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Member postings for Bob Worsley

Here is a list of all the postings Bob Worsley has made in our forums. Click on a thread name to jump to the thread.

Thread: Heating copper boilers
27/10/2020 09:50:20

Not too enthusiastic response, seems no one has ever tried it other than Ed, thanks.

Yes, there will be lots of amps needed, but was just thinking of kW input to see what the figures looked like. Change welding transformer to spot welding transformer. Or just strip the secondary off and replace with just a couple of turns or so. The important thing is the kVA rating of the laminations to carry the power continually. There is a low power requirement, easily managed by a domestic 100A supply, the shower takes far more. It is this low power requirement compared to a gas torch that is the attraction.

With the boiler almost totally shrouded with insulation and with the excellent heat conduction of copper I would expect the whole boiler to be at a similar temperature, possibly only 50C from one end to the other. This solves many of the temperature coefficient problems with connecting the power, but it will need multiple points with 2000A.

I have lots of high power resistors, possibly use them as a hot bed to indirectly heat the boiler but getting back to the gas torch problem. Has anyone used these gas radiant heaters as typically sold by Machine Mart to act as a hot bed? There is a 10kW one, couple of those with thermal shrouding might work.

What did surprise me when I looked in RS was the absence of any high temperature cables, insulation and similar, about 350C maximum, far too low. The idea of using the ceramic cases from fuses has been duly filched from another forum.

Charcoal was recommended as a bedding material in the fire as being clean burning?

Also one of the boiler books said dropping steel clamps in the pickle is fine. Remember being warned never to do that, meant the pickle needed to be changed?

25/10/2020 10:36:08

Another 'why do we do it this way' posts to antagonise and irritate the members of this forum.

Looking at something like a 2" scale traction engine, or probably a 5" loco.

These boilers are large and heavy, and require enormous amounts of heat to reliably silver solder, so need to heat the whole thing to 700C. The whole thing ends up at 700C radiating that temperature.

The problem seems to be that the gas flame is used to heat the boiler, but once the flame has impinged on the boiler it is then redundant. This redundant flame is still at 2000C so is going on to heat up everything around other than the boiler. Talking to people and stories of setting fire to the shed roof, or anything else, are not rare.

What is needed is a heat source that is in the copper. What I suggest is resistance heating using a normal arc welder.

The advantages are that there are no flames, and the whole boiler can be closely insulated to keep the heat in the metal.

Will it work? Copper has a specific heat capacity of 0.38J/g K. So to raise a 1kg boiler by 600C takes 0.38x1000gx600C = 228kJ. 1J = 1W/s so this is 3.8kW for 60s, or one minute.

A real boiler would be 20kg and 700C = 5.32MJ or 5kW for 18 min. This of course assumes no heat loss.

You would need a decent sized, or more than one, welder and because it is slow then need to run them at their 100% rating. Looking through Machine Mart the concept of continuous duty rating seems to have gone. You would also need to use one of the old transformer based welders, no silly electronics saying to turn off.

How to use them? On the barrel to firebox ring joint would need a clamp around the barrel for one lead and two clamps, one either side of the wrapper for the other lead. The current flow will then be all through the ring joint and down the throatplate. Boiler will need moving to do the top and bottom, but need to do that with gas anyway. Just also need to shift the insulating cover first.

The power leads will get hot, 700C, so not your average rubber coating, needs to be glass cloth or something similar. Because the welder is only 30V or so there is no electrical hazard, so bare wire might be ok.

It is also feasible to use some high power resistance wire or resistors under the boiler as background heat. This could be used with a gas torch as well.

Drawbacks? Will be a couple of large cables, taking 200A at 5kW, so quite stiff. Will need some heavy duty clamps for connecting, with AC looking at about 10-15A sq mm connecting area. Clamps possibly need to be connecting to a sheet rather than around the boiler with thermal expansion.

An alternative is induction heating, would be even better but a 5kW induction heater is probably rather expensive. The old transformer based welders are two a penny at sales.

The normal welder used would be AC, so to reduce losses the power cables need to be tightly twisted together, also minimum length. If DC then these worried don't apply. Also modify the welder to fit a number of old computer fans to cool the transformer.


Thread: DRO errors, or are they??
25/10/2020 09:53:21

Zero DRO, grab hold of the toolpost and then as hard as possible push it in, record reading, pull it out, record reading.

Seems to me that the screw or nut are loose somewhere?

Thread: Is Plastow 44T 6D.P bevel gear - 3" Fowler
22/10/2020 11:20:00

This is a general query about bevel gears.

