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Old 01-20-2013, 09:59 PM   #16 (permalink)
christofoo
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00C - '00 Toyota Corolla
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Quote:
Originally Posted by freebeard View Post
Looks good. Although I don't get why the lines across the top are curved when the edge fore and aft of them are straight.

What would you think if the metal frame was a complete square with maybe 2 round crossmembers?

Look at the departure angle from the bottom of the caster to the back edge. Try the caster maybe 6" from the back edge. One is probably better than two so you don't get twisting forces on the tongue when you traverse a dip at an angle.

I've been on that side of town twice now and forgot the Polymetal both times. Maybe I should make a special trip, but my priorities have resorted themselves this month too.
I was afraid that would be confusing; you can best see this in the front and back projected views; I've got a little curvature in the level area at the top, but no curvature in the sloped section. The line at the front is curved, but it's curved towards you, roughly. This is to match the curvature of the trunk, which is about 3/4" higher in the center than on the sides. I might drop this feature though. I doubt it will affect reattachment at zero yaw, although if the front lip of the box sticks up above the trunk anywhere I suspect it would cause a little drag at higher yaw angles. Arguably it is the curve of the roof that I should be trying to match on the sloped portion to get best reattachment. On the other hand if I'm not going to worry about drag from the caster I probably shouldn't obsess over the the front lip.

I've been wishing I had a CAD model of the car, because I'd like to get a closer look at how I matched the trunk, and there is also more detail on the sides of the car that I wish I could get a more careful look at. 3dcadbrowser has a nice looking 97 Civic file, and I can get it for free, but I have to wait '3-6 weeks' for my upload credit. I think the moral of this story is that if you're a CAD user you should go and upload a file now so you can have a free credit on tap when you need it. (And of course once I have a model of the car and the aero box I'm going to really wish I had CFD.) (Next best thing to the CAD file would be having it in the driveway, presumably it should be back in town later next week.)

I'll be tinkering with the placement of the caster. Once I get the bottom rail formed I'll set the car in the gutter and eyeball where it would work best. I have to consider on one hand that the strike is less likely to occur with the caster farther from the car, and on the other hand that the strength of the bottom rail will be greatest if I can keep the caster closer to the car.

I'd call the floor frame a trapezoid rather than a square, but yeah, that's the idea. And I may need to get the welder anyways - I'll have a better idea after I call some machine shops tomorrow on bending the main bottom rail.

Last edited by christofoo; 01-20-2013 at 10:04 PM..
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