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Author Topic: Belly Tank Lakester  (Read 43782 times)
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Peter Jack
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« Reply #30 on: September 02, 2010, 10:51:39 PM »

I'd recommend making the rear track narrower than the front. It will lead to more stable handling, especially under acceleration.

Pete
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dshuken
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« Reply #31 on: September 02, 2010, 11:14:38 PM »

come to think of it, I have heard the same thing about a wider front track width being more stable.  I would be careful to not get too narrow with the track width.  Considering the shape of the bottom of the tank, and how much air can get under it, if you got it a little sideways, or even spun it, having the wheels way out there might be the ony thing that keeps you shiny side up.  Just a thought.
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Dr Goggles
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« Reply #32 on: September 03, 2010, 12:25:12 AM »

come to think of it, I have heard the same thing about a wider front track width being more stable.  I would be careful to not get too narrow with the track width.  Considering the shape of the bottom of the tank, and how much air can get under it, if you got it a little sideways, or even spun it, having the wheels way out there might be the ony thing that keeps you shiny side up.  Just a thought.

On our car we set the track widths the same in the interests of clean aero. There are two arguments as to why a narrow rear axle will keep the car straighter, the drag racing argument that there is less "leverage" on a narrower axle is pretty flimsy when it comes to the amount of traction you have on salt , the gearing LSR cars run and the type of power you guys are talking.The other argument( for which the proper tech escapes me now) is debatable as well due to the limited traction and contact patch.

The wider your track the less likely the turbulance from the wheels is to affect the airflow around the body, the only penalty is a bit of extra axle. If the wash from the wheels disturbs the airflow over the body there's no point in having something as nicely shaped as a tank.

BTW shuken, the tank is lookin good..... cheers
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gidge348
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« Reply #33 on: September 03, 2010, 12:50:24 AM »

On speedway it used to be that the front was wider than the rear.The thinking being that a car will roll forwards ie. usually over front right wheel, the further that was away from the COG the harder it was to lift the remaining three wheels so gave you more stability.

I assume this is the same with drag racing in our sport through it usually a case of the rear overtakes the front and cars roll over the rear tyres so a wider rear may be better?

Go Karts put the tyres in to get more grip and out to get less...... Not sure what this all means but I guess you need to either have the front wider or the back wider or maybe both the same..... huh huh huh   
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Rex Schimmer
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« Reply #34 on: September 03, 2010, 11:20:45 AM »

I have to agree with Doc Goggles regarding both the track width, having the wheels the same width, and having the wheel far enough away from the body so that they do not interfere with the body air stream.

When you build a lakester using a surplus tank, you start with a shape that the government has spent big bucks on to make it as aero perfect as possible and everything you do to it makes it less aero perfect. Also when you have a low powered engine like the V4F motor that you are using you only have a very limited amount of power which will be pretty much the same for all cars in the class.  From the aero side there are a large number of things that can be done to go faster. If you are building this tank to be a "period correct" car then you should proceed with your present path, but if you are looking to try to set a record you probably need to reconsider your aero approach. Your chassis is certainly very well designed and your fabrication great but none of this will have much affect on if the car will go fast. It is horse power vs. aero drag that sets the max speed. You have a pretty well set amount of HPs only having better aero than the competition will make it a record setter.

Rex
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« Reply #35 on: September 05, 2010, 03:35:48 PM »

Rex,
Thanks for the input.  What your'e saying about keeping the front and rear wheels inline for better aero makes sense, if all we were doing is trying to set a record.  However, like you said, we are trying to build a "period correct" car.  I would take it a step further though.  If I was going after a lakester record I wouldn't use a belly tank at all.  Don't get me wrong, I love the look of a 'tank, so don't throw me under the bus yet.  wink  I would build a lakester with a body designed to get air up and over the body, not under it, which I think is a drawback with the tank, since all the air passing below the centerline of the tank is creating lift, however minimal as it may be. Let's not forget that these things were designed to go under an airplane, and affect the plane's handling as little as possible. All that being said, a purpose-built lakester just doesn't have the mojo of a belly tank. And more power to the tank guys who can compete with the "dragster" cars and still set records. What do you guys think?
Daniel
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Rex Schimmer
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« Reply #36 on: September 05, 2010, 06:41:43 PM »

Daniel,
The "clean sheet of paper" lakester design that you are proposing follows the present day thinking of Jack Costella, long wheel base, small frontal area, very low ground clearance and a flat bottom. Jack's cars have been extremely successful as is shown by the large number of records that they hold. I don't happen to agree with all of Jack's thinking and am presently working on a small displacement lakester design that when (and if) built will be more along the lines of a wing tank with some modification to the bottom.

