Thursday, 15 April 2010

Going faster for no extra effort

Yesterday evening I had a small problem with my Mango which meant I couldn't ride it home, so I rode my old two wheel Pashley PDQ recumbent instead. This has been languishing in the back of the ligfietsgarage for six months since my Mango was ready to ride and I abandoned my old friend.

It actually felt great to ride the old bike again. I've made many journeys on it in the past and it was a return to a very familiar feeling. In fact, it was better than it had been for a while, because not long before it was "abandoned" I'd spent quite a bit of time sorting it out with new chain, cassette, chainring, mudguards, even a new fork to replace the rusty looking one I was using (thanks to Tom who gave me his spare PDQ fork several years ago). The PDQ felt very light-weight after riding my Mango, acceleration between 0 and 20 km/h seemed instant. I enjoyed riding it. I had a bit of a tailwind for going home, and it took just 56 minutes to get home last night on the PDQ. For me, that's a good time in real conditions over 30 km on the PDQ.

Of course this morning the same tailwind was a headwind. It took me an hour and 3 minutes to get to work. Again not too bad on that bike with a headwind, but then there is what happens when I ride the Mango instead...

Both days have had much the same weather. Dry with a Northerly wind (i.e. blowing from work towards home). Yesterday morning it took just 53 minutes to get to work against the headwind in the Mango, and this evening in the newly repaired Mango it took just 49 minutes and 10 seconds to get home again. Those are average door to door speeds of 33.5 km/h into the wind and 36 km/h with the wind vs. 28 km/h and 32 km/h on the PDQ. I'm quicker in the Mango with a headwind than on the PDQ with a tailwind. It's a speed difference of between 12 and 20% - the greater difference being with a headwind, which is what you'd expect with an improvement in aerodynamics. A tailwind tends to even different bikes out.

The improvement in efficiency is amazing. Compared with a normal bike, or even most recumbents, the Mango allows you to propel yourself further and faster for the same effort.

This got me thinking. Some years ago I came across Walter Zorn's excellent bicycle speed calculator on his website. Unfortunately, I understand that Walter passed away last year. While his personal website is still viewable, not all of his excellent work is. In particular, his bicycle power and speed calculator has been offline for some time and I could only find it on the wayback machine.

While Walter's calculator has always had the Quest Velomobile in it as an option, it didn't have an option for the Mango. I've made a modified version which includes the Mango velomobile taking figures for Mango aerodynamics from other websites and the weights of real Mangos, including my heavy one fitted with the wonderfully puncture resistant Marathon Plus tyres (I ought to change them now that winter is over).

The calculator also still includes many other types of bikes, from upright roadsters through racing and time-trial machines and a variety of recumbents. One of the options is for a short wheel-base touring bike which produces numbers which are reasonably believable for my PDQ. By comparison, the option I added for my Mango gives just about the right difference in speed from that "PDQ" option. It's interesting also to compare with newer, lighter Mangos, and to see what happens with a hill. Even in relatively flat places like the Netherlands, there is never a truly flat surface, so weight is always an issue. The light weight of the Mango Sport means that it really comes into its own with even the slightest of uphill gradients, especially when compared with heavier velomobiles.

The photos show me on my PDQ somewhere with rolling hills between Cambridge and London back in 2006, and my colleague Arjen test riding a newly produced Mango Sport earlier today on a cycle path in our industrial estate. I wrote about commuting speeds before. The infrastructure here also helps a great deal. NL is a great place to live if you like to cycle fast. Read my review of the Sinner Mango Velomobile.

11 comments:

Anonymous said...

Please compare the triptime once you get new faster tires on your mango.

I like seeing other posts than the usual about bike infrastructure.

Biking around Copenhagen, loking for a slot to park my bike, i came to think about why the slots where often installed against the bicycling direction, which means i can not simply drive past the slots and easily spot in advance which are free. I have to drive very slowly and turn my head looking back.

Does installations like that also happen in the Netherlands?

J.. said...

