3047: Rotary Tool

|< < Prev Comic #3047 (February 5, 2025) Next > >|

Rotary Tool

Title text: It was great until my thumb slipped and I accidentally launched my telescope into the air at Mach 8.

Explanation

It is common to find multipurpose handheld tools that can function as higher-speed drills and lower-speed screwdrivers, switching between modes with a slider. The tool in this comic appears to have extended that concept to the extreme, covering both very high-speed and very low-speed tools. Presumably the tool has a rotating part at one end that can accept multiple attachments to facilitate the different uses.

All of these speeds are sensible for the specified uses. However, engineering a single tool to perform reliably across the required range of speeds is likely to be deeply impractical. Equally, designing the base unit such that it can be usefully employed to all these purposes would be a substantial challenge. For example, a household drill needs to be both portable and reasonably bulky, whereas a record player needs good stability, and a dental drill needs to be small enough to be moved flexibly and delicately. In any case, it's highly unlikely that any individual would have a need for all these uses,^{[citation needed]} so the market for such a tool would be extremely limited.

The title text highlights one of the downsides of combining functions in this way — the potential for using the wrong setting for the task at hand, by carelessness or clumsiness, with detrimental effects. In this case, while attempting to use the "sidereal telescope mount" option with an actual telescope, the user accidentally changed the tool to a much higher speed setting, launching it into the air, on a ballistic trajectory with hypersonic speed. More commonly, attempting to insert a screw while on the drill setting could cause damage to the item being screwed together, the screw itself, or the screwdriver bit.

The precession setting refers to the precession of the equinoxes (axial precession), which happens on a 26,000-year cycle that corresponds to the RPM rate shown. The average person does not need to adjust their telescope for such minor shifts, certainly not on a constant basis. This may be beneficial for scientists making precise measurements but they would have more powerful and dedicated tools to this end. For commercial use by the public, this would not be remotely necessary.

The Dremel tool referred to is a high-speed, low-torque rotary tool that can be fitted with a variety of bits for cutting, sanding, grinding, sharpening, polishing, engraving, machining, etc.

The speed of the dental drill might seem excessive, but according to Sable Industries, a manufacturer of high-speed dental drills, they can run "at speeds of between 300,000 and 450,000 RPM." They squirt water as they rotate to cool the bits down, so they don't overheat (a further design complication for this multitool).

The speeds labeled "record player" are intended to correspond to standard rotational speeds of phonograph records. The intended playback speed standardized at 78 rpm (not 72 rpm as depicted in the comic) in the 1920s, with a record diameter of 10 inches. The speed and size, as well as the required width of the groove encoding the music, dictated a playing time of about 3½ minutes per side; collections of 78 rpm records were released as albums. Beginning in the late 1940s, records designed to be played back at 33⅓ rpm (close enough to the 33 rpm in the comic) were produced, to allow longer play times (hence the LP designation, for "long play") on similar-sized records, which standardized on a 12 inch diameter. This was commonly used to release an collection of songs on a single disc, still called an "album", totaling about 22 minutes per side. Concurrently, an alternative format, 7 inch diameter records designed to be played at 45 rpm, was produced, allowing about 5 minutes per side. This was often used to release "singles" (a single song on each side of the record). The 33⅓ and 45 rpm playback speeds supplanted 78 rpm, and remain the standards today.

Function	Speed (rpm)	Rotation / Revolution Period	Diameter of Bit for Mach 8 Launch Speed	Notes
Sidereal mount precession adapter	0.000000000073	~26,000 years	4799 au	see axial precession
Sidereal telescope mount	0.00070	23.93 hours	74,866 km	rotates once per sidereal day
Hour hand on a clock	0.0014	12 hours	37,733 km	Typical 12-hour analog dial (as opposed to a 24-hour analog dial)
Minute hand on a clock	0.017	60 minutes	3,144 km
Second hand on a clock	1	1 minute	52.4 km	By definition a second hand rotates at 1 rpm because it completes a single rotation each minute
33 rpm record player	33	1.8 seconds	1,588 m	It's actually 33⅓ rpm
45 rpm record player	45	1.3 seconds	1,165 m
72 rpm record player	72	0.8 seconds	727.9 m	probable typo for 78 rpm
Screwdriver	300	0.2 seconds	174.7 m	Screwdrivers rotate much slower than similar looking drills to avoid stripping the screws
Drill	1,500	40 milliseconds	34.9 m
Airplane propeller	2,500	24 milliseconds	21.0 m
Dremel	35,000	1.7 milliseconds	149.7 cm	The speed of a basic Dremel, many Dremel tools have variable speeds from 5,000 to 35,000 rpm
Uranium enrichment centrifuge	60,000	1 millisecond	87.3 cm
Dental drill	300,000	0.2 milliseconds	174.7 mm

