Thursday, August 11, 2011

FNF - Drafting Revisited

You kind of expect to hear that bad 70's porn music right about now - bow chicka wow wow...


Generally speaking I don't find that new hampshire has much to offer a socialist liberal atheist like myself. However, they do two things very well - they maintain the national forest land, and they keep their roads in great shape. One of the sections of road I have to travel to get to my job now is a 4 mile stretch of route 111 where it crosses route 3 and heads west ( yes, in new hampshire, just in case you aren't aware). I actually take route 111 from Windham near the route 93 interchange to quite near the Mass border for my commute, but for the purposes of this blog entry, we'll stick with the western terminus.

This section of road is - much like the rest of route 111 all the way to the seacoast - in great shape. Smooth, wide shoulders, very few patches or any other non-asphalt items to break up the tarmac. Add to that very gentle sweeping corners, very flat terrain, no stop signs or stop lights, and nothing but residential side roads, and you have a good road for driving and riding...and drafting.

Wednesday morning I crossed the highway and saw a large box truck waiting at the last stop light for the next 4 miles. It popped it into the big ring, passed a few cars and tucked in behind the truck. I had no idea how far he was going. He could very well have pulled off at the next side road.

But he didn't.

He kept going...and going....and going.

He kept a smooth steady pace of about 40 for most of it, but as he crossed the town line from nashua to hollis, he pushed the speed up to about 45. My computer registered a maximum speed of 46.8. That's a drafting record for me, my previous some years ago being 46.

Now, I know what you're thinking...."47 mph on flat ground? something is wrong with your computer".

Well, no. You can see from the downloaded data above my cadence was in the high 120s.

Do the math.

A 700c wheel with a 23C tire has a circumference of 6.67 feet. I have a 53x11 on this bike which is a ratio of 4.81, so one turn of the cranks moves the bike 32 feet (4.81*6.67 = 32.13).

47 mph is 4136 feet per minute. Therefore, if you divide the speed by the distance for each pedal revolution, you get you cadence in revolutions per minute. 4136/32.13 = 128.7 rpm. Check the max cadence in the data above, you get...128 RPM.

You can also see from the data I wasn't working very hard. My heart rate actually dropped as my speed increased. Aside from the initial effort to catch the draft (peaked at 650 watts), it was pretty easy going.

But, I know you didn't come here today for a math lesson, so here is what you _did_ come for, Fully Naked Friday, Gotta luv a woman that can accessorize.......



bikenliftr said...

I saw you that day on the return trip.

CB2 said...

Are you kidding? I love math!