Davemk1 Posted December 19, 2007 Share Posted December 19, 2007 I'm thinking that I might want to make some changes to my Birkin to help in the aerodynamics dept. I was thinking a front splitter and a rear diffuser. Designing and making the splitter seems pretty simple. I'm less confident about the rear diffuser design. Anyone out there in Seven-ville know anything about this or know of anything available? Thanks, Dave Link to comment Share on other sites More sharing options...
Boxologist Posted December 19, 2007 Share Posted December 19, 2007 MOG out of Europe has a diffuser. get subscribed to teh d/e mod yahoo group if ur not. SCCA rules have limitations to what we can do for Solo compliance. There some nice discussions on the topic if u search. Link to comment Share on other sites More sharing options...
Mike Rohaley Posted December 19, 2007 Share Posted December 19, 2007 Is your main goal to increase downforce or to decrease drag? Depending on your goal I may have some usefull stuff that I have developed. Also, I found a video a while ago that followed the Caterham SV through wind tunnel testing that explained many of the difficulties of streamlining while maintaining the character of the car. They even documented a much unloved front wing design and how well it fared in testing. Link to comment Share on other sites More sharing options...
Mike Rohaley Posted December 19, 2007 Share Posted December 19, 2007 Sorry, I couldn't find the video on YouTube. I believe that it was a BBC documentary on the development of the SV and the time spent with Reynard developing the "next" Caterham (before they closed up shop). If anyone has it occupying hard drive space it would be greatly appreciated if you could post it here. Link to comment Share on other sites More sharing options...
Kitcat Posted December 19, 2007 Share Posted December 19, 2007 Remove the windshield. Link to comment Share on other sites More sharing options...
BusaLoco Posted December 19, 2007 Share Posted December 19, 2007 Fluke Motorsports UK multi-plane contoured diffuser £579.00 price excludes UK VAT (17.5% where applicable) http://www.usa7s.com/aspnetforum/upload/337112828_182_1.jpg http://www.usa7s.com/aspnetforum/upload/1986955224_182_2.jpg PRODUCT INFORMATION Two-tier contoured, channeled diffuser in carbon-fibre. Designed for after-market replacement on Westfields and similar these diffusers extend from the rear bulkhead. This has a three-fold effect * reduced drag from the rear fuel tank area which typically acts as a parachute without underfloor covering * down force creation from low pressure area created by aerodynamic profile of the diffuser - increased further as the channels aid the airflow keeping it attached to the contour of the diffuser * cleanliness! - covering the underside rear quarter of the car as such helps to keep the dust, mud and much from coating your suspension, diff and fuel tank! Fitting the diffuser will require a small slot cut out at the back of the bodywork (~0.75" x 18" ) to accommodate the second tier. The diffusers are typically attached at the front by extending the floor pan out an inch or two and 'hooking' the front of the diffuser over this lip. The rear can be attached with tie rods or quick release Dzus clips (not supplied). It is worth bearing in mind that as this diffusers pulls down at speed it is worth spending time ensuring that it is mounted correctly and firmly. When ordering, it is useful if you can pre-measure the length you require (the measurement from your bulkhead to the end of the diffuser) as reduction in this length from the default may reduce the postage cost. Link to comment Share on other sites More sharing options...
Mike Rohaley Posted December 19, 2007 Share Posted December 19, 2007 The video is called Caterham- Suvival of the Fastest produced by BBC4. It provides great insight into the hurdles involved in getting our brick walls to slip through the air. Link to comment Share on other sites More sharing options...
RGTorque Posted December 19, 2007 Share Posted December 19, 2007 downloading it now! http://domestic1.sjc.ox.ac.uk/~jn/caterham-bbc4-documentary.mpg Link to comment Share on other sites More sharing options...
