Pinnacle Posse

Arkose/Dolomite eccentric bottom brackets, anything i need to be wary of if buying a used frame (do they go wrong, creak etc)?

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They're a simple clamp shell on a solid insert so they're fine as long as the inside BB face is smooth and even.
Check the bolt threads are good. Bolts are supposed to be at 10Nm so check that and ride it with some caution in case it slips (you don't know the bike's history etc), all should be ok. If there's any noise that isn't the crank-BB or crank-pedal check the inside of the shell for uneven contact marking, eg light fretting type marks that might show a distorted shell. The frames were good generally so you're just checking for one that might have been poorly QC'd, it happens. You can put more than 10Nm on those bolts but they shouldn't need it.
Good bikes (I'm biased, I know) I loved my Arkose SS on Nano 40s, wish I'd kept hold of it.

Thanks that super helpful, am i right in thinking these can be run fixed if i flip the wheel and put a cog on the disc mounts?

I don't see why not. Check the dropout and hanger, there was a batch of the dropout used on the old Arkoses around the time of the SS models where the small bolts that hold the hanger in sometimes protruded a fraction above the frame side or hanger side surface and it could reduce the QR/skewer surface contact and grip. Not an issue normally but if you were putting tension on the lower chain run to brake the axle slot is at a forward/downward kind of angle and you don't want to pull the axle out of the driveside slot. Just fwiw. Check that and put a bolted axle/skewer on.

All makes sense, thanks again. TBH it looks like it could be a lot of fun/more useful as a single speed so i'm going to give that a proper try first if this pans out.

@jameso don't suppose you have a handy guide on how to adjust the EBB?!

I've loosened off the two M6 bolts and removed the cable guide for good measure. Initially i did a full assemble thinking i'd push on the cranks to rotate them but they weren't budging. The only way i can get the EBB insert to rotate in the frame is to put a BB tool on the external bearing shell and crank it. That moves things (feels/sounds a little coarse) but obviously is not feasible to do with the cranks on.

Do you know if the insert can drift from DS to NDS and vice versa? Want to be sure as i'm cranking on this thing that i don't mess the chainline up.

UPDATE/EDIT... Just found the two holes on the NDS, are these for a pin spanner? Bit surprised if this'll do it but then the stiffness may be the fact that it had drifted over and i was likely binding the BB shell on the frame!

I’m selling my size small Arkose singlespeed. Don’t suppose anyone has a medium they’d like to swap with me?

Sorry, late reply from infrequent visitor.
Prob a bit late now : )
Tip for moving this type of EBB insert more easily - take the pinch bolts out and thread one/both in from the other side with a penny in the slot. Tighten a bit and the bolts will push against the penny and it'll help you gently open the shell up so it all rotates more freely.
The insert can move side to side a little yes. The 2 holes fit an old pin spanner type I think but it's a while since I've seen one so I'm not sure.