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All Pumped up!

Well a definite milestone was reached today; the boiler passed its official initial hydraulic test at 500psi conducted by our Boiler Inspector.

It will never need to be pressed that hard again, next we have a 375psi test with all the ancillaries fitted (gauges, valves, plumbing etc.) then we put some fire in its belly and prove that the safety valves will stop the pressure going more than 10% higher than its 250psi operating pressure – then we will be allowed to insure it and use it in anger!!!

This might seem like a bit of a palaver, but a boiler failure will typically kill everyone within many feet – so it pays to take care.

When you consider that the pressure trying to force each end cover off during the test is equivalent to a large African Elephant standing on it, you can see why it uses a bunch of M16 and M20 studs to hold everything together!

Boiler sitting at test pressure.

500psi on the clock

500psi on the clock

A Few Notes

It took three attempts to get everything perfect, and here are a few notes for other builders:

  • The dome nuts needed to be skimmed, as the imperfections in their surface were enough to produce a significant shower at 200psi as they prevented the dowty seals from working.
  • One of the tubes had not been expanded into the mud drum – that started leaking without any pressure!
  • The stays on the steam drum needed shortening by about 200-thou to stop them bottoming in the dome nuts (it’s a bit of a fiddly dimension, as you must ensure enough thread is engaged with the nuts even with one end completely screwed up to the limit.)
  • The upper end of some of the tubes were a bit long and clashed with the lower stays in the steam drum, resulting in an hour or so with a Dremmel and air-driven countersink, to provide the necessary clearance.

Either way, an important day on the route to launch day!

Boiler Insulation and Funnel

Just a quick note on recent days’ work. We have been insulating the inner boiler casing and installing the funnel (at a jaunty angle)!

The boiler has two casings- one surrounding the burner, tubes etc. (the hot stuff) and an outer one of wood, with an air-gap in-between to keep passengers safe. This also includes a double skinned chimney (also to keep people safe – Lou has quite a scar from another steamboat where the funnel was not lagged or double skinned).

We are using “ceramic fibre board” from Vitcas This is quite expensive, but robust, capable of standing 2,300F (1,250C)  and capable of being cut with a knife or jig saw.

However, the mental gymnastics required to think about how it all fits together inside the boiler I find quite hard. However, after a deal of cutting and trial and error it’s almost done.

Tube nest

As we needed to remove the casing, I also took some pictures of the “tube nest” which shows the 200+ 12mm tubes all expanded into the steam and mud drums.

This lot totals about 30sq-ft of heating surface which is capable of producing about 300lbs of steam at 250psi per hour!


This is formed from some 7-inch stainless steel liner and enamel outer flue. This is what you would find attached to your average AGA.

Boat aesthetics required that this is attached at a jaunty angle (5-degrees) to provide an impression of dashing speed etc. However, making things at an angle is often more difficult than making things straight.

We have made the casing from 3mm steel and this has provided a solid foundation for mounting the funnel.

The inner liner is  178mm dia, so I bored out the hole in the top plate of the casing to size with the head of the mill set over 5-deg to get the required oval (a bit OTT I think).

I opted for a set of 20mm square blocks with their base machined to the aforementioned 5-degree angle and then M5 screws are used to attach these to the roof of the boiler casing to provide a “socket” for the liner.. The inner liner also has a “bulge” about 15mm above it’s lower end, so I machined notches in these blocks to engage with this bulge and thus provide vertical (or jaunty angle) support to.

The outer face of these blocks was then machined to fit the outer funnel, again with the steps providing the angled support. M5 screws thru the outer into these blocks secure the outer funnel. Lastly, a set of three blocks were made to secure the inner and outer funnel together at the upper end, and then an air-nibbler used to chop the inner to length.

Milling at 5-degrees

Milling machine set over to machine oval hole in cover, and inner funnel resting in said hole at required “jaunty” angle!

Funnel mounted on Boiler Cover

Funnel mounted on Boiler Cover

Finishing the Superheaters & Boiler Casing

Work on the Boiler continues with the finishing and installing of the Economiser (pre-heats the incoming water to the boiler using waste heat from just before the flue) and the Superheater (adds energy to the steam on the way to the engine, again using waste heat from the flue gasses.

Milling and Drilling the Econo/Superheater Headers

As noted in the last post, I decided to mill the recesses in the two halves of the headers, as there is a lot of metal to shift, and with the “ripping” milling cutters this was by far quicker. (some pics)….

