My Ordinary Little Hit & Miss Engine

[Don1966]

Wowwwwww! You've been busy and that,s looking fantastic Rudy..............

Don

[Roger B]

Coming along nicely    I do like some of your machining techniques  Still following along 

[rudydubya]

Thank you all for your compliments and encouragement.  I really appreciate you taking the time to keep me company.

Rudy

[Bearcar1]

Rudy, N-I-C-E!! Its awesome seeing this one being built. Beautiful work.. thank you.. 


BC1
Jim

[rudydubya]

Jim, thanks.

When I built my Upshur a few years ago I made the crankshaft on my mini lathe out of a solid piece of steel.  It turned out OK (no pun intended), but I still have nightmares from those interrupted cuts.  For this little engine I decided to try a built-up crankshaft.

I used 3/16" drill rod for the shafts and 1018 steel for the webs.  The left side is a little longer than the right to acommodate the hit & miss governor.  I'll use Loctite at the joints and 1/16" drill-rod pins through the shafts to make sure everything stays together.

I machined the webs to size and drilled and reamed the shaft holes.  Then I pre-drilled holes for the 1/16" pins.

I slipped the shafts through the webs with some Loctite at the joints and some 3/16" drill-rod spacers between the webs to keep things in place while the Loctite cured (not shown).  I then removed the spacers and drilled through the shafts and inserted the pins with more Loctite.

I used a hacksaw to cut through the main shaft.  The green tape is just there to keep some scrap sheet metal in place to protect my vise.

Next will be the piston.

Rudy

[b.lindsey]

Nicely done Rudy, but nothing ordinary about the build or the engine as I see it

Bill

[chucketn]

I used 3/16" drill rod for the shafts and 1018 steel for the webs.  The left side is a little longer than the right to acommodate the hit & miss governor.  I'll use Loctite at the joints and 1/16" drill-rod pins through the shafts to make sure everything stays together.

Does this type/shape of crank web offer any advantages/disadvantages over the  traditional rounded shape? Any balancing issues? I need to make a crank for a steam engine, and don't have the correct sized metal to make as per plan. I can make one like this.

Chuck

[Brian Rupnow]

Rudy--Very nice work, and a very interesting thread. I am following along.--Brian

[rudydubya]

Bill, thanks for the kind words.
Brian, nice to have you following along.  I know you like these hit & miss engines, I'll try not to disappoint.

Chuck in East TN, I'm afraid I'm not qualified to give you a good answer as to advantages or disadvantages of this type of crank web.  I chose the rectangular webs because that's what I was familiar with and had material on hand to make them that way.  As far as I know I have no real balance issues, the main shaft is centered in the webs, and the addition of the crank pin at one end only moved the center of mass away from the axis by about 0.012 inches, and it's adding only a few thousandths of an ounce.  I figured it wouldn't be a problem for a low-performance, low-speed little engine like this one, so I didn't add any counterweight to the other end, or try to account for the connecting rod weight, etc.  I have seen a lot of larger engines with circular crankshafts shaped for better balancing like you mention.  Maybe some of the more knowledgeable engine builders on the forum can give us more info.  Sorry I can't be more help for your situation.

Rudy

[Brian Rupnow]

Chucketn--As long as it is a "low speed" steam engine I don't think you will notice any real difference. What is "low speed"??---Probably anything under 300 RPM.---Brian

[rudydubya]

The piston is made out of 6061 aluminum, a through hole for the wristpin and a groove for a Viton O-ring.  Clearance in the middle for the connecting rod.  I considered trying to make some cast iron rings, but wasn't confident enough yet to try making any this small.  Maybe next time.  The piston will be a slip fit in the 1/2" cylinder and is 0.650" long.

I put a bar of 1/2" aluminum (it was slightly oversize) in the lathe and took a couple of very light cuts to get a slip fit in the cylinder, and drilled out some excess material from the inside.  I then cut a 0.070" wide, 0.064" deep groove for the O-ring with a parting-off tool.  I think I got pretty close with the groove, at least with the width, as the O-ring appeared to fit.  After I finished the groove I removed the piece from the lathe and put it in a 5C collet block.

I put the collet block in the mill vise and drilled and reamed a 1/8" hole for the wristpin.  Then I turned the collet block on end and milled out clearance for the little end of the connecting rod.

When I finished at the mill, I put the piece back in the lathe and parted the piston off.

Note:  The above piston turned out to be piston version 1.  After I finished the connecting rod (next), I found that there was too much clearance for my liking between the little-end faces and the inside cheeks of the piston.  Instead of modifying the connecting rod, I modified my piston design and re-made it with a narrower clearance for a closer fit.  I made it just like I did for the first piston, you can't tell them apart from the outside.  The original piston is on the left, with an test-fit O-ring in its groove.

Next, the connecting rod.

Rudy

[vascon2196]

Awesome!

I can't wait to see the rest!

[rudydubya]

Chris, you must be patient, I'm an old man...

I'll make the connecting rod out of aluminum.  As you can see, I'm adding some detail to it, something I can practice on and learn from.  I'll hold the big-end cap on with 0-80 screws.  I won't add any bushings or bearings to either journal.

I sawed off a slice of aluminum and milled it down close to size.  I allowed some extra length for sawing off the big-end cap.

I put the piece in the mill vise with the big end hanging over the edge, and put a washer over it for a guide and to protect the side of my vise when I sawed off the big end cap.  I think normal practice would be to drill the holes for the cap screws before cutting the cap off, but I had confidence in my DROs for drilling the pieces separately (the fact that I broke a drill bit off in my first attempt had absolutely nothing to do with it).  I sawed off the cap.

I milled the rod to length and drilled and tapped for the cap screws.  Then I milled the cap to length and drilled clearance holes.  They turned out OK.

Then I drilled and reamed for the crankpin and wristpin, and it cleaned up nicely.

It doesn't look much like a conrod yet, so I'll add some detail next.

Rudy

[rudydubya]

Since angles and curves are involved in shaping the conrod, I laid out a milling fixture with my CAD program and made one out of a piece of scrap aluminum.  It has holes matching the wristpin and crankpin, and a couple of additional holes for pins to guide my angle cuts.  The wristpin hole has a 1/8" OD brass tube Loctited in and tapped for the screw you see there in it (4-40 as I recall).  It holds the end down and serves as a pivot for milling curves.  There's a spring washer under the screw head to keep the piece held down but allows rotation.  I also made a 3/16" adapter sleeve for the crankpin end, so I can use it for both ends.  The crankpin hole is just a hole, so I can insert (and remove) a piece of 3/16" drill rod when I need it.

Here is the fixture at work.  I milled out the corners first, then started at the little end and milled the outside curve.  I used some small visegrips to hold the other end while I was rotating it.

To mill the top and bottom angles, I put a guide pin in its hole and pushed the big end over against it.  That gave me a straight X-axis cut.  Here you see the setup and the upper side finished.

When I had finished the upper side, I put the pin in the other hole and milled the bottom side.  After that it was just a matter of using the fixture for alignment and removing material and making circular cuts from each face to match the drawing.  I made one small mistake on one side, but not bad enough to require a re-make.  I won't show that.

After a short break we'll do the valves and guides.

Rudy

[Don1966]

Nicely done Rudy and I do enjoy a nice setup to work things out with. The photos are great as is the work..........


 

Don