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Old 2010-03-01, 08:42 PM   #31
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[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
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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
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Old 2010-03-01, 08:48 PM   #32
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Quote:
Originally Posted by jtrops View Post
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.
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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?
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Old 2010-03-01, 08:58 PM   #33
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Quote:
Originally Posted by skrobo View Post
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.
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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.
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Old 2010-03-01, 11:35 PM   #34
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qfactor...

Q is minimal, and the offset is also minimal since they're bmx cranks.
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Old 2010-03-02, 10:26 AM   #35
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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.
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Old 2010-03-02, 10:58 AM   #36
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Quote:
Originally Posted by lunicycle View Post
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 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.

Quote:
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.
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).

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Old 2010-03-03, 11:25 AM   #37
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Quote:
Originally Posted by kb1jki View Post
Q is minimal, and the offset is also minimal since they're bmx cranks.
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.
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Old 2010-03-03, 11:39 AM   #38
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Quote:
Originally Posted by Eiserne Hand View Post
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?
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.

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Old 2010-03-03, 05:53 PM   #39
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Q

Quote:
Originally Posted by Eiserne Hand View Post
Can you please measure the distance between the pedals. It seams to be wider than other cranks.
looks like 20.4cm how does that compare?
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Old 2010-03-03, 06:36 PM   #40
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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.
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Old 2010-03-04, 05:19 AM   #41
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Q Factor variance

[QUOTE=rob.northcott;1337067]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, thanks for the detail, and you've got me intrigued to find out the Q Factor for a few different applications. Whether our crank choice changes Q variance from hub to hub? Or if we took the standard crank Q for the Original equipment and compared it against the current 20.4 measurement?
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Old 2010-03-04, 05:26 AM   #42
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OKay Lunicycle, good idea. We'll get a full dressed weight for the complete uni, keeping in mind that will include Mount, Rotor, cranks and handle. I have a KH29 with a Magura as well, and we'll report the Weigh IN amounts :-)

Last edited by Mountainuni1; 2010-03-04 at 05:27 AM.
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Old 2010-03-04, 06:26 AM   #43
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Quote:
Originally Posted by kb1jki View Post
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.
Yah it looks like it should work with most calipers. It just seemed like you were limiting what calipers you could use in the description.

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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.
I think I would suggest the opposite approach. Space the disk away from the crank and have the caliper in a fairly fixed position. This would help with people like me who like experimenting with different setups and constantly changing things around. If you space the disk the built in adjustment in the calipers could take care of the small variance you would have left.

Quote:
Originally Posted by Mountainuni1 View Post
Rob, thanks for the detail, and you've got me intrigued to find out the Q Factor for a few different applications. Whether our crank choice changes Q variance from hub to hub? Or if we took the standard crank Q for the Original equipment and compared it against the current 20.4 measurement?
All the ISIS hubs (except the Nimbus Super-wide) are specked to the same axle dimensions. The Koxx hubs tend to be on the larger side for their tolerances and the cranks might sit a bit further outboard on them.

Some old square taper hubs are funny widths but pertnear everything is being made with 100mm bearing spacing now.

Your cranks do look kind of wide but you still need to clear the brake calibre.
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Old 2010-03-04, 10:09 AM   #44
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Quote:
Originally Posted by rob.northcott View Post
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!).
Murphy's law is that any exposed edge like the disc (doesn't even need to be sharp or sticking out too far, got the scars...) is going to end up making contact with your body during a crash. Sorry, not a fan of the outboard disc for MUni for that reason alone.

I agree also re too prone to damaging the disc.

HS33's do a good job on both counts - no risk of injuring rider during UPD, and unlikely to get damaged during UPD.

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Originally Posted by rob.northcott View Post
That's odd - the performance of a rim brake should be independent of wheel size...
Not really odd just my POV

Perhaps I wasn't clear enough - jump on a 24", go down a trail, apply the brake. jump on a 36'er, do the same. The braking experience is not the same due I would guess to a lot of factors including a perception of how granular braking and riding control is, based on the distance the wheel covers relative to crank etc.

For sure the outboard disc looks to be an effective/cheap way to retrofit disc brakes to uni's and it'll be interesting to hear what guys have to say when they use it, but tbh they don't appeal to me much as they are for MUni, especially when the hs33's are already doing the job.
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Last edited by lunicycle; 2010-03-04 at 10:10 AM.
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Old 2010-03-04, 11:10 AM   #45
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Quote:
Originally Posted by lunicycle View Post
Murphy's law is that any exposed edge like the disc (doesn't even need to be sharp or sticking out too far, got the scars...) is going to end up making contact with your body during a crash.
I know what you mean - that's one of the main reasons I've not tried any sort of extended handle yet (well, that and I can't be arsed to build one!)

Quote:
Originally Posted by me
That's odd - the performance of a rim brake should be independent of wheel size...
Quote:
Originally Posted by lunicycle
Not really odd just my POV
That's why I said it was odd - not trying to argue, I just meant that in theory a rim brake shouldn't really be affected by wheel size, so it's interesting that practical experience says otherwise. I suppose it's because of the difference in gearing and the feel of the ride. I've got HS33s on my 26x3 and 29er, and they feel pretty similar, but then there's not very much difference in size. Like I said, my coker's got a very different brake setup, so I can't really compare it directly (it really needs a lever that pulls less cable).

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