Davemk1 Posted December 19, 2007 Author Share Posted December 19, 2007 Is your main goal to increase downforce or to decrease drag? Depending on your goal I may have some usefull stuff that I have developed. Also, I found a video a while ago that followed the Caterham SV through wind tunnel testing that explained many of the difficulties of streamlining while maintaining the character of the car. They even documented a much unloved front wing design and how well it fared in testing. I'm looking for added performance in autocross. Since most autocross speeds are pretty low in the big scheme of things I'm not sure how much advantage there is to be had. I guess my main goal would be to add downforce. I think the easiest way to reduce overall drag is to remove the windshield and that's pretty simple. I'm not sure how it is on other Sevens but on the Birkin the area under and around the rear axle is open and the rear rises at too steep and angle to function as a diffuser. So my rough idea is to make a panel that will fill in the area around the axle as best possible and to make/buy a diffuser for the rear under the tank that doesn't rise as quickly and would better manage the air flow. Thoughts? Dave Link to comment Share on other sites More sharing options...
slngsht Posted December 19, 2007 Share Posted December 19, 2007 For autox, maybe a huge rear wing will accomplish what you need. Something removable. Link to comment Share on other sites More sharing options...
Mike Rohaley Posted December 19, 2007 Share Posted December 19, 2007 The route I went was to reduce drag by making a belly pan for the rear, the benefits of this don't really come into play at autoX speeds though. If you are looking for downforce at lower speeds (below 70) you will need a large and agressive wing (like Mazda suggested) that will definately look odd if it is street driven but will do the job around the cones. Then again, nothing comes for free. With downforce comes drag unless you do something cool like the Chaparal did with an adjustable wing angle of attack. http://www.usa7s.com/aspnetforum/upload/310887855_ZChaparral2F.jpg Link to comment Share on other sites More sharing options...
Ian7 Posted December 19, 2007 Share Posted December 19, 2007 With autocross speeds rarely reaching even average highway speeds, the "downforce" component of these diffusers is laughably small, especially if looked at in a $-to-downforce ratio. To put it in perspective, look at photos of what some of the Formula-SAE guys are running for wings in order to get any measurable downforce at their similar speeds. They are 3 and even 4 element assemblies, massive compared to the chassis. The many auto-x suggestions above are spot-on - - delete the windshield, vent the clamshells (if allowed), if not, trim the edges to whatever extent you can get away with, pay for a professional chassis set-up session, and buy the best stickiest tires available... have fun Link to comment Share on other sites More sharing options...
Boxologist Posted December 19, 2007 Share Posted December 19, 2007 unfortunately big wings are banned once u find ur self at a national event. conversation on CCC http://www.californiacaterhamclub.com/chat/showthread.php?t=894 Link to comment Share on other sites More sharing options...
Davemk1 Posted December 19, 2007 Author Share Posted December 19, 2007 I agree that hoping for any real downforce is silly. I realize I'm splitting hairs here with the wording but I can picture reducing lift a bit and making the car a bit more slippery with the removal of the windshield, a front splitter under the nose-cone, a tray under the rear axle and a diffuser. Seems like those things could add up to make a small difference overall. Thoughts? Dave Link to comment Share on other sites More sharing options...
Boxologist Posted December 19, 2007 Share Posted December 19, 2007 i big question i will eventually lookm into is whats legal for the underbody. (how much) can i drop sidesills and try to get some down force that way. an integated set of panels from just behind the engine to the rear diffuser will put the down force where u want it. i liek most of what was done with the CSR aerotreatments as they will be legal. Link to comment Share on other sites More sharing options...
ayseven Posted December 21, 2007 Share Posted December 21, 2007 accidental post Link to comment Share on other sites More sharing options...
Mandurath Posted December 21, 2007 Share Posted December 21, 2007 Better read the rules really carefully first (assuming you can stay awake through the whole thing). Or you will find your car placed in A-Mod where somewhere underneath the wing is a car. Link to comment Share on other sites More sharing options...
HPC Posted December 22, 2007 Share Posted December 22, 2007 The biggest problem with Sevens at speeds where aerodynamic effects come into play is uplift at the front axle - apart from the aerodynamic drag obviously. So I would think a rear diffusor is somewhat counterproductive and creating downforce at the front is much more important. Link to comment Share on other sites More sharing options...
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