Double acting triple - Using up spare pieces

[crueby]

This build is going to be a marine-style 3 cylinder double acting engine. No plans, just got a picture in my head of what it should look like plus a stack of brass and steel chunks left over from other engine/clock/boat projects. The size of the larger brass (1 1/2" by 7/8") is the determining factor for the engine block. Within that, going to make a 5/8" bore piston with a 1" stroke and a spool-valve with a 5/16 bore and abot 1/4" stroke. The piston rods will extend through the top of the engine giving a bit more eye-candy than stopping them internally (watching the engine in the Sabino at Mystic Seaport Museum gave me that inspiration). Plan to set it up with a reversing gear as well. Got some sketches down on note paper, but most of it is in the head - may get ambitous and draw up plans. This is nothing ground breaking in design, but should be fun.

Here are some pics of the progress so far. They show the set of engine blocks with the cylinders and valves drilled/bored (you will notice many more than three - while I had the setup done, made some extras to use in some other engines, once had it set up was quick to run off copies).
Next shots show the steps in making the end caps for the valves from a square block of brass - center drilled for screw holes, then turned down protrusion, cut off from main block, and turned the step in the back that fits in the valve hole. The rods are made, will add the spools to them later as seperate pieces (waiting till the steam lines are drilled into the engine block to get the exact positioning of the spools - easier to position them to match the holes than other way around).

 

[crueby]

Next set of steps on this build. First, drilled/tapped the holes for the cylinder/valve caps, then bored the holes for the steam lines in the block. To get all of them angled the same, made a wood block at the angle that the holes needed to be, with other blocks on the side to hold it in the machine vice in the same place every time. Then I could mill a flat, center drill the position, and drill through to the valve hole. Each of those steps was done as a batch (milled all, center drilled all, then drilled all) so I did not have to swap tools on every hole, made it go much faster - just loosen the vice and swap the blocks.

 

[crueby]

Making the cylinder caps - Started with a length of round bar in the lathe, drilled/reamed center hole, then keeping it in the chuck went to the mill and drilled the bolt holes in the perimeter (down through entire rod, got enough depth to make 5 at a time), then moved chuck back to the lathe and used the parting tool with a series of cuts to make the top and bottom of each one, and cut it off.

Next steps will be to counterbore the tops of the holes to make room for packing material (going to try twisted teflon thread tape like another poster suggested - sorry, forget who had that great idea), then will make a top piece for the gland and reshape that piece and the top of this one into an elongated round-rectangle (gotta be a name for that shape - see it all the time on engines!). That will be in a future post. Also, will be milling down the sides of the engine blocks into a taper with rounded ends, wrapping around the cylinder/valve bores (leaving mount blocks for the intake/exhaust pipes) in a future post. That should give it a much nicer shape than the current squared chunk....

 

[crueby]

To shape down the engine blocks, I put some small cap screws in two of the cover holes to use as stops in the mill vise (so that all of the angles would come out the same - dont have a tilting mill vise yet.... someday). Used the fly cutter to shape off the angled flats, leaving blocks sticking up for mounting the inlet/exhaust pipe connectors - on the inlet side the blocks are a narrow piece in the middle, while on the exhaust side they were left full length. The exhaust side will be drilled down from the end to connect the two passages into one pipe.

Then, got the blocks rounded off at the cylinder end. To do this milling, made an aluminum holder with a stop shoulder and a threaded cap, to fit in the cylinder hole. Then, used the rotary table to turn the engine block in the mill to round off the end concentric with the cylinder bore. Drilled and tapped for the pipe connectors, and drilled through for the steam passages (the ends of a couple of those will need to be filled with set screws).

 

[crueby]

Starting to look like something now - shaped down the packing gland blocks using the rotary table with the chuck/vise offset to the one side to give it a nice radius. Used a scrap piece of rod and tubing to position the packing caps in the vise each time (using the v-notch in the vise jaws) without crushing the hollow end of the cap.

Got to trial assemble things and see how it all looks so far (used socket head screws - much quicker to trial fit/dissassemble/put together again/again than with the hex heads!

Then laid out the three blocks to decide on which way to face things, to make a sketch and get measurements for laying out the crankshaft, valve eccentrics, and bearing blocks. Looks like everything will fit okay, even with reversing gear for the valves.

I decided to have one of the blocks face the other way, just seemed to look better that way - no real engineering reason why. A production engine probably would not do this just to make parts all the same - this makes it look a little more like a compound engine, though this one is not.

Making the crankshaft assembly is next - first time I've tried one this complex, be interesting to see how well it goes (hope I picked up enough tips in this forum to avoid the worst of the dead ends!).

