Tuesday, 16 March 2010

It's Harder Riding a Touring Bike

Before purchasing the Raven Nomad, I'd previously only ridden light-weight racing bikes. On my Seven Axiom Ti I have years of speed averages around the 27-30 km/h mark. I was a bit shocked when I rode the Nomad for the first few times and could only manage 22-23 km/h!

This average speed reduction is due to a number of factors including an increase in bicycle mass, a more upright riding position and increased rolling resistance from running lower pressured tyres.
    I've yet to ride the Nomad in full touring trim, as I'm still researching and purchasing equipment, but I wondered how much more average speed I would lose when the Nomad was loaded up with panniers and 24 kg of luggage? I thought I'd do some maths...

    The Equations

    There are two major components of resistance to overcome when riding a bicycle. One is air resistance and the other is road resistance (a combination of friction and gravity). The power (in Watts) required to overcome these resistances can be represented approximately as the sum of equations (1) & (2) below:

           Pair = ½ρ(vc+vwind)2CwAfvc   (1)

    where ρ = Air density = 1.293 kg/m3, vc = speed of cyclist (m/s), vwind = wind speed (m/s), Cw = Drag Coefficient, Af = frontal area of bike and cyclist (m2)

           Proad = gmvc(Cr+s)          (2)

    where g = gravity = 9.81 m/s2, m = mass of cyclist and bike (kg), vc = speed of cyclist (m/s), Cr = Combined Frictional Coefficient (mostly tyres, but also chain, hubs etc.), s = grade (slope) (E.g. 8% = 0.08)

    The Assumptions

    I've made some assumptions for the constants Cw Af and Cr based on information available here. I weigh about 72 kg in my cycling kit. Mass below is for the bike and rider combined.

    Bicycle Mass (kg) Cw (-) Af (m2) Cr (-)
    Seven Axiom Ti 81.5 0.9 0.45 0.003
    Raven Nomad (Unloaded) 88 1.0 0.60 0.007
    Raven Nomad (Loaded) 112 1.0 0.70 0.007

    I've also made the assumption that I have a sustainable upper power output of around 230 Watts. I don't own a power meter, but I've reached this figure based on some test numbers I've calculated whereby I matched power output to speeds and conditions I was familiar with for both the Seven and the Nomad (unloaded).

    Cycling along the flat

    In the case of cycling along the flat with no headwind, grade (s) and Vwind are both 0. From the two power figures it can be seen that much more power is required to combat air resistance than road resistance. Speeds for a power output of around 230 Watts range from 33 km/h (9.3 m/s) for the Seven, down to 26 km/h (7.3 m/s) for the loaded Nomad.

    Bicycle Pair (W) Proad (W) vwind (m/s) grade (m/m) vc (m/s) kmhc (km/h) Diffseven (%)
    Seven 207 22 0 0 9.3 33.3
    Nomad (U) 183 47 0 0 7.8 28.0 0.84
    Nomad (L) 174 56 0 0 7.3 26.2 0.79

    Cycling up a hill

    In the case of cycling up a 8% hill, grade (s) is 0.08. This time, much more power is required to combat road resistance (chiefly gravity) than air resistance. Speeds for a power output of around 230 Watts range from 12 km/h for the Seven, down to 8.5 km/h for the loaded Nomad.

    Bicycle Pair (W) Proad (W) vwind (m/s) grade (m/m) vc (m/s) kmhc (km/h) Diffseven (%)
    Seven 10 221 0 0.08 3.3 12.0
    Nomad (U) 10 221 0 0.08 2.9 10.6 0.88
    Nomad (L) 6 226 0 0.08 2.4 8.5 0.71

    Cycling into a headwind

    In the case of cycling into a 20km/h headwind, Vwind is 5.6 m/s. An even greater proportion of power is required to combat air resistance as would be expected. Speeds for a power output of around 230 Watts range from 22 km/h for the Seven, down to 16 km/h for the loaded Nomad.

    Bicycle Pair (W) Proad (W) vwind (m/s) grade (m/m) vc (m/s) kmhc (km/h) Diffseven (%)
    Seven 218 15 5.6 0 6.1 22.0
    Nomad (U) 202 29 5.6 0 4.8 17.4 0.79
    Nomad (L) 199 34 5.6 0 4.4 15.9 0.72

    Cycling into a headwind up a hill

    Probably the worst situation in cycling! Again cycling into a 20km/h headwind, this time on a 3% slope. Now it's pretty much an even split between power required to combat air resistance and power required to combat road resistance.

    Bicycle Pair (W) Proad (W) vwind (m/s) grade (m/m) vc (m/s) kmhc (km/h) Diffseven (%)
    Seven 114 116 5.6 0.03 4.4 15.8
    Nomad (U) 114 114 5.6 0.03 3.6 12.8 0.81
    Nomad (L) 104 125 5.6 0.03 3.1 11.1 0.70

    Coasting down a hill

    No effort is required here! Assuming the hill is long enough, the bike and rider will reach a terminal velocity when Pair and Proad cancel each other out. The slope is -8% and assume no wind. For the first time, the loaded Nomad is not the slowest! It's extra mass triumphs, but it's not enough to beat the Seven's better aerodynamics and frictional properties.

