The first 6 minutes of the video is getting up to 40psi. Then a couple of minutes of the engine working. Big file, so be patient.
The first 6 minutes of the video is getting up to 40psi. Then a couple of minutes of the engine working. Big file, so be patient.
You are probably fed up with my burner trials. I certainly was.
Fundamentally, I was trying to get enough heat into the Trevithick model dredger engine boiler, and just not managing it. My boiler is a scaled down version of the original, in copper. It takes a lot more heat than the 6″ vertical boiler which I made last year and I think that the reasons are…
So my colleague Stuart suggested that I try his Sievert burner…
This unit raised steam from 2500cc of cold water in 10 minutes, and got to 20psi in 14 minutes. The target of 40psi was reached in 18 minutes.
At 40psi the safety valve operated, and despite continuing to pour in the heat, the pressure did not rise above 40psi. So I am expecting that the boiler inspector will be happy with the safety valve.
I then ran the engine for 45 minutes, turning the boiler feed pump on and off to keep the boiler water level up. All went well. I have made a video of the event, but the upload failed last night, so I will try again later.
Next, to contact the boiler inspector for the final (I hope) inspection.
First I tried the Sievert 2943. I tried different gas settings, and different positions of the burner in the fire box. I quickly discovered that an opening had to be present next to the supporting flange. Despite that, steam was produced in 10 minutes, and 20psi was achieved in 15 minutes. My aim is to obtain 40psi, and maintain 40psi during engine operation.
Unfortunately this burner does not work if there is any significant back pressure in the system. Stuart has advised me to try the Sievert 2954 which he says will cope better with back pressure. The Sievert 2954 has a similar appearance to the 2943, so I have not photographed it.
I have borrowed a Sievert 2954, but it needs some setting up, so I thought that meanwhile I would try a burner style which had been mentioned earlier. It is a tube with multiple transverse slots. Despite being constructed rather roughly and quickly, it produced a good hot flame. Perhaps a bit small, but promising.
If the next Sievert is not satisfactory I will come back to this style, and experiment with different slot numbers and sizes.
If you are becoming a bit bored with all of these gas burner experiments, I understand. When the burner is finally sorted I will be delighted and relieved.
I have machined some wood to be used for lagging. It is West Australian Jarrah. A dark coloured wood which is often used for exterior flooring. I will apply it to the boiler soon.
The Trevithick dredger engine model is almost finished. Currently applying some paint. And getting it ready for the final boiler inspection. I am guessing about 2 weeks.
I have chosen a spot in the house where it will sit, and will post a photo in due course.
A few people have been asking if I have decided what to make next. In terms of a major build, the answer is no, I have not decided. I have considered a few possibilities. Those possibilities include a model of Stephenson’s “Rocket”, Trevithick’s “Catch Me Who Can” or “Pen-y-darren engine”, a Shand-Mason fire engine, or even another cannon.
What I will do, is to complete several unfinished projects, and if a major project becomes obvious, imperative, then anything is possible.
The unfinished projects include…
Looking at that list, I really do not need to start another major project.
And sometimes it is nice to sit back, and enjoy the glow and satisfaction of previous projects. It does sound rather self satisfied, no? So here is a selection of videos, mostly first runs of newly completed projects. Most are YouTube links, but one or two will run directly.
This was the first model steam engine which I made about 5-6 years ago. It is a Bolton 7 single cylinder mill engine, and this was the first occasion I had run it on steam. It was a very exciting moment, seeing it actually running on steam.
Next came the Bolton 12 Beam Engine. Still a crowd favourite. The beard was ordered off by SWMBO not long after this.
Then a couple of Stirling engines. How they work is still a mystery to me.
Then the problematic, difficult triple expansion engine, which took 3 years and several extended breaks to get to the working stage. Still not finished completely. Stuart Tankard’s boiler. Since then I made a vertical boiler.
And somewhere in there I made this little reversing engine for the club competition. Alas, it failed in action.
And 3 cannons came out of left field. They started as a CNC project, but then took on a consuming interest of their own. About this time I saw the necessity of learning how to put together a video. Still learning.
