Has anyone ever considered a brake that works directly on the crown of the tire? Say a lever which presses a roller-type braking mechanism down onto the rubber spinning near/under the seat, at the top of the fork. The roller, like a spinning spool, could have a variable resistance, to strengthen or weaken the force.
2 problems I can see straight away, 1 is the variable braking force that the tyre offers to the mechanism, any variability in the tyre thickness or profile will make a non-uniform force as the tyre rotates. Also, it’ll wear the tyre out twice as fast as a normal braking system.
Loose.
Here is a possible arrangement.
uni brake idea 2.bmp (448 KB)
Well, for discussion, I’m considering my Radial 360’s tire (smooth, round-topped road tyre, and the brake would need to have a larger or equal raduis to the tire’s cross section.
Some old rod-brake roadsters (dutch bikes) had brakes sort of like this, that pushed on the tyre. If you value your life, never borrow one of these bikes off anyone. They’re terrible. You’re not going to get progressive braking by pushing against something that is deformable (the tyre), the tyre pushes in when you brake and does weirdy stuff. You get extra tyre wear and if you’re riding in the rain the brake bit can grab stuff off the tyre and push it in, causing a puncture.
What advantage does it have over a normal brake, it seems more complex, with the variable resistance bit, and relies on a bunch of custom parts rather than just off the shelf bike bits. Also, the simplicity relies a bit on the lever coming out somewhere nice to hold, or else you’re going to need to extend that with another part going up high enough to grab on. It also looks like being quite big and heavy, you’re going to have to build those levers quite strong to make them not bend when you’re pulling sideways on them all the time, and when all the braking force is transmitted into sideways force on the lever.
The other problem is that I think from your diagram, resistance to the roller spinning will cause the front of the lever to move upwards, pushing the brake on harder, and presumably making the resistance change? Like when you have a v-brake setup that isn’t toed in, and it just goes on very suddenly, because the braking action causes the brake to turn on.
I think tyre crossection and bumpyness is likely to make a difference even on a smooth tyre, on a rim brake you can notice tiny rim differences, which are far smaller than the kind of bumps you’ll get in a tyre, especially one that you’ve worn down unevenly, as is often the case on unicycles.
What problem is it designed to fix?
Joe
Penny farthings (and some other early cycles) used “spoon brakes”: a lever at the handlebar that pushed a concave metal “pad” against the surface of the tyre.
This is very similar to your idea, except that yours has a roller. So, the idea of a brake acting on the rolling surface of the tyre is not new.
In cycling, there are five basic types of brake:
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Fixed wheel - which most unis have anyway. Fixed wheel offers fine control of speed, but is not good for sudden braking from high speed. It is also tiring on long descents, which is why many unicyclists add brakes to their unis.
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Rim brakes in which pads of rubber, leather, polymers etc. are pressed against the braking surfaces on the rim. The advantage is simplicity. The pad can be chosen for its friction characteristics. However the rim is dual purpose: a braking surface and part of the structure of the wheel. Therefore, rim brakes do not offer optimal friction, and are a compromise. Also, as the rim is very near to theroad, it will pick up water, grit and grime which affect the performance of the brakes.
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Internal hub brakes, also known as drum brakes. Here, both braking surfaces (the pad/shoe and the lining of the drum) can be selected for their friction characteristics. That is good. A drum can collect and trap water which affects operation, which is bad. The drum is a structural part of the hub and needs to be designed in from the start. The moving parts are concealed, and access is fiddly, so maintenance is an issue.
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External hub brakes: disc brakes. These can be operated by hydraulics or cables. Again, the choice of braking surfaces (pads and disc) can be made purely on the basis of friction characteristics. The hub needs to be manufactured in such a way that a disc can be fitted. There also needs to be somewhere to mount the calipers. Disc brakes are potentially the most powerful brakes for all wheeled vehicles, if cost is not an issue, and if there is space to fit them.
