Fastest Speed by Scooter 70

[roost]

The most important thing is to reduce aerodynamic drag. The TP Lolu Dragster reached 159 Km/h average, over 1 mile track, launched start. The engine was 80cc. Tuned 2+ http://www.topperformances.com/html/record.htm
Seems not very fast to me.

The longer gear ratio of the scooter gears does not reduce the acceleration. Well, the clutch works a little more time with long gears, but it looses energy only until a certain speed. After that the acceleration is the same.

 

[Folkert@MinaRally]

.... but it looses energy only until a certain speed. After that the acceleration is the same.

Yeah it loses energy until it hits 100 km/h and then it flies towards the 140+.

Ok a little exaggeration maybe, but you get the point.

But it's a well-know fact that a little longer gearing won't suffer the acceleration, but if you're gonna install a very tall gearing....

And like you said, if you'd had like an extreme tall gearing, you would need to have a huge amount of clutch slipage to get off the line.

Like many race rep sportbikes. They get taller and taller 1st gears. And to get them off the line, you can't just quickly feed out the clutch, or it will just stall.

I can image a scooter having such a tall gearing (if that ratio would exist) that you would need so much clutch slipage, that the clutch would be worn out after 3 launches.

Also, it would not accelerate with "normal" gearing. Well seen your statement, it would mean that it "only" loses energy untill a certain speed, but I don't know. That would be such a high speed, before "normal" acceleration would kick in, that you're already at the place you were destend to go to.

Or maybe I'm missing something here?

 

[rydah]

those figures are not impossible.. but the thing is, how long does they take those 14+kp/h & 15+kp/h :?

Emo the hondas out here in hawaii are 120 to 125+cc stroker motors. 52.5mm cranks and 55 or 56cc pistons. these bikes are crazy powerfull and fast. they reach speeds fast. they wheelie very easy. the rush you get from riding these bike is unreal.

 

[emo]

Emo the hondas out here in hawaii are 120 to 125+cc stroker motors. 52.5mm cranks and 55 or 56cc pistons. these bikes are crazy powerfull and fast. they reach speeds fast. they wheelie very easy. the rush you get from riding these bike is unreal.

no wonder you could do that on those 125cc kits.. but on that TP dick, i dont think so..

 

[roost]

Yeah it loses energy until it hits 100 km/h and then it flies towards the 140+.

Ok a little exaggeration maybe, but you get the point.

But it's a well-know fact that a little longer gearing won't suffer the acceleration, but if you're gonna install a very tall gearing....

And like you said, if you'd had like an extreme tall gearing, you would need to have a huge amount of clutch slipage to get off the line.

Like many race rep sportbikes. They get taller and taller 1st gears. And to get them off the line, you can't just quickly feed out the clutch, or it will just stall.

I can image a scooter having such a tall gearing (if that ratio would exist) that you would need so much clutch slipage, that the clutch would be worn out after 3 launches.

Also, it would not accelerate with "normal" gearing. Well seen your statement, it would mean that it "only" loses energy untill a certain speed, but I don't know. That would be such a high speed, before "normal" acceleration would kick in, that you're already at the place you were destend to go to.

Or maybe I'm missing something here?

It ain't that bad. On stock gearing the clutch usually works until 5-10Km/h, with longer gears until around 20Km/h. Power on the rear wheel is lower until the clutch is slipping, because some of the torque of the engine is converted into heat, by the friction of the clutch.
But when the clutch has finished slipping, the acceleration of the bike has to remain identical with whatever final gears we use. Else it wouldn't apply to the law of the conservation of energy.

Overrange pulleys are installed to make the clutch work until a lower speed. Or to have longer final gear ratio with the same ammount of clutch slippage. It depends on the angle of view.