 

[crueby]

On to the fun (scary? nervewracking? at least for me) part - the crankshaft. Always been the part I've had the most trouble with. This time tried a new (to me, not to you guys) way of building it up - force fit holes in the webs, assembling it, cross drilling for driven in pins, then silver soldering it up. In the past I went with machining down from castings or larger solid rods. For me, this way worked out much easier given the smaller capacity lathe/mill (sherline) compared to some of the larger ones some others have.

Started out with lengths of rectangular steel stock, clamped together and put in the mill vise for drilling the two press fit holes in each pair - from then on kept the pairs together and oriented the same way to minimize differences. After drilling, milled down the inside edges of each set to form the boss rim.

Then, assembled them onto the main shaft a pair at a time with a short length in place for the offset crank, and drilled for a driven pin down through the length of each web, going through both rods. That held each pair in place for soldering.

After the first two were pinned and soldered, had to slip on the valve eccentrics (turned from steel bar, cut in a slot to hold the valve bearing to be added later) before adding the last web pair. The eccentrics were just pushed on at this point, not lined up till soldering time.

Once all the webs were pinned and soldered, went back and lined up the eccentrics at proper angles with the corresponding web, holding them in place with a small dab of glue. Then, went in and soldered them in place, finally going back and cleaning up the last joints with a file.

All ran true at that point, then got up the nerve to cut the waste parts of the main shaft out from between the webs - all held fine and true! Phew!

Ready to make up the bottom plate (aluminum sheet) and main bearings (brass). Once that is done, ready to make the upper plate and pillars to hold the engine blocks in place so I can make the conn rod assemblies....

 

[crueby]

Time to make the upper and lower plates and main bearings - made a paper template using the crank assembly as a guide and transferred that layout to a piece of aluminum sheet. Milled the holes out with the plate mounted on blocks. Likewise with the upper plate - that one also has some mount holes for the reversing gear to be made later (figured I'd save a step and drill those holes now, make the reverse gear mounts to match the plates later).

The main bearings were made from a pair of 1/4" square bars, clamped together, drilled for main shaft and bolt holes, then cut apart and the tops filed down to shape.

 

[crueby]

Started on the posts for holding the upper/lower plates - started with 1/4" square bar, held them angled in the mill vise (gotta get a tilting vise!) with parallel clamps to hold them tight, and milled off the ends, and drilled them for the mounting bolts.

In the last picture 3 of the legs are there, broke the tap :wall: on the last one, have to remake it. Oh well...

 

[crueby]

On to the conn rod assemblies. Started with a piece of round bar, and milled flats on one side for the conn rod hole, and bolt holes on either side of that.
drilled out the upper half of the holes larger for clearance, and tapped the bottom half. Then, rotated it 180 in the vise and did corresponding flats on the other side. That completed the outer profile of the bearings, so cut the bar in half lengthwise, and reassembled it with some screws. Then, could come back and bore out the center hole that goes around the crankshaft. All that was done with everything still in the long bar, for ease of holding. Finally, cut each of the three apart, all ready to assemble.

The valve eccentric followers are next....

 

[crueby]

Starting in on the valve eccentric followers... Using the same general setup as on the piston crank followers, but started this time with a chunk of square bar (closest I had to something large enough).

So far, have milled down the top into facets to hold the valve connecting rods, and the screw holes on the sides to hold the halves together again later.

Next step is slit the bar into upper/lower halves, and start milling the inner/outer edges. The follower will have a hole in the center to match the cams, but with a protruding lip in middle to sit in the slot cut in the cams, to hold it from moving horizontally. That part should be fun...

In the photos, the sharp eyed will notice there are holes for 7 followers where only 6 are needed - making an extra in case Murphy makes a return visit... (was an engineer enough years to have a lifetime subscription to Murphy's Law!) :hDe:

 

[romartin]

Hi Crueby. I'm enjoying following your build. The pics are beautifully clear and part of the fun is not knowing what's coming next! Keep up the good work.
Ian.

 

[crueby]

Hi Crueby. I'm enjoying following your build. The pics are beautifully clear and part of the fun is not knowing what's coming next! Keep up the good work.
Ian.

Thanks - this one is the first time I've just winged an engine, with just an idea of what I want it to look like - done enough to (hopefully) anticipate what dimensions are critical, and what order it needs to be done in, but most of it is sized/laid out to look good and use the size of materials I have in the pile.

Just got the major pieces put together for the first time a few minutes ago - below is a snap of that. The vertical posts look kinda plain, need to turn in some decoration on those.

