Author Topic: Amateurish Engine  (Read 2108 times)

Offline Jasonb

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Amateurish Engine
« on: May 29, 2023, 04:42:36 PM »
I think I first saw the image below of this engine when it came up on Pintrest and it caught my eye. A bit more digging about with Google showed that it originated from the May 1881 edition of "Scientific American" and was listed under Amateur Mechanics as a "Simple Single-Acting Steam Engine"



I manages to find another engraving that showed an end view and side view sectioned through the cylinder with a couple of other details of the valve but that was too grainy to be of much use. There was also a basic description of the engine and some key sizes. One feature was the use of brass tubes for the cylinder and piston that would telescope together thus saving having to bore the cylinder and machine a piston on a treadle lathe that it was assumed most amateurs at the time would have.

It was said to be approx 1/20 HP and had a bore of 1.5" x stroke of 2" and an 8" flywheel. I set about drawing it up to suit some thick wall brass tube that I had for the cylinder and that dictated that I use a 19mm bore so my metric design is about half size. I also altered some of the construction methods suggested and also added a bit more elaborate detail so that I would not make it too quickly.

For example the text suggests that the plate supporting the cylinder be sandwiched between two threaded rings with the threads being hand chased and the assembly then being soft soldered together. I opted to make the plate and the two rings as one then fix to the cylinder with Loctite. Strangely it suggests the cylinder head is a casting with what looked like cored passages, I opted for an inserted sleeve to form the ports for the rocking valve's spindle to rotate in. Rather than brass on brass I opted for a piston machined from steel.



« Last Edit: December 11, 2023, 03:47:11 PM by Jasonb »

Offline A7er

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Re: Amateurish Engine
« Reply #1 on: May 29, 2023, 06:32:00 PM »
Can you adjust the amount of "throw" on the concentric?

Offline Jasonb

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Re: Amateurish Engine
« Reply #2 on: May 29, 2023, 07:07:00 PM »
No, just the timing relative to the crank pin.

length of Eccentric rod is adjustable to allow alteration of how much inlet/exhaust is opened.

I could not decide from the drawing if the lever that actuates the valve was slotted or not, that would have a similar effect to altering the throw of the eccentric but I went with a fixed point. It's not that common to be able to alter eccentric throw on a steam engine particularly a "simple" one so I did not allow for it.
« Last Edit: May 29, 2023, 07:16:48 PM by Jasonb »

Offline A7er

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Re: Amateurish Engine
« Reply #3 on: May 29, 2023, 08:19:59 PM »
Apologies for getting the terminology wrong!
I did a google search on the Scientific American magazine for 1905 and they seem to be available for download as a PDF. There is a log in required, so I don't know if it's easy or not. If you knew what month or issue the engine was in, that would make it easier. You might have already done the search yourself, if not this is the address.

https://www.scientificamerican.com/issue/supplements/1905/09-02/

Offline Jasonb

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Re: Amateurish Engine
« Reply #4 on: May 29, 2023, 08:36:58 PM »
Article in pdf form

Offline Jasonb

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Re: Amateurish Engine
« Reply #5 on: May 30, 2023, 06:27:04 PM »
As I mentioned in the opening post I wanted to add a bit more detail and ornamentation and the rather plain flat plate of the original engines base was the first candidate for that. I have had a couple of images of this engine in my "future projects" file and likes the edge detail it featured.



So after milling some 5mm plate down to size and drilling the various holes I started by using a 10mm cutter to do the recesses along the edges



After that the plate was held upside down and a dovetail cutter used to chamfer the edges to a height of 4mm which left a small 1mm vertical edge around what would be the bottom.



I deliberated for some time on whether to stick with parallel columns or to taper them, in the end straight won so it was just a case of turning spigots on each end that were threaded M4. Two bases were turned with a bit more decoration to the profile and then parted off over length.



The feet were attached to the longer bottom spigots with Loctite and once set were faced back to give the finished length from underside of base to the shoulder at the top of column



For the cylinder support a piece of 8mm flat bar was held in the 4-jaw and bored to 22mm then the integral upper collar formed by turning 2mm off the face of the bar.



