Oct
24
2011
3

Gas Downdraft Stove (mod 1)

Gas downdraft stoves are an interesting backpacking tool.  So I thought I’d make one and try it out.  It has passed the “driveway tests” with flying colors.  The design is derived from plans available from section hiker so I will mostly describe the differences.

The major difference is that I used one large piece of hardware cloth and four #6 bolts with standard washers, lock washers and nuts.  Two of the bolts hold the hardware cloth wrapping together and the other pair of bolts stabilizes the alignment between the can and the hardware cloth (keeping it all square).   I found that the fancy t-washers were largely a waste of money and didn’t help with either assembly or stability.

Schematic drawing of stove

Schematic drawing of stove

This made the manufacturing process easier and makes the stove cooler to handle as the hardware cloth is removed from the side of the can. The total weight after burn in is 101 grams, so this is not a large weight penalty.

To use the stove, fill with short pieces of wood laid sideways (some designs place them up and down, which didn’t work quite as well). The wood should not be much larger than a pencil. I was able to use pine straw and small tinder to start it (pile on top and let it burn down). Once it is going the nearly colorless flames extend quite high.

The working stove

The working stove

It is hot, burns for about 10-15 minutes and I think will work. I’m more optimistic about this than ethanol stoves.  (it is also approved in the “guide to safe scouting” as it isn’t a home made liquid fuel stove)

Oct
21
2011
0

Change your router password

I just read about a rather neat attack on routers – both wireless and wired ones.  Since you can supply a login id and password to an html query (http://user:password@site), it is not hard to have a script running locally on your machine that would log into a router set with default values and have it configure the router in an insecure manner.  In essence, a web page could set up the router to be remotely configured and thereby be vulnerable to all sorts of nasty fun things (how about a special firmware upgrade that makes it into a malware server or phishing workstation?).

The simplest solution to this is to change the password from the default.  It helps if you can change the account name, and if you use a different local network as well.

Cute, isn’t it?

Written by Rob in: engineering,security |
Oct
21
2011
0

The Wierdest Hardware Bug

Just a quick post, but one of the machines I built at home would crash in a somewhat random manner with the display locking up.  Sometimes several times in a row, but with no obvious pattern of cause and effect.  It did seem to be connected with the graphics system, so I was wondering about a new card, but hadn’t gotten around to fixing that.

Anyway I had a chance to replace the ancient CRT monitor (vintage 1995) with a new LCD one due to a house move.  Suddenly the machine is stable.   Apparently the monitor was creating voltage spikes or electronic noise which was upsetting the computer.  (They shared a common surge suppressor/line noise eliminator, but that wouldn’t have stopped what was in essence a ground loop).

So changing the monitor fixed the problem.  Go figure.

Written by Rob in: engineering |

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