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12:57 AM
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Q: Estimating climbing speed on climbs with variable grade

Phil FrostThere are numerous calculators online which estimate climbing speed based on power and grade or similar. For example: http://bikecalculator.com/ https://www.gribble.org/cycling/power_v_speed.html http://www.u.arizona.edu/~sandiway/bike/climb.html Obviously, these calculators are only as valid...

Somewhat derailled question, with a difficult user asking it.
However, where you (pl.) trolling him?
The whole "If you approximate invariance of air resistance, then it is only aplicable to riding in vacuum?"
oops, I just gave it the rest with my down-vote.
 
1:29 AM
I'm tempted to close it as off topic cos its not real world. But he didn't like the suggestion that theory stuff might be better on Physics. :)
 
1:44 AM
Well, he has a point when he says it is applied physics
It's just, his question is not allowing such a clear answer.
At slow speeds aerodynamic drag does not matter. Ie movement in vacuum is a good approximation, when the solution is invariant of the density of the (thin) medium.
But that's not quite the question, it is too muddled.
 
yeah - Bicycles is supposed to be practical, real world problems.
"how can I climb this grade faster" or less sweatty
rather than climbing grades in vacuum with no friction
 
2:04 AM
That is what the point is not. When I climb a steep hill, that varies between 8% and 12%. It is an excellent, real world, approximation for me not to consider drag.
There is also no significant difference in friction between that and a ramp with the same average.
That is valid because I am in a parameter range where these approximations are valid.
That something is invariant of a property does not require that the property is absent. It means it doesn't matter if it's there or not and thus we can make our lives easier by ignoring it.
You certainly do the same when you consider your physical environment. Eg when you decide if you can lift a heavy object, you ignore the atmosphere or its inertial mass. Then simply decide 30 kg that's good, 55 kg that's too much. Works even if your not in a vacuum!
 
3:11 AM
OK - look at it another way. The question has devolved into a discussion.
Its no longer Q&A
 
 
6 hours later…
9:01 AM
Definitely. It's horrible.
Not a clear question. Request for confirmation by crank.
 
 
4 hours later…
12:35 PM
Race went better than I had expected.
3
Second place in my category.
 
1:13 PM
!
Bravo Zulu!
 
1:48 PM
@Criggie I feel regret for wasting time discussing at length with a crank now. I suppose it's like getting drunk on really bad brandy. You drink it, know it is going to get bad, but the stuff already melted your brain and you still go on.
 
 
9 hours later…
10:52 PM
@gschenk nah you're fine - I do wonder what a vacuum-enabled bicycle would look like
Of course that's also a crappy question because its not something I intend on building
 
Hey, when SpaceX starts flying people to the moon we're going to need a way to get around!
 
yeah - but that would be for space exploration SE
 
Boo, you're no fun. ;)
 
11:22 PM
Well I'd totally write an answer to the question, which would be "solid fat tyres, semi-recumbent step-through design, mechanical coaster brake for rear and a band brake at the front"
There would be some rationale behind a trike design too., for stability
Assuming its ridden by someone in a space suit, that will be 200 kilos of rider, so an off-the-shelf bike won't be up to it. But the smaller planets have lower gravity, offsetting that.
Another issue is cold-welding, where moving metal-on-metal parts stick. So bearings would likely be ceramic or plastic, and any oils/greases would need to be engineered to not vapourise in 0G and high/low temperatures.
 

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