666 and engine NUTS

Route666 · Nov 27, 2004

Ok, how about an offset cylinder? So it sits above the con rod / crank connection with the crank at 90*? That way it is possible to have less height in the whole crankshaft rotation except close to 90 ATDC because of the rod being angled, PLUS you get the power directly onto the crank instead of angled.

I know there'd probably be problems with excessive rod angles causing bore wear on the up stroke, but I think it'd be a step in the optimum direction.

EDIT: You could have a fairly substantial offset pin in the piston, then you wouldn't have to offset it as much, and the upstroke wouldn't try and rock the piston as much either.

WORTH · Nov 28, 2004

Route666 said:
Ok, how about an offset cylinder? So it sits above the con rod / crank connection with the crank at 90*? That way it is possible to have less height in the whole crankshaft rotation except close to 90 ATDC because of the rod being angled, PLUS you get the power directly onto the crank instead of angled.

I know there'd probably be problems with excessive rod angles causing bore wear on the up stroke, but I think it'd be a step in the optimum direction.

EDIT: You could have a fairly substantial offset pin in the piston, then you wouldn't have to offset it as much, and the upstroke wouldn't try and rock the piston as much either.

Actually by moving the cylinder to the side you do nothing, max compression is always gonna be at the top of the stroke, which is a line between the center of the crank and the center of the piston regardless of where the piston is.

WORTH · Nov 28, 2004

This guy has an interesting concept, when I first got to his website I thought he build MY engine, but it is completely different, he is using a seperate overhead piston as the VALVES. Pretty cool actually.

http://www.jack-brabham-engines.com/articles.htm

gingerbreadman · Nov 28, 2004

WORTH said:
This guy has an interesting concept, when I first got to his website I thought he build MY engine, but it is completely different, he is using a seperate overhead piston as the VALVES. Pretty cool actually.

http://www.jack-brabham-engines.com/articles.htm

Does his engine use the "top piston" as a 2 stroke valving system where it reveals the ports as it goes by???

-gbm-

Route666 · Nov 28, 2004

WORTH said:
max compression is always gonna be at the top of the stroke, which is a line between the center of the crank and the center of the piston regardless of where the piston is.

Only if you rotate the cylinder bore around the rotational axis of the crank. Moving it sideways can have the effect of making the shortest distance (the point at where piston TDC occurs) further around the stroke of the crank. The rod would pivot about its center as the piston nears the top of its stroke and the crank begins descending again.

My angle on it was to get the point of highest cylinder pressure (around 10-15 degrees ATDC on a standard motor) to be pointed directly perpendicular to the crank at that moment. So instead of the motor ACTUALLY being at 90 ATDC, it isn't that far advanced, thus you don't lose the pressure by increase in combustion volume caused by the piston having moved so much when it gets to 90ATDC, yet you still get the advantage of having the piston and rod pushing directly perpendicularly on the crank when you get to peak pressure.

WORTH · Nov 28, 2004

gingerbreadman said:
Does his engine use the "top piston" as a 2 stroke valving system where it reveals the ports as it goes by???

-gbm-

I think so, there really wasn't a lot of info there but that's what it sounded like to me.

WORTH · Nov 28, 2004

Route666 said:
Only if you rotate the cylinder bore around the rotational axis of the crank. Moving it sideways can have the effect of making the shortest distance (the point at where piston TDC occurs) further around the stroke of the crank. The rod would pivot about its center as the piston nears the top of its stroke and the crank begins descending again.

My angle on it was to get the point of highest cylinder pressure (around 10-15 degrees ATDC on a standard motor) to be pointed directly perpendicular to the crank at that moment. So instead of the motor ACTUALLY being at 90 ATDC, it isn't that far advanced, thus you don't lose the pressure by increase in combustion volume caused by the piston having moved so much when it gets to 90ATDC, yet you still get the advantage of having the piston and rod pushing directly perpendicularly on the crank when you get to peak pressure.

I see your point, and you may get some advantage there, it would definatly be easier to build.

6Stang7 · Nov 28, 2004

Let's clear some things up here so we can all be in the same mod of thinking.

First let's agree on why engine fire BTDC.
1. As has been said, as the engine picks up RPM more timing advancement is needed because combustion is not instantaneous. The time required to combust at 2000RPM is that same as 10,000 RPM.

2. By starting the combustion process early, we get an increase in power. Image this. You have a door and I have placed a device on it that measure how much force you open the door with. First I have you open the door as hard as you can and you produce X amount of force. I then push on the other end of the door as ask you to open as hard as you can. You push as hard as you can, but the door doesn't give because I am preventing it from opening. Then I let go of the door instantly which allows the door to open a result in Y amount of force being produced. Which is higher in force, X or Y? Y, because Y had Z amount of potential energy (PE). Y is basically equal to the X force (because both times you opened the door as hard as you could) plus the addition of the Z (the PE force). Make since?

