Auto-x Splitter... does it work? - LotusTalk - The Lotus Cars Community
 1Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 47 (permalink) Old 06-24-2013, 07:54 AM Thread Starter
Registered User
 
glagola1's Avatar
 
Join Date: Apr 2012
Posts: 1,181
Auto-x Splitter... does it work?

Well, I'm going to find out. I've been slowly building my 08 for SSM and the only fab I've had to do to date is add roughly 95lbs of ballast. The car is well balanced and easy to drive at this point so I've been thinking of what I could do next.

So I built a splitter. I'll be testing it at the Blytheville double event and I'm dying to know if it does anything or not. Color me excited. I'll be sure to post back here with my impressions.

Here's how I did it:

I got a 4x8 sheet of 3mm Polymetal from a local vender for $48. Here's the sheet bolted to the bottom of the car using the stock holes that are used for the stock belly pan.



Then I used this contraption to draw a line 5" in front of the face of the bumper. The rules allow for 6" but I though 5" would work.



I cut out the shape and then added these little fender extensions with aluminum angle and pop rivets.



There's a perfect hole in the side of the clam that the side marker goes through. I cut the plastic stud off the side marker and melted a hole in the back of it so that it could comfortably sit over the top of a bolt head that holds the little tabs I made. This mount spot adds a good bit of stiffenss to the side of the splitter and running along them bottom of it are two aluminum angles to bolster the stiffness of the projecting face.



The splitter is 2 plies of the Polymetal riveted together with heavy duty 3M double stick tape helping with the lamination. What's really cool is that the edge of the Polymetal is actually sandable so I was able to clean up the edges and smooth the hand cut jigsaw profile.

Here it is all done and painted. It takes 13 bolts to remove it. The best part is that it adds more balast. Just 20 more lbs and I'll be able to run with the hard top off!





Total cost was $120 with 3 rolls of 3M tape being 30 bucks!
glagola1 is offline  
Sponsored Links
Advertisement
 
post #2 of 47 (permalink) Old 06-24-2013, 07:58 AM
Registered User
 
Join Date: Apr 2008
Location: Florida
Posts: 3,637
Looks good , but I've seen horror stories of too much pressure at high speeds cracking it and cracking the clam too. Might want to have some support from the top side attaching elsewhere.
qu1Z is offline  
post #3 of 47 (permalink) Old 06-24-2013, 08:14 AM Thread Starter
Registered User
 
glagola1's Avatar
 
Join Date: Apr 2012
Posts: 1,181
Thanks for looking out. It's not actually attached to the clam except for a the fender well which looks to be well supported. The 08's have 4 bolts that go through to the crash structure. I used those as the most forward mounting locations. I may end up getting some struts to stiffen the leading edge that I would attach to the steel parts up in the front opening... We'll see.
glagola1 is offline  
 
post #4 of 47 (permalink) Old 06-24-2013, 08:16 AM
www.theapexinn.com
 
kestrel74's Avatar
 
Join Date: Jun 2004
Location: Watkins Glen, NY
Posts: 11,682
I used 100 % silicone caulk ( a whole tube ) and "glued" my APR splitter on to the bottom of the clam ( as well as bolting it )....it's been years now, and never a problem. ( and yes, the front clam is still removable ) ( and many many times well over 100 mph )

Elise #2292 (SOLD) / CO / Starshield / Nitron Sport SA / RTDbrace / Uprights machined / Down Low rails / DBA 4000 Wiper Slot Rotors/ V1 / SS lines w/Pagid Black / G-Pan / Odyssey PC680 with RLS Bracket / Difflow 5 Element diffuser / Stebel Nautilus horn
www.theapexinn.com
" I started flying when Sex was safe and Hang Gliding was dangerous "
kestrel74 is offline  
post #5 of 47 (permalink) Old 06-24-2013, 08:34 AM Thread Starter
Registered User
 
glagola1's Avatar
 
Join Date: Apr 2012
Posts: 1,181
I don't plan on seeing speeds over 80mph.

Here's pic of a belly pan from an earlier then 08 Elise. It's missing the 4 holes that go to the crash structure that I'm using so support the load.



See the 4 holes in the spacer blocks here?
glagola1 is offline  
post #6 of 47 (permalink) Old 06-24-2013, 09:27 AM
Less is Better
 
me73's Avatar
 
Join Date: Aug 2011
Location: Issaquah, WA
Posts: 2,339
Are splitters useful at autocross speeds? I wouldn't think a lack of front downforce would be much of an issue at 60mph.
me73 is offline  
post #7 of 47 (permalink) Old 06-24-2013, 09:31 AM
Registered User
 
philethier's Avatar
 
Join Date: Jul 2008
Location: Minnesota
Posts: 2,961
In autocross, I expect the best reason to have a splitter is to take the shock of a cone hit.

