Gearwheels From Hell

Updated: 27 Dec 2011
Link to www.geararium.org added
A celebration of unusual coggage
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The vast majority of gear wheels are wholly conventional and go about their daily rounds without fuss or bother. The extraordinary deviations from the norm that are pictured here are unusual,to put it mildly, and it is a moot point as to whether some of these drawings found a home in a real piece of machinery. If these perverse mechanical arrangements are the answer, you may need to change the question.

The drawings here are taken from the book "Mechanical Movements, Devices and Appliances" by Gardner D Hiscox, published by Sampson Low, Marston & Co in 1899. The contemporary descriptions from this volume are in quote marks.

Left: Intermittent Motion Of Spur Gear: 1

"A is the driver. The pin J and the dog L are on the front side of the gear; the pin R and dog P are on the back. This class of gears may be made in varying proportion to suit the required stop motion of the gear B, A being the driver."

Left: Intermittent Motion Of Spur Gear: 2

"In which the dogs G and F form a part of the driven gear B. This form allows of varying proportions of stop and speed motion in the two gears. A is the driving gear."

Apparently inspired by Munch's "The Scream":

Left: Variable Sectional Motion

"...from sector gears. The sectors are arranged on different planes, so that each pair shall be matched and all so adjusted that their teeth will mesh at their proper periods."

This process of adjustment seems to have failed in the example shown here. Two ratios (green and beige) are engaged at once, which would jam the whole thing solid.

By now you are probably thinking that this is all so much hot air, and that no-one would ever actually attempt to make gearwheels anything like this. Wrong...

Left: Variable gear ratio drive for water pump

This is the drive mechanism of a water pump built in the USA, which actually exceeds in surrealism the diagrams above. Not only do the larger driven gears have a non-constant radius, but the point of engagement is shifted back and forth between the three pinions on the driving shaft. These pinions are not only different sizes, but they are also mounted off center on the shaft. As the shaft rotates the point of mesh moves sideways to meet the side shifting teeth on the large gear. According to Terry Wilson, this sort of gear was very common on early gas powered water well pumps in the US. It gave high speed when the pump rod was descending, and a lot of torque when it was lifting the water.

Picture kindly provided by Terry Wilson.

Here is another demonic gearwheel in real life:

Left: Self-reversing gear drive on beetling machine

This remarkable gearwheel is part of the drive mechanism of a beetling machine in the Museum of Scotland, Edinburgh. "Beetling" is a process applied to linen, and cotton fabrics made to resemble linen, to produce a hard, flat surface with high lustre and to make the texture less porous; the fabric is dampened and pounded with heavy wooden mallets. You can see why a machine to do that would be a good idea- unless you were an unemployed hand-beetler, of course.

The small gear on the vertical shaft drives the large gear; after the latter has completed almost a full revolution the stub at the end of the vertical shaft encounters a curved abutment that helps guide the small gear shaft sideways so it engages with the teeth on the opposite side of the large gearwheel, which is then driven back in the reverse direction. If you look at the top of the large wheel nearest the camera there appears to be a notch at the end- in other words the end of the large wheel effectively consists of two teeth that move the small gear sideways and round the corner, so to speak. At the end of the travel the small gear swops sides again. Note the bearing just above the small gear, which allows for lateral movement.
Quite what the purpose of this forward/reverse drive was in the the beetling machine I could not determine; presumably a section of cloth needs to be repeatedly beetled.

Author's photograph

Left: Animation of the self-reversing gear drive

Showing how the vertical shaft swings sideways to reach each side of the large wheel.

Another fine animation by Bill Todd
Left: Demonstration model of non-circular gears in CNAM, Paris

This model was built by J Schroeder around 1860, and displayed at the Paris Exposition of 1867. The label on it says "Toothed rolling curves with frame and quadri-lobed wheels" which is more of a description than any sort of explanation. The arrangement will give a varying output speed for a constant input speed, but to what purpose?

There are dozens of similar models in glass cases, stretching down a long gallery in the museum, and this is by no means the strangest.

CNAM is the Conservatoire National des Arts et Metiers, a very fine museum. It is roughly the equivalent of the Science Museum in London.

Author's photograph. Sorry about the less than startling image quality; photographing things in glass cases is always tricky.

Left: Square-wheel watch by Maurice Lacroix

This watch, called the " Masterpiece Roue Carree Seconde" (square seconds wheel) is a clockwork design, with the unique feature of non-circular gears to drive the seconds indication. The clover-leaf wheel is driven in the usual constant-rate fashion, but the square wheel turns slowly when its corners are engaged, and faster when it is driven via the flat sections. A non-linear scale is therefore needed on the seconds dial, much of which is obscured anyway by the square wheel and pointer on top of it.

There is, of course, absolutely no technical justification for this unnecessary complication. It is just supposed to look cool. The other little dial is an up/down winding indicator.

You can see a rather nicely done animated promotion for this watch on YouTube.

Before you condemn this as a piece of Pathological Engineering aimed at men who have far too much money, pause. This watch is in fact a one-off created and donated by Maurice Lacroix to be auctioned for the Monaco Association against Muscular Dystrophy on 23 Sept 2011, along with 40-odd other unique designs. You can read more about this and revel in the technical details at: Worldtempus.


BIBLIOGRAPHY

Left: Noncircular gears, Design and Generation

I came across this weighty tome in Cambridge the other day. Full of interesting stuff, but at a high theoretical level and with some pretty advanced mathematics.

From Cambridge University Press. You can get it from Amazon


LINKS

The Website www.mekanizmalar.com has a number of interesting gear animations:

1) An epicyclic gear problem.

2) An unwrapped version of Ferguson's Paradox. (You need to switch on "Dials" and watch for a while to see the effect)
You can see some more usual versions of the Paradox here, and here.

3) Roman Kuzhlev's website at www.geararium.org has some interesting gears but most of them are of the conventional shape.

Typing "non-circular gears" into the search function of Youtube yields a large number of videos of weird gears squirming around in unsettling ways.

Here is one example

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