Belly Tank Build Diary

[Mike Brown]

Mike.
Always a pleasure to watch your latest mods to your lakester. Love the wing idea, what are the dimensions of the wing section? It looks like an extruded section, who did you get it from? I might suggest that you cut the wicker bill off and make it so that you can add wicker bills of different heights. I like the mounting "post" you can make it pretty aero with some shaping and you have lots of material to grind out a nice shape. I am sure you thought of maybe using some of the commercial aero tubing but the price is very restrictive, $106/ft for the 3 3/8 inch stuff! We used some for our front axle, had to put a piece of 1-3/8 1/8 wall tubing through it to make it strong enough.

Keep up the good work, looking forward to seeing your mount and adjustment mechanism.

Rex

As always Rex, thanks for the kind words and comments.  A few runs will tell if the downforce improves the top speed with increased traction over the additional drag of the wing.  My data from the track indicates a lot of wheel spin on the big end of the mile.  First and foremost I want a safe vehicle so I am approaching this project cautiously. 

The wing is a really nice aluminum extrusion.  It has "screw splines" to facilitate installation of end plates.  The wing was supplied by Winglogic (wing-logic.com).   The chord of this wing is 9.8".  To be compliant with lakester rules I narrowed the wing to 44" which is the narrowest dimension between the wheels.  The original wing was 70" wide along with all of their data.  I have been told multiple times that I cannot multiply their published results by approximately 60% to get downforce and drag numbers but I am using this number for my calculations. 

I also considered cutting the Gurney flap off but have been cautioned by the manufacturer that the drag will increase while the downforce is reduced.  With the marginal power of the lakester I want to keep the drag as low as possible.  It was explained that taller Gurney flaps can easily be attached.  The manufacturer has been very helpful even though I am in the minority of land speed customers (maybe the only) that they have.  They also recommended posting in a facebook group "Professional Awesome Racing Technical Forum".   There was some good information regarding my post but like most forums it quickly went off the rails since I am not road racing. 

I want the mounting pylon to have as good of aero as practical but strength and rigidity are very important to me.  I watched Clark Rosenstengel's wing come off his Camaro at speed during a lap at the ECTA event in Arkansas and don't want that to happen.  Being land speed weight doesn't scare me, I prefer to build strong. 

For simplicity I will be hard mounting the wing with zero incidence and no adjustablity for initial evaluation.  This configuration offers the lowest amount of drag.  There are other methodologies to increase downforce (all with an increase in drag) without changing the angle of incidence.  These include taller Gurney flaps and larger/different shaped end plates.  If circumstances prove that this is a good thing I can always retrofit an adjustment mechanism.  Sometimes too many things to adjust just leads me to tinkering and not using good process for evaluation. 

[Mike Brown]

A view of the pylon upright.  The tube was stiffened with a 3" wide section of 11 gauge steel.  The stiffener was then "faired" with two additonal pieces of 11 gauge steel. 

[Mike Brown]

The mounting base was drilled and tapped to allow easy installation and removal of the wing.  I added two 3/16" spring roll pins to insure good alignment.  The mating holes in the wing are a slip fit. 

[Mike Brown]

The wing with end plates assembled to the car.  Still needing final welding and painting. 

[tallguy]

Mike, I'd like to suggest a few things related to your wing.  I'm not a professional
aerodynamicist, so I invite you to consult with other folks on these ideas.

This is the first automobile wing I have seen that is mounted on a single pylon
instead of two.  I'm concerned about oscillation/vibration of the wing, with each
end of it "bouncing" up and down.  If this oscillation exerts enough oscillatory
force, it could conceivably affect traction, resulting in alternating increase/decrease
in traction on each drive wheel -- like a series of "chatter-like" wheelspin in little
"blips".  It seems to me that two narrower pylons, spread apart by about 18" or more would provide significantly more stability.  They could each be narrow and aerodynamic, such that the total drag from them doesn't have to exceed the drag from the single pylon you have shown.  The "fairing" shape of the pylons could likely also be improved, compared to having flat-shaped added material (I never see flat shapes on aircraft wings).  The dam plates that are attached to the wing probably should not be rectangular.  Instead, something (seen as two-dimensional) similar to
an "airfoil" shape would probably be better.  The fasteners that attach the dam plates could be less-protruding.  You might want to consider flat head fasteners.  I am also a bit surprised about the claim that removal of the Gurney item would INCREASE
drag.  My opinion is that removal would decrease drag and also decrease downforce.  Good luck with this car.

[Mike Brown]

Mike, I'd like to suggest a few things related to your wing.  I'm not a professional
aerodynamicist, so I invite you to consult with other folks on these ideas.