Of course the OP here is absolutely correct: Do not attach it to the fiberglass.

Phil Ethier Minnesota USA
1973 Triumph Stag LE22439UBW "uncle jack", Sapphire Blue
2004 Suburban 8.1, Sport Red
2005 Lotus Elise, Bordeaux Red Pearl
2017 Ford Fusion (wife had to stop driving manual due to shoulder problem), Oxford White
2006 Gulf Stream Conquest Super C on Chev Kodiak chassis
http://www.mnautox.com
philethier is offline  
post #8 of 47 (permalink) Old 06-24-2013, 09:49 AM
2006 Exige
 
AZelise's Avatar
 
Join Date: Aug 2006
Location: Arizona
Posts: 672
Garage
Quote:
Originally Posted by me73 View Post
Are splitters useful at autocross speeds? I wouldn't think a lack of front downforce would be much of an issue at 60mph.
This one wins national autocross championships, so there must be something to it. Every little bit helps.

Nice work on the splitter - looks professional.


EDIT: pic too big..
Attached Images
 

Last edited by AZelise; 06-24-2013 at 09:54 AM.
AZelise is online now  
post #9 of 47 (permalink) Old 06-24-2013, 10:41 AM Thread Starter
Registered User
 
glagola1's Avatar
 
Join Date: Apr 2012
Posts: 1,181
Yeah, so part of this build was to see if it even does anything besides looking like it does. I'm not going to change my set up at all and run it. If the car behaves differently with it, I'll know it does something. If it drives the same, I'll share my experience.

Have you ever stuck your hand out a window of a car doing 45 and made a little wing out of it? You'll have noticed that it pushes your hand around. Do the same thing at 60 and it pushes a lot more. Now hold a sheet of plywood out the window.
glagola1 is offline  
post #10 of 47 (permalink) Old 06-24-2013, 12:48 PM
Registered User
 
Cicero's Avatar
 
Join Date: Nov 2010
Location: north carolina
Posts: 183
I made one out of 10mm alumilite about a month ago and fiber glassed the edges still haven't mounted it tho. Yours looks great! I love DIY projects
Cicero is offline  
post #11 of 47 (permalink) Old 06-24-2013, 04:59 PM
Less is Better
 
me73's Avatar
 
Join Date: Aug 2011
Location: Issaquah, WA
Posts: 2,339
Quote:
Originally Posted by AZelise View Post
Every little bit helps.
Not necessarily. If the car isn't experiencing front traction issues without the splitter, the front downforce is already sufficient and all the aero is doing is creating drag and adding weight, which doesn't help. But in autocross, it doesn't do much of either.
me73 is offline  
post #12 of 47 (permalink) Old 06-24-2013, 10:29 PM
Registered User
 
metrocube's Avatar
 
Join Date: Jul 2010
Location: Austin, TX
Posts: 841
Quote:
Originally Posted by glagola1 View Post
Then I used this contraption to draw a line 5" in front of the face of the bumper. The rules allow for 6" but I though 5" would work.
What you may find out pretty soon is that polymetal does not hold up well to abrasion. With 5" of extension, you will scrape the front of the splitter when the front dives under braking. Especially considering that you actually have about 10" of extension from the front edge to your first structural fastener. If you go fast enough, it's going to flex and bend downwards from the air pressure diff.

If you're lucky, it will merely wear the front to a razor's edge. If you're unlucky, the polymetal will crack and split. The latter is what happened to our first one, and the razor's edge is what happened to our second.

Polymetal does look gorgeous and shiny, though!



BTW, there is a maximum splitter length after which you begin to lose downforce. Splitters work by tapping into the high pressure bubble formed at the front of a car, the size of which depends on your speed and on how huge an airdam you have.

For a NASCAR stock car with a solid front air dam, a splitter length of 10cm (4 inches) was the limit before downforce started to drop.

Because the front of our cars is not a solid air dam, the high pressure bubble in front of an Elise/Exige is likely to be smaller than that of a stock car. If you aren't driving at 100mph+, the pressure bubble will be even smaller. So, it may not be a Lotus street vs performance compromise that the stock splitter is only 2". There may actually not be any benefit to running a splitter longer than that on an Exige/Elise with a stock front clam.

I'd love to get time in a wind tunnel.

Last edited by metrocube; 06-24-2013 at 10:39 PM.
metrocube is offline  
post #13 of 47 (permalink) Old 06-25-2013, 05:26 AM Thread Starter
Registered User
 
glagola1's Avatar
 
Join Date: Apr 2012
Posts: 1,181
Hey Metrocube, thanks for the good post. Yeah, it's all an experiment for me. Were you able to notice any difference in vehicle dynamics with the splitter?

