Air Dam

[wheelrdealer]

Bill you put a lot into that project.

It looks great.

Sorry to hear you won't be at Speed Week this year.

Mike:

It is 5,200 miles round trip to Bonneville from my shop in Florida. Right now I have a good motor but not a record setting motor. We can probably get a few MPH's more but we are a long way away from the 27.316 mph needed to match the current record. The car is ready, so I will spend this year adjusting the car and gathering parts to build a more capable engine. May change classes but have not decided.

To have a successful run at the D/CGALT record we will need a perfect motor, perfect gear, perfect salt, perfect tail wind, perfect driving, and all of the stars to align above floating mountain to create a unique magnetic pull to help us with our top speed. In other words, the D record was set by some very talented LSR guys and will be darn near impossible to break with a Camaro.  It is that Darn Near part that give us hope.

I know I cannot whine about long haul issues considering the distance a lot of LSR contenders travel from. We just feel is it better to conserve the cash we would spend on 2014 and get our short block together. Our next goal is to get the car in the 220's and see how it handles. 

[wheelrdealer]

I thought I would show how the tow bar and tow loop hooks up. It uses (2)  3" X 1/2" quick pins. 


The first photo is the slot in the bumper and the 1/2" hole where the bumper carriage bolt used to live. We reinforced the factory bumper mount and made a slot for the devices to slide into so there is no sise to side movement possible.

The second has the two ring installed. If I had a wider bumper I would have built this vertical instead of on the horizontal for aero reasons.

[wheelrdealer]

The first photo shows the driver's side tow bar hook up.

The second shows the tow bar installed.

I hope this triggers someone to think of an idea for their car. I have taken so many ideas from this site it is time I put something back into the well. Although my fabrication skills are small ball compared to most of the people posting on this site.

Lesson's learned: 1. With the pivots on an angle they will not rotate up or down more than 20 degrees. Which is plenty flexible for the level salt. Would not work as a place with larger dips or bumps. Someday I will go back and correct this but for now it works fine. Second, I think I will make the next tow bar out of chrome moly. I think it would be a lot lighter. This is a standard Northern Tool 5,000 LBS tow bar. Still easy to install with one person.

BR

[nickleone]

metermatch said  I have a spot welder, but no way to weld aluminum so I was thinking steel could be easier for me to fabricate.

Look at this:
https://www.youtube.com/watch?v=gcgC3V3mkcw

Nick

[wheelrdealer]

No alum. Welds on the air dam. All the Dzus tabs, braces and turn buckles are steel. Attackers to the alum. Via ss counter sunk Allen heads.
It an easily me made of steel.

BR

[metermatch]

Cool idea on the spot welding of aluminum.  I'm going to take that idea and discuss it with an old engineer friend of mine.  He has patents from working at Ford many years ago on developing spot welders for the cars on the assembly lines.

Jeff

[SteveM]

I'm working on an air dam similar to yours, and have a decision to make.

I can have the air dam situated so that it's vertical, but with no "lip" at the bottom, or leaned back a bit, but with a horizontal lip at the bottom of the dam.

I have read about the importance of the lip, or splitter, at the bottom edge, but don't know what is given up by leaning the air dam back (bottom edge farther back on the vehicle than the upper edge).

I've been messing around with cardboard as a template, and I'm planning to buy the sheel Aluminum tomorrow, so it's just about decision time.

Which is better - vertical air dam with no lower lip, or leaned back air dam with a lip?

Steve.

[wheelrdealer]

SteveM

Perhaps someone that knows can chime in. I just reproduced what I remembered seeing on the salt. I have mine set slightly forward at the bottom about 3/8" from the top. But I can easily reverse that with the turn buckle braces. The splitter lip can easily be added to the bottom section. Here I thought I was done and you have given me something to think about! Actually every time I read someone's build diary I see something I want to do.

BR

[SteveM]

Same here - almost all of my ideas were "pinched" from someone else's build thread.

To get a splitter "lip" on mine means that I'll have to lay the air dam back whatever the forward projection of the splitter is.  It's my understanding of the rules that no part of the air dam (splitter included) can extend beyond 1/4" in front of the forwardmost part of the bumper.

I hope someone with firsthand experience weighs in on this topic.

Steve.

[SteveM]

I have seen this article before, and just refreshed my memory.  It looks like the splitter definitely helps with a vertical air dam...

http://hanchagroup.wordpress.com/2013/01/29/splitter-or-air-dam-which-design-is-best/

This isn't exactly university level peer-reviewed research, but looks valid, nonetheless.

Steve.

[wheelrdealer]

Steve:

Thanks for the info. I will add the splitter to the bottom. I will have the same challenge on the set back from the bumper tip.

I do have a question for those that are more experience than me. The difference in down force between what I had and what I have is about 2/3rds more down force at 100 mph according to the article supplied by SteveM. My calculations show I need to add about 120 lbs to the front end of my car to get the CG exactly 6" ahead of the CP sitting still. How does the increased down force from my new air dam/splitter play into that calculation? If my down force goes up by an estimated  multiple of 3 at 200 mph do I still need to add the static weight to get the CG and CP 6" apart? Or will the down force accomplish the same thing?

Thanks

BR

[SteveM]

BR:
   My understanding of the statics in this situation is that any downforce created by the splitter will be applied as a concentrated load at the location of the air dam / splitter interface.  Since the air dam is attached directly to your bumper, it would be like having the load applied to the bumper.

   If the downforce is 150 lbs at x mph, then it would be like having a 150# person standing on your bumper.  At 200 mph, if the load triples, it would be like having a 450 pound person standing on the bumper.

   I guess the difficult thing related to your CG/CP comparisons is that the downforce is continuously changing as the speed increases.

   The comparison above is not based on my expertise with aerodynamics, only as an engineer.

Steve.

[wheelrdealer]

SteveM

Thanks I am certainly not an engineer but I have been known to hang out with some. I guess then the question is, do I set up the CG and CP relationship as it sits in my shop? Does adding down force at speed shift the CG and CP relationship?

 My rear spoiler is set flat 0 degrees as I ran it at speed week. I did not spin and the car went straight so I did not add any angle. My new spoiler can be adjusted up to about 12 degrees based on the handling. I gues is I add spoiler angle aka down force to the rear that will have to be considered in my CG and CP relationship.

BR

[Sumner]

... I guess then the question is, do I set up the CG and CP relationship as it sits in my shop? Does adding down force at speed shift the CG and CP relationship?....

I'll be interested in what others said but I'd figure it "as it sits in my shop".  The reason being that if the car starts around then all of those 'aero' calculations can go out the window real fast.  They will probably help in keeping the car straight in the first place but once it isn't then it is going to be the CG/CP as figured in the shop that will probably come into play.

In our case when the throttle stuck wide open the car started around when it had been running nice and straight, but once part way around the CP caught the car from going all the way around.  If the CG would of required 'aero' help then it might of gone all the way around once that 'aero' help started to go away.

Just my thoughts,

Sum