schlumpf…
if Schlumpf uses conventional isis cranks, then yeah. its the whole idea of using cranks for the brakes, you don’t have to modify wide hubs or geared hubs.
I think it makes perfect sense for a road going uni. There seems to be a lot of worry about hitting the disc with you foot/ankle, but in all of the time I’ve ridden bikes I can’t remember ever hitting my foot/ankle against the chainwheel. I like the idea of a mount that bolts on, or maybe an endless band like the way road bike brake levers mount.
I think you could expect better modulation with a disc brake on a 36’er than a rim brake. If you think about it there is more leverage between the rim and the disc, and so you should be able to get finer control; although, not stop as quickly. I also like the idea of using a cable brake rather than a hydraulic. The cable brake would allow for a simple drag lever in line with a standard brake lever so that you could have the best of both worlds.
I was thinking of having an adaptor made that would screw onto the crank arm like a freewheel on a trials bike crank. It would then allow you to use standard 6 bolt rotors.
My fist thought was that people would rather have a standard disk rather than a oddball disk that may or may not work properly with various calipers. You loose a point there
But
You found a readily available crank in almost all usable sizes for unicycling where you would need a brake and allow the use of other (bike) cranks without modification to be used. +1
Are you planning on making various sized rotors? I would be curious to see if 203mm rotor would feel similar on a 36er as a 160 would feel on a 26.
One suggestion I would make right away though would be to make the rotors compatible with Hayes, Magura, and Avid calipers, as far as I understand it they need a slightly wider braking surface than the Shimano calipers but the braking surface looks very wide so those calipers you mentioned might just be the ones tested and confirmed to work with the disk. Am I right?
[/QUOTE]
when we modified a cheap crank for the prototype and bolted on a 160mm 6 bolt rotor, the bolts were 1mm away from the bearing holders -too close. when we decided to use 104mm bcd cranks with 160mm rotors, the bcd was too close. we’re using 180mm rotor, and may also make a 203… but this is a drag brake. this rotor should work with all calipers, as it did with shimano. we need the feedback before we build every option. These are the most common usable standards out there. I’m glad you like the idea.
The disk is an inch closer to the leg because it’s outside the frame, but it’s unlikely to touch the leg while riding. if you rest your leg against it in an other circumstance, after taking it to sunday river… well the risk is your own. how many people have hurt themselves on a chainring while riding their bicycles? you should be fine… but that’s the feedback we’re after. the last discussion of brakes on a crank was the prototype for this.
We haven’t thought our way around the lack of a crank stop spacer, just spacers between the mount and caliper as the square taper wears, remove spacers… There is no extra metal to disperse heat on the disk, but the crank seems like a great heat sink. as far as Q, it’s the same as a chainring on a bicycle, conventional. Am… the seat and pedal seem to keep the disk away from the ground on crashes, however rocks could reach up and smack the disk, what can be bent can be unbent -kinda. I haven’t had to hammer it flat yet, or even bend it yet.
Sorry about that. I seem to be having trouble editing my posts. Sometimes the edits won’t “save” and there seem to be coding issues. That previous post should have had paragraph breaks in it, but they didn’t get coded in…
Anyway, I think what Terry was saying could still apply, but not from wheel tweaking. A bent wheel would screw up rim brakes but not a disc. To do that you’d have to bend the disc, which is also a possibility if you have hard knocks against rocks. But could a disc brake be easier to straighten out? 
We’ll submit one for review! the cranks go on evenly, the part that holds the disk on is slightly outboard of the frame, yet still inboard of the person. hydraulic rim brakes are not light, if any weight penalty for a disk is a trade off for consistency if the rim isn’t perfectly true, the rim surface is beat, if the wheel is covered in whatever… smooth, predictable, reliable.
a negative opinion to start is the most credible opinion once changed!
if you bent the axle, then maybe the disk brakes would be effected, but that’s the least of your issues in that event. HS33’s are great, but host the same issues that all rim brakes do. when you heat the pads, they glaze the rim, when you wobble the wheel, or goo the rim up with something, or get it wet, it’s not as consistent as a disk brake.
as far as the problem you guys are suggesting, look at your frames. the majority of all nicks and dings on mine are about 8" up from the axle… and the ones that are closer are very small and because i did something completely out of the ordinary. the pedal and crank are like a big guard for the majority of the disc, but i wouldn’t suggest crank grabs on that side.
it is a very original, simple, and useful idea, i like it, but i do have to question etching the name into the disc. it seems that the disc would be very reasonably priced, and significantly easier to produce without that.
The pictured 29er is an ISIS hub, so we’re ready for both versions, and I definitely understand the volumes, and potential market. Thanks for the feedback John, and words of encouragement!
