#241
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gee dub |
#242
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Aerodynamics of a bug
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I did think about cutting the hood but as you have said cutting it would not be something I would want to do .The bumper is from a Rover 400,It has been modified a bit but not heavily.
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gee dub |
#243
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Aerodynamics of a bug
I have been pretty active recently on this site as I have spent the past three or four days on the sofa with the sodding Flu. Anyway this is an idea I have had for a rear bumper/spoiler.It would work by releasing the pressure from the rear of the bug where the cars original design seems to act like a parachute.ie wings,apron,engine lid.The holes/vents in the wings etc would escape through vents and get channelled into the rear bumper at an angle to produce down force.In addition to this, the top of the bumper would be angled to produce more down force.It would be built to fit close to the body to eliminate what seems to also be the parachute shape of the standard bumper.Also the bottom center section could include veins.I have seen engine lids with holes behind the number plate this could be angled to produce more directional airflow.I am not sure of how it would effect the rear of the car but as I see it, it could possibly
1. create and add down force 2. release pressure from the rear wings,apron,engine lid. 3 create some rear end stability at high speed. I have got an old porsche style body kit rear bumper that I was intending to use as a starting point . All input welcome Hope it turns out better than my sketches .
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gee dub |
#244
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Hey Graham,
I like your sketches! The vents in the rear fenders and apron is something that Remmele has done to his cars for a long time also and I think the reasoning behind that is strong. It will surely help some, same as it would on the rear of the front fenders. Not so sure there would be downforce as such on a rear closed bumper though as turbulence behind the car is probably very high. I do agree they act as parachutes otherwise. For that reason I filled mine up with expanding foam (PUR) Walter |
#245
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Couple of aero basics for you:
To get downforce the rear exits would have to be channelled to point upwards, the downforce is a result of a reaction force. The air over the top of the car would be detached from the surface way before the engine cover, typically at the top part of the rear window. Downforce is mostly a result of STATIC pressure and the difference of this between top and bottom surfaces of a body. Target is to get higher pressure at the top surface which will result in overall DOWNforce. According to Bernoulli's equation: faster fluid flow results in lower static pressure. Using this, you want to get the air under the car flowing as fast as possible to get the static pressure as low as possible giving any increase in pressure over the body a chance to create the downforce.
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http://www.ricola.co.uk |
#246
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Graham, well done so far, a very nice side step to the usual copy cat builds, but do you want all that venting on a road car? i have exactly that type of venting on my race car, but its not subtle. with a water cooled road car, why not work towards a diffusor and flat bottom it up to the bumper line? this was a factor in my water cooled engine choice, together with diminishing DB control thresholds at the races, i'm now 3/4 db quieter over aircooled with water cooling alone. you will need to move the lower shock mounts to make a worthwhile flat bottom workable, and the exhaust needs attention with any engine to get it out of the way. Just my view, but i think a road car, or a race car come to that, should be as understated as possible, its easy to get carried away and the KIS rule always applies. but well done so far anyway.
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#247
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i'm in work next week so give me a call.
this is the sort of thing you wnat under the car
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my race car build galleryhttp://www.flickr.com/photos/1406263...7602662665607/ my web site www.rnjmotorsport.co.uk |
#248
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Of all the aero. tricks I've tried so far, venting the fenders made the most difference I could feel right away. Took the car out on the highway the next day and it felt much more planted to the road than before. I used a punch and flare tool on mine to make the holes. The turbulent air of the spinning wheels causes the fenders to act like wings and give the car some 'lift' at speed. If you look at new(er) cars they have a fender liner to minimize this distance between the tires and the inside of the wheel well.
Made a cheapo. roof spoiler out of garden edging recently. Just couldn't bring myself to spend $200 on a little piece of carbon fiber strip. Seems to help, car scoots off the line a hair quicker, could be my imagination too as I'm not being very scientific here but it definitely doesn't feel likes it's creating any drag.
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'66 Bus(11-window, CLK rims, disk brakes, IRS, bags, hydr. clutch, Super-1600 w/injection) |
#249
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I just found this interesting youtube vid & facebook item and thought I had to share it here.
See: Youtube video VW bug in a wind tunnel And there was a poll on the face book page, see the top red box. The answer is in the bottom red box: (click on it to get to the entire facebook page, I couldn't link directly to this item) The beetle has 6% less drag when going backward. I think it's because of attached flow staying attached to the rear window, which creates drag. Going backwards, there's nothing to attach to after the windscreen point. So the airflow can form itself like a teardrop.
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Greetings! ________Gerrelt ________homepage:gerrelt.nl __________________________________ Last edited by Gerrelt; February 9th 2013 at 15:51. |
#250
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Thats very interesting and sad at the same time. Shows us also here's a lot to gain with aero improvements.
We're probably on the right path Gerrelt |
#251
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Yep!!
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Greetings! ________Gerrelt ________homepage:gerrelt.nl __________________________________ |
#252
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Here is my underbody at its present stage. the rear ARB need moving to finalize the airflow, and is next for the chop saw, its going inside a tube running through the cars rear wheel boxes, bugs are hard work aero wise, the exhaust is particularly difficult to package away from everything in order to fit streamlining panels that wont be ripped off in the first race, my car already bottoms on the spring plate bolt heads and its not low enough yet, ideally the torsion tube needs raising and the horns chopping out. |
#253
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Aerodynamics of a bug
My car has been hibernating whilst I am waiting to finish a large building project before work begins again on it. I am still looking at the builds here and seeing peoples ideas and views.
Spanner, it's interesting that you mention raising the torsion tube and chopping out the frame horns .Thats got me thinking. Part of the next stage of mods on my car will involve cutting the torsion tube in the centre and replacing the frame horns to aid the g50 gearbox fitment.Do you think raising the torsion tube or removing it completely may be worth considering whilst I am at it ???? What are peoples views/ideas on the best possible rear end set up to accommodate the g50 minus a torsion tube.I will be using one of Alex's uniball set up's.I am now thinking of a gearbox cradle/frame horn combo to tie into the cage and hold the uniball kit at the same time raising the top shock mounts.Here's the car as it is at the moment.[IMG]~original[/IMG]
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gee dub |
#254
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Hi Graham, I would look at Ricolas layout, he made up new horns to suit a G 50, but to answer your question, unless it's a race only car, and running at circuit type ride height, ie, 40mm, raising the t/tube isn't strictly required, what it does is allows the car to run lower with good trailing arm angles for effective launching/traction, on the other hand, a powerful motor needs as straight a driveshaft alignment as you can get, so a gearbox raise is required in any case, removing the horns completely requires either a very strong mid mounted yoke set up, noisey for a road car, or a Porsche type rear engine support bar with lots of body/apron strengthening to hold the weight of motor, trans, and control the dynamics of driving forces on the supports, my racer uses a mid mount yoke, as I originally planned to loose The horns, I even tested with the end bolts removed with no problems, but they got a reprieve for packaging and mounting other stuff off them reasons, race only cars are easy, less compromises than a road car has, more for you to consider.
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#255
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Aint that the truth!
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