Why this design

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Why this design

This topic has 10 replies, 7 voices, and was last updated 12 November 2023 at 18:02 by Ady1.

Viewing 11 posts - 1 through 11 (of 11 total)

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11 November 2023 at 15:51 #689702
Justin Thyme
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@justinthyme24678
Here is a freewheel hub off a standard bicycle, there is nothing missing here, there is only two pawls and the empty recess does not take a pawl.

My question is, why are they not opposite each other? I guess there is a mechanical reason but I don’t quite understand it (at a guess I’m thinking the offset allows them both to engage better, but far from sure)
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11 November 2023 at 17:41 #689752
Ady1
Participant
@ady1
I have found quite a few design solutions on youtube, there is a small community of very talented guys who actually do CAD style moving parts videos which explain stuff better than a narrative ever could

That’s where I would try first
11 November 2023 at 20:01 #689774
Justin Thyme
Participant
@justinthyme24678
do you have a link
11 November 2023 at 20:01 #689775
Mark Rand
Participant
@markrand96270
My guess would be that it’s clever enough to result in nine or ten clicks per revolution.

Edit to add:-

No, the pawls must be on the outside teeth, which would be many more clicks per revolution, but still arranged to give twice as many clicks as teeth. The shiny areas on the face are, presumably friction surfaces???
11 November 2023 at 21:14 #689780
Bazyle
Participant
@bazyle
If it is symmetric wear or damage might push it sideways and lock it, maybe, just a guess. Or with two play in the bearings may ensure that both pawls take equal stress but a third one may never actually make contact so proved pointless. The design for 3 would have been tested and then someone got a bonus for saving making ten million pawls a year.
11 November 2023 at 23:11 #689789
Ady1
Participant
@ady1
On 11 November 2023 at 20:01 Justin Thyme Said:

do you have a link

No nothing like that, you have to do your own searching and use appropriate terms

For example I had nothing that really explained the feed mechanism of an MG42 and trawled through a load of crap until
12 November 2023 at 10:43 #689835
Robert Atkinson 2
Participant
@robertatkinson2
Only the designer knows for sure. They can have 2 to 8 pawls. Some explanation here:

https://www.bikeradar.com/advice/buyers-guides/freehubs/

and

https://www.sheldonbrown.com/freewheels.html

Of relevance “This particular freewheel has two pawls directly opposite one another and an odd number of ratchet teeth, 15, so only one pawl engages at a time.
12 November 2023 at 11:45 #689866
peak4
Participant
@peak4
Is it your own freewheel, or did you find the photo on the net somewhere?
A remarkably similar image is on This Cycling Forum, where a possible answer is provided just below by Colin

Bill
12 November 2023 at 13:00 #689935
Justin Thyme
Participant
@justinthyme24678
Lets say I was just after a second opinion, I was just rebuilding it yet again, and wondered if any of the engineering minded souls on here would of had a better or different explanation.
12 November 2023 at 14:37 #689949
Howard Lewis
Participant
@howardlewis46836
Is the third pawl missing?

There seems to be a space for one
12 November 2023 at 18:02 #689987
Ady1
Participant
@ady1
Certainly looks like there should be a third latch

Could there be any advantage in an unbalanced system?

edit. aha, it’s a cheap/sneaky way of stopping clunking in worn setups
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