I ave been looking at these for use in traction engines, but wonder why they have to be bevel gears, won't the contrate (as in Meccano gears) type work fine? Ok, not correct to scale, but much easier to cut, and not as if 5rpm is going to worry them. Hidden away inside the differential so not visible anyway.

Thread: Advice required
16/10/2020 18:00:35

The end of the tube belled out?

Easiest is to just use a centre punch and tap it with a hammer. The secret of success lies in making a clamp for the tube by clamping two pieces of steel together and drilling through the join with the outside diameter of the tube. I have only done larger diameters but the hole the same size as the od will grip enough. If necessary put a tiny bell mouth on the hole so the tube splays out.

Holding steel doesn't need to be more than 1/2" wide, I used 1.1/2" by 1/2" but was forming tube up to 1/2" diameter.

For a closing in forming use the same tube clamp but hit it with a Vee shaped hole in the end of a bar, I used a centre drill but you will need a busted one reground.

Thread: capacitance in long cables
11/09/2020 14:03:43

Why not use chips specifically designed to drive and cope with long distance cables?

The obvious choice are the RS232 1488 and 1489 devices. Feed power along two wires and signal on the third.

Thread: Is there any tips for sawing aluminium
04/09/2020 18:15:16

If cutting with something toothed then must use a lubricant to stop it welding to the tooth tip, WD40 is fine.

Any stone angle grinder disc will happily cut aluminium, steel will not work. I know because I cut a CVRT aluminium tank in half to shift it to the scrappy.

The Evolution metal cutting saws are brilliant, the Clarke ones aren't.

Thread: Copper boiler plate flanging, or not?
28/08/2020 15:50:50

Spoke to Reeves, I will try to get some drawings from Haining Steam Models to see what he says.

I have got the Alec Farmer book, but he swears by oxy-acetylene heating, I am not so sure. For soldering the stays OA seems ideal, tight flame and do them one at a time, but still have a 3300 deg C flame.

Don't see that it matters if the rivets bend in the middle, boiler pressure never going to straighten them so they will continue to stay the plates. Besides only 3/8"" or so between the plates so pretty stiff, not much more than the diameter.

Can't find my gas torch, still not got a hearth, progress is slow.

Interesting tests on boilers. Soft solder doesn't seem a good option, but silver solder seems to take almost anything.

Any more? Seems an expensive hobby even at £4 kg scrap value!

27/08/2020 15:42:03

Yes, as Jason says, poke rivet through to the outside, cut a cross in the end, heat to red to anneal, hit with suitably shaped punch to flatted down the four quadrants, silver solder.

Many boilers use rivets but just solder them on the outside, thought that splaying them would provide a similar mechanical hold a a nut.

Just an idea. One day might be able to get along to a club, but not at the moment.

26/08/2020 17:55:46

That drawing is exactly what I was expecting from Reeves, but no, just telling me to return it in an undamaged condition. Snag is they use thick paper from a shredder and it isn't easy to disinter the parts from this paper. Was missing the firehole ring, found it in the wheely bin.

No other progress either, trying to contact Tyler Steam Models to ask about drawings, buy a new set if necessary, but no response to email or phone call.

That photo of the BB boiler is impressive, built and safe! Would probably pass all the safety tests, simply because the copper and solder do make a good joint.

As to the rivet stays, they are 3/16" diameter, what I wondered was cutting a cross in the end, using a four way chisel to splay the ends out flat and then soldering. Different to threading and nuts, but the volume of copper mechanically holding the stay is the same. End of rivet will need to be annealed prior to splaying. Any thoughts?

25/08/2020 10:01:50

JB, don't be worried, I look, read and think. I missed that throatplate overlap probably because at that moment I didn't see it as being important which way round it was made, you corrected that, thanks. But I will say that continuing reading the ME and issue 3781 has the Waverly boiler with this joint the other way round, Martin Evans.

I mentioned I had contacted Reeves about the modified BB boiler. Not much of a reply. But the boiler as they supplied needs a joint ring inside the boiler to join the barrel to the wrapper. This ring is flat material 16" long by 3/4" by 3mm. So will go all the way around the boiler. Being 3/4" gives 3/8" on barrel and wrapper. The water gap between firebox front and throatplate is 3/8". So the ring completely blocks this? I have asked what I am supposed to do. Similarly the side stays are provided as copper rivets, what am I supposed to do with them, different to drawing.

Yes, propane can melt copper, but it can't boil/vapourise it like an OA torch can.

SoD makes some important points about old, out of date, builders or designs? I like copper for boilers though, its cost is only part of the cost of the model, but still less than a miniscule holiday.

Thanks to all again.