    Bicycle Pair (W) Proad (W) vwind (m/s) grade (m/m) vc (m/s) kmhc (km/h) Diffseven (%)
    Seven 943 -943 0 -0.08 15.3 55.2
    Nomad (U) 803 -803 0 -0.08 12.8 45.9 0.83
    Nomad (L) 1066 -1066 0 -0.08 13.3 47.9 0.87

    Average Speed for the Loaded Nomad

    For the test cases, a rider capable of generating 230 Watts should be able to propel the Unloaded Nomad between 79%-88% of the speed of the Seven and the Loaded Nomad between 70%-87% the speed of the Seven.

    I can make this (very crude) deduction for myself. If I can manage 28 km/h average for the Seven, I should be able to average about 83% of that on the Nomad Unloaded and 76% of that on the Nomad Loaded. This equates to about 23 km/h for the Unloaded Nomad (which agrees with my recorded averages) and 21 km/h for the Loaded Nomad (as yet untested).

    I've scheduled my trip at a leisurely 18-20 km/h average, so I hope my rather assumptive mathematics is reasonably valid!

    [1] Cycling Speed Maths and Ruminations
    [2] Bicycle Performance
    [3] Coefficients of friction. Rolling Resistance, Air resistance, Aerodynamics
    [4] Energy consumption during cycling

    Sunday, 14 March 2010

    Back to Halifax Post-Trip

    Update: I've now decided to fly straight out of St. John's back to the UK, so won't get to do all of this route. However, if I'm up on my schedule, I should have time to explore the Avalon Pennisula further...

    The schedule I've set to cycle across Canada and the route I've chosen in the east of the country both offer a nice amount of contingency. I've scheduled the ride at a hopefully comfortable 120 km for each riding day, with 12 full days off the bike. My route in the Maritimes is meandering and since I'm riding across Newfoundland the long way from Channel-Port aux Basques it's certainly not the shortest route and could be trimmed considerably, if necessary.

    This is all good and sensible and should ensure I reach my goal of St. John's one way or another. My trans-atlantic flight back home is from Halifax, Nova Scotia, though. If I'm still on schedule (and I haven't chucked the bike in the sea at St. John's) I hope to complete my tour with a leisurely ride back to Halifax. A sort of post-tour wind-down. As a considerable bonus, I will get to explore the southern half of the Avalon Peninsula via the Irish Loop and Cape Shore on Newfoundland and the southern shore of Nova Scotia via Marine Drive.

    If I have the time and the legs for the full route, it will add a further 950 km of cycling. The observant amongst you will realise I've now got my trip total up to 9,920 km. I may have to do a tiny bit more wandering along the way to crack 10,000 km!

    Friday, 12 March 2010

    Vancouver Island Pre-Trip

    Before I set off up the Sea to Sky highway, I'm going to take a short cycling tour on Vancouver Island. I haven't got time to explore the island fully on this trip, but I did want to experience a flavour of it, so I'm going to ride from Nanaimo to Tofino via the Pacific Rim Highway. It's about a 400 km round trip.

    Many X-Canada cyclists use Victoria, BC rather than Vancouver, as their 'official' starting point because it has the Mile 0 of the Trans-Canada Highway. (There's another Mile 0 in St. John's, if you're travelling east to west). It also presents a traditional photo opportunity due to the well known sign marking the point.

    I'm not actually using much of the Trans-Canada Highway on my route. I'm riding just the odd bit around Banff, Winnipeg and Sault Ste. Marie and some longer sections further east on Prince Edward Island and across Newfoundland. So Mile 0 doesn't hold a lot of significance for me. What is important to me, though, is a 'proper' Pacific-Atlantic ride...

    Vancouver, my starting point, technically doesn't face out to the Pacific as Vancouver Island is in the way! The Pacific Rim National Park coastline between Tofino and Ucluelet on the other hand does. So for an authentic Pacific-Atlantic road-trip, I'm riding to Tofino!

    Here I can dip my wheel in the ocean (a cycletouring tradition when doing a coast-to-coast) and dip it again at St. John's. I may also pick up a Pacific Coast pebble, carry it on my journey and lob it into the Atlantic when I get there!

    All very symbolic and something I forgot to do when I rode across the US in 2007...

    Wednesday, 3 March 2010

    Easy Rohloff Sprocket Removal

    I was reminded by Vik's post, referencing this forum post, that it was time to check I could still remove my Rohloff Speedhub Sprocket. I had planned to release the sprocket every 2500 km to avoid any future trouble. I'm at 2700 km now and 4 winter months riding done, so I'm about on schedule!

