More hair, less speed
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Forum Name: Etc
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URL: https://forum.bhpc.org.uk/forum_posts.asp?TID=964
Printed Date: 27 March 2026 at 4:35am
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Topic: More hair, less speed
Posted By: Adrian Setter
Subject: More hair, less speed
Date Posted: 30 October 2006 at 12:27pm
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Cut your hair and go faster - http://www.bikebiz.co.uk/newsitem.php?id=24644 - http://www.bikebiz.co.uk/newsitem.php?id=24644
------------- Challenge Hurricane - MicWic Delta (Front half) - Burrows Ratracer |
Replies:
Posted By: fards
Date Posted: 30 October 2006 at 12:38pm
| I've got slower as the hair as decreased, but then that seems to parallel with getting fatter and older. |
Posted By: GeoffBird
Date Posted: 30 October 2006 at 9:24pm
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I've never had any trouble keeping my head cool when wearing a helmet....oh....I see why now...
I doubt a lot of cyclists go fast enough for anything more than convection currents to have any effect  . Perhaps the BHPC could utilise it's collective expertise in aerodynamics to market an improved racing helmet.------------- Right Time - Right Place - Wrong Speed |
Posted By: Hadden
Date Posted: 05 November 2006 at 2:56pm
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Are we allowed to use a helmet of our own design and construction to race in? how about a series of NACA ducts in it to keep the drag down? ------------- Simon Sanderson. |
Posted By: GeoffBird
Date Posted: 05 November 2006 at 5:12pm
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Hadden wrote: "how about a series of NACA ducts in it to keep the drag down?"
Interesting idea. My experience of wind tunnel testing is that exit ducts are at least as important as entry ducts. It would certainly be an fascinating project though. Conventional helmets look like they are optimised for low speed use.
 I think using our own designs of helmet would be problematic and my invalidate our insurance (Alan?), but perhaps a light shell fitted over a type-approved helmet? ------------- Right Time - Right Place - Wrong Speed |
Posted By: Hadden
Date Posted: 05 November 2006 at 6:03pm
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It should be possible to make a much tougher and better shock absorbant helmet as mass produced ones use quite low performance materials. ------------- Simon Sanderson. |
Posted By: fards
Date Posted: 05 November 2006 at 8:23pm
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And very few UK available Helmets comform to any form of sensible standard nowadays.. The new euro/uk regs are a joke. |
Posted By: Rob
Date Posted: 05 November 2006 at 8:37pm
What, worse than the old 10mph fall from 1metre[1] onto a flat surface? Rob [1] Hey, does that imply that a 'Sports' class recumbent is considered the 'standard' bike??? ------------- -- Rob, Westcountry Recumbents http://www.wrhpv.com http://mullimages.com http://glydearoundbritain.blogspot.com |
fards wrote:Posted By: AlanGoodman
Date Posted: 05 November 2006 at 9:34pm
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There is nothing in our insurance specifying what helmets (if any) should be worn...
Our insurance only covers us for damage we do to other people...
I spent 16 years at the British Standards Institution testing (among many other weird and wonderful things) cycle helmets.
Apart from the often poor quality of the shells many have retention sysyems that are VERY poor at keeping them in the right place in the event of an accident.
Having said that in certain types of impact you are certainly better off wearing one than not...
I usually wear a woolly hat in the winter and a peaked cap in the summer...
------------- |
Posted By: gNick
Date Posted: 05 November 2006 at 10:25pm
Basically no - we work to a requirement for a helmet that is "approved by a recognised national standards authority". Unless you are in a fully enclosed streamliner where you have to wear some kind of padding on the bonce. If someone is prepared to make a helmet that is a helmet rather than a head fairing then if there is sufficient evidence to its conformance to standards we would probably allow it. Whether there is any sense in making one is another issue! The helmet rule is something that came in some time ago but is not in any way related to our insurance. Whether or not the helmet is of any value to HPV racers could evoke much debate but certainly you won't be allowed to race without one! ------------- gNick "I'm afraid it's definite, Mrs Banker - your son has bicycles" |
Posted By: fards
Date Posted: 05 November 2006 at 10:28pm
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The new EN 1028 is a laughable farce.. A helmet that meets it's requirements will only absorb 1/3 the energy of those designed to meet the snell b96.. So sod all in fact.. Table at the end of this sums it up.. http://www.cyclehelmets.org/papers/c2023.pdf - http://www.cyclehelmets.org/papers/c2023.pdf (reprinted from CTC mag). To tie in with any standards, gNick, Hadden, I can't see why someone like the guys that do this testing couldn't test yours to see if it was conformant. Other than the cost obviously. |
Posted By: KeithD
Date Posted: 06 November 2006 at 7:18pm
| Does anyone ride with an aero helmet? I was surprised not to see any at Reading in September. |
Posted By: Neil F
Date Posted: 06 November 2006 at 7:29pm
| Yes, Big Ian and I ride with them. I don't use it at every race, it depends on the temperature (poor cooling) or twisting tracks. |
Posted By: Twed
Date Posted: 13 December 2006 at 1:05pm
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Why does it depend upon "or twisting tracks"?!! ------------- Never believe an atom they make up everything. |
Posted By: KevinJ
Date Posted: 13 December 2006 at 2:14pm
