Are there V-Twin engines?

[Cavi Mike]

I would absolutely love to put one in my chopper build.

 

[motorpsycho]

there are no small v-twin 2 strokes, but someone was trying to develop one last year.
the only v-twin choices out there, and the much bigger v-twin 4 strokes for lawn tractors.

 

[Cavi Mike]

There's no real way to make a 2-stroke V-twin but I was hoping there was a small 4-stroke available. Since I'm a machinist by trade I think I'm going to attempt to build one myself using plans I found here, I'm just gonna up-size it a little bit because 32cc just ain't gon' cut it.

 

[motorbikemike45]

I don't know why you say there's no real way to make a 2 stroke V-twin. All it takes is a metal web divider separating the crankcase into 2 halves for each piston with either a bearing and seal or just a seal in the center where the crackshaft goes through. You will need a separate carb and intake for each cylinder, or a single carb and separate intake and reed valves for each cylinder and an exhaust from each cylinder's port. There have been thousands of 2 stroke multi-cylinder engines in motorcycles, cars, and even diesel 2 stroke multis on big ships. I saw a 5 cylinder opposed piston 2 stroke diesel on a Polish freighter thay was huge. The cylinder bore exceeded 6 feet. The system is the same no matter the size, number of cylinders, or piston configuration. Think of it as a series of single cylinder engines butted up against each other and sharing a common crankshaft. Someone on here showed someone building/has built one using 2 happy time jugs and rotated so they were in V twin configuration. I can't remember for sure, but I think they got it running and posted a vid on youtube.

 

[Cavi Mike]

In order to prevent catastrophic vibration, V-twins need to share the same journal which makes separating the crankcase unfeasible.

 

[motorbikemike45]

While the two conecting rods in a V-twin engine usually do share a single crank journal, there is no reason not to have two conecting rods on two separate crank throw journals that happen to be in the same plane as if they were on a common journal. Granted, it makes for a more complicated crankshaft, but it is most certainly doable.

 

[Greybeard]

If you look at marine use, there are V4, V6, and V8 two strokes in outboards. They are just Vtwins stacked.
I think the one that was being developed was a crankcase with two cranks, not that unusual concept as engines have been joined before with a single casting and two cranks.

 

[motorpsycho]

exactly! you can hook engines together vis the cranks.
you can have 4 engines couped together through the crankshafts, but the issue is balancing them all.
each engine will develop it's own vibration so dampemning and balancing all of the engines as one is what needs to be done.
there have been many dragsters that run 2-4 engines hooked together crank to crank.
look at the big tractor pullers with 4-6 engines.
in reality you can do whatever you want if you know how to make it work and how to balance it all out.
vibrations can easily kill 2 engines hooked together.

 

[Cavi Mike]

So the engine ends up heavy, loaded with extra moving parts, very complicated and bulky. Doesn't that defeat the purpose of going 2-stroke? I know if size isn't a factor you can just run them inline like a ship or sportbike but obviously that's unfeasible on a bicycle.

 

[suitcasejefferson]

While the two conecting rods in a V-twin engine usually do share a single crank journal, there is no reason not to have two conecting rods on two separate crank throw journals that happen to be in the same plane as if they were on a common journal. Granted, it makes for a more complicated crankshaft, but it is most certainly doable.

Actually, by using offset crankpins, a v-twin can be made to run as smooth as a parallel twin. Using a single crankpin for both cylinders is why Harley engines sound so good (and also shake like crazy, and don't make much power for their size) There is no mechanical reason a 2 stroke v-twin could not be built, but a 4 stroke would be better. It would be one very expensive engine for it's size, it cost a lot more to build a v-twin than a parallel twin because it requires 2 of everything, most of which can be shared on a parallel twin. Then there is the problem of making a v-twin fit inside a bicycle frame. They take up a lot more space than a single of the same displacement.