Top Speed

The top speed of the Address is around 64mph on the clock or around 60mph gps.

I say “around” as it is very dependent on slope and wind speed – but on the flat and with no wind I can manage 60mph.

Calculations show that at the maximum power at 8000 engine rpm corresponds to 60.5mph, so that fits.

At this speed, virtually all of the resistance is wind resistance.  Rolling resistance can be ignored in a first approximation.
Now wind resistance is proportional the speed to the power of three. Why? the kinetic energy of the air is given by the formula E = mv2/2 but the amount of air we meet is proportional to the speed, or v. So we can use a formula:-

power = kv3
k = bhp/(mph)3

The units of k are not important, but in this case it will be

bhp hrs3/miles 3

It is to do with the wind resistance of the bike and rider.  For the Address, if bhp = 9.4 and max mph = 60, then k = 9/60/60/60 = 0.0000435.

On my old Royal Enfield Bullet with around 22bhp managed around 76mph so k works out as 0.0000501. 

The BMW has around 50bhp and reaches 100mph so k works out about 0.0000500

Both motorcycles are “naked” so wind resistance will be higher than a scooter.

So can my Address go faster?
Yes of course, if I am heading downhill, or with a tailwind. BUT the engine rpm will go up of course. If I push the bike up to 75mph then in will be spinning at 10,000 rpm. So a 15mph tailwind would do it, right?  Wrong – the power is dropping off above 8000 rpm. I won’t have 9.4bhp. If the power at 10,000rpm has dropped to 7bhp, then I can only manage about 54mph in still air – so I’d need a 21mph tail wind to reach 75mph.  I’m not sure what the effect on the engine would be though.

Other scooters
Now, I’ve been looking at a Honda SH300i and I have been trying to find the top speed.  I’ve seen figures from 70 to 95mph! Using the same k as my Address, and the official Honda BHP of 24.8, top speed would be 83mph. That would probably show as 87mph on the speedo.  This seems about right to me.  It will be about the same for any 25bhp scooter such as the Vespa 300GT.

The effect of a passenger and hills.
On the flat, the overall weight of the bike, rider, and passenger has very little effect.  It’s a different story on a hill.  My wee Address zooming along at 60mph with my wife on the back will slow down to 50mph on a 5% slope.  24.8bhp would be able to go up at 75mph

Headwinds and tailwinds and rain
As mentioned above, a tailwind will give a faster maximum speed but due to the engine moving away from its maximum power point it is not a 1 for 1 relationship.
A headwind though is a 1 for 1 relationship at higher speeds. A 10mph headwind will drop my maximum speed by 10mph to 50mph.
CVT helps is these conditions. Years ago I use to commute to work an a Honda H100. In still wind I could get it showing 57mph on the clock, in fifth gear. With a tail wind (or tailgating a lorry – I look back in horror) I could reach around 62.
But a headwind would slow it down and push it out of the power band, so I had to drop to fourth gear. The bike would speed up, but then it would become rev-limited.  I simply could not get maximum power on the road at 50mph, so it was a continual gear change up and down. With a strong head wind and an incline I was sometimes switching between third and fourth gear under 40mph.
Rain has an effect too. Simply put, water is heavier than air.  It’s a bit like riding into someone squirting a hose at you.

I did consider doing the SS1000 soon after I got the Address, but I think the fact that my average speed could be drastically effected by wind and rain has put me off the idea.  It would become a matter of chance rather than riding skill and endurance.  Also I’d have to have the poor Address flat out all of the time to maintain the average speed.  Yes it could be done, but luck would play too great a part for me – and a bigger bike (like my 650cc 50bhp BMW) is not really a challenge – more of a chore.

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