Now, here is why I see this floating cylinder not working. If you had your whole power stroke in 90 degree, you have less of a degree rotation in which to transfer the power produced from the combustion. Once the piston starts to move up you have stopped the power stroke. In our engines, we have 180 degrees of rotation to transfer the power from the combustion into mechanical rotation. If you start the power stroke at a horizontal position, that means you would have to start it 90 degrees later then it does now. This means that you have only 90 degrees to transfer the combustion force. This might work at low RPMs, but will not work at higher RPMs.

Now the two piston per cylinder which has been brought up has no real advantage in my mind either for car applications. First, understand that even though you have two pistons per cylinder, you are exerting the same amount of force on them. You take X amount of cubic inces of air/fuel mix and you will produce on Y amount of force. The two piston design is just applying that force in a different way, not a better one. Also, this will then cause you to have ½ the cylinders WHICH IS A BAD THING! If you had a 302 CID V8 and a 302 CID inline 4, which would be better? Well, the inline 4 might have less parts and less friction, but that is not worth the vast increase in engine vibration that you would have. More cylinders results in smoother engine running.

He is what I think is the other reason. Car companies do not want to have to go through the work of designing a radically new engine block. Back in the 70’s, Sandia National Laboratories designed a variable stroke engine (in other words, variable displacement). The engine was EXTREMLY fuel efficient but was not produced because it was too hard to produce at the time, and car companies did not want to spend the money to re-tool factories for the block.

WORTH · Nov 28, 2004

6Stang7 said:
Let's clear some things up here so we can all be in the same mod of thinking.

First let's agree on why engine fire BTDC.
1. As has been said, as the engine picks up RPM more timing advancement is needed because combustion is not instantaneous. The time required to combust at 2000RPM is that same as 10,000 RPM.

First off what I have discussed sofar has nothing to do with ignition timing. We will need advance, we just don't know how much, and it is totally irrelivent in my design. At this point I don't really care what the end timing is going to be, I'm just trying to figure out if the design is solid.

2. By starting the combustion process early, we get an increase in power. Image this. You have a door and I have placed a device on it that measure how much force you open the door with. First I have you open the door as hard as you can and you produce X amount of force. I then push on the other end of the door as ask you to open as hard as you can. You push as hard as you can, but the door doesn't give because I am preventing it from opening. Then I let go of the door instantly which allows the door to open a result in Y amount of force being produced. Which is higher in force, X or Y? Y, because Y had Z amount of potential energy (PE). Y is basically equal to the X force (because both times you opened the door as hard as you could) plus the addition of the Z (the PE force). Make since?

Now, here is why I see this floating cylinder not working. If you had your whole power stroke in 90 degree, you have less of a degree rotation in which to transfer the power produced from the combustion. Once the piston starts to move up you have stopped the power stroke. In our engines, we have 180 degrees of rotation to transfer the power from the combustion into mechanical rotation. If you start the power stroke at a horizontal position, that means you would have to start it 90 degrees later then it does now. This means that you have only 90 degrees to transfer the combustion force. This might work at low RPMs, but will not work at higher RPMs.

Don't think of the power stroke in degree's think of it in inches. Does a shorter stroke engine suffer from it's shorter stroke? Or is it just a smaller engine.

Now the two piston per cylinder which has been brought up has no real advantage in my mind either for car applications. First, understand that even though you have two pistons per cylinder, you are exerting the same amount of force on them. You take X amount of cubic inces of air/fuel mix and you will produce on Y amount of force. The two piston design is just applying that force in a different way, not a better one. Also, this will then cause you to have ½ the cylinders WHICH IS A BAD THING! If you had a 302 CID V8 and a 302 CID inline 4, which would be better? Well, the inline 4 might have less parts and less friction, but that is not worth the vast increase in engine vibration that you would have. More cylinders results in smoother engine running.

He is what I think is the other reason. Car companies do not want to have to go through the work of designing a radically new engine block. Back in the 70’s, Sandia National Laboratories designed a variable stroke engine (in other words, variable displacement). The engine was EXTREMLY fuel efficient but was not produced because it was too hard to produce at the time, and car companies did not want to spend the money to re-tool factories for the block.

And on the other hand, Mazda used the Wankle

Route666 · Nov 28, 2004

WORTH said:
I see your point, and you may get some advantage there, it would definatly be easier to build.

I thought about it some more last night (in bed when I was meant to be sleeping), and because of the rod pivotting causes the later TDC, it also requires a heap of rod angle, so probably would wear too quickly and waste a lot of energy on the compression stroke at a stupid angle. I reckon it's still worth trying. Most likely for a lower rpm motor though.

666 and engine NUTS

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