Drivetrain Weight/Mass - Does it matter?
09-25-2003, 01:00 PM
#31
Tech Initiate
Here's a good read for all you techno buffs.
Click me
Basically, any mass lost on your drive train has a higher percentage effect on your car than static mass lost off the rest of the car.
BUT
Here's one that'll confuse you all. At the TC Euro's in 2002 a top line driver who shall remain nameless actually ADDED weight to his drive train. I know this for a fact because I saw his front diff after the meeting, it was packed with blue tack. Why you ask? He said it enabled him to use less throttle through some of the mid speed sections on the track to save his cells and it also kept the car more stable in the corner. He made the A-main. Admittedly this was on a very large track with very few acceleration points but the theory was sound, flywheel effect.
On a side note, it has been rumoured that the latest spec Honda Civic Type R actually has a heavier flywheel to improve it's 0-60 time. Figure that one out if you will, person with the best guess wins a cookie
//Stu
Click me
Basically, any mass lost on your drive train has a higher percentage effect on your car than static mass lost off the rest of the car.
BUT
Here's one that'll confuse you all. At the TC Euro's in 2002 a top line driver who shall remain nameless actually ADDED weight to his drive train. I know this for a fact because I saw his front diff after the meeting, it was packed with blue tack. Why you ask? He said it enabled him to use less throttle through some of the mid speed sections on the track to save his cells and it also kept the car more stable in the corner. He made the A-main. Admittedly this was on a very large track with very few acceleration points but the theory was sound, flywheel effect.
On a side note, it has been rumoured that the latest spec Honda Civic Type R actually has a heavier flywheel to improve it's 0-60 time. Figure that one out if you will, person with the best guess wins a cookie
//Stu
09-25-2003, 01:08 PM
#32
I think it is just magic.
09-25-2003, 01:12 PM
#33
Originally posted by Ragman
Here's a good read for all you techno buffs.
Click me
Basically, any mass lost on your drive train has a higher percentage effect on your car than static mass lost off the rest of the car.
BUT
Here's one that'll confuse you all. At the TC Euro's in 2002 a top line driver who shall remain nameless actually ADDED weight to his drive train. I know this for a fact because I saw his front diff after the meeting, it was packed with blue tack. Why you ask? He said it enabled him to use less throttle through some of the mid speed sections on the track to save his cells and it also kept the car more stable in the corner. He made the A-main. Admittedly this was on a very large track with very few acceleration points but the theory was sound, flywheel effect.
On a side note, it has been rumoured that the latest spec Honda Civic Type R actually has a heavier flywheel to improve it's 0-60 time. Figure that one out if you will, person with the best guess wins a cookie
//Stu
Here's a good read for all you techno buffs.
Click me
Basically, any mass lost on your drive train has a higher percentage effect on your car than static mass lost off the rest of the car.
BUT
Here's one that'll confuse you all. At the TC Euro's in 2002 a top line driver who shall remain nameless actually ADDED weight to his drive train. I know this for a fact because I saw his front diff after the meeting, it was packed with blue tack. Why you ask? He said it enabled him to use less throttle through some of the mid speed sections on the track to save his cells and it also kept the car more stable in the corner. He made the A-main. Admittedly this was on a very large track with very few acceleration points but the theory was sound, flywheel effect.
On a side note, it has been rumoured that the latest spec Honda Civic Type R actually has a heavier flywheel to improve it's 0-60 time. Figure that one out if you will, person with the best guess wins a cookie
//Stu
The cookie better have chocolate chips
09-25-2003, 03:15 PM
#34
Only thing I can add to the discussion is the age old shaft vs belt debate. One of the disadvantages to the shaft system is that most shaft cars have greater rotating mass than most belt cars. Also a heavy enough shaft will make the car have a gyroscope effect.