And finally the Trevithick dredger engine. The historical aspects of this engine, the genius of Trevithick, the fact that the engine works…. has been marvellous. The engine is looking quite different with some paint applied. And the propane burner is significantly better than appears in this video.
So, if you are still with me after all of those videos, congratulations on your stamina. It is therapeutic to take stock sometimes, and to wonder about where making all of these engines is going. It was not to any plan. Still no plan. Just enjoying the moments, the days.
Firstly some pictures.
So, I have reassembled the engine and the burner and the base.
Did you notice the base?
No? Excellent. That is the idea. A nondescript matt black base which is barely noticed.
Yes? OK, well it must be OK.
Then a trial of the burner inside the firebox, using the changes which have evolved over the past few days.
During the video I am constantly changing the propane flow, and there is a clear “sweet spot” point where it looks really good, and feels very hot. I have not yet tried to steam with it.
I was drilling a hole in the end of the Trevithick burner today. The burner was securely held in the vice, but the heat annealed brass was not as strong as the torque in the 6mm drill bit.
I still have the wooden forms which I used to make the burner originally, so, roughly twisted the part back into shape. It was pretty malleable still. Then forced it into the wooden form. And beat it into shape with the copper hammer. This was looking promising.
Tapped a 1/2″ x 26tpi thread, and assembled the burner.
My reader/advisor Huib, suggested filling the tube with stainless steel scouring wool, in order to improve the flame.
I asked SWMBO, and was directed to the appropriate supplier.. the local supermarket.
It has improved the flame; there is no back lighting of the jet itself, and there is a more even flame along the length of the tube. I think that I will be able to improve the flame further, but will wait until I can test it inside the boiler itself. In the video the roaring of the flame drowns out my voice somewhat. You will not miss much. I am varying the gas control.
So, sorry about the voice track. The stainless steel stuff is interesting. It is like swarf, but not sharp. I wonder how they make it. I imagine that it works in the gas-air tube by creating swirls and eddies, and better mixing the gas and air, without impeding the flow much.
Back in the workshop tomorrow. A few connectors to make, check the feed pump, then make an appointment with The Boiler Inspector.
By the way. The parcel opening post was apparently not very interesting, so I wont bother with that format again. I am aware that my video technique was pretty ordinary, but I am not inspired to try that one again. Pity. I enjoyed making that one.
The gas burner on the modelTrevithick dredger engine has been more problematic than anticipated. In the absence of published information about gas jet sizes, air hole sizes and numbers, the effect of a ceramic cover, and firebox size and shape, I have resorted to trial and error. Having read many of the comments on the subject in Model Engineering web sites, I can see that most other builders adopt the same approach.
I have lost count of the number of changes which I have tried. These are the ones which I can remember.
Concurrently while experimenting with the burner, I have been applying some paint. SWMBO insists that I am a hopeless painter, but I think that it is going on OK.
Looking at yesterday’s photo, the yellow flame indicates inadequate air for the amount of gas going in. The air holes at the gas jet level were already at maximum size, so I drilled some holes in the burner base itself.
So the next step was to remove the ceramic burner, and make changes to the spreader tube beneath.
The ceramic burner broke in pieces during the removal. Possibly still useable.
But I thought, maybe I will see what the flame is like without the ceramic burner altogether.
And this is what the flame looked like…
Now, that is more like it! (you can see the holes which I drilled in the end of the burner to increase air intake)
Admittedly, the flame will change when the burner is back inside the boiler, but this is the most encouraging flame yet. Minimal yellow. The gas flow will need to be reduced.
Next session, I intend to experiment with the hole sizes and number and angles. I do not expect to be using the ceramic insert in the final version.
Well, I was really not expecting this.
After all, the engine was running well on compressed air at 30psi, and the burner appeared to have a good flame.
And Stuart was coming to be involved with the big event. So nothing could go wrong!
I set up the iphone on a tripod. Checked the light. Oiled the bearings and slides. Filled the boiler. It takes 2 litres of water. And hooked up the propane. when Stuart arrived I lit up the burner, and sat back to see how long it would take to raise steam.
