Short of wearing a lead weight belt, I can see no way of controlling my larger unis on steep descents unless I fit brakes.
So, how is this done? Do I need braze-on bosses on the forks (which would spoil the chrome finish) or is there another way?
Thanks.
Hmm, I think Sarah drilled the bottom of the crown on her Coker and installed a caliper brake. This is probably the route I would go too, as I think a V-brake is overkill on a coker. cheers… Joe
if you do want a V-brake,you can put one on without welding with the Big Cheese adapter.
Re: Brakes? How?
Mikefule <Mikefule.5ooan@timelimit.unicyclist.com> wrote in message news:<Mikefule.5ooan@timelimit.unicyclist.com>…
> Short of wearing a lead weight belt, I can see no way of controlling my
> larger unis on steep descents unless I fit brakes.
I may be missing something, but how would a lead weight belt help
control on descends? It would drag you down with even more force,
right?
In the best of Dutch traditions, the Echelon-thingy has been
euthanasia’ed.
Re: Re: Brakes? How?
Think about the unicycle as a sort of lever. The fulcrum is where the tyre contacts the ground. The unicycle itself, and any of your weight which is on the seat is pushing down (via the hub) on the downhill side of the fulcrum. That part of your weight which is on the uphill pedal is on the uphill side of the fulcrum. If you stand on the pedal on a steep descent, most of your weight is being used to slow down the descent. The heavier you are, the more you can slow it down.
Put more simply: as you go down hill, the back pedal rises. You are using your bodyweight to stop it rising. The heavier you are, the easier it is to stop it rising. Wear a lead weightbelt and you will effectively have a greater bodyweight. (The suggestion to wear a weightbelt is of course made in jest, but the principle would work.)
Going up hill, extra bodyweight will help you to shift the unicycle, but your weight will be working against you as well because even though on each ‘step’ your weight is falling as it pushes the pedal down, you have to lift your weight a little bit higher for the start of each ‘step’ and over the length of the ascent, of course, you have to lift your bodyweight all the way to the top of the hill.
If you sit on the saddle rather than standing on the pedals on a descent, and perhaps pull up on the seat front for extra torque then your bodyweight is transmitted through the unicycle to the hub and therefore acts on the downhill side of the ‘lever’.
Mathematically, it gets complicated, because your weight is always pushing vertically downwards, but is transmitted through the crank which is not always perfectly horizontal. Only a proportion of your bodyweight is transmitted in a useful way when the crank is at any other angle. (It’s not really helping much when the crank is vertical, for example.) This is all to do with sines and cosines and stuff. However, hang on to that thought that if you are stopping the pedal from rising, then the heavier you are, the easier it is.
well, almost
not quite right!
On a steep descent, the easiert way to slow yourself down is to grab hold of the seat and pull up at the same time as your pushing down with your foot on the peddle upstroke. This has nothing to do with body weight and everything to do with the down force applied by your leg, and the upforce applied by your arm! I assure you, a weight belt wont help here, only more force!
And by the way, big buggers usually go down hill faster! cause once they get rolling, its harder to stop them!
James
RE: Brakes? How?
> is on the uphill side of the fulcrum. If you stand on the pedal on a
> steep descent, most of your weight is being used to slow down the
> descent. The heavier you are, the more you can slow it down.
Sounds great on paper…
> effectively have a greater bodyweight. (The suggestion to wear a
> weightbelt is of course made in jest, but the principle would work.)
Realizing the jest, but I don’t think so.
> Going up hill, extra bodyweight will help you to shift the
> unicycle,
No, extra weight always makes the unicycle harder to shift. A heavier wheel
is harder to move, and a heavily-laden rider is harder to shift for control.
> If you sit on the saddle rather than standing on the pedals on a
> descent, and perhaps pull up on the seat front for extra torque then
> your bodyweight is transmitted through the unicycle to the hub and
> therefore acts on the downhill side of the ‘lever’.
I think Mike needs to ride down more steep hills. What he’s leaving out of
his equations will become painfully obvious after a few long ones.
Your body is made up of bones and muscles. This mechanical system works
better in some positions than others. Sitting down, your legs are bent more.
Try walking any distance with your legs bent, so you’re crouching down low.
This is the equivalent of pedaling seated vs. standing. Though the seat
takes part of your weight when you’re sitting, you lose enough leg
efficiency that it is only useful for less strenuous forms of riding (we’re
talking about a steep hill here).
When riding down something steep enough to make one consider adding a
weight belt, traction is an issue. More weight=less traction on a slope
(unless you change tires). If you add too much weight, or if the trail is
too steep, you’ll just slide out.
