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Member postings for Evan Lewis

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

Thread: Steam engine from scrap metal
22/11/2020 12:29:17


Does that look better? I tapped the steam passage and redialed it, reducing the size from 8 to 4 mm and thus reducing area and volume by a factor of 4. I hope it works better.

Thread: Ball ended handle - how to
22/11/2020 11:47:18


The first turning job I ever did when I inherited this lathe was to make a new cross-slide handle from stainless steel. The firs lathe project in 55 years. The plan was just make something that works. It doesn't have to look authentic.

I like the way it feels but it is not balanced. Unless the gib adjustments are tight the handle drops down to the lowest point due to gravity. So that's what the balls are for. I knew there was a reason we have balls! Gravity. So now I am thinking I have to make a bigger ball, like the song "I like big balls". Maybe if I made it from solid gold it would be heavier.

Thread: Steam engine from scrap metal
20/11/2020 22:16:40

Thanks to you both again. Last night I threaded an 8mm brass bar, tapped the passage hole and glued it in with superglue. I considered cutting a keyway groove down the side but decided to drill it afterwards. we will se how that goes! I like your idea of a plain rod with a flat on the side best. I still have 3 more to do so I will try that. Yes, the link should be very helpful.

I don't have the material for the crankshaft yet. I would like to make it from stainless so that it doesn't rust. It is much harder to work with. Am I asking fro trouble?

20/11/2020 02:31:55

Thank you Jason and Byron for these useful tips with such great detail. I should have checked with you before building the cylinder block. Now I am stuck with my ignorant decisions!

In conclusion:

  • The valve cylinder diameter should be about half of the main cylinder diameter.
  • The valve piston should be lapped in and no O-rings used.
  • The main piston could have O-rings as specified by Jason. No preference for stainless, brass or bronze?
  • The bearings for the piston rods could also have O-rings.
  • I plan to put a cap on the back cylinder heads to accommodate the piston rod as it protrudes. I think it will need to have an internal diameter larger than the rod, otherwise it will work like a syringe, creating pressure.

I plan to tap the biggest passage which runs parallel to the cylinders and fill it with threaded brass. Then re-drill the passage 3-4mm diameter, and closer to the main cylinder so that they will be covered properly by the head. My main concern is that using a small drill close to the cylinder may go off course and curve around into the cylinder wall. This is a particular risk if I am drilling through the edge of the threaded plug. I do have a small reamer. Any suggestions there?

Thanks again!

19/11/2020 10:41:16

Thanks for your advice Jason. I am surprised because I thought these ports and ducts were too small and didn't imagine it would be much of a problem if they were too big. What happens with the large size? Does it have difficulty maintaining pressure with the large volume.

You mentioned specifically running on steam and that suggests to me the problem may be caused by the steam cooling down, and the huge mass of the cylinder block wouldn't help with that. Yes the large passages would slow the steam passage. But the pressure seen in the passages would be the same as the pressure produced by the boiler if the passages are large enough (?)

If it is a volume issue I suppose I should insert sleeves in as many areas as possible? I can't change the ports themselves as that would require re-boring the valve cylinders yet again.

The valve cylinder size was supposed to be half the final result of 20mm. I had some manufacturing problems. I did not figure out why, but on one occasion the cylinder turned out larger at one end -cone shaped. The boring bar must have moved. I bored the cylinders and THEN drilled the ports leaving serious burs inside so I had to bore it twice more. Again I did not think that the passages being too big would be a problem.

Yes friction may be an issue, especially with O-rings. I may leave the valve pistons plain and even the main pistons too -depending on what advice I get from you and other experts. Of course I can always take it apart and add O-rings later.

Thanks again.

18/11/2020 23:57:49

I have the option of making the pistons from bronze or stainless steel. They will of course be running in the brass cylinders. Which material should I use?

I also have 1/4 inch brass rods for con-rods but I see model kit sets often use stainless. I am thinking of turning down to 6mm so that I can use a 6mm reamer for the con-rod bearings.

18/11/2020 23:50:49

Thanks Neil for the timing tip. I knew I had to find out the exact phase difference. It will be adjustable by moving the eccentric cam on the crankshaft which will be held in place by a grub screw. So 90 degrees plus 10-20 degrees advance will be the starting point.

