Looking for a crank arm that is 118mm for single chainring setup

[Ajax Bay]

Nowadays, all square taper BBs are symmetrical, and even this century's cup and cone spindles mostly are.
Each additional 2mm of spindle length (in a BB) moves the cranks 1mm outwards. This is not difficult maths and stop allowing yourself the excuse of "not being maths savvy". But note that what you seek to do (single speed and a change of cranks) is not 'simple' and needs calculation and measurement to avoid buying the wrong item. And while your images are very clear in themselves even your thread title is 'wrong'.
You haven't made it clear where on the freehub your single sprocket is going to fit. See my earlier post - because that seems to offer significant chain line adjustment options, in 5mm intervals though. If you expect to position it where your largest (of 7) sprocket is then you will not match its line with the cranks: that would need a chain line of about 29mm - and the chain stay would prevent a chainring of any sensible size.
Where does this 118mm BB come from? Is that the broken one?

 

[XE007]

Thanks for you reply Ajax. Yes the 118 is from the old one.

I understand I need to get the calculations correct as I want to get the chainline right.

Like the previous poster said, I would like it in the middle as possible. I do understand that I will need spacers on the cassette later on once I get the measurements right.

Yes the title is wrong as much has changed but thanks again for your assistance and thankyou for clarification. No excuse for my math of course but have to think longer than most :-)

If I go your route on pushing the crank out, will I need any kind of spacer.

Thanks ajax

 

[Ajax Bay]

Share a link to how you are setting up your single sprocket on a 7sp freehub, please.
Andel chainset
"JIS square taper axle of length 110mm. A Shimano UN55 or Tange Seiki bottom bracket would be perfect.
"With the correct B the chainline is 42mm"
Every 2mm more than 110mm on the BB spindle will add one mm to the chain line at the crank.
@rogerzilla has given you all this.

 

[XE007]

Guys, thank you so much for your help in this and i now finally get it. I will let you know how this goes and thank you. Sorry for the headline as your questions modified what I originally wanted which is a very good thing.

thx