The Power meter arrived.

It is not a thing of great beauty but it does make the bike go much faster. The mechanism by which it achieves that is simple. It measures the power output of the rider. That finds its way onto Strava where all the world can see it. Therefore the rider works harder so as not to appear a wimp. As a consequence the bike goes faster. QED.

It is the round thing half way along the left crank arm.

It is a Stages Left power meter. This is pretty much the cheapest way to measure power. It goes without saying therefore that it’s not the best but it will suffice until next year’s Tour de France.

A power meter is a strain gauge. They can be put in different parts of the drive train for example in the spider that holds together the chain ring, the cranks or at the rear hub. Perhaps the optimum place is one in each pedal which has the advantages of measuring the output of each leg separately and being easily transferred from bike to bike. Using a single crank measures the output of a single leg and entails the assumption that the two legs are equal which probably isn’t exactly true. However I always use the same left leg so the metric can be compared usefully from ride to ride.

So what exactly does it do?

A quick revision of terms and units in mechanics will come in handy. Work is basically weight through distance. For example Robert and his bicycle through 50 km. It takes a certain amount of energy to accomplish the work. The units that energy is measured in is the joule. A handy way of quantifying work is the number of joules required to complete it.

Robert and his bicycle can travel slowly or a bit more quickly, The work done is the same. Power is the rate of doing work or put another way – all those joules divided by time and the answer is in Watts.

A power meter measures the rate of doing work in Watts. Your speed will vary when going up hill or down, with the wind or into it. The power meter will still tell you how much effort you’re grinding out whereas your speedometer will not.

The Stages Left comes mounted on a crank arm which replaces the original. If anyone would like to purchase a left Shimano Ultegra crank I have one for sale. Setting it up to work with my Wahoo Elemnt Bolt bicycle computer could not have been easier. Insert the battery in the power meter. Using the Wahoo app on the phone introduce the two bits of high tech. Download the Stages app and zero the power meter. Go for a ride.

One of my first impressions as I set it up was that the battery cover was a very flimsy piece of plastic. Without it the rather expensive meter won’t work. This could be an issue. However it’s still in place after a couple of hundred kilometers. Maybe they thought of that.

The next step is to put it to profitable use. Stay tuned … but for now some wise advice from Dr Oliver Bridgewood.