Power/Speed relationship

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Avantone
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Tue Jun 19, 2012 9:02 am

I'm building new features into the gearbox visualiser, and part of that includes something on the relationship between max power and max achievable speed assuming average scooter and rider weight (obviously lights and mirrors is going to dent VMAX!).

I know what the mathematics should be, but was interested in real-world feedback.

So do these look realistic - feel free to offer up your personal experiences for power vs. vmax

thanks

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Tony

Download the (Original) Lambretta Gearbox Visualiser at http://www.avantone.wordpress.com

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Speed Demon
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Tue Jun 19, 2012 10:23 am

If you are talking full-frame PX or SX then those figures seem about right.

Above 60mph aerodynamics makes such a massive difference that a decent screen will give you around 3-5 mph and that throws your figures right out. Old 50cc 1960s GP bikes were doing 100mph on around 20hp which is half your figure but they had very low rolling and aero resistance

How about having 3 selectable curves so the user can say whether their aerodynamics are bad, average or good?
Get to SULK

warts
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Tue Jun 19, 2012 2:14 pm

50cc honda and sukuki GP bikes also had twin cylinders and up to 14 gears, and very light riders. Very boring to watch on a circuit like IOM.
Anyway, would it not be possible to interpolate the aeros if the power were known? Or work towards producing a correction factor.

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Avantone
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Tue Jun 19, 2012 5:17 pm

I was thinking of a workflow that starts with the max power (to establish a theoretical maximum speed). Once that's established, it's a case of choosing the right ratios based on the spread of power.

The graph is based on average rider/scooter weight and aero profile. Once that's established there's going to be differing lines for the extremes.

Setting #1 Lightweight scooter/rider, better aero, rider prone
Setting #2 Standard bodywork with normal riding position
Setting #3 With passenger/luggage, extra bodywork (scooter and rider!)



Yeah, need to think if I'm complicating this too much.
Tony

Download the (Original) Lambretta Gearbox Visualiser at http://www.avantone.wordpress.com

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Avantone
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Tue Jun 19, 2012 5:19 pm

warts wrote:up to 14 gears
There are people that think 5 speed boxes are the work of the devil, I wouldn't start mentioning 14! :D
Tony

Download the (Original) Lambretta Gearbox Visualiser at http://www.avantone.wordpress.com

rbgaz
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Tue Jun 19, 2012 6:14 pm

Avantone wrote:
warts wrote:up to 14 gears
There are people that think 5 speed boxes are the work of the devil, I wouldn't start mentioning 14! :D
hi-tony---anychance--u-could--get--the-ratios-for-rimmis-5speed--and-put-it-on-u-website---that-b-good- :)

gavi4t
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Tue Jun 19, 2012 9:51 pm

i would definatly agree that you would need 40 + hp to get a full legshielded scooter to go a 100 mph on the road and lots of torque too after 100mph u would probably take off in a backwards direction due to wind going under the floorboard area like a le mans car flipping after all a scooter is about as aerodynamic as an ice cream van , ive witnessed 100 mph and the the front end is very light even with a legshield toolbox petrol tank with 11 litres of fuel in it and a very heavy front end from an auto ,mind you it is fun accellarating up a long incline with 60 bhp lol

Darrell Taylor
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Tue Jun 19, 2012 10:26 pm

a few of the scoots ive tuned that are 35 to 38bhp are topping out at 85 to 88 mph gps with full bodywork ,the top sprint bikes full bodied are seeing from memory 92-94 mph and at scooter shotout last year i think about 85 was max seen on full body scoots
the cut downs and bsso scoots did 100mph or just over
whats interesting to find out is what lambrettas with engine transplants achieve and power output they have ? what does speed demons 6speed cr250 do? ive heard 95 97 gps ?
feel free to use this link to contact me on facebook and like it(if u like it)
https://www.facebook.com/pages/Taylor-T ... 8819767924

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Muttley McLadd
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Tue Jun 19, 2012 10:37 pm

Speed Demon wrote:How about having 3 selectable curves so the user can say whether their aerodynamics are bad, average or good?
heh heh.. Is that for the bike or the rider? :P
CakeAndArseParty

rbgaz
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Wed Jun 20, 2012 5:40 am

Darrell Taylor wrote:a few of the scoots ive tuned that are 35 to 38bhp are topping out at 85 to 88 mph gps with full bodywork ,the top sprint bikes full bodied are seeing from memory 92-94 mph and at scooter shotout last year i think about 85 was max seen on full body scoots
the cut downs and bsso scoots did 100mph or just over
whats interesting to find out is what lambrettas with engine transplants achieve and power output they have ? what does speed demons 6speed cr250 do? ive heard 95 97 gps ?
so--my-mates-are-telling-porkys---90mph--on--24bhp--scoots----lol

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