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Old 11-24-2009, 01:27 AM
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Default connecting 2 two stroke engines

I saw a picture earlier this week with a moped with 2 engines directly connected to each other, and then another with 4 two stroke engines connected in a line. Does anyone have any info on what it would take to connect 2 two stroke engines, and in turn make a twin cylinder? I spent all night trying to find those pictures. So if anyone knows the ones im talking about that would be fabulous
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Old 11-24-2009, 09:47 AM
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can you find the pics?
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Old 11-24-2009, 09:53 AM
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You could machine an adapter, to simply bolt one crankshaft to the flywheel of another motor, then set the timing 180 off and your good to go (sounds a lot easier than it is). You will also have to sync the carbs or make a 2 into 1 intake, make sure there both mounted perfectly square to each other, and at the same height, etc.
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Old 11-24-2009, 11:39 AM
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Quote:
...then set the timing 180 off..
Why?
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Old 11-24-2009, 12:12 PM
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So while the engine is running, you'll have one piston going up, while the other is going down.


And I'm interested in seeing how this adaptor is made to chain the engines together side by side .....
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Old 11-24-2009, 03:17 PM
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Just chain them both straight to a jackshaft, and run a clutch/CVT from that to the axle. Easy peasy.

Quote:
make sure there both mounted perfectly square to each other, and at the same height
That will be incredibly difficult. You would need to have them SO accurately located or the adaptor would fatigue and either break itself, or brake the crankshaft.
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Old 11-24-2009, 04:12 PM
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Yes i understand most of this, i was looking for more info as to the best approach to connecting the crankshafts. i.e. keeping it aligned, strength issues. I still havn't found the pics, sorry
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Old 11-24-2009, 04:15 PM
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Quote:
Originally Posted by Russ2251 View Post
Why?
I guess i didn't make what i wrote clear, i meant set the engines 180 off from each other, not the actual ignition timing 180.
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Old 11-24-2009, 04:19 PM
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Quote:
Originally Posted by Kaptain Krunch View Post
I guess i didn't make what i wrote clear, i meant set the engines 180 off from each other, not the actual ignition timing 180.
Right so one is up being ignited, while the other is down after being ignited. Same principle as all 2 cylinder engines. This help keeps the engine moving through its strokes, kind of the idea of a flywheel, to help get the engine to its next power stroke. If both pistons were coming up at the same time, the drag of the engine might cause a "soft spot" in the return cycle of the pistons, causing it to have a dull spot, or even kill the engine.
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Old 11-24-2009, 05:26 PM
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Russ,

Am i missing something?? It makes perfect sense to me. But I'm sure you know more than me.

Oh...you deleted your post.
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Last edited by Kaptain Krunch; 11-24-2009 at 05:26 PM. Reason: Noticed the post i answered was gone
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Old 11-24-2009, 05:28 PM
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Quote:
This help keeps the engine moving through its strokes, kind of the idea of a flywheel, to help get the engine to its next power stroke. If both pistons were coming up at the same time, the drag of the engine might cause a "soft spot" in the return cycle of the pistons, causing it to have a dull spot, or even kill the engine.
Sounds good in theory, but in fact is not true. Both my engines fire at the same time. No "soft spots", no stalling.
Originally I thought this timing thing might be a problem. It's anything but.
Engines actually self synchronize...that is, they both fire at the same time.
I would have thought it would be a random thing depending on when/where clutches lock up.
The physics behind this has yet to be explained to me.
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Old 11-24-2009, 05:36 PM
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Quote:
Originally Posted by Russ2251 View Post
Sounds good in theory, but in fact is not true. Both my engines fire at the same time. No "soft spots", no stalling.
Originally I thought this timing thing might be a problem. It's anything but.
Engines actually self synchronize...that is, they both fire at the same time.
I would have thought it would be a random thing depending on when/where clutches lock up.
The physics behind this has yet to be explained to me.
I'm thinking it might have to do with the harmonic vibrations possibly?
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Old 11-24-2009, 06:50 PM
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Quote:
Originally Posted by Russ2251 View Post
Sounds good in theory, but in fact is not true. Both my engines fire at the same time. No "soft spots", no stalling.
Originally I thought this timing thing might be a problem. It's anything but.
Engines actually self synchronize...that is, they both fire at the same time.
I would have thought it would be a random thing depending on when/where clutches lock up.
The physics behind this has yet to be explained to me.
Yes but yours are two separate engines (if your referring to your twin duraforce go kart) and therefore are not connected to the same crankshaft, Your engines have the benefit of having seperate clutches. Where if at any point one were to start stalling, the engine rpm would drop, and therefore have the clutch disconnect it from the axle were it will most likely regain from its stumble, and also not drag down the other engine. In a 2 cylinder engine, if both cylinders were moving up and down in sync, and one experienced a hiccup during its power stroke, then on its way back up, both cylinders would be relying on the power stroke from a single cylinder. This would be even more pronounced with a 4 stroke engine, that has 3 strokes of non power, creating more drag and possibly killing the engine.

