Landracing Forum
Tech Information => Steering - Suspension - Rear End => Topic started by: ROCKZOMBIE on July 08, 2011, 10:10:41 AM
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My Tanker chassis and shell is complete. I know I will us a Ford 9" at the rear and will build the swing arms and coil over suspension myself. My question is, I hear a lot of you mention the VW rack and pinion, seems the ratio and price is right. What part # would I order the R & P under? I also intend to use the same coil over system up front with the same 2 1/2" of travel and I would prefer to go from spindle to spindle with a straight Axel set up for ease of fabrication and strength. I will be running the heavy 18" steel wheels with 30" meats, so I am looking for good strength in the whole set up. I am in no way a front end specialist so I would appreciate any input to this set up, I'm sure I'm not into anything new or different here, just never built one before and want to get it right first time. Thanx :cheers:
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Why the use of 30" tires in front?
DW
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Of course I realize the cost sufferance in the tall tires, I just happen to believe all tires the same is more stable at speed, I prefer the nostalgic look of the old Tall Wheeled LSV, but what would U'r suggestion be?
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30" tires put the front spindle centerline off the ground at 15" Thats a lot of ground clearance. If you follow the school of thought that a lot of under body clearance is a good thing then that is OK.
What engine class are you running? $750 per/tire is a lot of money to spend for a H class car..
DW
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:-o If you want to be anywhere NEAR competetive you should have nothing any larger on the frt than a 21" and a 23" on the rear. YMMV
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Sparky, The NASCAR tires would be a good choice
The H class record holder
:evil:
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Thanx guys. 1st off I will have only 3'' of ground clearance under the lowest section of the tank (the 4' long by 32" barrel shaped extension.) Considering 2 1/2" of suspension travel ( 1"+ up 1"+ down) This is my rough in layout for now. As for the bullet, AA/F Blown Alcohol, already got it. Now for final gear ratio, Mark at Pro Gear says, and I tend to agree (thou my knowledge of all this is purely conjecture and Zero experience) with all things considered and factored in togeather, considering engine horse power and RPM shift point, transmission gearing and overdrive ratio, then factor in ring and pinion ratio seems like the tall dia. drive wheel comes in pretty comfortable at 30". Now, after driving a 800 H.P. blown 440 Challenger in the streets for 15 years and a good bit of drag racing and being a chassis and rear end fabricator, it's easy to see why I chose to complete the entire chassis and shell on my tanker and leave the rest of this till last. Sure I can run a lower height front tire, just place the axle lower. But what about a 'cower catcher' type front spoiler scrapping the ground and shooting as much air as possible out to the sides, But aren't drop tanks designed to 'Fly' better because of equal pressure on all sides? Also, after considering axle location and tire height, what would be a good rake on a 24' tank with a 13' 6'' axle to axle length? I was thinking of 2'', this is in conjunction with front and rear down thruster wings. I will post picks when I get the hang of this photobucket program that Slim was good enough to send me. It's a real sweet tank. be worth lookin at. Oh. got my smoked canopies today from Todd's Canopies. Great guy, Great price, great quality. and ZERO visual distortion! Keep the info comin guys, I really appreciate it.
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dw, how do you figure to much air flow under a tank, u know, the one with the pointie fronts and rears, doesn't matter What dia. tire or where you mount the axle end result is The Center Of The Tank Is Always Gonna Be Lower Than The Front Or The Rear! Wouldn't want to run this thing with the lowest point being under the salt, down below the dirt line. Just Sayin.
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PM message sent
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with the pointie fronts and rears, doesn't matter What dia. tire or where you mount the axle end result is The Center Of The Tank Is Always Gonna Be Lower Than The Front Or The Rear!
Hummmmmm......
Well, it sure matters that rotating cylinders outside of the body lines cause a significant level of drag, and placement of the axles fo. and aft will also affect directional stability.
I think pics are in order.
~JH
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Yeah, I got pics but downgrading em to the required size to load here seems to be a hassle, Typical 32''dia by 24' tank with the engine totally enclose with only a slight rise in the shape for the driver canopy and the zoomie stubs protruding, a tail rudder, downthruster wings, looks pretty darn slippery to us but am wondering about any or no air flow under the 2 1/2" -3" ground clearance at the lowest point of the tank profile. To bad pics always seem to be the hardest thing to on these sites.
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The back of my flat bottom was 4.5 " 1.75" at frt splitter with 21/24.5" tires.. How long is the straight section of you car?
