Need aerodynamic help for a tank

[WOODY@DDLLC]

Some comparative drag numbers just for S&G! The P-38 tank is really not too bad.  Until you start modifying it! 

[John Burk]

Those numbers point out how good the design is on George Johnson's front wheel drive Saltosaurus lakester . No axle drag , narrow rear tires , legal fairing (header collector) behind the front tires .

[Sumner]

Those numbers point out how good the design is on George Johnson's front wheel drive Saltosaurus lakester . No axle drag , narrow rear tires , legal fairing (header collector) behind the front tires .

In addition to the above, he can keep the car weight low since the majority of the weight is forward giving him great CP to CG along with good traction.  No need to add ballast in the rear for traction and then more in the front to move the CG forward.  If one needs to add ballast for traction the same ballast just makes the CG move even further forward, a win, win.

I think about the only possible negative to front wheel drive is coming off the power the car can drive very differently than a rear wheel driven car on and off throttle.  I believe he had some problems with that but might of worked those out.  It was a great design and got him into the 2 club.  If I was to do things over from scratch I'd look very hard at front wheel drive,

Sumner

[Interested Observer]

If I was to do things over from scratch I'd look very hard at front wheel drive,

Sumner:  You’re right!

Along these lines, whatever happened to Jim Feuling’s front engine/front drive liner?  Always seemed to make a lot of sense to me.

[John Burk]

One of these Casale overrunning clutches solves the front wheel drive off throttle instability problem . They normally bolt to the output of a Casale V drive but can be mounted independantly like like the Danny Boy streamlined has . JJ from East Texas who used to post here makes / made a similar unit .


http://www.casalev-drive.com/files/QuickSiteImages/SWIRLAWAY_op_710x473.jpg

[Rex Schimmer]

Doesn't take long looking at Woody's chart on a "standard" P38 tank to see that what you do with the wheel/tires and the axles have a lot bigger effect than anything you do with the actual tank body. Reducing the drag of the axles, which I assume are a standard round section, can be reduced by over 50% with simple aero fairing, I know this works as we faired the rear axle of Steve Nelson's lakester and picked up 6 mph with no other changes. The selection of the wheel/tire combination is very important, check Sparky's beautiful front wheels and top fuel tires to see a good approach. Sparky also likes to run short rear tires, again trying to reduce the frontal area of the tires. It is the attention to detail on a lakester that makes them fast, no junk (spindles, shocks,springs,radius rods etc) hanging out in the breeze. Smooth is fast.

Rex

[WOODY@DDLLC]

Another chart here [Reply #10]: http://www.landracing.com/forum/index.php/topic,16411.0.html

[oj]

OJ,
Sounds to me like you may be considering building the actual tank your self. If this is your plan then you need to be looking at some of the NACA 66000 wing sections for dimensions. My preference is the 66018 section in revolution which also happens to be the section that the number 496 AAgas supercharged streamliner of Rob Freyvogl and Branden Barnard. Check out their build at http://www.landracing.com/forum/index.php/topic,8665.0.html . You can see their great design of a car that is very similar to a tank. As Nathan Stewart said, tanks are a difficult build bit it is a challenge that many people take just for the sake of doing it. Also look closely at the CFD picture that Woody has provided, it does not address the wheels and their affect on the cars total aerodynamics but if you look at the rear of the car you can see where the air flow separates from the body both on the top and also the bottom. The top is due to the specific aero shape of the body but the bottom shows what happens when you run the car to low. The "perfect" shape would have the air flow be attached to the body for its complete length to minimize pressure drag. The most important part of a lakesters aero are the wheels/tires, how they are connected to the body and their relationship to the body and how their areo may affect the bodies aero.

Sounds like a great project and keep us up to date with your progress.

Rex

Thanks for the link Rex, there is a lot to read there.  What little I saw looked similar to what I'm drawing up.