The extra weight is heavy. For all the good it does during the part of the
pedal stroke where it’s effective, you have to resist it for the entire
rotation of the wheel, including when the pedal is back. Riding downhill
causes your muscles to work hard while they’re being extended, rather than
contracted. From my experience, this makes them more sore than normal use.
> hang on to that thought that if you are stopping the pedal
> from rising, then the heavier you are, the easier it is.
This is perfectly true. Holding the wheel from moving, with extra weight, on
a steep hill, is probably effective. But for riding? Two words – FIELD TEST
Next weekend I am joining a group of riders doing the Downieville Downhill,
a famous mountain bike ride in the nearby Sierra Nevada. With a shuttle ride
up, it’s about 4000’ downhill in 18-20 miles. The one other time I did this,
with David Poznanter and Brett Bymaster, David and I were both super-sore
for about a week. It was the descent, not the miles. Nathan Hoover and
Bronson Silva will have brakes this time, but Scott Arnold, Tim Bustos and I
will not. Oh well.
And no, I do not volunteer to wear the weight belt!
Stay on top,
John Foss, the Uni-Cyclone
jfoss@unicycling.com
Howard Stern: “How many wheels does a unicycle have?”
The beautiful but vacant, recently-crowned Miss Howard Stern:
“…Four?”
Woooo! Hold on!
I made a throwaway jokey aside in a request for advice; someone queried it, half-jokingly; I responded in a fairly light hearted way and now I’m being criticized as if it were a physics exam answer. Steady on. This is a game we play for fun.
That said, here’s a clearer version of the rather minor point I was making:
A unicycle can be looked on as a sort of lever. It isn’t a simple lever, and the sums are more complex than for a set of weighing scales or a see saw because the fulcrum moves relative to the ends of the lever depending on the steepness of the slope.
However, if you ignore the complexities, there is a fulcrum (the contact between the tyre and the ground) and then the length of the crank gives one side of the lever, and the radius of the wheel gives the other.
In use, there are many variables, including the steepness of the slope. However, if we assume a constant downwards slope with a smooth surface, then we can limit the variables to the design of the uni, the weight of the rider, and the riding technique used.
Going down a slope under full control is a process of releasing the potential energy by allowing the pedals to rise at a controlled rate. (As opposed to letting the uni run away and simply trying to stay on.)
So, what variables can we control?
Note: the ratio of crank length to wheel radius is important, but the absolute length of the crank also has an effect because of ease or difficulty of use. A six inch crank on a 24 inch wheel is OK. A 9 inch crank on a 36 would be the same ratio, but I’d find it unrideable.
Note: this is where I made the flippant remark about the weight belt. My serious point is that quite simply, a heavier rider can, all other things being equal, apply a greater downforce on the pedal.
In practice, the options go something like this when the pedal starts to rise faster than the rider would like:
a) Push harder on the pedal.
b) if you need more force, stand on the pedal.
c) and if you still need more, pull on the seat/handle.
As a matter of experience (and here I bow to John Foss’ greater experience) it may be preferable to use the pulling on the seat technique rather than the standing on the pedal technique. That is not an argument that my physics was wrong, only that there is a better way to achieve the same result in pratice.
I do know that as a one time very keen bicyclist and tandemist, touring with camping loads in mountain country, my first line of attack on inclines was to stand on the pedals, and my second was to pull against the bars.
I also know that my stoker on the tandem, who had less room due to the frame design, reached a point on steep ascents where she was doing more harm than good because she couldn’t stand on the pedals and could only pull on the bars. We discovered this after slogging up Gospel Pass - she got off to open a gate and I rode through it and up the next steep section easily. (We are now divorced. ;0) )
I also know that today I rode fairly easily down some declines which I found unrideable a month or two back and I put this down almost entirely to the longer cranks I’ve fitted.
So, I’m not advocating weightbelts, but I do stand by my general point that if I were heavier, I would have more control of my speed on descents. Nevertheless, some constructive advice from the experts on how to fit brakes to the Coker would be much appreciated, that being where this thread started. :0)
you have been given two good idea’s already.short of welding there is no better solution than drilling a hole for a sidepull brake or using an adapter.i like the Big Cheese one because its alluminum but its $35 bucks at bike stores.there will be a cheaper steel one on the market soon.
here is a better picture of the Big Cheeze on a recumbent.hope this helps.
not if that huge steel rim is wet.
Re: Brakes? How?
>here is a better picture of the Big Cheeze on a recumbent.hope this
>helps.
Thanx alot Jagur for the pic, but I was wondering (I don’t know if this has
been asked before and if so, I apologise) will that adapter fit over a 3" wide
tire? also do you think this adapter will work with the nimbus II 28" (with a
24" wheel)?
thanx in advance
-Dylan
i doubt it will work with a 3.0 tire,nothing seams to work with those(adapter wise)
i havent put it on my Sem 29er yet but i will make it work(i know it will work)
well
i wouldnt recomend the big cheese adapter, specifically because the force of a v-brake or magura will probably snap the bolt that holds it onto the fork!
