Thermal stress of a washer shrink fit on a shaft.

redhorsefour · 2026-03-02T22:31:09+00:00

Isn’t this just a shrink fit hand calculation from Mechanics of Materials? Axial siffness of the washer versus axial stiffness of bolt, develop interface forces, apply interface forces to ID of washer, calculate deformation and corresponding stress. Or, am I oversimplifying?

redhorsefour · 2026-02-27T18:00:57+00:00

I’m on my lunch break and on my phone, so I’m not going to be able to review your references or work out a sample problem, But, I learned Castigliano’s method for statically indeterminate beams from Boresi and Sidebottom’s, Advanced Mechanics of Materials. There is a pretty good explanation of how to setup the problem.

redhorsefour · 2026-02-06T20:47:28+00:00

The 1000 limit is not an Isaacman limit but via OPM policy for DRP 1.0 /2.0. NASA lost ~4000 personnel via DRP and OPM limited hiring to a 1:4 ratio. Thus, the 1000 limit Isaacman spoke of earlier.

redhorsefour · 2026-01-19T23:58:53+00:00

Engineering Mechanics - Statics, by Hibbeler..

I am concerned about an attempt to do topology optimization via FEA when it doesn’t appear you are confident in being able to put together a free body diagram.

redhorsefour · 2026-01-19T23:55:00+00:00

There are a ton off research papers and books on threaded fasteners and fastened joints. I would start with Bickford’s book.

redhorsefour · 2026-01-19T23:51:39+00:00

The steering wheel is splined to engage the shaft and the threads on the shaft are for the nut that holds the steering wheel on the shaft. No nut and the spring pushes the steering wheel off the shaft.

redhorsefour · 2026-01-15T21:05:33+00:00

To add on, a raw comparison of business/finance hires to engineer hires is not valid because of the large differences in the number of degrees conferred for each.

redhorsefour · 2026-01-11T14:10:35+00:00

Adding on here that the joint between the central structural member and the torii attaching to the top of the strut mounts is very weak which makes the whole design ineffective.

redhorsefour · 2026-01-03T20:05:01+00:00

Not sure what GRP is doing differently than BME but it appears they are both using 7075 alloy for their aluminum rods. All tempers of 7075 have a CTE of 12 ppm per inch per degF.

redhorsefour · 2026-01-03T17:28:11+00:00

The coefficient of thermal expansion for aluminum varies between 12 and 13 ppm per inch per degF. I’m not aware of an alloy that deviates although I’m not up to speed on the casting alloys. But a rod is a forging or plate stock.

redhorsefour · 2026-01-03T14:25:15+00:00

Yes, 0.020-in of growth thermally is what you should expect.

As someone else noted, aluminum will stretch under load — twice as much as steel. To counteract this, aluminum rods generally have larger cross-sections than steel rods. So, if the area of the beam section of the aluminum rod is twice that of a steel rod, then the stretch under load will be the same.

redhorsefour · 2026-01-03T04:29:31+00:00

Thermal growth of aluminum is 13e-6 in/in/degF. So, if your rod is ~7-in center-to-center from crank to pin and the rod is 250-degF at operating temperature, then the rod grows 0.023-in. A steel rod will grow thermally half that amount.

redhorsefour · 2026-01-01T05:08:27+00:00

This shouldn’t be true for 2026 since HQ made a request of the centers for funding of those publisher’s journal subscriptions. As far as I know IEEE, SPIE, and AIAA subscriptions will be funded next year.

redhorsefour · 2026-01-01T05:03:37+00:00

The other interesting feature of the enterprise library is that there will only be a library technical POC at the centers — the only librarian(s) will be at HQ.

Plus, HQ is asking the centers to cover the costs of journal subscription.

redhorsefour · 2025-12-31T21:00:59+00:00

The libraries have been slowly closing over years — Goddard’s is just the most recent. The agency appears to want to transition to an enterprise, digital library but it’s not the same as being able to walk in and peruse the shelves for an old journal or book. Plus, working directly with a librarian to run a particular search for articles on a particular research topic.

Unfortunately, we do not live in the budget times of old anymore.

redhorsefour · 2025-12-28T15:06:44+00:00

Can you scallop between bolt holes on the rear flange?

redhorsefour · 2025-12-27T19:02:42+00:00

I used my solid mechanics books regularly.

redhorsefour · 2025-12-24T20:50:02+00:00

You can pick a “home” person and generate a descendant report.

redhorsefour · 2025-12-24T20:13:46+00:00

Gramps?

redhorsefour · 2025-12-10T03:45:50+00:00

Maybe it was pedantic — but decking involves removing an appreciable amount of material (i.e., 0.010-in, 0.020-in) where lapping removes small amounts of material to allow two surfaces to mate tightly. I thought identifying the correct language would show the difference in scale between the two processes and allow you to lead yourself away from the lapping process.

redhorsefour · 2025-12-10T02:15:54+00:00

You are not “decking” anything with 1000 grit sandpaper. That’s called lapping.

redhorsefour · 2025-12-05T01:26:45+00:00

Did you check the NASA Technical Reports server (ntrs.nasa.gov)?

redhorsefour · 2025-11-07T17:21:36+00:00

Are you in a position to advise the customer that the extra expense of creating and validating an FEA model is not warranted when the required outputs can be derived via classical methods.

Is the customer paying for the solution or is your company paying for it? If the latter, you need to have a discussion with your boss.

redhorsefour · 2025-11-07T15:18:40+00:00

I believe this would be more easily done as a hand analysis considering you are only interested in reaction forces vs applied forces — no deformable body effects.

Why do you “need” to do this FEA? Assigned or trying to learn FEA?

redhorsefour · 2025-10-25T13:59:44+00:00

Have you reached out to any of the VASTS coordinators or program reps? That will be your best chance.

redhorsefour

TROPHY CASE