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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 09-26-06, 01:36 PM   #1
LóFarkas
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Disc front hub, bolt-on cog - report

So here is the report I promised in another thread ages ago.

The wheel is done, I went on the first ride with it today. Perfect, not a single glitch, not even as much as a ping from the spokes or noise from the cog.

Parts: ****-man-o XT MTB disc front hub, *****-man-o DX cog drilled, 32 DT Revo spokes (2-1.5-2, crazy light), Mach1 CFX rim, threaded axle, nuts, spacers, bolts.

Total cost: about $70. Posh butted spokes didn't help, but who cares, it's just money
Total weight: 1060 grams including cog, bolts, and axle nuts. 960 w/o cog and its bolts IIRC, still including axle nuts. Not bad.

The wheelbuilding and spacing jobs are relatively straighforward, so I'll skip that. The hub has a ~40mm "chainline", so not a lot of respacing needed if you want 42. I run a 45, which ended up landing the rim almost perfectly in the centre between the two flanges - makes for a nice and strong, laterally stiff wheel.

The cog was not easy to drill... Here it is after I atttacked it freehand, marking the hole places with a pen (BTW, the ISO disc bolts are on a circle of 44mm diameter, which makes the 6 holes exactly 22mm apart from each other, and from the centre as well. 5mm holes needed for the M5 bolts, about 12mm is the ideal bolt length): (You can see that I had already filed off the ridges that hold it on the cassette... They interfere with the XT. Not too hard, a round file and 30 min free time is needed, plus a vise.)

The small dent is all I achieved trying to drill.
I realised this was not gonna work, so I took it to a machinist/mechanic friend who has a drill press. Still no dice. Normal drilll bits won't go through the hardened steel (good job, Shimano...).

In the end, another friend, a mechanic at a railway company who has a massive workshop at his disposal and works with steel every day drilled it with vidia bits (AFAIK thats another name for carbide bits). "Bits" is not a typo... two were ruined in the process. The third achieved final victory. At least his company paid for them

So be prepared that the DX will put up a fight.

I had to correct some holes with a small round file cuz they weren't aligned-surprisingly easy given how hard it was to drill.

Here it is built up:


On the bike:

More pics on my new flickr account: http://www.flickr.com/photos/lofarkas/



Edit: Hmmm, so how do you post flickr images again? I used the URL from the top of the page for the cog pic. I see a red X. I used the address in the "properties" box for the rest, I see the address in text...

Last edited by LóFarkas; 09-26-06 at 11:54 PM.
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Old 09-26-06, 01:48 PM   #2
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Wow!
Great job with that!

The 6 bolts and solid axle make it look like a pretty mean setup.
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Old 09-26-06, 02:52 PM   #3
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Very cool. Some company needs to start producing cogs pre-drilled. Is that a 16t DX cog?
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Old 09-26-06, 02:58 PM   #4
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Nice work!!! Slipped into vertical dropouts as well!
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Old 09-26-06, 03:02 PM   #5
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Quote:
Originally Posted by darkmother
Very cool. Some company needs to start producing cogs pre-drilled. Is that a 16t DX cog?
before anyone beats me to it:
Boone Titatnium ISO Disc Brake Fixed Gear Cog
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Old 09-26-06, 03:43 PM   #6
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Isn't Kogswell making some cogs like this too?
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Old 09-26-06, 04:07 PM   #7
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Very cool project and excellent implementation.

So, how do bolt-on cogs compare to screw-on cogs?

I know the pros and cons of screw on. What are the pros and cons of bolt-ons?
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Old 09-26-06, 04:48 PM   #8
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Can't strip bolt on cogs
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Old 09-26-06, 05:04 PM   #9
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sure you can. i'm sure some mtb'ers here have stripped their disc hubs.
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Old 09-26-06, 05:06 PM   #10
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I think you are tlaking about something else
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Old 09-26-06, 05:24 PM   #11
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Quote:
Originally Posted by abeyance
sure you can. i'm sure some mtb'ers here have stripped their disc hubs.
I've never heard of it. Even downhillers, who run massive discs and multi-caliper brakes don't seem to be able to cause the attachment of the brake disc to fail.
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Old 09-26-06, 06:02 PM   #12
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Bolt on cogs wouldn't get stripped. The thread's in the wrong direction relative to the force. If they were to fail, the mode would probably be shearing the bolt heads clean off.
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Old 09-26-06, 06:20 PM   #13
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I think the people that strip their MTB hubs are ham fisted when upsizing their rotors.
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Old 09-26-06, 06:58 PM   #14
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Quote:
Originally Posted by LóFarkas
Edit: Hmmm, so how do you post flickr images again? I used the URL from the top of the page for the cog pic. I see a red X. I used the address in the "properties" box for the rest, I see the address in text...
I think (haven't actually tried it) take the "?v=0" or whatever it is off the end, so that they all end in .jpg only.. that stuff is just dynamic image scripts, although I'm not sure of their purpose on Flickr. The joys of having my own server space!
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Old 09-26-06, 06:59 PM   #15
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what's the spacing between the flanges ??
come back in a year and tell us if the axle holds up

