Ask Science

10517 readers

61 users here now

Ask a science question, get a science answer.

Community Rules

Rule 1: Be respectful and inclusive.

Treat others with respect, and maintain a positive atmosphere.

Rule 2: No harassment, hate speech, bigotry, or trolling.

Avoid any form of harassment, hate speech, bigotry, or offensive behavior.

Rule 3: Engage in constructive discussions.

Contribute to meaningful and constructive discussions that enhance scientific understanding.

Rule 4: No AI-generated answers.

Strictly prohibit the use of AI-generated answers. Providing answers generated by AI systems is not allowed and may result in a ban.

Rule 5: Follow guidelines and moderators' instructions.

Adhere to community guidelines and comply with instructions given by moderators.

Rule 6: Use appropriate language and tone.

Communicate using suitable language and maintain a professional and respectful tone.

Rule 7: Report violations.

Report any violations of the community rules to the moderators for appropriate action.

Rule 8: Foster a continuous learning environment.

Encourage a continuous learning environment where members can share knowledge and engage in scientific discussions.

Rule 9: Source required for answers.

Provide credible sources for answers. Failure to include a source may result in the removal of the answer to ensure information reliability.

By adhering to these rules, we create a welcoming and informative environment where science-related questions receive accurate and credible answers. Thank you for your cooperation in making the Ask Science community a valuable resource for scientific knowledge.

We retain the discretion to modify the rules as we deem necessary.

founded 2 years ago

MODERATORS

sabbah@lemmy.world

AradFort@lemmy.world

ken_cleanairsystems

count_of_monte_carlo@lemmy.world

126

Why is this ballpoint pen spring shaped like this? (lemmy.world)

submitted 3 days ago by NoSpotOfGround@lemmy.world to c/askscience@lemmy.world

33 comments fedilink hide all child comments

Why is the spring strengthened in the middle?

It doesn't seem to affect the spring's buckling characteristics.

My speculation is that it's to reduce spring noise. That strengthened region at the middle is where the spring will buckle outwards most, resting against the barely visible side rails on the inside of the case. Instead of just one wobbly contact point it now has three rigid ones as a "skate" to reduce the stick-slip noise when opening and retracting the tip. Is this right?

(The pen is a Mitsubishi Uni-Ball Power Tank, pretty much my favorite model.)

you are viewing a single comment's thread
view the rest of the comments

[–] Blackout@fedia.io 6 points 2 days ago (1 children)

My guess too. A longer spring would have more deflection in the middle. This design could reduce that and increase the spring force.

[–] mojofrododojo@lemmy.world 2 points 1 day ago (1 children)

how would it deflect when confined in a plastic cylinder?

[–] Blackout@fedia.io 1 points 1 day ago (1 children)

It wouldn't much, the spring wouldn't be the exact diameter of the chamber. I could see a Japanese or German pen company over-engineering the spring this way because the cad stress analyzer shows a weakness there

[–] mojofrododojo@lemmy.world 0 points 1 day ago (1 children)

no, you can clearly see from the image posted the spring is snug against the interior wall of the cylinder it's enclosed in.

[–] Blackout@fedia.io 2 points 1 day ago

Your confusing an external rib for the internal wall. I can see at least a .5mm gap