Results 1 to 9 of 9

Thread: Aluminium Chassi

  1. #1
    Junior Member
    Join Date
    Jan 2012
    Location
    Italy
    Posts
    17

    Aluminium Chassi

    Anybody have experience in building aluminium chassi ? I'm evaluating to build my chassi by using square aluminium extrusions but I'm little bit concerned about brakets for mounting engine, control arms, shocks..... If I use stainless steel for brackets I need to find out the best way to bolt them to the extrusions.

  2. #2
    Senior Member
    Join Date
    Apr 2010
    Posts
    398
    Call Fran Hall at RCR cars. He has built aluminum frames and can tell you what works.

  3. #3
    Junior Member
    Join Date
    Feb 2012
    Posts
    15
    I built an aluminum chassis using C5 parts to create a little Hot Rod. I fabricated all of the brackets out of aluminum. Aluminum is lighter but not as strong. When you weld it it weakens. So, you need to use larger diameter material and thicker to have the equivalent strength as steel. Ideally you would heat treat the chassis after it was welded. You also have to worry about corrosion. In the end my "overbuilt" frame ended up being almost the same weight as an equivalently built steel one. All of the frames that I build now are steel. Here are a couple pictures of my chassis and car.






  4. #4
    Senior Member
    Join Date
    Feb 2005
    Posts
    611
    there you go something different, nice

  5. #5
    Junior Member
    Join Date
    Jan 2012
    Location
    Italy
    Posts
    17
    very nice chassi. What size of tube did you use ?

    Also, do you have a close up picture of control arms mounting points ? I still don't know if would be better to weld a aluminium braket or bolt a stainless one.

  6. #6
    Junior Member
    Join Date
    Jan 2012
    Posts
    28
    Quote Originally Posted by jmc View Post
    I built an aluminum chassis using C5 parts to create a little Hot Rod. I fabricated all of the brackets out of aluminum. Aluminum is lighter but not as strong. When you weld it it weakens. So, you need to use larger diameter material and thicker to have the equivalent strength as steel. Ideally you would heat treat the chassis after it was welded."
    John, just wondering about a few things you wrote from a mechanical engineer's perspective...

    "Aluminum is lighter but not as strong."

    True, but alloys like 6061 and 7005 do have high strength.

    "When you weld it it weakens."

    The same can be said of any metal so aluminum is not exclusive in this regard.

    "So, you need to use larger diameter material and thicker to have the equivalent strength as steel."

    Aluminum weight is about 1/3 that of steel. Strength and stiffness increase significantly with an increase in tube diameter. Using the same material, tube thickness goes down as diameter increases to result in the same strength with less weight. So a large diameter aluminum tube ends up weighing significantly less than the steel version.

    "Ideally you would heat treat the chassis after it was welded."

    What kind of heat treatment? I know that 6061 has to be liquid cooled but 7075 can be air cooled.

    I am asking these questions because I plan to build a round tube aluminum frame. Off the top of my head I was thinking something like 2" diameter tube. That is as far as I have gotten so any additional information you can provide would be helpful.

    For my Pro Mod drag car, tubing diameter and thickness are controlled by the rules. Mild steel must be thicker and can be MIG welded. Thinner Chrome Moly tubing (which my frame is made of) is allowed but it must be TIG welded. Apparently whoever came up with the TIG requirement must have been asleep in his mechanical engineering class because there is no advantage to TIG over MIG as far as strength does. Chrome Moly should be heat treated after welding no matter what welding method is used and no one heat treats it after TIG welding so the weld method is a moot point. Besides, the new rules require the use of gussets so the heat affected zone from the weld now becomes less critical and the method of welding even more so. My Pro Mod is torn down now because the chassis certification expired and I am adding the tubing and gussets required by the new rules. I even have to cut out and replace tubes on the passenger side with larger diameter ones due to the new rules. A big PITA but, the rules are the rules... ;^(

    BTW, do you race those cars? If so, what type of racing and where do you race?

    Jack

  7. #7
    Senior Member
    Join Date
    Nov 2008
    Location
    Detroit , Michigan
    Posts
    108
    Hi John,

    Nice to see you here....

    sorry but I completely disagree about using aluminum for chassis construction...when done correctly its a superb medium for building with ...in fact its so good that Ferrari has chosen to continue using it instead of following the trend of using Carbon fiber...like McLaren and Lamborghini...(I now have an Ex Mclaren engineer on staff at RCR btw)

    This weeks Autoweek magazine even features an article on page 7 titled "Arguing for Alumninum"

    Corvette, Ferrari, Audi, Maserati, Bentley, Aston Martin, Lotus and many more high end cars use welded, glued,cold metal transfer( friction fused), riveted aluminum for their chassis construction....and not to mention that we at RCR/Superlite have built close to 300 cars ALL with aluminum construction and we race our cars, with no failures so far...we even won the NASA Super Unlimited National Championship class in 2011....against Vipers, Porsche Twin Turbos etc etc ...with an aluminum chassised SL-C.......In fact at the Run and Gun event three/four years ago, you and I even had a conversation about RCR possibly manufacturing chassis for you...in Aluminum........??

    I bet you still fly in commercial airliners...made from aluminum...right???
    Attached Images Attached Images  
    Last edited by RCRFRAN; 02-05-2012 at 08:23 PM.

  8. #8
    Junior Member
    Join Date
    Feb 2012
    Posts
    15
    Jack, Fran is certainly qualified to speak to the use of aluminum. His aluminum chassis are works of art. In no way did I mean to disparage his cars. He is the person to answer your questions.

    I built the aluminum frame with 2 by 4 tubing for the rear clip. The perimeter framing is 2 by 2. Both are 1/4 inch wall. The tubing is T6-6061. The trans tunnel, foot boxes, and bulkheads are 1/8th sheet. All welds are tiq welded. The panels are 100% welded along all seams. The Vette suspension cradles bolt into the frame.

    I duplicated this frame with mild steel (Thinner) tubing, skinned with aluminum. It weighed 15 lbs more than the aluminum one.

    I am not a race driver. I have competed a few times at an event called Run n Gun. The event consisted of road racing, autocross, and drag racing. These are timed events. It's the only time that I have been on a track. I did do very well racing my cars at this event.

    My 16 year old son is a racer. He started in go karts won several championships racing super bike powered sprint cars. This year he is racing an American-Canadian late model Asphalt race car.

    Fran, right after the Run n Gun that we talked at I gave Dragon to my brother in law. For the past few years I have been dealing with health issues. In addition I have been taking care of 2 immediate family members, both of whom passed recently. I have just started to work on cars again. I am working on a simple Miata based car that I hope to sell some kits of.
    Last edited by jmc; 02-05-2012 at 09:38 PM.

  9. #9
    Junior Member
    Join Date
    Jan 2012
    Location
    Italy
    Posts
    17
    Hi Fran,
    it looks like you are the best person to talk about aluminium chassis.... glad to hear that you succesfully completed many aluminium cars so far. My car is gonna be a sport street roadster (not race), Corvette like.

    My main concer using aluminium is that without the roof, my design going to have a lot less rigidity. I would use different size of square 6061-T6 aluminium extrusions (from 50x50x3mm to 100x60x4mm), with stressed aluminium panels TIG welded (full butt welded).

    Do you have any data about torsional stiffness of your chassis ? I'm executing righ now some FEA simulation and I would appreciate to have some data to compare to.

    thanks.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •