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Thread: Electric Car chassis!

  1. #1
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    Electric Car chassis!

    Hello everyone!
    I have been lurking around for few months and I am impressed by how helpful most of the members here are. Over the few months, I have learned a lot of useful things from this forum. Thanks to some members here who go to great lengths to post each and every detail of their progress. It has helped me avoid mistakes that I may have made in future.
    I am planning to build an electric super car. I plan to complete it in three years and I would like to know if I am going in the right direction for the chassis design. I will be building it during my free time. At the moment everything is in 3d format.
    I plan to build by welding space frames. Either tubular or square/rectangle section steel tubes.
    I would like to know which is better, Round tubes or Square section? I would also like to glue carbon fiber sheets on the outer part of the chassis instead of steel sheets.
    (Just like how BAC Covers their mono chassis)
    I would like to post few examples, but I think for the first three posts, I am not allowed to post external links or photos, I do not want to break the rules.
    Thank you.

  2. #2
    Senior Member MacGyver's Avatar
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    Welcome to the forum,

    Looking forward to seeing your ideas. One of our members who makes fiberglass body's also made his first demo car electric. Unfortunately the 20K Battery price keeps most of us from such an attempt.

  3. #3
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    Quote Originally Posted by MacGyver View Post
    Welcome to the forum,

    Looking forward to seeing your ideas. One of our members who makes fiberglass body's also made his first demo car electric. Unfortunately the 20K Battery price keeps most of us from such an attempt.
    That's nice
    You know the username?
    I am aware of the battery costs, but I will find a way to make the money!

  4. #4
    Senior Member ncrazyballa's Avatar
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    batteries are no longer that expensive. you should be able to build a battery pack for around 6k.

  5. #5
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    In regards to the BAC mono that is a true spaceframe with a stressed engine and the body work is just that.
    BAC used round tubes because per weight for torsional and compression strength, which is generally what you will be aiming for lower weight with higher strength.



    You will find most home builders (GT40s, Locost's) will use square tubing as its much easier to fabricate and thus makes the build quicker.
    If its a 1 off i would go this path and take the minimal weight hit as fish mouthing is a PITA even with the tools vs cutting flat edge on a SHS unless you get all of the tubes CNC cut.

    What you can do to save weight is delete the need for stiffening between frame sections by adding panels to make in in shear. This can be done in a number of ways ie AL sheet glued and riveted on, using AL honeycomb as filler, welding in a steel sheet, etc. This is taking steps towards being a monocoque without trying to workout fatigue in AL which is not a space to without real world experience.
    Check out: http://www.themotorreport.com.au/166...s-the-inverter as an example of how this can be done - all plans are downloadable. Not a cheap car to build as too many custom parts for my liking but then again i operate in the extremely low end of the car building $ scale.

    I did a uni project which involved an electric F-SAE car, a number of years back now but range/performance/$ did not come easily even for our modest targets.

    Cheers,
    Taffy

  6. #6
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    Quote Originally Posted by ftaffy View Post
    In regards to the BAC mono that is a true spaceframe with a stressed engine and the body work is just that.
    BAC used round tubes because per weight for torsional and compression strength, which is generally what you will be aiming for lower weight with higher strength.



    You will find most home builders (GT40s, Locost's) will use square tubing as its much easier to fabricate and thus makes the build quicker.
    If its a 1 off i would go this path and take the minimal weight hit as fish mouthing is a PITA even with the tools vs cutting flat edge on a SHS unless you get all of the tubes CNC cut.

    What you can do to save weight is delete the need for stiffening between frame sections by adding panels to make in in shear. This can be done in a number of ways ie AL sheet glued and riveted on, using AL honeycomb as filler, welding in a steel sheet, etc. This is taking steps towards being a monocoque without trying to workout fatigue in AL which is not a space to without real world experience.
    Check out: http://www.themotorreport.com.au/166...s-the-inverter as an example of how this can be done - all plans are downloadable. Not a cheap car to build as too many custom parts for my liking but then again i operate in the extremely low end of the car building $ scale.

    I did a uni project which involved an electric F-SAE car, a number of years back now but range/performance/$ did not come easily even for our modest targets.