 

[crueby]

More work on the valve followers - after last post, I laid out the center hole, and decided that the steps I had made first left too much material and looked chunky, so went back and deepened the steps. Also slit the block in half through the centerline of where the hole would be and screwed the block back together again for the rest of the shaping. Cut each of the 7 followers from the main block (6 needed, one spare).

Then, drilled a center hole through the length of the block. The position of this hole did not matter much, it was just a starter hole for the milling operation. Using the rotary table and four jaw chuck, centered up the pieces one at a time to mill out the center hole. First made the hole the diameter of the rib that will ride in the slot in the eccentric, then stepped it out for the part that rides on the rim. Had to flip the piece over to do the rim cut on the other side. This is where the spare came in handy - I messed up centering the first one for the final cut, and ruined it. :wall:Fortunately the rest came out okay.

Final shaping step was to remount it in the four-jaw chuck with one jaw moved into the center, so I could mill the bottom of the piece concentric with the center hole. With all of them mounted on the crankshaft, it is looking really busy.

Next up: make the reversing gear assembly and get the valves going. After that, make the inlet pipes and can test run this puppy.

 

[crueby]

Started in on the reversing gear assembly - making the arched cross arms for each of the three cylinders. I had some sheet brass (C353) left over from a clock movement, and laid out the pieces on that. Traced the shape from a paper pattern (the radius of the arc puts its center at the center of the eccentric). For each piece, also marked the center point of the arc on the metal, so that when clamping it down on the rotary table, the center point would be at the center of the table, and rotating the table would cut the arcs. I drilled the holes where the conn rods down the eccentrics will attach with clevises, and also where the lever arm that will move the set back and forth attaches. Then, used the rotary table on the mill to cut the center slot, and top and bottom edges. Freehand moved the mill table to do the vertical cuts at the ends and tabs. That hole setup went pretty quick - then just a little time on the sanding belt to round the ends and tabs, and ready to go.

Next up - making the clevises and lever arms. Getting close to firing it up first time....

 

[crueby]

Got some more done on the reversing gear - made the clevises to attach the valve rods, and got it all mounted. Still need to make the actuating levers for it...

 

[ChooChooMike]

For someone "winging" it, you are doing a pretty darn good job !! Love the fact you're using Sherline equipment for all of this Interesting and different setups I would not have thought of !! :bow:

Mike

 

[crueby]

For someone "winging" it, you are doing a pretty darn good job !! Love the fact you're using Sherline equipment for all of this Interesting and different setups I would not have thought of !! :bow:

Mike

Amazing how many ways there are to set up a rotary table, 3 or 4 jaw chucks, and a vise! Never got very good with an etchasketch, but same skills come in handy sometimes in milling out complex shapes. Plus, a file and sander can fix a lot of boo-boos...! I've had good luck with the sherline - used to have an old unimat, upgraded to the sherline when I went from mainly ship models into engines and clocks. Sometimes wish I had a larger lathe, but can do a lot with the small one.

Right now working on figuring out the best way to make the reversing gear link arms - not a lot of room between the cylinders, and had a couple false starts that wound up with too many tiny pieces without enough thickness to thread. Think I got it licked now, pics to follow in next couple days.

 

[crueby]

Finally got he arms/linkages for the reversing gear made and installed - had some false starts on it that were not robust enough or were too hard to assemble next to each other.

Ended up milling the arms out of a chunk of mild steel with the angles on the ends all part of the same piece. Then turned down the shafts on the lathe and the short pieces at the end on the mill's rotary table. Came out looking about right and works good.

Coming down the home stretch now - making up the intake/exhaust manifolds and that will be the last of the parts. I did make a intake that I can bolt to one cylinder at a time to get the valve timing tuned up - easier to run it on each piston seperately to know if they are all running right. First need to go back and do a little tuning on the valves, one of them is sticking a bit. With the holiday coming up, probably going to be another week or so till it is all up and running (hopefully well!) - will post video then.

 

[crueby]

Got a start on the guide/locking plate for the reversing gear - milled out of scrap of brass sheet (used piece of wood as sacrificiall spacer between it and the rotary table). Still need to smooth out the ends and mount it to the uprights next to the actuating arm.

 

[crueby]

Had some time this morning, and was able to get the intake manifold made and make a first run - video below. Dont have the guide/lock plate on for the reverse gear arm, but could not wait to see how it went. Also need to make the exhaust manifold - right now just exhausting out of the back of the main blocks. So far so good! Nice to see it running finally.

[ame]http://youtu.be/Q2zFwmiAJTg[/ame]