crossplane crank; works for yamaha!

[spectre6000]

Are we trying to get two cylinders to fir simultaneously as if it were a two cylinder engine? I.e., 1/3 fire (or 1/4) and then the other pair? or 1/2 then 3/4? The natural balance of the flat four engine comes in that opposing cylinders travel in opposing directions simultaneously and cancel out each other's kinetic energy that would try to move the engine one way or the other. As long as one cylinder on each side is traveling opposite one on the other you should be fine. As for the firing balance... I don't know that it wouldn't be more balanced to have 1/3 fire, then 2/4 as the motion of the cylinders is latitudinal and not fore and aft...

You could do a four lobe cam running that way is you make cam symmetrical along the shaft (like an elongated oval with the shaft at the center) and change the cam/crank gear ratios to 1:4... I think that's it if I understand the intent correctly... It would require some heavy machining of the case for clearance, and maybe some creative case modification with an aluminum case (so it's weldable).
_________________
Jason Hopper

-'58 German Market Deluxe Beetle (in progress)
-'84 M1009 CUCV
-'81 K10
"Buy the best, cry once." -Gene Berg
"A cheap man will always buy the cheapest thing available, and then buys another one hoping for a better result, and then spends the rest of his life in misery complaining about it. A thrifty man will buy a good part once and never think about it again." -RockCrusher
"Don't feed the Shitty Parts Monster!" -Me

[modok]

The four lobe cam would work fine, and I would not alter the firing order either, just the....... spacing rather. It would be odd fire but still 4321
Both the cam and crank can be cut in half, turned 60 or 90 degrees, and put back together again and it will work. granted, you'd also need to modify the distributor.
This would reduce the torque shake from all four stopping and starting at once. I believe that is why yamaha did it, smoother power for better traction.

I did hear of a "big bang" two cylinders fire at once vw airplane engine being built. WHY, I don't know. and the crazy guys making them into 6 and 8 cylinder engines have welded cranks together.
just a matter of motivation

[wompninja]

I really like the "big bang" idea. it seems like it would smooth out the engine substantially because the force generated by ignition would almost be cancelled out because they are opposed and firing at the same time. I.E. two shotguns butt to butt fired at the same time. Hypothetically the kick back would be cancelled out.
_________________
Pics of my 1970 Satin Black Type 1 build

[modok]

um, no, the firing forces twist the flywheel, not push the engine sideways

this is very easy to test
go down the road and get going some rpm
Or put it on a dyno
floor it, observe vibration
let off, observe vibration

It is easy to remove the forces of the cylinders firing
Changing the crank is not so easy to test
the altered crank makes the flywheel run a more constant speed since the pistons don't all stop and go at once

[wompninja]

Very true, there are definitely simpler remedies for engine shake.
_________________
Pics of my 1970 Satin Black Type 1 build

[modok]

oh....wait a minute.... what I get it now.
With the big bang it would reduce the load on the main bearings, yeah, ok

But when 2 and 4 fired at once it would wind up the crank a lot since they are farther from the flywheel....... that could be a drawback

[wompninja]

If you beef up the bearings and put type 4's in I think it would work. Team that up with lightened flywheel and a heavier pulley/harmonic balancer and you've possibly got a smooth engine.
_________________
Pics of my 1970 Satin Black Type 1 build

[nsracing]

[RockCrusher]

[bdkw1]

[mark tucker]

I think you guys B nuts. but I reckon it,s better than chewing each other's asses. well sort of.hmm why not just go turbine??or steam turbine, or wankel,with a titanium wank?

[wompninja]

Ok, what about something like this? Don't mind the fact that I used a really old engine for the picture. I call it the X8, I guess it's a cross between a rotary and a v8.

_________________
Pics of my 1970 Satin Black Type 1 build

[spectre6000]

Pushrod/crank clearance issues... Overhead cam it Carerra style though... If you have the ability to cast/machine at that level there's some merit. It wouldn't work with an upright cooling system; you'd need a type 3/4 type set up where the air blows over the cylinders/heads from the front.

Reminds me of an X-wing.
_________________
Jason Hopper

-'58 German Market Deluxe Beetle (in progress)
-'84 M1009 CUCV
-'81 K10
"Buy the best, cry once." -Gene Berg
"A cheap man will always buy the cheapest thing available, and then buys another one hoping for a better result, and then spends the rest of his life in misery complaining about it. A thrifty man will buy a good part once and never think about it again." -RockCrusher
"Don't feed the Shitty Parts Monster!" -Me

[didget69]