New race car aero development

[Brookst]

Hi everyone,
Firstly I want to say hello, I have been a long time reader of the forum but I am currently building a new race car and I would very much appreciate your advice on the aero as it's a important part of the car. A bit of background first on the car it's a GP Midget for those who don't know that is a UK oval racing series on tarmac circuits of varying lengths. The rules are VERY open in terms of chassis, aero, suspension and essentially everything. My current car runs a ford x flow with approx 160 bhp. Now the current car is built round some else's old GP midget chassis that had essentially no bodywork/wings at all and that's fairly common in the class but we wanted to introduce some aero mainly because the cornering speed of most of the cars are pretty poor and I feel aero is one area to improve this. The car is yet to be completed but I have (hopefully) included a link to some pics. The car should be complete this month and be raced at the next meeting. The "plan" is to use this chassis as a test bed this season and build a second chassis based on a single seater Mygale/VD etc to race next year. There are in built problems with the current chassis that would mean as a long term project it's not a good base but it's all we could get hold of at the time. The main issues are one of weight, it's far too heavy, the suspension is pretty outdated and I'm not keen on the chassis layout either but it's what we had as I said and it should serve for what we want this year.
Some additional info for you the car runs on 9x13x20 Avon crossply slicks at the front and 10x13x20 same at the back. The weight of the car will be approximately 540 kg wet. As i mentioned the circuit sizes vary enormously on some you may only be reaching max speeds of 50 to 60mph others around 100. So we are not talking high max speeds here. I'm not sure the pics show it clearly but we have opted to trial a "blown diffusor" we purchased the old minardi PS01B blown diffusor off eBay and worked that into our exhaust system and diffusor. I'm aware of the Off throttle issues with this design and there will certainly not be any budget for fancy ECU programs to get around the issue but it should be interesting to trial the part on track. I would really appreciate anyone's advice on the this car, what may be worth trying out or modifying. I will aim to update the tread after each practice session or race and tell everyone about what worked and what didn't. Then we can use that to build a better car in the future.
I'm sorry about the long post! Kind regards
Tom
[URL=http://s350.photobucket.com/user/Brooks ... e.jpg.html]

https://imgur.com/gallery/RFq7G

[Brookst]

Hi guys,
I have attached an alternative link due to the problems with photo bucket the new link has more pics of the car and some of other race cars in the class.

https://imgur.com/gallery/RFq7G

[Brookst]

https://imgur.com/gallery/voHpk

Above is a link to some more updated pics, the car is almost done and will be ready for its first race this Saturday at Birmingham wheels raceway. I can't tell you how excited we are to see how the car performs.

It will also be interesting to see how a car which relies on a very different aero package and design in general does against the more typical GP midgets in the class.

I will keep you all posted.

Regards
Tom

[n_anirudh]

Is Maldonado driving that car? (couldnt help noticing the logo on the rear wing)

Good work Tom!

[Brookst]

Haha sadly not the driver of this one is my father. He used to race these when he was some what younger. This will be his first race for about 40 years.

Thanks very much
Tom

[n_anirudh]

Are you planning to take it to any hill climbs?

[Brookst]

We might do yes if we have time but the priority with this car was to try various design features and aero parts and use that information to build a second lighter, better aero, generally better car for next season.

My first group of pics showed some of the other cars in the class, most seem to follow the general design ideas in terms of chassis layout and wing design of F1 Brisca stock cars. I'm personally not a fan of this design when you have such an open rule book so we decided to go more down the single seater circuit car design route.

There are obvious issues with converting one sort of racing car to another and you will never end up with the "perfect" car. But it was our best option at the time. Our base car was a typical GP midget, designed initially to have little in the way of body work other than panels to cover the engine etc and one big wing on the roof.

We have used various single seater body panels to make up the current body (and made a few as well) the aero package is a "guesstimate" and we will have to see over the course of this season what works and what doesn't. It should be really interesting to see how it goes.

