Sturmey X-RD5 pinion timing marks. - why?

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Stradageek
Posts: 1657
Joined: 17 Jan 2011, 1:07pm

Re: Sturmey X-RD5 pinion timing marks. - why?

Post by Stradageek »

Geoff.D wrote: 10 Aug 2022, 6:16pm Does this mean that the need for timing stems purely from the ratio between the diameters of the smaller and larger planets?
Yup, that's as close as I can get to understanding it. The fact that Brucey found it difficult to explain means that I'm happy to accept a less than completely satisfying understanding of the issue - I only have so many (and a diminishing number of) brain cells :D

If you want some real brain teasers try working out why Dark Matter/Energy is deemed to exist, why Mercury is a regular naked eye morning star only when viewed from the Southern hemisphere or how the 'slingshot' effect is used to accelerate satellites traveling to the outer solar system.

Like your/my 'timing' conundrum I believe there comes a point where you need a mathematical equation to 'prove' it but a) I much prefer to visualise the answer and b) my maths is not up to it. :?
Geoff.D
Posts: 1982
Joined: 12 Mar 2010, 9:20pm

Re: Sturmey X-RD5 pinion timing marks. - why?

Post by Geoff.D »

jb wrote: 10 Aug 2022, 12:30pm Timing marks are needed on all compound planet gears. As the gear teeth need to all be in the same position to mate with the compound gears 'sun' gear. If they are not aligned more likely than not you wont be able to assemble it or if you do it will feel very stiff to turn.
Thanks, jb. I take your point and I'm beginning to understand why.
My initial thought as to why there might be misalignment between planet and sun (that it was related to the alignment of the two ball locking mechanisms relative to the axle) is wrong. The link to Brucey's explanation gives me more clarification. It's still about alignment of planet teeth to sun teeth, as you say, but more to do with relative diameters of the two pinions.
Geoff.D
Posts: 1982
Joined: 12 Mar 2010, 9:20pm

Re: Sturmey X-RD5 pinion timing marks. - why?

Post by Geoff.D »

Stradageek wrote: 11 Aug 2022, 7:44am
........... I only have so many (and a diminishing number of) brain cells :D

If you want some real brain teasers try working out why Dark Matter/Energy is deemed to exist, why Mercury is a regular naked eye morning star only when viewed from the Southern hemisphere or how the 'slingshot' effect is used to accelerate satellites traveling to the outer solar system.

Like your/my 'timing' conundrum I believe there comes a point where you need a mathematical equation to 'prove' it but a) I much prefer to visualise the answer and b) my maths is not up to it. :?
Aaah. .... that old conundrum. The inverse ratio between age and number of brain cells remaining!!! :D

Some more brain teasers - why does matter require the Higgs Boson in order to have mass? what's going to happen when a real life example of a "worm hole" is identified? why does the scientific method produce far more questions than answers and, yet, is considered "rational progress to understanding"?

I could go on "ad infinitum". But, there again, where on earth (or not on earth) is infinity, except in our minds?

I'm satisfied with Brucey's explanation, even though it only explains one specific static situation in the diagram. I take his word for it that the same reasoning applies if (for example) the planet pinion in the diagram were rotated by 90 degrees. I'm pleased that my thoughts were the same as his (the advance of the teeth on the planet compared to the sun) even though I overcomplicated the reason for this.

As for delving into the reasons as to why it works with prime numbers ....... I'll get back to you when I've worked out why the hare never did catch the tortoise!! :D

Nice to talk to you.
Geoff
jb
Posts: 1782
Joined: 6 Jan 2007, 12:17pm
Location: Clitheroe

Re: Sturmey X-RD5 pinion timing marks. - why?

Post by jb »

Geoff.D wrote: 14 Aug 2022, 2:36pm why does the scientific method produce far more questions than answers and, yet, is considered "rational progress to understanding"?

Ah, but knowing the right questions that have to be asked stops one falling into the pit of superstitious clap trap and conspiracy nonsense.
Cheers
J Bro
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