Instead, why not just go to a bike frame makers, and get them to weld a set of bosses on, it wont cost much!
One more comment, a heavier person wont be able to stop the uni faster. have you ever seen a overweight person sprinting on a track bike? nothing to do with wieght, everything to do with strength in legs! large doesnt mean strong!
James
Re: Brakes? How?
klaas123@xs4all.nl (Klaas Bil) wrote in message news:<a4088c64.0206032028.141b762e@posting.google.com>…
> Mikefule <Mikefule.5ooan@timelimit.unicyclist.com> wrote in message news:<Mikefule.5ooan@timelimit.unicyclist.com>…
> > Short of wearing a lead weight belt, I can see no way of controlling my
> > larger unis on steep descents unless I fit brakes.
>
> I may be missing something, but how would a lead weight belt help
> control on descends? It would drag you down with even more force,
> right?
>
> Klaas Bil
actualy weight has no direct effect on speed due to gravity. the
lead belt may however stablize the rider making it require more force
to change the riders reletive position atop the corker. also added
weight may have some effect on friction between the tire and the
ground, also within the bearings. this may help slow the uni down by
some degree that is problebly measurable in some lab somewhere.
really haper should be answering this question
trevor andersen
Re: Brakes? How?
Mikefule <Mikefule.5qo1y@timelimit.unicyclist.com> wrote in message news:<Mikefule.5qo1y@timelimit.unicyclist.com>…
> Woooo! Hold on!
>
> I made a throwaway jokey aside in a request for advice; someone queried
> it, half-jokingly; I responded in a fairly light hearted way and now
> I’m being criticized as if it were a physics exam answer. Steady on.
> This is a game we play for fun.
>
but hey, it brings up good points that are worth talking about.
wether or not you personaly were right or wrong, it gives us a chace
to think about what it really is that slows us down, adn what we can
do to improve our riding. its all good
trevor andersen
I haven’t looked rigorously, but in fact if you weigh more, you have more momentum when moving. You may be able to stomp harder on the back pedal when trying to stop, but you are opposing a greater momentum, so you must stomp harder to stop as fast from the same speed. Being heavier won’t help anything.
-gauss
Re: well
But something different is happening there. On a bicycle at high speed, the rider is spinning the cranks and is aiming for as circular a movement of the feet as possible. With clips/straps/cleats (etc.) the rider actually exerts an upwards force on one pedal at the same time as the downward force on the other pedal. Additionally, the rider is able to push the pedal forwards at the top and backwards at the bottom. (Note: most every day cyclists don’t do this, and I suspect racing cyclists only pull up on the pedals for short bursts. It hurts!)
On a uni, sprinting, all of this is possible except the upwards force - unless you are willing to wear straps/clips/cleats etc. In which case you can only read this if you have a laptop at your hospital bed. ;0)
BUT I was specifically talking about controlled descents. I have in mind the bit where you go over the edge and the hill is pretty steep, and it’s too long to just let the uni do its own thing for a few yards before recovering full control.
A few weeks ago, I dropped over a steeper edge than expected, and the sudden ‘kick back’ of the rear pedal literally lifted me out of the saddle and catapulted me some distance. This was largely due to carelessness on my part.
On several other rides, I have come to long steep descents and I have resorted to standing on the pedals and trying to control the descent ‘one step at a time’, letting the back pedal rise, but as slowly as I could achieve. There comes a point where I have to pull up on the front of the seat, to force my foot down against the pedal. If I were heavier, this point would come slightly later.
Do a thought experiment here: imagine an ultimate wheel with a wide flat section tyre. That is, it would stand on the flat without falling over sideways. I say ultimate wheel simply to eliminate the fork and seat falling over. An equivalent weight could be suspended from the axle if you insist.
Now stand this ‘idealised’ wheel on the flat. It just sits there.
Now put a small weight on one pedal. The weight falls, pulling the crank round and moving the wheel until the pedal is at bottom dead centre.
Now take that weight off and reposition the wheel with the cranks at horizontal.
Now, using the knurled knob provided for the purpose, tip the ground so that the wheel is facing up/down the slope.
The wheel rolls down the slope, right?
Now, do the same, but hold the wheel steady and hang a small weight on the pedal as before. With the right amount of weight, the wheel will stand on the slope without rolling down.
Now steepen the slope. You need more weight on the pedal to achieve equilibrium.
(Or you need a longer crank or a smaller wheel.)