[QUOTE=Tirving;1336545]
Wouldn’t the same be true for rim brakes? If the wheel is not true… I get rubbing of my pads.
Plus… I’m pretty sure the axle would have to be bent for it to affect the rotor as it is attached to the cranks, not the wheel specifically. Maybe I’m seeing this wrong but for the rotor to wobble, the crank would also have to wobble… right?[/QUOTE
Right on Tirving. The axis point is the hub, not the rim, so a slightly out of true rim is irrelevant from this standpoint. And to piggy back on another statement, were dealing with light, strong aluminum so we’re not anticipating any significant weight differential issues from the disc side
The disc will be compatible with either a cable pull caliper or a hydraulic piston set up. Good Question JTROPS. We have stuck with the higher end hydraulic for our proto’s, but either will work fine. One question I have back is would the UNI community prefer to buy their own brake to work with this? Or provide a package deal where the caliper, handle, hoses/cable are part of a bundled offering?
Hi Skrobo-
Thanks for the compliment on the useful idea. The name etching, could be tailored to any application, it’s the design, bolt pattern, and unique idea which drives the patent. How would you know where to get them if I didn’t put my name on it? Once you’ve spent the money, you’ll see why I want my companies name on the disc, and not just something generic that could be copied, or not have some sort of identity to the product.
qfactor…
Q is minimal, and the offset is also minimal since they’re bmx cranks.
looks interesting, but tbh as it is now would seem to suit road use more.
I would imagine the disk getting damaged sooner or later in MUni crashes and needing to be replaced ($/hassle), and of more concern is not ankle rubbing during riding, but any part of your body coming into contact with the edge of the disc during crashes. I’ve experienced this myself with test bits and pieces - even safely rounded narrow plates etc turn can into knives during upd’s, slicing skin open. Not a fan of the outboard disc mounting, though there’s not a lot of choice probably atm.
would be interesting to know the true weight installed, though I can’t see it being much less than hs33’s and tbh the weight of hs33’s is a non issue anyway.
would be interesting also to compare the feel and performance of the disc against hs33’s. The hs33’s feel great on the 24, but imo anyway the braking experience degrades slightly as the wheel size increases. related, would be handy to run the disc on a 36’er and have no more rim rubbing on brake.
I think you’d be pretty unlucky to hurt yourself on the disc in a crash (pinned pedals and other pointy bits are far more of a risk IMO), but I do reckon there would be quite a good chance of bending the disc if you dropped the unicycle on rocks (which I do all the time round here!). If that did happen though (and it was too bad to bend back), you could unbolt the disc and still be able to ride home so you wouldn’t be completely stuck. The one in the OP’s picture looks a bit more solid than most bike discs though, so it might be more resiliant.
That’s odd - the performance of a rim brake should be independent of wheel size, whereas a disc brake performance would decrease with increased wheel size. I can’t really comment from experience because my 36er is running a cheap BMX calliper with a v-brake lever that pulls far too much cable, so it’s pretty puny anyway! But overall braking force isn’t that important on unicycles anyway - modulation is what we need, which a disc brake should be pretty good at.
I still think the main benefit of a disc brake is keeping the braking surface out of the mud and grit, so you get consistent braking whatever the ground conditions and avoid the cringeworthy expensive grating sound every time you brake. If I still had a mountain bike I think I’d have gone to discs by now purely for that reason (I seriously thought about it for my winter road bike as well). Some people would want them just because they think it’s cool to have a disc brake as well - although personally I think they’re pretty ugly and rim brakes look much tidier (on bikes as well).
Rob
On a bicycle the q-factor is the distance between the pedals (or better the outside of the cranks at the pedal thread) parallel to the centerline. On unicycles the q-factor is the outward bend of the cranks. Right?
Can you please measure the distance between the pedals. It seams to be wider than other cranks.
Q should always be the distance between the pedals, but as the length of the axle is pretty constant on unicycles the main thing affecting the Q is the shape of the cranks. So people tend to refer to straight cranks as “having no Q factor” and offset cranks as “having more Q factor”, which is not really correct terminology, but people know what it means.
The bottom bracket axle on a bike is usually quite a bit narrower than a unicycle axle, and bike cranks have to angle outwards to clear the chain stays of the frame. So using bike cranks on a unicycle will result in a wider stance (higher Q) than the same cranks on a bike. Unicycle cranks tend to be straighter on average than bike ones for this reason.
Rob
I like the lateral thinking of using the 5 bolt fittings for a chain ring. It looks smart. I can’t help thinking that anyone who rides hard enough to really need a disc brake is going to need something less vulnerable. Neat idea, though.