I took the option to profile and drill the two holes on the CNC but it could also be done easily enough with a rotary table. This is a good example of why someone would want a good range of different height parallels, with 8mm stock and a 6.5mm depth of cut having the right parallel so you are only holding the bottom 1mm of the stock ensures you should not cut into the vice jaws.



An old arbor was reused to hold the work while the thickness was reduced to 4mm leaving just the lower collar standing proud by 2mm.






« Last Edit: May 30, 2023, 06:34:06 PM by Jasonb »

Offline Michael S.

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Re: Amateurish Engine
« Reply #6 on: May 31, 2023, 08:29:38 AM »
Hello Jason,
an interesting project. A simple machine and yet with a lot of refined controls. A good start.

Michael

Offline Jasonb

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Re: Amateurish Engine
« Reply #7 on: June 01, 2023, 08:37:15 PM »
The piece of thick wall brass tube that I had came out at 22.7mm by the time the chrome plating had been skimmed off so I opted to use a M22 x 0.5mm thread for  the gland nut that seals the end of the piston (no rings). I opted to make the female thread first and rather than single point cut it I took the opertunity to have  ago a thread milling on the CNC. So an odd bar end of 1" brass was held in a 3-jaw chuck, the end milled flat and then the threading size and smaller clearance hole were bored with the CNC followed by thread milling.

<a href="https://www.youtube.com/watch?v=5Y58fe95IFw" target="_blank">http://www.youtube.com/watch?v=5Y58fe95IFw</a>

With the internals done I cut a test make thread on the opposite end of the stock and screwed the gland nut onto that to do the remaining turning, the final operation was to use one wheel of a diamond knurl to add a rope type knurl to a half round bead that had previously been turned.



With sufficient length sticking out of the chuck the chrome was turned off the other end of the tube and then a 12mm length reduced to 22mm dia which gave a shallow shoulder to locate against the cylinder support plate. Following that the thread was cut, I find it easier to run the lathe backwards and bring the tool in from the far side, that way I can cut at several hundred rpm and not have to worry about overrunning the length of thread if I don't stop the lathe when required



After checking the fit of the thread using the gland nut as a gauge I bored out the tube to the desired 19mm diameter. It was then sawn off and the top faced back to final length.






A piece of 20mm leaded steel was turned to fit the cylinder and then bored out to 17mm to leave a 1mm wall thickness, sawn off, faced to length and a 3mm hole put into the top ready to receive the small end yoke.


Offline Jasonb

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Re: Amateurish Engine
« Reply #8 on: June 03, 2023, 07:32:31 PM »
At this stage I was enjoying the building so much that I did not take as many photos as I could have done but there is nothing too special about most of the remaining parts.

The crank disc was roughed out and then a RCGT 06 button insert used to finish the back edge and give a nice large fillet to the protruding boss and then the hole was spotted, drilled 5.8mm with a stub drill and reamed 6mm before sawing the disc off of the piece of steel bar. It was then Loctited onto a length of 6mm precision ground mild steel and once that had gone off the front face was turned to final thickness thus ensuring the face was perpendicular to the shafts axis.



The bearing supports that can also be seen in the photo above were turned from 12mm leaded steel using a ball turner to form the top and a 1mm radius tool to turn the tapered column so it blended in nicely to the ball. Moving over to the mill 3mm was taken off opposite faces and an 8mm hole drilled and reamed through to take the bearing. Back into the lathe a parting tool was used to form a 3mm dia spigot that could be threaded once cut off for a nut to hold the support to the base



Bearings were simple turning and reaming from Colphos and loctited into place after which the oil hole was drilled through

After turning the OD of the eccentric a 1mm parting insert was used to cut a central groove to retain the strap



After which the stock was held in the small 4-jaw and clocked to give the desired throw before turning the spigot, spotting, drilling, reaming and then cut off



After tapping for a M3 grub screw the eccentric was mounted on a 6mm bar so the sawn face could be turned back to the final 5mm thickness



A piece of brass was square dup and then milled to 5mm thickness before boring to size using the eccentric to gauge the fit.



The outside profile was done on the CNC but could quite easily be done on a rotary table or even with filing buttons depending on what you have available.

