My Excel Spreadsheet for Motorcycle Performance estimation.
This spreadsheet will predict the likely performance of a
motorbike when the user inputs certain information.
The output is a list of Average Tractive Force in each
gear,Peak Drag force (due to air resistance) in each gear,
rate of acceleration through each gear, time spent in each
gear, cumulative time, distance travelled
in each gear, cumulative distance, speed reached in each gear
and also an estimation of the likely maximum speed of the bike.
The cells with a yellow background are the results of
calculations made by the spreadsheet, the grey cells
are for user data input.
Starting in the "Data Entry" area the user enters either
the power/rpm and peak torque/rpm
as quoted by the manufacturer (in BHP and ft.lb) or the
same info from actual measurements at the back wheel.
I've used a sweeping assumption that manufacturers figures for
power/torque are crankshaft values and
an estimate for actual back wheel values will be about
10% less.
Next you enter the gear ratios and the speed expected to be
reached in each gear.
The gear ratios are the total gearing between crank and rear
wheel so you must take into account
the gearbox transfer ratios and the final drive ratio
(rear sprocket/geabox sprocket). The spread sheet calculates
the engine RPM at the given speed for each gear - you can use
this to check you've got the correct ratios
and wheel diameter by comparing the calculated RPM from what
you actually see on the bike.
The final area in the Data Input section takes in info about
Weight, rear wheel radius and the
magic number of Cd.A
Cd is the coefficient of drag and A is the
frontal area. The product Cd.A varies
from about 0.24 for a sports bike
to 0.35 for a Pan European (approx!).
Rear wheel diameter along with gearing determines the revs at a
certain speed and will have a bearing
on the acceleration figures.
Download the Self Extracting Zip
file of the spreadsheet(51k)
Download the Zipped Excel
Spreadsheet (15k)
[Back to Bike info]
[Next]