LC8 - How fast?

[Uiltjie]

OK guys, don't get upset, this fun remember?

So, I spoke to my clever swaerie in Pretoorsdorp, who is a civil engineer BTW.

It takes energy to move mass, end of story.  Not acceleration, just maintaining speed, be it top speed or any speed.  You need energy for that.  The more the mass, the more the energy.

2 simple examples:

1.  A Bugatti Veyron has a 750Kw engine to move its 2.5t body to a topspeed of 400km/h.  If it weighed 500kg, the motor needed would have been say 300Kw.
2.  If you take a Citi golf, powered by a VW 1600 motor, driving at say 100km/h, takes X amount of energy. If you build the same car from styrofoam, same shape, same drag, and you power it with a Yammie XT500 motor, and travel next to the real golf, and you could quickly swap the engines, do you think the XT motor will maintain the speed on the real Citi Golf?

Does this simple arguement make sense?

yes, the argument makes sense however it is incorrect ... the air resistance of the vehicle in question either the golf or the bugatti is the limiting factor not the weight thereof.   

again your swaar is bringing in too many variables , we are not comparing a xt500 motor with a citigolf motor , we are comapung a citigolf motor with a citigolf motor, we are comparing a citigolf weighing 1 ton with a citigolf weighting fora rguments sake 2 tons ...in this scenario the top speed owuld be the same , the time taken to reach top speed would be vastly different ..the negligible topspeed owuld be due to additonal friction caused by the wheels an bearings but it would be tiny

Those were my own stupid examples....

OK, not pushing this too far (I hope we can get a proper physics professor here with a formula ) take the same Citi Golf, load one with a 50kg driver, hit a saltpan for as far as you want to go, as long as you want - take top speed.  Now, take the same car, load 5 pax and 20 cases of beer, hit the same saltpan.  Will the topspeed be the same?

I still don't think so....it takes energy to move mass.  The more the mass the more energy needed, therefore the laden CitiGolf would have used all its energy to move the mass, and will have no more the reach the topspeed of the light one....that makes sense, doesn't it?  There is no such thing as perpetual power....

[Uiltjie]

I'm going to send this one to Mythbusters!

[LuckyStriker]

I'm going to send this one to Mythbusters!

great idea

[IceCreamMan]

OK guys, don't get upset, this fun remember?

So, I spoke to my clever swaerie in Pretoorsdorp, who is a civil engineer BTW.

It takes energy to move mass, end of story.  Not acceleration, just maintaining speed, be it top speed or any speed.  You need energy for that.  The more the mass, the more the energy.

2 simple examples:

1.  A Bugatti Veyron has a 750Kw engine to move its 2.5t body to a topspeed of 400km/h.  If it weighed 500kg, the motor needed would have been say 300Kw.
2.  If you take a Citi golf, powered by a VW 1600 motor, driving at say 100km/h, takes X amount of energy. If you build the same car from styrofoam, same shape, same drag, and you power it with a Yammie XT500 motor, and travel next to the real golf, and you could quickly swap the engines, do you think the XT motor will maintain the speed on the real Citi Golf?

Does this simple arguement make sense?

yes, the argument makes sense however it is incorrect ... the air resistance of the vehicle in question either the golf or the bugatti is the limiting factor not the weight thereof.   

again your swaar is bringing in too many variables , we are not comparing a xt500 motor with a citigolf motor , we are comapung a citigolf motor with a citigolf motor, we are comparing a citigolf weighing 1 ton with a citigolf weighting fora rguments sake 2 tons ...in this scenario the top speed owuld be the same , the time taken to reach top speed would be vastly different ..the negligible topspeed owuld be due to additonal friction caused by the wheels an bearings but it would be tiny

Those were my own stupid examples....

OK, not pushing this too far (I hope we can get a proper physics professor here with a formula ) take the same Citi Golf, load one with a 50kg driver, hit a saltpan for as far as you want to go, as long as you want - take top speed.  Now, take the same car, load 5 pax and 20 cases of beer, hit the same saltpan.  Will the topspeed be the same?

I still don't think so....it takes energy to move mass.  The more the mass the more energy needed, therefore the laden CitiGolf would have used all its energy to move the mass, and will have no more the reach the topspeed of the light one....that makes sense, doesn't it?  There is no such thing as perpetual power....

top speed will be the same minus a small amount due to friction of the wheels which is encreased due to weight , rolling reistance ...  

check how much energy is needed at top speed for any vehicle ...  

[LostDOG]

In 1988 I was a pillion of a friends CB750F. Plakkies, T-shirt, shorts and helmet that was way too big. Near Witrivier he did some crazy speed. I dont know what the clock speed was. This story has no real meaning except I know that was the fastest I've been on a bike, and I wanted to be included in this thread. And I didnt spill either of our dops.

[Uiltjie]

Guys, I have to move some mass now

Will still think about it this pm, while I put in some work!

Cheers!

Ps, Please do carry on, would like to see the formula....

[Butch]

Guys, I have to move some mass now

What a coincidence, I also need to take a shit.

By the way, I prefer being called lean or small boned, rather than skinny.