As for the reason your kart's engines run at the same time, i believe that has alot to do with the live axle, and use of separate clutch's (i believe thats what you karters call basically the whole rear axle moving, right?) I would assume that at lower rpm when the clutches are both partially engaged, which ever engine is creating less power will slip the clutch until they are running at the same power stroke. This is probably due to the large mass of the axle and wheel rotating assembly that doesn't like torque of 2 engines pulling the right side of the axle, then the left, or vise-versa. So it probably creates a larger resistance on the less powerful (possibly more) engine down until they are in sync, and the axle is experiencing almost equal amounts of torque on both sides of the axle: at the same time. I deduce this because if both engines were on different axles i bet the engines wouldn't act in this manner, without the help of a steering wheel which you could steer toward the direction of the more powerful engine (i.e. drive straight) and in turn create that same resistance (or boost) to the less powerful engine, so the wheels will run the same speed . This wouldn't be the case with a twin cylinder engine as much because the crankshaft of both cylinders are so close to each other, and the counterweights are designed to deal with this.
Makes me wonder if the engines would be more efficient if the chains were right next to each other on the axle and centered. Russ flip one of those engines around!
Anyway there's my 2 cents and 10 minutes worth of rambling, go ahead and pick a bone (i recommend my left collar bone, as it has a titanium plate on it
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Old 11-24-2009, 07:14 PM
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Huh?
At any rate, I posted this question to a group of physics "experts".
May take up to two weeks to get the answer.
I'll post response here if and when they answer it.
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Old 11-24-2009, 07:35 PM
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Ya sorry its been a long past few weeks. I will ask my physics professor as well as some of the cats in the engineering department. Gotta get SOME use out of all this tuition im spending.
Also don't forget there is a good chance you'll get an answer that only applies if the engine is operating in a vacuum! Or more seriously, if the engine and axle operated 100% efficiently. **** physicians
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Old 11-24-2009, 10:42 PM
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Quote:
This would be even more pronounced with a 4 stroke engine, that has 3 strokes of non power, creating more drag and possibly killing the engine.
LOL, unlikely. 2 engines stuck together and firing simultaneously may have slightly more drag, but they also have twice the power. While I agree that it would be better to have them firing alternately for reasons of balance and smoothness, i doubt it would make much difference to overall performance.
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Old 11-24-2009, 11:42 PM
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Quote:
Originally Posted by Kaptain Krunch View Post
I guess i didn't make what i wrote clear, i meant set the engines 180 off from each other, not the actual ignition timing 180.
thats incorrect if u wont to make power with a 2 stroke thay will make more power if they are 0* apart so that both pistons will be at TDC at the same time it might sound better to go 180* apart but in fact it is not the only benafit would be that the engine would be more balanced.
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Old 11-25-2009, 07:47 AM
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Quote:
Originally Posted by dan View Post
thats incorrect if u wont to make power with a 2 stroke thay will make more power if they are 0* apart so that both pistons will be at TDC at the same time it might sound better to go 180* apart but in fact it is not the only benafit would be that the engine would be more balanced.
If the engines are 180 off, it would be much smoother, and if my thinking is correct, they would wind out faster, do to the combustion of one engine helping the other through the compression/exhaust stroke.
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Old 11-25-2009, 08:10 AM
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Quote:
Sounds good in theory, but in fact is not true. Both my engines fire at the same time. No "soft spots", no stalling.
Originally I thought this timing thing might be a problem. It's anything but.
Engines actually self synchronize...that is, they both fire at the same time.
I would have thought it would be a random thing depending on when/where clutches lock up.
The physics behind this has yet to be explained to me.
I still think my explanation in your thread regarding this was corect, but It'll be interesting to hear what those physics "experts" come up with.
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Old 11-25-2009, 08:55 AM
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You talking about those 2/4 Zenoah's hooked up as one?
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