This is the first automobile wing I have seen that is mounted on a single pylon
instead of two.  I'm concerned about oscillation/vibration of the wing, with each
end of it "bouncing" up and down.  If this oscillation exerts enough oscillatory
force, it could conceivably affect traction, resulting in alternating increase/decrease
in traction on each drive wheel -- like a series of "chatter-like" wheelspin in little
"blips".  It seems to me that two narrower pylons, spread apart by about 18" or more would provide significantly more stability.  They could each be narrow and aerodynamic, such that the total drag from them doesn't have to exceed the drag from the single pylon you have shown.  The "fairing" shape of the pylons could likely also be improved, compared to having flat-shaped added material (I never see flat shapes on aircraft wings).  The dam plates that are attached to the wing probably should not be rectangular.  Instead, something (seen as two-dimensional) similar to
an "airfoil" shape would probably be better.  The fasteners that attach the dam plates could be less-protruding.  You might want to consider flat head fasteners.  I am also a bit surprised about the claim that removal of the Gurney item would INCREASE
drag.  My opinion is that removal would decrease drag and also decrease downforce.  Good luck with this car.

Thanks for the input.  The end plates and fasteners were supplied with the wing, I also believe that they could be improved upon.  The frame of the belly tank does not lend itself to having many easy structural points for attaching a wing and one of the reasons that I chose a single pylon.  I will make multiple passes to evaluate the dynamic stability of the wing.  I have plans to add some guy wires to help stabilize the wing if oscillation becomes a problem. 

[Mike Brown]

I was looking for an illustration that "Woody" sent me indicating that a simple flat piece of stock attached to the rear of round tubing would significantly reduce drag but couldn't find it.  I did find this illustration in a kit plane site that shows that it is not entirely uncommon to fair tube with flat sides and thin trailing edges.  My goal with the three pieces of flat stock were to reduce drag and increase stiffness. 

[WOODY@DDLLC]

Simple version - other factors involved.

[Mike Brown]

Simple version - other factors involved.

Thanks for chiming in Woody.  I am glad someone has good recall. 

[SPARKY]

Response to TG

As someone who has walked the track for the first 3 miles at B'ville many times to see what I could learn--  I can attest to the spin marks  alternating from side to side much like evenly spaced footprints.---

I do not even pretend to know all of the inducing forces of the many things that could induce the rhythmic patterns but they exist some of them obviously very violent. I have experienced it with my car.  One of the reasons I chose to not run suspension is if I am ever to go to a wing it will be mounted on the axle housing over the axle bearings

[Mike Brown]

Response to TG

As someone who has walked the track for the first 3 miles at B'ville many times to see what I could learn--  I can attest to the spin marks  alternating from side to side much like evenly spaced footprints.---

I do not even pretend to know all of the inducing forces of the many things that could induce the rhythmic patterns but they exist some of them obviously very violent. I have experienced it with my car.  One of the reasons I chose to not run suspension is if I am ever to go to a wing it will be mounted on the axle housing over the axle bearings

I understand that on the salt.  I only race mile events on paved runways.  They are unimproved race surfaces with bumps, dust, etcetera but they do offer significantly more traction than the salt.  The main deciding factor early on to run suspension was for safe stopping.  I choose to not add downforce or weight on the rear of the car alone which would negatively affect my CP verses CG.  The CG is already too close to the CP on this car which caused me to add 120 pounds of ballast behind the driver's seat.  By locating my wing forward of the rear axle two things happen, my CP moves further back and I can bias the downforce from front to back without adding additional weight to the car or separate downforce generating aero on the front of the car.  I get that adding weight to the rear of the car helps with traction especially when you have miles to get up to speed.  I think that mile racing has some similarities to drag racing whereby accelerating a lot of additional weight to 200+ in a mile is detrimental to achieving higher speeds.  I am not however looking to significantly reduce the weight of my car.  My wing is easily removed, we shall see if the car is faster or slower with it in May.   

[SPARKY]

Mike,

When you put a jack under the RR axle how  for will the tire come off the ground when all the tire are inflated to race pressures, before the RF lifts?  A more telling situtation would be to put the care on 4 corner scales and do it and record the 4 weights.

[JAL AKA JL222]

Response to TG

As someone who has walked the track for the first 3 miles at B'ville many times to see what I could learn--  I can attest to the spin marks  alternating from side to side much like evenly spaced footprints.---

I do not even pretend to know all of the inducing forces of the many things that could induce the rhythmic patterns but they exist some of them obviously very violent. I have experienced it with my car.  One of the reasons I chose to not run suspension is if I am ever to go to a wing it will be mounted on the axle housing over the axle bearings

   Unlocked rear end gears?

                         JL222

[SPARKY]

JL 222

I have no idea which cars made the "footsteps".   I would assume that most were higher horsepower cars by the length and depth of the spin marks and how far down the track they were.  I assume that some were liners by the width of the track  but most had fairly wide rear wheel spacing.

I assumed that most were spools, but that is pure assumption on my part.

[Mike Brown]

Mike,

When you put a jack under the RR axle how  for will the tire come off the ground when all the tire are inflated to race pressures, before the RF lifts?  A more telling situtation would be to put the care on 4 corner scales and do it and record the 4 weights.

This is the last car weights.