Bike Aero

[Adam43]

In Moto GP what are the major considerations with regard to bodywork?

I assume it is just to make it as slippery as possible, allowing for any cooling. Or have I got it completely wrong? Downforce as such doesn't really apply because of the lean angles(?) (although under braking it could help).

So is it simply slippery is best?

I consider this superficially on and off, but this time it was prompted by Rossi's aero devices by his hands.

[GORDON STREETER]

Adam.. I can remember "dustbin" fairings in the 50s that were outlawed because it made the bikes too fast for the brakes of the day. So the more slippery they can make it the better. I don't know if the latest shape of fairings are any better or worse than those old designs and I have always wondered why they haven't re- introduced the all enveloping style.
Possibly it can't be done in the rules, or are they still outlawed in road racing ? as all the top land speed record bikes use them.

[Locost47]

The Moto GP guys do put a lot of effort into drag but they do little or nothing about lift. Bikes have terrible nose-up pitching moments (largely but not exclusively due to the high centre of pressure for drag) and consequently high front lift. This will get worse when they sit up under braking too and that's something they do look at, though they don't focus on cornering aero as much as you'd perhaps expect.

[Dennis.Doyle]

Yet another subject I know S.F.A. about, but won't let that stop me speculating

Since a bike leans to way more than 45 degrees (up to about 67 so I'm told currently), if you were to put something like a conventional car wing on the bodywork, the force outwards would be greater than the force downwards, i.e. it would be worse than nothing.

Alternatively, if you were to put a conventional aeroplane wing, i.e. giving lift rather than downforce, on this would be reversed. Since lift is most certainly going to kill you under various other circumstances, I guess this is why they don't go in for downforce/lift?

Even if they aren't wheelying for the spectators, I'd guess the changes in attitude are so gross that, aero mods (apart from reducing drag) would be a bit of a mixed "blessing".

[Jeff 8]

Originally Posted by GORDON STREETER

Adam.. I can remember "dustbin" fairings in the 50s that were outlawed because it made the bikes too fast for the brakes of the day.
Possibly it can't be done in the rules, or are they still outlawed in road racing ?

Dustbins were banned in 1957 because of sudden and unpredictable handling in cross winds. They still are, if you see the DVD "Faster" you will see how Red Bull Yamaha tried to make their bikes as quick as the factory bikes with a Pterodactyl like nose, it was faster in testing but had other problems in the races and dropped them.

I often wonder what modern bikes would look like if they were not banned.

[Speedy1]

one of the guys in the work complex was looking to improve aero losses on his race bike
I had him bring in the rule book to study in an effort to find areas of improvement
Current GP bikes have about as much aero body work as they are allowed
the teams do spend time in wind tunnels looking for the little bits that add up
A few have tested at the low speed tunnel in San Diego LSWT.com

[GORDON STREETER]

I know this should really be on a bike forum but a lot of us old boys remember the amazing start of the multi cylinder revolution in motorcycle racing.
The Moto Guzzi 500 V8 with a full dustbin fairing clocked 178mph at the Belgian GP in 1957 with only 75bhp. I think that is a good argument for an all enveloping fairing. GP bikes today don't do a lot over 200 mph with 3 times the power ! Ok I know speed isn't linear with power but how fast would a modern GP bike go with one of the "dustbin" jobs.

[Notso Swift]

Is a "dustbin" a fully enclosed wheel?
if so, front or rear or both.

I always wondered why front wheel wer not fully enclosed as I thought it was an area where safety could be improved, if nothing else.

[GORDON STREETER]

Yes Notso fully enclosed . Take a look at some of the early to mid 50s GP bikes on the net. Some of them really went to town !

[Jeff 8]

Originally Posted by Notso Swift

Is a "dustbin" a fully enclosed wheel?
if so, front or rear or both.

I always wondered why front wheel wer not fully enclosed as I thought it was an area where safety could be improved, if nothing else.

How could enclosing the wheel improve safety? The bottom would still be exposed, look at ice speedway with studded tyres and wheel guards that almost fully cover the tyre, they still have to wear thick protective gear.

A "Dustbin" is a fairing that encloses the front wheel and front of the bike, in one piece.

