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| bio | website | ericmenze.com |
|---|---|---|
| location | Minneapolis, MN | |
| age | 28 | |
| visits | member for | 1 year, 1 month |
| seen | 7 hours ago | |
| stats | profile views | 28 |
I'm a Computer (Web) Programmer/Analyst based in Anchorage, AK and Minneapolis, MN. I use (among other things) ASP.NET, C# and SQL Server.
I build things. Bicycles, computers, websites, guitars, cars, motorcycles, sound sytems... lots of things.
- Resume: http://ericmenze.com
- Personal Website: http://ehryk.com
- Pause your videos at specific locations: http://pauseforlater.com
- Calculate and build spoked bicycle wheels: http://wheelspoking.com
- See activity specific analysis of your GPX Files: http://gpxdataanalyzer.com
- Tool to open command/powershell prompts from any location (Windows): https://github.com/Ehryk/ContextMenuTools
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Jun 3 |
comment |
How do I calculate the diameter of a chainring from the number of teeth? @zenbike - I would very much appreciate it if you would discuss this with me in chat. |
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Jun 3 |
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How do I calculate the diameter of a chainring from the number of teeth? Why would time be of any consequence here? Wrong is wrong, and has no temporal limit where it becomes not wrong. Further, I didn't see these answers clearly enough showing how to describe ALL a chainring's measurements, and the question does not specify tooth-tip diameter. Your measurements work out because your formula is 'good enough' for the margin of error you care about. What my comment was intended to elucidate is that Daniel's comments were all correct except the "1/2" or so", but more importantly the REASONING by which you were claiming him wrong is invalid, and I described why. |
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Jun 3 |
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How do I calculate the diameter of a chainring from the number of teeth? I am not interested in 'stirring things up' and if you think that is my motivation then you have me completely misunderstood. I have pointed out errors and misunderstandings (not just in the comment you deleted), and you are committing logical fallicies when you say things like "X is wrong because they didn't explain it to me or didn't debunk my theory/equation". Then you deny that you're shifting burden of proof when this is a textbook case thereof. Further, I am somewhat dismayed at the lack of even attempting to understand, or consider you could be in error - you just cut off discussion. |
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Jun 3 |
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How do I calculate the diameter of a chainring from the number of teeth? You can calculate the tooth tip diameter once you relax the idea of using the chain pitch - which @zenbike is not. The chain pitch is 12.7mm (ideally), but he's using the tooth-tooth measurement which he has at 12.75mm. n * this measurement = the perimeter of the 53-gon about the teeth = 675.75mm, but the circumference will be slightly greater (pi*12.75/sin(180/53)) = 676.14mm. The caveat here is that you need to measure each tooth-spacing because they will vary from chainring to chainring, where the pitch will not. |
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Jun 3 |
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How do I calculate the diameter of a chainring from the number of teeth? His expected result was off, and I mentioned I was also surprised by how little, however he was correct that the formula would be 'shy some.' He also is not wrong BECAUSE he didn't give explanation, and you aren't correct until proven wrong. Correctness has nothing to do with explanation or lack thereof. "The math is right, though, unless you can point out a specific error?" is shifting the burden of proof - the math is either correct or incorrect, and n*L = the perimeter of the 53-gon, not the circumference of the circle you drew (pi*L/sin(180/n)). |
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Jun 3 |
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How do I calculate the diameter of a chainring from the number of teeth? Fixed a section that was not bolded |
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Jun 3 |
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How do I calculate the diameter of a chainring from the number of teeth? Removed comment about clearance based on Chain Roller Tops - they don't come near the chainstay |
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Jun 3 |
revised |
How do I calculate the diameter of a chainring from the number of teeth? Removed comment about clearance based on Chain Roller Tops - they don't come near the chainstay |
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Jun 3 |
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How do I calculate the diameter of a chainring from the number of teeth? The same mathematics in a slightly easier to digest format is the crd(theta) function en.wikipedia.org/wiki/Chord_(geometry) - it relates the length of the chord (the chain pitch in this case) to the radius and the angle. Adapted here, 12.7mm = r crd (360 / n) = 2*r*sin(180 / n); therefore r = 6.35 / sin (180 / n) mm. We need TeX over here. |
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Jun 3 |
revised |
How do I calculate the diameter of a chainring from the number of teeth? Did a better job with the image |
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Jun 3 |
revised |
How do I calculate the diameter of a chainring from the number of teeth? Added simplified formulas |
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Jun 3 |
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How do I calculate the diameter of a chainring from the number of teeth? Added roller top description |
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Jun 3 |
revised |
How do I calculate the diameter of a chainring from the number of teeth? Fixed wording: added 'only' in first sentence |
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Jun 3 |
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How do I calculate the diameter of a chainring from the number of teeth? See my answer below. Tooth tip height cannot be calculated this way (without knowing the distance of the tooth tips from pin centers); so if that's the point of the question, the answer is no in a definitive sense (though it'd surely be in the ball park, as you measured experimentally). Note that neither of the reasons you gave make @DanielRHicks wrong. I hope my answer illustrates why he is correct, although your experimental results are 'close enough' for the purpose of the question. |
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Jun 3 |
answered | How do I calculate the diameter of a chainring from the number of teeth? |
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Jun 3 |
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How do I calculate the diameter of a chainring from the number of teeth? @DanielRHicks is correct; but this should still fall within your 1.5mm margin. The reason is that you're making the n-gon discussed above, so the circumference != center of top tooth to next tooth * number of teeth; this is the perimeter of the n-gon at the tooth-tops. I too was surprised how little of a difference this makes (like Dan I was expecting it to be off more) but the proper formula for the circumference through the pin centers = pi * (link length) / sin (180 / n). Using this, I get d = 215.223mm and c = 676.146mm |
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May 29 |
answered | Sources of vibration at high speed in and around rear wheel |
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May 26 |
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Why is my chain riding up and skipping teeth on the freewheel? The jockey closest to the cog is properly adjusted with the stop. After the second jockey, the chain then 'bends' slightly to the inner chain ring (which doesn't happen in the largest chain ring). |
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May 26 |
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Why is my chain riding up and skipping teeth on the freewheel? It's a GT Frame which I then Herculined - it's a brand of truck-bed liner that's very tough and scratch resistant. I coated my motorcycle in it, and after a 35MPH slide down pavement, I just had to roll a bit more on the slide marks, and you can't tell it was even there. |
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May 24 |
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Why is my chain riding up and skipping teeth on the freewheel? I've bent it to be as straight with the cogs as I can, but I'll take it to the bike shop next and have them adjust the hangar as you suggest. |
