# Rohloff Belt Drive



## smudge (Jan 12, 2004)

I built this bike for myself to enter in a competition back in October. At that time, I had been waiting for rohloff compatible CarbonDrive cogs for nearly two years and had pretty much given up. I discovered that Phil Wood Co is making Rohloff compatible cogs and finally got the bike set up as was originally intended in late November.










I had been using this rear wheel on my 29er for the past few years and always hated it for MTB riding. It turns out it's a perfect commuter wheel and I'm glad I didn't sell it as I had intended.










We've been lucky enough to get some great weather here in the PNW over the past few weeks. Coupled with the fact that my daughter is now finally strong enough to wear a helmet, I've been able to get out for more frequent rides than normal. Bottom line, I dig the belt drive.

The Phil cog doesn't have hollow teeth and I don't imagine it would be great for the mud but in my case it makes for a great around-town bike.


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## Ptor (Jan 29, 2004)

That is a gorgeous bike -- very clean and efficient looking. The front rack is great -- how heavy a load are you good for? I have two additional questions -- what is the front end geometry (HTA and fork offset)? And second, what the crank is and how do you set it up to achieve the correct belt-line? I'm always looking for a better crank setup for my Rohloff.


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## smudge (Jan 12, 2004)

PeT said:


> That is a gorgeous bike -- very clean and efficient looking. The front rack is great -- how heavy a load are you good for? I have two additional questions -- what is the front end geometry (HTA and fork offset)? And second, what the crank is and how do you set it up to achieve the correct belt-line? I'm always looking for a better crank setup for my Rohloff.


Thanks.

I've put about 20lb on the rack so far and it was fine. I don't know how much I can put on it yet but I suspect I'll find out in the coming months. The platform isn't very big, 10 x 14, and fits my Timbuk2 Dee Dog messenger bag perfectly. It's 3/8" x 0.020" wall titanium and in hindsight I should have put a couple of struts at the top of the fork rather than one crown bolt (it was my first rack and first fork). If I grab the rack with my hand, I can wiggle it significantly but in use I don't notice anything bad. I wouldn't let anyone sit on it though.

The HTA is 73.3° and the fork offset unintentionally came out to 47mm. I'll eventually get around to building a new fork for it, it was supposed to be 55mm. I made a super quick mitering fixture and used a horizontal mill at a friends shop (I couldn't make it work with my fixed head vertical mill). He was hard at work so I set it up quickly, ran the miter and then took off. It rides great with no load but the front end gets a little heavy with ten pounds on it.

That's a Dura Ace double crank and the only way to get the belt line right is to use a ton of chainring spacers. It's no good but it's what I had. I have a prototype FSA BB30 triple crank that I'm eventually going to use but I have to make an eccentric insert that will accommodate BB30 bearings. It's modeled up already, I just have to plan the machine setups. I'll still need some chainring spacers, but not nearly as much.


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## Ptor (Jan 29, 2004)

smudge said:


> I have a prototype FSA BB30 triple crank that I'm eventually going to use but I have to make an eccentric insert that will accommodate BB30 bearings. It's modeled up already, I just have to plan the machine setups. I'll still need some chainring spacers, but not nearly as much.


Oh, to have skills like that... I have a Ti frame with an eccentric that I run my Rohloff on and I've had issues with the Bushnell and Carver eccentric binding the bearings of the bottom bracket when things get tightened down. Do you think your eccentric insert will help with that? If your eccentric for the BB30 works out, it would be great if you were able to offer them to the general public. I also like to run narrow Q-factor crank, hence my interest in your crank -- might have to look at using a bunch of chainring spacers myself -- what is "not good" about that solution?


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## smudge (Jan 12, 2004)

PeT said:


> Oh, to have skills like that... I have a Ti frame with an eccentric that I run my Rohloff on and I've had issues with the Bushnell and Carver eccentric binding the bearings of the bottom bracket when things get tightened down. Do you think your eccentric insert will help with that? If your eccentric for the BB30 works out, it would be great if you were able to offer them to the general public. I also like to run narrow Q-factor crank, hence my interest in your crank -- might have to look at using a bunch of chainring spacers myself -- what is "not good" about that solution?


I'm not sure why the Bushnell would bind as the part that contains the threads is one solid piece. There should be no misalignment in the bearings, which is often the cause of the binding. What type of BB are you using?

The way my insert works, it's dependent on the ID and the faces of the shell being machined properly. Because of that, it's unlikely that I'll offer it for sale without one of my frames. As of right now, I don't think there's a single frame builder (including me) who has a tool that can reliably face a 2 3/8" shell and I only know of very few who bother to bore the shells after welding. My insert will use a larger than standard bore, which is another reason why I have no current plans to offer it aftermarket.

It's not that using a bunch of chainring spacers doesn't work, it does. It's just a pet peeve of mine to have extraneous stuff on the bike. The tech drawings I got from Carbon Drive listed a chainring offset for 130mm cranks that was incorrect, hence the spacers. Had I known from the get go, I would have opted for MTN cranks rather than the DA cranks I have.