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I happen to be one of those that believe a tank should have enough ground clearance to allow undistubed airflow underneath the car. This requires at least 3-4 inches of ground clearance and if done correctly this accelerated air flow if allowed to remain attached will generate some aero down force with a very efficient drag to lift ratio. When you run a tank low the boundry layer on the bottom of the car thickens the farther back on the car and if it interferes with the ground plan it can cause the air to become unattached from the body and create turbulance along the lower part of the tank at the rear which greatly increases the cars pressure drag. If you look at some of the aero reference books, "Race Car Aerodynamics" by Katz is pretty good, he talks about a percentage of the total lenth for minimum ground clearance, I don't happen to have his book handy but I think I remember for a tank shape it is between 3-5% which in your case would be around 6 inches. minimum.
How far from the body are you mounting the wheels? Using a good front axle set up with some aero shouding can be pretty efficient for a lakester.
Rex
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I happen to be one of those that believe a tank should have enough ground clearance to allow undistubed airflow underneath the car. This requires at least 3-4 inches of ground clearance and if done correctly this accelerated air flow if allowed to remain attached will generate some aero down force with a very efficient drag to lift ratio. When you run a tank low the boundry layer on the bottom of the car thickens the farther back on the car and if it interferes with the ground plan it can cause the air to become unattached from the body and create turbulance along the lower part of the tank at the rear which greatly increases the cars pressure drag. If you look at some of the aero reference books, "Race Car Aerodynamics" by Katz is pretty good, he talks about a percentage of the total lenth for minimum ground clearance, I don't happen to have his book handy but I think I remember for a tank shape it is between 3-5% which in your case would be around 6 inches. minimum.
How far from the body are you mounting the wheels? Using a good front axle set up with some aero shouding can be pretty efficient for a lakester.
Rex
I'm not trying to get under your skin here Rex.
We have a dog in this fight. We have a history of disagreeing with Rex about this specific issue. I will leave the math to the Reverend:
http://www.landracing.com/forum/index.php/topic,862.23.html ( go to reply 23)
We went low for a number of reasons and we aren't afreaid to admit some were cosmetic, some were for safety( lowering the vertical COG).
I have a gut feeling that the term "interfering with the ground plane" is a little misleading as it indicates that the air is moving when it isn't.
Typical 32''dia by 24' tank with the engine totally enclose with only a slight rise in the shape for the driver canopy and the zoomie stubs protruding, a tail rudder, downthruster wings, looks pretty darn slippery to us but am wondering about any or no air flow under the 2 1/2" -3" ground clearance at the lowest point of the tank profile.
I am of the mind that the zoomies (see this topic: http://www.landracing.com/forum/index.php/topic,9912.0.html ) may be a more significant factor than the ride height in what you are trying to achieve. The "downthruster" wings will certainly add drag. Your decision with them is "do they create a degree of drag that is outweighed by the increase in thrust we can apply to the track"
It's fun this....................
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Doc Goggles,
You make it sound like we are at each others throats!!! over this. We just happen to have different thinking. Re-reading the Rev's post the reasons that he has given for your cars configuration are very understandable, and I still think that your tank is one of the best lookingt around. I love low cars, my little A modified roadster that I take to the salt is only around 3 inches off the ground, I just don't think that a tank should be that low. The car that I am presently working (?) on will be built with about 6 inches of ground clearance at the lowest point and will not have a "cambered" bottom. This is the great thing about this type of racing we can all try our ideas and if they work we can give ourselves a big pat on the back, if they don't we can always go back to the drawing board!
Regarding your statement, " I have a gut feeling that the term "interfering with the ground plane" is a little misleading as it indicates that the air is moving when it isn't." What interfers with the ground plane is the boundry layer of the car as it thickens the further back you go on the car , especially when it transitions from laminar turbulant flow. The ground plane is not moving and therefore does not have a boundry layer.
Hope to see you at the salt soon.
Rex
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.....Sorry Rex, I didn't mean it to sound like that..... but I thought that recently it may have sounded like I was following you around disputing everything you said...
I will be at Speedweek,no I won't be bringing my copy of Goro Tamai's "The Leading Edge" ....Meanwhile you can introduce me to your pals as the unreconstructed hick from somewhere you can't get by bus.......
Viva landracing.com!
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RZ where did you go :? All I was trying to say is Tires are usually a big part of the total drag on a lakester if you can make them work for you I am planning on those speed ranges with 23 and 24.5 & 26" rear tires FOR B'ville with a GM 7.5" 10 bolt rear end. I dont run on pavement.
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Sparky - and all:
Where'd Rockzombie go? might be part of the problem that surfaced here today. He's been demoted to "guest" status by some quirk in the site's hosting hardware - I think. He and at least two others of which I know got that "demotion" overnight last night. One of the newly-disenfranchised folks emailed to me to ask of the change. I didn't do anything - really!
But I've once more asked Dan, the host company guy, to see what the heck is causing these farkles.
Sorry for the inconvenience. Really. :cry: