On Jan 25, 3:29 pm, "Clive George" <
[email protected]> wrote:
> "Andre Jute" <[email protected]> wrote in message
>
> news:[email protected]...
>
> >The entire affair went so smoothly that I felt we could have tried for
> >100mph rather than 100kph but I wasn't sure the standard tubes were
> >good for it (I'd want double tubes and nitrogen inflation for higher
> >speeds to avoid disastrous heat rise) and anyway we would need a
> >longer piece of road we could block off without inconveniencing
> >anyone. The disc brake wasn't even too hot to touch and I never needed
> >to apply the rear brake to stabilize the bike.
>
> Nitrogen won't make any difference. Use decent tyres at suitably high
> pressures, and you won't suffer heat rise. Punctures could be very nasty at
> that speed - not sure how to avoid that, apart from checking the road very
> carefully.
I used Schalbe Marathon Plus tyres because I already had a new set.
They're still on the bike a couple of years later.
> A single stop from speed won't actually test the brake very much. It's
> keeping something heavy, like a tandem, under constant braking which does
> it.
> I only got to 49mph when slipstreaming a truck in the flatlands of Cambridge
> before my legs ran out of spin - 52x12 top gear (I might have been able to
> spin faster for a short time, but the truck wasn't accelerating terribly
> quickly). What was interesting was the buffeting as I dropped back - quite
> unpleasant.
You have to set the truck up right or you can take a nasty spill if
you release directly into the over-the-kamm eddying. The best sort of
truck is a refrigerated truck, among other reasons because its weight
causes smooth transitions in motion. The rear doors are opened at 45
degrees or more, depending on the width of the road, and stayed with
rods attached to the lock mechanisms with ratcheting pipe clamps. The
space at the bottom across the back and below the doors is filled in
with 19mm ply; you need three 8x4ft sheets. When the truck accelerates
after releasing you, and you slow anyway because the grade isn't steep
enough for the speed, the width of the aero envelope puts your
exposure to the buffeting further back where it is already much
weaker. I know quite a bit about airflow over and behind fast cars
(I'm the author of a book on designing and building prototype and one-
off cars), and this problem is another reason I didn't even think of
trying for the 100mph rather than the 100kph.
> cheers,
> clive
I'm impressed with your journey behind the truck: not with the dashing
speed or the impressive athleticism but with your daring. I wouldn't
dream of trying what you did without an ambulance helicopter standing
by. I remember the roads around Cambridge as being rough to cycle on
-- not to mention finding potholes that defeated the suspension of my
Citroen SM -- and no better than Irish roads, which are appalling.
There was one smooth good road though, to Burwell near Newmarket, that
was a pleasure in the very early mornings when it was not too heavily
trafficked. And when there were roadworks roundabout Hauxton
somewhere, there was a huge mound of earth, highest spot on the Fens,
that we raced down on the first mountainbikes, when straight
handlebars were a rarity.
Andre "Chicken" Jute