Thread: Turret spindle thingy project

Originally Posted by Stustoys

Yes
I certainly like that idea better, as long as the belts dont flop around to much.

Keep up the good work

Stuart

I was thinking the same/similar Stuart...long distance between drive pulley and driven pulley coupled with no real support at or under mounting area of spindle could lead to lots of vibration as well as belt slap which may compound the... err my ....vibration theory???

but running under load will prove it one way or another

Originally Posted by eskimo

I was thinking the same/similar Stuart...long distance between drive pulley and driven pulley coupled with no real support at or under mounting area of spindle could lead to lots of vibration as well as belt slap which may compound the... err my ....vibration theory???

but running under load will prove it one way or another

It's currently got 2cm of belt flap with a regular time period of about 2 seconds, the pulleys have a reduction ratio of 1:1.1666666 so I wonder if the slight ratio difference gives it a harmonic like that. The reason is that years ago I built a 1Hp disc sander with a 2:1 pulley ratio and a very long belt as the motor was at floor level and the disc at waist height. A friend with some experience in making them said I'd have trouble with belt flap and said he had to use a rigid backed "Pump" belt to stop his from flinging off when stopping. Anyway my sander had no hint of critical speed flap on startup or much running vibration at all , it just sat there quietly with the disc hissing from the airflow. My friend muttered something about me being arsey but I can't help but think the 1440 rpm motor and two different sized pulleys really helped prevent vibration and eliminate the critical speed belt flap.

I would think that having the belts at 90 degrees to the mount would increase movement at the spindle and hence give vibration which in turns compounds the belt slap and one assists the other gradually increasing to its limit

even small irregularities in the V belt..hard/soft spots on the belt (usually on the cheaper belts) can result in increased vibration and once it starts other things can compound the effect.

Going to A section or B section may not be the answer...going to SPZ and keeping the distance short between driven and drive pulley can help reduce vibration..only problem with SPZ's/SPA's are that they like to be very tight so mounts but be rigid...or vibration will once again set in???

Originally Posted by eskimo

I would think that having the belts at 90 degrees to the mount would increase movement at the spindle and hence give vibration which in turns compounds the belt slap and one assists the other gradually increasing to its limit

I'm hoping to avoid that with a 90 degree mount by using spring dampening/tension to begin with and maybe later with a gas strut to provide tension but allow some slight movement for belt unevenness. One option that might work best to release the belt tension would be an over centre brace to give a rigid locking action.

Originally Posted by eskimo

Going to A section or B section may not be the answer...going to SPZ and keeping the distance short between driven and drive pulley can help reduce vibration..only problem with SPZ's/SPA's are that they like to be very tight so mounts but be rigid...or vibration will once again set in???

That reminds me, on the smooth running disc sander, the motor mount was rigid, it was hinged with a threaded rod to adjust belt tension. Even so I've seen a spindle with a rigid motor mount that only has a 24 inch A section that continuously flaps on the driven half of the belt not the returning/retreating half. The whole thing is rigid and solid yet the short belt flaps like a guitar string.

Originally Posted by Graziano

I'm hoping to avoid that with a 90 degree mount by using spring dampening/tension to begin with and maybe later with a gas strut to provide tension but allow some slight movement for belt unevenness. One option that might work best to release the belt tension would be an over centre brace to give a rigid locking action.

Hi Mark,
I have always has belt flap with multiple belts, first one and then the other belt, sort of copying each other. Never real bad though. I had always thought that a rigid mount was better than a sprung mount in regards to belt flap. I have found with sprung mounts the torque of the motor always moves the mount on startup, which can throw belts off. With the belts flapping, the spring can allow the motor to move and cause more flap, etc etc.

Ewan

Originally Posted by Graziano

I'm hoping to avoid that with a 90 degree mount by using spring dampening/tension to begin with and maybe later with a gas strut to provide tension but allow some slight movement for belt unevenness. One option that might work best to release the belt tension would be an over centre brace to give a rigid locking action.



That reminds me, on the smooth running disc sander, the motor mount was rigid, it was hinged with a threaded rod to adjust belt tension. Even so I've seen a spindle with a rigid motor mount that only has a 24 inch A section that continuously flaps on the driven half of the belt not the returning/retreating half. The whole thing is rigid and solid yet the short belt flaps like a guitar string.

short belts are or can be a problem ...as I said above going to SPZ/SPA's commonly called wedge section (they have a deeper V than equivalent counterpart) may (if mounting does not flex) overcome flap, but they need to be very tight..and I mean tight, whereas if you tightened a standard A section to same it would be too tight and belt will prematurely fail.

Originally Posted by eskimo

short belts are or can be a problem ...as I said above going to SPZ/SPA's commonly called wedge section (they have a deeper V than equivalent counterpart) may (if mounting does not flex) overcome flap, but they need to be very tight..and I mean tight, whereas if you tightened a standard A section to same it would be too tight and belt will prematurely fail.

Thanks I'll switch to the SPZ's after the other measures have been tried. At this point the belt flap is what I'd consider acceptable with the motor rigidly wedged but I want to switch to the hinged motor to make the pulley alignment more accurate and rigid than the slide setup currently has.

Not too much work has been done on the Spurret lately, I did fit a gas strut from a photocopier document feeder lid to keep up the belt tension (slight blurred top belt in picture): it was very effective at reducing belt flap and vibrations but the stroke could be longer. I showed it to a guy with more experience in these matters and he replied "Jesus &*$"£! $"*&%!! just how smooth do you want this thing to run??". The strut made the sliding motor mount practical to use as it dampened a lot of the vibrations while still allowing the belt tension to be loosened off for a spindle change. I do plan however to make the motor fit a couple of hinged arms as it would make the pulley alignment much more accurate and could allow a hinged brace for the spindle arm...possibly