 

[Joël]

It ain't that bad. On stock gearing the clutch usually works until 5-10Km/h, with longer gears until around 20Km/h. Power on the rear wheel is lower until the clutch is slipping, because some of the torque of the engine is converted into heat, by the friction of the clutch.
But when the clutch has finished slipping, the acceleration of the bike has to remain identical with whatever final gears we use. Else it wouldn't apply to the law of the conservation of energy.

Overrange pulleys are installed to make the clutch work until a lower speed. Or to have longer final gear ratio with the same ammount of clutch slippage. It depends on the angle of view.

Almost true.
It's not only the clutch that counts. When the clutch is fully working (1:1 ratio with the clutch housing) the engine CAN BE still climbing in rpm's. If that's the case, you haven't got full power until the toppower rpm is reached.
I agree, the moment you reach the toppower rpm the acceleration is 100% the same as with a shorter final ratio.
The only thing that changes with a shorter ratio, is the speed where this full-power point will occur. The engine will give full power at a lower speed, and therefore, the acceleration from a standing start is improved.

If you have 2 scooters driving the same speed (say 60 km/h) with a different final gear ratio, and they both are running on their toppower rpm (say 14000 rpm) with a fully working clutch, the OVERALL gearing (between crankshaft and wheel) is the same.
It's the variomatic which compensates the shorter geared scooter.
That's why the variomatic of the short-geared scooter reaches earlier its maximum point, and therefore the topspeed is lower.

 

[roost]

In fact in reality it is much more complex than I described, my example was aproximative. The clutch in reality cannot (shouldn't) work at the rpm of maximum power.

The thing I wanted to expose is that when the variator is in operation, the acceleration is the same no matter the final gear ratio.

 

[Folkert@MinaRally]

...

The thing I wanted to expose is that when the variator is in operation, the acceleration is the same no matter the final gear ratio.

See, now that is the thing that make me wonder. Not saying you are wrong, but I'll give you my point of view (and you can tell me if I'm right or wrong)

See the variator part of the overal transmission, is the variable part and the gearing or final drive ratio is the fixed part of the transmission.

Now say you have 2 scooter with al the same stuff and same variable tranmission, only the final gearing is different.

How could the scooter with the taller gearing have the same acceleration? (and let's asume both have the same amount of friction/heat loses)

The scooter with the taller gearing but have slower acceleration OR (and this is what you might have been trying to tell all along) would the scooter with the taller adjust the clutch engaging point (higher rpm) to get it off the line as easy as the guy with the shorter gearing?
But then the that guy would also have more friction loss because his clutch is slipping more.

I think I'm still a bit confused.

 

[roost]

On the scooter with the short gearings, the clutch will work (slip) less time. This means that less energy of the engine will be consumed by the clutch.
(Example) If two scooters which are equally tuned except for the gearings would drag race;

Both scooters kick the gas same time.
The clutch begins to work and the scooters begin to accelerate. The first few meters they are side to side.
It's (example) 10km/h. On the scooter with the short gearings the clutch end it's work. At this point it's engine goes into the real powerband rpm, and the clutch does not consume any more power. While the scoot with the longer gears has the clutch still working. So the scooter with the short gears blasts some meters in front of the other scoot.
It's 20km/h, when the clutch of the other scoot finishes it's work, happens the same what happened to the scoot with the short gears.
Now on both scooters the variators are expanding the belt and regulating the transmission. On the scoot with the shorter gears, the variator expands faster, but both scoots mantain the same powerband rpm, and the torque transmitted to the rear wheel is the same. It has to be, by the law of the conservation of energy. This means that they accelerate the same. However the second scoot is some meters back.

Lets say at 100Km/h the variator of the short gear scoot comes to the end of it's range. Because of this the overal transmission ratio becomes fixed, this means that to gain speed it should increase the revs. So it usually does, but this way the engine goes overrev, where it looses power, so the scoot stops accelerating.
While on the scoot with the long gears the vario is still working to mantain the engine at it's max power.
If the scoot stops gaining speed and the engine isn't in overrev, it means that all the power possible is used to fight the aerodinamyc and rolling drag force. On a perfectly tuned scoot this would happen just before the variator has ended it's range.

Of course there are some other things that are and may happen during the work of the transmission system, but it's the work of a good tuner that has to take out much performance possible from the engine by setting it up properly.
So the setup and quality of the clutch on an long gear scoot engine is much more important.
I hope I was understandable

 

[Folkert@MinaRally]

On the scooter with the short gearings, the clutch will work (slip) less time. This means that less energy of the engine will be consumed by the clutch.
(Example) If two scooters which are equally tuned except for the gearings would drag race;

Both scooters kick the gas same time.
The clutch begins to work and the scooters begin to accelerate. The first few meters they are side to side.
It's (example) 10km/h. On the scooter with the short gearings the clutch end it's work. At this point it's engine goes into the real powerband rpm, and the clutch does not consume any more power. While the scoot with the longer gears has the clutch still working. So the scooter with the short gears blasts some meters in front of the other scoot.
It's 20km/h, when the clutch of the other scoot finishes it's work, happens the same what happened to the scoot with the short gears.
Now on both scooters the variators are expanding the belt and regulating the transmission. On the scoot with the shorter gears, the variator expands faster, but both scoots mantain the same powerband rpm, and the torque transmitted to the rear wheel is the same. It has to be, by the law of the conservation of energy. This means that they accelerate the same. However the second scoot is some meters back.

Lets say at 100Km/h the variator of the short gear scoot comes to the end of it's range. Because of this the overal transmission ratio becomes fixed, this means that to gain speed it should increase the revs. So it usually does, but this way the engine goes overrev, where it looses power, so the scoot stops accelerating.
While on the scoot with the long gears the vario is still working to mantain the engine at it's max power.
If the scoot stops gaining speed and the engine isn't in overrev, it means that all the power possible is used to fight the aerodinamyc and rolling drag force. On a perfectly tuned scoot this would happen just before the variator has ended it's range.

Of course there are some other things that are and may happen during the work of the transmission system, but it's the work of a good tuner that has to take out much performance possible from the engine by setting it up properly.
So the setup and quality of the clutch on an long gear scoot engine is much more important.
I hope I was understandable

Yes your english is fine.
But now I have another question.

In your example you have the scooter with the short gearing getting into overrev and the scooter with the long(er) gearing stays in its powerband.

First, even if it wouldn't overrev, but was also kept in its powerband, it would at some speed still stop acceleration when a certain aerodynamic drag "value" is reached.

But what if the scooter with the taller gearing would also hit overrev? It would stop accelerating too.

All good, but if both scooters are in powerband, with a fully engaged clutch and they would both stay there, the variator on the scooter with the short gearing has to drive a shorter final gear ratio (the fixed gearing) while the longer gear scooter's variator has to drive a heavier gearing. So the scooter with the shorter gearing has a greater "turning moment" which =torque.

Sure the acceleration STOPS earlier than the taller geared scooter......(right?)


Ok let's step away from scooters for one moment now and talk about motorbikes. Yeah I know, these have gearbox....but....
The gears are variable gear ratio's (so like the scooters variator, only not stepless), and a motorbike also has a fixed final drive ratio: the small front sprocket and the taller rear(wheel) sprocket.

Now how many times have I seen and read, that people either increase the rear sprocket by a couple of teeth, decrease the amount of teeth on the front sprocket, or with very overgeared bikes, to both.

Now the reason they do this is -yes you guessed it right- is to trade in top speed (who need a 180mph top speed) for more acceleration. Yes the acceleration stops earlier. What used to be the top speed in 5th, now has become their 6th gear. Since the ratio is shorter, the thrust/drag balance each other out earlier, but acceleration has increased.

 

[roost]

In your example you have the scooter with the short gearing getting into overrev and the scooter with the long(er) gearing stays in its powerband.

First, even if it wouldn't overrev, but was also kept in its powerband, it would at some speed still stop acceleration when a certain aerodynamic drag "value" is reached.

But what if the scooter with the taller gearing would also hit overrev? It would stop accelerating too.

The scooter stops accelerating when the power of the aerodynamic braking and terrain rolling equals the power of the engine on the rear wheel. If the engine goes overrev il looses power. So less power will be availible to fight the aerodynamic braking and terrain rolling = lower speed.

All good, but if both scooters are in powerband, with a fully engaged clutch and they would both stay there, the variator on the scooter with the short gearing has to drive a shorter final gear ratio (the fixed gearing) while the longer gear scooter's variator has to drive a heavier gearing. So the scooter with the shorter gearing has a greater "turning moment" which =torque.

Yes, that is why the variator is there; to compensate the differences in torque of longer/shorter gears. At the wheel the torque remains the same.

Ok let's step away from scooters for one moment now and talk about motorbikes. Yeah I know, these have gearbox....but.... okay the gears are variable gear ratio's, but a motorbike also has a fixed final drive ratio, the small front sprocket and the taller rear(wheel) sprocket.

Now how many times I've seen, that people either increase the rear sprocket by a couple of teeth, decrease the amount of teeth on the front sprocket, or with very overgeared bikes, to both.

Now when they do this, yes you guessed it, they trade Top Speed for acceleration. (and often, what used to be the bike's 5th gear, now is its 6th)

They havent gained as much as they feel. Whith shorter gearings more energy is used over the same ammount of road, so it accelerated better. The engine was more time at full power.

 

[Gurra]

A guy here in sweden got 143 km/h on the bench (is it called that?) with his carbon aerox.

He didnt have NOS at the time, but he is installing it till the 2005 season

 

[Joël]

Yes, that is why the variator is there; to compensate the differences in torque of longer/shorter gears. At the wheel the torque remains the same.

True.

Folkert, what you must understand is when two scooters drive the same speed, and has the same engine rpm, the overall gearing must be the same!!

Same gearing -> same wheel torque -> same acceleration force -> same acceleration!!

 

[Folkert@MinaRally]

True.

Folkert, what you must understand is when two scooters drive the same speed, and has the same engine rpm, the overall gearing must be the same!!

Same gearing -> same wheel torque -> same acceleration force -> same acceleration!!

Joël, I understand that 2 scooters with same engine RPM and speed have to have identical gearing.

But then I say: then these scooter have same acceleration and speed, because they have the same gearing (the actual sprockets), same rear wheel diamter etc (since wheel diamter also is a factor)

But 2 scooter can also have different speeds at same engine RPM, which means that the overall gearing is not the same and thus, acceleration is also different.

So while you are 100% correct, it's just one situation you describing.

If we took the 2 scooters in your example and let's say both have a 13" rear wheel, with same tire around it.

Now if we gave one of these scooters a 10" rear wheel, they will still rev the same (assuming that in all examples, the engines have the same power output at any given RPM) the 10" scooter will have a faster acceleration than the 13"
However the 10" will have a slower top speed when both reach maxium rpm/same overrev.
And they had the same overall gearing, and with exact same variator assambly, the final drive ratio (the sprockets) would be the same too.

In this case, the wheels could also be seen as the final, final drive ration.

The larger wheel diamter will give more top speed (since it covers more distance per revolution), but the smaller wheel will have a quicker acceleration (but it wil stop acceleration faster, than the larger wheel)

Again, I'm not saying anyone's right or wrong, just trying to "solve" this.

Maybe we all have a different definition of the acceleration we are discussing here?
And maybe you mean with same acceleration, that well they both accelerate the same, but with larger gearing it is spread over a longer time as opposed to the one with the smaller gearing.

