 |
|
 |
|
|
| Author |
Message |
| Itchy |
This post is not being displayed .
|
Itchy
Super Spammer
Joined: 07 Apr 2005
Karma : 
|
 Posted: 19:22 - 10 Jul 2014  Post subject: pointy headlights/drag? |
 |
|
https://www.motorcyclenews.com/upload/278400/images/gsr750-5.jpg
So we get bikes increasingly which have pointy headlights, my assumption is it is for aerodynamics as the old style circular headlamps with a flat front in the direction you are going are about as aerodynamic as a house brick.
But considering you've got a completely unaerodynamic rider sitting on it holding wide bars, not particularly aerodynamic engine block. How much energy exactly is saved by putting a pointy headlamp on it, or is it just a style thing?
____________________
Spain 2008France 2007Big one 2009 We all die. The goal isn't to live forever, the goal is to create something that will. In the end, your life will flash before your eyes. Make sure it is worth watching. |
|
| Back to top |
   |
You must be logged in to rate posts |
|
 |
| Fisty |
This post is not being displayed .
|
Fisty
Super Spammer
Joined: 11 Apr 2007
Karma :  
|
|
| Back to top |
 |
You must be logged in to rate posts |
|
|
| recman |
This post is not being displayed .
|
recman
World Chat Champion
Joined: 26 Mar 2012
Karma : 
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Slacker24seve... |
This post is not being displayed .
|
Slacker24seve...
World Chat Champion
Joined: 10 May 2010
Karma : 
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| ADSrox0r |
This post is not being displayed .
|
ADSrox0r
World Chat Champion
Joined: 23 Oct 2012
Karma : 
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Teflon-Mike |
This post is not being displayed .
|
Teflon-Mike
tl;dr
Joined: 01 Jun 2010
Karma : 
|
Posted: 21:05 - 10 Jul 2014  Post subject: |
|
|
The old round headlamps had a plain mirrored reflector behid the bulb, and the flat lens 'focused' the light chucked forwards and deturmined the beam pattern. That's why it was flat.
In 'clear lens' lamps, the lens is clear, and doesn't focus the beam pattern; instead the reflector is sort of crinkly, with lots of complex panel sections to catch and reflect light through the clear lens already in the desired pattern.
It's supposed to be more efficient, as it's suggested you can loose as much as 30% of the light i a 'diffuser' (flat) lens. And made possible by modern CAD techniques and high accuracy moulding, to accurately shape the reflector.
Advantage of the lens being pointy to aero-dynamics is probably bog all, even on a full-faired bike, though may reduce a bit of turbulence, and likely direct more air round the sides, rather than up over the clocks; but main technical advantage is likely to be that like a Gothic arch over a square lintel, the curve will take more load for a given thickness, so the lens may be thinner/cheaper/lighter, and less likely to vibrate or flex or wobble, or break from stone strike etc.
I HAVE to believe these things are significant... I would absolutely hate to think that it is merely the stylists being given cart-blanche to do so much 'ugly' all on thier own!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Kickstart |
This post is not being displayed .
|
Kickstart
The Oracle
Joined: 04 Feb 2002
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| gsxfdumb |
This post is not being displayed because the poster is banned. Unhide this post / all posts.
|
gsxfdumb
Banned
Joined: 19 Jun 2014
Karma : 
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| talkToTheHat |
This post is not being displayed .
|
talkToTheHat
World Chat Champion
Joined: 21 Feb 2012
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| deadwolf |
This post is not being displayed .
|
deadwolf
Could Be A Chat Bot
Joined: 24 Jan 2013
Karma : 
|
| Posted: 02:58 - 12 Jul 2014 Post subject: |
|
|
One theory I have about current bike design trends (i.e. fugly pointed angular steaming pieces of ****) is that engine/chassis/tyre performance has advanced sufficiently to the point that you can easily reach current speed limits without the need for functional aerodynamics as part of the bike's design. Hence the stylists get more free reign to play around with the plastic since it's of little consequence to overall performance.
Proper slippery shapes are thus only important when breaking speed records, while modern technology will ensure that even a brick of a bike will do license-threatening speed.
Imagine if bikes were allowed to do say 300MPH tops for whatever reason. In the short run manufacturers might put more effort into actual aerodynamics to help reach that speed while the engine and cycle parts are catching up.
