Uni-body Cars?

[ZZZBrahmaBull]

On the uni-body cars,is there such as frame connectors?To race one you would be absolutly crazy not to make the frame and chassis one complete solid unit for safety the main reason.Even for a street hot rod like an F Body Dodge Aspen.I can feel the body sort of twist if i really give it the gas around 80mph.I suppose you could do custom fabrication modification to make it solid,safe and secure?

[Truck99]

Most people who build a circle track car using a unibody chassis tie the front and rear subframes together. I've seen it done many different ways, so that part is open to the imagination. There are aftermarket connector kits, but the ones I've seen done from scratch appear to be much stronger.

[jwmbishop]

Most of the kits available are targeted for the street rodder so are not as strong as some homemade stuff I have seen either. Some track rules preclude connecting the subs directly - especially in the pure stock classes. But the cage can be constructed and triangulated in such a way that is creates most of the center section rigidity you want for handling without giving up much (if anything) in safety. From a safety perspective rigidity does not equal safe! As long as your driver area does not crush the more absorption you get in an impact the lower the g forces applied to the driver's vital organs.

 

You think you can feel that Aspen twist? I put a 427 BBC in a 72 Vega GT - on the third pass it exploded the back and one side glass out when grabbing second (and left it with about three inches of wedge in the body)! And that was WITH a connector kit and six point cage!

[4cylfordz]

I race unibody cars. usually after connecting the subframes with some sort of square tubing, we also use a bottom rail in our cars. like instead of welding the cage to the floor we'll take square tube and run it bumper to bumper following the path of the sub frame and welding it completely down building like a false frame then building the cage off of that. stiffens them up quite a bit.

[bret90]

I like to make a perimeter frame and use straight subframe connectors, both using 3x1.5" .083.

[thumper]

If you are building a big block drag car.build a complete frame and chassis,then add the body.For an oval car,the cage does add the needed strength.To me its important not to damage the integrity the factory put in.For a full sized car the connectors and cage should be designed to work with the factory chassis.The unibody is lighter and gets strength from the shape of the metals rather than the mass.For a smaller car I like to make the mounting points for the cage in a double sheer design.I put in the L shaped plate,then hole saw a hole through the side and through the rocker.I install a pipe through the hole,then make a plate for the outside of the rocker.I form the outside plate to the rocker,weld the pipe to it and trim the excess.With everything welded together you would have to completely rip out the rocker to pull the cage off like a T bone could do.Then I build the cage as close to the body as possible and weld the cage to the body at every oppourtunity.I build in a crash zone at each end of the car for deflection.Its easier to replace one end of a car than a complete chassis that bent in the center of the car.Theres no such thing as a crashproof car.

 

Chassis deflection is a safty issue as well and probably the most important issue.The asphalt modifieds of a few years back were killing their drivers with cars that could have been repaired in the pits and raced again that nite.The chassis was so rgid,all the energy was transmitted to the driver while the cars had local damage only.

 

Another point,on pavement a rigid chassis is more desirable because the track is consistant.On dirt some chassis flex is desirable to be more forgiving on an inconstitant surface.The reason is the more rigid the chassis,the more accurate the chassis tuning has to be.You will not notice a 50 pound spring change on a flexable chassis but you will on a rigid one.

 

On the main cage I always add a retangular tube across the floor to tie the main loops behind the driver to each other and weld the center hump.Adds lots of strength to side deflection and gives me something strong to build my seat mounts off of while giving a place for belts.My cars are strong and light and safe for the driver.Just be careful about whacking out the factory strength aeras.It doesnt make the finished product safer.Just add to it.

[ZZZBrahmaBull]

Ok Thanks Guys for all that info.Yeah I know its a lot more to know in the structure engineering than I will ever know.Since I saw the article in Circle Track and can still find it on the web.How to make a street stock safer.They reenforce the frame.So I assumed it be the same on a unibody.But didn't know too much rigid could kill.But yeah makes sense since energy will travel the path of the least resistance which is the driver.Energy has to go somewhere.My fear of unibody breaks in 1/2 on impact without any fabrications.

So on dirt chassis like bamboo,bends but don't break,now I know.I read somewhere in drag racing to get your car to lunge forward hard off the line make the chassis as rigid as you can.Shatter the rear windshield?Yep saw that back in the 70's Victoria Texas .Think it was a 76 or 77 Coronet,not sure 426 or 440.The rear window just exploded on take off.Well once again Thanks Guys for the input.Sure don't want to make a death trap at the same time trying to make it safer.When in doubt,Stop,and ask.

[JamesHigdon]

To add a few things I hadn't seen mentioned here; welding the seams in the uni-body along with using a large plate where the bars meet the chassis can add some much needed strength to the chassis. In road and drag racing it is not uncommon to seam weld the stitch welds throughout the unibody for added strength to the main tub. The cage to chassis points should be mounted with a large formed and seam welded plate, this will keep the cage from pulling or pushing through in a hard hit.

[ZZZBrahmaBull]

To add a few things I hadn't seen mentioned here; welding the seams in the uni-body along with using a large plate where the bars meet the chassis can add some much needed strength to the chassis. In road and drag racing it is not uncommon to seam weld the stitch welds throughout the unibody for added strength to the main tub. The cage to chassis points should be mounted with a large formed and seam welded plate, this will keep the cage from pulling or pushing through in a hard hit.

Got another question in same area of the car.Tail pipes on 70's Mopars.One side is no problem.But other side,got the gas tank right in the way.Only options are run them out the sides forward of the rear tires,maybe the best.Or both pipes out the back on same side.I hate that one.Or take out fuel tank,put fuel cell in the trunk.But then no gas guage.Now if I was an engineer I could maybe design something that would work.Like have 2011 windshield wipers on 70's car.Man would that be nice.Anyway the guys that design and fabricate the NASCAR chassis and all the other stuff in the cars.Can only wish I could be just a little bit as good as they are.

[HiTech]

why would you not have a gas guage.... its a two wire system ..easy to make the guage work with a fuel cell ..you can buy cells fitted for sending units ..

[jwmbishop]

got the gas tank right in the way.Only options are run them out the sides forward of the rear tires,maybe the best.Or both pipes out the back on same side.I hate that one.Or take out fuel tank,put fuel cell in the trunk.But then no gas guage.Now if I was an engineer I could maybe design something that would work.Like have 2011 windshield wipers on 70's car.Man would that be nice.Anyway the guys that design and fabricate the NASCAR chassis and all the other stuff in the cars.Can only wish I could be just a little bit as good as they are.

Route the exhaust into the gas tank and you would have pressurized delivery and can throw away the fuel pump saving $$ in the long run.

 

we ran the exhaust out in front of the tires once. Overheated right Rear tire and did not realize that the hot exhaust coming back off the wall going down the straight was our problem until after chasing non existent suspension problem for three weeks.

 

my preference would be to relocate fuel cell away from exposure anyway.

[ZZZBrahmaBull]

Thanks HiTech.Was wondering if I be able to make something work like that.Then a 30gal fuel cell in the trunk that will work.Will do that in the Aspen & Road Runner when I have the frame mods done.Like Bishop says less exposure.Living down 3 miles of rough gravel road everything from gas tank to exhaust get beat up with rocks.Lost couple tanks of gas from that.

[jwmbishop]

An RCI aluminum 15 gallon with sender runs right around 200 - the 20 is 300. kinda worth it imo.

[HiTech]

An RCI aluminum 15 gallon with sender runs right around 200 - the 20 is 300. kinda worth it imo.

yep thats the way to go ......jw .ive been down his three mile road .it aint no smoothy ..aboult beat us to death getting to his land ..in a pickup to say the least ....he didnt tell you he hauls the mail down those roads did he .cars need skid plates . duke of hazard typ thing ..lol

[jwmbishop]

Sounds like the City "streets" here in Corsicana!

[ZZZBrahmaBull]

An RCI aluminum 15 gallon with sender runs right around 200 - the 20 is 300. kinda worth it imo.

yep thats the way to go ......jw .ive been down his three mile road .it aint no smoothy ..aboult beat us to death getting to his land ..in a pickup to say the least ....he didnt tell you he hauls the mail down those roads did he .cars need skid plates . duke of hazard typ thing ..lol

Been there since 85 dealing with that road.Its 11 miles the other way and rougher too.Thats were I developed my love for driving on dirt.

Freshly graded and smooth, 70 to 85mph no problem.Like HiTech says Bo & Luke Duke and sort of like Shady Oaks.Why the neighbors called the Sheriff Dept on me.Why I bought a Street Stock or go to jail.

[scopx]

Sounds like the City "streets" here in Corsicana!

 

You are preachin' the Gospel about the streets of Corcicana. I really hate it when pulling my wide gooseneck trailer through there as width tad wider than those chunked outside lanes on 31. Got caught on the outside lane with car on inside. To maintain without hitting car, had to put the sidewalls of the right side tires so close, they were were squalling on the side of concrete curb.

