• 15th December 2003 - By greg
    Dec 15

    Dec 15, 2003

    Progress is going well and the HPV is ready for some serious miles and testing. But, it really sucks here in the winter. It was slightly above zero today, but where there isn’t ice on the road, there is plenty of slippery gravel. I have taken the HPV out for some short rides on a stretch of fairly clean and untraveled road, and I’m pretty happy with how it feels. At first it seemed really twitchy at higher speeds, but I think that’s just a result of getting used to riding a two wheeled recumbent, as I have never ridden one before and they are quite different. Your center of gravity s very low and as a result, you cannot use your body to balance, you have to rely 100% on the steering. I am getting the hang of it though – but at speeds of around 30 km/hour, it can seem like quite a bit of work keeping it going in a straight line.

    As a result, I am thinking about converting it to a trike¬†(3 wheeled HPV). One of the benefits of the FWD system is a simple rear end – just a front wheel and fork. To add two wheels to the back, I just need to bolt on a couple of front forks and fasten on two 650 wheels. Presto – instant trike. I’m going to rig up a removeable trike gear and run it through some tests to see how much stability the third wheel adds, and – most importantly, at what efficiency cost.

    My performance goal is still 40km/hour at 150 watts with the safest vehicle possible. If I can accomplish that with a three wheeled vehicle and a full fairing, then I’m set for my 10 day cross Canada plan.

    An essential part of the testing process is my SRM power meter which arrived the other day. Its basically a strain gauge that replaces the crank and chain wheel. When you press against the peddle, the strain gauges built into the chain wheel bend slightly (microscopically). The electronics then convert that strain to a watts value which is displayed (along with speed and heart rate) in a monitor mounted on the handle bars.

    The reason the SRM is important is to better control the testing environment. For example, the first thing I want to test is to see how much more efficient the lowracer is than my triathlon bike. I could simply take both out for an hour ride and record my average speed, but how would I know what my relative effort was for each test ride? To control that effort level and keep it consistant between all tests, I will use the SRM watts meter to ensure that I am putting out a consistant watts effort level. So, if I were to put out exactly 150 watts for an hour and travel 30 km on my road bike, to put out 150 watts for an hour on the recumbent might equal 35 km distance. A difference of 5 km/hr would equate to about a 20% increase in efficiency.

    Here is my current TODO list:

    1. Lace up the front wheel properly with new spokes.
    2. Replace the front hub bearings with new bearings
    3. Install the front wheel break
    4. Fabricate a trike extension for the rear end
    5. Buy two 650 triathlon wheels for the trike (and give Helen her 650 training wheel back)
    6. Get the SRM software working and get the trike out (somewhere???) for a good, 1 hour long 150 watt test ride.
    7. Do the same test ride with the triathlon bike to quantify efficiency of the recumbent
    8. Do the same test again, but with the trike extension on

    Here is my long-term TODO list:

    1. Build 2-wheeled low racer (DONE)
    2. Build trike extension
    3. Quantify efficiencies between 2 wheeled, trike and road bike (start accumulating performance data)
    4. Design and build tail fairing
    5. Quantify efficiency gains with tail fairing on both trike and 2 wheeled version
    6. Design and build front fairing
    7. Quantify efficiency gains with front fairing on both trike and 2 wheeled versions
      (remember – the goal here is to achieve a safe, comfortable HPV that will average 40km/hr with 150 watts effort)
    8. Rebuild the HPV with Carbon Fiber
    9. Quantify the efficiency gains by reduced weight of carbon fiber

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