I assume the advance is to cushion the change in direction as the piston approaches top dead center?

I have read about steam lap and exhaust lap, but not sure what effects they have. Not sure about the role of "lead" either. Do the following numbers seem reasonable?

The ports are round, 6.5mm diameter (originally planned to be 8mm) and the valve pistons 9mm long by 20mm diameter. If these pistons are placed so that they are centered over the two inlet ports when the valve piston assembly is in the mid-position, this will give symmetrical laps of (9-6.5)/2 = 1.25mm. ie steam lap=1.25 and exhaust lap=1.25 with stroke length 24mm.

I have not made the piston assemblies yet. If I put O-rings on the valve pistons it might affect this behavior if the pistons are not a tight fit. Should I use O-rings. If not the design will be subject to decreasing efficiency with wear.

I plan to have two eccentrics for forward and reverse operation with a sliding control added later.


Edited By Evan Lewis on 18/11/2020 23:55:13

18/11/2020 23:35:40


VERY rough sketches.

Steam galleries:






Side walls and internal "Walls" which support brass sliders (20x5mm brass bars) centered on the cylinder axes:






Showing the walls and slider bars




Rough 3D Sketch

Possible cross-head sliders shown at top left. 



3D Sketch - an early version




PHOTO of the brass block covered with engineers blue, mounted with 3 bolts on the compound slide of the Boxford A lathe. This uses a purpose built boring bar holder in the 4-jaw chuck. The position of the boring tool is fairly easily and accurately adjusted with a dial gauge.

Note: You can the motor I installed recently. It is a 180 volt DC motor out of a treadmill with a Chinese pulse width modulator HQ-SXPWM-X speed controller.  It is very nice to use!





PHOTO of the finished brass cylinder block. That is all I have made so far.



Yes it seems spooky and a bit weird for Newbies. I could not see how to make an album which was required for the camera icon above, but the icon next to it allowed me to link to photos on my web site and they showed up on my posts.

Anyway I finally found my way to albums and created one by uploading the same photos. For those having trouble seeing them I will display them again using the album!




Edited By Evan Lewis on 19/11/2020 00:11:25

Thread: Testing Models
18/11/2020 10:42:21

Hi Byron,

I was interested in your mention of Doble: "I thought I would compare this turbines performance with that of one of Abner Doble’s steam engines that was probably one of the best ever put in a car. ". The engineering Co A&G Price Foundry I was talking about had a license to male Doble steam buses for Auckland City. Would they have been turbines?


18/11/2020 10:36:07

Hi Byron,

Thanks for your reply. I was interested in a comment in the thread that the turbine jets go "sonic" at 25 psi. I suppose this is the pressure at which the fluid velocity reaches the speed of sound and cannot go any faster. Is that correct. I did similar calculations for the Hero engine and concluded that it occurred at 10-14 psi but I may not have taken into account all the factors such as the increase in density as pressure increases. I was very surprised that it occurs at such a low pressure even if is 25 psi. Because the Greeks probably could not deal with high pressures my Hero engine had a pressure relief valve set at 15 psi.

Are you able to explain in simple terms why the Hero reactive turbine is so much less efficient than other turbines which are so efficient that they are used in nearly all oper stations. I wrote an article on the history of a local engineering company, A&G Price and they claimed that their Pelton wheels were 90% efficient. Using the data they provided I checked their calculation and it was correct, but I don't know how reliable their data was.

I have started building a double acting 2 cylinder horizontal steam engine from scrap metal using only a lathe. I put a post under the heading "Stationary Steam Engines". I read the above posts about measuring the effectiveness of piston seals under pressure. For simplicity I am thinking of using O-rings for piston seals. To keep friction down I understand they would be fitted loosely. I imaging they should only just touch the cylinder walls with no perceptible compression. Is that right? The main cylinders are 22mm diameter so I would by O-rings with 22mm outside diameter but they are sold by inside diameter so 18mm rings 2mm thick would do it. Is that right? Then the grooves would be 2mm deep I think.

