Between 265 & 485 SQ/FT The 12-Gauge Garage

[Jack Olsen]

Ran it up to 127 mph [at my private, closed test course] and the new mechanism worked flawlessly.

I've got a few ideas to jacket some of the uprights to reduce drag back there, but I'm prepared to call the main part of the project complete. There will be more testing before I take it to Willow Springs in September, but that will be mostly to confirm repeated (and repeated, and repeated) reliability.

So thank you to everyone who has offered help and advice. One of my favorite parts of this kind of project is putting myself in a situation where I'm 'the dumbest guy in the room' and learning from people who know more than me.

Next up, I'm going to work on some ideas for improving the front splitter (and canards).

 

[Jack Olsen]

And here's video of the new way it works. Less total change in angle now (14°), but better leverage.

Click on the image for video.

 

[HOTFR8]

Looks like that set up works well.

 

[Outlawmws]

Glad to see you got it sorted Jack!

 

[buildyourown]

Random question...

What is that square block thing called?

I'm not sure what I would use it for exactly, but I think I need one

I can find "vee blocks", and "webbed angle plates", but I'm not sure what to search EBay for to get one of those blocks.

I'm also wondering what that thing behind the square block is.

I don't think the square block has a name. My guess, it was a student project or a bored machinist. Possibly with a wire edm.

The item behind that is a sine bar. Used in combination with gage blocks or adjustable parallels to position parts at very accurate angles.

 

[DocRocket]

Looks good, and to quote Robert Heinlein: "Don't worry about the theory if the hardware works."

 

[TwoBytes]

I don't think the square block has a name. My guess, it was a student project or a bored machinist. Possibly with a wire edm.

The item behind that is a sine bar. Used in combination with gage blocks or adjustable parallels to position parts at very accurate angles.

Thanks buildyourown! I did a bit of machining in high school (a long time ago), but none since, and it's always been something I'd love to get into. Seeing stuff like that always piques my interest.

I had to Google "sine bar" and "wire edm", cool stuff, sent me down a Wikipedia rabbit hole for about an hour.

 

[1Garageman]

Time to kick some *** on the race track!

 

[Jack Olsen]

Aerodynamics is like a rabbit hole, espcially when it's something you don't know very much about.

I did some reading, and deduced (rightly or wrongly) that my unlined wheel wells were costing me some drag. My wheels were basically only enclosed by the external shape of the fenders, and (apparently) that contributes a fair amount to overall drag at higher speeds. The lower the volume of the wheel wells, the better?

So at a cost of four and a half more total pounds (ouch!), I lined my wheel wells with 22-gauge aluminum. Here's an ugly picture of one.

Now, I'm thinking about jacketing the wing's uprights in the same material. The part I would hate is the weight increase. But I'm assuming that eighth-of-an-inch-thick aluminum (and then those cutouts) creares a fairly un-aerodynamic profile.

Now, maybe it would make more sense to round off the leading edge of the uprights and sort of knife edge the trailing side? That would be a lot of sanding and router work, but the benefit would be no added weight.

The alternate plan is the jacket, which would have a shape something like this little test strip shows.

That's shown off the car. Here's a wide-angle picture of the uprights in position.

Opinions? Expert opinions?

On the obsessive-devotion-to-getting-a-1:25-at-Willow-Springs front, I'm also planning on some one-day-only mods. I'll use duct tape to smooth out the drip rail profile on the car's A pillars. I'll remove both outside rear-view mirrors (I've got a parabolic mirror in the car). I'll also remove the passenger seat and door liners for the weight savings.

I'm wondering if removing the rear bumper would save me some weight (just for that run) without too much of an aero penalty? It seems like in back, creating turbulence comes with less of a penalty?

It would definitely be ugly.

 

[slik560]

Not educated enough to postulate on the fender liners, but I see prototypes in the Tudor series and elsewhere where they vent/louver the fenders to let trapped air out the top. Might not be an option in your class, though. Just an off the wall thought.

 

[Jack Olsen]

Thanks. I've thought about the vents. I don't have any rule sheet to contend with, but that kind of thing would compromise the look of the car when it's not on the track, which I'm not ready to do just yet.

