Clarkson 5" A3 Rebuild

[coniston]

Finally managed a bit of time in the workshop today, glad of the break from all the garden remodelling.


I finished the steam pipe adaptor by machining a flat at 15 degrees each side for the two connections, I borrowed an idea Steve (Spring Crocus) showed in his build of using a vice held in another vice to get the parts at an angle safely without having to hold the piece by the corners. After machining the flats I drilled then through at 5/16" and counter bored 7/16" for the two threaded spigots.




And checked the fit was ok.





Then held the parts together with some wire after adding the flux and a silver solder ring, gave it a blast with the Sievert torch and watched the silver solder flow neatly round the joint. Inspection inside showed perfect penetration with the solder showing visibly all round the end of the spigots.








Tried it on the loco and all looks good.




Made the first of the two union nuts from 3/4" bronze, didn't have any of that size brass.





That's it for today, hope to do a bit more in the workshop before I have to get back onto the garden buildings project.


Chris D 

[coniston]

Squeezed a bit more time yesterday and today to finish the steam pipe adaptor. Finished the second union nut then made the nipples, these are just flat faced, same as the one that came off, to make separating the pipe work just that bit easier. No 'O' rings, just the flat face, worked before so should work this time.




I then made a 90 degree union for the oil inlet which is screwed 1/4" x 40 with a lock nut to be able to position it in the most convenient way. I milled a flat on the adaptor and also took the opportunity to turn a bit of the body away just to make it look a bit neater.





You can see from this view with the smoke box in place that there is a 1/4" hole between the blast pipe and the steam pipe, this is where the oil connection comes through from underneath. 


 


I can have the oil union either facing forward toward the smoke box door or behind, but I think if behind the oil pipes will be a real pain to couple up. Anyway I can wait until later to decide on that.



Next job will be to bend the super heater steam pipes round and cut to length to meet up with this adaptor.


Chris D

[springcrocus]

Jun 11, 2020 21:41:46 GMT coniston said:

Squeezed a bit more time yesterday and today to finish the steam pipe adaptor. Finished the second union nut then made the nipples, these are just flat faced, same as the one that came off, to make separating the pipe work just that bit easier. No 'O' rings, just the flat face, worked before so should work this time.




Chris D

No critisism, just interested. Is there any reason why you chose this approach over the traditional sixty degree nipple? Very little movement needed to move the pipework with a nipple but much longer contact on the angled face for a good seal.

Regards, Steve

[coniston]

Hi Steve, as the original had a flat face and seemed to work I thought I'd give it a try. Although when first fitting the pipes they are relatively easy to move around I have found after some years of use they are more difficult, particularly if they end up close to or touching the inside of the smoke box. Any way I'll give it a try and see how I get on.

Thanks for your interest

Chris D

[jma1009]

Steve,

Chris has adopted the correct approach with smoke box joints for the elements with flat nipples as opposed to coned nipples.

A blower pipework will have a bit of 'give' in it and is usually coned nipple and female connection to match.

The superheater and steam pipe assembly has very little 'give' in it so the flat nipples are usual in this case. (I have always turned up these flat nipples from hard drawn phos bronze, but that is fancy on my part).

Cheers,

Julian

[coniston]

Another step forwards this afternoon, I cut and bent the steam pipes from the dry header to meet up with the adaptor. Not silver soldered the nipples on yet, that'll be the final job on the super heaters.



And all connected up.



Chris D

[stevep]

Excellent access to the tubes.

[coniston]

Thanks Steve, I am trying to make it as serviceable as possible in all various thing I am doing, smoke box access is always difficult but at least this one has a 6" inside diameter so I can get a hand in there.

Chris D

[coniston]

Getting a bit of time in the workshop again so first job was to silver solder the union nipples onto dry steam pipes from the super heater, sorry no photo. This finishes the super heaters until I make the regulator and steam pipe and finish the tube plate bush so I can mark and drill the holes for the studs holding the super heater wet header flange.

On my loco as originally built the blower steam is fed from a valve in the cab through the dummy vacuum pipe outside the boiler to the smoke box where there is a union inside to connect the blower to. I am keeping this solution so no longer need to fit a blower valve and tubular stay as shown on Don Young's drawing. I am replacing it with a typical screwed rod stay with intern/external threaded nuts each end.

I didn't have any 1/2" hexagon bronze bar so machined some 5/8" gunmetal bar to size. I use a 5C collet spin indexer as it is easier and quicker to set up than my rotary table and as yet I don't have one of those nifty hexagon and square collet blocks I've seen being used.

Clocked it up to within a thou then taking a 20 though cut off all six sides, measure it across the flats then divided the difference by two and used that on the feed screw dial to get it to size. Pleased that it ended up just 1/2 though under 0.5"









Then into the lathe to turn the outside for 5/16" to 3/8" diameter, using a split die opened up as far as the holder allowed I put a slightly oversize 3/8 x 40 ME thread on the outside. Then drilled and tapped 1/4" x 40 ME to 5/16" depth. Finally parting off with a 5/32 long head.



And this is the two of them finished.



