discussion Elmers Standby #19 Model Steam Engine

[Mr Bowcat]

Morning all.

I decided it was time I used my machines to build something other than tooling, so I've chosen this as my first engine build. This is a model of a simple steam (or in my case air) powered engine designed my Elmer Verberg. This is a relatively cheap build, there are no castings, it's all built from bar stock so only around £30 in metal (although in fairness several thousand in tooling).

The plans and stock.

I'm starting with the foot and frame, these were rough cut from 10x50mm aluminium then squared up.

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And the features formed.​

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The most nerve racking part of this was the long 3mm hole from the end all the way down to the crank pin hole, around 60mm.

 

[Jim R]

Very interesting project Bob. Way beyond my comprehension but fascinating to follow. I imagine that setting up your machines accurately is quite a job.

 

[Tim Marlow]

Great start Bob. Not often we see real engineering on here. Just out of interest, what is the function of the “long “ hole?

 

[Mr Bowcat]

Cheers gents.

Jim, yes getting and maintaining the machines to be true is a necessary evil, and fixturing the parts generally takes more time than actually machining the features.

Tim, the long hole is a steam passage. I have one more hole that needs to be drilled in the frame side that will meet a matching hole in the rear of the cylinder. The long hole will actually be blanked off at teh end eventually, so the steam (or air) will be directed back down toward the crank pin which will have flats machined into it which act as the inlet and exhaust valves.

it will probably make more sense when more parts are made, at least I hope so as I'm a bit confused as to how it all works myself.

 

[Tim Marlow]

Bit like a sleeve valve system then Bob…..at least, in my head so probably wrong . The long hole is just a way of porting steam to the cylinder.

 

[Mr Bowcat]

Having studied the plans some more it appears to both port steam to and away from the cylinder. Onene slot in the crank pin will feed steam (or air) into the cylinder, then as the engine turns and the piston is pushed the other way, the steam (air) is then pushed back down the port and out via another slot in the crankpin.

 

[Mr Bowcat]

Morning all.

Started on the cylinder yesterday. This is a relatively simple block, 20x20x37mm with a 14mm hole bored 35.5mm deep.

I started off by squaring up the stock and reducing it to the required 20x20mm square dimension, but leaving it over long at this stage. This was then stood upright in the mill and the hole bored with a variety of drills and finally a 14mm 3 flute slot drill (milling cutter). The surface finish is actually pretty good, it looks a little rough in the photo but is actually very smooth. However I will end up giving this a polish later down the line.
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With the hole bored slightly over-length I could then use my depth micrometer to find out how much over it was , then fly cut the end of the cylinder to get the precise depth.

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I ran out of time after this so still have to reduce the other end to overall length, then add some holes and chamfers.

 

[Jim R]

Making progress on this very interesting project. Sounds as if you have it well planned and it seems to be going as it should.

 

[Mr Bowcat]

Thanks Jim.

So far so good, I am spending a lot of time thinking ahead, especially in terms of order of operations.

 

[Mr Bowcat]

Morning all.

I decided to brave my very cold workshop last night in order to finish the cylinder. This consisted of 5 holes, one all the way through to meet up with the steam passage and 4 threaded M3 to mount to the frame, and a couple of aesthetic chamfers.

And here it is mounted to the frame. A quick blow through with air confirmed the holes all line up and I will be able to get steam/air to and from the piston.

Think I might tackle the flywheel next.

 

[Jim R]

Fascinating

 

[Tim Marlow]

Having studied the plans some more it appears to both port steam to and away from the cylinder. Onene slot in the crank pin will feed steam (or air) into the cylinder, then as the engine turns and the piston is pushed the other way, the steam (air) is then pushed back down the port and out via another slot in the crankpin.

Pretty much how a sleeve valve works, except it goes backwards and forwards rather than round and round . At one end of the slide it lets live steam in, and at the other it lets exhaust steam out. Using the crank pin is a pretty elegant solution I think. This is starting to look really good, you’ll be building live steamers in no time

 

[Mr Bowcat]

Cheers Tim.

I'm starting to get my head around how it works, I think as more parts are made it should become clearer to me.

 

[scottie3158]

Bob,
Looking very good mate a great project took me back to being an apprentice, I can smell the swarf now.

 

[Mr Bowcat]

Cheers Paul.

 

[Mr Bowcat]

Morning all.

I got back to work on the Elmers this weekend. I decided instead of making the flywheel I would concentrate on some of the smaller parts.

First up was the bearing, which also acts as the steam/air intake, and the inlet pipe bracket.

Then on to some very small parts, the crank pin and wrist pin.

And the crankshaft. Having made this I think I now understand how it works. It has a large and a small flat at 180 degrees, the small flat has a hole through it that meets up with a hole drilled along it's length. As the engine turns the long flat allows steam/air to travel up the long hole in the frame and across into the piston. As the engine continues to turn the piston will then push the exhaust gas back along the passage where it will meet the small flat, and exhaust out the hole in the end of the crankshaft.

Finally I decided to attempt what to me is the hardest part to machine, the connecting rod. This is made from 3mmx6mm flat brass bar. After locating the holes on the mill, it needed to be turned on the lathe. Holding such a small part in the 4 jaw is difficult, so I made up a fixture to help with that.

Then it was just a case of using a parting tool to locate either end of the taper, and turn down the central section.

This still needs the ends cut down and rounded, but I am more than happy with this part.

 

[Jim R]

All the parts look good. I have no idea how you go about making parts like these but its very interesting to see it done. The accuracy needed must be very high.

 

[Mr Bowcat]

Thanks Jim.

Most of this weekends parts were made on the lathe, with a few features then added on the mill.

in terms of accuracy, yes a lot of the parts need to have close tolerances. The crank for example has to be able to hold steam/air, yet still be able to turn smoothly in the bearing.

I have DRO's (digital readouts) on both my mill and lathe which have a resolution of 5 microns (5 one thousandths of a mm) which helps a lot in holding tolerances. I would hate to do it the old fashioned way of counting revolutions of the hand wheels and dealing with backlash.

 

[Jim R]

a resolution of 5 microns (5 one thousandths of a mm)

I find it almost impossible to visualise something that small!

 

[Mr Bowcat]

Yep, its pretty diddy. My micrometers and dial indicators go down to 1 micron (0.0001mm).

An average human hair will be around 50-100 microns, to give you some idea of scale.