Darly moor speed?
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URL: https://forum.bhpc.org.uk/forum_posts.asp?TID=668
Printed Date: 27 March 2026 at 1:18am
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Topic: Darly moor speed?
Posted By: LeeW
Subject: Darly moor speed?
Date Posted: 05 June 2006 at 11:32am
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How did your avarage speed on your bike computer compare to the speed on the darly moor results page? I ask this since the speed on the results page is 1.1Mph faster than what I got on my bike computer so I am wondering if my computer needs re-calibrating. ------------- Current fleet: Milan SL MK2 #027, Fujin SL II, Beany! |
Replies:
Posted By: Andrew S
Date Posted: 05 June 2006 at 11:53am
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You will probably find that the length of almost all circuits as listed on our website is greater than as measured by your speedo, which accounts for the higher speeds. At least part of the reason is that the 'official' circuit length is measured down the centreline of the track, which is longer than any reasonable racing line. I've never been entirely convinced that this accounts for all of the difference, but have never actually measured the centre line and racing line on any circuit to see what the difference is. For the record, I recorded avg 24.4mph vs 25.2 official - smaller than your difference. How do you calibrate your wheel diameter? I measure at least 10 rotations, using the tyres and pressures I use for racing, sitting on the bike. My neighbours can attest to the bizarre and obsessional measurement of the pavement outside my house. |
Posted By: Rob
Date Posted: 05 June 2006 at 12:40pm
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25.6mph on computer, 26.5mph 'official'. The difference is quite normal and consistent... In the past I've carefully recalibrated my computers to 'BHPC Speed' by fine tuning based on the %age differences over a few races but maybe that is being obsessive..... Measuring lower is an incentive to work harder! <grin> Rob ------------- -- Rob, Westcountry Recumbents http://www.wrhpv.com http://mullimages.com http://glydearoundbritain.blogspot.com |
Posted By: Rob
Date Posted: 05 June 2006 at 12:45pm
Ah, the old school book problem of raising a wire fence around the equator of the earth (yes, I know it is mostly water)... You put the first wire in and then decide you want a 2nd wire 0.5metre higher - how much more wire will you need for the 2nd wire than for the first? Rob ------------- -- Rob, Westcountry Recumbents http://www.wrhpv.com http://mullimages.com http://glydearoundbritain.blogspot.com |
Andrew S wrote:Posted By: antony
Date Posted: 05 June 2006 at 1:33pm
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Would that not be dependant on how high (more accurately, how far from the centre of the earth) the first wire was? Or were they looking for a formula for the answer rather than a specific number? And, presumably, the book was wrongly assuming the earth to be a perfect sphere and also ignoring the minor imperfections of topography superimposed onto it. Besides, I think you'll find the answer is: No more. It'll stretch enough to cover the difference. And if not, just miss a bit out round the back somewhere where no-one will notice. Make sure you get paid in full, in advance. Don't forget to leave some slack to cover mid-ocean ridges and some tensioning devices for subduction zones. 
PS. For all your fencing needs, see www.bodgitandscarper.com. Ahem, sorry. 
------------- Deja mu: The feeling you've heard this bull before |
Posted By: LeeW
Date Posted: 05 June 2006 at 1:35pm
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My magnet is on my right wheel. My speed would have most likley been a bit higher if my magnet was on the left wheel ------------- Current fleet: Milan SL MK2 #027, Fujin SL II, Beany! |
Posted By: KevinJ
Date Posted: 05 June 2006 at 1:46pm
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I can only see that making a difference of about 5 Metre distance per lap, so that would mean that it is only about 0.2% difference. ------------- Kevin Jenkins Windcheetah |
Posted By: gNick
Date Posted: 05 June 2006 at 1:46pm
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3.1415927(.....)m or PI metres (circ=pi*D,and new circ=pi*(D+(2*0.5)= pi*D +pi*1; thus difference is pi*1)
So for a 10m wide track with all the curves in the same direction you will travel 31.416m further on the centre line than on the inside line. Most of us will not be travelling on the inside line all the way round so assuming the racing line is about half way between the inner line and the centre line we are doing about 15m less per lap than the specified distance. For Lee this makes a the projected average speed 25.032mph rather than 25.193 (based on 15 laps in 52min 9.89s). Methinks speedo calibration might have a bit more to do with it! ------------- gNick "I'm afraid it's definite, Mrs Banker - your son has bicycles" |
Posted By: KevinJ
Date Posted: 05 June 2006 at 2:06pm
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Sorry gNick - was using the same formula (I am a mathematician!) but was just trying to account for the diffence between having the speedo magnet on the different wheel.
Incidentally http://www.sidenet.co.uk/circuits/infoDarley01.htm - http://www.sidenet.co.uk/circuits/infoDarley01.htm
has it as 2.41 Km (we are only 2.35) so that woul make everyone even faster!!! ------------- Kevin Jenkins Windcheetah |
Posted By: legs_larry
Date Posted: 05 June 2006 at 2:13pm
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Most of the circuit lengths were measured by the then-Editorial Cateye, so are at least definitively inaccurate...
------------- ==================== a bit ov a lyv wyr by slof standirds |
Posted By: gNick
Date Posted: 05 June 2006 at 2:28pm
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So we are looking at a then-Editorial racing line as Thee Officialle Distance?
No probs Kevin - I writ my bit off line and then posted it after yours when it was writted before.
According to the Darley Moor official map ( http://www.darleymoor.co.uk/1trackmap.htm - http://www.darleymoor.co.uk/1trackmap.htm ) the length is 1.5miles or 2.414km
So we should just go and calibrate our speedos properly - there is a measured mile not too far from the current-Editor's residence... ------------- gNick "I'm afraid it's definite, Mrs Banker - your son has bicycles" |
Posted By: antony
Date Posted: 05 June 2006 at 2:38pm
Then again, the Blackbushe site defines their track as 600m (it's 515m) and for a long time and probably still, the Preston site claims theirs is 1500m (it's closer to 1600m).  ------------- Deja mu: The feeling you've heard this bull before |