Monthly Archives: May 2007

The Beverly Clock

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The beverly clock has an ingenious power source. It has a sealed container of air that expands and contracts with temperature differences throughout the day. I’m envisioning a sealed plastic box with a hole cut in the top, and a flexible material over the hole (like a balloon). This material would be connected to a toothed bar interlocking with a gear, connected to a pulley over which the weight and chain that normally run these clocks hangs. The toothed bar only grips the gear in one direction, and when it does it turns the gear/pulley and winds the chain. When the temperature and therefore the pressure of the air in the box fluctuates, it moves the toothed bar up and down, winding the chain. This means that the natural behavior of the environment winds this clock.

It would be difficult to get much productive power out of this setup, but it’s a novel approach to the problem and might be worth keeping in mind.

Ballista Trigger

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A month or two ago I was reading a book on Greek and Roman engineering and was inspired to make a ballista. It was pretty simple and worked reasonably well for the nonexistent amount of planning that went in to it. Pictures can be seen here. The only engineering hurdles it didn’t accomplish were adequately maintaining and adjusting tension in the springs, and a trigger mechanism to hold the string until it’s ready to fire.

I just finished a design for a trigger that uses only parts that were available in ancient times (maybe not quite, but if this were the size of real ones it could be).

Ballista trigger design

The only thing that worries me is the placement of the rod in the slider. Since the position in which it holds the most tension is where the rod tries to slide forward, I’m afraid it will be easier for it to slip slightly out of position without having to move the slider down. Regardless, this will just be minor slippage so it shouldn’t be a problem. If it works well I might make two of these, one from wood for the actual weapon, and a second from plastic for demonstrating how it operates.

Speaking of ballistae, does the maker faire catapult competition sound awesome to anyone else? I would have gone just for this had they made it known with more time before the event, but alas they didn’t. Is anyone interested in doing something similar in Chicago? I bet there’s enough nerds in Chicago interested in making weird stuff to have a decent competition.

Student Run Companies

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The other day I saw this device linked from digg. It’s not really that special, just a machine for climbing rope really fast. It’s certainly a nice piece of engineering, and it’ll be useful in certain professions, but the thing that really gets me about the article is this:

The students founded a company, Atlas Devices, based in Cambridge, MA, to commercialize the device, which is about the size of a power drill.

Too many times I’ve seen this same story. Students from MIT invent some cool device and start a company selling it. Why is it so easy for them to start companies like that all the time? Isn’t it hard to develop an idea into a marketable product? Is MIT doing anything else but forming groups to develop products? Most importantly, why haven’t they given me a call yet? ;)

Materials: The Most Important Engineering?

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I’m watching “Ancient Discoveries: Machines of the East” on Discovery and as usual, there’s some amazing things those ancient inventors came up with. I just saw a device that pours a fixed amount of water at a fixed interval. It used a siphon and a float based valve like that in a modern toilet. The show said this showed an advanced knowledge of differential pressures, which is used today to make jet engines. Was the only thing stopping them from making jets a lack of the materials that could withstand those forces?

There’s seems to be a first key invention that starts a field of science/engineering, like the discovery of the wheel to mechanics, electricity to electronics, etc. But beyond that, could it all be a matter of making the “things” of your discipline out of lighter, stronger, or other interesting materials?

This idea is just off the cuff, I’d like to hear some comments either way.