Board-track power: less than you probably thought

[DougC]

I originally posted this to another forum, but it might be worth repeating here.

This page has a story on a barn-find 1909 Curtiss:

http://thevintagent.blogspot.com/2009/05/barn-find-1909-curtiss.html

link text--- http://thevintagent.blogspot.com/2009/05/barn-find-1909-curtiss.html

Early on in the text he notes-

"... quite a nice machine in the day with a reliable and powerful inlet-over-exhaust v-twin of 1000cc..."

Beneath the second photo, a couple of figures are given-

" ... The Curtiss weighed all of 160lbs, and was good for around 60mph ..."

Further on it is said-

"... By 1904, a racing motorcycle of 5hp began to make the rounds of competitions, and winning, and he journeyed to Daytona that year to participate in the open speed trials on Ormond/Daytona beach, breaking all the 2- to 10-mile records in the process, averaging 67.41mph for the 10-mile record. ..."

--------

So from this we can gather a few things:

For a v-twin motorcycle of the 1905-1910 era...
...weight would be ~160 lbs
...top speed would be around 65 mph

Most surprising to me is these two figures-
...v-twin engine would be ~1000cc's
...that engine would only make about 5 hp (!)

By comparison, the 2010 Yamaha YZF-R1 has a 998cc 4-cyl engine that makes about 146 HP.
If you wanted to compare another modern v-twin engine, then the 2011 Harley-Davidson models with a relatively crude 883cc motor makes "only" about 55 HP. Ten times as much.

A modern 5.5 HP lawn tractor engine is a pretty low-performance motor, yet displaces only around 150cc's.



We see a lot of people who wish they could find an engine that would look more authentic than the China bike engines--but the biggest problem you would seem to have would be to keep a modern engine from making too much power....

The last of the board-track racers--that were hitting 100-110 MPH--probably had engines that were still only putting out around 10-12 HP.
~

 

[cashman]

Floyd Clymer, who was a cinder track racer back in those days wrote a book called Treasury of Motorcycles of the World and in it he talked about the "valve wars" that went on between the racers. Seems that combustion efficiency was a hot topic back then and everyone had a different method. Those numbers which sound pretty low by todays standards, illustrates how far combustion technology has come to today and continues to be refined. And back in those days, they didn't have a fuel that had been tailored for use in internal combustion engines like we do now. But that was all cutting edge technology back then. Still, it took a lot of courage to hop on one of those and reach the speeds they made.

 

[cobrafreak]

Yes, a 1911 single cylinder Indian is 500 cc's and has 4 HP (!), while my motorbike Indian with the 66 cc 2 stroke puts out 2.25 HP. Not a whole lot of difference. I wonder if there are any torque ratings available for the old bikes. Torque is a lot different than HP. HP is the speed that the engine can get up to full power while torque is the work that the engine can do. So while the old bikes could get to 60 mph, how quickly did it take them to achieve this speed?

 

[masterpoop63]

well its obvious isnt it?they werent wearing safety equipement :mrgreen: makes you go 1000x faster per horse power :mrgreen:

 

[deorman]

SAE vs dynometric- My Honda is about 7 1/2, or probably around 50 or so. My little 25cc weed-whacker motor kit could probably propel a bike 50 mph with a smaller slave ring, but you'd need to pedal or add a gearbox to get moving or climb the slightest grade.

 

[cobrafreak]

You could go the NASCAR route for power reduction. Put a restrictor plate (a piece of metal with a smaller hole between the carb and engine). You could make an 883 Harley very very low power if you wished.