I was wondering...

A special section just for steam engines and boilers, as without these you may as well fit a sail.
User avatar
barts
Full Steam Ahead
Full Steam Ahead
Posts: 1069
Joined: Wed Nov 18, 2009 6:08 am
Boat Name: Otter, Rainbow
Location: Lopez Island, WA and sometimes Menlo Park, CA
Contact:

I was wondering...

Post by barts » Sun Nov 27, 2016 4:51 am

Is there a functional reason that holes in the flywheels for barring the engine over are generally square? I can guess that a round bar in a larger square holes isn't as likely to get stuck, but that seems somewhat dubious as a reason. Perhaps it was easier to cast square holes?

- Bart
-------
Bart Smaalders http://smaalders.net/barts Lopez Island, WA
User avatar
fredrosse
Full Steam Ahead
Full Steam Ahead
Posts: 1906
Joined: Fri Nov 20, 2009 5:34 am
Boat Name: Margaret S.
Location: Phila PA USA
Contact:

Re: I was wondering...

Post by fredrosse » Sun Nov 27, 2016 5:27 am

It seems to me that it would indeed be easier to make a core for typical sand cast flywheels with square (or very nearly square ) sand projections on the core piece.
User avatar
DetroiTug
Full Steam Ahead
Full Steam Ahead
Posts: 1863
Joined: Fri Nov 27, 2009 5:56 pm
Boat Name: Iron Chief
Location: Northwest Detroit

Re: I was wondering...

Post by DetroiTug » Sun Nov 27, 2016 11:42 am

Bart,

Easier pattern would depend on the design, method and available equipment/software. If the square holes are short and do not run all the way to the edge - a slot, it would involve a complicated one or multiple piece sand core that is placed over the initial sand cavity formed with a conventional 2-piece pattern. The top surface of the initial sand cavity is the middle of the outer ring - no way to remove a one piece pattern half if the square holes are near center and do not run all the way to the edge.

I think the intention here was that flywheels possibly weighing tons were pried over a fulcrum, and a flat tipped pinch bar works in a square hole with flat sides. Round holes would have the probability of the wrong size bar getting stuck, not a big issue on our smaller engines, but again on flywheels weighing tons, it could be disastrous.

For a 30"? spoked? flywheel pattern, I would definitely consider "S" shaped spokes or some other indirect route from hub to outer rim. Straight spokes on large one piece spoked castings have a high probability of cracking when cooling.

-Ron
User avatar
barts
Full Steam Ahead
Full Steam Ahead
Posts: 1069
Joined: Wed Nov 18, 2009 6:08 am
Boat Name: Otter, Rainbow
Location: Lopez Island, WA and sometimes Menlo Park, CA
Contact:

Re: I was wondering...

Post by barts » Sun Nov 27, 2016 5:46 pm

This is of course for the Sea Lion engine build; I'm going to need to turn the engine over to the right position to start since it has a pretty short duration intake valve opening. The flywheel is nestled down in the frame (the bearings are underneath) so grabbing it by hand is not a good idea. The flywheel is limited to 12" in diameter, so it will be a 3" thick chuck of 1018 steel, w/ holes drilled in the face to fasten the prop shaft adapter. I'll mount the flywheel up on the rotary table and drill some holes in the rim. so I can bar it over.

The attached picture is up to date aside from the cylinder details; I'm simplifying that assembly still and haven't made a new one. I gave up on the roller crosshead since the accelerations are too high to prevent the rollers from sliding, and will use a traditional slipper design w/ lead babbitt running on cast iron. There'll be a pad to collect drippings underneath the crosshead, and a wick-type oiler. I may experiment w/ grease as well; the loading is pretty low.

- Bart
Attachments
assembly.png
assembly.png (42.35 KiB) Viewed 10697 times
-------
Bart Smaalders http://smaalders.net/barts Lopez Island, WA
User avatar
fredrosse
Full Steam Ahead
Full Steam Ahead
Posts: 1906
Joined: Fri Nov 20, 2009 5:34 am
Boat Name: Margaret S.
Location: Phila PA USA
Contact:

Re: I was wondering...

Post by fredrosse » Fri Dec 02, 2016 1:01 am

On a couple of older lawn tractors I have owned, (8 & 10 HP in the 1970s) a belt driven generator was also the engine starter, turning with about 10-12 inch pulley on the engine, and about 3 inch diameter pulley on the generator/starter. That might work for your application with little fuss. Also you might consider the more conventional starters supplied now with the 10- 14 HP lawn tractors of today, which work much more like automotive starters, just smaller.
User avatar
TahoeSteam
Full Steam Ahead
Full Steam Ahead
Posts: 813
Joined: Fri Mar 07, 2014 5:38 am
Boat Name: Wayward Belle
Location: South Lake Tahoe, CA, USA
Contact:

Re: I was wondering...