The eccentric rad was just 2mm dia steel threaded at both ends and the end that screws into the strap had a small spigot turned to locate in the groove of the eccentric

For the top end of the rod I kept the ball shaped theme going when making the rod eye.


Offline Michael S.

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Re: Amateurish Engine
« Reply #9 on: June 04, 2023, 10:56:32 AM »
You did a good job on the bearing and the crankshaft. I look forward to the progress.

Michael

Offline GWRdriver

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Re: Amateurish Engine
« Reply #10 on: June 04, 2023, 04:43:21 PM »
At this stage I was enjoying the building so much that I did not take as many photos as I could have done
For some years I've taken photos of most operations on my projects, especially those which are unique and I think I might need to explain at some point, but like you I'll occasionally get wrapped up in the flow of work and forget to pause and grab the camera so a visual record of that particular operation goes missing from the archive.  :facepalm:
Cheers,
Harry

Offline Jasonb

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Re: Amateurish Engine
« Reply #11 on: June 05, 2023, 07:15:18 PM »
The engraving shows a flywheel with a fairly deep section rim which no doubt helps get the single acting piston back up to TDC, most castings of the right size seemed a bit lacking in mass so I drew one up and set about making it from a slice of cast iron bar that I had to hand which required holding by the minimal amount while some gentle cuts were taken to clean it up.



Once that was done I could get a decent grip of it to turn the other side and also cut a 1mm deep recess with  around nosed tool on each side to reduce the amount of milling required. The hub on the other side protrudes further to give room for the grub screw.



An adaptive path with a 6mm cutter followed by a ramp with a 4mm ball nosed cutter took care of the roughing and finishing firstly to just beyond half depth



After flipping the stock over a shallower repeat of the above took care of the rest after which a quick tickle with a Dremel cleaned up any slight machining marks and gave a little texture.



I did not take many pics of the conrod, just this one that shows the beginnings of the yoke that screws into the underside of the piston crown having the waist cut with cranked round nosed tool.



And one of the little end being turned and tapped after having been milled square and a reamed 3mm hole formed



But I did take a photo of all the parts before putting them together, I just used Loctite to fit the big & little ends to the rod


Offline Dave Otto

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Re: Amateurish Engine
« Reply #12 on: June 05, 2023, 10:26:19 PM »
Hi Jason

Since you didn't cut clear through on the 1st op how did you align side two with side one when you flipped it over?
I did a small flywheel this last weekend and used a pocket routine to cut the openings clear through the blank, then came in with a ball end mill to add all the blends. When I flipped it over I could indicate along the spokes to align two of them with the X axis of the mill. The second side only needed the blends added with the ball end mill. I was using machined soft jaws in the mill vise to hold the blank.

Dave
 

Offline Jasonb

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Re: Amateurish Engine
« Reply #13 on: June 06, 2023, 07:49:48 AM »
Dave, it's not easy to see but right at the bottom of the photo is a black blob, this is a sharpie mark that extends across the rim and round to the other face. Once the top side has been machined I put a pointed wobbler into the spindle and move in Y out to the rim and make a light scribe mark on the side. That mark can then be squared across the face and onto the opposite side. When refitting the work the other way up the jaws are just nipped up and the blank rotates so the marks line up with the wobbler's point. Seems to work well with little or no misalignment.

Of coarse if you are trying to replicate a true cast flywheel then you have the option to offset the second side to get that true representation of the two mould halves not lining up :LittleDevil:

Most of my flywheels tend to have some taper to the spokes so it would be hard to indicate along an edge. I suppose it would be possible to work out an XY co-ordinate part way along the spoke and use a pin in the spindle as a stop to butt the spoke up against, might try that next time as it could be quicker particularly if the side of the tool were used rather than a pin.

Offline Dave Otto

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Re: Amateurish Engine
« Reply #14 on: June 06, 2023, 01:28:01 PM »
Hi Jason

Thanks for the clarification. I suppose that I would just use a DTI in the spindle and walk back and forth equal amounts form center to get the same reading on each end. Same idea just a different way to get there.

Dave

 

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