Author Topic: Belly Tank Build Diary  (Read 361808 times)

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Offline ronnieroadster

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Re: Belly Tank Build Diary
« Reply #165 on: August 03, 2016, 09:43:56 PM »
A photo of the pedals installed in the car.  The next step is build a foot box.  The car weighed in total at 2,426 pounds with 1,045 pounds on the front and 1,381 pounds on the rear.  I plan to build the foot box from 11ga steel in an effort to get more weight up front.  I would like to start with a 50:50 weight distribution.  The throttle pedal is the factory drive by wire system that came with the engine controller. 


  For a better handling car the weight distribution should be determined based on the center of pressure location from the rear axle center line. Once the C/P location is know the center of gravity location must be in front of the C/P by up to six inches. The amount of weight needed on the front axle might be less than your 50/50 idea.
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Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #166 on: August 04, 2016, 09:15:57 PM »
I estimated the pressure center using a calculator found on the Landracing forum (http://www.mh-aerotools.de/airfoils/software.htm).  This calculator estimates my pressure center to be about 4" behind the center of the wheel base.  To move the CG to 6" in front of the pressure center will place the CG 2" in front of the wheel base center.  This will require slightly more weight on the front than the back.  This will be more than the 336 additional pounds to the front end that I estimated for a 50/50 weight distribution. 

Offline John Burk

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Re: Belly Tank Build Diary
« Reply #167 on: August 04, 2016, 11:43:55 PM »
Hang a model from a thread and blow air at it . You may be surprised how far forward the CP is .

Offline Interested Observer

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Re: Belly Tank Build Diary
« Reply #168 on: August 05, 2016, 08:32:51 AM »
Mr. Brown,
The aerotools calculator appears to operate on an area-weighted basis and for an aircraft uses the planform layout.  Was your result also based on planform or, more appropriately, a lateral profile form?  Or, perhaps a modified partially yawed profile that includes both front wheels? 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #169 on: August 05, 2016, 11:27:12 AM »
Mr. Brown,
The aerotools calculator appears to operate on an area-weighted basis and for an aircraft uses the planform layout.  Was your result also based on planform or, more appropriately, a lateral profile form?  Or, perhaps a modified partially yawed profile that includes both front wheels?  


For the first attempt (and not knowing much about the software) I took a photo of the car from the side perpendicular to it.  I used Photoshop to "cut" the car out, imported the image and pressed the button to analyze.  If there is a better methodology I am open to it.  

Thanks for your interest in my project. 

Mike Brown

Offline Rex Schimmer

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Re: Belly Tank Build Diary
« Reply #170 on: August 05, 2016, 03:19:27 PM »
Mike,
Are you including your weight when you do your CG calculations? Just a thought as if you put my fat a$$ in the drivers seat I would bet you would not need to add front weight! Good reason I'm not a driver!

Rex
Rex

Not much matters and the rest doesn't matter at all.

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #171 on: August 05, 2016, 03:42:58 PM »
Mike,
Are you including your weight when you do your CG calculations? Just a thought as if you put my fat a$$ in the drivers seat I would bet you would not need to add front weight! Good reason I'm not a driver!

Rex

A good question.  Yes I did get the weight while in the car.  I was able to borrow four wireless electronic scales from the local Porsche club to weigh the car.  This allowed me to get simultaneous weight from each corner of the car while sitting in it.  The scales are amazing.  I contemplated gaining 300 pounds for ballast but decided against it when I realized that I didn't want to buy another fire suit.  So the ballast will be metal either steel or lead or both. 

Mike Brown

Offline krusty

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Re: Belly Tank Build Diary
« Reply #172 on: August 23, 2016, 04:38:06 PM »
Tungsten! The favored weight of racing teams with more than decent budgets!  At 1204.41 #/cu.ft., you could layer your helmet with Tungsten (0.069699635 #/cu.in.) and still fit in your drivers suit. If you need front weight, consider Tungsten sole plates on your driving shoes. The possibilities only end with your budget!   :mrgreen:

vic
« Last Edit: August 23, 2016, 04:41:27 PM by krusty »

Offline Rex Schimmer

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Re: Belly Tank Build Diary
« Reply #173 on: August 23, 2016, 06:21:16 PM »
Vic,
You old grouchy old "fart" you got to many zeros, it should be .695 lb/cu.in. so it is about 7 times heavier than aluminum and 4 times heavier that steel and about 1.7 times as heavy as lead, but the price is around $75/lb in round bar form and a pound of tungsten is only about 1.4 cu. in. so you dont' get much for your money.

Rex
Rex

Not much matters and the rest doesn't matter at all.

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #174 on: August 24, 2016, 07:30:09 PM »
The factory drive by wire gas pedal did not well in the foot box.  The plastic factory pedal attached to the throttle sensor with a knurled pin.  I replaced the factory pedal with a new one that I fabricated.  The round disk is an exhaust valve from a 1955 Chrysler Hemi. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #175 on: August 24, 2016, 07:31:48 PM »
I fabricated suspension link retainers from 1/4" stainless steel.  They are secured inside the panel with a clamp collar and cotter pin. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #176 on: August 24, 2016, 07:34:37 PM »
When you first don't succeed read the directions.  I soaked the exhaust wrap in water overnight (in a zip lock bag) per the instructions and was able to successfully apply the exhaust wrap to the tail pipes of the car. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #177 on: August 24, 2016, 07:38:51 PM »
Tungsten! The favored weight of racing teams with more than decent budgets!  At 1204.41 #/cu.ft., you could layer your helmet with Tungsten (0.069699635 #/cu.in.) and still fit in your drivers suit. If you need front weight, consider Tungsten sole plates on your driving shoes. The possibilities only end with your budget!   :mrgreen:

vic

Well the tungsten possibility ended quickly with my budget.  I added (3) 50 pound rectangular blocks of steel and will be rechecking the CG this weekend.  I would really like to make an initial pass at National Trail dragstrip in Hebron Ohio before going to the Ohio Mile in Wilmington Ohio for the last race of the season. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #178 on: August 26, 2016, 09:12:47 PM »
I like to use safety wire on critical fasteners used in assemblies like suspension.  I am adverse to drilling 1/16" holes 1-1/8" deep through the heads of grade 8 bolts.  I prefer to drill through the corner of the hex.  This same methodology can be used for nuts.  I purchased a drill jig for this purpose but was not satisfied with the results.  I broke too many drill bits ruining expensive bolts.  I came up with a successful methodology using my milling machine.  I find the edge of the hex point and move into the bolt 1/8".  I mill a flat using a solid carbide two flute Kennametal end mill which makes a flat.  I then step back another .020" and drill a 1/16" hole using a Guhring parabolic flute drill bit.  I have drilled over two dozen holes without breaking a bit.  I keep the speed down to 1,500 rpm and use synthetic gear oil to lubricate both the end mill and drill bit. 

Offline Mike Brown

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Re: Belly Tank Build Diary
« Reply #179 on: August 26, 2016, 09:13:47 PM »
A photo of drilling the 1/16" hole in a nut.