Thread: Is a hand scraper pulled or pushed?
25/08/2020 09:43:33

To answer Paul, no, I didn't do the scraping.

At the time, near 35 years ago, I had a friend who rebuilt and mended machine tools, he did it. It was on a Hassison L5A, which I still have and use, bought from Rotagrip. It wouldn't turn anything. Undid the few capscrews to remove the top of the saddle, bit of marking blue, front left, under the chuck, side of the saddle Vee ways no blue for 2-3 inches. Scaped the centre of the Vee ways, only contacts at the ends for 2" or so. I think he used a power scraper but only took minutes to get it done, blued and checked. End result was amazing, could turn to a size, repeatedly.

The difference I see between push and pull scraping is that pushing is digging into the metal, pulling isn't. With a 90 degree end, held at 45 degrees then the angle of the scraper to work is the same. Just seems more controllable pulling.

Thread: 1.0mm 2 flute cutter HSS or Carbide.
23/08/2020 10:50:10

Slitting saw or a couple of hacksaw blades side by side, power hacksaw blade?

Thread: Is a hand scraper pulled or pushed?
23/08/2020 10:47:17

As is usual, after posting this, sat down with an ME off the pile to read and an article about scraping, 15 Jan 1988 issue 3817.

Their scraper, made from an old flat file, the end has the teeth removed and then slightly hollow ground. Use the periphery of the grindstone to put a slight hollow right at the very cutting end of the file. Grind the end with a slight curve and finally stone on an oilstone.

In use the description is "The tool is drawn steadily across the work with slight pressure applied to enable the cutting edge to make the cut.". My immediate reaction was 'ah, it is pulled'.

In use the scraper seems to be held at about 45 degrees to the work, so the 90 degree end face is at the same angle to the work if pulled or pushed.

Must say that pulling makes more sense if you have a handle the length of a chair leg, 20" or so, plus the length of the old file, 12" or so. Internal scrapers can only be pushed but they are hollow ground and the trailing edge touching sets the cutting angle.

Another problem solved! Thanks to everyone who read and contributed.

Thread: Copper boiler plate flanging, or not?
22/08/2020 12:17:57

This is certainly getting some comments! Thanks to all.

My BB drawing is dated "JF/5July 64"and looks exactly the same as the one in the book Model Boilers for Road and Ploughing Engines by John Haining dated 1974.

Nothing in the drawing about extending the sides of the opened up full length barrel, perhaps assumed. I don't have the ME articles describing the construction of the BB, I do for the 16hp single cylinder.

It is ironic that it was the 16hp one I was going to build, but Graham Howard of Brunell Model Engineering decided he wasn't going to supply more than a few of the castings. Paid £2300 for nearly nothing, plus £2500 for a commercial boiler and now got a pile of scrap. At the time I was in serious arguments with a planning department and knew if I met Howard there would be a death, so time now expired to take him to court.

The Minnie boiler is done with a short barrel and separate wrapper with ring, perhaps copy that?

I don't want to give the impression that this particularly worries me. But, I don't belong to a local club, Stamford or Melton, due to virus, I have not made a copper boiler, I have bought two Minnie kits to practise on, hopefully one with unflanged plates, in the end it has to be acceptable to the inspectors.

I will go back to Reeves to put the points to them, including the change to 10swg/3mm for all the copper.

I have also made comments about using oxy-acetylene. Just come across an article to send shivers up your back from ME 2 May 1986 number 3776 about just that, a 3.1/2" Britannia with combustion chamber. A beginner, using O-A welding gear, leaks everywhere, cut boiler in half to repair, burnt copper, solder run everywhere, repaired and joined back together and passes all tests. I obviously can't copy and paste the article here, but the mods might find it a useful exercise. I have to say that it is this that frightens the daylights out of me.

After reading so much, and this forum, I think now that copper is a safe material to make a 100 psi boiler from. Why? It is malleable and ductile, the flanging give a huge safety margin on the joints, propane can't damage the copper, silver solder is a safe material because if the joints are too larhe then it simply won't join. If the boiler is going to fail then all these make it fail slowly, it will tear or pull apart. Actually rather impressive. Apparently LBSC tested a boiler to destruction but no issue number where the results are given, can it be found and added this thread please?

Thread: Workshop Equipment
21/08/2020 17:00:58

It was my opinion.

It was a series of decisions I made when upgrading. Take it or leave it.

No one has commented on the testing of the lathe. I am not surprised, the number of times I told people at exhibitions that a readout is just an accessory, doesn't do anything for accuracy, and not one, not one, person ever came back and said they had tried it.

Keep an eye on the auctions, nice machines for just a few hundred, got to move it though!

