Three Cylinder Oscillating Steam Engine

[toolznthings]

Building the Samuel K. Hodgson's engine from plans published in " Steam & Stirling " book # 2. Making some changes in materials and some modifications to some of the designed parts. Will make the cylinders from 12L14 using 1 3/4" round stock with a through bore and brass cylinder head instead of aluminum with a blind bore. To start I faced and turned a cleanup cut on the o.d. on one end of the stock.



Turned stock around and faced opposite end.



Extra stock will be left on the cylinder block for final finishing after silver soldering the pivot to the block. At the mill. Holding on to the faced ends from the lathe milling to rough size the cylinder comes next.



After sizing the cylinder I machined a shallow pocket for the pivot pin allowing some clearance for the silver solder.



The cylinder pivot is .375 12L14 rod rough cut longer than finished length.
Silver soldered in place and glass beaded to cleanup for next operations.

 

[toolznthings]

With the collet chuck on the lathe and holding onto the .375 cylinder pivot shaft I will be machining the cylinder back face true to the shaft. This will make sure the cylinder will be square to the pivot and seal against the main body of the engine.



Making the face cut and adding the undercut relief around the pivot.






With this face finished I can now machine the opposite face parallel and to size. Remember there is stock on all surfaces of the cylinder.



Out of the lathe ready to go back to the mill.



I now have two finished faces to work from and will mill one face first measuring off the pivot to establish size.



Squaring up to the first milled face to do the first end of the cylinder.

Using a depth mike to establish the finished dimension on this end.



Setting on a parallel to finish the overall length.



Finished the last face using a parallel and set up to cut the pivot to its final length.

 

[Blogwitch]

This is a good engine to learn how to do co-ordinate drilling on, and your choice of materials seem to be just fine.

With these small engines, it pays to experiment a little with things, as long as you keep the basics in line with the plans, almost any else goes, rounding off corners, finning, flutes etc, it makes for a more personal engine.

BTW, I do like the way you are putting text with each picture, it allows the followers to know what you are doing rather than just a string of pictures and being left guessing.

Nice one

John

 

[toolznthings]

After machining the length on the cylinder pivot shaft I set up to drill and tap the end for a 6-32 thread. Used a stop to align the other two cylinders.



The next setup will be for boring a thru hole about 1/2" in diameter in the proper location for the cylinder .750 diameter bore.

Used 1/32 parallels and keeper springs.
Spot drilling for rough drilling a thru hole.



Boring on location to get a true hole for indicating at the next setup.Size was not important, but position and straightness was the goal.



Off to the lathe with a four jaw chuck to finish the bore. Using a long stem indicator I can indicate the bored hole front and back to true up for boring. A quick indication on the cylinder face was also done.
I happened to have a piece of hex stock with a drilled hole which fits over the pivot shaft to allow one of the jaws to grip the part and soft pads on the other jaws.
Finishing at the lathe is far easier to get a smooth bore and I can also polish the bore here.



Boring with a small carbide boring bar.





With all three cylinders bored a steup at the mill was done for drilling and tapping the 0-80 holes for the cylinder heads.



The final operation was to mill the corner chamfer on the cylinders. I used a v- block and balanced the vise with one of the other cylinders. You can't see the mill stop I have lower in the vise for the v-block to stop against. Simple matter of side milling and turning the cylinder end for end to get equal chamfers.



The finished cylinders. I milled some additional relief around the pivot shaft before assembly. Not shown here.

 

[toolznthings]

Next on the the list of parts is the main plate that supports the cylinders and has the air passages. Starting with a piece of 3/4" 6061-T6 aluminum bar stock I set up to machine the .625 thickness.

Rough sawed to length and held in the vise on the two stock surfaces. Resting on the parallels and not tapped down against them for the first cut.



With this side finished the part was flipped over and this time was seated tight against the parallels and finished to .625 thick.





Band sawed the bulk of the material off one side.



The plate will be finished to 5.500 wide and 4.875 high. Took a light cut with the face mill to get one edge square to the face.



Milled the opposite side parallel to this first cut and to size. Used indicator and setup for the next face to be square to the first two cuts.



Milling with the side of a end mill will not produce a perfectly square cut to the face. Thus the reason for milling in this fashion. I'm cutting the part to size and square for the setups for drilling.

Set up to drill the two air passages that run thru the 5.500 width first. Drill half way thru one side then from the opposite to match up with the first holes.
Spot drilled, screw machine drill, then jobber drill to finish.





Angled holes were next that connect to the cross drilled holes. Used a height gauge and marked the starting point for drilling and made a felt tipped pen layout for reference.
Using a set of tall jaws I set the part with the protractor.



Used the wiggler to pickup the layout line for the first hole.



Spotted the surface with a end mill for the drill to start. Used screw machine, jobber and taper length drill to reach the cross holes.





Same operation for the opposite side with the part tilted the other direction.

 

[toolznthings]

More air holes to drill from the bottom of the main plate to connect with the first two cross drill holes.



Full disclosure with this operation since I'm doing a build done, post last, in this thread. I drill the holes shown in the wrong position. :wall: Not to swift since I plugged all ten holes and had to drill them out to fix. ( no way to get chips out ) Added the three 10-32 mounting holes to the bottom in the correct position.

Onward !

Made a setup to rough drill and bore the main bearing hole and the three cylinder pivot holes. Did a layout and determined that I had enough room between the air passages to add some brass bushings.



Set up the boring head and bored all four holes. At the lathe I made the main bearing and the three pivot bearings.





Finished bores before bushings.



