Newbie- Radial lawnmower engine idea. Thoughts?

[radialnut]

Hi. Hope this isn't too whacked of an idea for my first post, but here goes.

I just saw on e-bay for sale, a RUNNING P/W R4360 Wasp Major radial engine,(http://cgi.ebay.com/ebaymotors/ws/eB...m=380002382354) and thought to myself, "But what the heak could I ever use it for?". It's just way out of my league, but for under 6 grand, I nearly fell over. That got me thinking to something smaller and more usefull, maybe, a lawnmower engine? Something affordable and useable, even if not very practical... ok. how to go about it. I wish to be a little honest here. I have a 10th grade education, and about 2 weeks worth experience with a bridgeport and a lathe combined. (but the shop teacher never let his eyes off me) Last truth would be that I dont have a huge budget surplus. Inginuity however, I have in abundance.

I have 2 concepts based around 3-5 HP b/s or tecumseh, vertical shaft engines.

1st concept involves utilizing 5 seperate and unmodified engines, mounted to a plate, using a planetary type of gear drives, where you only need to create a throttle linkage setup for fuel control, and use the gear timing to determine the firing order. this seems to be the easiest, "cheater" way of getting something feasable to run, with a basic type of a radial concept.
Here is a link to a model for sale that got me thinking...
E-bay Item number: 250223456598 (in case below link doesn't work)
http://cgi.ebay.com/Old-Original-Exp...QQcmdZViewItem

Now, obviously a few things would be different, such as the mounting plate would be rather big, basicly mounted as though on a huge mower deck, the gearing being below, using meaty gearing that could be housed almost transmission like. that would take the most engineering, but i think the right gears could be found. this would also allow for using different timing orientations for some hilarious experimentation. A great first project anyways, but probably a bit big to be any of any use.

My second, more elaborate scheme would en essence involve quartering 5 identical garden variety vertical shaft engines, welding them together making a single common housing, then re-engineering a cam type set up, a new master crank, oil sump/geared pump, pressure lube, and going on from there. Would it be easier starting from scratch, or is the there any possible way to in essence, weld 5 mower engines together to create a single, 5 cylinder monster briggs that could swing a 6 foot blade at 1800-2500 rpms, mowing an average farm in like, 10 minutes? Yea, it might need a 12 gallon gas tank to go a quarter acre, but then, the fun is in the presentation, isn't it?

Am I totally off my rocker, or does anyone here see any possibilities?

Thanks.
Radialnut

[cam1]

Why nor just take the fuel you would burn in the engines, and pour it onto the grass, you could light it, and presto, no more grass left to cut.(ever)
Seems this approach would be the most efficient path to getting the job done

ha ha

[dynosor]

The geared radial should work, but the central shaft should have a much bigger gear than each single cylinder motor. The small RC motors run at 10,000 to 25,000 RPM and a large prop or lawn mower blade cannot be run at much over 2,000 RPM.

The point is you need to gear it so that the engines run at a speed where they make usable power and the blade or prop runs where it can work without self destructing. For a lawnmower, the gears would need to be inside a dust proof box, and the intake air would need some kind of filter.


Joining single cylinder engines can be done, but getting the crank shafts aligned and joined may be the biggest challenge. Here is how the OS model engine company has made a

4 cylinder engine out of existing 2 cylinder engine components:

Engine http://www3.towerhobbies.com/cgi-bin...?&I=LXPRL5&P=7

Front crank half http://www3.towerhobbies.com/cgi-bin...?&I=LXPRU9&P=Z

Rear crank half http://www3.towerhobbies.com/cgi-bin...?&I=LXPRV0&P=Z

Note that the crank case is all new and not spliced.


Your biggest problem is that cheap single cylinder engines tend to use cantilever crank pins (attached at only one end) and non-split big end bearings on the connecting rod. Simply welding the crankshaft nose of one engine to the rear of the next crank won't work: the conrod would smack into the nose of the next crank as it goes around...
You would have to make a second web for all but one of the cranks and depending on if the cranks were permanently joined or not, split the big end bearings to assemble the engine.

It may be easier to make a new crank case and crankshaft to use the cylinders, pistons etc of the single cylinder engines. You would need conrods with split big end bearings or make your crankshaft in sections to assemble the engine...

[elmerfud]

Look at Rotecs engine, made by Paul Chirnykif.
Its a wowser, expensive yes. How do you get gas transfer through the ports if cylinders are not compressing the crankcase gas? (2 stroke)