 

[Zeke]

Some very ugly cars have been very fast. I remember a kart race down in Phoenix where a guy passed me in a 100cc laydown kart that was so ugly it took my eyes off the line as I watched him go by in a flurry of duct tape and thin Lexan panels configured to the design of the day.

One has to look at the front of an F1 car to see that totally fluid lines don't necessarily make the air behave. They certainly don't believe in less is more. But, you'd have to take clues from the various Porsche cars in the sports car races series including the all Porsche spec series, Porsche Carrera Cup. I think they've optimized the aero to the extent they can.

Personally, if I had free rein I'd allow any pressurized air in the wheel wells to exit via shark gills and be added to the exterior flow strategically. Do you wonder what affect the liners might have on brake cooling? Or what kind of pressure can sneak into the area between the liner and fender?

Wrapping the uprights in a shroud might end up dumping some air where it doesn't need to go or create turbulence and loss of a beneficial boundary layer and lead to flow separation. Now that was a mouthful for me as I'm not at all schooled in aerodynamics or any dynamics for that matter.

Your choice of wheels might make a difference too. I would also look at adding a Gurney flap at the front edge of the wheel arch to pull air out from wrapping the rolled fender. Might bypass any effects from the spoked rims. I know you'd prefer to achieve the lap time on a car that can be legally driven on the street in every aspect except maybe the exterior mirrors. And/or maybe the exhaust. I remember on one track day Dave from TRE removed his muffler and ran megaphones. I'm thinking in retrospect that the DME knew about the change and added fuel to compensate. More flow, more fuel, more speed. I'm sure there's a compromise to achieve the most power where you need it.

I think it's time to invest in an older data gathering system and hook up some pitot tubes. I can't think of any other device that can provide as much local info than those.

It seems you added the part about no fender vents while I was slowly typing away and looking for images.

 

[Outlawmws]

Hmmm. thinking outside the box a bit here. but a wing is trying to provide up or down force, and the wing shape is optimized for that.

those upright supports are trying to cut the air...

I'm a shooter as well and round nose bullets have a lower ballistic coefficient than Spitzers and spitzer boat tails have even lower BCs.

Based on that, I'd think leave off the sheet metal, and knife edge both leading and trailing edges of those supports and the weight cutouts. Try to get the thing to cut the air and drop off the back without causing turbulence.

Think of the nose of a jet fighter... sharp ain't it? Then it tapers off too reduce back side turbulence (like the trailing edge of a wing...)

Wheel wells are a pain, Too many variables. a friend tried to use cowl induction on his Silver State Firebird; it was NOT a sealed setup, and actually caused the air flow in the engine compartment to stall the air flow through the radiator!. We sealed that and suddenly its running cool again... (200 + MPH car...)


Point being what air is coming in from where? Your front has an air dam, right? So is the front half trying to **** air in from the outside of the wheels? Are the wheels them selves using vanes as spokes? and which way are they moving the air? (done right, you need right and left hand wheels...)

Then there are the effects of the fender flairs off the open side. I'd get some telltail yarns along the edge of the well and a camera on it... Maybe even a camera inside the well on other yarns...

 

[DocRocket]

Many bullets and fighter aircraft have pointy noses because they are supersonic. The sharp point is lower drag at HIGH speeds (think 600 mph and up). Take a look at airliners. There is NOTHING about an airliner that is not about improving the lift/drag ratio, unless it is mandatory to carry the appropriate number of passengers. The nose is quite blunt. That minimizes drag at subsonic speeds. The rounded, teardrop shape is minimum drag for low speeds (anything you are going to get a 911 without JATO rockets to run at). If you are going to spend time with a file, round the front edges and knife edge the trailing edges, but I suspect that a chamfer on the leading edges will get you most of the benefits at lower effort than the full up grinding.

As for the rear bumper, I don't know how much it will help. The reduction of however many pounds that is would probably help some, but I don't know how much that will impact the drag. You would basically be removing a blunt tail surface and replacing it with a slightly different blunt tail surface. There might be a little bit less trapped air behind the bumper, but not much, the splitter/chin spoiler at the front should eliminate most of the air under the car.