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Dragging your shoes on the floor. This works if there is plenty of room in which to stop, and if they are old shoes anyway, and if your mother doesn’t see you doing it. It is a very difficult skill on a unicycle, and not a popular choice.
We now look at number 6: the brake that operates directly on the surface of the tyre. It is possible to choose the “pad” (or roller) for its friction characteristics. However, the tyre has other characteristics - not just friction, but also knobbly grip, steering and suspension. So the profile of the tyre, its texture, and its pressure may vary considerably from uni to uni. Also, if riding off road, the tyre may well become clagged up with mud. This option therefore offers many disadvantages over most of the existing models, and no obvious advantages.
Do unicycles need brakes? Some people say yes. So what do they do with those brakes? If you slam on the brakes for an emergency stop, you will probably fall off. Therefore, the ideal uses for the brake are gently scrubbing off speed, or acting as a constant drag on long or steep descents - or for holding the wheel steady when doing trials manoevres, I guess. These tasks are well within the capabilities of the various types of rim brake (centre pull or side pull calliper, cantilever, V brake etc.) that are readily available.
Nice idea, but, on analysis, not a useful one. But don’t let that discourage you, because it is only by throwing new ideas open for discussion that progress can be made.
I just posted this in the Coker Design thread, and it seems more appropriate here:
I hope this isn’t too far off-topic because it’s mostly fantasy and not a real suggestion for coker design. But I wonder if some of the brilliant minds on this forum could develop something like this…a mass-adjusting braking system. Wouldn’t it be great if there was a practical way of combining traditional braking with something that kicked the center of gravity simultaneously backward (or maybe a little sooner than simultaneously) to take some of the unforgiving face-plant tendencies of braking out of play? I know that the body through leaning is the organic way to do this, but I have yet to use a brake for any purpose other than a very slight reliever for my legs on long descents (and I’ve had some scary moments letting the brake off, too). It seems like if there was a counter-weight mechanically connected to the brake handle that moved back when you applied the brake, and came back forward when you released it, that you could have a better chance of staying on the unicycle when using the brake (especially in a situation that requires a spontaneous adjustment in speed).
I’m sure that besides the weight issue, there must be other problems with this, but I’m too short on brain cells to figure that out. What do you think?
I wish someone would cook up an alternative for the Magura per hard core Muni. I’ve got two Maguras and am constantly swapping them out and sending the busted one back to the factory for blown hoses, etc., then a few weks later repeating the process with the good one. They’re simply too fussy and fragile to hold up to all the rocks and falling we do. But there’s nothing else I know of that works nearly as well.
Gotta wonder if some DH rim/cable brake isn’t available to ease my grief, though I suspect clearance might be an issue. The “Dutch Solution” doesn’t sound like a viable alternative, however. Nor does the Fred Flintstone method (foot dragging).
Go figure . . .
JL
I’ve found my Maggies to be perfectly serviceable and tough, if you have lots of trouble with hoses try upgrading to braided metal hoses, that should stop rubbing/splitting issues.
Loose.
Unfortunately, this would be contrary to Newton’s laws of motion, but other than that, it might just work.
The Japanese longbow is the same today as centuries ago. If the archer misses his target, he turns his atention to his technique and practises to improve it.
The western longbow, with its balance weights and telescopic sights is almost unrecogniseable compared to the one that controlled the field of battle at Agincourt.
Is it easier to work harder to earn money to spend on stuff to make it easier to do what you enjoy than it is to work harder improving at the stuff you enjoy?
that one looks like it’d work.
i wouldn’t mind trying it…
I had this briefly on my uni until I got the brakes adjusted correctly so they work progressively rather than just on and off. If you’ve got v-brakes, you do it like on here where it says ‘Setting Pads’ Linear Pull Brake Service | Park Tool with a shim (piece of cardboard,or rubber band). Basically just loosen the pad, squeeze the lever tight until the pad is sitting nicely and is toed in correctly, tighten up the pad and then release the lever.