Post by TahoeSteam » Sat Dec 03, 2016 7:40 am

The Dodge Brothers automobiles used a similar setup with their generators until about 1925. John York has one and when he's starts it, all you hear is the compression in the cylinders. Way ahead of their former employer's model T nonsense.
User avatar
barts
Full Steam Ahead
Full Steam Ahead
Posts: 1069
Joined: Wed Nov 18, 2009 6:08 am
Boat Name: Otter, Rainbow
Location: Lopez Island, WA and sometimes Menlo Park, CA
Contact:

Re: I was wondering...

Post by barts » Wed Dec 07, 2016 4:15 am

I could certainly use a golf-car starter for this purpose; they're a lot lower output than a real alternator, though;
about 15 amps at full rpm. I had one of these starter generators on an old Bolens tractor; started the 14 hp single
cylinder Wisconsin w/o any problems.

I'll have solar panels on the boat as well since I want the batteries to stay charged while she's on a mooring or for
anchor. The typical marine fridges take about 20 - 25 amp/hr /day. A couple of 100w solar panels would help
a lot, as would an ample battery pack.

I'll mull this over; powered cranking is certainly nice for clearing the engine of condensate w/ the drains open and
the throttle cracked just a bit.

- Bart
-------
Bart Smaalders http://smaalders.net/barts Lopez Island, WA
User avatar
barts
Full Steam Ahead
Full Steam Ahead
Posts: 1069
Joined: Wed Nov 18, 2009 6:08 am
Boat Name: Otter, Rainbow
Location: Lopez Island, WA and sometimes Menlo Park, CA
Contact:

Re: I was wondering...

Post by barts » Wed Dec 07, 2016 5:28 am

Hmm. The idea of using a starter generator seemed familiar, so I looked at my notes and recalled the problem: they want to spin pretty fast, which is hard to arrange w/ a 400 rpm engine.

The maximum continuous rating is on these units is 8000 rpm; the speed at idle is ~3000 rpm. This is rather difficult to arrange w/o a multi-stage step-up drive, which is kind of ugly.

The Balmar marine alternator I am considering (70A 6-series) is available w/ a 1.9" serpentine belt pulley; w/ a 12" pulley on the crankshaft the alternator will turn at 1500 rpm at the planned engine idle of 250 rpm w/ the Kitchen rudder in neutral; this would produce 15-20 amps. At an easy cruise speed of 300 rpm, the alternator would output 50-60 amps. This gives ample power for a 12v icebox cooler or other amenities.

The nicest approach might be a direct drive motor-generator made from one of those Fisher-Paykel washing machine motors, but that's more of a project than I need. Baring holes and a real alternator seems simpler :).

- Bart
-------
Bart Smaalders http://smaalders.net/barts Lopez Island, WA
User avatar
DetroiTug
Full Steam Ahead
Full Steam Ahead
Posts: 1863
Joined: Fri Nov 27, 2009 5:56 pm
Boat Name: Iron Chief
Location: Northwest Detroit

Re: I was wondering...

Post by DetroiTug » Wed Dec 07, 2016 2:58 pm

I think it would take a very large brush DC motor (generator), to start this large Unaflow. Would work great for a conventional steam engine, but the compression stroke is going to be hard to overcome. Brushed DC motors have very low torque at low RPM - why most successful starters us a reduction gear.

You guys may recall, I tried to hack an alternator on the Tug and it didn't work. I stepped up, I think 8:1? and it was still not sufficient RPM to over come the RPM needed to exceed 12v output. I wound up using a 60 VDC servo motor. It reaches 12 volt at about 250 engine RPM, then above that it is charging the battery. It's more of a novelty than necessity and it IS a way to charge the battery, but it comes at a cost to shaft horsepower. Only used when needed, have a switch to turn it off and on.

The starting sequence will probably be similar to a hit and miss engine, roll it back to top and then fire it and away she goes. I'd be considering an exhaust valve in the head with it's own eccentric that can be disengaged for starting. For that a Stephenson link could be used with a crank driven eccentric attached to one end and the other end attached to a rod that simply connects to a rotating collar on the crankshaft (disengaged).

-Ron
User avatar
barts
Full Steam Ahead
Full Steam Ahead
Posts: 1069
Joined: Wed Nov 18, 2009 6:08 am
Boat Name: Otter, Rainbow
Location: Lopez Island, WA and sometimes Menlo Park, CA
Contact:

Re: I was wondering...

Post by barts » Thu Dec 08, 2016 3:13 am

Each cylinder drain on this engine will have two valves, one right next to the cylinder as usual, and another a distance away. When used as a cylinder drain, both valves are open. After the engine is warmed, the valves that are a distance away from the engine are closed. This will greatly reduce the compression due to the increased cylinder volume. By placing the engine slightly after TDC with the timing shifting so that the valves are never opened, I'll move the timing adjust lever to cause the top valve to open. This should start the engine nicely w/ the reduced compression.

Key of course is warming thoroughly, and having a steam eductor on the condenser so we can start the engine w/ reasonable vacuum and an empty condenser.

I can also use a manual lever to actuate the valves; this is what Elpenor has:

http://www.elpenor.co.uk/pictures/engine/eng06.jpg

- Bart
-------
Bart Smaalders http://smaalders.net/barts Lopez Island, WA
Post Reply