Thread: Capillary gaps required for silver soldering.
21/08/2020 16:53:26

My apologies to duplicating this thread.

I have asked the same question starting in June in the Workshop Techniques forum.

I also am confused, still.

I have never made any boilers, just about to start though.

Thread: Is a hand scraper pulled or pushed?
21/08/2020 16:42:43

I have got scrapers, many collected from auctions and both flat with a slight curve on the end, triangular with relief between the corners and curved again with relief between the edges.

I never was able to get them to do anything.

Reading old ME's I cam across an article about some pne scraping a flat surface and said get an old file, grind the teeth off the end, slightly curve then, then bang the tang into a wooden chair leg so it would fit over your shoulder.

There are endless articles on the web about scraping, but so far I have not come across one that tells you that you PUSH the scraper, or PULL it!

This is only for flat surfaces, such as fettling a lathe saddle, for bearings then you use the triangular and curved ones and PUSH them.

What do the experts say? It could be that my scrapers are too small, blade about 8" long, handle similar, but nowhere near the 24" chair leg.

Thread: Copper boiler plate flanging, or not?
21/08/2020 13:02:29

It gets worse.

There have been some mentions, and many more elsewhere, that the boiler needs to be made to a published design otherwise you have to sort the safety factors out. \

Just bought a Fowler BB boiler set from Reeves. It turned up as a short length or tube plus a firebox wrapper and a jointing ring. The plans say the tube is one solid piece from smokebox to backhead.

Contacted Reeves to ask for the amended drawing, not available, besides it is common now to supply the wrappers as a separate piece of copper.

This is not as the designer designed it.

Where does this leave me?

I was also somewhat surprised that the barrel, wrapper and all the firebox copper was 13swg, not 10swg. This is as the designer specified, but whilst not exhaustive the other plans I have seen in ME all call for 10swg, 3mm, on 2" scale engines. Any thoughts? Should I chuck these pieces and get some 3mm?

Thread: Workshop Equipment
21/08/2020 12:55:39

My two pennyworth.

I had a South Bend, like the Boxford, and access to my dad's ML7 when I bought another lathe.

Three things drove me to drink with the SB and M7.

1 - That the chucks were held on a screw thread, meaning that grief had to be imparted to get them off. A lathe with a taper fitting, my Harrison has an L2 taper, or the newer Camlock type are really worth the cost.

2 - That the SB etc had a spindle bore that seemed to allow only a pencil to go through it. The Harrison has 1.3/8" and that I would say is a good size.

3 - That some form of quick change gearbox is essential. My Harrison has a full Norton box, but the alternative of just three speeds or pitches is worth its weight in gold. I do almost no threading other than at 48tpi, so changing gears wouldn't be too much of a pain. But feed rates are a completely different thing, and being able to quickly change is essential otherwise you just don't bother, and power feed finish is so much better than by hand.

Don't dismiss secondhand, look on,uk for a changing selection.

To test a lathe do the following. You will need a micrometer reading to tenths of a thou, or 0.002mm, preferably the fiducial type.

1 - Get a bar, 25-30mm is fine, of free cutting steel in the chuck. Even brass will do.

2 - Get a round nosed tool, needs to cut equaly well to the left and right, with a nose radius of 1mm or so.

3 - With a parting off tool cut two grooves in the end of the bar. One about 10mm from the end and the second another 10mm from the end of the groove just cut. Both grooves need to be about 3mm deep.

4 - Set lathe to run at a suitable speed with a feed rate no coarser than half the radius of the tool.

5 - Position tool in the outer groove with a depth of cut of 1mm at least. Clamp cross slide so it can't move.

6 - Set feed direction to the left.

7 - Start lathe and cut to the left until reaching the inner groove and stop the feed, leave lathe running. So this has surfaced the bar with a 1mm depth of cut.

8 - Quickly move the carriage to the right until the tool is in the outer groove. A spiral cut will appear in the just machined area.

9 - Stop lathe, reverse feed direction to the right, start lathe.

10 - Engage feed so the lathe now cut the bar to the right. When off the end of the bar stop the feed and the lathe.

11 - Measure the diameters of the two sections just machined, one to the left, one to the right.

12 - Weep.

What you have done here is check the saddle for skew as it moves under a small cutting load to the right and left. If the readings agree within 0.01mm then the lathe is good, normally it would be 0.1mm or even worse.

Try this on a new lathe in the showroom and see what excuses are brought forth.

On a second hand lathe, Colchester, Harrison and similar, the bed is hardened and the wear will be in the saddle, not hardened, so it can be scraped out. My Harrison had an error of about 5 thou, but after scraping it is 2-3 tenths.

Good luck!

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