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Old 09-26-2003, 10:01 PM   #46
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Talking Hell ya fysics

He who masters Newton's laws, wins. Not only is reducing rotational mass important but drivetrain friction is too. Thats why shaft cars have the biggest advantage over belt cars. Think about it, on both cars there is ofcourse friction between the spur and pinion gear which is about 3 teeth. Then in a shaft car's transmission there is very little friction due to the 3-4 teeth touching between the ring and pinion gears. (compared to the belts touching half of each of the pulleys) Then ofcourse there is alot of friction in the bearings. (which switching to ceramic bearings would help) By reducing rotational mass and friction even on a heavy (ROAR spec weight) car can accelerate very fast. I would rather drive a little heavier car with a very efficent drive train compared to a very light car that has alot of drive train friction. Lightening the car's total mass doesn't improve acceleration much but reduces traction and changes the handling ability of the car. The extra total mass is the inertia that you want because it carries you through the turns, not the extra rotational mass.
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Old 09-27-2003, 12:10 AM   #47
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Rotating weight is very important; the effective mass is 4 times the static mass. So if you trim .5 oz of rotating mass it's the same as losing 2 oz of total mass. 2 oz out of 50 is 4%. That's a lot. Believe me I tried racing a 1 oz heavy TC3 last year and it was lacking in acceleration. The only thing is to reduce weight that much you have to use the plastic diffs and cvds which may twist 5%, and I have seen a lot of fast guys running all aluminum/titanium drivetrain and win.
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Old 09-27-2003, 10:54 AM   #48
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what about the centripetal force?

a lighter car will NOT have less traction when cornering. while it may have less tractive force due to the reduced normal force (down), the car will also have a reduced centripetal force (radial) as a result of its lighter weight. for most of us, "traction" is the overall ability of the car to maintain it's desired path. all other parameters held constant, reducing translating weight will not hinder the car's ability to corner.
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Old 09-27-2003, 11:04 AM   #49
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check it.

http://serverdown.leosandbox.org/Hom...ment5/exp5.pdf
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Old 09-29-2003, 01:54 PM   #50
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a lighter car is affected less by g-forces thus it can corner quicker and accelerate quicker. a car that whiehs more is affected by inertia more so you use up more tires and have to slow down more to make a corner plus it takes more battery power to get back up to speed again.
lighter car is faster all around period!
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Old 09-29-2003, 02:38 PM   #51
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Default go light go fast

light is fast but time on the track and batteries burned will make up for any drive train that even NASA can build with unlimited budget .....

go to the local track pay the practice fee and get rolling there is absolutely no substitute for track time ..........

prove me wrong and i will give you a chocolate chip cookie ...
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Old 09-29-2003, 02:40 PM   #52
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even for the pro's tracktime is a must!
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Old 09-29-2003, 02:46 PM   #53
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Quote:
think about what you are saying- a flywheel has nothing to do with the compression of an engine,trust me. i too am a certified tech (Mercruiser marine engines) i happen to know a little about flywheels and compression-which by the way have nothing to do with each other
OK, Imagine for a moment, if you can, that Enertia doesn't exist. Therefore, if you threw a ball, as soon as it left your hand it would stop. Also, you would be able to drive into a brick wall at 100 mph, and nothing would happen. (Just hang in there)

In a FOUR stroke ingine, the cylinders only fire once every other cycle. It is necessary for the ENERTIAL energy to push the piston pack UP to exhaust burned gasses, and pull in new fuel, and then COMPRESS the fuel/air mixture on the pistons way back up. This mechanism relys on enertia to complete the cycle before firing again. And if your thinking the other cylinders are firing while this one is doing its thing, think about a 1 piston engine...

SOOOO...... If you increase the amount of enertial energy available to help complete the firing cycle, then is is easy to assume that with more energy available to push the cylinder back up on its compression stroke, that the pressure can be increased, thus yeilding more energy. IE it would allow you to have higher compression without stalling the engine.

