Xsalor,
some motors have capisitior start, and they will not run under low voltage conditions without the capisitor trying to kick in and get the motor back to full speed... and it kicks in if you load up the motor under work,
i think its a general rule of thumb, unless the motor has replaceable brushes it wont work,,
easy to find out, if your willing to give it a smoke test.
turn it on and plug it into one of the foot controls on a sewing machiene,
but mash the foot control to the floor and slowly back off when testing,
it should provide full power, then back off the foot switch, if it starts bucking quit.
my harbor freight 1" belt sander wont run slower than full out. its low amperage 1/4 hp motor has capisitor start for starting and kicking
some cases motors have exterior caps that can be removed to get at the brushes, but there is a lot of different motor syles that have hidden brushed, some are brush less... hard to tell looking at them
look on the delta web site for the sander and see if they have the exploded diagram on that sander, or any information on variable speed... control
i have the 1x42 craftsman and 1x30 harbor freight 1"x30 sander and
www.leevalley.com has the belts regular abrasives and leather, im thinking of that leather belt myself but at 1150 rpm i think it will just sling off the compound
or just going ahead and building a mandrel like the Burke system, its just hard for an non driving feller to get around to all the different places to get all the parts... or i would definitely have one.
all the small sanders grinders and stuff round here that i purchased are mom and pop weekend toys,, and they are tearing up on there own, lost a 1x30 belt sander due to a faulty switch burning out. the battery operated dremels
and last night my wet grinder ate the worm gear... of course not brass but plastic,,, made to be ate if there was trouble, now finding that part in Taiwan or china will be fun...