Sea Lion Engine build

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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barts
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Sea Lion Engine build

Post by barts » Mon Feb 01, 2016 5:11 am

I'm finally cutting metal on the Sea Lion engine. I'm starting with building the crankshaft; the crankshaft cheeks are 2" x 5" x 7.75" steel plate. I welded (tacked) them together and line bored the crankshaft and crankpin holes on the lathe, squared things up, and laid out the four tapped holes where the counterweights will bolt on and the two for the pinch bolts that retain the crankpin. I did all the drilling on the Bridgeport. I didn't have a 1" end mill to counterbore the holes for the pinch bolt Allen heads; after messing around w/ a boring head and getting a poor finish I finally got smart and used the rotary table w/ a 3/4" endmill (video included). The co-ax indicator I picked up a couple of years ago sure saves time when doing setups like this.

At this point I'm waiting on the pinch bolts (4" x 5/8"-NF 20 Allen head) and the 2" 4142 pre-hard for the shafts and crankpin. I'll make he counterweights once the piston, rod & crosshead are done & weighed so I can balance the engine properly.

Photos are here:

https://goo.gl/photos/aqmFMXKRHXUjTwFt8

- Bart
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Re: Sea Lion Engine build

Post by Akitene » Mon Feb 01, 2016 7:48 pm

You're doing a great job, Bart. The rotary table + end mill combo is a smart one.

Judging by the size of the crank webs, your Sea Lion will be on the big engine side. What will be its overall size?
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Re: Sea Lion Engine build

Post by barts » Mon Feb 01, 2016 8:38 pm

Akitene wrote:You're doing a great job, Bart. The rotary table + end mill combo is a smart one.

Judging by the size of the crank webs, your Sea Lion will be on the big engine side. What will be its overall size?
Thanks... the engine will be 5.75" x 5.75" bore & stroke; it's a poppet valve uniflow, so the engine is large for it's power output.
I'm using all rolling contact bearings to keep the engine clean.

- Bart
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Re: Sea Lion Engine build

Post by racerfrank » Tue Feb 02, 2016 2:50 am

Bart

On your line boring setup, it appears there is a plate bolted to the cross slide possibly using the compound slide mounting bolts to hold it down. Is this how it is? what holds the other end?

Frank
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Re: Sea Lion Engine build

Post by barts » Tue Feb 02, 2016 3:57 am

racerfrank wrote:Bart

On your line boring setup, it appears there is a plate bolted to the cross slide possibly using the compound slide mounting bolts to hold it down. Is this how it is? what holds the other end?

Frank
There's a threaded hole in the compound about where the screws hold the cross-feed nut; there's a setscrew in it normally. I discovered this by when looking for a way to fit a taper attachment (still a future project). I use that and the two compound attachment bolts to fasten the tooling plate to the cross slide. I drilled and tapped a bunch of 1/2" bolt holes so I can use my mill tooling to fasten the part being machined.

If there hadn't been a hole to use, I could have drilled and tapped one.

I made this plate when I needed to clean the wear out of the piston valve bore on Otter's antique steam engine.

- Bart
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Re: Sea Lion Engine build

Post by barts » Mon Feb 08, 2016 4:01 am

I've added some more photos to the crankshaft album... and included one below for a teaser.

https://goo.gl/photos/aqmFMXKRHXUjTwFt8

The 2" type E pillow blocks that will be the engine main bearings (and handle the propeller thrust load) arrived this week, along with 26" of 2" 4142 chrome-moly, heat treated, ground and polished. I machined the crankpin from the latter, and made the two ends of the crankshaft; they just needed facing and center-drilling. There's a bit of video in the album showing the 2" shaft in a steady rest. Next it was time to separate the two crank cheeks; a 3/16 end mill worked to machine out the tack welds at either end. I then used the bandsaw to cut the outer web on the crankcheeks so the pinch bolts could work.

The hardened chrome moly shafting cut readily w/ a high-speed blade in my venerable 4x6 bandsaw at a slow speed. I used carbide tools and it machined ok; it is tough. It seems to machine better if I push the feed a bit ore than feels comfortable.

I tested the effect of the pinch bolts; at 100 ft-lbs on each 5/8" Allen head the two crank checks & crankpin are one piece :).

Next, I need to machine the spacers that center the bearing between the crank cheeks on the crankpin, and have Barbie (who has access to a Maker Space) sandblast the crankshaft cheeks. Then it's time to heat the cheeks to 300F and freeze the shafts, which should give me plenty of slip room to assemble the shafts and cheeks; there's only a bit over .001 interference at room temperature. I'll add 1/2"-NF dutch keys (2 per end) lock-tited in to hold things in place. My backup plan in case this won't hold is to add another pinch bolt between the two shaftt and cut a slit between the two bolt holes, but I doubt I'll need this.

- Bart
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Re: Sea Lion Engine build

Post by barts » Thu Feb 11, 2016 7:31 am

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The checks have been sand blasted (thanks Barbie!), and tonight I heated them to 300F and cooled the shafts to near 0F in the chest freezer, and assembled them. It actually takes a minute for the parts to 'grab' since they had about 3+ thou clearance; once they start, of course, it goes very quickly as the contact force and thus the heat transfer increases.

Next it's time to drill and tap for the Dutch keys, and assemble and check between centers on the lathe how close I got things. I may check first to see if the keys affect anything.

I may pick up some metal this week so I can start fabricating the base... a single cylinder engine doesn't take a lot, but the bearing carriers are taking a lot of force (2600 lbs each) so some section is needed between the engine columns and the bearings.

Since the boat design has a box keel, the crank is actually hung under the engine base. I will run copper tubing to the bearings for greasing; this would be hard to pull off w/ a bronze bearing and oil cups :). A low crank keeps the prop shaft straight, and lets us keep the cabin sole low and free of 'lumps and bumps'. This means I also need to make a platform on casters for the engine to sit on during assembly, since the flywheel and crank are actually below the engine bearers.

- Bart
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Re: Sea Lion Engine build

Post by DetroiTug » Thu Feb 11, 2016 3:51 pm

Bart,

Looks like you're doing an awesome job and looking forward to future updates. All of you building engines really gives me the bug to build one, but I have too many irons in the fire right now.

-Ron
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Re: Sea Lion Engine build

Post by barts » Fri Feb 12, 2016 6:23 am

DetroiTug wrote:Bart,

All of you building engines really gives me the bug to build one, but I have too many irons in the fire right now.
-Ron
Yup... the other build thread got me off my duff :). I've been sketching up this engine for many years in one form or another.

I torqued up the crank pinch bolts to 100 ft-lbs, and chucked on end in the lathe chuck and the other end on the center. It ran about .007 out of true; an few 'adjustments' w/ a heavy brass hammer and my dial indicator says .0005 - close enough. This weekend I'll try and key the main shafts so they'll stay put when there is 5000 lbs pushing and pulling on the connecting rod.

It's interesting; the peak forces can be quite high w/ uniflows, but the large expansion ratios mean the BMEP is actually quite reasonable.

- Bart
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Re: Sea Lion Engine build

Post by DetroiTug » Fri Feb 12, 2016 3:57 pm

Bart,

Curious as to the intended starting procedure. Seems in a single cylinder Uniflow that with the compression or re-compression stroke that starting could be difficult. Some sort of conventional exhaust poppet valve for starting? That can then be left closed once flywheel inertia is sufficient?

-Ron
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