I am using pistons as valves instead of the usual flat plate so that I can do it easily on the lathe. The valve cylinder is penetrated by numerous ports: 2 steam inlets, two exhaust ports, and two ports leading to the top of the main power cylinder. They are round holes drilled rather than slots. Can I use rings on these valve pistons too or will they get torn up by the ports? Ideally the valve pistons should seal along their whole length but two O-rings or any other kind of rings would not do that.

Our hardware shop says they can get two kinds of O-ring: Nitrile eg N70 which are recommended for temperatures up to 90 degrees C, and red Vitron up to 200C. I assume I would need the Vitron type.

You may not want to read more and this is just an aside: I bought a BMW X5 second hand at 100,000km. It leaked water like crazy but passed a pressure test by three different organizations including AA. My radiator man found that it had 5 O-rings from China that had gone soft and gummy, completely flattened. Replacing them fixed the problem and he said this was very common with Chinese O-rings. But why did it pass pressure tests? They were associated with the expansion chamber which is part of the pressurized system. I think they must seal under pressure and leak when the pressure drops.

Thanks for your help.


Thread: Steam engine from scrap metal
18/11/2020 05:55:31

I just drew another sketch of the steam ducts and galleries which I have already drilled in the cylinder head shown above.

I have also realized that if I obtain a 50mm diameter steel bar I can easily achieve the 18 mm offset I need with my 5" 5-jaw chuck. So i will be able to make the crank shaft from a single piece.

Sketch #6: The steam ducts and galleries that have already been drilled into the cylinder block.

18/11/2020 04:21:32

Thanks for the tip GL. The brass block shown in the photo above is the only part that I have made so far. The rest is in my head and some rough sketches. Since you requested visual representation I have added my sketches here but they are VERY rough.

This is a photo showing the cylinder boring process with the block of brass (covered in engineers ink) mounted using 3 bolts on the compound slide.

Incidentally you can see the DC treadmill motor I just installed with variable speed control 2.5 HP at 4700 RPM motor speed.

A photos of the boring bar holder in the 4 jaw chuck for boring cylinders

This 3D sketch shows the cylinder block, two main pistons near the center and two valve pistons towards the sides. Steam ducts are shown for the piston on the right. Intake and exhaust galleries are not shown here.

Rough sketch of planned engine design #1

Sketch #2 includes the cross head and crankshaft. It top left I sketched two types of cross-head slider and plan to use the design to the right. Probably made of bronze.

Rough Sketch

The following is an image I took from an animation in Wikipedia and this has been the basis of my design. I altered the slide valve to make it look more like a pair of pistons. The gap in shaft shouldn't be there! I said the valve pistons would be 180 degrees out of phase with the main piston, but this is adjustable and an approximation.

Rough Sketch #3

This is the end view showing the "walls" between all 4 cylinders with a brass bar on the top to act as slider surfaces for the cross-head. The 4 cross heads will be about 25mm square and 10mm thick with grooves cut down the edges to run on the brass slider.

Rough Sketch #4 - End View of the cylinder block with slide rails

Plan view showing the walls and the brass sliders will be mounted on top and screwed to the walls. I have reduced the thickness of the walls to 5mm aluminum bar.

Rough Sketch #5 Plan view

17/11/2020 12:45:32

The valve piston works exactly the same way as a D slide valve and the cross section of the piston assembly is exactly the same as the cross section of a D valve. It consists of two pistons, each 9mm long with only 5mm space between them. Steam galleries 6.5mm diameter were drilled from the ends of the cylinder block, straight across the valve cylinder and into the steam gallery described above. Then the holes in the end of the block were tapped and blocked off with 8mm stainless steel grub screws. That is why the 6.5 mm drill was chosen.

The biggest flaw with this design is that the steam galleries are too small. And the large mass of brass will take a long time to heat up resulting in condensation. A third problem is that I have read that you should not use brass with steam because it will corrode. I am not sure how quickly that occurs and wether it is really a problem for a model.

The diameter of the ducts is restricted by the limits of the valving system. I was surprised at how precisely this has to be made so that the inlet and exhaust valves do not open at the same time. Usually slots are used to increase the steam flow. At one stage in the design process I was going to have two sets of these galleries for each piston but forgot about that when I actually came to make it! See photo. Since the holes are 6.5mm and the valve pistons 9mm there is 2.5 mm total overlap giving 1.25 mm steam lap and 1.25mm exhaust lap but i have not been able to find any documentation on how to design the lap. It may be too much? When the main piston is at the mid-point of the cylinder the valve pistons occlude with inlet and exhaust ports.

