Have you ever seen a belt drive sturmey archer 3 speed hub

[Gattopardo]

Have seen a bike for sale with a sturmey archer 3 speed hub with belt drive.

Are they rare?  Worth anything or more just silly.

[GavinC]

I imagine it would just be a bog standard Sturmey hub fitted with a belt drive sprocket. That was the case with the Sturmey 2 speed coaster hub that was fitted to my Moulton TSR2. The belt drive sprocket was a regular Sturmey fitting - I ended up building a wheel with a 5 speed SA hub and using that with the belt drive.

[Gattopardo]

Ah so no real value over the norm then.

Are the cogs easy to get replacements, if you want to alter the ratios.

[Captain Nemo]

Don't expect to get any change from £100 for a rear sprocket. And then if you want to run the same belt, you would probably need to change the front ring too. Alternatively a new belt or a fugly belt tensioner will be required.

It all starts to get expensive if you want to play with ratios.

[Gattopardo]

Wow, that means the bike really isn't worth anything

[mzjo]

Sprockets have been available for belt drives for a very long time. Since Nexus and Alfine sprockets are interchangeable with SA (I'm assuming that Alfine 11 are the same as Alfine 8, the 8sp ones definitely are) it may be worth looking at prices for them as well if SA cost an arm, a leg and the skin off your butt.

I last looked at belt drive a very long time ago and in that historic era Gates advised against belt tensioners in any shape or form (more exactly they forbid them and any mention of them), the technology may have changed since.

I think the deal might have been change belt, change sprocket (soft alloy probably).

What's the bike?

[MikeFromLFE]

It's one of those interesting technologies that have no great value over the old ways of doing things.
Getting rid of a dirty oily chain brings issues of maintaining tension.
Any other advantages?

[Lightning Phil]

In the days of horizontal drop outs and nuts, tensioning wouldn’t have been a problem or would it?

[DuncanM]

Maybe not, but somehow you need to be able to get the belt through the rear triangle...

[mzjo]

It's one of those interesting technologies that have no great value over the old ways of doing things.
Getting rid of a dirty oily chain brings issues of maintaining tension.
Any other advantages?

On a bike being used in dirty offroad antics there is an advantage in being to hose it all down at the end of the w-e before riding to work on a monday morning. Santana's race team used to do this apparently with their mtbs (or so their publicity said at the time). IGH helps of course, not likely to be very successful as a technique with a dérailleur.

In the days of horizontal drop outs and nuts, tensioning wouldn’t have been a problem or would it?

Gates were very particular about tensioning, chainline and wheel alignment. They had a tension test for refitting on the road a bit like the test used by car mechanics for checking tension on toothed cam belts. Apparently it was a source of belt failure for early Gates installations. Long fork-ends are less use than an eccentric BB shell given the hassle and need for getting back right if you have a puncture. Again the technology may have improved significantly since I read up anything on the subject.

Maybe not, but somehow you need to be able to get the belt through the rear triangle...

Fittings that allow a separation of the rh seat stay have been around for a while to convert bikes to belt drive. Cue your friendly frame builder. Probably the least problematic bit of the whole affair! (Alternatively old mtbs and other frames that didn't pass the chain through the rear triangle)

[DuncanM]

Maybe not, but somehow you need to be able to get the belt through the rear triangle...

Fittings that allow a separation of the rh seat stay have been around for a while to convert bikes to belt drive. Cue your friendly frame builder. Probably the least problematic bit of the whole affair! (Alternatively old mtbs and other frames that didn't pass the chain through the rear triangle)

I am aware - I was responding to the previous post about how you could just use an older bike with slotted dropouts. Rather than getting a framebuilder sort out the stay so it can be taken apart and put back together, you're better off just getting something purpose built. Is the old school E-Stay stuff stiff enough to maintain tension in a belt? I remember them being either flexi or snappy!

[Gattopardo]

Doesn't matter as I'm not buying the bike.