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## NHpug (Mar 30, 2007)

Would you please say more about where and how the frame separates for the belt?
Lovely bike!
Thanks!


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## smudge (Jan 12, 2004)

NHpug said:


> Would you please say more about where and how the frame separates for the belt?
> Lovely bike!
> Thanks!


It's something I first saw on a bike designed by Dave Levy of TiCycles. You can see a line around the circumference of the seat stay just above the dropout. There's a cone inserted into a negative to take the shear load and a bolt that's holding it all together. The bolt is inserted under the hood of the dropout. If you didn't already know it was there, you probably wouldn't look for it.


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## NHpug (Mar 30, 2007)

Cool, thanks!


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## smudge (Jan 12, 2004)

no problem. detailed pics here


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## Wombat (Jan 25, 2004)

That's a lovely bike. Sometimes they just look right and, although this is always subjective, yours looks great. And I like the solution you have for the getting the belt through the chainstay.

Tim


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## Ptor (Jan 29, 2004)

smudge said:


> I'm not sure why the Bushnell would bind as the part that contains the threads is one solid piece.


I would not have thought a Bushnell would bind either, but it can easily be demonstrated -- when the EBB is cranked down to the point where it won't slip, the number of "swings" that a single crankarm can make when let go from the horizontal position (no chain mounted, arm swinging like a pendulum) is halved from when the EBB is loose. This is true with Phil Wood Ti or Shimano UN52 or UN72 bottom brackets. I mate those bottom brackets to a set of Ritchey Logic Mnt cranks as it gives the lowest Q-factor for a crank that I have come across.


smudge said:


> It's not that using a bunch of chainring spacers doesn't work, it does. It's just a pet peeve of mine to have extraneous stuff on the bike.


If it's not too much trouble, perhaps you could post a picture of the spaced out chainring. I've thought about doing something like that to reduce Q-factor even more (my frame can handle it). Also moving to an external bottom bracket might solve my "bearing binding" problem.


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## smudge (Jan 12, 2004)

PeT said:


> I would not have thought a Bushnell would bind either, but it can easily be demonstrated -- when the EBB is cranked down to the point where it won't slip, the number of "swings" that a single crankarm can make when let go from the horizontal position (no chain mounted, arm swinging like a pendulum) is halved from when the EBB is loose. This is true with Phil Wood Ti or Shimano UN52 or UN72 bottom brackets. I mate those bottom brackets to a set of Ritchey Logic Mnt cranks as it gives the lowest Q-factor for a crank that I have come across.


That's really interesting. I'll have to look more closely at it while I ponder it. Obviously you're seeing something that I either haven't experienced or maybe it hasn't affected me enough to notice. It would be nice to understand why that's happening. You're using a cartridge bottom bracket as well, which would seem to make it even less likely to happen.



PeT said:


> If it's not too much trouble, perhaps you could post a picture of the spaced out chainring. I've thought about doing something like that to reduce Q-factor even more (my frame can handle it). Also moving to an external bottom bracket might solve my "bearing binding" problem.


Sorry for the huge pic but it's already up on flickr. You can see the spacers if you look here. I think these add up to 5mm and right now I have 8mm of spacers between the ring and crank.


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## windsong (Feb 21, 2010)

*belt diven on the spot*

We at the bike shop are looking to upgrade our belt diven spot to increase the climbing beneifits and enjoyment, can it be done? :band:


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## UncleRobin (Dec 28, 2009)

smudge said:



> Sorry for the huge pic but it's already up on flickr. You can see the spacers if you look here. I think these add up to 5mm and right now I have 8mm of spacers between the ring and crank.


Instead of the chain ring spacers, could one flip the ring around so the mounting tabs were on the inside face of the ring? Also the choice to mount the ring on the inside or outside of the spider would add to the chain line adjustment possibilities. Just curious.


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## smudge (Jan 12, 2004)

UncleRobin said:


> Instead of the chain ring spacers, could one flip the ring around so the mounting tabs were on the inside face of the ring? Also the choice to mount the ring on the inside or outside of the spider would add to the chain line adjustment possibilities. Just curious.


If the ring is flipped and run in the outer position, it interferes with the crank arm. If flipped and run in the inner position, it sits too far to the inside.


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## smudge (Jan 12, 2004)

windsong said:


> We at the bike shop are looking to upgrade our belt diven spot to increase the climbing beneifits and enjoyment, can it be done? :band:


See if you can find an aftermarket Adam Craig quadriceps bolt-on kit, that should take care of the climbing benefits. I'm not sure what would help with enjoyment...the promise of post-ride cold beverages?


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## Speedub.Nate (Dec 31, 2003)

https://www.cyclingweekly.co.uk/news/latest/444118/james-bowthorpe-s-round-the-world-bike.html

Here's a bit of an interesting read -- from the UK's _Cycling Weekly_, this rider recently completed a 176-day round-the-world ride on a belt-driven Speedhub.


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