Counting tyres on a conveyor belt

[L D[AR2P#0.0]]

If the tyres are placed manually - can the tyres end up on top of each other or will they all be flat as in this example.

 

[markymark31]

Yes they will lay flat, exactly how they are shown on the belt in your photo before they get to the roller conveyor.
This is the sketch we made below (worst case) ?

 

[ktmtragic]

Two sensors in series mounted across /above the belt looking down. If they are spaced correctly should be able to pick the space between tires even if they are touching.

 

[rigicon]

Colour sensor? Pity you have dismissed camera's as they start at £600+. It would be an ideal camera taught application with a positive outcome.