Funny how you told me just last week in Assen that you hardly ride your old recumbent any more, trying to ease my mind over the prospect of selling my Hurri, and now you're telling me how great it is to get on the old bike again.

I think you'll now see my point in not wanting to sell it. ;-)

David Hembrow said...

Anonymous: Glad you like the different type of post. It has to be noted, though, that a large part of the reason why my commute can be so quick is that the infrastructure makes it possible. The backward racks sound a bit awkward. There may be similar ones in NL somewhere. While the overall standard is very high here, and while the speed of updating is also very high, amongst the vast amount of infrastructure there is also old stuff, bad stuff and just not well thought through stuff. It just isn't very common these days.

J..: That is a fair observation. Your Hurricane is also a 20" wheel bike and shares characteristics with the PDQ (though it's also lower and faster). On the way home on the PDQ, with a tail-wind and the sun shining, it was very enjoyable. However, on the way back to work the next morning when it was still a bit cold, I was riding along with cold toes and cold fingers (I never need to wear gloves in the Mango). What's more, due to the headwind my progress seemed glacial compared with what I'm now used to. This all reminded me about what makes the Mango so great to ride, and what made me "abandon" the PDQ. I fear it may be another six months before I ride it again...

J.. said...

David,

Wearing gloves can't be that much of a fuss, but getting cold feet is just irritating. Having said that, the point of keeping an open recumbent even when you have a velomobile, is that you might want to really feel the breeze on hot summer days (days when cold feet are not a problem). You could reasonably feel a little trapped in a protective shell under those circumstances.

I've not had the privilege, but if I did own a velomobile I don't think I could get myself to sell my hurri.

workbike said...

I had a similar (though slower) experience when I went from using the Bakfiets most of the time to riding the Xtracycle after Winter. Suddenly hills I would sweat up were little lumps, and flat sections shot by.

That's an interesting point as well: I take it forgranted that in car-dominated Ostfildern, a ride will include annoying stips and short dog-legs to avoid junctions and motor vehicles, but without them, I can see how my journey time could be dramatically reduced.

I'd still like to try a Mango though...

Anonymous said...

Another reason for keeping the 2. bicycle in working order is for when something goes very bad with your primary bicycle, and you urgently need a backup.

Nick said...

What's this sudden obsession with speed all about? Personally I usually find I'm happy if I just get there; whether it takes 20 minutes or 20 minutes and 10 seconds is a bit academic.

Surely, if speed is such a concern, you'd do better in a car!

David Hembrow said...

Nick: There's nothing sudden about it. I've been racing on and off for many years. Why the interest in speed ? Simple. It's fun !

You're right that ten seconds difference is irrelevant. I don't worry too much about the odd ten seconds either, and my commute times vary by far more than that depending largely on the other people on the route. However, in my case the commute speed improvement by riding a Mango instead of the PDQ means saving not ten seconds, but an average of 15-20 minutes every day. That is significant. I can get up a bit later, leave home a bit later, get home a bit earlier.

Not only does it equate to time, but also to around 200 Kcalories per day less, which is reflected in feeling less worn out in the evenings and the next day after riding.

It's also about practicality. I doubt I would have been able to continue to do a 60 km round trip to work right through the winter when it was -10 C on an open bike.

On the other hand, I use a standard upright bike for visiting the local supermarket. Horses for courses.

I'm afraid I'm not much interested in cars. There's something horribly boring about them, even when travelling at speeds which would be truly terrifying on a bike. What's more, it'd make me fat(ter).

Nick said...

OK, now I see the point. I probably missed it in the first place because my own ride to work is only 20 minutes (or more accurately 18 minutes 20 seconds on a good day, traffic lights permitting).

J.. said...

Nick,
speed=comfort. Being more efficient not only allows you to go faster, but also allows you to travel at the same speed with less effort. That's part of the reason why some people ride recumbents, and it was one of the main tenants of the design philosophy of the guys at velomobiel.nl when they designed the Quest and the Mango.

Nick said...

No J, dynamic and mechanical efficiency equals comfort, not speed - but that's splitting hairs; I understand what you're telling me.