Building the printer rails BELT ISSUES COMING OFF!!

Well I staying up late last night, again. I built all three sides of the printer rails. Bottom motor mount, belt spreader pulley and upper end pulley.

I connected the belt to the carriage.

End pulley connected

Motor end and belt spreader

MOTION UP AND DOWN WAS SMOOTH - BUT BELTS FALLING OFF THE END PULLEY - UPON MOVING THE CARRIAGE UP AND DOWN - TWO TURNS OF THE END PULLEY!!

ON ALL THREE SIDE ASSEMBLIES!!

I tried flipping the motor gear  - SAME thing - keeps coming off the end pulley at top.....

I then read  - http://reprap.org/wiki/Rostock#Belts

Belts

It can be challenging to get good belt tension. You should be able to pluck nice bass tones on the belts. Here is Johann's tensioning method:

• Make sure you don't have a flange on the outer idler bearing (the one that is facing you).
• Put timing belt on motor pulley and idler bearings.
• Push idler end up as far as possible with one hand.
• Remove belt from idler bearings.
• Push idler end up 3 mm more and tighten screws on smooth rod.
• Put timing belt on idler again. It will be very tight.
• The idler bearings are tilted 2 degrees upwards, so your belt should not fall off even though the outer bearing has no flange.
• If the belt does fall off, reduce belt tension slightly, or print a new idler end with increased upward tilt...

Important note - last two statements - 

• The idler bearings are tilted 2 degrees upwards, so your belt should not fall off even though the outer bearing has no flange.
• If the belt does fall off, reduce belt tension slightly, or print a new idler end with increased upward tilt.

I did not know there was a slight angle - also noticed the screw holes where the endstop will mount - I INSTALLED ALL THREE END PULLEYS UPSIDE DOWN!!!! HAHAHAHAHAHHAAA!!

Flipped them 180 degrees AND WORKS LIKE A CHARM - belts not coming off!!!