Jeff

[phoenix]

Originally Posted by GORDON STREETER

The Moto Guzzi 500 V8 with a full dustbin fairing clocked 178mph at the Belgian GP in 1957 with only 75bhp. I think that is a good argument for an all enveloping fairing. GP bikes today don't do a lot over 200 mph with 3 times the power !

For the same drag coefficient and if the machines weighed the same, and 3 times the power 308 mph should be achieveable

[Speedy1]

go to You Tube to see movies of "worlds fastest bicycle"
81 MPH on about 550 watts (.73 hp) peak
also fun to look at
www.speedtrialsbybub.com for the motorcycle edition of Bonneville

[ubrben]

I work for Dunlop in MotoGP and jointly engineered Alex Hofmann on a Ducati last year. There was about a 20mph headwind in warmup and he said "this bike's like a giant sail" having almost crashed when it unloaded the front.

The best comparison of approachs is probably in seat booms. The Honda and Yamaha are very slender in lateral cross-section whereas the Ducati is larger.

The compromise seems to be between reducing pressure drag in the upright position for straightline speed and having too much vertical force unloading the rear tyre as the bike is leaned over. The larger seat boom will create larger forces in this situation.

Ben

[chunder]

I remember a few years ago a guy called John Mockett was very invovled with aero work for bikes, he did lots of differenat shape bodyworks for Yamaha tea,s, I rememebr a very bulbous 250 Yam that Kocinski rode and he also did some detail work on the Roberts bikes at the time. I think also he did the big dustbin fairing on the Harris Yamaha that Emmett rode.

Again on the Aftser video you see Hopper testing a giant fairing on teh Red Bull Yamaha but they see no gain from it.

I think bikes are very much more subjective than cars, its harder to gauge aero work coz every rider rides different. I know Ducati have done a lot of work with their GP bikes oer the years and it seems to be paying off, it seems though that they also have the best and most powerful engine. This allied to the right aero makes a fast bike.

Anotehr area of great concern years back was the loaction of the air inlets for the airbox, even now you see many different variations, most though are content with w front of nose arrangement.

If you lo now aswell, most bikes have a very tapered rear end almost to a point, this must be for aero reasons, there was much static work done on rear ends in the 500- days and since GP with tiny exhausts that can be outlet near the riders feet it sees that tail and seat units are getting smaller all the time, I would ahve though that area was a great area for finishing off the airflow over the rider, maybe the sharp tapered style is the best??

[Jeff 8]

I think the tapered rear on bikes is to prevent slipstreaming as it leaves a smaller "wash".

Check out what some F1 designers did with a clean sheet of paper, planning aero first rather than add on later.

http://www.motorcyclenews.com/MCN/Ne...icturegallery/

It may work but we have seen people with new ideas before not able to sustain interest in bikes while they play catch up to the established manufacturers. Names like Ilmor, ELF, Bimota, etc spring to mind.

Jeff

[Gerben24]

what I find funny is that they talk about the feel of the bike, like they are Motogp riders that have already ridden it.

Furthermore, I would be very surpised if this concept works without a frame. First of all, all the stresses from the suspension will be going into the engine-block. Second of all, current riders can not ride a bike with a frame that does not 'bend'. I dont know who it was, it could be Aprilia, who made a frame out of carbon fibre. This frame was to stiff and was unusable, therefore they went back to a 'metal' frame.

Still, good on them to show interest in bikes.

[chunder]

Interetsing point but I dont necessarily agree with you about some of that coz Roberts have come in and made parts for many manufacturers whilst also keeping their feeet in the water with a race bike.
OK the man involved is never likely to walk away unless he runs out of money coz IRTA want him there more than anyone else.

But the point made about Ilmor is true, I just think they were naive really, they though "hey we can build a bike early and there will be plenty of people wanting to sponsor it" I think they were geniunely shocked at the lack of interest, eitehr that or something far more sinister is at play there!

As for ELF they only really managed to run coz of Honda. Honda gave them free engines in retutn for Elf and De Cortanze developing ideas that Honda wanted to patent! The single sided rear, the hub centre front etc.
If it wasnt for Honda Elf would never have stayed in the class as long as they did, and when De Cortanze left the bikes pretty much stayed static anyway, Haslam only got so far with the development then got fed up and rode an NSR!!

