I was browsing a Swiss company who make custom titanium frames and I came across I build I liked the look of with Alfine and a belt drive. In the promotional speil translated by google it states, “No eccentric bottom bracket and our new frame lock/dropout”. Looking at the dropout I cannot for the life of me figure out how they’ve done it? I think it must relate to the coupler for the frame for the belt drive but its really clean and non-obvious – at least unless I’m missing something!!!

The site has annoying flash protection so I can’t link direct to the picture nut I screen grabbed and add on here but here is the link to the page: http://www.hilite-bikes.com/titan/en/clean-racer-shimano-alfine-sg-s705-gates-drive-belt/

Thanks to anyone who can shed any light or explain it.

Telescopic chainstay(s) at the split (with grub screw accessed from the dropout) to allow tensioning?

Some Jones frames, or maybe just a prototype, came with telescopic adjustable chainstays that let you adjust chain tension by pulling/compressing the back end.

As both sides of the frame seem to have a split on this model, I’d guess they have done something different, presumably tensioned via an screw that’s accessed from the dropout, into the chainstay?

It’s super neat.

(Like Nemesis said :-))

JINX!

Ha! Brant can’t speak now 🙂

Interesting stuff. Thanks for explaining. So now I have a new consideration for the age old sliding dropouts vs EBB debate. Its been executing really nicely on that model.

Tidy, assuming it works:

Bit delicate perhaps?

Been thinking a bit more about this – if they are telescopic chainstays wouldn’t the seat-stays have to be adjustable as well to account for the change in position? If so I can’t see any joins on the seatstays for this.

wouldn’t the seat-stays have to be adjustable as well to account for the change in position

There’s enough ‘give’ in Ti to take the changes needed.

There’s a fair number of FS designs that rely on repeated stay bending instead of a rear pivot.

Hmm, but given this, wouldn’t moving the dropouts mean you’d have to readjust the brakepads?

I think it’s made for that belt length. The joins at the split are flush and there’s no chain wear to account for so it may only have a few mm of range. Really neat.

The pitch on the belt is what, 5mm? If so, you’d only need ‘2.5mm plus a bit’ of adjustment (assuming you can get belts in specific lengths)

assuming you can get belts in specific lengths

You can, but not a huge choice.

Still don’t get it. It those photos the split is flush but the belt is tight. Never used a belt though – perhaps there’s enough give to persuade/climb the belt onto the drive rather than getting it on and then tensioning.

Tidy looking bike – strange component choice though – uber expensive looking frame with economy deore chainset.

jameso – Member
there’s no chain wear to account for

Quite right – however there is belt wear to account for, unless there’s some mew material that never wears?

perhaps there’s enough give to persuade/climb the belt onto the drive rather than getting it on and then tensioning.

vertical dropout – put belt on ‘cog’ on rear hub then insert hub into dropout. Same as with an EBB?

Possible eccentric in the dropout?

vertical dropout – put belt on ‘cog’ on rear hub then insert hub into dropout.

Ahh, that makes sense.

Quite right – however there is belt wear to account for, unless there’s some mew material that never wears?

Perhaps it’s a bike for looking at not actually riding – therefore no wear 🙂

Could it be the correct chain stay length for that belt? But like the old magic ratios for singlespeed?

that was my thought and the split chainstay is to feed the belt through and not to adjust

Quite right – however there is belt wear to account for, unless there’s some mew material that never wears?

A few mm may be enough if you don’t intend to run it into the ground MTG-style. There’s not the wear rates a SS MTB chain sees anyway.

My first thought was a magic ratio. The split in the chain stay is obviously there together the belt on. There would have to be a smaller tube inside the chain stay to strengthen the join, you couldn’t have two tubes butting together and expect it to stay inline.

I can see the idea mentioned nemesis (and brant) of the adjustable chain stay length via a screw accessed from the drop out, but there would be no access with a wheel and wheel nuts in the dropout.

But to gain enough movement to open the chain stays to get the belt on, keep it strong enough to cope with the load, and to offer belt tensioning, I think the seat stays would need to be bolted and not welded.

Edit: The BB looks suspiciously like an eccentric to me. Not sure, but it does look “normal”.

Interesting to see their solution.

Some stuff here – http://www.hilite-bikes.com/titan/en/successful-compromise-stiffness-weight-comfort-2/

Could there be something funky going on in the BB , as I thought Deore cranks were only available as HT2/Out board bearings and judging from the pic below that BB is neither?

It’s a Shimano pressfit bb.

It’s a Shimano pressfit bb.

Everydays a school day.

What about a small cam shaped insert that rotates slightly around the rear axle and main drop out allowing to tension then nipped up to prevent movement.

they do seem to be claiming that they use some sort of magic dropout to achieve the tension, reading brant’s link.

What about a small cam shaped insert that rotates slightly around the rear axle and main drop out allowing to tension then nipped up to prevent movement.

It looks like there is just about room for it on the closeup pic of the dropout.

White Industries have an eccentric hub, could be using something similar

Yeah that other link is interesting because they refer specifically to the dropout and say (albeit with google translate) “No detailed images can be given ;)” – a bit intriguing really. Might have to trawl through the rest of their site and see if theres nothing else to go on. I wonder if there are any Swiss titanium, single speed experts kicking about….