Milling Recesses in Headers

Milling Recesses

O-ring milling set up

O-ring milling set up

Some finished headers

Some finished headers





Tapping Machine 😦

As there were such a lot of M8 holes to tap (about 48 per boiler) I thought I would “invest” in a tapping head for the mill, and went for a cheap Chinese one – and you certainly get what you pay for… I was worried when it arrived as it appeared to not have a load-sensitive clutch, so decided to try it gently on a test piece… the pictures show how that worked out…

The £^*kin Tapping Head

The £^*kin Tapping Head

Machine Tapping in Action

Machine Tapping in Action

I can imagine it would have been OK with tapping thru holes, but even being as careful and slow as I could, it was useless on a blind hole -sheering the tap instantly. I was just very happy that I snapped the tap in a test piece, and did not scrap a header that I had spent some time (and money) on making… So it’s back to standard/hand mode… and we have a full set…

Back to the old method

Back to the old method

Some finished headers

Some finished headers

Cutting the O-ring Grooves

The final job on the headers is to cut the 4.5mm wide groves for the o-rings that seal the joint between the two halves. I was a little nervous about cutting these in the lathe, as you need to produce a narrow tool with additional clearance to avoid the outer edge of the groove as it is cut.

O-ring milling set up

O-ring milling set up

So, again I decided to mill these, using a small slot drill and the rotary table. This did work, but was slow and tool wear was a problem – I might revert to lathe cutting these for the drum ends.  The setup for milling the grooves was to fit new clamps in the recess before removing the clamps on the rotary table that were holding the header while recess milling (see pic). This meant we knew that the part was still centred on the rotary table, ensuring the recess and o-ring groove were concentric.

With all this complete we just needed to fit the tubes with the same expanding process as used on the main drums.

Boiler Casing

You will recall I drew the parts for the inner casing of the boiler in ViaCAD and then had them plasma cut directly from the drawing; this meant assembly was quite simple. I used M5 rivnuts and screws to make the assembly, spotting through from the plasma cut holes to locate the rivnuts. This went well. I also purchased an American design of tool for fitting the rivnuts, this is based on a pair of wedges which produce the compression to expand the rivnuts. The more normal “pop-rivet” style of tool requires bigger hands and forearm muscles that I currently own!

Completed Inner Casing

Completed Inner Casing

Starting the casing

Starting the casing

Pressure test

The last job is to pressure test the assembly, as the boiler is rated to 250psi, the hydraulic test (with the assembly full of water to avoid any large bangs!) is 500psi. Once we located the one tube we failed to expand (light shower ensues) the assembly proved pressure-tight – which is more than could be said for the plugs and pump, which took several hours of work to fettle to a point where they would stand the pressure. (In the process I became a complete fan of Dowty Seals, which rendered the plugs in the headers pressure-tight with little more than finger pressure inserting the plugs. Here is a video of one of the completed assemblies under pressure (before I cured the leaking pump!!).

Not a bad months work in total…

Tube Expanding and Economiser Headers

Just an update on progress with the boiler and other (interrupting) activities.

Tube Expanding

Nigel was good enough to make the trip north and assist with the tubing of the first boiler.

This was actually a simple, if repetitive, job.

Fitting the tubes

We firstly supported the three drums in the casing end plates, which were temporarily joined with lengths of timber. When fitting the tubes the game plan is to first locate the “centre” row of straight tubes, then fit the outer rows.

In practice there is not enough clearance to insert the first end of the tube with the drums in their correct orientation, so one firstly turns one of the drums in the casing to allow one end of each of the first row of tubes to be slid into this drum, and then the drum can be rotated back to its correct orientation and the free end of the tube inserted into the other drum.   (Hint: Insert them into the mud drum first, we actually started by inserting them into the steam drum first, but they fall out as you rotate this drum).

Once the straight tubes are in place then the outer rows can be inserted by inserting the tube into one drum and pushing it in as far as the first bend, this then provides the clearance to allow the  tub to be swung into place and then you can slide the free end back into the other drum.

Once the tubes are in place you can commence expanding (in fact we expanded the straight tubes into place before inserting the bent ones. Drilling all the holes with a 12.1mm drill actually worked well and provided just enough clearance to allow assembly – any tighter and it would have been a real struggle.

How much expansion?

Before expanding we did the maths on how much expansion was needed. The idea is that firstly you expand the tube to take up the slack between the tube and the hole (12mm OD, 12.15mm hole) so this was 0.15mm on diameter, then you expand the tube by 5% of its wall thickness. So given a wall thickness of 0.7mm this meant expanding the tubes a further 0.07mm. So the resulting ID of the tube was 10.82mm.  We did this by test expanding one tube in stages and checking the diameter, and when it was right we measured the free-length of the mandrel still showing. This proved to be about 20mm, so we then made a 20mm collar for the mandrel which stopped the expanding at the right point.

