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 Post subject: Re: Locost aerodynamics
PostPosted: September 11, 2014, 11:51 pm 
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962P, i agree with your point of view, your findings are what you personally found, and as you say there are many variations of locost/lotus/lola/lalo all with slight variations but large enough to cause significant changes in the aero and on a dirty car with lots of disrupted flow, these variations become amplified.

there is one thing however that you may wish to turn your attention to, and that is "we are all plagued with a blizzard hot or cold hitting us in the ear" is there a perfectly repeteable formula for how far in front of your head should the windshield be to limit this.

with regard to the cockpit area and turbulance, i have on my car small round luvered vents in the side as can be seen in a side view which introduces air into the footwells, have you thought of this in a sim?

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 Post subject: Re: Locost aerodynamics
PostPosted: September 12, 2014, 8:14 am 
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I have not done any work on the 7's so I really have not looked into different things and the effects they have on the 7's .
the couple of things I have looked at were just to satisfy my own curiosity .
because what I do is for motor sports we do have to deal with driver comfort .
getting the aero on a car as we all know is very important but it's all for not if the driver is getting fatigued .
there are things like opening the body of the car for ducting cool air to the drivers that often have very little effect on the over all aero performance of a car .
in formula cars we will cut opening in the nose panels to duct cool air to the drivers were on sports racers we will do the same but on a sports racer the opening will end up in different places . this has to do if it's for open cockpit cars or closed cockpit cars .

John with your car as the aero is not all that good my guess is the placement of your cockpit ducts are fine . the fenders by them selfs are creating more drag then cockpit ducting ever would .
again it comes right around to if your getting over heated you will not be able to drive the as hard as you would need to making any aerodynamics kind of pointless .


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 Post subject: Re: Locost aerodynamics
PostPosted: November 7, 2014, 4:17 pm 
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I read through all the pages and have to say you all gave me some great ideas. Due to my unique design (read AWD subaru turbo build) and my wife's demand that the car had a hard roof (T top with removable gull wing doors) I could use some of your opinions.

Attached below are some side profiles of my car. I'm aiming for down force in the rear as a majority of the weight is upfront. The plan is full belly pan the length of the car ending in a large diffuser, with rear side/top intakes for cooling the rear diff and rear mounted radiator. The whole underside will be sealed and i plan to have lots of vents to get the air out of the engine bay. I plan to have full/partial side fairings to cover the exhaust and cooling tubes that run along the side and decrease the aero drag. The primary point t of the car is track day and autocross with some street legal fun.

If you have any suggestions let me know. My plan is to make the body out of fiberglass molds as I've done lots of fiberglass in in my life.
Cheers


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 Post subject: Re: Locost aerodynamics
PostPosted: November 7, 2014, 8:07 pm 
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It doesn't look like you will be able to see what is in front of you with that seating position.

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 Post subject: Re: Locost aerodynamics
PostPosted: November 7, 2014, 9:53 pm 
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I think you are going to have to move as much equipment to the rear of the car as possible (Batter, ECU, Fuel, Radiator?, etc) to try and get decent weight distribution. At the moment it looks like hard braking will result in the rear end lifting off the floor.

It is a shame you could not have the engine at the back and still have 4 wheel drive. It would have soooo much traction getting off the line with all the weight in the rear. No idea how you could do it without having 1 forward gear and 5 or 6 reverse gears though.

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 Post subject: Re: Locost aerodynamics
PostPosted: November 7, 2014, 10:59 pm 
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There's a reverse cut ring and pinion for the transaxle and then you need to find a reverse cut ring and pinion for the R160 or another front diff. That might work better, but this car is already well under way.

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 Post subject: Re: Locost aerodynamics
PostPosted: November 8, 2014, 9:36 am 
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I hate to say it but I tend to agree with the statements others are saying about the design of the chassis .
as it is now the nose weight is way to much . the car is going to under steer like a total pig !
with the front axel to engine over hang to wheel base I'm thinking you can not get enough weight on the rear to balance out the chassis .

seating is also not the best ! your neck is going to kill you after a very short time in the car .
in general seats have a lay back they are designed to be used at . once you mount the seat out side of the lay back they are for they tend to become very uncomfortable .
your best bet is to design your own seat to work with the formula car type of lay back your looking for .
it's not going to do a dam thing for line of sight into a corner to see the apex .