If you’ve got maguras, there’s probably something you can do to adjust the angle so that they work properly, but I don’t know what? Anyone?
Basically, the key thing is to make it so that putting the brake on doesn’t make the pads pull onto the rim and brake more. This way you can simply control the power by varying your pull, and slowly let off the brake, rather than suddenly releasing the power. I’m not sure if the coker frame doesn’t help here either, if it twists much under braking, that could force the pads to turn into the frame maybe.
vivalargo have you tried a set of well set up v-brakes? I believe Shimano Deore rim brakes will fit over a 26"x3" tyre, and when you set them up right, they work fantastically, from my (limited) experience of maguras, the v-brakes I’ve ridden with feel at least as good as maguras to me. As long as your brake mounts are behind the frame rather than in front, there shouldn’t be any problems with hitting the brake arms. It might be slightly hassle for seat in front if you do that a lot, but I doubt it. Joe McLean over here has v-brakes on his muni and they appear reliable in the long term, with a whole lot of riding in them. I’ve got them on my Schlumpf 29er and they were fantastic for the about 15 miles of pretty steep riding that I got to use them for, before the Schlumpf frame snapped. They’re oh oh so easy to fit too. Takes 10 minutes to install too and has no bleeding or tube broken hassles, and you can take a spare cable in the unlikely event of breaking it on the trail.
Joe
Thanks, Joe…I will get my V-brake adjusted per your advice. Maybe I’ll be more inclined to use it if it works better.
Mike–
I pride myself in NOT being a lawbreaker, Newton’s or any others. While you’ve pointed out that my description of my lame idea is indeed faulty, maybe this little sketch would suffice to explain what my words didn’t…sorry.
http://www.unicyclist.com/gallery/?g2_view=core.ShowItem&g2_itemId=173283
Even though the longbow was good enough to win the battle, it seems that mankind has found plenty of new ways to kill people. I see this trivial waste of my own time (and now yours) quite harmless and in the spirit of good fun. I didn’t mean to trigger arrogant sarcasm.
Sorry. Cultural differences. Over here, that would be heavy irony as part of a robust but good natured debate. It’s a British thing - it’s how we bond. This is an international forum and I should have made allowances. I apologise for any offence caused.:o
Thanks for the clarification, Mike. Overly sensitive on my part. Sorry. I’m a sissy.:o
Hi,
I like the spool brake idea for a road uni. Why not build one and let us know how it works out. Here is the set up that I use it cost $20.00 Canadian to put together.
No problem.
whatever happened to the guy making the magnetic-controlled coker brake?
http://mc2.elijahtech.com/index.php
I have the braided cables but we’re always trying hard stuff and so every ride is good for at least a dozen falls. The cables hold up but not the fittings . . . or me.
JL
I encourage anyone to tackle the roller brake, you might be able to make something useful. But I’d pay attention to the previous hundred years of bicycle technology to help save you some time. Find out what’s already known to not work well. After that, consider how many parts would have to be custom made compared to a more traditional brake system.
Another drawback to a tire-based brake that I didn’t see mentioned above is stuff on the tire. Water would probably be a major problem. Dirt? Mud?
The balance-point adjusting concept is something that would be nice to have, but like Mike said I’m not sure that you can arrive at it without cheating or some heavy duty electronics and sensors (aka Segway). The idea of adding extra weight, just to make it easier to slow down, seems like a step in the wrong direction (except for a pure fitness vehicle). You need to get the wheel out in front of you before applying brakes, and the more in front it is, the harder you can apply the brakes. But also the higher the consequences and tighter the tolerances to keep everything under control. It would be kind of like the unicycle equivalent of antilock brakes.
This of course all depends on the individual; how much available time they have vs. budget. Some of us are into other things, or have families, etc.
Originally I thought Mike’s clever quote was comparing buying existing technology (more money but less time) with designing/testing/making your own stuff (maybe less money but way more time). It all depends what you’re into. I love the fact that so many people are experimenting and coming up with new ideas for unicycling these days. Keep it up!