Since I was going to be spending the whole day gluing up slabs for RP doors, which is boring as hell, I decided to try a test of the idea I had about using a light bulb inside of the machine cabinets to ward off condensation and rust. I'm no scientist, having spent my undergraduate years as a lowly philosophy major, so my testing may not be up to snuff - I did the best I could. I figured I'd gather up some data and ask smarter folks what it means.
My shop ain't Dexter's Lab, by a long shot, so I had to work with what was available to me. Since I was going to be using the tablesaw during the day, I decided to run the test using the shaper as a test subject. The tablesaw has a lot less surface area overhanging the cabinet enclosure and would perhaps respond better to the light bulb treatment.
Problem: When a cool/dry air mass is followed by a warm/moist air mass and the transition is somewhat rapid, as sometimes occurs in my area of Pennsylvania in the Spring and the Fall, condensation forms on the cast iron surfaces of the stationary machinery, causing rust.
Proposed Solution: An incandescent light bulb, left on overnight, mounted within the cabinet, may provide enough of a rise in temperature over the ambient temperature/dew point to eliminate condensation and rust.
Test Subject: Delta "Platinum Edition" Cabinet Shop Shaper. Cabinet Enclosure: Sheet Metal - 19-1/2" x 19-1/2". Top: Cast iron - 40" x 27". Note: Cast Iron Top overhangs Cabinet Enclosure by 10-1/4" on each side and by 3-3/4" on front and back.
Heat Source: Sixty Watt Incandescent Bulb in Clip On Fixture, mounted
2" away from under side of cast iron top, within cabinet enclosure.Test Instruments: (1) Amprobe Digital Sling Psychrometer, Model THWD-1, (2) Unknown Brand Digital Thermometer/Hygrometer (Note: This was not capable of decimal readout, so all numbers for it are whole), (3) Aquarium Thermometer, of the type intended to be applied to the exterior surface of the glass on an aquarium - mounted on the edge of the cast iron top (Note: this was not tested against the other two instruments but was put on in an attempt to gauge the actual surface temperature of the cast iron top - it is only capable of reading out in two degree increments). The instruments (1 and 2) were sat next to each other for one hour and gave the same readings (within their abilities) before the test.
The Test:
The Unknown Brand Thermometer/Hygrometer was left at the workbench and the Digital Sling Psychrometer was used at the Shaper, which was approximately 8' away. True surface temperature of the cast iron top could not be measured with the instruments at hand. The Digital Sling Psychrometer was laid on it's side, with the sensor approximately 1/2" above the cast iron surface.
The Digital Sling Psychrometer was positioned in the approximate center of the area over the cabinet enclosure in Test Position "A" and was positioned approximately 1" from the edge of the overhanging portion of the cast iron top in Test Position "B". The approximate distance between the two test positions was 19". The instrument was moved from position "A" to position "B' at half-hour intervals.
Results:
At Test Position "A" (center of cast iron top, over cabinet enclosure).
Hour Temperature/Ambient Temperature/Test Position "A"
0 63f 62.2f 1 63f 67.1f 2 64f 68.2f 3 63f 68.4f 4 63f 68.4f 5 63f 68.7f 6 63f 68.4f 7 62f 67.8f 8 62f 67.2fAt Test Position "B" (approximately 1" from edge of cast iron top).
Hour Temperature/Ambient Temperature/Test Position "B"
0 63f 62.2f 1 63f 63.8f 2 63f 64.3f 3 63f 64.6f 4 63f 64.6f 5 63f 65.0f 6 62f 64.6f 7 62f 63.5f 8 61f 63.9fNOTE: At the end of the test, the aquarium thermometer, applied to the surface of the cast iron table, read 68f next to Test Position "B", when the Digital Sling Psychrometer read 63.9 at Test Position "B". It read 76f next to Test Position "A" when the Digital Sling Psychrometer read 68f at Test Position "A".
Conclusion: Damned if I know. I'm hoping that some smart person can tell from the data if the light bulb idea will work.
Regards, Tom Thomas J. Watson-Cabinetmaker Gulph Mills, Pennsylvania