Your statement regarding wing tank cars developing lift , (  not under it, which I think is a drawback with the tank, since all the air passing below the centerline of the tank is creating lift,) is not correct. A wing tank car, if it has sufficient ground clearance will actually generate down force, cause by the air that is going under the car having to accelerate to a higher velocity. (Bernoulli strikes again!) regretfully most of todays "tank" cars are ran with extremely low ground clearance which completely disrupts the air flow beneath the car and can actually completely destroy the aerodynamics of the lower half of the tank.

Rex
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Stainless1
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« Reply #37 on: September 05, 2010, 08:26:34 PM »

Daniel, can't tell from the pics, is the steering rack mounted on the front axle?  or the frame... mounted on the axle well eliminate any bump steer, put a collapsible d or double d slider in the column. 
Just a thought...
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Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
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« Reply #38 on: September 05, 2010, 08:54:32 PM »

Re Stainless' comment.

 The pictures look like the steering mounts to the spring perch and ,as Stainless described, anything other than an axle mount -with proper U-joints and plunge to match the suspension travel, will indeed create "bump steer.

(As clever and knowledgeable as Landracing posters are I won't be surprised that somebody will describe a sytem of links, levers and so forth that will disprove the axle mount being the only solution, HA!).

On the  plus side, what great construction work! But, unless the spring rate is INFINITY,better re- think the steering,
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SPARKY
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« Reply #39 on: September 06, 2010, 12:18:26 AM »

My thoughts on a COMPETETIVE Lakester:

Absolutely the lowest frtonal area as possible and the SMALLEST WHEELS & TIRES!!!


Wide frt axle and a blunt frt nose withbody shape to get most of  air over it as possible

Flat botton with 3 degs of rake for a lot of reasons:

narrow rear axle with exhaust pointed back down the track between the body and wheels over the axle

NO QUICK CHANGE OR FORD 9"


« Last Edit: September 06, 2010, 09:11:20 AM by SPARKY » Logged

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« Reply #40 on: September 06, 2010, 12:57:15 AM »



Absolutely the lowest frtonal area as possible and the SMALLEST WHEELS & TIRES!!!
check

Wide frt axle and a blunt frt nose withbody shape to get most of  air over it as possible
check
Flat botton with 3 degs of rake for a lot of reasons:
check
narrow rear axle with exhaust pointed back down the track between the body and wheels ovwer the axle
same width and with the tailpipe straight out the rear here,....

NO QUICK CHANGE OR FORD "
Thanks to our man in arizona wink we're getting there...

Building a lakester involves a lot of compromises, Sparky has obviously made some smart decisions and has hats to prove it.

BTW Bill I tried to ring you yesterday cheers
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Few understand what I'm trying to do but they vastly outnumber those who understand why...................

http://thespiritofsunshine.blogspot.com/

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« Reply #41 on: September 06, 2010, 09:13:33 AM »

sorry I missed the call
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Miss LIBERTY,  changing TKI  to noise, dust and RUST!!!

The # 1 issue is: TO KEEP THE REPUBLIC      
   Center for Self Governance            tncsg.org     mrspowell.org

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller
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« Reply #42 on: September 06, 2010, 11:21:58 PM »

Rex,
 The reason most of the tank cars out there, including mine, are so low is that unless you run a huge rear tire, the rear end hangs so low that the tank cant come up any higher.  you could always notch the bottom of the tank, but that would kind of defeat the purpose.  If you raise the tank for aero, you also raise the CG.
Stainless,
Yeah I did mount the rack to the chassis, but steering is still in the experimental phase.  I did think about mounting it on the axle, and use a slider shaft to eliminate the bump steer, but with the space available it just worked out better that way.  The thing that i hope will save me is that in my experience, with enough leafs in the cross spring, there is only about a half inch of trravel.  I just got the chassis on wheels today, so i will check the bump steer situation and let you guys know how it turns out.
« Last Edit: September 06, 2010, 11:29:07 PM by dshuken » Logged
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« Reply #43 on: September 07, 2010, 06:14:11 AM »

Sparky, What type of rear do you think is the best to use in a tank, I am getting ready to purchase a quickchange but if there is a better alternative I am all ears for someone with past experiences.

Thanks,

          CJ
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SPARKY
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« Reply #44 on: September 07, 2010, 07:17:11 AM »

Depends what you are running for drivetrain  and where and how you plan to run---

there is an extended thread about rears in the archives

Rex I would say that it is about TOLTAL drag reduction--Aero is the largest one

It remains the combination that produces the greatest tractive effort to the salt, with the least amount of drag that one can keep together for the required number of passes. 

There are combos that are better in one area but may not be the best choice 

I just happen to feel like air shifted trans and quick changes fall into that category

A lot of people or suprised when they learn that I run an auto, no tq converter and a stock valve body
« Last Edit: September 07, 2010, 07:31:10 AM by SPARKY » Logged

Miss LIBERTY,  changing TKI  to noise, dust and RUST!!!

The # 1 issue is: TO KEEP THE REPUBLIC      
   Center for Self Governance            tncsg.org     mrspowell.org

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller
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