Opened 7 years ago

Closed 22 months ago

#5965 closed defect (wontfix)

Hand Crank can only charge the laptop 21 times

Reported by: arjs Owned by: wad
Priority: high Milestone: Future Release
Component: mechanical Version:
Keywords: crank, freeplay, charging Cc: walter, arjs, vmb@…
Blocked By: Blocking:
Deployments affected: Action Needed: never set
Verified: no

Description

(With reference to the the green hand crank)
On the page http://wiki.laptop.org/go/Product_News

there is a link to the Freeplay Hand crank spec sheet
http://wiki.laptop.org/go/Image:OLPC_clamp_charger_detailed_spec.doc

Page 1 of the spec sheet (under the section of Benefits) mentions that the Crank can work upto 500,000 revolutions.

Cranking at the rated rpm(130rom), it means that it can do 500000/130 = 3846 minutes = 64 hours.

One session of cranking takes about 3 hours, which means that the laptop can only be charged 64/3 = 21 times.

Change History (4)

comment:1 Changed 7 years ago by jg

  • Milestone changed from Never Assigned to Future Release
  • Priority changed from normal to high

Seems like the specs v.s. reality needs testing... Certainly that spec is insufficient....

comment:2 in reply to: ↑ description Changed 7 years ago by vmb

Replying to arjs:

Page 1 of the spec sheet (under the section of Benefits) mentions that the Crank can work upto 500,000 revolutions.

Actually, no -- it says it's been tested out to 500,000 revolutions, not that it's rated to a lifetime of 500,000. But we do need to get Freeplay to give us a more firm estimated lifetime.

comment:3 Changed 7 years ago by erikg

Has anyone ever actually cranked a laptop to full charge from 0?

It seems like an extremely painful process, especially as the freeplay device appears to lack any kind of differential gearing.

comment:4 Changed 22 months ago by wad

  • Action Needed set to never set
  • Resolution set to wontfix
  • Status changed from new to closed

Closing, since we never approved the Freeplay hand cranks for use with the laptop due to the "extremely painful process" involved.

It is clear that 500K revolutions is insufficient for such a hand crank.

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