So ask yourself: Is enertial energy and compression related...? Not directly. But you can't have one without the other.
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Old 09-29-2003, 03:00 PM   #54
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pit crew you are dwelling in a subject you are not fully knowledgable about and engine does not need a flywheel to run. and it does nothing to compression. .
a heavier fly wheel or lighter flywheel doesnt control how much! it dont add or subtract compression the reason behind a flywheel is to make the engine run smoother , besides having the clutch attached to including the starter ring which doesnt need to be at the flywheel.
take for instance the porsche 944's the the motor upfront and the transmission is in the rear along with the clutch mechanisim. which has a flywheel aswell!
compression is controlled by bore,stroke, cc in cylinder combustion chamber determines compression.
static compression is controlable via valve,port,camshaft size. which is another subject!
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Old 09-29-2003, 03:13 PM   #55
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Quote:
Originally posted by PitCrew
OK, Imagine for a moment, if you can, that Enertia doesn't exist. Therefore, if you threw a ball, as soon as it left your hand it would stop. Also, you would be able to drive into a brick wall at 100 mph, and nothing would happen. (Just hang in there)

In a FOUR stroke ingine, the cylinders only fire once every other cycle. It is necessary for the ENERTIAL energy to push the piston pack UP to exhaust burned gasses, and pull in new fuel, and then COMPRESS the fuel/air mixture on the pistons way back up. This mechanism relys on enertia to complete the cycle before firing again. And if your thinking the other cylinders are firing while this one is doing its thing, think about a 1 piston engine...

SOOOO...... If you increase the amount of enertial energy available to help complete the firing cycle, then is is easy to assume that with more energy available to push the cylinder back up on its compression stroke, that the pressure can be increased, thus yeilding more energy. IE it would allow you to have higher compression without stalling the engine.

So ask yourself: Is enertial energy and compression related...? Not directly. But you can't have one without the other.
wrong again Pitcrew. each cylinder fires every cycle in a 4 stroke engine.not every other cycle.5 events happen every cycle:INTAKE,COMPRESSION,IGNITION,POWER,EXHAUST -EVERY CYCLE,NOT EVERY OTHER CYCLE. you have two certified techs explaining that flywheels have nothing to do with compression.myself and speedxl. and to emphasize what he said,you really dont have the knowledge in this area to argue your point. i am not saying you are a bad guy,but we know what we are talking about
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Old 09-29-2003, 05:12 PM   #56
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Thanks

Last edited by PitCrew; 09-29-2003 at 05:52 PM.
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Old 09-29-2003, 07:42 PM   #57
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Quote:
Originally posted by PitCrew
OK, Imagine for a moment, if you can, that Enertia doesn't exist. Therefore, if you threw a ball, as soon as it left your hand it would stop. Also, you would be able to drive into a brick wall at 100 mph, and nothing would happen. (Just hang in there)

In a FOUR stroke ingine, the cylinders only fire once every other cycle. It is necessary for the ENERTIAL energy to push the piston pack UP to exhaust burned gasses, and pull in new fuel, and then COMPRESS the fuel/air mixture on the pistons way back up. This mechanism relys on enertia to complete the cycle before firing again. And if your thinking the other cylinders are firing while this one is doing its thing, think about a 1 piston engine...

SOOOO...... If you increase the amount of enertial energy available to help complete the firing cycle, then is is easy to assume that with more energy available to push the cylinder back up on its compression stroke, that the pressure can be increased, thus yeilding more energy. IE it would allow you to have higher compression without stalling the engine.

So ask yourself: Is enertial energy and compression related...? Not directly. But you can't have one without the other.
If inertia didn't exist you would be able to move that hand to throw that ball...
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Old 09-29-2003, 08:35 PM   #58
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Default Drivetrain Weight/Mass - Does it matter?

Guys;

As an old time Drag racer (68, 440ci Road Runner), I can tell you personally that very minor changes in rotating mass can have a SIGNIFICANT impact on accelleration of a Vehicle.

Obviously the laws of Physics would also apply to our R/C vehicles as well. So with everything else being equal, the Car with the lighter Drivetrain, will accellerate quicker.
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Old 09-30-2003, 12:23 PM   #59
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Sean, in Pitcrew's defence I believe he meant stroke not cycle. i.e. every other time the piston is on it's down stroke it produces power.

Is this not why 2 stroke engines require less flywheel effect, every downward stroke of the piston is a power producing stroke so less inertia is needed to continue the cycle. Been trying to explain to a few peeps at work, they can't get they're head round a 2 stroke engine to save their lives, and they're the maintenance crew.

//Stu
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Old 09-30-2003, 01:00 PM   #60
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Yes 4 stroke. up(compression), down(fire) up(exhaust) down(intake). repeat.

That is exactly what I have been trying to say. At low RPM the momentum of the flywheel is needed to get the piston up and down on the exhaust and intake cycle before the compression then power.

all I said earlier is that with a heavier flywheel, there is more power to push the piston back up on the compression stroke. If you had a really light flywheel, and really high compression, the engine would stall at low RPM.

Its a mute point at this time.

Thanks for the Defense.
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