For a scatterbrained idea.

Shimano Alfine. No other one single speed tensioner comes close imo. Apart from the obvious £50+ ones, the Shimano one is like £12

I liked the Surly Singleator. Spendy but justified because it gives both push up and push down options. That may not be important to you.

But it requires a thin 18mm cone spanner to adjust. I fashioned one from a small oddment of metal plate to keep on a keyring so I didn’t have to carry a larger spanner

I’ve had problems with push up fouling the chainstay before taking out enough slack.

Does the Alfine guide allow you to remove the rear wheel as you would with a mech or does it not have sufficient range in the spring so you need to loosen it off first?

Also looking at harebrained idea.

Alfine tensioner has an odd chainline if I remember correct though I had no issue using 3 different brand tensioners with my alfine

The first segment of the Alfine is fixed, which means with large cogs you will probably need to undo the bolt first.

Meh, in which case no worky as I need to lift the rear wheel out to get the bike in the car.

Ah, that reminds me there are two alfine tensioners

the one above and this one

Why push up?

I got hung up on the idea of it being the correct engineering solution, but as the podge pointed out, they only work if your chain is the right length + half a link or so.

Which is probably why the alfine has an extra arm in it.

Push up because I think it’s a better way to do it than push down, and it needs to be sprung because I’m going to try it on a FS frame that doesn’t have a BB pivot, although the main pivot is just behind the BB shell.

You might need a push down tensioner then, perhaps. Push up usually requires a shorter chain length, which may not be long enough to accommodate the rear sus movement.

One of those Alfine ones that looks like a rear mech might be best.

Seems such a shame on a lovely minimal-looking singlespeed to bolt one of those awful things on the back. They look pretty much like a mech, only worse…

Why not use a bottom guide wheel on the front such as a Blackspire Stinger?
I did this on my old 24″ DMR and also on my current 26″ DMR singlespeed.

Providing you have an open chainring, you can twist the guide upwards to tension the chain, then nip up the allen bolts through the chainring.
If you don’t have ISCG mounts you could still use a BB-mounted guide but it would take a bit more trial and error to get the position of the arm right before pushing the guide wheel into position and locking it.

Handy to have that added chain-retention too.

My old 24″ jump bike.

Edit – Just noticed this…

it needs to be sprung because I’m going to try it on a FS frame that doesn’t have a BB pivot

Works well on a hardtail though.

You’ll need something like the Rohloff tensioner or that first alfine up there then, a normal singulator style one won’t offer anywhere near enough range on a suspension bike. Bear in mind the tenioner has to adjust for double the chain growth.

If you can get a hold of one, goldtech (BETD) used to make a sprung chain device.

kayla1 – Push up because I think it’s a better way to do it than push down, and it needs to be sprung because I’m going to try it on a FS frame that doesn’t have a BB pivot, although the main pivot is just behind the BB shell.

I ran a Giant trance with an Alfine using a superstar Zinger without problems.

Had previously tried push up, push down, cheap & expensive. The Zinger was the only one that worked.

I’d agree that on a hardtail the front tensioner is best

Kayak- I use a Blackspire on my HT for just that reason!

TINAS- thanks, I’ll have a look at the rear mech looking ones.