Next set up was for the face holes that feed and exhaust air from the cylinders.
These holes break into the sides of the previous drilled holes so I used a 1/8" end mill.



I installed the pivot bushings permanently, but left the crank bushing a lite fit so I could remove it to do the final finishing of the faces without the bushing being in the way.



Using the pivot holes for locating with 3/8" shoulder bolts, I made counter bored and threaded holes in a fixture plate.



After rough sawing away excess stock I made a setup at the CNC mill to cut the large radii. Using the bored crank shaft bushing bore for part 0,0.



Milling the radius cuts.



Finished and ready for some more drilling.

 

[toolznthings]

Adding the air inlet/exhaust ports to the main back plate. Drilling to the angled air passages and spot facing and tapping for 5/16-24 threads. Set up at correct angle and picking up the center of the main bearing bore.

Setting at 56 degrees.


Picking up the bore with gauge pin and edge finder.



Spot, drill and tap. Repeated on opposite side of plate.



Also added the oil holes to the bearings. Using a simple layout for each bearing.



Decided to do the pistons with a indexer and tail stock setup.

Made blanks for the pistons at the lathe with extra stock for holding in a collet in the indexer and extra stock for a tail stock center. The left side of the groove closest to the collet is the piston end. Picked up the end with edge finder.
Doing the two lower pistons with the off sets first which need larger stock.



Milling and indexing to do all four sides in one set up.



With all four sides milled the wrist pin hole was drilled and reamed. I also used a pointed center to make a spot for dividers to layout the end of the piston as a guide to finish. Did this before drilling.



Similar set up for the top vertical piston.





Set up at the lathe to remove the excess stock and face the ends of the pistons.
I finished the ends with a belt sander to my layout line and polished the ends.



The two lower pistons get the ends milled with a .394 wide x .375 deep slot measured from the center of the wrist pin hole. Total depth .687 from the end.

The set up in the vise.



Milling to size.



The pistons before the oil groove. Also drilled oil holes through to the .312 wrist pin holes. ( not shown )



Added a v-groove in each piston for oil.



A trial fitting of the cylinders and pistons on the main plate.

 

[toolznthings]

Decided to make the crankshaft in two parts. The main body turned from 12L14 and the wrist pin from a 5/16" dowel pin.

Turning the .375 shaft diameter and the 1.500 diameter in one set up.



Finished. Ready for facing the 1.500 diameter to length.



Sawed off the bulk of material and finish faced to size.



Set up at the mill to bore the hole for the wrist pin dowel. It will be a press fit.

The set up with a v-block.



Indicating to find center.



Boring the hole for the wrist pin.



After boring and not moving from location over the bored hole I put the dowel pin in a 5/16" collet and used the mill quill to start the pin into the hole to insure that it was started straight. Finished the press in with the part between the mill vise jaws.



The finished crankshaft.



Turning the brass cylinder heads next. This was my change in design to have thru bored cylinders.Turned and parted off and chucked to finish the top of the head.



Finished facing with a small under cut for looks.



Setting up at the mill using my small three jaw chuck fixture. Temporary spacers under the part to be removed for drill clearance.



Indicating the cylinder head.



With spacers removed and using the DRO bolt circle routine the clearance holes for the 0-80 SHCS were drilled.

 

[toolznthings]

Making a modification to the fly wheel by adding a hub for a set screw rather than having the tapped hole at a angle. To do this the crank bushing needs to be shorter than the print call out. With the set screw at 90 degrees to the crankshaft I will be able to add a flat for the set screw and will be able adjust the end play easier at assembly. Set screw will be 10-32.

Bored the bushing first.



Checking the fit.



Turning o.d. to finish.



Turning the first side of the fly wheel with the hub.



Rough drill and bore. Add chamfer. ( not shown undercut the face )



Facing opposite side of flywheel in soft jaws. Add center undercut and chamfer.



The finished flywheel.

 

[toolznthings]

Threading the air inlet to match the air brush hose I use for my engines. The opposite end gets 5/16-24 threads.



Test fitting the threads.



At the mill to cut a hex for wrench.



The finished fitting.



Ready to do some finish work before assembly.
Benching the mill marks from the cylinders on the granite plate. See "Tips & Tricks " for my method.



The three cylinders finished.



My next idea to reduce friction between the cylinders and main plate. I added strips of adhesive backed UHMW tape to the cylinders. Applied to acetone cleaned surface and compressed in the mill vise for max adhesion. Picture of tape before trimming and adding the air hole. The addition relief cuts around the pivot pin can be seen in this view.



Masking the cylinders for painting.



Rattle can spray paint " Ford Blue "



Careful masking of the flywheel for some red paint.



After polishing the piston side of the main plate I masked all other areas and sprayed the back side. Tooth picks in the oil holes.



Machined the base plate and finished the surfaces to remove any mill marks.



The parts ready for assembly.

 

[toolznthings]

Finishing up the engine with all the parts ready for assembly.

The pistons and cylinders with crankshaft assembled ready for the main plate to be lowered over them while laying flat on the bench.



Lowering the main plate onto the pivot shafts and crankshaft is the best way to get everything together.



Air and inlet and exhaust fittings in place. The springs and spring covers are next. I shortened the spring covers overall length about .030" to allow for the UHMW tape that is on the cylinders.



Attached the aluminum base plate with three 10-32 shcs.



Added the cylinder heads and flywheel to finish the assembly. Left the flywheel solid for a little extra weight because of the springs I used.





The engine finished and running with a few drops of oil. Thanks everyone for the views and " likes " ! I appreciate the interest.
Brian


https://youtu.be/s8VDl3aEwAg