Author Topic: Mid- Engine Modified Sports  (Read 784801 times)

0 Members and 1 Guest are viewing this topic.

Offline manta22

  • Hero Member
  • *****
  • Posts: 4137
  • What, me worry?
Re: Mid- Engine Modified Sports
« Reply #1725 on: August 24, 2019, 08:07:55 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

  • Sr. Member
  • ****
  • Posts: 433
Re: Mid- Engine Modified Sports
« Reply #1726 on: August 24, 2019, 10:00:57 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

  • Hero Member
  • *****
  • Posts: 4137
  • What, me worry?
Re: Mid- Engine Modified Sports
« Reply #1727 on: August 24, 2019, 11:09:54 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

  • Hero Member
  • *****
  • Posts: 1203
Re: Mid- Engine Modified Sports
« Reply #1728 on: August 25, 2019, 07:54:53 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, 07:58:57 AM by Koncretekid »
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!

Offline manta22

  • Hero Member
  • *****
  • Posts: 4137
  • What, me worry?
Re: Mid- Engine Modified Sports
« Reply #1729 on: August 25, 2019, 11:11:06 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

  • Hero Member
  • *****
  • Posts: 3776
Re: Mid- Engine Modified Sports
« Reply #1730 on: August 25, 2019, 12:15:30 PM »
PM sent.

Pete

Offline manta22

  • Hero Member
  • *****
  • Posts: 4137
  • What, me worry?
Re: Mid- Engine Modified Sports
« Reply #1731 on: August 25, 2019, 08:49:51 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

  • Hero Member
  • *****
  • Posts: 4137
  • What, me worry?
Re: Mid- Engine Modified Sports
« Reply #1732 on: August 29, 2019, 07:09:15 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

  • Hero Member
  • *****
  • Posts: 4137
  • What, me worry?
Re: Mid- Engine Modified Sports
« Reply #1733 on: September 06, 2019, 08:25:18 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

  • Hero Member
  • *****
  • Posts: 5503
Re: Mid- Engine Modified Sports
« Reply #1734 on: September 08, 2019, 11:07:13 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

  • Hero Member
  • *****
  • Posts: 4137
  • What, me worry?
Re: Mid- Engine Modified Sports
« Reply #1735 on: September 08, 2019, 09:16:25 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

Offline MattGuzzetta

  • Full Member
  • ***
  • Posts: 103
Re: Mid- Engine Modified Sports
« Reply #1736 on: September 25, 2019, 02:46:47 PM »
Hello Neil,
I have looked at all the listed runs on the WOS site and did not see any runs with car 291.  Did you finally get to run or were you still running into inspection woes? I follow your build on this forum and love the car, need to run that dang thing. As the results have not been posted for Monday, I hope you did get at least one or two runs in! Did you run and how did it go, if you did?
Keep up the information on your build site, love your car!  8-)
Matt Guzzetta

Offline manta22

  • Hero Member
  • *****
  • Posts: 4137
  • What, me worry?
Re: Mid- Engine Modified Sports
« Reply #1737 on: September 25, 2019, 03:56:28 PM »
Thanks for the interest, Matt. Yes, I had a problem in tech, my helmet was not completely below the top of the roll cage. It was about 1/4" too high, even with my scrunching down as far as I could and even with modifying the seat as much as we could in the pit. It was clear that I'll need to fabricate a whole new seat that will allow my butt to move a bit forward so that my helmet will be lower. My friend Wayne Ludington and I had done all we could so it was time to pack up and head home.

My thanks to Jeff Nish and Rob Freyvogel who both loaned me their spare helmets to see if they would help. The USFRA loaned me a -5 firesuit that gained me a little over my thick -20 suit. Thanks to everyone who helped.
Regards, Neil  Tucson, AZ

Offline MattGuzzetta

  • Full Member
  • ***
  • Posts: 103
Re: Mid- Engine Modified Sports
« Reply #1738 on: September 25, 2019, 04:37:08 PM »
Thanks for the quick reply Neil!  Bummer, you have made 2 trips (if my memory is correct) to Bonneville without being able to make a trip down the track.  I commend you for the tenacity to keep making the effort and hope you finally make the show!  Maybe you can make it to an event at El Mirage to see what else you need to tweek to make it through tech, it would be a shorter trip and get you cleared for a real run at Bonneville.
I love your monocoque work and all the aircraft fittings in your car, very cool.  The 500cc Streamliner I built was a monocoque built with fiberglass, with construction urethane foam sandwich as the main structure. I used to send photos of the build to the SCTA to explain wihat the structure was internally as there was no way to see the actual structure when it was painted.  Plenty of work in the 60's as a student!

Hope you get to run next year!
Matt Guzzetta

Offline manta22

  • Hero Member
  • *****
  • Posts: 4137
  • What, me worry?
Re: Mid- Engine Modified Sports
« Reply #1739 on: September 25, 2019, 04:47:45 PM »
Thanks, Matt. Your little streamliner sounds interesting!

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