[nulldevice]

I was out riding recently when I came to a stop sign. It was at the foot of a steep-ish hill that I remember frequently blasting up on my 1960s 305cc Suzuki Raider. I could reach 70 MPH indicated at the top, so I blasted up the hill on my Burgman 400. It also reached 70 MPH at the top.

After finding some data and reducing it the Raider had 14.9 pounds per horsepower and the Burgman has 22.1 pounds per horsepower. With 1 1/2 times the weight per horsepower how is the Burgman 400 even close to the same performance? Top speed experiences show the same in the mid 90 MPH range too.

So, I speculate:
The horses they use to define horsepower got stronger over the decades and thus fewer horses needed for the same rate of work

They changed where they measure from the crankshaft or even calculate from the top of the piston to where the rubber meets the road or somewhere in between.

They had to have normal accessories load driven by the motor and running -- alternator, oil pump, water pump, cooling fan and such during the dino run at some date between the two machines manufacture.

I don't know. It is just weird. anyone have any ideas?

 

[inCaffeine]

To be honest, I don't really understand the non-metric system or in specific values.
But as I understood (tnx google), "pounds per horsepower" is a unit of the power-specific fuel consumption.
So that, your comparison is not quite correct.
Correct me if I'm wrong:
Suzuki Raider t305 = 28 [email protected] 7,500 rpm
Burgman 400 (for example 2007) = 23.4 kW @ 7600 rpm
That is, if compare just horsepower or kilowatts, everything is much simpler and more understandable.
More about comparisons.
1-cylinder four-stroke scooter vs two-stroke, twin-cylinder motorcycle?
6-speed multiplate wet clutch vs variator?
I hope you understand what I want to say...

 

[Bluebottle]

Speed is dependent on aerodynamic drag and tyre rolling resistance, so there is are at least two whole metrics missed out of your calculations for terminal speed.

Added to that changing gear can sap speed on a hill climb because the power is off during gear changes and ratios/change times decided by the rider may not be optimum. The automatic can have a significant advantage.

Aerodynamic drag on Burgmans isn’t great but it’s a much smoother form than most bikes.
Tyres are massively improved over 60’s tech and pressures have increased which both reduced rolling resistance

 

[inCaffeine]

IMHO, aerodynamics is not the most critical factor.
We can also pay attention to the size of the wheels (18 vs 13): this is physics: what will be the torque moment on the wheel...
And anyway, the comparison is not very correct: very different things both technically and technologically.

 

[mikeyMarine]

I'm old enough to remember WHY but not when the horsepower change measured at output shaft vs rubber on road happened, then it migrated to output shaft to propeller shaft in boating, etc. so indeed the horsies have evolved, the horsies may disappear with the newfangled 4 motor electrics to be replaced by torque numbers. tater totter mater motter. It all boils down to how fast you can git outta the Klub parkin lot when the Feds show up.

 

[dogboy]

I'm getting out of my league here, but maximum horsepower rating is measured at a specific RPM, and maximum torque, also at a specific RPM, is also important when generating acceleration times. The gearing inherent in the powertrain is going to determine when the machine is, or isn't, operating in the "power band" of the engine, and it isn't always going to be optimized for maximum horsepower utilization. Driveability, fuel economy and longevity play major factors in that engineering decision. My Toyota Tacoma generates maximum horsepower at 5,200 RPM, and I can assure you that the engine sounds like it's going to leap out from the hood at that engine speed. 🤣

 

[mikeyMarine]

This is why I suspect electric will just say max torque, direct drive to wheel and same torque thru all rpm ranges

 

[Bluebottle]

IMHO, aerodynamics is not the most critical factor.
We can also pay attention to the size of the wheels (18 vs 13): this is physics...

I have some experience of the physics, including a few years doing wind tunnel research, and a fair bit on tyre’s.

I remember incrementally changing increasing tyre sizes and getting roughly 5% reduction in acceleration going up in size by a similar proprtion.

However, that is with all other factors remaining the same.
It is different comparing 2 vehicles because the reduction gears are chosen by the manufacturer to balance the wheel size propertie.

 

[nulldevice]

To be honest, I don't really understand the non-metric system or in specific values.
But as I understood (tnx google), "pounds per horsepower" is a unit of the power-specific fuel consumption.
So that, your comparison is not quite correct.
Correct me if I'm wrong:
Suzuki Raider t305 = 28 [email protected] 7,500 rpm
Burgman 400 (for example 2007) = 23.4 kW @ 7600 rpm
That is, if compare just horsepower or kilowatts, everything is much simpler and more understandable.
More about comparisons.
1-cylinder four-stroke scooter vs two-stroke, twin-cylinder motorcycle?
6-speed multiplate wet clutch vs variator?
I hope you understand what I want to say...

Pounds per horsepower can also indicate the amount of weight (one is weighing the machine's gross loaded weight) each horsepower is hauling around.

Where you went wrong is you were thinking along the lines of measuring the weight of the fuel consumed per horsepower/kilowatt hour, one indication of performance. I calculated the gross weight of the machines and rider and then divided it by the horsepower, a different measure of performance.

 

[Bluebottle]

I calculated the gross weight of the machines and rider and then divided it by the horsepower, a different measure of performance

If it helps with any translation issue:
Nulldevice is describing the power to weight ratio.
The weight each horse (or each Kw) has to pull if you divide the weight up between them.

The more weight each horse (Kw) has to pull - the slower you would expect them to be

 

[Dave_J]

 

[Bluebottle]

But as I understood (tnx google), "pounds per horsepower" is a unit of the power-specific fuel consumption.

On a technical note after re-reading this:
The unit of power specific fuel consumption is time related so it would be per hour, either
g/(kW·h) = grams per Kw hour
or
lb/(hp·h). = pounds per horsepower-hour

Edit: The pounds or kilograms would also be fuel weight burned, not vehicle weight.

 

[inCaffeine]

I calculated the gross weight of the machines and rider and then divided it by the horsepower, a different measure of performance.

now it's clear.
anyway, the comparison does not become more correct from this: very different things both technically and technologically.
(see also what MikeyMarine and Bluebottle said about the size of the wheel, about changing the method of measuring horsepower, about gears... +chain rings.... and more, and more...)

and by the way, I think, it is quite possible, that on a short distance (starting from a traffic light), that T305 would have won against Burgman 400.

 

[B Getz]

Do you lose any HP with the belt drive? If so should it be somewhere in the calculation…. Somehow?

 

[SKreger]

Maybe a few years ago, the rider's weight in pounds (or kilos) the 1960s 305cc Suzuki Raider had to move up the hill, was less than nowadays... 😉

 

[PAP]

Since gross and net horsepower is measured at the "crankshaft"... everything from there back could make a major difference!

 

[Bluestrom13]

Raider = all TALK.
Burgman = all TORQUE.

 

[Bluestrom13]

Thanks Dave.
I was thinking that that one was wasted.