chassis opinion(s)

[johnneilson]

I know everybody has one,

After having spent years in making cars turn and accelerate, read light and less mass, I am planning on building a BellyTank.
I am not planning on using an existing frame, this is a build from floor up out of tubing.
I do not intend to torsion bar it (front) in fact, I am thinking single leaf front rigid mount rear.
So, for opinions on chassis;
What size tubing? wall thickness?
And why? we have dimensions for roll cage, I am planning 1 3/4" x .120

Fire away!!

speed, dirty 2 is target.

Thanks, John

[Dr Goggles]

Rather than voice an opinion , I'll just tell you what we did, we used the same size tubing all over used 1/4 plate for the firewall, and the floor which is flat. Have seen tanks that "bounce" because of the frame flex, didn't want that to happen.

we're in the build diaries under "Australian Bellytank".....start at the top.....

[jl222]

  With all those years of experience you should know what happens when your wheel rate gets to high.


                JL222

[1212FBGS]

tubing size? wall thickness?.... im thinkin ya might wanna start with a rule book.... especially if ya wanna race it....
kent

[johnneilson]

Hmmm, not much help here.

Yes, actually I have been reading the Australian Bellytank thread. This is one of the reasons for asking. I have notinced many car built with rec tubing for the main rails.
It actually makes sense to run solid mount front and rear axles, I keep thinking along the lines of transition and dampening.

The Rulebook is interesting, it like SCCA has to cover a multitude of different types of cars.
As far as driver protection, yes, I see definate construction. It seems resonable, nothing out of the ordinary.
One thing though, and maybe I missd it, the vehicle weight doesn't factor into the cage requirements (tubing size).
I miss type, yes, if a smaller engine class and speed below a threshhold, lighter tubing.

In SCCA, the requirements depend on the weight of the car, at one time a 4000# car was 2" x.120 tubing.

My initial question was chassis, not roll cage. The latter is easy, the other has many factors.

Thanks, John

[jl222]

  With all those years of experience you should know what happens when your wheel rate gets to high.


                JL222

  Chassis opinion.... If you build a solid suspended car expect a lot of wheelspin from to high a wheel rate.

                                  JL222

[johnneilson]

JL222,

Yes, very true. I have noticed that some tanks have slabs of steel bolted to them to add traction and possibly to balance the car for acceleration and keeping it pointed in the right direction. The ones I have looked at are solid mount rears, and some front suspended. It would almost seem that solid mounting the front and allowing for rear suspension would help in the traction dept.

Thanks, John

[robfrey]

I'm still a bit of a rookie but I like suspension. That being said, I think whether or not it is worth it depend on many factors. What quality of salt will we have over the next couple of years?How much rwhp will you be making?
A belly tanker only makes a little downforce (in theory because of ground effect) so you might need all the traction you can get.

[hitz]

I was going to make my lakester rigid on both ends (cheaper) but looking back many years made me think of my first two motorcycles (both rigid rear.) so I went with a parallel four bar (no instant center) mostly for traction. A small chunk of salt can lift the tire off and just a little compliance will get the wheel back on the ground sooner. The front is different, it's rigid. If the rear is behaving it doesn't have much to do. It doesn't have bump steer but doesn't steer well in the bumps. We don't have bumps on the salt courses any way, do we?

Harvey

[John Burk]

How about De Dion rear suspension like the left image at this link except that the De Dion tube rotates on two inboard tabs with a coilover inside the body with only the tube exposed to the air . The De Dion tube could be a streamlined tubing .

http://www.google.com/images?hl=en&q=de+dion+suspension&um=1&ie=UTF-8&source=univ&ei=2nLbS8m3KZG69QSep8Vn&sa=X&oi=image_result_group&ct=title&resnum=4&ved=0CCcQsAQwAw

[John Burk]

A better link to the view of a De Dion rear suspension

http://www.carbibles.com/images/dediontube.jpg

[hotschue]

Ref. De Dion rear, Having a unit in my vintage racer and made the following observations.  Basically it acts like a straight axle rear, even though it looks independent.  When one side goes up the other reacts in the opposite.  The main advantage is the unsprung weight, it dirt tracks on asphalt with most of your steering input with the right foot. Year of the car is '58, I believe this to be the first 4 link before it caught on in drag racing in the late '60's. Attached a couple of photos when I freshened the chassis in '07. 

[jacksoni]

There are only specs for cage. Chassis is up to you but must only be strong enough to "resist flex or twist". We have seen loosy goosy chassis get booted. Look up the thread on the tank motor powered lakester. My liner had solid front and rear. No ballast. CG ahead of center of pressure. Never had wheel spin. Never got squirrely and went straight even on some rough courses driven by me and subsequent owner even with a blow-out front tire at speed.  Had enough power from 2L engine to go 270+ middle mile still accelerating (about 280-285 est exit speed). Yes other cars lot faster since. Your results may vary.

[dw230]

And yet, that same car got me in the 2 club, regardless of driver talent.

DW

[jacksoni]

And yet, that same car got me in the 2 club, regardless of driver talent.

DW

Shoot, who said anything about talent- driver or builder