Though I am not sure how whether it will really be able to improve to a massive extent. Trawling around the internet it seems that the brains tolerance is less than 50g before damage. So if you assume that the helmet has got to stop you then hitting a solid object. Let's assume the material is perfect. So it slows your head in an even acceleration until it stops. So we have the bike velocity V at brain damage level, a deceleration a. then V^2 = 2aS where S is the thickness of the padding. Lets assume a is 50g (the max) i.e. approx 500m/s^2 S will be about 3 cm - 0.03 m Then V^2 < 2*500*0.03 = 30 ==> V = 5.5 m/s is that about 12.5MPH That seems worryingly low to me so I have probably made a mistake. Anyone know where? ------------- Kevin Jenkins Windcheetah |
Posted By: kit wolf
Date Posted: 13 December 2006 at 3:51pm
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==> V = 5.5 m/s is that about 12.5MPH
That seems worryingly low to me so I have probably made a mistake. Anyone know where? I don't think you made a mistake - but that's also about the speed your head would hit the ground if you were to fall off an upright sideways. Opponents of cycle helmets say this design speed is so low as to make helmets next to useless as most collisions (esp. those involving motor vehicles) involve higher impact velocities. There's an oft-repeated claim that bike helmets aren't designed to protect you in crashes faster than 12mph - which is nonsense on any bike save a lowracer, because you have to work out the vector of the forward and downward motion of the head - which would be 1.412x12 ~= 17mph. By their reasoning, helmets actually wouldn't protect you in any accident when you were moving and also fell to the ground. Although it's possible to cycle into a brick wall, or to fall straight towards the kerb, these are worst-case scenarios and I imagine most accidents involve considerably lower forces. For example you might hit a windscreen glancingly, or fall to the ground and slide a bit. Even windscreens have quite a bit of give in them (I passed the aftermaths of two bus/pedestrian accidents in the past few weeks, and the depressions in them were several inches deep - both accidents occurred in 20mph zones and I suspect at least one was fatal). How useful that little bit of protection actually is, I have no idea. It was discussed in depth on uk.rec.cycling a few years back: http://groups.google.co.uk/group/uk.rec.cycling/browse_thread/thread/9dcadcea1df34a89/13aabfc9b0398c97?lnk=st&q=helmet+12mph+anonymous+coward&rnum=1#13aabfc9b0398c97 (warning - heat as well as light). I think there are links to the Snellen testing specs on the parent thread. Kit |
Posted By: AlanGoodman
Date Posted: 13 December 2006 at 4:37pm
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For what it's worth, I worked for BSI from 1980 to 1996 testing (among other things) cycle helmets. I was involved with the development of the PAS (Product Approval Specification) that we used to Kitemark them before the British Standard was finalised.
The PAS and the BS were pretty much just written around what was available at the time, and a lot of those products were er.. Poo! I'm sure things have improved over the past 10 years, but I still see one of the main problems as being the retention systems. I've never had a helmet I feel confident would stay in place in the event of an impact. I very rarely wear a helmet other than for racing. Alan. ------------- |
Posted By: Neil F
Date Posted: 13 December 2006 at 7:16pm
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Twisting Tracks.
well you need to move your head round to see into the corners and I find that the tail doesn't help head modility - especially as I only had 2 inchs cleararance to the rear wheel on the NoCom.
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Posted By: Andrew H
Date Posted: 16 December 2006 at 11:05pm
What worries me about helmets is the lack evidence that they are useful. In places where they are compulsory they don't seen to reduce the rate of serious injuries - they just reduce the number of peole cycling! Most serious head injuries to cyclists are caused not by a straight blow, but by a blow that causes rapid rotation. I wonder whether the helmet, being considerably bigger than the head, increases that risk. So I only wear one when racing - or to keep the hood of my anorak in place in the rain, which it does rather well!
------------- Andrew Horne One Challenge Wizard - so far |
Posted By: AlanGoodman
Date Posted: 17 December 2006 at 8:00am
Not just the size... The shape of the helmet shell and position/shape/size of ventilation features also have a big effect on rotational forces in the event of an impact. A lot of work was done on this for motorcycle helmets, and those tests (with tri-axial accelerometers/load cells) resulted in a big change to the mechanisms used for attaching visors as well as to ventilation features and overall helmet design... ------------- |
Posted By: kit wolf
Date Posted: 18 December 2006 at 2:15pm
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For what it's worth, I worked for BSI from 1980 to 1996 testing (among
other things) cycle helmets. I was involved with the development of the
PAS (Product Approval Specification) that we used to Kitemark them
before the British Standard was finalised. Feeling embarrassed about my previous reply now, but I'm curious: do you know how the guidelines were designed. Basically, did somebody say "this is how much protection a helmet needs to give, in order to be worthwhile", or did somebody say "This is how much protection it's reasonable to build into a helmet, so we'll use it as a basis for the guidelines". Kit |
Posted By: AlanGoodman
Date Posted: 18 December 2006 at 5:00pm
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There is always a bit of a need for a balance between drawing up the best possible specification and coming up with something that manufacturers can produce at a sensible cost... No point in having a specification that nobody works to.
For that reason most British Standards are (or were in my day...) largely written around the best of the products that are available and then amended as the quality of materials and methods improve. The committee producing the standard had representatives from manufacturers as well as BSI, RoSPA, Department of Transport etc. Alan ------------- |