The major effect of turbulence at the rear is to keep the flow over the rear attached, which is normally slightly better than detached. If you look at a few factory cars, like the Lancer Evos, you see the vortex generators over the back window? Those are to create turbulence at the back edge of the roof to keep the flow attached on the back window, reducing drag a bit, compared to detached flow. Same principle as dimpled golf balls--in the normal speed range of golf balls, the attached turbulent flow is slightly lower drag than detached laminar flow.

 

[Squankum]

Jack:

There are many practical experimenters (hacks?) when it comes to aero improvements over at ecomodder.com. Speaking of ecomodding, I was poking around the web for ideas for belly pans about a year ago, using google image search, when I spotted your car somehow, even in an underbody mechnical photo, I spotted the car.

Took a quick hop over there just now and was reminded that Priuses now have little air dams for the rear tires. I recently saw something there about the rear wheel wells on Priuses having some venting to them, but I forget the details.

Since you don't have rules and you don't have a pit crew doing tire changes, I wouldn't just line the rear fender wells, I would also put skirts on there. Alas, I cannot think of a way you can make a quick install/release panel that mounts there without doing things to that bodywork that would make many of us cringe and some 911 folks faint like fops.

But you could, in theory, seal up the rear wheel wells somewhat, as long as you can manage the brake venting otherwise. Note, in NASCAR, they use electric fans to move air in brake duct hoses when they really need it. Also, enough of those hoses with fans pointed straight down can help with the downforce. (My info may be 5 years old, but they were doing it at one point.

Of course, fender skirts would make some purists have a case of the vapors, but I always say you should throw Porsche history back in their faces: What about the 1951 356 aluminum bodied coupe, huh? Skirts all around!

Then, for yuks, you could just paint Fuchs wheels on the skirts.

Oh and, I understand the usual tension between "modified street rod but still quite a 911" vs. "Race car and nothing is sacred", but rain gutters are an abomination to the winds and must die. You have the grinders... heck, you don't even have rain...

Oh, and if you don't run bumperless, at least drill the bejeebers out of that bumper.

 

[chiz1180]

Just curious in race trim does the car have a diffuser? Also for 1:25 run how feasible would it be to ditch the muffler? I know some tracks frown against that but it would definitely save weight.
btw excellent garage and I like that you drive you car, too many people who have Porches in my area don't drive them like the should. Best of luck achieving your goal.

chiz1180

 

[EdT]

I've been following your quest for some time. Taking a step back from the details for a moment, I have a few thoughts.
Ideally, a race car is always accelerating as fast as it can or decelerating as fast as it can. If that's not what's happening, then you're doing something wrong. Again, ideally there is no limit to top speed and you just accelerate until it's time to slow down again. In both acceleration and deceleration mass (weight) is your enemy. Lighter is better for both, but heavy is not what limits your top speed. That is limited, ultimately by a balance of how much power your engine can develop and how much drag your car has.
Assuming no speed limiter or other artificial limit and assuming that the engine does not run out of revs before equilibrium is reached any car will reach a speed where it is no longer accelerating but has run into an aerodynamic wall where the drag (and other frictional losses) absorb all the power that there is and the car is stuck at that speed. Clearly, no power is going toward acceleration so it must all be consumed by frictional losses (drag).
The math for acceleration (F=MA or A=F/M) is linear. There are no exponential elements. For a given engine output, you will pick up some acceleration for each unit of mass you can get rid of regardless of how fast you are going. Aerodynamic drag has a somewhat more complex equation that I don't recall in detail, but drag is related to the square of the velocity. That is, twice as fast, four times the drag. Four times as fast, 16 times the drag etc. . That's a two edged sword because each unit of drag you can eliminate pays back way more at speed that a unit of mass.
So, if you look at your track performance profile chart (I think you showed one once) you may be able to determine the benefit of spending time on weight reduction vs aerodynamic improvements. Weight reduction will always help, but if you find that for half of the high speed straight you have run into the wall then you need to look at how it would work out if you didn't hit a higher speed wall at, say 3/4 of the length of the straight. (This assumes that your engine is not at max rpm when you hit the wall). 5% less drag is the same as 10% more power.
Just as a point of reference a cylindrical object passing through the air has a drag of "X". An object with the same cross sectional area at the same speed has between 1/8 and 1/10 as much drag. So, take off the radio antenna. I would think that the supports for your wing are a drag nightmare and might benefit from the fairing you have in mind.
This is just some miscellaneous ramblings late at night, and the real world is not nearly as cut-and-dried, but maybe it will help a little.

