I have only ridden 20" unicycles so far. I am planning to get a uni with a bigger wheel. I still don’t know how to decide on 26", 28", or 29".
All I know is that they are all faster than my 20" (without getting into crank length vs. cadence, etc. – I don’t like to pedal really fast anyway).
My question is this: When you UPD and you are going faster than you can run, what happens? You fall? How fast can an average person run? How much momentum is lost when your feet first hit the ground? In other words, what is a safe top speed assuming you have an aversion to road rash and tumbling along the asphalt?
There’s a gravel foot path close to my house that I like to ride around on my 29er. The path is twisty and the gravel is loose … it’s fun to slide around going as fast as possible.
The other day I had a UPD on this path while going pretty fast and I hit the ground running - but not running fast enough. I did that cool thing where I was leaning forward too much and couldn’t catch up to myself. I kept running and running but finally decided it was time to tuck and roll. Naturally, the first thing I did after getting up off the ground was look around to see if anyone witnessed what must have been a pretty funny sight.
I guess the point is that I can usually run out of a top speed UPD on the 29er (with 125mm cranks) but not always. FWIW I love my 29er and you would love one too!
I can run out UPDs up to about 12 mph. Above 14 mph and I’ll end up sliding or rolling on the pavement.
Fortunately I’ve only had one UPD at 14+ mhp (this was on a Coker). The spedos max reading was 17.5 mph and I believe I dismounted at that top speed. I was fortunately wearing inline skate kneepads and full finger cycling gloves. I ended up doing a nice headfirst slide on the pavement, just like I was doing a slide into home base. I slid on my knees and hands. My pride was hurt because there were witnesses (it was on a well used city bike path). Other than that, my only injury was a small scrape on my forearm from the pavement. No biggie.
Wear leather cycling gloves, hardshell inline skate kneepads, optional wrist guards, and a helmet. That will be enough to keep you from getting too scraped up in the event that you are unable to run out a UPD.
In just the past few months, I have gotten to where I can ride my 26 inch uni faster than I can run. I have only had to dump once because of an uneven unlit sidewalk one evening. I found that you make a few stumbling long steps with you hands sort of paddling along for a moment and then tucked into a roll. I wasn’t really any worse for wear. I would love to see a video of this cause I can imagine it is really funny. Anyway, crashing seems to take care of itself. I don’t worry so much about it.
-gauss
>run, what happens? You fall? How fast can an average person run?
I would guess that the average guy under 40 can run about 12 mph easily
(for a short time, and you only need about 15 feet at most). 15 mph is a
pretty fast sprint (either on or off a uni), but it’s hard to hit that
speed on unis under 28" for most people. Basically I find that people can
ride about as fast as they can run, so it’s unlikely that you’ll have a
problem. I’d make extra sure NOT to wear loose laces in your shoes, tho –
that’s where some real problems begin.
Yeah, I have ‘run out’ some awesome UPD’s a few times myself. It is actually such a funny feeling to come off the uni, sort of still going through a pedalling motion with my legs only finding myself doing it right on the ground. I throw in a few windmilling arms for dramatic effect and then if I think things are feeling rather ominously on the verge of out-of-control I head for the tuck and roll.
Sometimes the tuck and roll isn’t needed and I can just run out the UPD but when the roll is called for it does end the whole show with a nice bit of flare. (Thank goodness I did all those shoulder rolls in my martial arts training days!)
I’m sure this type of performance, though only occasional for me, is impressive in a strange way for those innocents nearby. It helps convey the high-risk nature of uni’ing that is often overlooked by those only familar with the sport via the circus context .
Wow, thanks everybody! I’m going to get a 29" uni, tuck in my carefully tied shoelaces, wear the specified protective gear, and ride at speeds faster than I originally thought safe. And I won’t worry too much about taking a tumble. If my adrenaline-charged legs can’t handle the speed, then I will crash as best as I can.
I’ll take it slow in the beginning. Unicycling has motivated me to get in shape – lose weight, get fit, build some lean body mass. It also provides me daily exercise, which will help with some of the above. The goal being, of course, to be able to ride better. Longer rides. Steeper hills. Safer falls.
By the time I have enough skill and riding experience to feel comfortable and safe while perched on a fast-moving unicycle, I will be in better physical condition – and better able to handle a fall. And I’ll find someone who can teach me how to fall, too. I’m not sure how instinctive it is.
I was riding a Coker on a 20 mile ride that leaves downtown at 2AM. Heading up a hill, which I can go much faster up than down, I was at what I thought was full speed (aka Mach-Coker), but hit a bump, leaned foreward into it and began picking up speed at a tremendous rate. Shortly, I was going too fast to bail or run out. This was definately my top speed ever. Speed stabalized at a very uncomfortable rate, but I was still falling foreward. I hit a expansion joint and was sent flying in front of the cycle and landed with hands straight out in front (super man style) and slid along the concrete on my wrist guards, eventually slowing to the point where my toes also slid along the road. Sparks were flying from the wrist guards for what seemed a very long time. A few bikers behind me were way impressed when I got up -unscathed- walked back to my unicycle, remounted and continued. I still don’t wear knee pads, but never ride without wrist guards or a helmet.
