Author Topic: Mid- Engine Modified Sports  (Read 784823 times)

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Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #45 on: September 20, 2008, 01:35:11 PM »
I fabricated a pretty healthy heel support plate from a piece of scrap 0.160" 7075-T6 that I had lying around. It is held to the chassis tubes by rivets through some aircraft aluminum extrusions. After drilling all the holes and deburring everything I went over it with an orbital sander to scuff the surface slightly to provide some "tooth" for the zinc chromate primer.

The pedal pivots are some surplus things that I bought some time ago with the idea that they looked like they would be useful for something-- and they are. The fabricated pedals rotate on a chrome- moly rod that runs through these things. I need to move the clutch pedal pad over a bit to the left but that's a low priority item. The pivots are bolted to a 0.125" 6061-T6 plate with 1/4- 28 flat head titanium bolts. This plate is also fastened to the heel plate with the same type bolts. It is also finished with an orbital sander and zinc chromate. The pedals will eventually be reinforced a bit and then plated.

BTW, my wife hasn't asked "What are you going to do with all this stuff?" lately. :-)

Here are a couple of photos.

Regards, Neil Tucson, AZ
Regards, Neil  Tucson, AZ

Offline Jonny Hotnuts

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Re: Mid- Engine Modified Sports
« Reply #46 on: September 20, 2008, 08:32:37 PM »
Dont forget the pull back on that throttle pedal!

(Unless you’re using hydro lines)

Love the work....I follow your build closely

 :-D
jonny_hotnuts@hotmail.com

"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #47 on: September 20, 2008, 10:33:16 PM »
JH;

The pull-back bracket will be added later when I do a bit more work on the pedals and before I have them plated-- probably zinc plating with a gold passivation.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #48 on: November 03, 2008, 07:38:42 PM »
This is just a fabrication tip for anyone who may be interested.

This photo shows how to put a bolt through a tube-- in this case a 2" x2" square steel tube. If holes are simply drilled through the tubing and bolts are inserted, the tube will be squeezed and deformed as the bolt is tightened. A far better approach is to cut a length of round tubing slightly longer than the width of the large tube. The I.D. of the tubing sleeve should be slightly larger than the bolt diameter. Insert the sleeve through the tube and then carefully weld around the sleeve. This sleeve will then prevent the large tube from being crushed as the bolt is tightened.

In this photo I am using two sleeves for 3/8" bolts; the sleeves are assembled in the tube but not yet welded.
Regards, Neil  Tucson, AZ

Offline Geo

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Re: Mid- Engine Modified Sports
« Reply #49 on: November 03, 2008, 08:34:02 PM »
BTW, my wife hasn't asked "What are you going to do with all this stuff?" lately. smiley

It's because SHMBO can now find you with out looking all over the neighborhood.  She tells her friends "If I want him he's always in the garage."   :evil:

Geo

Offline Geo

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Re: Mid- Engine Modified Sports
« Reply #50 on: November 03, 2008, 08:43:53 PM »
Neil,

Love your work, enjoy reading about the build.  The tip about bolt sleeves in the tubing can be applied to all section types of tube and even imitation tube like our unibody stiffening and frame box sections.

For supporting our radius arms in case of failure we drilled a hole and inserted a tube with 3/8 ID that was 1/4 inch wider inside and out for 1/2 inch total wider than the body section.  This was welded in and painted.  The cable with small loops on each end was placed over each end of the tube and a stainless bolt with extra wide stainless washers and a stainless nylock nut was tightened.

Geo

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #51 on: November 04, 2008, 12:46:30 PM »
Thanks, Geo. Your radius arm restraint strap attachment looks like a good one.

Your mention of a washer reminded me of another trick when putting a sleeve in a very thinwall square or rectangular tube. Place a washer with an I.D. slightly larger than the O.D. of the sleeve on each side of the side of the tubing and then weld around the outside and inside of the washers. The diameter of the washer spreads the load over a larger area of the thinwall tubing, giving it more bearing strength. This works for thin sheet metal, too.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #52 on: June 07, 2009, 04:33:56 PM »
The new left rear suspension is in place now but the modified chassis members are only tack- welded at this point. At present I'm duplicating this on the right rear chassis. Flux is everywhere.

The aluminum uprights are from a 996 Porsche and the calipers & rotors are from the front of a 928 S4 Porsche. The coil- overs are adjustable Aldan units.

Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline John Burk

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Re: Mid- Engine Modified Sports
« Reply #53 on: June 07, 2009, 07:07:25 PM »
Neil
Aren't the arcs of the two upper links in conflict ?

Offline Peter Jack

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Re: Mid- Engine Modified Sports
« Reply #54 on: June 07, 2009, 10:18:56 PM »
I'd like to see the bump steer or roll steer graphs. It's not necessarily how the geometry's accomplished but rather that it follows the correct path and that it locates the wheel firmly in position without binding.

I was intrigued by the use of brazing. We used to use it on road racing cars years ago very successfully. I'm not so sure that it's not a better solution than mig welding because too many people use migs with not enough power and not enough skill. With brazing the process goes slowly enough that the operator can see when he's getting proper wetting action on both of the pieces being joined. The process also causes less distortion.

Pete

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #55 on: June 08, 2009, 12:54:41 PM »
John & Peter;

The upper links are not exactly the same length and the chassis mounting points are not quite in the same plane. This geometry is almost identical to the original Porsche 996 rear suspension but modified to replace rubber bushings with adjustable rod end bearings in threaded steel tubes.

I haven't run any graphs yet but I've checked the bump steer manually and it looks OK. When I'm further along I'll graph it and the camber & caster angles over the full suspension travel.

"Braze welding" has been the norm for many years, especially in the UK. Race car tube chassis were fabricated by this method and it is still used for motorcycle and custom bike frames. I like All State #11FC and Harris #17FC rod-- nickel silver has a tensile strength of 80,000 to 90,000 lb/sq in. This is far higher than the parent metal, mild steel. The lack of distortion and low built- in stress is a real plus.
Regards, Neil  Tucson, AZ

Offline Jonny Hotnuts

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Re: Mid- Engine Modified Sports
« Reply #56 on: June 09, 2009, 12:50:33 AM »
Neil....

Are you planning on running the car this Speed Week?


Also.......

Do you fancy yourself more Hardcastle or McCormick?

-JK
LOL!

~JH
jonny_hotnuts@hotmail.com

"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)

Offline floydjer

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Brazed joints
« Reply #57 on: June 09, 2009, 11:37:32 AM »
Weren`t "Bird cage" Maserati frames completely brazed? J.B.
I`d never advocate drugs,alcohol,violence or insanity to anyone...But they work for me.

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #58 on: June 09, 2009, 12:04:29 PM »
JH;

Wrong car; that "Coyote" in the early episodes of Hardcastle & McCormick was a slightly modified Manta Montage-- a different car from the Manta Mirage. A Montage looked very much like Rex Svoboda's McLaren-- not surprising since the Montage was a copy of a McLaren M6GT. Later in the series they used a cobbled- up DeLorean because Brian had a hard time getting in & out of the Montage.
The Mirage was a copy of a McLaren M8 Can- Am car except they converted the open cockpit to a closed coupe which should have lower drag.
Here are photos of the two different cars-- neither one is mine. Note the "Rockford Files" location.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #59 on: June 09, 2009, 12:07:08 PM »
JB;

I don't know about the Maserati "Birdcage" but most tube chassis of that era were braze welded with nickel silver.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