines and due to this and 2 extra rows of crown stays (6 vs 4) can work at a higher pressure than drawn by Don Young.

BTW, the boiler looks great, as a pure layman on the subject I'm very impressed.

Pete