 

[Outlawmws]

Many bullets and fighter aircraft have pointy noses because they are supersonic. The sharp point is lower drag at HIGH speeds (think 600 mph and up). Take a look at airliners. There is NOTHING about an airliner that is not about improving the lift/drag ratio, unless it is mandatory to carry the appropriate number of passengers. The nose is quite blunt. That minimizes drag at subsonic speeds. The rounded, teardrop shape is minimum drag for low speeds (anything you are going to get a 911 without JATO rockets to run at). If you are going to spend time with a file, round the front edges and knife edge the trailing edges, but I suspect that a chamfer on the leading edges will get you most of the benefits at lower effort than the full up grinding.

SNIP

OK, but then there are Indy and formula cars, well under supersonic, and still have sharp, pointy, noses. Yes, Jacks top speed is something above half of their top speeds, on the big tracks, but they also spend a lot of time well under 200 on the smaller and tight twisty tracks.

I still think knife edging, or close to it, both leading and trailing edges on the uprights is the way to go.

 

[qship510]

Racing makes heroin addiction seem like a craving for something salty

You've got it bad Olson, good on ya mate

 

[alpinewhite]

Back to the garage.

Jack, why didn't you take the free Listas you were being offered?? That was sacrilegious not to accept them.

 

[Boosted1]

4 lbs!! Kidding. Another option would be diet for driver to offset, just sayin

I just bought an Aluminum alternator bracket for my car to replace the stock steel one, so I do get it. Have a nice day. As always, I enjoy the updates.

 

[gtr cook]

Would it be possible to squeeze a rear diffuser under the engine without compromising temperatures? That may be something to look into, especially if you can get it to work with the front aero and the active rear wing.

 

[Squankum]

Now, in theory, you might say that engine fan is blowing in the wrong direction for down force.... but the sheet metal around the engine, everything was designed for a certain direction.... and experimenting would be much too expensive. (As in, if you screw it up and the engine overheats...)

Also, "underneath" air could be dirtier. And who knows, maybe it helps with the airflow over the back of the car.

 

[JYank]

Jack, look at drag racing funny cars. they go over 300 mph.

 

[RonB001]

To quote TwoBytes from post 3737:
Random question...

"What is that square block thing called?"

These are from a family of items called "parallel blocks".

Some are solid, machined steel, usually long-ish and fairly thin. An example 1/4" x 3/4" x6"
Many are rectangular, with holes, some threaded. An example 1" x 2" x 3".
Some, like the referenced picture, are hollow cubes.

These are all machined parallel, so that each dimension is exactly (within tolerances) what it says it is.

They are often used for fixturing parts for machining. Google image search "parallel blocks" for examples.

Regards,
RonB

 

[chiz1180]

Jack, look at drag racing funny cars. they go over 300 mph.

Drag aerodynamics are totally different game than road race... drag cars need to only go fast in a straight line, where as road race cars need to balance going fast in a straight line and going fast around corners.

chiz1180

 

[JYank]

Drag aerodynamics are totally different game than road race... drag cars need to only go fast in a straight line, where as road race cars need to balance going fast in a straight line and going fast around corners.

chiz1180

I realize that, but some of the techniques apply to both.

 

[TwoBytes]

These are from a family of items called "parallel blocks".

Some are solid, machined steel, usually long-ish and fairly thin. An example 1/4" x 3/4" x6"
Many are rectangular, with holes, some threaded. An example 1" x 2" x 3".
Some, like the referenced picture, are hollow cubes.

Thanks Ron! I had seen solid parallel blocks before, it makes sense that a hollow one would be called the same thing.