Some steam leaks were expected, on this first steam run. Leaks don’t show on compressed air, unless they are severe. As the water heated up, some leaks appeared. The water feed clack valve and the sight glass were bad. The clack valve just needed some goo. Later I disassembled the sight glass, and cleaned the valve, with some improvement, but more work needed. Or a new sight glass valve. A couple of other trivial leaks were easily fixed.
So we watched the clock, and checked the temperatures. Ot took 20 minutes to start raising steam. That is a bit slow. Eventually it reached 20psi, but the pressure refused to go any higher, despite fiddling with the gas and air controls.
At 20psi, I opened the throttle and gave the flywheel a swing. You can see the result.
After that, we let it cool down and fixed the clack valve leak. The sight glass valve leak was looked at later, but could not be fixed simply.
The burner was definitely not up to the job, so in this last video, it got some assistance.
It does go! Just needs a few tweaks. Lovely sound.
I know that this blog is titled “johnsmachines”, but I do get interested in “other stuff” too.
I came across this video on YouTube yesterday. It runs for 4 hours.
The footage was shot by an amateur astronomer, through telescopes which anyone can buy. A 9.5″ Celestron reflector (Schmitt Cassegrain I think), and an 80mm Orion refractor.
I used to be an amateur astronomer, and still retain an interest. One of my worst decisions ever was to give away an Orion 10″ reflector about 10 years ago.
Anyway, back to the video. It shows the surface of the moon, concentrating on some interesting areas. Following are some screen shots. It is titled “Live Moon Surface Observation”. Worth a look. Suggest jumping to 28minutes and watch maybe 5 minutes, zooming in and out.
Earth’s moon is strange.
It is the largest moon in the solar system relative to the parent planet.
It is much less dense than earth.
(why? if it is made of the same rock). (5.51g/cm vs 3.34g/cm. Thought to be due to Earth’s metal core.)
It almost exactly blocks the disk of the sun during a lunar eclipse. Coincidence?
The other side of the moon always faces away from earth. Until the space program, no human had ever seen the other side of the moon. The other side, incidentally, is quite different from the side which we see. Much more cratered, no large flat areas. Presumably most meteors come from the direction away from the sun (because they are scooped up by the gravitational field of the sun).
One moon day is exactly the same length as a lunar month. It is the only moon in the solar system where this applies. That is why the other side of the moon always faces away from earth. Another coincidence? (correction. Pluto – Charon also exhibit this behaviour, so it is not unique, just unusual. Thought to be due to “tidal locking”- thanks Gene).
OK. I know. You came to this site to look at my machines, particularly the Trevithick dredger engine. I am still fiddling with small details which are not very photogenic, but necessary before I run it on steam. Currently hooking up the boiler feed pump.
Not real happy about this one, but it is necessary if I am to run the dredger engine in public, at club meetings etc.
The original dredger engine had 3 taps to check on the boiler water levels, like this.
Unfortunately that setup is unacceptable for boiler certification, so I have installed a sight glass using the same penetrations.
The sight glass is a bit short, but it should comply with the regulations.
I have spent another half day experimenting with different spring configurations, so that the safety valve releases at 40-50psi. Eventually I decreased the coil pitch of the spring, and the valve now releases at 45-50psi. That will do.
I have no intention of modelling the dredger, but in making decisions about the engine base have gone back to the sources to find out about the gun ships. These are referred to as “gun brig”, “bomb-ship”, “hulk of a dismasted ship”, in letters by Trevithick and others.
The first three of these dredgers were recorded by Trevithick as being 80, 120 tons and 300 tons.
And this is the diagram of a cross section of a bomb-vessel from a century before Trevithick. It is mounting a 13″ bore mortar. Note the massive supporting beams. You can see why Trevithick chose this type of vessel to mount his steam engine and dredging machinery.
Now that I have a tripod for my video camera (an iPhone), I have become a bit more enthusiastic about making videos. Terrible standard of video compared with Joe Pieszczynski, and This Old Tony, and Stefan Gotteswinter, but maybe better than just text and photos. I will be interested in your responses.
The Dredger Engine is still not quite fully made, but while I had the video set up for the spring making exercise yesterday, I added the following. It is totally unscripted, and unedited, so there are errors. “pressure valve” instead of “pressure gauge” for example. Have fun counting the errors. The final 30 seconds is me having difficulty turning off the camera!
I was attempting to model the Trevithick Dredger Engine as true as possible to the original. But, I also wanted it to run, so the flywheel would spin and the crosshead move up and down and the unusual valve control lever flick up and down.
There are several problems with this approach.
I had a full day in the workshop yesterday, so I had better front up and straighten those steps for SWMBO. Actually, it will an interesting job. I will use a 4WD high lift jack(s) under the house to free the steps, then use the Landcruiser winch with a snatch block to pull the concrete steps into position. Might be worth a photo. How the steps ended up out of position is a mystery.
The feed pump is attached to the base, and since I had not decided on the final form of the base I had to leave the pump sitting all alone on my messy bench.
But I have now decided to proceed with a wooden base, made of 32x32mm hardwood beams, and a solid wooden top to which the engine and the feed pump are attached.
So today I attached the feed pump. The engine itself is still just sitting, not attached. And the bits of the base are still a loose pile of beams of wood, not bolted glued or screwed together.
One minor problem was that there were incomplete dimensions on the plans for the feed pump and its supporting column. Fair enough. I assumed that the dimensions would be measured on the job.
First I had to make the steel beam which attaches to the cross head, and the column at the other end, and the pump… 3 attachment points. I had cut out the beam last week, but it needed a couple of bends. It was 4mm thick steel, so I did the bending in the workshop press.
Of course one of the bends was too angular, so a bit of cold blacksmithing to flatten it.
And fitted everything to the engine sitting on the base.
Then the penny dropped. The holes in the base should be the same as the corresponding holes in the steel beam… 32mm. so I filled one of the holes with epoxy filler, redrilled it, re-tapped it and reassembled everything.
Next to make the pipe between the feed pump and the boiler feed pre-heater, and a bypass tube with valve. I have not decided on the size or form of the water supply tank. A riveted squarish tank, or even a riveted cylinder would be nice. Probably make do with a plastic bottle for the time being.
I also need to fasten together those base beams. Have still not decided how to do that.
There are 4 types of wood in the base. I might have mentioned one or two of them. One is the top, one is the beam under the front of the boiler, the base beams is another, and there is a sizeable block underneath everything. I doubt that anyone will be able to identify all of the wood types. 2 are Australian, one is European, and one is Asian (I cut up a breadboard for that one).
And thinking about a colour scheme. Flat black is the favoured colour in most other models, but I want to include some Georgian reds blues greens or yellows. And leave a bit of brass and copper for polishing.
Oh, and I made a ring for the top of the chimney. Seen in the second pic.
Reader Huib suggested that I would need to modify the gas burner for my model steam engine even before I had tried it.
He was absolutely correct. The burner was difficult to light and keep going, unless I blocked off at least half of it. (see previous post).
So, today, I modified the burner along the lines suggested by Huib.
And this was the result. The burner li up easily when gas was admitted.
I measured the temperature of the burner, and it was 790ºc. I think that it will do nicely. After that, I sealed the fire clay burner into the brass container with a high temperature boiler sealant.
Yesterday I received in the mail a tiny pressure gauge. 3/4″ diameter, 0-80psi. from EJ Winter, Sydney. Order was placed Wed, arrived Thurs. Great service. Thanks Ben deGabriel.
Trevithick would not have had a pressure gauge in 1803, but modern boiler regs insist on one, so I have bowed to the inevitable, and will install this gauge on top of the boiler. Photos to follow. I expect to be running the engine on steam next time I am in the workshop. WooHoo! Not tomorrow though. Baby sitting.
Quite a few potential workshop days are being foregone because we in southern Oz are experiencing a very hot summer. And the few more moderate temperature days are “lost” to essential jobs for SWMBO, and around the house. Shouldn’t complain about the weather. Townsville, Queensland, where my brother and family lives, has been declared a disaster area due to torrential floods… 1000mm (39″) rain in the last few days, with more on the way. And the next ice age has apparently started in USA.
But, back to the workshop for a few hours here and there, I have made the boiler water feed pump for the Trevithick dredger engine. As usual, I grossly underestimated the time these few simple components would take to make.