09-25-2003, 03:58 PM
#35
for what its worth i heard a lot of referenc to real drive trains and transmissions,and the horsepower lost through the drive train.rotating mass is not the big culprit here,its friction and drag,you would be suprised how much power is robbed just from the transmission fluid. take for example(and i know i am talking boats,just think drive train)marine engines,just like car engines the HP rating is taken at the crank not the prop.and the same thing huge power drops from crank to propshaft. in racing applications they found that it was friction,not rotating mass robbing power wich prompted the development of dry sump outdrives. instead of the gears turning through a sump of oil they inject a light film on the drive gears,just enough to keep them lubricated. just this alone made for significant propshaft horse power increases. i think people tend to under estimate gear friction
09-25-2003, 04:25 PM
#37
thanks, but yeah, well i wouldn't have to get so creative if you two guys weren't so fast.
ray brought up a great tuning parameter that has more hype about it than richard simmons in a tank top....?
really, chassis flex is about the only thing anyone seems to care about indoors. i may have to add to the recent onslaught of hi-tech threads with that one.
beware...
yeah, about the richard simmons thing... i don't understand why you guys like him so much.
ray brought up a great tuning parameter that has more hype about it than richard simmons in a tank top....?
really, chassis flex is about the only thing anyone seems to care about indoors. i may have to add to the recent onslaught of hi-tech threads with that one.
beware...
yeah, about the richard simmons thing... i don't understand why you guys like him so much.
09-25-2003, 04:49 PM
#38
Herminator,
My guess would be that the "flywheel" effect is used to help push the cylynders up on the compression stroke, allowing greater compression.
Maybe not...
My guess would be that the "flywheel" effect is used to help push the cylynders up on the compression stroke, allowing greater compression.
Maybe not...
09-25-2003, 05:14 PM
#39
Originally posted by PitCrew
Herminator,
My guess would be that the "flywheel" effect is used to help push the cylynders up on the compression stroke, allowing greater compression.
Maybe not...
Herminator,
My guess would be that the "flywheel" effect is used to help push the cylynders up on the compression stroke, allowing greater compression.
Maybe not...
)so you are still drawing in and compressing the same volume of air. the only way to increase the volumetric efficency of a given engine design is forced air induction(super charger) and yes you can change compression making a high compression engine but thats a whole different topic all together
09-25-2003, 05:22 PM
#40
I yjink he means that it keeps the momentum up.
09-25-2003, 05:26 PM
#41
Regarding the Honda, the answer is that the heavier flywheel allows the engine to spool down less during the shifts, losing fewer RPM, and therefore spending more time at a higher point on the HP curve. Admittedly the wheels chirp a little more during shifts, but is that so bad? 
I know because I did that experiment a few years ago on my very own SCCA Solo 2 Honda Civic.
It also helps out dynamic fuel economy, which is my personal theory.
On a long track that flows well, there's not much of a good reason to go with a flyweight driveline. A little more mass, as clase to the motor as possible (before much reduction happens) will do just what that UK racer says, conserve power and carry more speed through some corners. It would be worthless, or even detrimental, on tight twisty tracks of course, but an advantageous setup would have variable driveline mass to control the flywheel effect. Once everything else was dialed properly...
-dave
I know because I did that experiment a few years ago on my very own SCCA Solo 2 Honda Civic.It also helps out dynamic fuel economy, which is my personal theory.
On a long track that flows well, there's not much of a good reason to go with a flyweight driveline. A little more mass, as clase to the motor as possible (before much reduction happens) will do just what that UK racer says, conserve power and carry more speed through some corners. It would be worthless, or even detrimental, on tight twisty tracks of course, but an advantageous setup would have variable driveline mass to control the flywheel effect. Once everything else was dialed properly...
-dave
09-26-2003, 06:29 AM
#42
Just wanna put in my two cents...
With an electric engine, which is able to stop and start at will, a flywheel is not necessary, if you could have a zero-mass drivetrain, it would work fine. A gas/nitro engine, on the other hand, does need a flywheel of sorts to keep the crankshaft turning until the next power cycle.
In terms of the drivetrains of an RC car, lighter rotating mass will make it much more responsive in terms of acceleration and deceleration. this means that you press the trigger, the car will reach the required speed fast. let go, it will slow to a stop fast. In a way, this is good, it gives you great control of the speed of the car. But you also have to add to it the effect of the mass of the chassis itself. Of course, that's not in the scope of the original post.
So back to the original question... A heavier rotating mass-drietrain would require more energy to pin at the same speed as a lighter rotating mass drivetrain. this means that the motor needs to either give out more energy in the same amount of time, or the same amount of energy for longer. I'm not 100% sure, but I think the real case event is a mixture of both, the motor is pushed harder, delivers a bit more power, and at the same time gets hotter, and it also takes a little longer to get up to speed.
If we were to stop the flow of current into the motor, then the drivetrain will slow down, but remember that the motor will cause drag onto the driveline (try and spin an unplugged motor by hand and you'll know what I mean). So, the motor's resistance has a bigger effect on the deceleration of the drivetrain than the mass does (unless we're talking about a very large mass).