Just in case I wasn't clear, but I just mean the simple: who accelerates the fastest to any given speed. (of course in the end the higher geared scooter will pass the lower geared scooter)

Now when I think about the other "definition", that on the longer geared scooter, it's accleration kicks in later, or better yet, is spread over a wider speed range, while actually being the same(!) but on the shorter geared scooter, that same amount is put in a smaller range, so it stops acceleration sooner (and thus a lower speed) but it still has to faster off the line, so looking from that perspective, it accelerated faster over a certain distance. Untill it's shorter gearing is at its limit and the longer geared bike passes it.

 

[Aerox-Evo70]

A guy here in sweden got 143 km/h on the bench (is it called that?) with his carbon aerox.

He didnt have NOS at the time, but he is installing it till the 2005 season

on the bench 143 isnt very fast (depending on the gearing)
even i scored 170 with only 17hp max (14hp @ 165) with a ratio of 10 and 13" weel...

but above the 100 kmph the wind drag gets really strong.

 

[roost]

Now if we gave one of these scooters a 10" rear wheel, they will still rev the same (assuming that in all examples, the engines have the same power output at any given RPM) the 10" scooter will have a faster acceleration than the 13"
However the 10" will have a slower top speed when both reach maxium rpm/same overrev.
And they had the same overall gearing, and with exact same variator assambly, the final drive ratio (the sprockets) would be the same too.

In this case, the wheels could also be seen as the final, final drive ration.

The larger wheel diamter will give more top speed (since it covers more distance per revolution), but the smaller wheel will have a quicker acceleration (but it wil stop acceleration faster, than the larger wheel)

Again, I'm not saying anyone's right or wrong, just trying to "solve" this.

This is the same situation as on scooters with different final gear ratios. The wheel is a gear.
In your case will happen the same as I described; the 10" wheel scoot will pull away in the first meters of the race, then they will accelerate equally. Unless there is a difference in weight. And lets forget about the different wheel inertia.

Maybe we all have a different definition of the acceleration we are discussing here?
And maybe you mean with same acceleration, that well they both accelerate the same, but with larger gearing it is spread over a longer time as opposed to the one with the smaller gearing.

The acceleration of which I'm talking to is lets say; who takes less time on a distance of 100,200,400m...
With larger gearing it is not spread over a longer time! But a longer geared scooter will have more "gears" reserve.

 

[Folkert@MinaRally]

....

The acceleration of which I'm talking to is lets say; who takes less time on a distance of 100,200,400m...
With larger gearing it is not spread over a longer time! But a longer geared scooter will have more "gears" reserve.

With that said Roost, the shorter geared scooter will be the quickest to reach the 100, 200 and 400 meter (or as long as it hasn't reached topspeed/the longer gearing of the other scooter hasn't kicked in) and thus has the quickest acceleration.

 

[Folkert@MinaRally]

on the bench 143 isnt very fast (depending on the gearing)
even i scored 170 with only 17hp max (14hp @ 165) with a ratio of 10 and 13" weel...

but above the 100 kmph the wind drag gets really strong.

You say you reached 170 km/h with a 13" AND 10" wheel?

So what you did you do? You changed real wheel on you scooter in between dyno runs?

I have a feeling you're saying something that doesn't make any sense, but I can't tell for sure.

And wow, 170 km/h is REALLY fast, even on a dyno. That scooter bust have had the tallest gearing ever.

 

[Henk_de_mol]

No, on the dyno it isnt necessary to have a very tall gearing.. Just keep the throttle open

 

[roost]

With that said Roost, the shorter geared scooter will be the quickest to reach the 100, 200 and 400 meter (or as long as it hasn't reached topspeed/the longer gearing of the other scooter hasn't kicked in) and thus has the quickest acceleration.

You just dont understand
Yes, the shorter geared scoot will pass first the end line. Because of the meter or two the scooter has gained during the start (the clutch thing, remember?).
But it will be ahead of the long geared scoot, at the end line, by just the meter or two that has gained during the start.


On a dinamometer with an inertia flywheel, top speed can't be measured. Well, it measures the maximum possible speed of the rear wheel to the given engine transmission setup and rpm. But such data is useless.