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Thread: Chassis Design

  1. #1
    Junior Member
    Join Date
    Aug 2007

    Chassis Design

    Hello all!

    I'm here looking for some advice regarding a custom chassis. Im in the process of designing a 3 wheeled, ultra light-weight 2 seater. Part of the ultralight necessity is that I need a light, strong chassis, and Im at a standstill about how to design it. The options I was considering are as follows:

    1. Two 10-inch tall trusses, connected about 18 inches apart, running the length of the car, with a small pair of trusses running perpendicular at the front, making a "T" shape. All constructed of square aluminum tubing.

    2. Two rectangular tubes running the length of the car, with diagonal cross bracing along the length.

    3. Something similar to the locost chassis, however pinched inwards at the back to accomodate a single wheel. Also made of square alum. tubing.

    Some other info regarding the design:
    Engine: suzuki/yamaha/kawasaki(whatever I can pick up cheap) sportbike motor.
    Dry weight(planned): 920-1,000lbs.
    Wheelbase: 84-98 inches
    Width(front hubs): 58inches
    Width(body at front hubs): 50 inches
    Height(excluding ground clearance- bottom of chassis to top of body): 40 inches
    Driver weight: 180
    Rear engine & gearbox, weight: approx 200 lbs

    Im looking for opinions on any of those design ideas, or alternative ideas if anybody has any. Any experiences with constructing aluminum chassis would also be appreciated. Essentially, if you know something that might be useful, please explain!

  2. #2
    Senior Member
    Join Date
    Feb 2005

    Re: Chassis Design

    first let me say you are making the right decision going aluminum, its lightweight and strong , but you can't bend too much, why don,t you put your idea on paper so everybody on the forum can see and we can all try to help you?, or at last let us know what city you are at, you know what they say two heads are better than one, but in this case we got many heads don't we boys ?.

  3. #3
    Junior Member
    Join Date
    Aug 2007

    Re: Chassis Design

    All right, Ill do my best sketching out what I was thinking of and Ill scan it as soon as i get a chance. Im also relieved to hear somebody agreed with my choice on aluminum, not only will it work technically, but economically, theres a relatively inexpensive supplier not too far from me that I've found that specializes in aluminum extrusions. With luck i'm hoping to build the chassis for under $450.

  4. #4
    Senior Member AdrianBurton's Avatar
    Join Date
    Jun 2003
    Tucson, AZ

    Re: Chassis Design

    Have a look at the earlier lotus chassis, it was done exactly like what you are looking to do.


  5. #5
    Junior Member
    Join Date
    May 2007

    Re: Chassis Design

    I'm working on a very similar project. 3 wheeler with single drive wheel in the rear. I'm using the Locost chassis as my "inspiration". If you check out Ron Champion's book, he shows the basic chassis being held up by 1 guy, with a caption saying the weight is about 35 lbs. (P.53) I'm not quite sure I believe that, but even at twice the weight, I doubt you will do a lot better with aluminum. I've been looking, and it seems most custom chassis use steel, and not even the more exotic alloys (like 4130).

    Mine is going to be a plug-in hybrid, so my drive train will be much less conventional. It uses a tandem rear wheel with a large drive pulley in the center. I lifted the entire Fiero front end subframe out of an '88. It weighs 200lbs complete with hubs, brakes, suspension, and steering. It will be direct drive, AC electric motor to rear wheel. Total curb weight 1600 lbs. I'm also looking at a foam/fiberglass sandwhich body. What were you thinking for a body?

  6. #6
    Junior Member
    Join Date
    Aug 2007

    Re: Chassis Design

    Sorry if this post is a bit sporadic, trying to cover each issue with a different paragraph.

    For the body I was planning on creating a foam and drywall mud body plug and use that to create a glass mold, similar to another car I found.
    Like him, I think I'd build up foam over the actual chassis, then just tear it off afterwards. I thought that this would be nice as once Ive made an initial mold, I can refabricate body parts at a later date.

    I checked out some of the locost frames, and Ive decided to scrab the aluminum for both cost and feasability reasons. Mig welding steel tube together seems like it would lend itself so much easier than having to learn to weld aluminum(not to mention I have no tig welder at present). I saw that picture too in Champion's book, though I heard(unconfirmed source) that the frame was aluminum, not steel.

    After hearing suggestions here and elsewhere, Im considering a locost inspired frame, 1.5" square 14 gauge steel tubing. Im hoping I can complete the frame to weight around 150lbs, which comes out to about 100 feet of tubing.

    I like the sound of that fiero front end, was it reasonable in terms of cost? Ive looked at some parts from kit cars and hot rod suppliers, and new parts will break the bank for me. I was considering piecing together my own front end and making custom control arms, but even then the cost of good-condition used parts, like calipers, hubs and uprights, steering rack, and shocks would cost quite a bit as well, so an older car's front end might be good.

    A last comment regarding the hybrid, check out for misc. electrical and mechanical parts. Most things there are too light duty for automotive use, but occasionally you can find cheap materials like wiring, switches, lights, and alternators.

  7. #7
    Senior Member Mr355's Avatar
    Join Date
    Jun 2002

    Re: Chassis Design

    Venture Vehicles is introducing the Venture1 tilting hybrid. Looks pretty cool.

    I thought of this jet fighter/formula one idea last spring with two wheels up front. I wonder what the advantage/disadvantages are between 2 front vs. 2 rear wheel.
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