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How to build a front splitter for the One Lap VR-4

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GreenGSX

DSM Wiseman
371
5
May 13, 2002
Rochester, New York
By now its no longer a secret that the VR-4 is getting a wing. Not just a “ricer” looking wing but a real-deal if you have to ask you can’t afford it type of wing. The deal was too good to pass up so we went for it. What does a rear wing do? In simplest terms it pushes down on the back of the car. The faster you go the harder it pushes. The angle of the wing can be adjusted to “dial” in the amount of down force. So why the wing? Having a rear wing helps keep the rear of the car planted and adds overall to the amount of grip the car has. It also lets you set the car up to over steer at low speeds when the wing has a smaller amount of down force and when you go faster the car becomes neutral so you can take transitions at higher speeds. The problem is that whenever you push on the back of the car you end up slightly lifting the front. That’s important because when you want the car to turn you need all the weight you can get on the front tires.

This is where the front splitter comes in. A splitter is noting more then a big flat piece of something attached to the area under the front bumper which directs air under the car. Since the air under the car has a shorter distance to travel then the air going over the car it moves faster.. Bernoullis’ principal says faster moving air has a lower pressure and that lower pressure is what causes front down force. It’s that down force that we are after to help balance out the added down force of the rear wing.

For a splitter to work it has to be flat, parallel to the ground, and be able to hold together at high speeds. The benefit of the splitter gets better the further back under the car it goes and in real race cars is part of an under tray that includes a flat middle and a diffuser at the rear. With very little time to build a splitter we are only going to bring ours as far back as the front of the front tires. To help the fact that we are not going very far back under the car we are going to extend the lip of the splitter almost 5 inches beyond the lower lip of the fascia.

To build the splitter I chose a product called alumalite which is a sandwich of aluminum-plastic honeycomb-aluminum. Its used for signs and the sides of tractor trailers. I was able to get a 4′ x 8′ sheet of 1/4″ alumalite for $90 locally.

Working with it is pretty easy. You can drill it, cut it in a table saw, use a grinder, or pretty much any other power tool you have. Lightweight and strong it’s a pretty versatile material for race cars.

A splitter has to be strong. It has to be able to withstand high loads without bending. If it bends you loose some of the benefit and some of the down force. So to make this as strong as I could I decided to build a frame for it out of 1″ aluminum tube. The frame would be then bolted to 1/2″ nuts that I will weld to the bottom of the. I used two on the engine cross member with a third on the radiator core support. I’ve jacked the car up on the engine cross member so I know its strong enough to handle the loads of the splitter.

I am using 1/2″ bolts to attach it to the car so I welded up some 1″ tube risers to the frame to set the height of the splitter. The lower the splitter the better it works but the lower you build it the better chance you have of having it rip off when you get a little to aggressive over a set of rumble strips. I decided to build it with 5″ of ground clearance which is just enough to get in and out of my driveway and low enough, I think, to work.

Once in place there is a large gap between the bottom of the fascia and the splitter that must be filled. After looking for materials to fill that gap I settled on the alumalite. By cutting relief cuts on the back side I was able to form it around a Map gas bottle so I knew it would conform to the larger curves of the fascia.

With the splitter and the air dam built it was now time to turn to a support system. I need to build a set of turnbuckles to support the leading edge of the splitter and to allow some up-down adjustment to fine tune the amount of down force. I found a set of turnbuckles at my local hardware store that along with some threaded rod and clevis pins would give me what I needed.

Here are some photos of the build. For the rest of the story and all the photo’s be sure to check out our website here Rochester DSM OneLap Blog Archive How to build a front splitter
 
9!'clipseDOHC;bt7855 said:
Looks pretty hefty! Have you tested it on a track yet to see how it performs? Or are you waiting for the wing because they work together?

I have not put it on a scale but it does not weight that much. I can easily move it around with one hand.

The splitter has been on the car for a couple of weeks now and so far so good. Its holding both its shape and angle so at least I know I'll be able to set it and it will stay put. I have no real data other then the seat of the pants but that is telling me that front end grip and braking are up. The whole story can't be told until the wing gets on the car. That is due to arrive tomorrow.
 
Looks awesome!! I need to learn to weld asap so I can make one!
 
I'm sure it will work just fine, but you should always keep in mind the direction of the corrugated material when building things. There are arrows on your board telling you which way the material should be used.

I had an 3D art project where we needed to build a chair to support our own weight using nothing but a 4x4 sheet of corrugated cardboard. Mine was a success at holding my 240lbs.

If you cut the material along the arrow lines, you can fold the material much easier due to it's properties.

I'm sure your splitter will be plenty strong, especially with the frame support, but others may need to keep this fact in mind when building other structures.
 
iamtall77;bt7859 said:
I'm sure it will work just fine, but you should always keep in mind the direction of the corrugated material when building things. There are arrows on your board telling you which way the material should be used.

I had an 3D art project where we needed to build a chair to support our own weight using nothing but a 4x4 sheet of corrugated cardboard. Mine was a success at holding my 240lbs.

If you cut the material along the arrow lines, you can fold the material much easier due to it's properties.

I'm sure your splitter will be plenty strong, especially with the frame support, but others may need to keep this fact in mind when building other structures.

That's a very good point. But the splitter is 5' 9" wide so there was only one way to harvest the material from a 4' x 8' sheet. Having had the material in my hand it appears to be equally strong in all directions. Don't forget that I have a frame built of 1" aluminum tubing that that bolts to the alumalite making it super strong. I would stand on it and take a picture but I don't want to take the chance. There are only a few days left before the start of the race and i am fat. Too risky....
 
I'm very excited this year. I'm bummed that your trans just crapped out on you though. Hopefully it will be up to the task. I know on the org we are looking to get you a backup. I'm just curious why you didn't also fab up some canards. I would assume any extra down force you can get is good?
 
thecman02;bt7862 said:
I'm very excited this year. I'm bummed that your trans just crapped out on you though. Hopefully it will be up to the task. I know on the org we are looking to get you a backup. I'm just curious why you didn't also fab up some canards. I would assume any extra down force you can get is good?

It funny you mention that because the splitter was designed for a canard to help get air past the front tire which sticks out past the fender. The edge of the splitter is flush with the outside of the tire.

The only reason I didn't build something like that is time. I just didn't have the time to develop this any further then how it is now. If it survives the race I will take what I learned and tweak the design a bit. I have a DE event at Watkins Glen at the end of the month that I can really do some testing at.

I have a spare transmission in the car now that is shifting good enough for us to go. It is not going to shift at high rpms/loads but if we baby it we'll be fine. I would like to arrange for a spare that we can borrow in South Bend. I am not worried about the race but it is important to get the car home.
 
Nice job, just one suggestion, put splitters, or air dams on either side to channel the air into the IC and maybe ramp it to the bottom of the IC. At high speeds that flat may cause air flow issues. Also if you need any composite help hit me up Expandable foam (its easy to shape) and Fiberglass would be nice and light and cheap.
 
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