2009:Mechanical 2.28.2009

Summary from 2-26-09

Set out to prove out the add on helix idea for the shaft rollers.  Used a PVC roller and set it up with 2 round belts with helix winds on both sides of the belts.  Used our wooden mock up with a std plucker pulley shaft on the bottom.  The concept worked great, it could feed balls up and feed them out the top.  We used a stationary piece of wood board for the rear section.  The helix sections would reseat a belt that is pushed out of the desired tracking groove.  There is a short video that Cynette took and it is placed on the conveyer redesign comments link near the 2-16-09 work sheet day log.

Started fab on 1/2" diameter shaft lengths and 1 1/2" diameter tube lengths.  Also started cutting the nylon end plug bushings.  Gathered up 1/2" shaft collars in case we need them.  Goal would be to make 5 sets of these roller shafts.  Should also make a spare as well. 

Got agreement on the revised belt layout:

Front lower(plucker to second level) will be 4 belts.  From second level to top will be 9 long belts spanning the ~24" distance.  The third level will be an idler.  The layout will be - a lower drive belt then 3 belts going up, then 2nd lower drive belt and 3 more going up, the 3rd lower drive belt and 3 more going up and the 4th final lower drive belt.  Spacing to be determined.

Spent time recalculating belt lengths to reduce the bearing loads and motor torque.  Looking at 5 to 7% stretch.

Summary from Saturday 2-28-09

Still concerned about bearing loads on shafts that have 9 belts.  Did a little bench mock up with nine matched belts and recorded force to stretch 1%, 2%, etc.  It took more than 140 pounds to stretch 9 belts 2 %.  Decided at that point we would shoot for 1 to 1.5% max.

Finished up making all the shaft roller components for 5 sets of shafts.  Also cut and finished an extra inner and outer shaft and roller.  Still need another set (2) of the nylon bushings.  All 1/2" shafts have been polished down on the ends for a slip fit with the bearings.  Experimented with various concepts and belt spacings to get all the helix features on the roller.  Late in the day we decided to use dounut rings out of plucker tubes (joined together with short sections of 10-32 screw threads) in some locations instead of helix to save space on the shaft so we can still have 9 belts across.

Recalculated belt sizes for the nine wide conveyors using 1.4% stretch.  This will allow us to reuse the 4 upper rear belts currently on the robot.  Reallocated belting material, looks like only one belt will not be continuous (made from two pieces).

Josh was in with Nick and (others) and they mounted a robot sub frame to the cart and did other finished work on the cart.  Added a piece of plexi to the under shelf - that will make it safer to carry batteries just in case the tape would get scrapped off both terminals and they happen to hit the shelf at the same time - no risk of that now.  It looks awesome, great job cart team! 

Started packing for RIT - Lots to do still, we will meet on Sunday from Noon till 5:00pm