I stayed late after hours and used the bender in our machine shop with discretion.
Main Roll hoop: 1.75" OD, 0.135" wall. (I was mistaken about the 0.128" wall I mentioned in a previous post.)
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Main roll hoop 1.75 dia 0.135 wall.jpg [ 1.45 MiB | Viewed 3270 times ]
God this thing is heavy. The width of the main roll hoop is 41" CTC, which puts it inline with the standard Locost7 book chassis width.
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main roll hoop front view.jpg [ 1.57 MiB | Viewed 3270 times ]
Note the harness bar is at the same height as the rear uppermost member (Book chassis member "O" I think), to meet K3 and K4 members. The bottom of the triangulation members (meeting the main roll hoop and harness bar) ties into the rear lower control arm inboard point of the radius rod.
I indicated earlier that it has been many moons since my welding class. I wasn't kidding:
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Sorry no showcar welds here.jpg [ 789 KiB | Viewed 3270 times ]
Not exactly "stacked dimes" but more like stacked bird ****.
Nevertheless, I think it'll hold. Checking it against the chassis:
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checking rollhoop against chassis.jpg [ 1016.83 KiB | Viewed 3270 times ]
The bottom of the main roll hoop leaves barely an inch of clearance above my helmet. Without a helmet I've got plenty of clearance.
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Main roll hoop and helmet.jpg [ 1.07 MiB | Viewed 3270 times ]
This is cutting it close, but I think I'll just go with it.
With regards to the front suspension, I've ordered a set of 1999-2005 Miata front spindles from ebay, and I'll need to fabricate front LCA once they arrive. for the UCA, I'll just follow suit for standard Locost7:
http://www.speedwaymotors.com/Adjustabl ... 2095.html/I've been giving the rear suspension some thought. Here is where I will cut the upright:
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location of cutting the upright.jpg [ 1.04 MiB | Viewed 3270 times ]
Essentially the cross section is an I-beam, and the web 0.825" thick.
Considering I will be loading a 1/2" diameter grade 8 bolt in double shear. Assuming a grade 8 bolt yield strength of 130ksi, and an allowable load of 1000lbf (est.), this gives an allowable stress of 2.55 ksi, which results in a Factor of Safety against yield of 52.
One could argue the smallest cross section of the upright above the bolt would have the highest stress, and I should consider the yield strength of the cast iron instead, but that material section above the bolt is does not experience bending moments as the material under the bolt (between the UCA bolt and spindle). Granted there is likely bearing stress from half of the cylindrical surface of the bolt acting on the upright, but I'm fairly sure the material above the bolt would not come close to the Von Mises stress.
Also, if we look at the OEM upper control arm pickup point, the cross section where the ball joint tapered shaft enters the upright is substantially smaller than the section I will be using. I do not intend on welding onto the cast iron upright, as this would likely reduce its' yield and tensile strength and likely fracture at the heat affected zone.
I intend on using 5/8"-18 heim joints with AFCO steel swaged suspension tubes for adjustable camber. Likewise, the same member for toe links.
http://www.speedwaymotors.com/AFCO-1954 ... 0947.html/In terms of ride height of the car, I'd like to stay low at around 3" to 4". The problem is if the car is this low with 16" wheels, the angle of CV axles increases, and there is likely an efficiency loss. Ideally, I would love to rotate the engine 90 degrees forward to lower the CG of the engine, and raise the inboard axle point, and then run a dry sump. This would lower the CG of the car, as well as allow for more horizontal axle positioning. But, I'm only dreaming, as a dry sump would not be cheap.
Anyhow, I'm also thinking of going with 13x10" wheels for solo II:
http://www.bassettwheel.com/legends_mini.html/And some used 13x9.5" used hoosiers:
http://www.ebay.com/itm/679-2-USDRRT-Ho ... 601721234/This would help aid in lowering the car. However, there is an issue with the willwood 12.2" rotors not clearing.
I also need to start thinking about steering rack placement, and if I want to use the integra steering rack with a Coleman 2:1 steering quickener.
And then there is the rest of the car:
Steering column support
Pedal Box mount
Shifter linkage and support
the list goes on...
Also, I'd like to place the radiator, fuel tank, and battery infront, and all in a line and longitudinally (in place of where the engine would have been). I was thkinking of picking up four bathroom scales and corner weight the car before I start fabricating support beams and tabs. The car will likely be biased towards the rear left, as both the engine and driver are both on the left.
Anyhow, it's late, and I've run out of shielding gas. This is like taking small bites out of an elephant one nibble at a time.