Since the thing called Q-factor came from bikes I’d suggest that the bike definition be used. Even if the Q-factor is not really a factor but a distance.
Q factor is the overall width of an installed crankset, measured parallel to the bottom bracket shell from the outside of one pedal insertion point to the other. You can think of it like this: the larger the Q factor, the farther apart your feet will be.
The Q-factor is effected by the axle length and crank offset (sometimes probably incorrectly called the crank Q-factor).
THIS. Sure, this thread was reaching its typical height of unicycling nerdliness (actually much higher, with actual math involved), but how about something useful that people can understand and work with? How about this:
Pedal Offset: The measurement defined normally by “Q-factor”, laterally from the thread opening on one crank to the other. The total distance that separates your feet, width-wise. We don’t measure from the center of the pedal because pedals come in different widths, as do feet.
Crank Offset: The amount of outward “flare” of a crank arm. A “zero-Q” crank would have no offset, but the vast majority of bicycle cranks have an offset of several mm.
Pedal Offset presents the complete picture for a given complete unicycle or bike, including hub width, bearing spacing and everything else in there. This is useful for a specific cycle, or to compare with the Pedal Offset of another cycle. Crank Offset gives just the number for the cranks, which stays the same wherever they are installed. Double the Crank Offset to get the total amount of “flare”.
No more duck discrimination! Ducks are supposed to walk like ducks; they are built primarily for the water, and walking on land is only secondary, so cut them a break!
Now for the hard part: How to accurately measure your Pedal Offset? It’s not that easy…
This is still not fully rider independant as the seat hight depends on the rider.
As always when I try to come up with overly complicated solutions to nonexistent problems someone eventually finds a very sensible and boringly easy approach.
Obviously. But you won’t be able to come up with a measure of “quack” which is both useful and completely rider independent. If a 12" uni has the same Q-factor as a 36" uni, then the stance of the rider of the 12" uni (most likely a 5-year old) would be much wider–relatively speaking–than that of the 36" rider (most likely an adult). Dividing by h gives you a comparable quantity which says something useful about the stance of the rider. Plus, it only depends on the unicycle itself, not on the natural stance of the rider.
Maybe I’m missing something, but wouldn’t it simply be a measure of the distance between the spindles minus the width of the hub, adjusted so that 0 becomes the “standard” (if there is one)?
Maybe your mathematical background is making your think this has to be somehow related to the mathematical definition of a factor? The word ‘factor’ has more than one meaning:
factor: “a fact or situation that influences the result of something”
Given Q is for “quack” (which I have learned from this thread) this meaning was probably the original intent – as Finnspin eludes to above, maybe you’re trying to solve the wrong problem? That is, trying to define something precisely that was never intended to be used that way.
The issue is that this quantity does not directly tell us how much the rider has to “quack”. The Q-factors on a 12" and a 36" uni could be the same, but the rider of the 12" would most likely have to “quack” much more than the 36" rider, because the 12" rider’s legs are so much shorter than the other.
Like @DrD, I don’t see any reason to insist that the Q-factor is dimensionless (i.e., the ratio of two lengths). But I still think that my Q/h definition says more about the “quack” than the original Q.
Just consider the 12" being closer to the size of a duck. A duck will certainly quack more when on a 12" where as if it is sitting on 36" it will just relax on the seat or just fly off. No quacking whatsoever
An UW does away with the frame and often the spokes and hub and because of this can have an extremely low Q, but there’s no way to get away from the axle width of an actual unicycle.
So the alternative name instead of “Q factor” seems to be “tread”, or more explicit: “tread of the crankset”.
Crankset is a common term in bicycling, referring to the crank arms, crank axle and some more things. “Crankset” isn’t a common term in unicycling, but one might argue that the term works analogous for unicycles, i.e. axle/hub + cranks = crankset.
So that’d make “tread of the crankset” a reasonable alternative to “Q factor” also for unicycles.
Still not convinced or you want to be more explicit, I’d suggest “tread of the hub and cranks”.
Side note: There’s the related term “stance width”. This seems to be common for the lateral distance between the centre of the riders feet. So it’s the tread of the hub and cranks plus a bit more. This term seems to be common in b*ke fitting, especially for clipless riders, where the “stance width” is fixed. (Just noticed, @JimT already mentioned that earlier.)
Do you think when they were coming up with the idea for “The X Factor” TV show that there was ever a discussion of if it’s precise definition? Maybe not. (Then again, maybe that is pretty ‘dimensionless’ stuff, but I don’t want to get into anyone’s taste in televisual entertainment )
“Crankset tread” seems like a reasonable term if you want to have a precise, absolute, measurable dimension, but folk will pretty much always just default to “Q” since it all seems pretty relative.
In unicycle land you’ve pretty much only got 100mm or 125mm bearing spacing on hubs nowadays, and cranks with some flare or not, and while there has been some discussion on here lately regarding pedal extensions (and hence more “Q” due to those) I think most folk are probably comfortable with the loose definition of Q-factor.
Perhaps more fundamentally, there doesn’t seem to be a precise definition of “saddle height” – I mean where to you measure it from, and to: the ground, the centre of the axle, the top of the pedal, top of the frame, to centre of the seat, nose of the seat? Folk seem to be quite content with not having a “definition” for that are happy enough saying they need to put their seat higher or lower (and use the markings on the seatpost as a relative measure).
It’s unicycling, not rocket science, and while hubs and cranks are precision engineered I don’t think we need to get too caught up in it all.
I’ve been quite tongue-in-cheek with this, that is because I don’t think it really matters too much, apologies if I have offended anyone with that.
That´s what unicycling is all about to me, the simplicity and the pure fun. I give a f*ck about all the technical stuff as long as it works.
Not meant to offend someone either.
Georg
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