Author Topic: Mid- Engine Modified Sports  (Read 784779 times)

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Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1740 on: October 05, 2019, 06:10:18 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

Well, after a number of shift cycles, that approach was not satisfactory after all- the steel arms were too thin and even after being reinforced it started to flex. Back to the drawing board- or the stash of surplus stuff.  :-)

With my little hobby bandsaw, I cut two new swing arms out of 1/2" 6061-T6 aluminum plate, made a 3/4" hole in one and a 5/8" (nearest to 14mm) hole in the other using aircraft counterbores. They cut a nice clean hole that is also pretty accurate. I drilled and tapped two 1/4-28 holes in each to act as set screws. On the opposite end of each swing arm I drilled a 3/8" hole for the link bearings.

From somewhere I had bought a few odd tube ends that had ball bearings staked in one end and the other end was bored 3/8"- a perfect fit for a 3/8" spherical rod end bearing that I had. Clean both the made threads and the inside of the hole, apply some good ol' JB Weld epoxy and Voila!- a nice link for connecting the swing arms.

The G50 shift rod moves in and out as well as rotates and the rotation is opposite to the normal shift pattern, necessitating the link monkey motion. The G50 end swing arm needs to be able to rotate but be stiff when pushed & pulled. Since the G50 shift rod and the long shift rod are not parallel, there needs to be a bearing on the other swing arm that can accommodate rotation in two axes but also be stiff when pushed & pulled. A spherical rod end bearing does this nicely. I ground a two small divots in the end of the long shift rod to prevent the set screws from slipping on the 3/4" Thompson ground & polished shaft. It has a hard 60C surface so set screws would not be able to bite into the surface otherwise.
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1741 on: October 05, 2019, 06:14:01 PM »
Here are the latest shift linkage photos. I think this approach will be OK.
Regards, Neil  Tucson, AZ

Offline floydjer

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Re: Mid- Engine Modified Sports
« Reply #1742 on: November 04, 2019, 09:37:52 AM »
very nice work Neil. Carry on.
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 #1743 on: November 19, 2019, 06:50:59 PM »
I'm continuing my work on improving my shift linkage. One of the problems I have in smooth shifting the linkage is the geometry. I had the shifter link pivot point located above its end that is fixed to the chassis. Moving the shifter from 1st to 2nd and from 3rd to 4th generated a downward force on the shift rod where it slid through the Thomson ball bushing. Conversely, shifting from 2nd to 3rd and from 4th to 5th generated an upward force. Moving the ends of the link to the same level reduced this quite a bit.

From examining the present shift rod, it is clear that the 3/4" mild steel tubing was not satisfactory. The surface was being indented by the small ball bearings in the ball bushing. Grooves are visible in it where the balls have rolled; this also causes rough shifting across the neutral gate. I will replace the mild steel tubing with Thomson ground & polished shaft. This has a precision diameter and has a vary hard 60 Rockwell C surface.

While I'm at it, I'll move the shifter & shift rod over about 2" to get it a bit further from my right thigh. This requires new mounting brackets for the two forward ball bushings, so I  made two brackets by adapting two nice aluminum right angle brackets that I had in my surplus aerospace stash.

BTW, the four odd-looking orange "nuts" fastening the ball bushing to its mounting plate are called "Hy-Locks". These are prevailing torque lock nuts that have a narrow groove machined around their ends. At a specified torque, the hex end breaks off. This guarantees that they are tightened correctly and does not require a torque wrench.
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1744 on: November 19, 2019, 06:52:59 PM »
A few more pictures.
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1745 on: November 19, 2019, 06:54:13 PM »
More.
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1746 on: November 19, 2019, 06:55:03 PM »
Last one.
Regards, Neil  Tucson, AZ

Offline ggl205

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Re: Mid- Engine Modified Sports
« Reply #1747 on: November 19, 2019, 11:11:53 PM »
Looks like linear bearings, Neil. If they are, your problems should be resolved. Some linear?s are even adjustable for wear.

John

Offline salt27

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Re: Mid- Engine Modified Sports
« Reply #1748 on: November 19, 2019, 11:25:12 PM »
Happy Birthday to you, Neil.    :cheers:

Offline 4-barrel Mike

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Re: Mid- Engine Modified Sports
« Reply #1749 on: November 20, 2019, 12:54:10 AM »
Looks like linear bearings, Neil. If they are, your problems should be resolved. Some linear?s are even adjustable for wear.

John

And may he have the requisite number of runs to require that adjustment!  :cheers:

Happy Birthday, Neil.    :friday

Mike
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Offline Saltfever

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Re: Mid- Engine Modified Sports
« Reply #1750 on: November 20, 2019, 05:25:17 AM »
I think I see wipers on the linear bearing but is that enough? How are you mitigating the ever present salt problem?

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1751 on: November 20, 2019, 09:49:12 AM »
These two bearings are inside the cockpit so salt should not be a problem.

Thanks for the birthday wishes, fellows.
Regards, Neil  Tucson, AZ

Offline jacksoni

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Re: Mid- Engine Modified Sports
« Reply #1752 on: November 20, 2019, 12:46:04 PM »
Happy Birthday Neil!

WRT "inside the cockpit so salt should not be a problem" uuuuuhhhhhh, good luck with that. It gets eeevvvveeerrryywwwhhheeeerrreeee.  :evil:  :cheers:
Jack Iliff
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Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1753 on: November 20, 2019, 01:35:27 PM »
Happy Birthday Neil!

WRT "inside the cockpit so salt should not be a problem" uuuuuhhhhhh, good luck with that. It gets eeevvvveeerrryywwwhhheeeerrreeee.  :evil:  :cheers:

Thanks, Jack. I should have said "...not be as much of a problem."  :wink:
Regards, Neil  Tucson, AZ

Offline Rex Schimmer

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Re: Mid- Engine Modified Sports
« Reply #1754 on: November 20, 2019, 02:47:16 PM »
Lube with Gibbs oil, pretty good a controlling corrosion. Or better yet soak the shaft in Gibbs oil for a couple of weeks.

Rex
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