____________________
Motorsapien Art |
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Northern Monkey |
This post is not being displayed .
|
Northern Monkey
World Chat Champion
Joined: 17 Nov 2013
Karma : 
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Teflon-Mike |
This post is not being displayed .
|
Teflon-Mike
tl;dr
Joined: 01 Jun 2010
Karma :
|
Posted: 08:44 - 12 Jul 2014  Post subject: |
|
|
| deadwolf wrote: | One theory I have about current bike design trends (i.e. fugly pointed angular steaming pieces of ****) is that engine/chassis/tyre performance has advanced sufficiently to the point that you can easily reach current speed limits without the need for functional aerodynamics as part of the bike's design. Hence the stylists get more free reign to play around with the plastic since it's of little consequence to overall performance |
I'm inclined to agree with you; it is about marketing, and a plateau in technology meaning that aesthetics is one of the few 'features' designers have very much creative freedom to play with.
But it is also cultural; motorcycles now are selling more and more as life-style accessories, where the 'look' of the product is often the biggest sales motivator; buyers want to look like their GP hero's or ideas of a Bad-Boy Biker, and dress to the image, where in days of yore, bikes sold significantly more as utilitarian transport, where the image wasn't as important as whether they owner could change their own tyres and adjust their own tappets.
'Performance' seems to be of much more academic interest these days; with polarisation between the utility commuters, now significantly compressed into the sub 125 capacity class and limited by the A1 licence limits; and the 'Leisure bike' now starting really at 600cc and up, where a certain level of performance is presumed, and most bikes have more than 'sufficient', so its merely how much a buyer is prepared to pay for more; so the engineering challenge, is not often to find 'more' performance, but make it cheaper, and keep the tree-huggers happy while they do it.
It's all about 'product design', and where once upon a time bikes were designed by chaps in overalls, with greasy fingers saying 'yeah! That works good, now lets tidy it up a bit" They are designed by committee, like i-phones or food mixers, with stylists and accountants and marketing men, worrying about focus groups, colour schemes, sales projections and manufacturing costs, calling the shots as engineers, worrying about nuts bolts and stressing over fatigue limits!
As for breaking speed limits, without aerodynamics? Well, a humble YBR125, can break most UK speed limits, bar the elevated limit for duel-carriageways, with a mere 10bhp, and you only have creep up to the heady 15bhp of an old 1960's BSA 250 push-rod single, to start nudging over even that, without fairings; which is probably a slightly skew argument, but still.
Interesting to note, back in the 1950's, the Triumph 650 Thunderbird, with barely 50bhp could crack the ton, without stream-lining... stripped, mildly tuned for US 'High-Octane' gas, and fitted with a cigar streamliner fairing, it cracked the 'double ton', on the salt flats.
https://image.motorcyclistonline.com/f/features/122_1006_triumph_bonneville_beginnings/33204147+w620/122_1006_01_o+triumph_bonneville+left_side_view.jpg
failing to gain their accreditation as the 'worlds fastest production motorcycle' only due to an FIM technicality of the delay between two-way mean runs, but launching the Bonneville street-bike for the following year... while leaving the Vincent HRD 'the worlds fastest production bike', having made an FIM accepted record run on the salt flats at over 150mpg, with only a little over 60bhp from high compression & High-Octane, and a tiny test rider in a pair of speedo trunks, lying on the tank, without any fairings at all.
https://coldfury.com/images/VincentSpeedRecord.jpg
(I always associate this famour run with Bonaville maniac Jimmy Allen, but checking, it was in fact a completely different lunatic by the name of Rollie Free)
Japanese 'Muscle-Bikes' of the 70's, with the Z1 leading the way with Double-Over-Head Cam 900cc 'four', punting near 90bhp, struggled to punch much over 130mph; wasn't until the early 80's, and what would probably now be described 'part faired' bikes started becoming more common, and touting water-cooled engines with more than 100bhp, that they started scaring the high-side of 150mph.
And hard to say, really, how much aerodynamics have played in top speed; I mean the 'Naked' 60bhp Vincent was reckoned to be 'good' for 120mph, out the crate; same sort of power from push-rod Guzzi's gave early 850 'Le-Mans' similar top speed, and a Norton commando wouldn't be far behind. Late 80's we had the race-rep 250 two-strokes, punting similar power, and full 'race' fairings, but still only scaring 130'ish' for it.
Probably the most conscientiously 'streamlined' production bike, before the Busa, was BMW's K1.
https://www.bmbikes.co.uk/photos/specphotos/k1.jpg
Utilising their aircraft divisions wind tunnel, to sculpt the styling, it was a deliberate attempt to get a motorcycle to crack 150mph with a strict 100bhp Euro-limit engine.
But even then, I think, as much as anything, fairings/aerodynamics on motorcycles have probably increased stability more than they have reduced drag, and in increasing stability, made it easier to 'hang on' and exploit whatever speed you can get, going by the Vincent precedent, where 150mph is possible without any streamlining, if you are daft enough to ride in your undies, lying on the tank in swimming goggles, and hang on long enough!
Busa? They are now governed at 186mph or something aren't they? Did they actually crack the double ton on a stocker? I'm not sure, probably close enough; but from what, 180'ish' bhp give or take where you take the reading and whether you factor in any Ram-Boost 'bonus'... either way, its three times the shove that took the Thunderbird streamliner to the same speeds back in the 1950's!
'Technology', has certainly made speeds more accessible as the bikes have become more user-friendly, and put it in the grasp of the man in the street on show-room motorcycles, but easy to argue its always been there, and there have always been the more deturmined, who from way back when, have opened the taps, and risked all, to wobble and weave thier way to whatever end, on whatever they could get thier hands on; whether that was a BSA A65, or Bonnie in the days of the ton-up-boys, or even earlier, a big JAP V-Twin in the '30's, or later, in the 70's or 80's a Kawasak H2 750 two-stroke tripple, Laverda Jota, or early 'wobbly wheel GSXR-1100; with teenage rights of passage emulating them on whatever lightweight with saggy chain and upside down handlebars they have to hand!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Wafer_Thin_Ham |
This post is not being displayed .
|
Wafer_Thin_Ham
Super Spammer
Joined: 18 Nov 2005
Karma :
|
| Posted: 08:47 - 12 Jul 2014 Post subject: |
|
|
Lovely, but a bit dodgey in cross winds. 
____________________
My Flickr |
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| deadwolf |
This post is not being displayed .
|
deadwolf
Could Be A Chat Bot
Joined: 24 Jan 2013
Karma :
|
| Posted: 09:32 - 12 Jul 2014 Post subject: |
|
|
| Teflon-Mike wrote: |
But it is also cultural; motorcycles now are selling more and more as life-style accessories, where the 'look' of the product is often the biggest sales motivator; buyers want to look like their GP hero's or ideas of a Bad-Boy Biker, and dress to the image, where in days of yore, bikes sold significantly more as utilitarian transport, where the image wasn't as important as whether they owner could change their own tyres and adjust their own tappets. |
[rant]Frankly, that's what I don't like about current naked bike designs. Posers and imitators used to be confined to GP-wannabes and Harley pirates, while commuters and standards looked more unpretentious and benign. Now they're also being tarted up and you end up with superficial plastic crud like the Z800 which looks like a hunchbacked Transformer toad.
I'd rather have some round-headlamped UJM thingy that doesn't have to be swathed in overstyled plastic because I can appreciate a bike for what it is and am not after whatever social effect riding a 'modern' standard is supposed to conjure up. Bikes have always been effortlessly cool, they don't need to be tarted up with any more plastic chintz beyond what is necessary  [/rant]
Anyway rant over, on with the show..
| Teflon-Mike wrote: |
the Vincent HRD 'the worlds fastest production bike', having made an FIM accepted record run on the salt flats at over 150mpg, with only a little over 60bhp from high compression & High-Octane, and a tiny test rider in a pair of speedo trunks, lying on the tank, without any fairings at all.
Japanese 'Muscle-Bikes' of the 70's, with the Z1 leading the way with Double-Over-Head Cam 900cc 'four', punting near 90bhp, struggled to punch much over 130mph; wasn't until the early 80's, and what would probably now be described 'part faired' bikes started becoming more common, and touting water-cooled engines with more than 100bhp, that they started scaring the high-side of 150mph.
And hard to say, really, how much aerodynamics have played in top speed; I mean the 'Naked' 60bhp Vincent was reckoned to be 'good' for 120mph, out the crate; same sort of power from push-rod Guzzi's gave early 850 'Le-Mans' similar top speed, and a Norton commando wouldn't be far behind. Late 80's we had the race-rep 250 two-strokes, punting similar power, and full 'race' fairings, but still only scaring 130'ish' for it.
|
Yeah, that's a pretty interesting comparison. Where along the line does all that extra power made by the Japanese stuff get lost? Is it in the tradeoff for heavier and more reliable components or some other factors?
This might sound totally far out but I've started thinking of 'speed' as a big pie, and different bikes as different-shaped forks, all trying to slice out the biggest piece of the speed pie. And it looks like you can change the length, shape and number of prongs as much as you want, but eventually there's not much difference in the amount of pie you scoop out. Hence explaining the different approaches that all end up arriving at more or less the same arbitrary point i.e. 150MPH
| Teflon-Mike wrote: |
Probably the most conscientiously 'streamlined' production bike, before the Busa, was BMW's K1.