I'm using a length of very thick wall 1/4" copper tube with 1/8" bore as I don't have 1/4" rod long enough, this is 30" long before trimming to length. As it is the same material as would be used for a blower stay I don't see a problem with it. I threaded the first end with the 1/4 x 40 split die opened up again in an attempt to get tight fitting threads. A bit tricky trying to line the tube up to get it through the bush until I hit upon the idea of putting a piece of welding wire through the tube plate bush with the tube inserted from the back head end and the two meeting under the regulator dome opening, it then became very easy.





I just need to mark and cut the tube to length, thread it and screw the whole lot together with a bit of sealant on the threads.

Chris D

[don9f]

Hi Chris, those hex and square collet blocks are extremely useful.....I don’t think I’ve used my rotary table since getting them! Saves such a lot of time not having to remove the vice from the mill etc.

Cheers Don

[kipford]

Chris
+ 1 for the Stevenson Collet Blocks. I have one of each as well, both came from ARCEurotrade.
Dave

[coniston]

Gosh, I cannot believe it has been 4 months since last working on my A3 rebuild. Finally got some workshop time so carrying on with boiler fittings. Next logical part is the regulator, to the Don Young design. Made of three parts silver soldered together, the body, steam pipe fitting and the valve port face. First up is the internally threaded steam pipe fitting, just a simple turning job in Phos Bronze internally threaded 5/8 x 26 TPI.




Next part is the body which is 3/4" square x 1 3/16" long. I have a length of 1 3/4" diameter phosphor bronze which I used, firstly sawn a length off the bar and faced each side to end at .750" thick. Then onto the milling machine to square it off at .750" square.




Not too bad a finished size




So these are the embryo parts so far, just need to bring the length to 1 3/16" before milling out the insides.




Hopefully more to follow this week

Chris D

[coniston]

Bit more on the regulator body, firstly I drilled a couple of holes to 1" depth to remove some metal before milling the main steam throughway which as drawn is 5/16" x 9/16" but typical Don Young no specific depth given. I has to meet with the outlet spigot, the bore of which is 3/16" from the bottom, so 1" deep it is. I also decided to mill the pocket which the second port lets steam into as a 3/16" deep pocket rather than the sloping design Don has, just to make the milling operation a bit simpler without the need for another set up.

Here it is to the depth of the shallower pocket, the clearing drilled holes can just be seen.




And here it is after milling the deep pocket with a 1/4" end mill, now squaring the corners as much as I can with a 1/16" FC3 cutter (which I broke just after this photo was taken) The cutter is held in an ER11 collet chuck which is then held in the ER32 collet chuck as I dont have a small enough ER32 collet and this set up gives a bit better view of the cutting operation.



This is as far as I have got, next up is to drill / bore for the outlet spigot then drill across for the operating arm pivot. The eagle eyed will notice that early on I managed to turn the Y axis the wrong way and put a small indent into the top surface. At least this wont matter as the actual port face is a separate piece silver soldered on top.



Chris D

[coniston]

More progress on the regulator this afternoon, hole bored for the steam outlet spigot and hole drilled for the operating arm pivot and a start on the separate port face which is to be silver soldered to the top.

Centring the regulator body for drilling and boring, I use a home made 'wiggler' tool that locates in a centre pop on the workpiece and due to the relative lengths magnifies the movement at the tail stock end, pretty easy to get the part centred as the 'wiggler' provides real time indication of the workpiece movement. It is made from a 7 inch length of 1/8" silver steel mounted in a ball joint from an old car tailgate gas strut.




After boring the hole to 5/8" the next job was to drill for the operating arm pivot.




These are the two parts so far






Started milling to size a piece of cast gunmetal for the valve port face using a tungsten carbide end mill which gives a lovely finish, well it does compared to my less than sharp HSS end mills.



Hopefully a bit more tomorrow

Chris D

[coniston]

Finished the valve port face for the regulator today, milled it to size (well not to length until after the slots were finished), so now ready to silver solder the three parts together. I have left some metal on the port face to mill it down to size once silver soldered to the block as I'm sure some distortion will happen.

Started the 5/32" ports by drilling 4 off 3.2mm holes using index dials on the mill for coordinate drilling, the scribed lines are there as a check to ensure my calculations are right. I have a 0-5/16" keyless chuck mounted on a 1/2" parallel arbour which I can quickly put into the collet chuck saving time and hassle changing chucks which I don't like doing often as it is  MT3 in the spindle and whacking the drawbar makes me cringe about what damage it is doing to the spindle bearings.






Then I used a 3mm FC3 cutter to open the ports to size. I haven't squared the ends as shown on Don Youngs drawing as I don't see there is any real benefit in doing so for the miniscule area lost.






These are the three parts ready for silver soldering.





Chris D

[coniston]

A little bit further on today, the body assembly has been silver soldered together, although I'm a bit p****d off the top valve port plate moved a bit during the process which I didn't notice until I had finished, luckily I can live with it not being absolutely aligned to the body and I'm not risking trying to get it spot on now, it is parallel with the direction of movement which is the important bit. Also a bit of stray silver solder managed to fasten the holding wire into the cross hole so that needs running a drill through to clear.




