For the tensioner I'm going to use a small hydraulic ram with gauge and screw type piston, similar to the kind found on a set of hydraulic pullers.
For height adjustment I'm going to use new acme rods and nuts linked across with bycicle chain and sprokets.
The saw main frame will be of aluminium, because you can buy it in sizes that will slide inside each other more acurately than steel, I have acsess to a tig welder to weld things up here.
For powering the belt to the band wheel, I'm going to buy one of those industrial centrifugal clutches, that fits straight onto the engine shaft.
For log leveller, I'm going to make a wide V bracket/plate, welded onto the top of a large commercial scissor jack.
For log dogs, a set of expanding jaws closed by another acme thread, fastened to the maim chassis cross member under the log, use acme thread and nut and geared head from scissor jack, make sure of depth of cut, so you do not cut through with band.
For a log turner, use a hand wynch welded to a plate on top of a 2 inch box section, which slots into another box welded to the main chassis, the nylon strap type, place strap under log and around to the other side of the log, knock in a peg, turn wynch and the strap will turn log around and over.
Lets call this the crap heap challenge, to see who can make the cheapest mill here.
Davy.