Re: Another interesting Tektronix web site


Dave Wise
 

Thank you, Daniel, for your research and ideas.

The natural shape is a hollow ball. It must have been molded.
The screw plays no role in normal use; it limits motion extremes to keep the cushions from tearing or coming out of the mounting holes.

I replaced all the cushions in my D and H, maybe ten years ago, with new-old-stock I bought from Stan Griffiths. (They all have the same orange paint stripe.) Most are fine but one is a mosaic of cracks. I’ve read that making rubber is not 100% science. I figure there was a bad batch.

A solid ball with a hole through the middle would be too stiff unless the rubber was exceptionally soft.

Another TekScopes member created a photo album, "541 Flip-flop fan mounts", in which he created fan mounts from the sole of an old sandal. It seems to me that I could combine that with your tubing idea.

- Long screw or stud, nuts, washers
- Thick-wall latex or silicone tubing, with 5/16” outside diameter (slip fit in the mounting hole) when the screw is in
- Three foam rubber disks with 5/16” hole

- Put screw through tubing
- Thread first disk onto it
- Slide into first mounting hole
- Thread second disk onto it
- Slide through second mounting hole
- Thread third disk onto it
- Add washer and nut just snug

The foam rubber disks cushion axial motion, the tubing cushions radial motion, and the screw holds it all together.

I will look around for an old mouse pad. Cut into disks with scissors and hole with a paper punch. This just might work!

Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Daniel Koller via groups.io
Sent: Sunday, June 20, 2021 5:42 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Another interesting Tektronix web site

Hi all,
I took a look at my D. My shock mounts are not gray - they are black. They are just so oxidized on the surface they look grey, but they darkened up with rubbing.
They have the consistency of latex surgical tubing, which makes me wonder if A) that is what they are made of, and B) maybe that is what they can be made of. I think if allowed to expand fully, they would be closer to "I" shaped - a tube with flanges on the ends, rather than "ball shaped". They take on the ball shape because they are compressed in their mounts. You might be able to approximate them with surgical tubing. I don't know if latex can be formed like thermoplastics, but if so, you could try heating a section of tubing and blowing into it to bulge it out. Donno. But making a flange would be hard. That might have to be molded.
Regarding molding hollow things - maybe mold the solid part, then freeze it and drill out the center in a drill press? Keep it frozen in the mold until drilled. Might be able to cast it in RTV that way. But the resulting part will still be stiffer, in my opinion, than the original, just based on poking at the ones I have on the chassis.
Another possible option is to 3D print. I have been playing with a very soft thermoplastic polyeurethane (TPU) in my 3D printer. One needs a special extruder with very little clearance between the extruder gears and the feed tube, OR a direct extruder that goes right into the print head, in order to be able to "push" the plastic through. But it does work, and I have successfully printed lens caps and gaskets. I have not yet tried stand-offs and vibration mounts, but I do plan on printing a door bumper for a car, which has some of the features of the D's mounts. In the end, the consistency will be a bit stiffer than RTV I think. There is "Ninjaflex" TPU available, which is even softer, but I have not tried it yet.
Ok, and lookie here:https://www.plasticballsupply.com/1-2-in-0-5-black-buna-rubber-resin-balls/?utm_campaign=shopping&utm_medium=cpc&utm_source=google&gclid=CjwKCAjwzruGBhBAEiwAUqMR8HA-hPxNS7QI8J9bTUim39oKHQD8fSUIEJESdlbOjltfInNCf-jM_xoCt7EQAvD_BwE<https://www.plasticballsupply.com/1-2-in-0-5-black-buna-rubber-resin-balls/?utm_campaign=shopping&utm_medium=cpc&utm_source=google&gclid=CjwKCAjwzruGBhBAEiwAUqMR8HA-hPxNS7QI8J9bTUim39oKHQD8fSUIEJESdlbOjltfInNCf-jM_xoCt7EQAvD_BwE>
Rubber balls. You still need to put a hole through them. The dermatologist can provide the answer. Just go have a mole removed and ask them for the hole-punching razor tool they use to circumscribe the mole. I saved one or two and they are about 3 and 5 mm in diameter or so, with various sizes available. This is cheap if insurance pays for the service. Otherwise, you can get biopsy punches on amazon.

https://www.amazon.com/Biopsy-Punch-Sterile-Stainless-Steel/dp/B07R25NHBR/ref=pb_allspark_dp_session_sims_pao_desktop_5/141-2449543-9055469?pd_rd_w=4kBMY&pf_rd_p=3ac2ce50-9d75-4bd3-868d-72b252a0623c&pf_rd_r=1B8PSTPQSFTG3WBK8GEW&pd_rd_r=59842b2f-725a-4e66-90d4-d34a3844db5d&pd_rd_wg=wZjGh&pd_rd_i=B07R25NHBR&psc=1<https://www.amazon.com/Biopsy-Punch-Sterile-Stainless-Steel/dp/B07R25NHBR/ref=pb_allspark_dp_session_sims_pao_desktop_5/141-2449543-9055469?pd_rd_w=4kBMY&pf_rd_p=3ac2ce50-9d75-4bd3-868d-72b252a0623c&pf_rd_r=1B8PSTPQSFTG3WBK8GEW&pd_rd_r=59842b2f-725a-4e66-90d4-d34a3844db5d&pd_rd_wg=wZjGh&pd_rd_i=B07R25NHBR&psc=1>

I think careful use of one of those punches can put a neat hole through a rubber ball, and rubber washers seem to be available in plenty of sizes on the interwebs! Good luck.
I'd be curious to know how you replace these. My 503 has latex isolation mounts in parts of the circuitry. I'm betting they are getting pretty dried up.
Dan

On Sunday, June 20, 2021, 04:16:31 PM EDT, teamlarryohio <larrys@teamlarry.com> wrote:

Been far too long, but the ones I used were the same type generally as the fan mounts. Otoh, McMaster has a huge variety of hardware bits.
G'luck!
-ls-

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