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Mike Spencer Mike Spencer is offline
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Posts: 164
Default OT Impact wrench design



Ed Huntress writes:

Bear in mind that a "hit-and-miss" engine is not the same thing as
these Canadian "make-and-break" engines. The Acadia fires on every
cycle; it doesn't idle for multiple revolutions, like a hit-and-miss.
And hit-and-miss engines were 4-strokes; the Acadia type
make-and-break is a 2-stroke.


You've more or less answered your own question about whether my 10 HP
stationary runs in reverse. The small marine engines were 2-stroke
but the stationary ones were four-stroke. My 10HP is 4-stroke and
doesn't run in reverse.

Hit-and-miss engines could have either spark plugs or the low-voltage
"igniter" ignition, which was a pair of points that opened and created
a spark (actually, an arc, but we won't quibble). The make-and-break
always has that type of ignition, and is named for it.


Some had a magneto. Some with a magneto used a separate spark plug
while others fired the magneto spark into a "points"-like device very
like the "igniter" to which you refer. Others had a battery and
"spark coil" which discharged as a spark/arc when the igniter points
opened instead of a mageneto.

My 10 HP Acadia had a magneto of the second type which worked when I
got it in the early 70s but had disintegrated (despite being boxed up
in a dry place) when I went to fix it up circa 2004. So I replaced
the magneto unit with an igniter from another engine and home-rolled
coil, modified the timing train with a hand-forged part and it now
runs fine again.

As Mike says on his webpage, there were other brands, which were once
very popular for working boats in Mike's neck of the woods.

Here's one, an Atlantic, in operation on a boat:


I think that's the Lunenburg Foundry brand. Still in business but the
iron foundry is long since closed. I used to get my forge firepots
there.

https://www.youtube.com/watch?v=UxGw...eature=related

As you can see, it moves that boat along pretty darned well for 4 hp.
The low rpm was well matched to the low speed of those displacement
hulls, which results in efficient propellers.


Circa 1970, I watched an old guy in a small open fishing boat come
into a local little harbour with such a single-banger engine
running. He was standing in the boat; stopped the engine, kick-started
it in reverse. Never looked up from the floor of the boat again as he
tidied some gear, collected his lunch bucket and jacket, picked up a
line while stopping the engine as he walked past, stepped up on the
bow thwart and onto the wharf without breaking his stride just as the
moving boat touched it. Whipped the line around a post and went
home. I guess he must have done that exact thing in exactly the same
boat and same place maybe 18,000 times in the past 60 years and didn't
*have* to look to see where he was going.

--
Mike Spencer Nova Scotia, Canada