The pump is driven off the crossbar where the stroke is 100mm (4″). At the pump, the stroke is ~17mm (~5/8″). The suction side has an 8mm (stainless steel) non return ball valve and the delivery has a 6mm non return SS ball valve. The plans specified a dummy pump, for appearance only, but I have made it functional.
The 2mm ss cap screw is to limit the ball movement to 0.8mm travel. Something less conspicuous will replace the cap screw. Probably a ss grub screw.
The rod driving the pump piston is a piece of bronze brazing filler rod. Just happened to be the correct diameter.
I will need to add a further pump, hidden somewhere, for boiler approval. It will probably be a hand pump.
The next step is to design and make the stand for the engine. The plans specify a large, and in my opinion – ugly, wooden box. So that is not on my option list.
Most of these “dredger” engines were used in factories and mills. Some were used to drive mine pumps, and a few were used on dredgers. In the factories and mills they would have sat on masonry or wooden bases, and on the dredgers they would have sat on the very solid decks. (the dredgers in some cases were converted gun ships, designed to mount large black powder cannons, mortars or seige guns, so they were very solid!)
Now, some pictures of other dredger engine models, and the reconstructed full size one, and their bases. I have numbered the pictures, and I would be interested in my readers opinion about which would best suit my model. Please leave a comment.
After the debacle of the valve sleeve rotating because I had not secured it, I secured it with a grub screw, and had another attempt at running the engine today.
But before that I shortened the valve lever blocks by 2-3mm. I had noticed that air was entering the cylinder well before top and bottom dead centre. Shortening the bars delayed the entry a bit. Still a little bit before TDC and BDC, but watch the videos to see the result.
So, it is still not finished, and the timing will need some fine tuning. But it works! Phew..
It works in forward and reverse, depending on piston position when it starts, or if the flywheel is given a initial swing.
In the above videos the engine is not bolted to the box, and some of the noise is the cranks hitting the box. The valve arm being hit by the striker is also contributing to the noise.
I will work on the gas burner next.
The flywheel and driving gear both are attached to cranks which join the connecting rods to the mainshaft. It is important that both cranks are attached with the same angularity. Seems simple. The cranks are identical. But small taper holes, through brass and silver steel.
Drilling the 2 holes took most of the day.
Figuring the setup was the biggest challenge.
First problem was that the 2.5mm drill bits were not long enough for the chuck to clear the gear. I did not have adequately small ER collets (would have required ER8’s), but I did have a Dremel chuck which was small enough. But no spindle for the Dremel chuck. The Dremel chuck has a really odd thread. I measured it at 40tpi, and 7.05mm diameter.
So I made a spindle. Thank goodness for CNC threading.
Dremel chucks are convenient, but they are not very accurate. Fortunately, once the hole was centred, the drill bits and reamer seemed to follow the centred start. Here I am about to ream the hole which has 3 steps 2.5mm, 2,8mm, and 3mm. The shop made spindle is held in the milling machine drilling chuck.
I took the reaming very gently, not wanting any broken bits of high speed steel stuck in the workpiece…. and all was well.
So I sat back and enjoyed one of my Xmas presents. Ah! Bliss!
The deWaal plans for the Trevithick Dredger Engine call for a 30mm diameter lead ball for the safety valve.
I considered substituting steel or brass, and turning the ball, but lead is almost 50% more dense than the other metals, and that could be detrimental to the functioning of the safety valve, so I worked out how to make the ball in lead.
I have previously cast lead balls 14mm diameter, but this is significantly bigger. I did briefly consider making a plaster of Paris mould, but I could find no balls of the correct diameter for the POP mould, so I decided to mill the mould.
On rummaging through my big milling cutters, I discovered that I have a ball nose cutter, 31.75mm diameter. It was part of a package of cutters which I had purchased years ago, and almost forgotten. I had bought the cutters BY WEIGHT. I think that I paid $US5 per pound, and I bought 20lb. Mostly the cutters were resharpened end mills, but one of them was an unused 31.75mm ball nose. Pretty close to perfect for this job!
Only one part for the day’s work again. But it was a LOT OF FUN!