[Notes: 1) All speeds are rounded to two significant figures, which may result in some variance from the intended result when trying to calculate revolution times from them. 2) Mach 8 launch speeds based on stated RPMs 3) Mach number is actually defined by the local thermodynamic temperature. All the above will be based around the velocity at STP, or thereabouts, although the larger radii would necessarily involve travel through higher latitudes, into space or far beyond, where such a measure rapidly becomes meaningless.]

Transcript

This transcript is incomplete: Do NOT delete this tag too soon. If you can fix this issue, edit the page!

Multi-function rotary tool

[A close-up of a stick-shaped tool, where on the side of a section is a panel with a slider adjustable in various levels annotated with numbers and texts. Besides the panel there are some invisible inlays. One visible end of the section is attached to another section.]

Speed (rpm) Function

0.000000000073: Sidereal mount precession adapter

0.00070: Sidereal telescope mount

[Following three are labeled "clock hands":]

0.0014: h

0.017: m

1: s

[Following three are labeled "record player":]

33: 33

45: 45

72: 72

300: Screwdriver [Current setting]

1500: Drill

2500: Airplane propeller

35 000: Dremel

60 000: Uranium enrichment centrifuge

300 000: Dental drill

  Add comment        Create topic (use sparingly)       Refresh 

Discussion

How come it's at 0.017 RPM for a minute?? and yet 1 RPM for a second? pls fix this randall Midnightvortigaunt (talk) 18:01, 5 February 2025 (UTC)

Its 0.017 RPM for the minute hand. The minute hand revolves once per hour or at 1/60 RPM ≈ 0,017 RPM --172.71.148.59 18:14, 5 February 2025 (UTC)

Ohhh that makes sense I didn't think about it like that Midnightvortigaunt (talk) 19:27, 5 February 2025 (UTC)

Mr.Dude (talk) 17:20, 7 February 2025 (UTC) I wonder what torque is needed to launch the average backyard telescope worthy of a tracking mount at Mach 8 given standard state pressures and temperatures of perhaps average conditions found in Randall’s back yard.

How come the comment above is invisible to me? 172.68.245.229 18:03, 5 February 2025 (UTC)

Possibly because people indented with spaces rather than with colons? 162.158.79.77 19:40, 5 February 2025 (UTC)

72 RPM for a record player...? 162.158.74.25 18:08, 5 February 2025 (UTC)

I could only find 78 RPM disks in the german wikipedia. 172.70.114.56 18:41, 5 February 2025 (UTC)

I came here to make the same comment: 72 is most probably a typo. The old records (at this date, very old, since the transition to vinyl records was 1948 to 1958 (in the US)) were 78 rpm, not 72 rpm https://en.wikipedia.org/wiki/Phonograph_record Rps (talk) 19:30, 5 February 2025 (UTC)

72 is (for example) relevent to font sizes (size 1 = 1/72 of an inch, size 72 = 1 inch), which might therefore have envaigled Randall's head for numbers by a different route, and got him confused. Conceivably he has had to deal with playing old 78s, but probably not for a long time... even the retro-revival of vinyl, recently, has probably not had quite so many old old records released to fill such nostalgic needs. So an easy brain-fudge/thinko to trip over on. 162.158.74.48 00:54, 6 February 2025 (UTC)

There used to be a record label call 72RPM records. 172.69.229.146 (talk) 19:07, 5 February 2025 (UTC) (please sign your comments with ~~~~)

We need one of those tables in here. DollarStoreBa'al (talk) 18:37, 5 February 2025 (UTC)

I made a change to the explanation that all of these numbers are realistic because, I checked out the speed of dental drills and they really do rotate that fast. I haven't checked out all of the other tools, but I suspect that they are also accurate. If you find that any of them are misstated, please correct my correction. Rtanenbaum (talk) 22:38, 5 February 2025 (UTC)

TABLE REQUEST When someone uploads a table, I'd like to recommend a second column for the frequency / reciprocal of the speed. "0.000000000073 minutes" is one every 13.7 billion minutes, or ~26,000 years. Thanks! 172.70.46.107 20:20, 5 February 2025 (UTC)

Me again. Should the column header "revolution time" be "rotation time"? In every instance, the axis of motion is within the object itself; even the second/minute/hour hands go around the axis. 141.101.76.73 16:41, 6 February 2025 (UTC)

TRIVIA 16 2/3 RPM phonographs were used for some voice-recorings back in the day. 172.68.26.24 21:01, 5 February 2025 (UTC)

My parent's old record player (60's, probably) had 4 possible speeds: 16, 33, 45, 78. By the early 80's the current ones only had 33 and 45. Rps (talk) 16:59, 7 February 2025 (UTC)

Album goes back to stacks of 78s. A symphony or opera would be 2, 3, 4 or more disks. They were bound like a photo-album with a leaf for each disk. "78" wasn't "standardized" until the format was fading. 3600-rpm motor and 46-tooth gear is incomplete (one tooth gear??) Early discs were from 60 to 130 rpm. Users would adjust speed by ear (also to ease pitch-matching for karaoke). Only as LPs arrived did someone invent the number "78.26 rpm" (no recordplayer and few lathes of the period were near that accurate). --PRR (talk) 02:34, 6 February 2025 (UTC)

Indeed, my parents had a large collection of old records and at least one had a speed marking of 80rpm.--172.68.186.43 09:17, 6 February 2025 (UTC)

With wind-up players, a lot of them started off playing at one speed and ended playing at a completely different one anyway...172.68.186.50 09:43, 6 February 2025 (UTC)

I suspect there's not many consumers needing a Uranium Enrichment Centrifuge... at least outside of a few countries in the Middle East. --172.70.58.6 08:50, 6 February 2025 (UTC)

Might face some regulatory / export license issues too.172.70.86.129 11:34, 6 February 2025 (UTC)

I feel like there was a lost opportunity to have Dr. Who's Sonic Screwdriver on the list. Maybe the rpms are unknown.162.158.159.107 13:05, 6 February 2025 (UTC)

The table says that 0.00070 "seems off; a sidereal day is 23.93 hours". That's just because (like all of the other settings) 0.00070 is quoted with only 2 significant digits. Every period between 23.64 and 23.98 hours would round to 0.00070 RPM. 162.158.134.199 13:58, 6 February 2025 (UTC)

The question I have is: why are dental drill speeds so high? 172.70.247.92 17:21, 6 February 2025 (UTC)

"why are dental drill speeds so high?" It hurts less. (Are you old enough to remember routine use of belt-driven dental drills?) You can cut a given amount of material (wood, steel, tooth) quickly with heavy force or high speed. Neither is really fun, but hi-speed is generally preferred. --PRR (talk) 19:08, 6 February 2025 (UTC)

Although some materials behave badly to heat (either work-hardening, for some alloys, or melting/burning, like plastics) and that's why variable-speed hand-drills/etc usefully have low speeds (for essentially the same force, when that's done via reostat rather than an actual gearbox). On the few occasions I've had my teeth drilled, I'm pretty sure I've detected the pungent smell of fried tooth-fragments, but it was nothing like as strong as smelling my own nose-flesh being burnt one of the times I had it cauterised to try (and fail) to prevent excessive nosebleeds. 172.69.79.139 21:15, 6 February 2025 (UTC)

The latest NMR CPMAS probes send their rotors to go at 9.6 Mrpm, M=mega. [1] --172.69.109.172 21:56, 7 February 2025 (UTC)

Should we list the rotor diameters to achieve the mach 8 speed mentioned in the title text in the table? I don't think that we should. guess who (if you desire conversing | what i have done) 06:01, 24 February 2025 (UTC)

I (obviously since I worked it all out) think it is in the spirit of the ridiculous idea of the comic and XKCD generally to do these calculations. That said, I'm getting different numbers than your update to make it Mach 8. Denver87 (talk) 16:21, 24 February 2025 (UTC)

I get the following: 4,799au, 74,866km, 37,733km, 3,144km, 52.4km, 1,588m, 1,165m, 728m, 175m, 34.9m, 21.0m, 149.7cm, 87.3cm, 174.7mm. Denver87 (talk) 16:21, 24 February 2025 (UTC)

Happy to share calculation notes, but here's the example for the dental drill: 300,000rpm = 5,000 rps; diameter of: 174.7mm --> circumference of: pi * 174.7mm = 548.8mm; 548.8mm * 5000rps = 2,744,000mm/sec = 2744m/sec; Mach 8 = 8 * 343m/sec = 2744m/sec. Denver87 (talk) 16:21, 24 February 2025 (UTC)

If you agree with the calculations, one of us can at least update it. Denver87 (talk) 16:21, 24 February 2025 (UTC)
        Add comment