Cunning oil cooler plan..so fiendish...

[Ghost]

A few years back I was in the wind tunnel at Mira with one of the Brunei cars.

This particular model had a long lower opening in the lower air dam /bumper.

A largish conventional grille above it. At speed no air at all went through the conventional grille. Aerodynamics is a real black art that can only be proven in these environments.

[geo7863]

Originally Posted by zimbo

Also, had you considered why there are two slots in the fairing? Could it be that they are there to reduce a low presure buildup behind the fairing nosecone at speed, which may possibly affect airflow over the air intake or around the vertical cylinder, and that diverting or blocking this air stream may have adverse aerodynamic effects elsewhere?

I wouldn't consider a second oil cooler necessary at all unless you have done a lot of work on the engine (big bore, high compression, porting, carburation etc). Just my opinion, of course.

No... air behind the slots, assuming the slots were blocked and there was absolutely nowhere for that air to go to, would have a static pressure of 1 ATM, the air flowing around the fairing and under the nose of the bike would have dynamic pressure, which is lower than static pressure and dependent upon the speed of the air, so in effect the air behind the slots (covered) would have an overpressure, compared to the air flowing past it

With such a flat square frontage on the 900ss most of that 'dynamic' air would be just turbulent air anyway, bubbling all around the back of the fairing.

Aerodynamics lesson over switch off brain.... Cor looks nice with the oil cooler there though dont it mate..

[markm]

mmmm food for thought. As George (bubled'n'boiled in bucharest) pointed out in a post of his elsewhere: much more fun than a tamiya or airfix kit (i prefer tamiya btw; and scratchbuilding is evern better! you should see the scratchbuilt 6 foot Titanic i did!).. Back to the bike:
Sticking the cooler in the nose is to me "visually" ok.. i'd have to get this to work without running into other problems mentioned by zimbo, ghost, mr r etc etc (and thanks for your thoughts! abs brilliant this forum; post an idea and you get loads of people bouncing back feedback and ideas! )..
A bypass valve (cheers Adrian ) good idea!
I guess, as George does, that at the end of the day i want to use the 2 absolutely (at present) useless intakes on the fairing.. and i've a perfectly good oil cooler dangling in the garage... i'll see what my fertile brain can come up with

mark

[Mr.R]

Hi Mark,
I've fitted an oilcooler in the nose of my old bevel 900, in the colder months of the year I blank it with an alloy plate.
Lots of racers just gaffer tape up the appature.
Norman Hyde who advertises in the classic mag's sells oilcooler conversion kits for old Triumphs etc, part of the kit is a thermostat/bypass valve, he may sell these separately?

Steve

[markm]

Originally Posted by Mr.R

Hi Mark,
I've fitted an oilcooler in the nose of my old bevel 900, in the colder months of the year I blank it with an alloy plate.
Lots of racers just gaffer tape up the appature.
Norman Hyde who advertises in the classic mag's sells oilcooler conversion kits for old Triumps etc, part of the kit is a thermostat/bypass valve, he may sell these separately?

Steve

Hi Steve, Christ thats a name from the past! He must be getting on a bit? I remember in the 70's him doing loads of stuff on the racing triples for the factory. My memory is a bit vague at the moment but i seem to remember him doing a monstrous triple based sidecar. But it was the Rob North framed bikes that did it for me...i used to drool over those bikes! I'm kicking myself nowadays because going back to 1992 i was at a "crossroads": buy one of the new hinckley triples or ressurect my old bonnie into one of Norman Hydes creations based on a North lookalike (think it was the Hyde Harrier).. i bought a triple and sold the bonnie (actually that year i did a number of stupid things: i got engaged, bought a house, sold a bonnie T120, a T140 and the most heinous crime ever committed: got rid of a T110...all in the name of love!!!! B*gger! I still love Triumphs)
Back to the Duke:
Cheers for bringing back Normans name to my memory got a feeling i may just find some useful stuff there so i'm off for a mooch around. Strange how this website and especially this forum sends people off on a tangent and possible wallett bashing

Mark

[AdrianK]

<<the nose of the bike would have dynamic pressure, which is lower than static pressure and dependent upon the speed of the air, so in effect the air behind the slots (covered) would have an overpressure, compared to the air flowing past it..>>

..... could you explain that a bit more? It seems a little counter-intuitive .

[geo7863]

Originally Posted by AdrianK

<<the nose of the bike would have dynamic pressure, which is lower than static pressure and dependent upon the speed of the air, so in effect the air behind the slots (covered) would have an overpressure, compared to the air flowing past it..>>

..... could you explain that a bit more? It seems a little counter-intuitive .

er if you really want me to?

This is what I learnt when studying for my pilots license.

Introduce an object into a body of moving air (or move that body through the air) and things happen to the air molecules. For some reason, unkown to me 'cos I is thick, when the air molecules are parted by the object they will meet at the same time when past that object.

