Mid- Engine Modified Sports

[manta22]

I installed a few safety pins to make SURE the rear body section of my black Mirage will not come loose at high speed-- remember what happened to Bruce McLaren. I've see a picture of one that came unlatched at just highway speeds-- not pretty; did lots of damage. 
 
The sides of a Mirage rear body have molded- in indentations for quick- release pins; Manta Cars installed them in their factory demonstrator MANTA 2. To take advantage of this method of rear body fastening, a vertical piece must be fabricated and bolted or welded to a side- pod chassis tube so that the pin has something to slip in to. Make the depth of the piece such that the quick- release pin balls pop out to lock it into place. I used 1/2" diameter pins made by Hartwell-- more surplus stuff.
 
A second piece of insurance is the pair of "hood pins" that I installed on the top of the rear body. The 1/2" aluminum pin bolts to a steel bracket welded to the rear hoop of my roll cage. This came from Speedway Motors. Since the rear body of a Mirage is hinged at the rear, the front closes on an arc rather than straight down; this made it necessary to angle the pin slightly backward and make the hole slightly oval to accommodate the arc.
 
These details make the rear body mounting very solid and safe. I thought these photos might help explain how they were mounted-- sorry about the poor focus..
 
Look closely at your car-- could it come loose? If you have the least doubt, install some extra safety pins!
 
Regards, Neil  Tucson, AZ
 

[manta22]

Finding racing wheels to fit the five bolt 14.5 x 130mm bolt circle of my Porsche 996 rear hubs did not work out. The only ones I found were $$$$$$$$$ and I wouldn't have wanted to expose them to salt anyway. I abandoned that idea after I found that the existing bolt holes in the hub could be re- machined for larger holes needed to accomodate pressed- in 5/8" wheel studs. This new 5 x 5" pattern will allow me to use Bassett stock car wheels. I will pick up my hubs and brake rotors tomorrow from the machine shop so some progress is happening.

It was necessary to ruin the rear wheel bearings (a double- row ball bearing) taking the hubs out of the aluminum uprights but I probably should have replaced them with new ones anyway. I removed the remainder of the bearing, cleaned the upright, treated it with phosphoric acid, and then gave it a thin coat of zinc chromate primer.

[Rex Schimmer]

Neil,
How did you get the hub and bearings out of the up-right. Press? On aluminum parts with pressed in bearings I would usually go with the "blue wrench" to get the bearing race to expand and then every thing should fall out. Your progress is looking great.

Rex

[Peter Jack]

A press is not the way to remove bearings from aluminum or magnesium castings. Rather than the blue wrench, which does work, I've usually used an old kitchen stove heated to 450 deg. F. Leave the castings with bearings in for a while and the bearings will pretty much fall out. Do the opposite to install the new bearings, with the new bearings at room temperature. This sure saves wear and tear on the bearing bore of the casting.

Because I'm a bachelor the kitchen stove may be substituted. Definitely don't even think of doing that unless you want to attain that status!

Pete

[manta22]

Rex & Pete;

I heated the aluminum upright with a propane torch until it was hot to the touch and then used a bearing puller I bought at Harbor Freight to withdraw the bearing. The kit is called "Front- Wheel Drive Bearing Puller Kit" and cost about $60. I'll use it in the reverse manner to install the new bearing; I have both rear wheel bearings cooling in my freezer right now.

Regards, Neil

[Peter Jack]

My bet is that you're not getting to 200. Cooling the bearings does very little, on the other hand the heat in the aluminum makes a big difference because of the differences in coefficient of expansions. At 450 the bearings will literally drop out and drop in.

Pete

[manta22]

Pete;

You're probably right-- more like 150F is my guess. The key is temperature difference so cooling the bearings to 0F will help a little.

Regards, Neil

[Peter Jack]

My point Neil was that steel expands and contracts much less than the aluminum. The problem, as I see it, is that any time you press the bearings in and out you put wear on the bore and sooner or later you run into a problem with the bearing getting loose in the bore. The oven trick is commonly used by most serious race teams.

Pete

[manta22]

Yeah, I know about the oven trick but if I tried that my wife might stop using it-- I'd starve.

Regards, Neil

[Peter Jack]

That's why you keep an old stove in the garage, for bearings and pizza. The oil and grease fumes add a little flavour.

Pete

[manta22]

The machine shop finished modifying my rear hubs to a 5" bolt circle and pressed in the 5/8" studs. The brake rotors were also modified to this new pattern.
 
Here is a photo of the rotor slipped over the studs:

Bolted to the wheel it looks like this:

The rear of the wheel (15 x 9.5) looks like this with the hub & rotor mounted:

[manta22]

Here is what the left rear Porsche 996 upright looks like with the a-arms attached.

[manta22]

Trial fit of tires-- front tires are sitting at full droop-- normal ride height will put them up into the wheel wells. The front wheels aren't here yet.
Everything is still under construction.

Regards, Neil

[salt27]

Neil,
We need an update.

Thank you, Don

[maguromic]

Neil, Always enjoyed looking at your build, please post some more..  Tony