Oddball engines and prototypes

[WilDun]

I know it's a little off the two wheel track and it's possible that it's been mentioned before, but ……….. this has to be the ultimate in fun and even I might be able to use it!

https://www.youtube.com/watch?v=qSMWEd54NcA

[guyhockley]

Just found out about these. Most outboards have reed valves into the bottom of the crankcase but Mr Martin thought different, apparently. I've seen automatic inlet valve two strokes in museums and books but these are timed by eccentrics on the crank.

https://www.joeoutboard.com/manuals/martin-manuals.html

[Pursang]

[QUOTE=guyhockley;......these are timed by eccentrics on the crank.[/QUOTE]

That's keeping it simple, a bit more work to change the timing, but!

Cheers, Daryl.

[Pursang]

I know it's a little off the two wheel track and it's possible that it's been mentioned before, but ……….. this has to be the ultimate in fun and even I might be able to use it!

That does look like a whole lot of fun!!! So long as it's fitted with a decent 2 stroke engine.

Cheers, Daryl.

[Grumph]

Just found out about these. Most outboards have reed valves into the bottom of the crankcase but Mr Martin thought different, apparently. I've seen automatic inlet valve two strokes in museums and books but these are timed by eccentrics on the crank.

Perkins in the UK did something very similar in the 50's. Drawing and pics in Irvings 2 stroke book - which i've misplaced.

Friend of my father's had a Perkins 40HP with this setup. Went quite well too.

[WilDun]

That does look like a whole lot of fun!!! So long as it's fitted with a decent 2 stroke engine.

Cheers, Daryl.

That could probably be done I'm sure - a really giant leap forward.
Not many motorcycle type two strokes available now, (everything is dictated by fashion - nothing is dictated by commonsense!).

[tjbw]

Just found out about these. Most outboards have reed valves into the bottom of the crankcase but Mr Martin thought different, apparently. I've seen automatic inlet valve two strokes in museums and books but these are timed by eccentrics on the crank.

https://www.joeoutboard.com/manuals/martin-manuals.html

Shouldn't there be a seal between the crankcase chambers?

Martin engines were manufactured by National Pressure Cooker Company. I think the engines had cams on the crankshaft, as indicated on these patent drawings.

[guyhockley]

Older outboards with bush main bearings often don't have any additional crank seals and I think the crank is running directly in the crank case as a centre bearing. The cams are either side of that.
Interesting that it's a horizontally split case when the Japanese hadn't invented them, yet!

[guyhockley]

That could probably be done I'm sure - a really giant leap forward.
Not many motorcycle type two strokes available now, (everything is dictated by fashion - nothing is dictated by commonsense!).

Quite a few people in the UK have fitted bike engines into mobility scooters, Colin Furze, for example, but I think they have all been foul strokes.

[husaberg]

Older outboards with bush main bearings often don't have any additional crank seals and I think the crank is running directly in the crank case as a centre bearing. The cams are either side of that.
Interesting that it's a horizontally split case when the Japanese hadn't invented them, yet!

When you look at the patent pic it looks as if it follows common auto practice of separate sump alhough in this case its half the crankcase
I read the other day that Suzuki and Kawasaki never line bored the twins and threes main bearings as one operation.
Where as Yamaaha did and for that reason. Yamaha lab seals dont last in these other bikes without correction of this.
It turns out the rubbers seals are much more forgiving for potential misalignment. Made sense to me.
I think the YR3 was the first Yamaha with horizontal split cases about 1969

[guyhockley]

There was a hilarious story in one of the UK newspapers, years ago, about the decline of the British bike industry. The writer had obviously misunderstood what he had been told. He said that British bikes had vertically split petrol tanks that always leaked and the Japanese had introduced horizontally split tanks to keep the stuff in.

[guyhockley]

When you look at the patent pic it looks as if it follows common auto practice of separate sump alhough in this case its half the crankcase
I read the other day that Suzuki and Kawasaki never line bored the twins and threes main bearings as one operation.
Where as Yamaaha did and for that reason. Yamaha lab seals dont last in these other bikes without correction of this.
It turns out the rubbers seals are much more forgiving for potential misalignment. Made sense to me.
I think the YR3 was the first Yamaha with horizontal split cases about 1969

There was or is a website about a bloke racing an early Suzuki twin. At one point he had the cases line-bored to take larger, Yamaha main bearings. If I remember right the poor machinist had a bit of bother because the cast in iron/steel inserts were all over the place.

[guyhockley]

Not quite how I remembered...

http://www.t20suzuki.com/racing.htm#TZcrank

[Frits Overmars]

Seen in the Farcebook group '2Stroke research & development': the RSW125 8-Valve. A dazzling percentage of visitors sang the praise of the oval-piston Honda without even noticing the Aprilia engine underneath. I hesitated between laughing and weeping.

[guyhockley]

9 valve, surely?