I will give the example of an aircraft wing, or the spoiler on a F1 car (It snt really a spoiler as that is designed to 'spoil' the air flow and induce drag, the F1 cars have an upside down wing or aerofoil)

The upper surface of a wing (lower for F1) is usually more curved than the lower surface (upper for F1). when the air molecules meet the wing they part and go over and under the wing, when they get to the trailing edge of the wing they will get there at the same time (thats the bit I dont understand why).

The air molecules running over the top of the wing have a further distance to 'run' before they reach the trailing edge so to meet the lower wing air at the same time they move faster. This gives a lower (dynamic) pressure.

The air molecules under the wing, have a lesser distance to travel so are moving slower and have a higher (static) pressure. This is what gives the wing lift, and in formula 1 its this 'lift' upside down which presses the car against the tarmac.

This is also by the way how a carburettor venturi works, faster air running through the squeezed space gives a lower pressure, lower pressure means that it sucks the air in faster.

And also how carburettor icing works, even on a fairly warm day as lower pressure means lower temperature, which means air that is moist loses its ability to retain that moisture as the air cools, the moisture turns to water which can be cooled below freezing point and thus form ice on the carburettor butterfly valves, this is the main reason why light aircraft crash, carburettor icing, loss of engine power, loss of forward thrust, loss of lift, glide to a good landing point or die!

Now a bike is not a wing, so a lot of the air that the bike is moving through will be 'battered' out of the way and becomes turbulent very rapidly (this is form drag because the bike is not a clean smooth aeordynamic object). Whatever clean air flow that there is will become turbulent once it is past the smooth part of the bike that is moving through it.

So from the above, the air behind the nose fairing, if it were blocked would have a higher (slow moving static) pressure than the air moving past the nose fairing., there wouldnt be a suction effect, it would be the opposite, however watch a jet taking off in the drizzle and you see wing tip vortices, this is the higher static pressure spilling over the top of the wing and becoming turbulent when it meets the lower dynamic pressure (hence the vertical winglets on the ends of a lot of jet wings, even the humble old 737 has 'em, to reduce this turbulence and reduce drag, increasing efficincy and saving fuel, whilst still charging you more for your ticket)

I digress..ahem.. this turbulence is what is happening when the lower pressure air is meeting the higher pressure air from behind the fairing, so there never is an overpressure as such.

right you can wake up now

[Pablo Pirate]

And that my lord is how we know the world to be bannana shaped!!!

[geo7863]

Originally Posted by Pablo Pirate

And that my lord is how we know the world to be bannana shaped!!!

I have headache now..wish I kept me trap shut..

Its not easy going from pongo to flyboy you know!!

[Pablo Pirate]

Tell me again how we can navigate the earth using a sheeps bladder?
Keep up the good work mate.

[AdrianK]

Originally Posted by geo7863

er if you really want me to?

This is what I learnt when studying for my pilots license.

Introduce an object into a body of moving air (or move that body through the air) and things happen to the air molecules. For some reason, unkown to me 'cos I is thick, when the air molecules are parted by the object they will meet at the same time when past that object.

I will give the example of an aircraft wing, or the spoiler on a F1 car (It snt really a spoiler as that is designed to 'spoil' the air flow and induce drag, the F1 cars have an upside down wing or aerofoil)

The upper surface of a wing (lower for F1) is usually more curved than the lower surface (upper for F1). when the air molecules meet the wing they part and go over and under the wing, when they get to the trailing edge of the wing they will get there at the same time (thats the bit I dont understand why).

The air molecules running over the top of the wing have a further distance to 'run' before they reach the trailing edge so to meet the lower wing air at the same time they move faster. This gives a lower (dynamic) pressure.

The air molecules under the wing, have a lesser distance to travel so are moving slower and have a higher (static) pressure. This is what gives the wing lift, and in formula 1 its this 'lift' upside down which presses the car against the tarmac.

This is also by the way how a carburettor venturi works, faster air running through the squeezed space gives a lower pressure, lower pressure means that it sucks the air in faster.

And also how carburettor icing works, even on a fairly warm day as lower pressure means lower temperature, which means air that is moist loses its ability to retain that moisture as the air cools, the moisture turns to water which can be cooled below freezing point and thus form ice on the carburettor butterfly valves, this is the main reason why light aircraft crash, carburettor icing, loss of engine power, loss of forward thrust, loss of lift, glide to a good landing point or die!

Now a bike is not a wing, so a lot of the air that the bike is moving through will be 'battered' out of the way and becomes turbulent very rapidly (this is form drag because the bike is not a clean smooth aeordynamic object). Whatever clean air flow that there is will become turbulent once it is past the smooth part of the bike that is moving through it.

So from the above, the air behind the nose fairing, if it were blocked would have a higher (slow moving static) pressure than the air moving past the nose fairing., there wouldnt be a suction effect, it would be the opposite, however watch a jet taking off in the drizzle and you see wing tip vortices, this is the higher static pressure spilling over the top of the wing and becoming turbulent when it meets the lower dynamic pressure (hence the vertical winglets on the ends of a lot of jet wings, even the humble old 737 has 'em, to reduce this turbulence and reduce drag, increasing efficincy and saving fuel, whilst still charging you more for your ticket)

I digress..ahem.. this turbulence is what is happening when the lower pressure air is meeting the higher pressure air from behind the fairing, so there never is an overpressure as such.

right you can wake up now

Thanks Geo...I think I can see what you're saying. It's a bit late in the evening and I was up all last night!

The terms 'dynamic pressure' and 'static pressure' are a bit confusing. The top and bottom of the wing both experience 'dynamic pressure' but (as you said) less on the top than the bottom.
An airspeed indicator works by using the difference between dynamic pressure and static pressure...the dynamic pressure (proportional to the square of the speed) is always higher than the static , except when the aircraft is stationary ....and then they're obviously equal and you've got 'nothing on the clock but the maker's name'
The aerofoil theory applies to aerofoil or semi-aerofoil shapes but as you said not every bit of a bike is aerofoil shaped. What happens at the front of a 900SS ? Dunno!! Anyone got a wind tunnel?
ATB
A.
P.S Re-winglets the theory is as you describe but interestingly on some if not all Boeings you can actually go without them and there is no performance penalty...some manufacturers have them and some don't..which makes me wonder if they are all they're cracked up to be. Zzzzz! Sorry chaps, now we can all go back to sleep!

[geo7863]

Adrian K... you bloomin tease you knew all along!!

Yes the terms dynamic and static pressure are confusing, especially when the dynamic and static feeds for the airspeed indicator are, on the Zlin's that I fly both on the same pitot head, or on some aircraft the dynamic feed is on the pitot and the static on the side of the aircraft fuselage, both in areas which are experiencing airflow...

Now, sorry Mark back to oil coolers

[markm]

Originally Posted by geo7863

Adrian K... you bloomin tease you knew all along!!

Yes the terms dynamic and static pressure are confusing, especially when the dynamic and static feeds for the airspeed indicator are, on the Zlin's that I fly both on the same pitot head, or on some aircraft the dynamic feed is on the pitot and the static on the side of the aircraft fuselage, both in areas which are experiencing airflow...

Now, sorry Mark back to oil coolers

Gadzooks! what 'av i started??

George and Adrian (resident aerodynamic experts).. so... would i be correct in thinking that all the air that enters the 2 intakes once inside the nose of the fairing becomes a swirling bumbling mess? Theres enough obstructions there (wiring, connectors, steering head stem, yokes etc etc).....

right... i'm still on a tangent thanks to this forum.. in mooching around on the net yesterday (thanks Steve - Mr. R) and through one link or the other have found something i might give a go: found an oil cooler by Setrab 641
measures 8" wide by 2" deep and 1 1/4" thick which will fit in the space at the nose of the fairing behind the 2 intakes. I've also found a clever little device called a thermostat 641-10 Thermostat Twins which would open up at 80 deg C and allow oil to go to my hypothetical aditional oil cooler... failing that theres a manual version bypass valve. I've also found a thermostat at BSR Aerotek for £12.50 so could be something worth experimenting with..
All interesting stuff!
I need to know now whats the optimum oil temp range on our ducati's?
Anyone have a clue?
regards
Mark

[AdrianK]

Originally Posted by markm

Gadzooks! what 'av i started??

George and Adrian (resident aerodynamic experts).. so... would i be correct in thinking that all the air that enters the 2 intakes once inside the nose of the fairing becomes a swirling bumbling mess? Theres enough obstructions there (wiring, connectors, steering head stem, yokes etc etc).....

right... i'm still on a tangent thanks to this forum.. in mooching around on the net yesterday (thanks Steve - Mr. R) and through one link or the other have found something i might give a go: found an oil cooler by Setrab 641
measures 8" wide by 2" deep and 1 1/4" thick which will fit in the space at the nose of the fairing behind the 2 intakes. I've also found a clever little device called a thermostat 641-10 Thermostat Twins which would open up at 80 deg C and allow oil to go to my hypothetical aditional oil cooler... failing that theres a manual version bypass valve. I've also found a thermostat at BSR Aerotek for £12.50 so could be something worth experimenting with..
All interesting stuff!
I need to know now whats the optimum oil temp range on our ducati's?
Anyone have a clue?
regards
Mark

Hi Mark,
I'd never claim to be an aerodynamics expert.....the maths is far too complicated!! However I do regularly depend on the theory working!

Re the oil cooler idea I found a US website where the guy had done exactly what you propose i.e mounting the cooler inside the nose fairing. I've just tried to go back to the website but for some reason the pictures wouldn't download. The link is as follows..... Miller Oil Cooler Kit
You can e-mail the guy via http://arch.texas.net for more information. Re the cooler and plumbing I found Pete at NBM Woolford at Silverstone to be very helpful. He can provide all the kit and useful advice. www.nbmwoolford.co.uk

George,
I really wasn't teasing! I find the subject interesting and there's always more to learn about the 'black art' of aerodynamics!!
Flying a Zlin....lucky chap! A bit like an aerial Ducati !!
Safe flying
ATB
Adrian

[Kenoir]

Originally Posted by Pablo Pirate

And that my lord is how we know the world to be bannana shaped!!!

This new learning fascinates me!