(not being sarcastic or anything liek that)
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Old 09-26-06, 07:00 PM   #16
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Is there additional function to this setup, or just for fun? Either way, looks pretty sweet!
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Old 09-26-06, 08:20 PM   #17
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less DIY, more bolt-on action: click
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Old 09-27-06, 12:09 AM   #18
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^^^ Yeah, but Level is the most expensive solution in existence, while disc mount is the cheapest while being equally bombproof. Cog supply is guaranteed as well (if you can drill one...). Of course, you can't go freewheel with this setup, ever, which is the only down side to it that I can think of. Oh well.

It is cheap, light, absolutely indestructible, easy to switch cogs, easy to tweak chainline. I'm not expecting any problems except becoming less and less unique as others discover the joys of 6-bolt. BTW, one guy here in Budapest is already building his to copy mine, redeploying his used MTB front hub...

coelcanth: let me get my caliper... 55 mm. Enough. 9-speed MTB rear wheels have the drive side flange only 18-22 mm from the rim. On this one, it's 27 on one side, 28 on the other.

I did worry a bit about the axle. Was planning to find out how far apart the bearings are on typical rear hubs, but didn't. (If someone knows, tell me.) If you think about it, it has to hold up. In freewheel hubs, the drive-side bearing was on the inside of the freewheel, I'd guess at least 1 or 2cm, maybe more further in than it is on my hub, so the setup is stressing the axle way-way-way less than an 8-spd freewheel hub did. It better do so, cuz 8-spd freewheel hubs cracked axles like salty sticks. I shelled out on a $10 Shimano axle (yeah, that counts as a luxury item for me...) to be on the safe side.

DerekRI: What additional benefit do you want? Costs half as much as a track hub, weighs less (I think) and works better.


BTW, 6-bolt shimano disc hubs are discontinued (they do splined disc mounts now) Grab one while you can

Thx, BM. The pics are a-ok on my comp now without the junk at the end of the URL.
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Old 09-27-06, 12:25 AM   #19
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Oh, yes: it is a 16t. The chain gets pretty close to the bolt heads, so you ceratinly can't drill a 14t. Maybe a 15, depending on what chain you use and how large the bolt heads are.

Also, DX cogs are surprisingly thin. This is something like 2.2 mm, while my track cog was exactly 3mm thick. Maybe it's actually not a 1/8? Dunno.
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Old 09-27-06, 12:43 AM   #20
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Quote:
Originally Posted by LóFarkas
Of course, you can't go freewheel with this setup, ever, which is the only down side to it that I can think of. Oh well.
Instead of using a front hub, get a singlespeed rear hub with splines for one cog on one side and the disc mount on the other. Yay, fixed/free! I have the one from Nashbar. If you don't file off the cog splines entirely you can use the drilled cog on the freewheel side, too.
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Old 09-27-06, 12:50 AM   #21
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^^^ Yeah, thought about that. Only these silly manufacturers only make SS disc hubs in casette style, which makes them heavy as a rock and expensive like frickin' jewelry. Also, no fix/fix possibility. 135 as well, though I could probably chop one down to 130.
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Old 09-27-06, 07:41 AM   #22
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I love it! Very glad that things worked out for you LóFarkas.

As far as stripping discs, I've heard of people stripping the heads of the bolts that hold on discs, but that's about it. It looks to be about as bomb-proof as you can get for $70. Very well done.
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Old 09-27-06, 10:51 AM   #23
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I have a disk front hub I wanted to try this on, only thing is its currently setup for a QR. Mabey I'll change the axle out and try to find a cog to drill. Ohhh if only someone made one besides Boone.
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Old 09-27-06, 10:55 AM   #24
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That's pretty badass! Great job.
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Old 09-27-06, 10:59 AM   #25
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Is that a M756? Same hub I used, which was rediculously easy since it's based on a 10mm axle. Nice job!
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