    The Rohloff Speedhub Sprocket can be difficult to remove
    (if you leave it on too long)

    Rohloff sprockets have some notoriety for becoming struck on tight, partly because Rohloff have specified a threaded sprocket in preference to a splined sprocket and lock-ring arrangement, but mostly because people leave the sprocket on far too long before trying to remove it. I wasn't expecting any problem removing my sprocket at this stage and that's how it turned out. It unscrewed easily.

    Removing the sprocket: Fix the sprocket removal tool with the quick release nut,
    arrange the spanner and chainwhip
    and push down on the chainwhip (NOT the spanner)

    When I received my Nomad, I took most of it apart to be satisfied that everything had been prepared properly. (I'm not a very trusting person). To Thorn's credit, everything was fine. When I reassembled the bike I used my preferred copper based anti-seize preparation on most of the threaded components. Of course, I removed and refitted the Rohloff sprocket during this process as well.

    Use an anti-seize preparation when refitting

    Therefore, for today's quick operation, I had a Rohloff sprocket that was fitted using an anti-seize preparation and it had only been on the hub for 4 months and 2700 km. That's why it could be removed so easily.

    I do quite a lot of bike maintenance and I think most tasks are pretty easy with the right tools and preparation. Maintenance only becomes difficult when you leave it too long. Then you have to resort to long levers, hammers and grunting a lot. By regularly removing and refitting torqued threaded components, you can save yourself a lot of headaches.

    I've a comment regarding the positioning of the chainwhip in the forum post referred to at the top. (I also use a Park Tool SR-2). It has the chainwhip in the 10 position and the chain wrapped around the sprocket with a tie-wrap for extra security. I prefer the SR-2 chainwhip in the 8 or 9 position because more chain links are naturally engaged and then the tie-wrap isn't necessarily needed. There is still enough leverage in this position.

     More links engaged in the 8 position for about the same leverage

    Incidently, in the Rohloff video on sprocket removal, the chainwhip is attached 'upside down'. I tried this with the SR-2, but it won't grip that way at all. This suggests the best positioning may well depend on the chainwhip make and it's characteristics.

    The moral of the story here? Regularly remove your Rohloff Speedhub Sprocket and reassemble with an anti-seize preparation and you won't have any trouble. It should only take 10 mins and will ensure the sprocket always unscrews easily. While you're at it, how about extending this regime to include the pedals, cranks, bottom bracket and EBB as well...

    Monday, 1 March 2010

    Audax: Kennett Valley 100

    I did another audax ride on the Nomad at the weekend. This time it was the Kennett Valley 100 in Berkshire, organised by Reading CC.

    Everybody's looking forward to a February day out in the rain...

    This is a very popular winter event and there were around 60 riders on the 100 km event and I'd imagine a good number on the 200 km as well, although they'd already left by the time I rolled up to the village hall in Grazeley.

    Rain showers were expected throughout the day, but it was quite bright just before we set off and there was some debate about whether to wear rain jackets. I decided not to wear mine to start with, hoping to avoid the boil-in-the-bag effect for as long as possible. Of course, after all of 15 minutes it was raining and I was stopped at the roadside putting on my jacket! Within 30 minutes the rain was lashing down and jacket or no jacket everybody would be soggy for the rest of the day.

    The first leg out to Hungerford was pretty wet and horrible actually, but I was taking it easy today and spent time happily chatting to fellow riders on the road, including a couple on a Thorn tandem with a Rohloff hub! Approaching Kintbury, I teamed up with Chris and we rode the rest of the day together. (I'll call him Chris, but it could have been Mark! I'm best described as 'disappointing' for remembering names. I've tried word association to help me out but I seem to forget the associations I've made just as effectively! Chris is the chap on the right of the picture above and in the foreground of the picture below).

    Chris (or maybe Mark) in his 'tasteful' Marmite cycling jacket

    The rain had mostly stopped by the time we reached the halfway point at the Tutti Pole cafe in Hungerford. Beans on toast (of course) and cake and tea was ordered and swiftly dispatched to my stomach. Chris's missus had driven out to meet him, so I chatted to them both for quite a while, hoping to dry out a bit at the same time. Unfortunately that didn't work at all and it felt decidedly chilly setting off after the warmth of the cafe.

    The route back via the "Berkshire Alps" was hillier though, so we soon reverted back to our warm and damp state. The scenery was very nice, especially around Boxford and Winterbourne, with snow drops in abundance brightening the otherwise dreary day. After navigating through Theale, we were on the last leg back to Grazeley, drying out now, but with a mildly irritating headwind for company!

    A good leisurely paced ride for me today, 130 km in total and not spoilt too much by the weather. You can't expect anything better at this time of year in the UK. There were even some polite 4x4 drivers about. Whatever next. Thanks to Chris/Mark for the road chat and good luck with your Super Randonneur aspirations. Thanks also to the event organisers.

    I managed to pick up my first puncture on the Nomad after 2600 km although luckily the tyre didn't go flat until the following day!