    Cheers,
    Taffy
    Hi
    Thanks for the tips.
    I have found a race car builder who wants me to help him with designing a new external skin for some of his single seater cars and he will help me build the chassis. I will have to pay for just the materials. So I am going to build it like the BAC Mono. From what I have been reading so far, I think its the best. So I guess using the expertise of a race car builder, I will get better quality.
    I would like to know if covering or gluing/riveting Carbon fibre sheets on the outer part of the chassis will benefit in adding rigidity. I plan to use 1mm thick carbon fibre sheets.
    The other method I would like to consider is the one you suggested, Adding Aluminum sheets by gluing and riveting. What I am not so well informed is the kind of aluminum sheets I must buy. And how thick It has to be. Sorry If I sound a bit dumb, I am just completely new to this.
    I checked out the link you have posted, could you please tell me where can I download the plans? I would love to check it out. May be in a month or two I will build the chassis on solid works and upload it here.
    Thanks for the tips again.

  7. #7
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    Getting a professional to help is a good idea, designing a chassis should be done suspension first and then working back to making a frame to join the points in space.
    The Inveter files can be downloaded from here: https://grabcad.com/library/andre-ca...rtscar-1/files

    You need to get some books to read on the subject of chassis design, i have only worked with Carbon in some basic none long term applications and not in a position to advise you bonding that to a frame.
    The list here has as good as place to start as any: http://www.buildyourownracecar.com/r...neering-books/
    Chassis Engineering by Herb Adams is as a must have in my opinion and one i reference a lot.

    A space frame chassis can work without the body work which when making a prototype is a massive win in that you can drive it and still have access to all the parts. Start adding panels and things become alot harder.

    For basic just covering applications run of the mill AL from your local supplier will work, if it becomes load bearing then that will depend on the application and there are a lot of choices.
    Just like what lotus did back in the 60s, take a look at the aircraft industry for answers as they have been using it in load bearing applications for years: ie: http://www.totalmateria.com/Article96.htm

  8. #8
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    Icetray,
    Square or rectangular tubing, although not generally thought of as customary, makes a fine chassis. Many formula cars, which rely more on a monocoque design, use this to facilitate attaching panels. In my opinion, some of the finest racecars ever built were the Trans-Am Series cars of Reiley and Scott (current producers of Indy Racing League chassis) They were rectangular tubing from the bottom of the glass down and round from there up in the rollcage. This gave a strength where needed but ease of construction where needed too. It also gave a flat surface to weld the cage of a Camaro or Mustang to a generic lower chassis. Use 5052H32 for the stress skins, DO NOT USE 6061T6. Your racecar builder can tell you why, but that brings up a couple of points. You seem to be on the right track generally, but what type of racecar builder has experience in stressed monocoque construction? That is some pretty elite territory, but general principals are general principals and you might be fine. The bigger issue is your goal of building this within the next three years in your spare time. If every minute of the next three years is your spare time, you have underestimated it by at least 100%. That is not meant to be a discouragement, just shared info that you requested.

  9. #9
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    Quote Originally Posted by ftaffy View Post
    Getting a professional to help is a good idea, designing a chassis should be done suspension first and then working back to making a frame to join the points in space.
    The Inveter files can be downloaded from here: https://grabcad.com/library/andre-ca...rtscar-1/files

    You need to get some books to read on the subject of chassis design, i have only worked with Carbon in some basic none long term applications and not in a position to advise you bonding that to a frame.
    The list here has as good as place to start as any: http://www.buildyourownracecar.com/r...neering-books/
    Chassis Engineering by Herb Adams is as a must have in my opinion and one i reference a lot.

    A space frame chassis can work without the body work which when making a prototype is a massive win in that you can drive it and still have access to all the parts. Start adding panels and things become alot harder.

    For basic just covering applications run of the mill AL from your local supplier will work, if it becomes load bearing then that will depend on the application and there are a lot of choices.
    Just like what lotus did back in the 60s, take a look at the aircraft industry for answers as they have been using it in load bearing applications for years: ie: http://www.totalmateria.com/Article96.htm
    Hi
    First of all, thanks a lot for that link!
    I will start researching more, especially the Chassis Engineering.
    Yea, that's the idea using space frame.

    I will try to avoid thinking of adding any covers for the chassis for now. I will first focus on construction , placing batteries and motors and suspension/sterring mounting. Its not just me who is working on this. I got a staff too to join me on the free time who works on solid works. We plan to construct the chassis on solid works and send it to an expert to judge the stress etc.
    Only then my friend who is a race car builder will come in.

    Thanks once again.

  10. #10
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    @ 76mx

    Cool, I will discuss it with him. He too gave me this option with square section and he suggested that it can save space inside the cockpit but he said that the tubular frames were more rigid.
    My friend makes Formula Cars and hes got his own racing academy.
    I am lucky that I have more free time than a normal person, I am very grateful for that. I do not want to waste it.
    Last edited by icetray; 07-18-2017 at 08:44 AM.

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