Ignoring problems arising from the tyre slipping as the slope gets steeper, it is easy to see that the steeper the slope, the more weight you need on the uphill pedal to achieve equilibrium.
As you ride down a slope, step by step (rather than spinning frantically) what you are doing is transferring most of your body weight to the uphill pedal to prevent it from rising. If you run out of bodyweight, either the unicycle starts to accelerate out of control, or you have to apply a brake, or you have to augment your weight by pulling up on the saddle.
So, more weight = more control in this specific situation.
Going up hill, more weight gives more torque, but at the expense of the fact that you have to lift that weight all the way up the hill. Thus, a heavy rider may be able to get the uni to go up a steeper slope, but will have to work harder than a lighter rider to get up a given hill.
On the flat, the rider’s weight will make little difference except perhaps in the limited case of accelerating/decelerating on a big wheel with small cranks.
I used to ride a recumbent bicycle. On that, you couldn’t get any of your weight over the pedals, and the pushing force was achieved by bracing your back against the back of the seat. That was on the forward stroke of the pedal, rather than the downward stroke. Same principle, though.
It all comes down to the length of the lever (ratio of the gears) and the amount of force you can apply in the necessary direction.
Yes, I understand: You make more torque if you weigh more, but you also have more MOMENTUM. That is mass*velocity=momentum. maximum Torque = mass * crank length when the cranks are parallel to the ground and neglecting dynamic affects. so if you multiply mass times a factor x your torque goes up as you predict. Your momentum goes up by the same factor. You won’t stop any faster.
-gauss
Not to step on Mike’s toes, I think he is a cool guy, but here is the danger of “thought experiment” without thinking of the science that should accompany it. If you actually look at the statics, you can see that mass has nothing to do with it.
In the drawing below the weight on the crank applies a counterclockwise moment to the whole system (system = weight+massless wheel). The moment is R1* mg. The wheel contacts the ground at point A. Gravity wants the wheel to roll down. The force due to gravity at A can be decomposed into a component in the ramp direction (tangential) and one 90 degrees from that(normal). The normal force from gravity we don’t care about unless we care about friction. The tangential component serves to rotate the wheel in a clockwise direction (newton’s third law). The moment here is R2mgsin( alpha). So for the wheel to be still, the two moments must be equal (to cancel out) so: R1mg=R2mg*sin (alpha). Dividing through by mg and cleaning gives R1/R2=sin(alpha)
So here is the surprising, but very true result that the angle or slope at which the wheel begins to turn depends not on the mass, but on the ratio of the crank length to the wheel radius.
This sort of goes back to what I was saying about how increased momentum cancels the greater torque applied by a bigger guy.
We’ve already gone too deep into this and would be better off riding the bloomin’ things, but…
Your diagram very clearly illustrates one aspect of a complex problem. My argument relates to a different aspect of the same problem. I do not think our positions are mutually exclusive.
Clearly, the tip of the crank (or strictly, the centre of the pedal spindle) needs to be further uphill than the contact point between the tyre and the ground. Thus, a longer crank will allow the uni to remain static on a steeper slope.
However, returning to the crank as a lever, even a crank equal to 99% of the wheel radius wouldn’t stop the uni rolling down the hill without some weight on it. At the other extreme, a crank reaching only 10mm past the tyre/ground interface would need more downforce on it to hold the uni static than a crank reaching 50 mm past the tyre/ground interface.
As for the momentum comments: I’m really talking here about the type of descent in which the uni is totally under control which means that the rider could by choice, stop it at any moment. This is different from simply under control in which the rider is confident of his/her ability to stay on, steer, and stop at the bottom. A stationary unicycle has no momentum.
Perhaps (I honestly don’t know) other riders don’t aim for this. I think of myself as quite a ‘thoughtful’ rider in that I am at my happiest ‘picking’ my way along a trail, considering the obstacles and overcoming them one by one - as opposed to blasting into them at full speed relying on momentum to see me through. (I have to say that a few days with a Coker is teaching me the merits of the blast and hope approach.
Perhaps my ‘picking my way’ approach comes from 15 years relying on a very basic 20 incher with loose and rattly lollipop bearings. I had to find my way though mazes of wheeltraps whereas now I am equiped to regard those wheeltraps as part of the challenge.
Anyway, positively my last word on this weight issue is that I think that the weight of the rider in certain circumstances, as specified previously, is a significant factor in the degree of control the rider can exercise on steep descents, but I accept it is only one factor among many, the most notable of which are crank length, wheel radius and the technique used by the rider. I do not propose to quantify or prioritise these factors. 'Nuff said from me. :0) (Finally, whilst it’s nice of you to call me cool, don’t forget I’m a Morris dancer, a breed seldom associated with coolity.)