Utilising their aircraft divisions wind tunnel, to sculpt the styling, it was a deliberate attempt to get a motorcycle to crack 150mph with a strict 100bhp Euro-limit engine. |
Looks like streamlining would get more priority when other things like engine power is restricted...but why not just build a modern Vincent?
| Teflon-Mike wrote: |
But even then, I think, as much as anything, fairings/aerodynamics on motorcycles have probably increased stability more than they have reduced drag, and in increasing stability, made it easier to 'hang on' and exploit whatever speed you can get, going by the Vincent precedent, where 150mph is possible without any streamlining, if you are daft enough to ride in your undies, lying on the tank in swimming goggles, and hang on long enough!
|
This is probably the most important and overlooked point IMO, so far a lot of the discussion about aerodynamics is about top speed, but like Pirelli's motto goes, power is nothing without control...
| Wafer_Thin_Ham wrote: |
Lovely, but a bit dodgey in cross winds. |
Brings to mind this article I read recently, some electric bike manufacturers want to use dustbin fairings to improve range but the same old disadvantages that got dustbins banned in racing also work today:
https://www.fasterandfaster.net/2010/03/dustbin-fairings-and-motorcycle-racing.html
Article also makes a short but interesting point about bike design by comparing the Hayabusa and Britten, both being damn fast bikes despite one wearing a watered-down dustbin and the other sporting a mere half fairing.
____________________
Motorsapien Art |
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Kickstart |
This post is not being displayed .
|
Kickstart
The Oracle
Joined: 04 Feb 2002
Karma :
|
| Posted: 12:46 - 12 Jul 2014 Post subject: |
|
|
| deadwolf wrote: | One theory I have about current bike design trends (i.e. fugly pointed angular steaming pieces of ****) is that engine/chassis/tyre performance has advanced sufficiently to the point that you can easily reach current speed limits without the need for functional aerodynamics as part of the bike's design. Hence the stylists get more free reign to play around with the plastic since it's of little consequence to overall performance.
Proper slippery shapes are thus only important when breaking speed records, while modern technology will ensure that even a brick of a bike will do license-threatening speed. |
Irony is that compared to modern bikes a brick (well, one with smooth surfaces and slightly rounded corners) is probably not that unaerodynamic .
But ignoring UK pre speed limit motorways it takes relatively little power to hit the UK national speed limit.
| deadwolf wrote: | Imagine if bikes were allowed to do say 300MPH tops for whatever reason. In the short run manufacturers might put more effort into actual aerodynamics to help reach that speed while the engine and cycle parts are catching up. |
At that speed aerodynamics become massively important. They might even have to start thinking about what actually causes drag (ie, then complete aerodynamic mess that is the back of the bike).
| Teflon-Mike wrote: |
And hard to say, really, how much aerodynamics have played in top speed; I mean the 'Naked' 60bhp Vincent was reckoned to be 'good' for 120mph, out the crate; same sort of power from push-rod Guzzi's gave early 850 'Le-Mans' similar top speed, and a Norton commando wouldn't be far behind. Late 80's we had the race-rep 250 two-strokes, punting similar power, and full 'race' fairings, but still only scaring 130'ish' for it. |
The race replica 2 strokes probably are better with aerodynamics, but the big thing is that they are quite peaky and sensitive to gearing. While a 45hp TZR250 could manage about 120mph, the KR1S with about 60 hp (with high standard gearing, and conditions not being unfavourable) managed 143mph in a road test. If the conditions were not good then top gear would probably be pretty useless for top speed.
| Teflon-Mike wrote: | But even then, I think, as much as anything, fairings/aerodynamics on motorcycles have probably increased stability more than they have reduced drag |
It is probably the need for stability that has prevented aerodynamics from getting better. As mentioned the cause of the drag is the back of the bike, hence the point that the drag acts on is fairly far back on the bike which gives stability. Improve drag at the back and this point moves forward and the bike become less stable. Like trying to through a dart backwards (of trying the stand on top of a parachute when drifting down  ).
| Teflon-Mike wrote: | Busa? They are now governed at 186mph or something aren't they? Did they actually crack the double ton on a stocker? I'm not sure, probably close enough |
Realistically they might just about manage to hit the 186mph speed limiter when stock in neutral conditions.
All the best
Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing |
|
| Back to top |
| |
You must be logged in to rate posts |
|
 |
Old Thread Alert!
The last post was made 12 years, 92 days ago. Instead of replying here, would creating a new thread be more useful? |
 |
|
|
This page may contain affiliate links, which means we may earn a small commission if a visitor clicks through and makes a purchase. By clicking on an affiliate link, you accept that third-party cookies will be set.
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum
|
Read the Terms of Use! - Powered by phpBB © phpBB Group
Debug Mode: ON - Server: birks (www) - Page Generation Time: 0.26 Sec - Server Load: 1.8 - MySQL Queries: 13 - Page Size: 110.98 Kb
|
Help & FAQs
Search BCF
Members
Groups
Events Calendar
rating
rating