Originally Posted by corgi1
Flat bar w/a slot mounted between both tubes ,,,a tube that fits the idler size bolt ,cut at a slight angle(like the angle of the mounted flat bar compaired to the chain),,,a handful of washers for spacing and the ends of the tubes,,,the angle cut tube would turn around to the chain line and washers would give in/out adjustment and the nut on the bolt would be straight beacause of the other end of the angle cut tube
Yup, you got it! It's clear as mud.
The chain run is not in line with the seat and chain stays because the stays are attached to the seat post (narrow end) and wide at the rear so the wheel can fit in between them.
They are at an angle to do this. The engine chain run is straight, in line between the rear sprocket and engine sprocket, not the same angle as the chain stays. When you attach the mounting plate to the chain stays it will be at the same angle as the chain stays, not the angle of the drive chain. When you directly attach the idler wheel to the plate it will be at the angle of the chain stays too, not straight and true with the drive chain.
The tube cut at a slight angle fits in between the mounting plate and idler wheel and you can rotate the tube to get the idler wheel to rest in line and true to the drive chain. The handful of washers are provided to allow you to adjust the idler wheel in or out so the chain is centered in the idler wheel's groove.
You stack them as needed on to to the assembled length of the idler wheel and angled tube to center the chain in the idler wheel groove when everything is tightened.
I hope the mud is clearer now.