 

[Sune]

Hi Jack, you properbly already know it but just wanted to share the images of another very nice 911

http://ironandair.com/journal/#.U_HCEfl_sQk

 

[Linda@Lista]

@frijolee - Hey Joel, if you have any questions on Lista, please don't hesitate to reach out! We are always excited to see the new garages on here

 

[tc-cad]

Hi Jack

I recently have been doing a lot of reading about installing a Chevy LS v8 engine into various Porsches. I realize this may go against a Porsche Purist train of thought but I was wondering what your thoughts/opinions are on this subject.

Thanks
TC-CAD

 

[Squankum]

Jack:

A week or two ago I learned about this thread: a man in Scotland putting a newer (but not super modern) Mercedes turbodiesel into an older (R107) SL convertible.

I post the pic here because he put a two post lift in his small shop and it doesn't look too horrible for space intrusion. It reminded me of you and your table lift. Of course, when your lift isn't being used, it has zero space intrusion.

And I post the link, because... hey everybody! Look at this guy's beautiful, thorough work on this install!

http://www.peachparts.com/shopforum/diesel-discussion/350221-not-another-diesel-107-a.html

 

[Sune]

Hi Jack,

You've been very quiet lately. Is all well?

Best Regards
Sune

 

[Mpower5266]

I read through this thread a while ago but the other night I caught your Petrolicious video and it reminded me to post in your thread. Great work and I love that 911.

 

[autolex]

Nice work on the wing Jack, good to see you're talking to Keith Tanner too (he's got some incredible cars and has done some really revolutionary stuff for cheap-aero )

 

[Coolabah]

Many bullets and fighter aircraft have pointy noses because they are supersonic. The sharp point is lower drag at HIGH speeds (think 600 mph and up). Take a look at airliners. There is NOTHING about an airliner that is not about improving the lift/drag ratio, unless it is mandatory to carry the appropriate number of passengers. The nose is quite blunt. That minimizes drag at subsonic speeds. The rounded, teardrop shape is minimum drag for low speeds (anything you are going to get a 911 without JATO rockets to run at). If you are going to spend time with a file, round the front edges and knife edge the trailing edges, but I suspect that a chamfer on the leading edges will get you most of the benefits at lower effort than the full up grinding.

As for the rear bumper, I don't know how much it will help. The reduction of however many pounds that is would probably help some, but I don't know how much that will impact the drag. You would basically be removing a blunt tail surface and replacing it with a slightly different blunt tail surface. There might be a little bit less trapped air behind the bumper, but not much, the splitter/chin spoiler at the front should eliminate most of the air under the car.

The major effect of turbulence at the rear is to keep the flow over the rear attached, which is normally slightly better than detached. If you look at a few factory cars, like the Lancer Evos, you see the vortex generators over the back window? Those are to create turbulence at the back edge of the roof to keep the flow attached on the back window, reducing drag a bit, compared to detached flow. Same principle as dimpled golf balls--in the normal speed range of golf balls, the attached turbulent flow is slightly lower drag than detached laminar flow.

.... and here's me thinking " cars, garages , tools - it ain't Rocket Science"

LOL I stand corrected , sir... and I think I learned something today.

 

[Lyndon]

Hi Jack. I've just completed all 198+ pages of this thread. Phew - that's taken some time, but you (and many others on GJ) have motivated me to look at my poor old garage (and as far as the boss is concerned - rubbish repository) in a whole new light.

I've already used advice from here to make a new work bench from scratch (& a ripper it is too), and look for ways to get everything a place, off the floor as well.

Anyway, notice you haven't posted since 8th August so hope all is OK, and I hope the DRS (from F1) wing worked OK.

From the Land Down Under.

 

[ekraft84]

Jack, love the garage. It goes without saying of course, but I don't think I've ever posted in this thread. Just read through it.

Thanks.

 

[chicane]

Agreed. When they get a bunch of the early cars together, it can cause quite a stir. (And at least once, I can say, it's led to a 7-cars-at-once arrest by multiple police helicopters.)

Awesome...

 

[Lyndon]

Bump - Anyone know where Jack is?