Honda Spree and Elite 50 Forums

9:1 gear goes little over 70mph, dd50 not port motor/ not port contesta bore,pg long, keli pulley/ramp. ct/28mm oko and pg long &1500 springs ... near sea level tuning that is 10in wheels tunes roller about 42-45 grams- 110lb rider.


Dont buy 9:8gear , just 9:1 gear are good on steep hill and flat road!

Greetings:

The clutch is splined onto the front transmission shaft. There is no "clutch drive ratio". My NB50 Service Manual indicates the Variator can vary the engine/front shaft ratio by a factor of 2.4:1 at its low-speed position to 0.8:1 at its high-speed position.

That and the gearing determine a relationship between engine RPM and rear axle RPM. The relationship is fixed once the variator sheaves are fully compressed.

RPM(e)/0.8 = RPM(d) Where "e" and "d" refer to Engine and front Drive shaft.

After that it becomes a question of determining the speed of the Axle:

RPM(d)/9(for 9:1 gears) = RPM(a) Plug in 12.4 or 7.833 or whatever your gearing is.

The Axle speed is multiplied by about 50 inches per revolution, based on a 16" wheel-tire diameter.

So once you know axle RPM, you can determine theoretical groundspeed per minute in any units you like.

I performed the calculations of my previous post in my head, so there are probably errors, but the gist is that it would take lower gearing or a phenomenally high-revving engine to get to 70, let alone 100. Factor in imperfect belt contact, tire slippage and the inherently bad aerodynamics of any open * vehicle and it seems unlikely that an air-cooled scooter can run at the Ton for long, except in the vivid imaginations of their owners. See Power, Traction, and Aerodynamics.

Wheelman-111 wrote:Greetings:


RPM(e)/0.8 = RPM(d) Where "e" and "d" refer to Engine and front Drive shaft.

After that it becomes a question of determining the speed of the Axle:

RPM(d)/9(for 9:1 gears) = RPM(a) Plug in 12.4 or 7.833 or whatever your gearing is..

so really its rpmE/.8/.9=rpmA

What i'm confused about is this, the manual says the front shaft ratio factor is between 2.4 and .8, isn't that the ratio of the front pulley to the rear pulley.

At low speed the belt is riding on the inside of the variator (small diameter) and riding high up on the clutch side pulley (large diameter).

At higher engine speed the rollers move away from the center of the variator causing them to push against the variator backing plate, pushing the variator forward causing the belt to ride up high on the front pulley (large diameter) and at the same time, the spring in the back is compressed causing the clutch side pulley to move out allowing the belt to ride low on that pulley (small diameter).

So the 2.4 would be small diameter front, large diameter rear, and .8 would be large diameter front and small diameter rear?

here are the basic to find out gear ratio.


primary gears count the bigger tooth and small tooth from that, then you divide by.

same step like primary gears. This is scecondary gears , count it.

primary ratio# time by secondary ratio equal to final drive ratio.

Nevermind, found it here.
http://auto.howstuffworks.com/cvt2.htm

The drive ratio is the ratio of the drive pitch radius to the driven pitch radius.