Started on the slide valve by bringing a bit of cast gunmetal to size although still a bit more to come off the height as you'll see from the scribe mark.




For comparison this is the regulator that came out of the original steel boiler next to the new one. You will see that the steam port is much smaller on the original, I believe the Don Young design will be an aid to achieving a free steaming loco (hopefully)






Chris D

[coniston]

Moving on with the regulator slide valve, I had left some material on the depth of the valve so it is easier to grip in the vice for the first operations. First thing was to mill the clearance for steam to get to the port, this is 9/16" wide, I used a 10mm carbide end mill to get to depth then took it out to width each side.




Next operation was to put the slot across that takes the operating spindle, this is drawn at 5/32" wide with full radius at the bottom ending 1/64" above the top of the port face. As I have a 4mm ball nosed slot drill I am making the spot and spindle 4mm which is a couple of thou over 5/32. Firstly I used a 4mm FC3 cutter to mill the slot to the centre of the bottom radius.



Then bottomed to depth with the bull nosed slot drill. I didn't want to use this for the complete operation as it is a long series one and knowing my luck I'd probably snap it off.



Here it is so far on top of the regulator, it is designed to be wider than the body and it will have a small chamfer both sides as shown on the drawing below.



And here's a photo of the drawing to show what it is supposed to look like.



Chris D

[coniston]

Finished off the sliding valve for the regulator this afternoon. Last operations were to bring the valve to correct depth, cut the steam access slot in the middle, chamfer the bottom sides to bring the face to 3/4" wide from 13/16" and shape the front and back, more for appearance and weight reduction than anything else I can see.

After I milled the bottom face to depth (thickness) I started the slot by drilling 3 x 4mm holes (each end and in the middle) then used an FC3 cutter to cut the slot to 9/16" length (or width depending on how you view it) before using the same cutter to take 15 though off each side opening it to 3/16" wide. You may notice from the drawing it should be 5/32" wide to match the slot in the port face, more on that below.

you can see the three holes as I start to open the slot.



And once to depth and length, widening it to 3/16"




When I took it out of he vice I realised my mistake by not filling the cross slot where the drive pin will operate, I closed the vice a bit too much and squashed the valve. Luckily I managed to hold it half in the vice and tap it back straight (well near enough) before finishing the face with 600 grade oil soaked wet and dry on the surface plate. Bit of a moment and must remember how soft cast gunmetal is in future.

I decided to only chamfer the front and back rather than follow Don's design as I felt there would be too little metal left to provide sufficient strength and I really don't want the valve to break when in service. This time I machined a piece of aluminium to a snug fit on the main slot to prevent it closing up. 



And once the small chamfers were milled (1/32" x 45 degree) on the edges of the working face it looks like this:



You can just make out the small chamfers in this end view, making the port face the same width as the body.



The reason I made the central steam access slot 3/16" wide instead of 5/32" is to hopefully provide a more progressive opening of the regulator. As designed the valve opens both ports at the same time, there is no progressive lead as seen on other loco designs. From experience of driving many different locos I can say that a smooth progressive regulator will prevent wheel spin and sudden take up of rolling stock, making a much more comfortable experience for both driver and passengers. If you're not careful you get into a cycle of open and shut regulator, a bit like kangaroo petrol in the car.

I know from talking to a long time friend of Don's who built a number of his designs, that as a designer he favoured a 'sprightly' performance and many if not all of his designs feature (suffer from?) a sharp opening regulator. 

as an aside Don Young drove my actual loco at Southampton before he penned Doncaster, apparently he felt the loco lacked performance and subsequently spoke to Clarkson offering to redesign the A3 to improve it. As would be expected Clarkson refused which I guess prompted Don to proceed with his own drawings. I'm sure that Doncaster will out perform my Clarkson version, but I am trying to make some improvement to the steam distribution to hopefully end up with a satisfactory loco. Another club member at Fareham built the Clarkson Duchess, and although that one also appears sluggish it certainly does pull very well, a bit like a tractor rather than a racing car, just keeps chugging along.

Anyway back to the regulator and in the following pictures you can see the effect of making the steam access slot 1/32" wider, I also increased the the valve length by 1/32" to compensate.

This first picture shows the slot just uncovering the port whilst the front port is still closed off




Now the slot is uncovering the port  by 1/32" the front of the valve is just opening the front port



And when the regulator is fully open both ports are completely exposed.



I don't think it will be necessary to increase the valve travel as the should be sufficient 'land' on the port face for it not to return to the fully forward position. In my case this doesn't really matter too much as I am using a normal screwed gland at the back head and not following Don's close to scale design so I don't have the same restriction on angular movement.

All I need to do now is to lap the valve and port faces to achieve a nice steam tight fit then on to the operating pin, pivot and links.

Chris D

[Deleted]

Excellent work Chris...now if only you had built a spare...

Top work sir...

Pete

[coniston]

Nov 3, 2020 22:26:02 GMT @greenglade said:

Excellent work Chris...now if only you had built a spare...

Top work sir...

Pete

I nearly had to make another, the number of errors that crept in, but managed suitable recovery strategy . Now I've made the mistakes you can make yours perfectly, bit like the rest of your build.
Chris D