Some dramatic descriptions there, and I recognise the symptoms!
Back to the original question…
If you’re not into riding fast for fast’s sake, then you’ll probably be doing around 5 - 6 mph on the 20. A 28 is only a 40% bigger wheel so, all other things being equal, you’ll be doing around 8.5 mph. At that speed, you will easily run out of most UPDs. You will only have really nasty UPDs (on the flat) if you’re pushing the limits.
The taller wheel will change the angle at which you fall, making it more likely that you will lose balance and hit the ground with more than your feet, though.
On the flat, riding as hard as I can, on a 28 with 110s, I’ve never come close to hurting myself in a UPD. I always wear cycling gloves and a helmet. On a Coker with 125s, I did the full Superman body surfing sliding to third base routine and that hurt!
(Trying to make this accessible to the American readers: I’m simply guessing that the posture adopted when sliding to 3rd base is broadly the same as when the tail end batsman prostrates himself to the Australian bowler and begs for mercy.)
On Sun, 26 Jan 2003 17:18:41 -0500, “David Stone” <dstone@packer.edu> wrote:
>It’s MUCH easier to get your cadence up on larger wheels. I can’t go much
>higher than 130 cadence on a little wheel, but on a Coker, I can easily
>achieve much higher rates (like 170) for short spurts. Maybe a good
>formula would be that you increase the size and the cadence by about the
>same percentage. If so, then you just have to multiply the percent
>increase of the wheel size (in this case, 40%) by itself and then add the
>original percent increase (so 40%x40%=16%, + 40% = 56%, which would mean
>that the speed would go from 6 mph (on the 20" wheel) to nearly 10 mph (on
>the 28").
That’s interesting David. What do you think causes this effect? Is it that a larger wheel has a stabilising effect so you need less ‘spare’ rotational speed to correct forward unbalance? Or maybe it is just you, being mostly used to Cokers I believe, while Mikefule may be least used to Cokers (comparing to other size wheels). And is your suggested formula based on some reasoning or do you just find it conforms to what you found?
Your finding contrasts with the Constant Footspeed Hypothesis Theory that Mikefule so neatly developed, and (of course) also with his own experimental data that he has posted on various occasions. He found almost constant top footspeeds* for wheels of 24, 28 and 36", if anything the effect was reversed from yours.
*I have not seen data from Mikefule (or anyone) for the same cranks on different wheels.
klaasbil_remove_the_spamkiller_@xs4all.nl writes:
><dstone@packer.edu>
>wrote:
>
I wrote how I find that it seems easier to to achieve higher cadences on
larger wheels (Cokers, 28"ers, etc) than smaller wheels (like a 20"ers).
Klaas wrote:
>
>That’s interesting David. What do you think causes this effect? Is it
>that a larger wheel has a stabilising effect so you need less ‘spare’
>rotational speed to correct forward unbalance? Or maybe it is just you,
>being mostly used to Cokers I believe, while Mikefule may be least used
>to Cokers (comparing to other size wheels).
It’s not a Q of “used to” because I have been riding Cokers only for a
couple years and have had my smaller wheels for over 20 years.
My guess is that it’s mostly related to cranks. If I have little 110s on
my Coker and try to compare the cadence with 125s on my 20"er, it’s easy
to see why Roger the Coker wins. If I had 60cm cranks on a 20" uni, then I
could make a fairer comparison. Certainly with even crank lengths, the
Coker wins. In my only time trying a 20" uni with short cranks (110s), it
was clear that higher cadences are possible – maybe 150. So I think most
of the problem is that cranks tend to be finitely small (usually no
smaller than 110s, and most often 125s or so), which means that in going
from the smaller uni to the larger one, you’re more likely to achieve
higher cadences. If you went from a 20" uni with 125s to a Coker with 200
cm cranks, the max cadence would not change much.
>And is your suggested formula based on some reasoning or do you just find
>it conforms to what you found?
The latter.
>
>Your finding contrasts with the Constant Footspeed Hypothesis Theory that
>Mikefule so neatly developed, and (of course) also with his own
>experimental data that he has posted on various occasions. He found
>almost constant top footspeeds* for wheels of 24, 28 and 36", if anything
>the effect was reversed from yours.
I haven’t seen his data. It doesn’t sound right, tho, and my logic (above)
seems to make sense (about crank size being the major factor).
>
Another factor is that the heavy Coker wheel may add its own energy to the
equation in a significant way. And couple that with the small cranks,
you’ve got a speed machine.