With an electric engine, which is able to stop and start at will, a flywheel is not necessary, if you could have a zero-mass drivetrain, it would work fine. A gas/nitro engine, on the other hand, does need a flywheel of sorts to keep the crankshaft turning until the next power cycle.
In terms of the drivetrains of an RC car, lighter rotating mass will make it much more responsive in terms of acceleration and deceleration. this means that you press the trigger, the car will reach the required speed fast. let go, it will slow to a stop fast. In a way, this is good, it gives you great control of the speed of the car. But you also have to add to it the effect of the mass of the chassis itself. Of course, that's not in the scope of the original post.
So back to the original question... A heavier rotating mass-drietrain would require more energy to pin at the same speed as a lighter rotating mass drivetrain. this means that the motor needs to either give out more energy in the same amount of time, or the same amount of energy for longer. I'm not 100% sure, but I think the real case event is a mixture of both, the motor is pushed harder, delivers a bit more power, and at the same time gets hotter, and it also takes a little longer to get up to speed.
If we were to stop the flow of current into the motor, then the drivetrain will slow down, but remember that the motor will cause drag onto the driveline (try and spin an unplugged motor by hand and you'll know what I mean). So, the motor's resistance has a bigger effect on the deceleration of the drivetrain than the mass does (unless we're talking about a very large mass).
09-26-2003, 02:04 PM
#43
I yjink he means that it keeps the momentum up.
With an electric engine, which is able to stop and start at will, a flywheel is not necessary, if you could have a zero-mass drivetrain
Less rotating mass= less overall weight to get moving= faster car! as simple as that.
09-26-2003, 03:17 PM
#44
ok guys here it is from an ase certified tech.
for drag racing purposes especially the small bore engines drag racers install heavier flywheels to keep the engines rpm up between shifts and when launching to prevent stall which occurs in four cylinder engines and rotorys the inertia is needed for the lack of torque due to displacement.
for road racing they used lighter flywheels due to the constant change in rpms. plus the engines stay in the power band where the engine produces the most torque thats why the formula one cars rev so high to take off, so do the toyota atlantics.
i dont understand why you would add wieght to create a fly wheel effect on an electric cars especially all you have to do is trim up your throttle so when you let off power is applied to the motor as if you are heal toe driving in a real car . the car maintains momentum and doesnt unsettle when entering a corner .i use this especially when using a one way or running a 12.scale to keep up cornerspeed alot of guys that have made the a main used this method i used at the onraod nats and finished six in the 12 scale Amain and kevin mitchel finished 5 in the a main sedan stock class. this works extreemly whell on a stock motor which in turn is as if you were running a four cylinder engine and you dont want to bog it down, try it guys your lap times will drop i promise you. .
for drag racing purposes especially the small bore engines drag racers install heavier flywheels to keep the engines rpm up between shifts and when launching to prevent stall which occurs in four cylinder engines and rotorys the inertia is needed for the lack of torque due to displacement.
for road racing they used lighter flywheels due to the constant change in rpms. plus the engines stay in the power band where the engine produces the most torque thats why the formula one cars rev so high to take off, so do the toyota atlantics.
i dont understand why you would add wieght to create a fly wheel effect on an electric cars especially all you have to do is trim up your throttle so when you let off power is applied to the motor as if you are heal toe driving in a real car . the car maintains momentum and doesnt unsettle when entering a corner .i use this especially when using a one way or running a 12.scale to keep up cornerspeed alot of guys that have made the a main used this method i used at the onraod nats and finished six in the 12 scale Amain and kevin mitchel finished 5 in the a main sedan stock class. this works extreemly whell on a stock motor which in turn is as if you were running a four cylinder engine and you dont want to bog it down, try it guys your lap times will drop i promise you. .
09-26-2003, 05:19 PM
#45
Originally posted by PitCrew
yes, this is what I was reffering to. You can have higher compression because there is more energy stored in the flywheel to compress the air.
An electric motor has rotating mass, and it takes a considerable amount of energy just to stop the armature, especially at 30k RPM.
Less rotating mass= less overall weight to get moving= faster car! as simple as that.
yes, this is what I was reffering to. You can have higher compression because there is more energy stored in the flywheel to compress the air.
An electric motor has rotating mass, and it takes a considerable amount of energy just to stop the armature, especially at 30k RPM.
Less rotating mass= less overall weight to get moving= faster car! as simple as that.
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