Last time I was through they had one lane partially blocked off. (Usually try to make trip late at night to avoid all the drama.)

Sorry to get off track here.

[jwmbishop]

And as hiway 31 gets state money its one of the best roads in town! Currently in middle of project to install drainage tunnel underneath. A real mess to avoid!

 

My mother lives in the Purdon bottoms - 3.4 miles of dirt road from one direction (for the first six years she lived there it wasn't even gravelled past the first 1/4 off the highway so we parked and trudged across the pasture if it even looked like rain). I moved out here for the last two years of high school and drove a 72 Nova SS down those back roads. My bud and I played starsky and hutch many a night. After one summer that car looked like a well hammered and straightened street stocker. Bondo is for sissies - leave the wrinkles they add character - lol.

 

I learned a very important lesson one night. A 4800 lb car travelling 60 MPH as it goes over a 6 foot elevated train crossing will fly approximately 75 feet. And those landings we see in the movie pretty much end a cars life - which is why there is money to be made in prepping cars for shows. They usually need 8-10 identical cars to film a movie like dukes! A good lesson indeed - which is why in 85 I jumped at the offer to work at McBurnie Coachcraft making the kit Ferrari (Corvette platform) they used on miami vice series. Of course that one did not get beat up so they only used three cars - two set and one show (the show car was NICE - GB twin turbo on a then new engineered 350 TPI - aka ramjet). The GTO they rolled on Knott's Landing was also one of ours (280Z platform with a big block chevy option) - they got two, one complete and one just a shell with roll cage - they cable pulled it to get it to roll.

[ZZZBrahmaBull]

JW I had bought a Yellow 68 Dodge Charger off ebay in 03.The car was a Hollywood Stunt Car.Used in a mock explosion scene.The 383 I have in my shed is out of that car.Car came from Santa Rosa Ca.Can't remember the series and movie the car had been in. I sold the car as a roller.You ever saw that car?What about a Street Stock with wrinkles and bullet holes????Street Stock like that that is street legal sure be fun.Get lots of looks.

[jwmbishop]

Cool - did it have the charge ring under it? (its a steel ring welded to the underbody to lift that side for a roll over - if you watch stunts closely you can see them in action)

 

Bullit used a yellow 68 383 (painted black and trimmed as an R\T 440 for the movie), Dirty Mary Crazy Larry used two 69's and a 68 (the black strip was not factory sticker job - was hand painted by the film crew) but these had 440's in em and all are accounted for. They do the swap up a lot to keep the rare car out of trouble - think Nash Bridges. That set car did not start life as a hemi cuda vertable. It was a hard top slant six. Did not stop it from selling for 1.1 mil (Mr Johnston was there at the auction and when bidding slowed down at 675 he got on the mike and said "You know this aint a real Hemi Cuda - but it's wotrth MORE as my ass has been in that"! Bidding took back off.

You might find it here: Link to Movie Mopars

 

When I worked for Tom McBurnie getting cars ready for a show usually meant two - one on the roll back and one on a trailer - this was his guys rolling out in "08

[ZZZBrahmaBull]

Cool - did it have the charge ring under it? (its a steel ring welded to the underbody to lift that side for a roll over - if you watch stunts closely you can see them in action)

 

Bullit used a yellow 68 383 (painted black and trimmed as an R\T 440 for the movie), Dirty Mary Crazy Larry used two 69's and a 68 (the black strip was not factory sticker job - was hand painted by the film crew) but these had 440's in em and all are accounted for. They do the swap up a lot to keep the rare car out of trouble - think Nash Bridges. That set car did not start life as a hemi cuda vertable. It was a hard top slant six. Did not stop it from selling for 1.1 mil (Mr Johnston was there at the auction and when bidding slowed down at 675 he got on the mike and said "You know this aint a real Hemi Cuda - but it's wotrth MORE as my ass has been in that"! Bidding took back off.

You might find it here: Link to Movie Mopars

 

When I worked for Tom McBurnie getting cars ready for a show usually meant two - one on the roll back and one on a trailer - this was his guys rolling out in "08

It had lots of 1/4 flat metal plate welded in it,under the hood and inside the car on the roof.The inside was all burned from the explosion.The doors were sprung from the ram that blew them open.I saw a ring somewhere.Bought the car for 900,sold it 700 kept the motor/trans.That guy said he will try to restoe it.Haaaa best of luck.Series?Fast Lane?Not sure.Motor got burned too.

HITech: Well its not quiet The Lucas Oil Off Road Series to get to my place.Man now that be nice if the Series was nearby here.Love those trucks.Now thats racing.