I have not decided on rings for the pistons. I was just going to manage without rings but that may not be wise, so I think I will use O-rings but could use some tips and tricks to work out how deep to cut the grooves. Should I have rings on the valve pistons - they would have to pass over numerous port holes and might get torn up? Also the valve pistons would ideally be sealed along their whole length.

Also I have not worked out how to seal the glands that the con rods pass through. O-rings here too? Placed inside the bearing surfaces?

So now I plan to bolt flat plates on each end of the brass bar as a frame with a brass plate for the floor screwed onto the under side of the walls. These walls will support the crankshaft. Then I will place additional 3 walls between the cylinders and mount brass bars 5x20mm across the tops of the 5 walls to make a T shape 100 mm long for the cross heads to slide on.

The cross-heads will be about 10mm thick (is weight a concern?) with grooves milled down the side. I do not have a mill but have a milling attachment for the lathe. (Otherwise it could be made from 3 plates screwed together.) The connecting rod will screw into the crosshead and the "swing rod" which connects to the crank shaft will require a wrist joint.

I plan to have double eccentrics for each cylinder so that they can be connected to a C-shaped slot controller to provide forward and reverse and variable power. But in the first instance I will just use one of them to make it a bit simpler until I am sure it will work.

I do have some scrap bronze and all the bearings and cross heads will be made from that.

I also have some interesting scrap I got from a scrap dealer in NZ. This is 80mm diameter solid round bar about 500mm long which he gave me. It was attached to a plate 100mmx10mm and the same length and I was able to remove it. It appears to be very hard magnetic stainless steel but the Menz Shed has an electric hacksaw which will cut off disks.

At first I assumed I would be able to make the crankshaft out of a single block but with 36mm swing it is too big. I can just fit the 80mm bar into my chucks but cannot set an offset to turn the bearings for the big ends. So I have decided that I will have to cutoff and face 3 disks and drill holes to place shafts for the big ends. I do not know how they will be kept in place. Probably pins drilled across the holes. Any suggestions here would be helpful. I think that threading these joints would not be sufficiently accurate or rigid. Can it even be done?

Any advice that you can offer would be greatly appreciated!

17/11/2020 12:45:15

I went to a scrap metal yard in TN, USA and they had a solid round brass bar 75mm diameter by 2 meters long in the scrap! I bought about two feet of it (600mm). Also a rectangular bar 50mm x 38mm and I bought about 600mm of that too. It was only $2.80 per pound. I cut 150mm off each and brought it in my hand luggage back to NZ in January. What to do with it! I used up the round bar making involute spiral cams for the drop hammers in the stamper battery and produced huge amounts of swarf!

My Mac is so full of stuff that I didn't have room to install CAD software so I just drew rough sketches freehand with a blunt pencil on the knee. Too shocking to publish!

Well I decided to build this steam engine using the rectangular block. I drilled 3 holes across the center so that I could bolt it to the crompound slide. Put a quarter inch steel plate underneath to center it and used a dial gauge to line it up. I tightened two of the gib screws to clamp the compound and cross slides. This meant that I could bore all the holes on the same plane. I made a boring tool holder for the 4 jaw chuck and used it to bore two main cylinders 22mm diameter with a planned stroke of 36mm and piston length of 10mm.

I bored two cylinders for the valve pistons which ended up 20mm diameter after making the mistake of boring before drilling the port holes which left terrible burs in the cylinders. So I had to bore them again. I wrote in my notes "drill before boring", but with weeks passing between stages I forgot about that!

I drilled steam galleries parallel to these cylinders placed between each main cylinder and valve cylinder, but not passing right through, and drilled similar holes on the other side part way through leaving metal blocking the mid-portion.

The plan is to make heads that duct the steam from these galleys into the main cylinder heads. That way the piston can reach the end of the cylinder without getting fouled up with a port.

I have a good drill press and used that to drill vertical holes from the top of the block - one near each end of the valve cylinder to act as steam inlet ports, and a single hole at the center as a steam exhaust port. This should be bigger as the steam expands so I drilled right through the block so that steam can exit from both the bottom and top of the block. Again I could have drilled holes side by side to act like a slotted port, but I am concerned that all these ports may damage the piston. I was going to make the pistons from bronze but perhaps I should use stainless.

Edited By Evan Lewis on 17/11/2020 12:58:33

17/11/2020 12:44:07

Hi everyone,

I have already made the cylinder block for a two cylinder, double acting steam engine. I have just read through "Steam Engine Number One" and found that and many other posts useful. And I have watched just about everything I can find on YouTube and read Wikipedia. I am doing this whole project with a lathe and decided to use piston valves which came into fashion about 1900 instead of the slide D valves used before that.

I am not an engineer because I failed to get into engineering school and became a doctor instead sad. My father taught engineering at Te Puke High School in New Zealand and I was in his class for 4 years doing engineering theory, workshop practice and technical drawing in the early 1960's.

When Dad died recently he left me a lot of tools and a lathe that he bought from the school: A 1955 Boxford Model A. I now have that set up in my car garage. I do have a propane-oxygen welding torch. It is adequate but there is no spare space for more equipment. I do not have a compressor but think I will need one to test the steam engine. I use an old propane tank flushed out and filled with compressed air at the petrol station (NOT recommended). I have made about 32 YouTube videos about how to use and overhaul the lathe. (under the name evan-e-cent or evanecent : see Playlists on steam engines and using an engineers lathe).

My first project was to build a Hero steam engine (designed by the Greeks 2000 years ago) and calculate its power output and efficiency documented at (there are some numerical errors in the text shown on the video.)

On the same web site I wrote software for working out what gears to use in the gear train to cut any thread, metric or imperial, and to calculate feed rates (see

I built a model of a gold-mining quartz stamper battery and that worked out very well, but is not on YouTube yet. (see my wife's web site for a video of a small battery). The plan is to possibly use the steam engine to drive this battery.

Cylinder block for a 2 cylinder steam engine made in a lathe.


Edited By Evan Lewis on 17/11/2020 12:54:15

Thread: Testing Models
17/11/2020 06:48:17

I found this discussion very interesting. Thank you! I have done some similar calculations for a Hero engine which I documented in a web site that you might find interesting, although I think your knowledge is much more advanced than mine. I am now building a double acting two cylinder steam engine and was interested in the results for different types of piston seals. I will post that separately.

Thread: Boxford needs new motor.
08/06/2020 13:03:01

Another user on the Boxford Users group is looking for a motor for his Boxford and you may be interested, but to be honest I think you have covered it all here.

Don't forget to get a lingkbelt too as you don't want to be stripping the head down unless you have to!


Thread: Online free software for calculating change wheels for South Bend clones
08/06/2020 12:51:26

This is a new program which I wrote to determine what change wheels to use to cut imperial or metric threads on any South-Bend clone lathe with or without a gearbox. I have a Boxford Model A with gearbox. The software is free and readily available because it runs online. Yes it really is free. The URL is currently case sensitive:

Corny names tend to be easy to remember and search online! Contact me by email and tell me what you think.

Thread: Evan Lewis from New Zealand
08/06/2020 12:47:10

New program to determine what change wheels to use to cut imperial or metric threads on any South-Bend clone with or without a gearbox. I have a Boxford Model A with gearbox. The software is free and readily available because it runs online. Yes it really is free. The URL is currently case sensitive:

Corny names tend to be easy to remember and search online! Contact me by email and tell me what you think.

I am not sure which thread to add this to for promotion. It would be good if you would allow me to post it on several; Machinery and computers and old machinery types would be good. I think I will go ahead and you can delete if you consider it inappropriate. I am only trying to provide a free service which should be helpful.


The new Boxford group is thriving with a lot of active discussion going on. I have not seen any abuse etc. It is great and very helpful.


Thread: Paint recommendations
08/06/2020 12:29:48

I painted my old Boxford lathe with one-pot epoxy ultra blue. It is Australian Wattyl Rustkill. Nowhere near the original color but I'm happy.

Someone else said that I had chosen the idea type of paint. as good as two pot. I left town for a year and when I came back it was hard asa rock.

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