Are Shafties Harder to Roll Than Chain Drives?

[nhmaf]

One really gets an appreciation for how much work 1 HP equals when pushing a 450 pound motorcycle up a hill on a gravel road - most unpleasant!  At least the 1 mile of paved road was easy by comparison..

[Barry]

One really gets an appreciation for how much work 1 HP equals when pushing a 450 pound motorcycle up a hill on a gravel road - most unpleasant!At least the 1 mile of paved road was easy by comparison..  

I agree 1 HP is a lot more than we think and having also tried and ultimately failed to push my bike up an incline  I couldn't resist working this one out.


1 HP will lift 550lbs in 1 sec so 450lbs in 0.82 sec.

Assuming a modest pushing pace of 2 miles per hour or 2.93 ft/s
1 hp would be able to push the bike up a 1 in 3.58 slope -  I think there's no chance of that at least not by me.

A normal untrained person (that's me) is able to sustain only in the region of 75 watts for an hour or 1/10 of a HP

So that would equate to a slope of 1 in 35.8 which sounds about right as I was easily defeated by a 1 in 10 slope. It eventually took two of us with lots of rest periods.

We can do better than 1 in 35.8 for a short while but even a modest incline is a killer for any distance and rolling resistance on the level is insignificant by comparison.


Actually those calculations underestmate the task because we are also raising our own body weight at the same time as pushing the bike.

[nhmaf]

.. somehow I thought Barry wouldn't be able to resist doing the maths on that one!  

I was able to push the bike up some paved slopes pretty well but I highly doubt I was able to sustain anything close to 1HP for any length of time, too.   What was most crippling was trying to push the bike uphill on a gravel road - pushing hard resulted in my feet just slipping as the surface of the loose gravel gave way, and I nearly fell on my face with the bike toppling onto me.   After VERY slow progress I eventually got to a flat spot where I could leave the bike while I walked the remaining half mile back home to get my truck and trailer.

[georgesgiralt]

Hello !
I've had the great opportunity to test the rolling of my R65 by hand.
I had the bean can Hall sensor fail, so I got a replacement and last Sunday dismantled, affixed and soldered the new one in place. Bike started on first attempt, and a couple of minutes later I was on the road to test the bike, having a huge smile on my face.
It ran for exactly 1.5 km and then stopped like someone hit the kill switch. Fortunately enough I was at a traffic light. No ignition. As I used a Siemens sensor instead of the unobtainium Honeywell, I thought it was the sensor which was not good.
I had to push her up to the top of the hill where my home and garage was. Boys, that's hard ! I was exhausted when I finally came home.
I dismantled the bean can to find that the rotating steel cover (cutting the magnetic field to signal for ignition) had caught two of the three wires, cutting the red one straight...
So I now can tell that's hard to push a BMW ! And boy, they're HEAVY !  

[Barry]

.. somehow I thought Barry wouldn't be able to resist doing the maths on that one!

Looking back I missed out an important detail. It should have read:

1 HP will lift 550lbs 1 foot in 1 sec so lift 450lbs 1 foot in 0.82 sec.

Trust me the rest of it was correct