Snubbers and Thrust Restraints¶

Run the Snubbers and Thrust Restraints MicroSim Fullscreen

About This MicroSim¶

This MicroSim puts nine numbered markers on two FanPedia drawings from page 135. On the left, a steel isolation base sits on isolators and carries snubbers, with a close-up inset of one snubber at the lower left. On the right, a fan discharge is joined to its discharge duct by a flex connector, and two thrust restraints, one above and one below the joint, tie the two sides together.

The nine parts are the two snubber brackets (one attached to the fan or base, one attached to the floor), the elastomeric (rubberized) material between them, the isolators, the discharge duct, the flex connector, the fan discharge, the ceiling hung type isolator and the threaded rod. On a wide screen the labels sit in strips above and below the drawing with leader lines; on a narrow screen they move below it as a numbered list. The elastomeric strip is small, so its marker sits just right of the inset with a short pointer to the part; the fan discharge marker sits in the white space above the grey fan section.

The quiz describes each part by its job or its place ("Select the material that prevents metal-to-metal contact.") instead of naming it, in a shuffled order. You get two attempts per prompt. The first wrong answer shows a hint about where to look; the second reveals the part and counts as missed. Mastery is 8 of 9 correct on the first attempt. Explore mode is never scored.

How to Use¶

Explore mode (the starting mode). Point at a numbered marker, or Tab to it, to see the part's name and description in the panel below the drawing. Click it (or press Enter) to open it; opened parts get a ✓ in the label list and the counter shows how many of the 9 you have visited. Clicking a name in the label list opens that part too.
Quiz mode. Press Quiz. The labels and leader lines disappear and a prompt describes one part:
- Correct: "✓ Correct:" with the part name and its description; the marker turns green with a ✓ badge and its label comes back.
- Wrong on the first attempt: "✗ Not quite.", the name of the part you picked, and a hint. The hint never names the answer.
- Wrong on the second attempt: the answer is marked "Answer" and named, and the prompt counts as missed.
Press Next prompt after each answer. The toolbar shows "Parts correct: n of 9".
After the ninth prompt, the summary shows your first-attempt score, whether you reached mastery (8 of 9), and each missed prompt with its answer. Retry missed practises only the misses (not scored), Start over reshuffles and resets the score, and Back to explore returns to the labels.

Keyboard: Tab moves through the markers in number order and then the buttons; Enter or Space selects a marker. After an answer, focus moves to Next prompt, so Enter goes on.

Data label: "Drawing: FanPedia, Twin City Fan, p. 135", shown under the drawing.

Iframe Embed Code¶

You can add this MicroSim to any web page by adding this to your HTML:

<iframe src="https://moroshek.github.io/FanTASTIC-textbook/sims/ch23-snubber-thrust-restraint-overlay/main.html"
        height="796px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan¶

Learning Objective¶

The learner will identify the nine labeled parts of a snubber on an isolation base and of a thrust restraint across a fan-to-duct joint, given each part's function or location (Bloom: Remember, verb: identify).

Audience¶

Adult professional development: new application engineers, sales staff, representatives and facilities staff.

Duration¶

10-15 minutes

Prerequisites¶

Chapter 23, sections "Spring Isolators", "Open, Housed, Restrained and Seismic Springs", "Where the Isolators Go" and "Snubbers and Thrust Restraints".

Activities¶

Explore (4 min): Open all nine parts. Sort them aloud into the snubber (the two brackets and the elastomeric material), what the snubber works with (the isolators) and the thrust restraint across the joint (ceiling hung type isolator, threaded rod, and the fan discharge and discharge duct it is attached to). Where does the flex connector fit, and why does it need the restraint?
Compare (2 min): Name the force each device answers: the snubber limits movement in any direction, such as seismic loading; the thrust restraint limits horizontal motion caused by aerodynamic force.
Quiz (5 min): Switch to quiz mode and find all nine parts from their jobs or places without going back to explore mode.
Review (3 min): Read the missed list, open those parts in explore mode, then press Start over for a new order. Then sort the job cards in Isolation Hardware Sorter.

Common Misconceptions Addressed¶

A snubber holds the fan rigidly in place: in normal running the fan floats on its isolators, and the snubber engages only when an unusual load, such as an earthquake, tries to move the fan too far.
The snubber's two brackets touch when it engages: elastomeric (rubberized) material between them prevents metal-to-metal contact.
The flex connector keeps a spring-mounted fan in place: open springs offer no restriction of aerodynamic motion, so the fan moves at every start and the connector takes the strain; the thrust restraint's threaded rod is adjusted to prevent that horizontal motion.

Assessment¶

First-attempt score shown in the summary as "First-attempt score: n of 9"; mastery is 8 of 9 on the first attempt.
Pointing at markers and opening infoboxes in explore mode is exploration, not evidence.
Follow-up question: a high-pressure fan with a horizontal discharge sits on open springs. Which parts on the right-hand drawing would you add, how many restraints are used, and how are they placed?

References¶

FanPedia: The Fan & Blower Encyclopedia (PDF) - Twin City Fan; p. 135 is the snubber and thrust restraint drawing used here and describes snubbers, p. 197 describes thrust restraints.
FanPedia online - Twin City Fan's online version of the encyclopedia.
Chapter 23: Spring Isolators, Restraints and Field Measurement - the section "Snubbers and Thrust Restraints", where this MicroSim is embedded.
Isolation Hardware Sorter - classifies job-site descriptions by the isolation hardware FanPedia calls for, including snubbers and thrust restraints.