If anyone has any suggestions about modifications, things that maybe worth a try they would be very much appreciated.

Regards
Tom

[Vyssion]

If anyone has any suggestions about modifications, things that maybe worth a try they would be very much appreciated.

Hey mate, good on you for getting a race car built - I moved to the UK a couple of years back, but have never heard of the "Midget" series though! Just to give you some context on the comments below, I work in the racing industry as a CFD Aerodynamicist - by no means the next Adrian Newey (yet!), but hopefully they give you a few things to try.

• The front endplates are barely higher than the aerofoil profiles themselves. You may want to try increasing the height of the endplate to be higher above the top surface of the aerofoil itself to better encapsulate the high pressure bubble which forms.

• Endplate below the front wing, again, doesnt extend very close to the ground. Of course this may be a regulations thing, so no worries there, however, you ideally want to increase the strength of the underwing edge vortex to get some more poerformance out of it. I would start by placing a 90° footplate extending from the base of the endplate out towards the wheels - this will aid in strengthening the vortex which forms and give you a greater pressure differential between the top and bottom of your front wing.

• Front wing element angle of attack looks a little shallow - I assume that within the Midget racing formula, most of the "hard limit" on getting it as fast as possible comes down to the engine power you're allowed to work with. I would say that you could probably get away with increasing the 2nd front element's angle of attack more to bring some of the aero balance a little forward and increase overall front downforce at very little "drag limitting top speed"
  cost

• Your rear wing appears to be a single element. Fine, however, the camber and angle of attack on that looks very extreme... I would hazard a guess that that wing is in constant trailing edge separation due to the massive adverse pressure gradient you would have on the suction side. Perhaps consider splitting that into two elements, or revising the aerofoil profile / reducing the angle of attack - that should reduce your drag and give you more performance

• The roll hoop I assume is regulation in its position and size? Regardless, due to the size of it vs. your rear wing,
  there is a substantial amount of blockage that the hoop imparts on the rear wing. You do have the wing very high up (which I assume is to get a "clean" air as possible) however, I would hazard a guess the hoop is influencing the rear wing's performance quite a bit (couple that with the separation I would say is occuring...)

• Rear wing looks a little narrower than you would fit - this may be regulation, but if not, thats a good way to gain a fair amount of aerofoil area (assuming it isnt separated flow!)

• There is a wing below the main rear wing element which I assume is meant to be some sort of a beam wing?
  If that is the case, it is much too high and removed from where the diffuser exit is to have any real effect on increasing the pressure pumping effect of the underbody. It is also quite close to the back cover of the chassis in the middle which may be doing something funky there - plus, there looks to be splits in the gurney flap as well? Finally,
  the gurney flap is quite large to what I am used to seeing. Not crazy large, but usually you want to set your gurney flap to be somewhere in the region of 150% of your boundary layer thickness at the trailing edge of your aerofoil so that you are able to generate a sort of "captured" vortex between the flap and the aerofoil surface that will serve as a way to artificially increase the effective shape of the aerofoil with two alternatingly shed vortices behind the flap.
  The splits will be bleeding air through at the least, which will negate some of the gains that you will be getting from the flap being there

• Cant quite make out much detail in the diffuser, other than you have some sidwards expansion as well as vertical expansion. I assume youre using a flat floor?

• Some of the panel gaps are somewhat large.... Perhaps a little bit of my OCD there... But you may find that whatever internal structures you have will be impeding air flowing through the gaps and out somewhere else. You will however be generating a new boundary layer on each panel which is better for viscous drag, but yeah... probably offset by the other drag you experience

Hopefully some of this is useful in some way to you - great job so far and I do wish you and your Dad luck!! Any questions, feel free to ask

[matt21]

Could you post a link to regulations?
Would be interested in what is allowed aero-wise.

For me the cars look a little bit like Formula Student cars.
Maybe this is worth looking to.