This worked very well, the load on the drill driving the expander could be heard to change as the expander reached the collar, thus making it simple to know when each tube was tight, without a lot of squinting down the drums. It’s really a two man job, as one needs to hold the tube so that the required 3mm+ of the tube is extended into the drum, while the other drives the expander and “contraption”. A video of the process in action:

We actually fitted about three-quarters of the tubes that we could reach from one end and then turned the boiler around and did the tubes at the other end. It might have been better to work from both ends, as by the time we had finished the mud drums had been pushed out sideways in the casing by about 1mm – no big issue, but information we will use when expanding the other boilers.

One other issue was that the “contraption” and expander proved too long to be assembled inside the smaller mud drums. We solved this by shortening the “chuck” on the “contraption” and by shortening and regrinding the square drive on the expander.

Here are some pictures showing the process. About 14hrs work to expand the tubes for one boiler.


The next part of the job was to turn up the ends for the drum, and also the economiser and superheater ends.

I decided to start with the economiser and superheater ends. Having first drilled another 12.1mm hole in the centre of the blanks for the inner headers (to take one of the super heater tubes), this was initially a simple turning job with the blanks held on a mandrel pre-turned in a 3-jaw chuck – this lead to Interruption 1, the clutch on the Harrison started slipping when confronted with the loads of highspeed turning with the insert tooling I was using. So an hour of so cleaning and refilling the parts washer followed by getting all the oil off  the clutch plates solved the problem.

Then we needed to cut 70mm diameter 12mm deep recesses in the centre of each part – I started by boring one of these, but it was slow work, so I decided to change over to milling these – here two more interruptions intervened in progress. Firstly the Mill started a rather worrying clicking noise from the gearbox – trying to ignore it didn’t seem to work, so I concluded I needed to strip it and investigate, as any major failure would be catastrophic as there very few parts available if anything broke.

Rambaudi Mill Gearbox Servicing

Rambaudi Mill Gearbox Servicing

This was simple to do, but hard on the nerves  – more parts washing, lots of inspecting and new grease restored the machine to full (quiet) operation. I think small bits of dirt and swarf had migrated into the gears and spindle bearings, and the cleaning sorted things.


Lastly, I spent a while trying to resharpen a bunch of broken and worn milling cutters with pretty limited success – so I bit-the-bullet and purchased some new cutters, including a 16mm “ripping” cutter designed to rough out at higher speed – a good choice.

Recess Milling and PCD drilling

I decided to mount the header blanks on a rotary table and then mill the 70mm recesses with the ripping cutter, then remount the blanks on the table with a stud through the centre hole, located between a set of stops to drill the 12 M8 tapping holes using the DRO’s PCD program – nice and simple and accurate. More pics.

A boiler making “Contraption”

More Progress on the Boilers – and a “Contraption”

We now have all the components to commence the “real construction” of the boilers.

Boilerplate and Steel

As you will recall from earlier posts we have drilled the holes in the steam and mud drums, and ordered the plasma cut 3mm plates for the housings from Ashby Welding in Church Crookham, and (after a lot of searching) ordered the 20mm Boiler Plate for the drum ends – which was eventually sourced from Brown MacFarlane in Stoke on Trent with the very capable assistance of  their Account Manager Alan Taylor. So the Landy made another round trip to Hampshire with a good load of steel in the back!

Boiler Plate and Casing Steel

Boiler Plate and Casing Steel

A First Set of Tubes

While in Hampshire Nigel Thomson and I spent a few hours in is workshop making a first set of 5 boiler tubes, so that I could test fit them in the boilers. They all fitted, as the pictures below indicate. So now he and Mark have only 600 or so more to do! (and you can see the plasma-cut end plates from the CAD drawings in an earlier post).

Boiler Drums in Casing

Boiler Drums in Casing

First Tube set in place

First Tube set in place

A Contraption

In order to finally fit the tubes a “tube expander” is fitted into the end of each tube and this is wound into the tube to expand it into the drum, and this secures it in place. This requires that we have a mechanism to reach inside the steam and mud drums to screw the expanders into and out of each tube, and also to drive a countersink bit to clean and de-burr the inside of each of the 1,200 tube holes in the drums. We thought of using a right-angle air ratchet wrench to do this, but having tried this out I decided to opt for a more “traditional” chain-driven tool, that Louise immediately  christened “A Contraption”….

Here are some pictures and a video of The Contraption with some old bloke demonstrating its use, and showing how well it cleaned up the holes in one half of one of the steam drums.

The pictures below show the effectiveness of de-burring the holes on the right-side of this steam drum (and it was quick too)…

Deburred Tube Holes in Steam Drum

Deburred Tube Holes in Steam Drum

Boiler Begins!

Sorry for the long silence, we have been working hard to relocate to Cumbria and convert the garage into a workshop – with that approximately complete it allows me to get started on the boiler for Befur. So this post concerns itself with this topic. Continue reading