I've also just ordered some support struts to attach to the front edge. You guys have made me nervous about flexing.
glagola1 is offline  
post #14 of 47 (permalink) Old 06-26-2013, 01:20 PM
Registered User
 
metrocube's Avatar
 
Join Date: Jul 2010
Location: Austin, TX
Posts: 841
Yeah, but I'm going into sweepers at 100mph. I can't see a splitter having any effect at 40 mph, there's just no aero grip to be had from a splitter at that slow of a speed.

I think the autocross guys who do slow-speed aero right are the guys with the huge double and triple wings on the front and rear. Rear Wing Solo cars: Grassroots Motorsports forum: Grassroots Motorsports Magazine

Last edited by metrocube; 06-26-2013 at 01:32 PM.
metrocube is offline  
post #15 of 47 (permalink) Old 06-26-2013, 01:31 PM
Registered User
 
metrocube's Avatar
 
Join Date: Jul 2010
Location: Austin, TX
Posts: 841
This, by the way, is a fantastic thread for anyone who wants to see someone else's experiments with aero: Vorshlag 2011 Mustang GT 5.0 - auto-x/track build - Page 10 - RoadRaceAutoX
metrocube is offline  
post #16 of 47 (permalink) Old 06-26-2013, 01:34 PM
Registered User
 
doug_porsche's Avatar
 
Join Date: Jun 2008
Location: 38th state
Posts: 2,249
Quote:
Originally Posted by metrocube View Post
Because the front of our cars is not a solid air dam, the high pressure bubble in front of an Elise/Exige is likely to be smaller than that of a stock car. If you aren't driving at 100mph+, the pressure bubble will be even smaller. So, it may not be a Lotus street vs performance compromise that the stock splitter is only 2". There may actually not be any benefit to running a splitter longer than that on an Exige/Elise with a stock front clam.

I'd love to get time in a wind tunnel.
I would agree based on the video I watch weekly, and as close as I can get to having my car in a wind tunnel to test.


I cant prove it, but it seems that most of what I read references around 60mph as the number where aero starts working effectively.

Apexes are a lot like relationships. So tough to get right, so easy to see where they went wrong.

The secret to a long life is ------- not dying.
doug_porsche is offline  
post #17 of 47 (permalink) Old 06-26-2013, 03:19 PM
Registered User
 
Join Date: Mar 2012
Posts: 253
I was relatively convinced that aero for autocross was really fairly pointless on full bodied cars until I listened in on a conversation about it, led by a person who has access to a wind tunnel (and is a very serious autocrosser).

Huh.

That said, I'm kinda with Doug - ~60mph, it starts to matter.

So, 60mph = 88 feet per second.
63mph = 92.4 feet per second.
65mph = 95.3 fps.

10 seconds at 63mph if no-aero allowed only 60, you're 44' ahead.

3mph is pretty generous, really, so let's roughly quarter it - 11' ahead.

11' = ~1 car length.

60+ is very common on Nationals courses.

if he needs to ballast up anyway.....do it. Makes all kinds of sense to me!



Iain
mannix is offline  
post #18 of 47 (permalink) Old 06-26-2013, 03:50 PM
Registered User
 
apk919's Avatar
 
Join Date: Oct 2007
Location: Not Here
Posts: 9,786
A couple of things:

1) Most aero devices create downforce proportional to the square of speed... so if a device created "x" lbs of downforce at 60mph, it would be create about x/4 lbs. at 30mph and 4x lbs. at 120mph. 60mph is an arbitrary number, but unless you're using *really* large surface area aero devices (as Fred does), the amount of downforce is going to be pretty small at 60mph.

2) A splitter creates downforce by "splitting" the air going over/around the nose of your car from the air going under your car. The air hitting the nose of your car creates a local high pressure zone as it is pushed upward or around the car... air going under your car is relatively unchanged. The splitter sits between the local high pressure air above it, and the relatively normal pressure air below... the pressure differential creates downforce, with a very small penalty in drag (relative to canards/diveplanes, spoilers, or wings).
apk919 is offline  
post #19 of 47 (permalink) Old 06-26-2013, 08:03 PM
Registered User
 
Gunpilot's Avatar
 
Join Date: Jun 2012
Location: Enterprise AL
Posts: 4,098
That video is fascinating!
TimWhit likes this.

2012 Evora 2+0 IPS.
2007 Exige mental track toy.
2005 Elise.
1982 Brunette.

"Listen up, I ain't Captain Walker. I'm the guy who carries Mr. Dead in his pocket."

"CHARLIE DON'T SURF"
Gunpilot is offline  
post #20 of 47 (permalink) Old 06-26-2013, 08:51 PM
Registered User
 
holmz's Avatar
 
Join Date: Sep 2006
Location: Antipodes
Posts: 2,309
Nice work!
holmz is offline  
Sponsored Links
Advertisement
 
Reply

  LotusTalk - The Lotus Cars Community > Motorsports > Solo timed events

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the LotusTalk - The Lotus Cars Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome