bikerbob951 wrote:
Looks great!
I'm in a very similar design phase with my project, learning to work with weldments and 3D sketches, despite using Solidworks for years. Also, with your suspension geometry design, I saw that you used Vsusp... how did you determine what values you wanted for your car? I understand what all the different parameters mean, and what the average values should look like, but how do you know how it will translate to your car's handling characteristics? More to the point, did you base your geometry off of someone's proven design, or did you use theoretical numbers? I ask because that's something I'm struggling with at the moment.
I love the shape of the chassis you're designing. Do you plan to bend the tubes yourself or have them CNC bent? I'm working with square tube simply for cost reduction and ease of manufacture, at the expense of ascetics.
One last thought, you mentioned using plexi sheet for some bodywork, which is something I've been considering... but using it throughout the chassis in lieu of aluminum bodywork. Thoughts?
Anyway, looks great so far, keep us updated!
The suspension values are all based on theoretical "good handling". I've laid out the miata suspension before but I knew my chassis would be vastly larger, wider, and have a completely different weight distribution so I didn't read too much into it. There's also the fact that all production cars, not matter how well they handle, are designed to fit a specific chassis package which doesn't necessarily apply here.
The parameters I listed in the OP were the best I could gather from as much reading as I've been able to do. My general requirements/parameters were:
low roll centers with a downward sloping inclination toward the front
zero positive camber in any circumstance I could manage
ground clearance for the chassis under full bump
general balance of camber loss in roll vs. camber gain in bump
On top of that I had to work around my engine package which is, unfortunately, quite wide. The package is stout and powerful though so I was willing to compromise.
The realization I came to with suspension is that it cannot be perfect without active suspension and I don't have the time or money to develop that system....or buy it from Williams. So what I did instead was use general guidelines and create numbers that hit the spectrum. The rest will come down to chosen shocks and springs (TBD when I have a more accurate idea of weight and distribution) and roll bars that I will probably eventually fabricate.
For chassis fabrication I plan to do as much of it by myself as I can. I'm not making that easy by creating lots of curves but since this is an exo car the aesthetics are important (to me) and I'm not willing to sacrifice looks for ease of manufacture. I will buy a tube roller from HF and upgrade it as necessary. I'm not sure about the bends but they're currently all spec'd to the JD squared 5.5" radius for 1.5" OD .083 tubing so if it works out in my favor financially I will take that route. Or I'll beg someone here with a roller to do the work for a small fee. I don't plan to pay to have them done professionally but that may change in time.
I don't plan to do plexi for all the body work, it's just not flexible enough for a few things I plan to do. I may even go with fiberglass and create bucks for some special work but that's really getting ahead of myself. I also don't plan to use aluminum as body sheeting, it will be used for front and rear bulkheads as well as the undertray(s) but nothing else. Most of the car will be open ala the atomic one.
Funny you should mention weldments in Solidworks, the model I posted shots of was done entirely using sweeps and extrusions. I made it quite far with that model but have restarted today using weldments and it's sooooooo much easier and faster. And my model tree looks perfect now. I will post up a more complete chassis later today, one with a floor and scuttle and whatnot. It's really taking shape.
lastly thank you for the compliment (or at least I'll take it as such) on the looks. I have about 100 sketches of the chassis in various dimensions and was never really happy with them structurally. I'm absolutely thrilled about this one though and it feels good to be working toward a "final" product in terms of the model.
I just bookmarked your blog to read in full at a later time as well