Okrasa Special

[steve wright]

yes what I find amazing is Jefferey has a decade of experience with this under his belt already! And being tutored by some of the best in the world. Not a bad way to start a career.

[smallspeed]

Some big decisions to be made about how to vent the hot air from the oil cooler. The 550 and RSK simply exited it over the front axle, but that's pushing air under the car and creating lift which isn't good. Given the original designer (David Small) had gone to the lengths he did in creating a completely flat floor, it seems right we do something better than this. Other manufacturers were also more sophisticated, venting it through openings in the side of the wings (Aston Project cars and racing Ferrari's in particular). The other idea being bounced around is to vent it between the front valance and bonnet onto the windscreen but both require ducting so we need to figure this one out soon. Thoughts welcome on this one if anyone has experience..

No experience as such regarding cars of this age, but certainly drawing air from the lower part of the nose (or in-front of the front axle using naca ducts or similar) and ducting it up and over the car is far better from a lift point of view.. In my opinion it would be a pity to disrupt the lovely clean lines of the car with lots of vents and things though, so possibly a slight up-turn at the rear of the "bonnet" and some ducting from the rear of the cooler to push the air out from underneath and over the screen would be neatest?

Not sure what you're planning in terms of air-intake to the engine, but might be a nice nod to more modern thinking (although probably not massively beneficial on this car) to make sure you're not directing hot air from the cooler straight into the engine
For example:
If you're drawing air to the intake(s) from the sides (like a boxster) or top of the rear wings (like the little snorkels on a 250lm?) then direct the air from the cooler over the middle of the roof
If you're drawing air to the intake(s) from the middle of the rear screen / rear deck lid, then split the air from the cooler and send it over the a posts/side windows and away over the top of the rear wings
etc., etc...

Sorry, I'm a bit out of touch with the project so not 100% sure what some of the finer details are, but hope some of this makes sense or leads to useful conversation

[Pandora]

Looking great, Steve,

I'd think a slight kick up at the rear edge of the bonnet with the hot air flowing up the underside of the panel and out in front of the windscreen would be neatest. yes, the windscreen wipers will obstruct 'flow' a bit, but not too much, and this would/ could nicely mirror the detail at the leading edge of the rear clamshell at the base of the rear window.

Given the chassis design, it should be simple enough to duct up over the footwell, and as heat rises, fairly efficient?

Al

[Pandora]

Quick scribble:
Okrasa cooling

Al

[steve wright]

Thanks for the input guys (and lovely sketch Al). Yes seems like the most elegant solution as cooler will be in the nose: there will be no oil cooler in the fan housing so the engine bay will remain relatively cool. We've had good experience with this set up on the 356 which only has the cooler in the front wing. That engine gets a beating and yet gets above 85 Celsius. I was initiatory thinking of a second skin to duct the air but have decided to go with 100mm brown hoses; very period and a lot less work to construct. They will run either side of the bonnet so will be virtually unnoticeable insitu. The engine gets air from inverted quarter windows (opening in rather than out) and then the hot air exits under the car via a lovely backwards facing vent installed by the original owner to minimise the impact on the completely flat floor. At the rear we have plenty of openings in the rear of the Kamm tail to exit air from the rear wheel arches. Little Pete (as opppsoed to Big Pete from Cogbox) is going to help with measuring air pressure and lift once we get the car up and running with simply air pressure sensors so we can get a proper fix on what is going on, although we will have to do the whole 'stick woollen tufts on it and drive it up the motorway' to do the preriod correct stuff

[Pandora]

Ironically, I was offered a wind tunnel for free just last week. (Really! Another part of the Uni was throwing it out)

Sadly, we didn't have the space to house it, so we had to say no.

Wool tufts down the A3 it is then!

Al

[steve wright]

Al I have space or know people who would love to get their hands on one. If still available can you pm me? Thanks

[neilbardsley]

Ironically, I was offered a wind tunnel for free just last week. (Really! Another part of the Uni was throwing it out)
Al

That isn't something you hear everyday!

[Pandora]

LOL, yeah, not an everyday occurrence, even in a university!

Still, it got me to thinking about the period style options for air inlets, borrowing from others of the period - Ferrari GTO, 250 Coupe speciale, My beloved 'Pandora', the Alexander Turner, Elans etc, so I made up a quick underlay and scribbled a few options - of course the necessary air flow will dictate size, but quite a pleasant way to send a few moments doing a 'brain dump' of ideas, if only to provke thoughts for Steve and the guys at M&Y

I'm a bit sad it doesn't have a radiator - it really narrows the need to give the car a 'face'!

Other boring things like indicators, number plates etc also serve to fill in the gaps, but you get the idea.

Al

IMG_20171207_200511[1] by Alastair Brown, on Flickr

IMG_20171207_200500[1] by Alastair Brown, on Flickr

IMG_20171207_200447[1] by Alastair Brown, on Flickr

IMG_20171207_200431[1] by Alastair Brown, on Flickr

IMG_20171207_200419[1] by Alastair Brown, on Flickr

IMG_20171207_200407[1] by Alastair Brown, on Flickr

[smallspeed]

#1 for me - love the frog look!

[neilbardsley]

If you put a lip on the bottom of the front (like a splitter) is that significant in preventing the air getting under the car?


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[steve wright]

Thanks Al. Those are great and really useful to enable pondering of ideas and options. The cooler is 190mm x 300mm, and also needs to include two 92mm diameter holes for brake ducting (one either side)so quite a bit larger than the aperture you envisaged. I was think Ferrari 250LM style, about 100mm high.... but it would be great to see other options

Neil a lip wasn't in practice then unfortunately - probably 5 years too soon...

We will make sure the flat floor is extended as far and wide as possible and make up wheel spats front and rear though

[Pandora]

These things are best sketched out on the panel in styling tape, but sketches do have a purpose as well, if just to promote discussion. To keep the lines clean and simple I'd avoid too many holes & vents (I know you like them ) so if you wanted a central grille rather then the very early 60's style 'shark nose' treatment, I'd take the brake cooling from within a bigger vent, rather than having separate inlets at the side.

It's a controversial statement, but I think the GTO is far uglier than the SWB as it is littered with vents which break up the form. Conversely, the 911 has very clean surfaces.

Integrating additional lighting and smaller ducts together helps bring cohesion to the design

Happy to scribble a few more ideas if it helps,

al

[steve wright]

yes planned to take brake cooling from within the nose vent - great minds think alike

happy to see some more ideas - I don't want to put more grills and ducts than are absolutely necessary, but we do need to vent hot air and I don't want it going under the car if I can help it. all ideas welcome

[Pandora]

Will dig out my crayons next week.

Al