Bimota I am not sure of, they basically in the early days built frames for the race bikes and never intended to race their own bikes really.
The 500 was a disaster from the start and was so eagerly anticip[ated that they rushed it rhough and made some huge cock ups. Their 4 stroke bikes were usually good, with the 600 wining races and Gobert winning a WSBK race, but again without help from Japanese they would not race.

Read a fascinating hsitory of thema while ago, in the early days of the SB1 and KB1 they actually had to get crashed bikes to build a Bimota to get hold of the motors and electronics, they didnt get a deal with teh Japs til a few years later! Ambulance chasing Italian style!

[Speedy1]

Thanks for posting the link
pretty darn low cda estimate

anyone remember the Britten?

Originally Posted by Jeff 8

I think the tapered rear on bikes is to prevent slipstreaming as it leaves a smaller "wash".

Check out what some F1 designers did with a clean sheet of paper, planning aero first rather than add on later.

http://www.motorcyclenews.com/MCN/Ne...icturegallery/

It may work but we have seen people with new ideas before not able to sustain interest in bikes while they play catch up to the established manufacturers. Names like Ilmor, ELF, Bimota, etc spring to mind.

Jeff

[Jeff 8]

I was looking at the bike and that I was thinking, Britten, I suppose the last successful bike from a clean sheet of paper built in a shed. His ideas were different but they worked, probably through his determination not some team of highly paid engineers. His ideas on aero was different too, minimal frontal area, radiator under the seat.

Jeff

[chunder]

Britten was a clever engineer but if you remember his original bike it was far mroe radical aerodynamically, it had huge wings over the riders hands etc!

The problem for me with teh Britten was you never really saw it run against the best riders int he world, it was always in a Twins race or a one off thing like Isle of Man or NZ where it was the class of the field.

For me the engineering in that bike was second to none, John got very good power from a 1000 Vtwin long before anyonme else and he did it without Desmo or Pneumatc valves.

Aero wise I think he was a little lacking as the bike was mainly like that to work wround the chassis he was using, or rather lack of chassis!

The innovations on the bike were incredible, the aero work was interestingk the forks, stressed engine, exhaust, so many things. The man was a genius!

Gerben, it was Cagiva that made a carbon frame, as d d the old Skoal Heron Suzuki team. The frame really worked and was dropped by Suzuki when they started with the V4.
Aprilia tried one on 250 but it was too stiff and the Cagiva one was actually a latter half of the frame with teh headstock in ally. But they did use carbon swing arm. I think you could get the flex these days, carbon is almost as flexible really, its all in the mix and the heat cycles I guess??
As for stressed engines, a lot of teams do that now, Ducati been doing it for donkesy years.

[trikesrule]

Interesting article Jeff. I race a Gravity Bike (no fairings) and every bit of drag reduction I can get in this class (Stock Gravity Bike) helps. Yes making the bike as narrow as possible and reducing the frontal area all helps. Anything ahead of the rider must be used to 'break' the air ahead of the bike. In my case I used my arms to help the air around my shoulders. I drop my knees dpwn to air brake instead of siting up like most do. Theses mc designers want drag reduction - they should be talking to some of these gravity bike racers........trikes

[trikesrule]

Sorry about the misspelling but the admin cut me off.......trikes

[Speedy1]

guy with the hairy balls in this picture is the one riding the machine with hard, tiny wheels and NO brakes holding the video camera with one hand recording the ride
wait ... that's not a bike .....

Originally Posted by trikesrule

Interesting article Jeff. I race a Gravity Bike (no fairings) and every bit of drag reduction I can get in this class (Stock Gravity Bike) helps. Yes making the bike as narrow as possible and reducing the frontal area all helps. Anything ahead of the rider must be used to 'break' the air ahead of the bike. In my case I used my arms to help the air around my shoulders. I drop my knees dpwn to air brake instead of siting up like most do. Theses mc designers want drag reduction - they should be talking to some of these gravity bike racers........trikes

[Speedy1]

the latest issue of Bernoulli hit my mailbox today (California)
it includes a 4 page aero article on GP bikes
interesting
in essence states the same as this thread, comparing against automotive, not much research is being done on single track vehicles