Hood side
Hood inside
At the time the readily available sandpaper was paper backed 11x9
I had a woodworker with a lathe turn a 9 inch circumference x 11 inch long drum from Hard Maple fixed to a 1/2 inch steel rod.
The paper was attached using Weldwood contact cement.
The original motor was a 1700 RPM 1/3 HP open Westinghouse.
The original design was a closed box of 3/4" plywood with only the hinged table gap providing the only ventilation.
There is a large piano hinge about 1/3 in from the back edge of the table.
Angle Aluminum was fixed to all four sides of the table.
Two medium duty pillow blocks with a 1/2" shaft collar on the axil.
The axil pulley is 6". The motor pulley is 4.5". The drum rotates more slowly than 1700 RPM but with more torque.
Less heat from friction and more power.
The gap adjustment is a threaded rod. A cap nut at the top meets a wide washer glued to the bottom of the table
A nut is welded to the top side of a steel corner brace. A wing nut locks the height, a dial wheel at the bottom end.
I tried to route a "V" channel in the drum for wedge clamps to hold the sandpaper . I could not pull it off. It did provide a place for the leading edge of the paper that did not have it hit the stock being sanded. This stopped the tear away.
The volume of fine sawdust produced is huge. Collection at the source is a necessity.
A frame of 3/8"x1/2" Pine sticks with walls made of three layers of Amazon corrugated box cardboard. The layers are bonded using a liberal and total layer of PVA glue. The outside is covered with Duct tape. 3/8"x1/2" sticks glued to the inside of the top are the anchor for the screws holding the vac hose socket. The vac hose is heavy. The dust collector box is not. The hose weight has to be neutralized. Bungee cords work.
Mistakes:
the closed box - the motor needs serious air flow. I build POF. A large ship can need 100 or more 2" x 24" boards of framing stock. A long session would lead to a hot motor. It would trip the thermal protector switch.
A capacitor motor - A sander does not need instant rated RPM. Taking a few seconds to get up to speed is not a problem. Having an expensive component that is something else to go bad is unnecessary.
The gap. A stock thickness capacity of slightly more than 2" would be helpful.
Weldwood contact cement - it does hold the paper and the now cloth backed sanding media. There is no solvent that will dissolve it that I can find. I probably would not want to get near it if there is a solvent. Mineral spirits will break the bond, It is a long hard job to remove the now sticky glue - physical scraping.
I recently found a latex cement that easily cleans with most organic solvents.
I still use this sander, It holds 80 grit. It does the bulk of the work to remove the bandsaw blade scaring. Multiple passes.
I burned out the original motor - 40 years was good service considering how I mistreated it.
New motor
1/2 HP 1,725 RPM frame 56
115V AC 8.0 A TEFC
shaft 5/8 in x 1-7/8 in
Split phase DAYTON $347.46
It is a bull.
I cut big holes in both sides of the box. It has its own cooling fan. Sawdust cannot get into it.
I planned an upgrade to the drum. Replace the Maple with Aluminum. It can be machined for wedges to hold the sanding medium. I mean Aluminum is light, right? Wrong! A 4" diameter by 11" long rod of solid Aluminum is heavy - really heavy. An upgrade for the pillow blocks - ones with grease fittings. Wedges and screws from a Jim sander. It will take a fabricator to center bore for the axel and grind the "V" channel. I am afraid to find out the cost of it.