|Glossary Intro and Glossary Annexes|
This narrows the groove of the upper belt taking up the slack created by raising the assembly. It is beautiful in its simplicity but difficult to describe. When the machines set unused for years it is common for the center floating portion of the assembly to stick from rust or dried grease.
Without knowing how the mechanism works this creates real problems for new owners. If you crank the adjuster too hard the aluminum supports for the adjuster rod will break off. Sadly, I have seen way too many in that condition and have repaired a bunch of them.
The speed changer has two operating ranges depending on how you orient the belts. Low range gives rpm from around 450 to 1800. High range from around 2000 to 6600 rpm.
One disadvantage is that most lathe and drill press work are in the low range and the table saw operates in the high range so belt changing is necessary when changing modes.
A second disadvantage is that the two belt system creates a lot of power loss between the motor and spindle.
When you start with 1/2 HP that doesn't leave a lot. It still works pretty good for most lathe and drill press work but really can be a problem in saw mode.
Many users will remove the speed changer pulley and go to direct drive for table saw use. Sadly, this requires reversing the motor pulley orientation also so if you do it often it can be a real pain.
That is why variable speed dc or ac motors are really nice to have. They make the machine the best of both worlds.
Since the table saw is also the most compromised function of the multipurpose machine, the ideal shop in my opinion will have a nice table saw to complement the 10ER, space permitting of course.
[Below is a cut=away of the speed changing mechanism used on Mark IV and later models of Shopsmith. In addition, notice on the upper right portion of the image a cutaway of the "quill and lever" setup.]