Motorcycle Control Panel with Arduino + Bluetooth

Forum 2005-2010 (read only) General Exhibition
71

Posted by: tz
Force = mass * acceleration, and apparently you have acceleration and know the mass of you on your bike.

Torque is force * distance (normal, i.e at a right angle), so if you know the diameter of the rear tire you know the torque there from the force. Then you have to go back through the gearing ratios (the drive chain, transmission, etc.) and determine if you want to account for friction.

Work is force * distance (in the same direction as the force), which is also calculable from the acceleration. Power (watts/horsepower) is work per second, i.e around 750 foot-pounds per second.

A lot of it is basic physics, but more of it is just getting the units to cancel out.

Here's what I've tried:
1)made a curve on spdsheet. seconds as X axis, mph as Y axis, curve then = mph/secs, changed mph to feet/secs so curve shows ft/sec/sec or ft/sec^2, am I right so far? (ft/sec^2 is acceleration), right ? or wrong?

2)wt of bike+me = approx 700lb, mass = wt(lbs)/32.18ft/sec^2 (force of gravity in ft/sec^2)= 700/32.18 = 21.75lb-sec^2/ft

3)force = mass*accel = 21.75b-sec^2/ft *(say) 30 ft/sec^2 this will = 652.5 lb of force

4)torque = force * radius of turned wheel, wheel = 2ft in diam, radius =1ft, therefore: torque= force of 652.5lb * 1ft = 652.5ft-lb on the driving wheel, right? wrong? at time when accel=30ft/sec^2 ???

  1. find rpm, rpm=ft/sec^2 @1-sec =ft/sec (say)30ft/sec^2 @1sec = 30ft/sec, *60 =1800ft/min, diam of wheel =6.33ft, then rpm=1800ft/min/6.33ft/rev= 284.4 rpm for dr. wheel

6)hp=torquerpm/5252 = 652.5ft-lb284.4pm/5252 = 35HP at the dr. wheel when bike is being accel at 30ft/sec^2

  1. however, following this chain of calculations up the curve, I end up with ridiculously high HP, almost 400hp,(at the dr. wheel) not on my harley sportster. :o
    Further calcs. for engine hp gives a high hp of 109 hp from the engine which is doubtful. :-/

I found the derivatives of the original curve, which give instantaneous change in accel, using that, I end up with extremely low hp. :-[

Any advice would be appreciated, but I know this is off subject. :slight_smile:

PO'T