[IceCreamMan]

back to topspeed

on a bark would be on my gsxr750 ,clocked at 285km/h ...true speed prolly around 260 i owuld imagine

on my strom , clock speed 230 (restricted to that) true speed as measured by mr garmin is 212km/h ...

i rearely go over 200 these days except on dirt 

[JourneyMan]

165.

On the clock, not GPS. 

[shark_za]

What ICM says is true, speed has no relation to power apart from acceleration and momentum.
Don't think of this on the road, rather in space. You apply power to a mass, it accelerates till the resistance factors equal the power and it stays at the same speed. Both the heavy and lighter thing will do this. In space, if the resistance stays zero the things will continue to accelerate, probably to the speed of light.

The real world difference is due to factors like gravity.

Power has a time factor in it, so while a heavier car may have more momentum at the same top speed it took longer to get there and therefore the energy is the same.

[Paulsky]

the best i've ever seen is 221 on the speedo on my 950, doubt it was much more than 200 or so genuine, speedo's are very optimistic. Gonna give it a run this weekend with the GPS and see what it will pull. it ran an actual 229 on the dyno. That is without wind resistance though. PS. am running a 16 front sprocket.

[serf]

190 on the speedo - the bike was willing but I ckickened out.

Want to add my bit on the acceleration / top speed argument - I drive a diesel bakkie with a top speed of about 140km/hour. Load 750 kg's and I will never reach that speed, doesn't matter how hard I try. So in my opinion wheight does play a roll  - (sorry, but I am an auditor and not an engineer) - just my 2c.

[peter stuyvesant]

Clocked 206 (GPS speed) on my 950 and I think it was on the way to the "bash" with side panniers and luggage
Just managed 200, 2 up (clock speed).
Either way, plenty fast on a d/s bike.

[Operator]

I did 220 on my KTM once...

Butch was that on tar ......or gravel ?   

[Basset]

I am not an engineer. (As ek klaar aan 'n bike gewerk het sit ek nie die spanner op die engine neer nie )
I also fly RC aeroplanes and I know for a fact that when you put a bigger engine in the same aeroplane you achieve a much higher top speed. We measure it with radar.
So I am under the impression that yes, if you want to move a body at higher velocity you need more power.
 
My one aeroplane needed more weight in the nose, so no change in engine or body just more weight and my speed came down with a substantial margin.
WTF 

[topbox]

OK guys, don't get upset, this fun remember?

So, I spoke to my clever swaerie in Pretoorsdorp, who is a civil engineer BTW.

It takes energy to move mass, end of story.  Not acceleration, just maintaining speed, be it top speed or any speed.  You need energy for that.  The more the mass, the more the energy.

2 simple examples:

1.  A Bugatti Veyron has a 750Kw engine to move its 2.5t body to a topspeed of 400km/h.  If it weighed 500kg, the motor needed would have been say 300Kw.
2.  If you take a Citi golf, powered by a VW 1600 motor, driving at say 100km/h, takes X amount of energy. If you build the same car from styrofoam, same shape, same drag, and you power it with a Yammie XT500 motor, and travel next to the real golf, and you could quickly swap the engines, do you think the XT motor will maintain the speed on the real Citi Golf?

Does this simple arguement make sense?

probably cause it to accelerate

[LostDOG]

I am not an engineer. (As ek klaar aan 'n bike gewerk het sit ek nie die spanner op die engine neer nie )
I also fly RC aeroplanes and I know for a fact that when you put a bigger engine in the same aeroplane you achieve a much higher top speed. We measure it with radar.
So I am under the impression that yes, if you want to move a body at higher velocity you need more power.
 
My one aeroplane needed more weight in the nose, so no change in engine or body just more weight and my speed came down with a substantial margin.
WTF 

OK Basset, this is another different scenario. Wings provide lift. Lift force is dependent on air velocity over said wing. Thus more weight means you need more speed to lift it. Now, if you dont have more engine power available you start trimming all parts of the wing to change the lift characteristics, thus changing drag, thus slower speed. Eeish.. we could go on forever and a day with various scenarios. How fast was your plane?

[Meerkat]

Now, take the same car, load 5 pax and 20 cases of beer, hit the same saltpan.  Will the topspeed be the same?

You would never reach the same top speed as the first car, as you would need to stop every coupla minutes for p-stops for the beer drinkers. 

 

[LostDOG]

Now, take the same car, load 5 pax and 20 cases of beer, hit the same saltpan.  Will the topspeed be the same?

You would never reach the same top speed as the first car, as you would need to stop every coupla minutes for p-stops for the beer drinkers. 

 

     Reminds me of "Cheech and Chong - Up in Smoke" Hey dude are we moving yet?

[Uiltjie]

Now, take the same car, load 5 pax and 20 cases of beer, hit the same saltpan.  Will the topspeed be the same?

You would never reach the same top speed as the first car, as you would need to stop every coupla minutes for p-stops for the beer drinkers. 

 

     Reminds me of "Cheech and Chong - Up in Smoke" Hey dude are we moving yet?

Excellent movie!