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 Post subject: Re: Locost aerodynamics
PostPosted: November 8, 2014, 11:07 am 
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His seat is not going to stay like that he mentioned in another comment/thread that it is too big for the seat space so it is just sitting on top at the moment and fell back.

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 Post subject: Re: Locost aerodynamics
PostPosted: November 8, 2014, 11:52 am 
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The plan is to have every auxiliary component mounted in the rear, such as radiator, fuel, ecu, controllers, me, a large rear wing and full underbody diffuser. This car will be a bit nose heavy which I am working to counteract with suspension and aerodynamics. I know it's not ideal but it's what I have.

Next car will be better. Either standard v8 rwd build or rear mounter motor build.

The seat will be hand made as this one does not fit. It will be more upright and able to see over the intercooler.
Here are some mock ups I made to show the roll bar height and windshield height if I go full cockpit.


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 Post subject: Re: Locost aerodynamics
PostPosted: November 8, 2014, 1:10 pm 
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Let's try to keep most of the discussion about this car in John's build thread unless it's actual aero stuff...
http://www.locostusa.com/forums/viewtopic.php?f=35&t=16857

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 Post subject: Re: Locost aerodynamics
PostPosted: November 8, 2014, 1:18 pm 
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Horizenjob
Sorry about that. I'm just trying to get you experts to aid in my aerodynamic design. I can build most anything but coming up with pretty body lines or drawing is just out of my realm.


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 Post subject: Re: Locost aerodynamics
PostPosted: November 8, 2014, 1:33 pm 
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I would think that between auxiliaries in the rear, spring rate and sway bar selection, and maybe even a bit of reverse tire stagger, you can probably get the handling to balance out ok.

I would be careful with the downforce balance though, as a rear aero bias will only magnify any understeer tendencies. I believe that the typical idealized starting point aero downforce distribution is just slightly more rearward biased than the weight distribution, such that it inherently develops a little more high speed understeer. However, there are a lot of assumptions made with that which may or may not fully apply to any particular car.

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 Post subject: Re: Locost aerodynamics
PostPosted: November 8, 2014, 4:23 pm 
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A rear aero solution will be a slippery slope when heading into a turn. The rear end that stuck great at high speed will quickly lose grip as the car slows and starts to turn in, which can easily allow rear wheel lock-up. I'm not sure if it'll spin or understeer like crazy.

Separately, are there any sketches or CAD drawings of the final product? I can't figure out how it can be styled without the front of the car being the tallest part. The "Exocet" kit has the same issue with a drive train that packages better but even then its styling is, um, challanged.

Regardless, I'd keep the radiator up front where airflow is a known quantity.

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 Post subject: Re: Locost aerodynamics
PostPosted: November 8, 2014, 8:57 pm 
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your asking allot if your trying to use any aero to balance out the chassis .
the 1st thing to get a good car is balance , then mechanical grip then you go for aero .
just for fun I run a couple of simulations with a car design like your . I could only guess on many things as I do not know the balance of the car as it sits nor things like the wheel base and track but takeing a guess from the wheel size your showing it's not good at all .
the size of the rear wing would have to be huge and then to get the needed rear down force you would have to be at speeds of 80 MPH and over .
a rear diffuser because of the size it would need to be for the amount of sqr inches of the under chassis you have to work with along with all the other factors would have to stick out about 2 plus feet past the rear frame rails if you were looking for a rear diffuser that really works .

one help would be to go with a different intercooler . the top mount does add unneeded height .
but were to move it ? to the front that just adds unwanted nose weight .
side mount ?
that too has some problems .
what type of body are you thinking of ?
open wheel design or full fenders ?

you have a pretty tuff design challenge in getting aero out of a box shape.


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 Post subject: Re: Locost aerodynamics
PostPosted: November 8, 2014, 10:23 pm 
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maybe something like an audi tt.

and you could fill the roll bar and rear chassis with lead.

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