Does this chain look ok?

[al78]

Whilst cleaning the drivetrain on my hub geared MTB I decided to investigate whether I could wrap the chain around the chainring and sprocket without using the chain tensioner. To my surprise it seemed to work, the result can be seen in the photo. The question is, does the chain tension look ok here and how much should I be able to wiggle the chain up and down? Are there any other issues that I need to consider. I was planning to put a chaincase over it to keep dirt off which should greatly reduce chain wear. As the frame has vertical dropouts I cannot adjust tension by moving the rear axle horizontally.

The chainring is 42T, sprocket 20T and the distance from the centre of the rear axle to the centre of the crank axle is just over 42 cm (42.3 ish).

 

[RecordAceFromNew]

General rule of thumb is half an inch up and down, though unlike fixed a little more relaxed would be fine unless the chain starts to come off.

Although you have vertical dropouts, you might still be able to finesse it by choosing the right "magic gears" with precise measurement of the distance between the bb and the rear axle.

 

[yashicamat]

Looks a little slack to me. The biggest issue, as mentioned by RAFN, is the chain jumping off the sprocket at the back. If you're using normal sprockets designed for multi-speed bikes, they are likely to have shaping on them to make shifting gear easier; this works against you on a SS bike. I solved my issues with two large washers each side of the sprocket - my chain never leaves now and I don't have to have a perfect chain tension either.

 

[Piemaster]

Another option would be to fit a half link in the chain

 

[Zoiders]

You get more leeway than with fixed of course so magic gear is less sensitive to exact tension but I would be looking at an adjustable chain tensioner that you can adjust the chainline on.

 

[Piemaster]

Think the point of the OP was the removal of a chain tensioner.
Actually, looking at the photo again there must be as much chain engaged on the sprocket as there would be if using a chain tensioner so can't see there be anything much more than an asthetic problem. I have some slack on an alfine hubbed bike and its not been a problem.

Way I see it - With a hub gear os s/s the chain wraps a full 180 deg around the sprocket. With a chain tensioner or derailler it is less than that but there is the tensioner involved.