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Author Topic: Mid- Engine Modified Sports  (Read 401491 times)

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Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1725 on: August 24, 2019, 07:07:55 PM »
I re-designed my shift linkage. The gear change shaft on a Porsche G50 both rotates and moves in and out so I used a series of straight shafts running in Thompson ball bushings to accomplish the shift motion. The rinky-dink way that I had to reverse the shaft rotation was not really very satisfactory so I came up with the approach shown in the photo. I used Ruland shaft collars to fasten the swing arms to the 3/4" shaft and 16mm trans shifter. I drilled holes to bolt everything together and used a surplus threaded link to couple them together.

The shaft collars are nice- they can be loosened and allow their positions to be adjusted.

Regards, Neil
Regards, Neil  Tucson, AZ

Offline Interested Observer

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Re: Mid- Engine Modified Sports
« Reply #1726 on: August 24, 2019, 09:00:57 PM »
Neil,
Given the Heim joints on the threaded link, how does any longitudinal movement of the shift linkage shaft get translated to the transmission input shaft?

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1727 on: August 24, 2019, 10:09:54 PM »
Good question, IO. You're paying close attention.  :-)

I did not have any threaded clevis so I had to use spherical rod end bearings. One is a 1/4" high-misalignment bearing and the other is a normal 3/8". On the 3/8" bearing I used three very thin large shim washers on each end of the ball. This is enough to prevent angular movement of the ball while still allowing easy rotation. In essence, it is "fixed" and having one end that is fixed is all that is needed.

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

Offline Koncretekid

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Re: Mid- Engine Modified Sports
« Reply #1728 on: August 25, 2019, 06:54:53 AM »
Any reason not to fix the other spherical rod end joint in the same fashion to make it even more resistant to flexing? 
Tom
« Last Edit: August 25, 2019, 06:58:57 AM by Koncretekid »
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1729 on: August 25, 2019, 10:11:06 AM »
Any reason not to fix the other spherical rod end joint in the same fashion to make it even more resistant to flexing? 
Tom

Tom, one of the bearing balls needs to be free to allow for the rotation necessary because of the fact that the shift rod and the transaxle are not parallel. It's not much motion but it is necessary.

I do have another idea of how to stiffen the arms; I'll try it today.

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

Offline Peter Jack

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Re: Mid- Engine Modified Sports
« Reply #1730 on: August 25, 2019, 11:15:30 AM »
PM sent.

Pete

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1731 on: August 25, 2019, 07:49:51 PM »
The swing arms I made were a little too flexible so I cut some 1/2" square steel tubing and inserted two , one inside each edge, and riveted them in place. This stiffened the assembly considerably and the shift motion feels good now.

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

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1732 on: August 29, 2019, 06:09:15 PM »
I fired up the engine yesterday, let it warm up, and adjusted the new Proform 850 Racing Series carburetor idle mixtures and idle speed. I had an intake manifold vacuum gauge connected and it showed 11 inches of mercury @ 1,000 RPM idle. This sounds reasonable since I am running a Crower 00427 mechanical roller cam, 290 degrees intake (advertised) and 260 degrees @ 0.050 lift.

It sounds good and the throttle response is very crisp. Far better than the old Holley.

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

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1733 on: September 06, 2019, 07:25:18 PM »
Last year tech did not like the location of my fuel filler cap and tank vent; it was considered to be "in the cockpit" so with the help of a friend, a few borrowed fittings from the Turbinator guys, some pop rivets, and a few lengths of thin stovepipe from Ace Hardware in Wendover, I "walled-off" the cockpit from the fuel filler & vent. The flattened-out stovepipe ran all the way to the top of the roll cage but there was zero visibility out of the right side window. Not good- but OK for a temporary fix.

This week I removed all the thin sheet metal and fabricated an isolation panel out of some scrap 0.080" 5052-H34 aluminum that I had. I riveted an extruded 2024-T3 right-angle piece to the bottom so that it could be fastened to a chassis tube. Another piece of aluminum is fastened to the top of the panel using 5 right-angle floating captive nuts. When the door is closed , it seals against a rubber strip on top of the outer edge of it. I still need to complete the caulking (3M 2000+) and install the rubber strip.

Time is getting short....

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

Offline wobblywalrus

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Re: Mid- Engine Modified Sports
« Reply #1734 on: September 08, 2019, 10:07:13 AM »
It would be nice if all cars had light colored chassis, engine bay panels, and under the hood parts, like you have done.  It makes it much easier to see what is in there. 

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1735 on: September 08, 2019, 08:16:25 PM »
I can't claim to have done it on purpose, WW. I protect the aluminum panels with a yellow zinc chromate primer and the chassis is finished with some polyurethane that I bought surplus from the USAF. It just happened to be yellow.  :-)

Today I finished the panel to isolate the cockpit from the fuel cell filler & vent. It seals against the lower lip on the upper door when it closes.

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