Croudsourced weather forecasting idea

I often hear grumpy old farts complaining about the accuracy of weather forecasts, and it seems that (grumpy, old) people who have lived in an area for a while actually do have a fairly good idea of the weather in their area. I guess this is based on experience noting prevailing conditions and subsequent weather patterns. Of course, this knowledge isn’t going to do anything for predicting weather in a neighboring city, but for their own area, they could probably be considered an expert. Considering that the Bureau of Meteorology (BoM) is making forecasts for large geographic areas, it isn’t surprising that they cannot match the accuracy of a local expert.

So, this got me thinking – a crowdsourced weather forecasting system. For a given region, users can predict the weather (rain/storm, hot/cold, humid, dry etc). Actual observations from the BoM and other recognised sources can be used to score the accuracy of predictions. Users can also rate the accuracy of predictions of other users. These ratings can be used to give confidence in future predictions.

I haven’t the time (or skill, really) to implement something like this – anyone want to have a go?

Burnt SATA power connector/cable

An interesting issue that I had to look at today – a burnt out SATA power connector. Some pictures:

Burnt SATA power connector

The connector on the control board

Burnt SATA Power connector - drive

Another view of the connector on the control board - note the scorching of the surrounding circuit board, but the lack of any burnt out components or tracks

Burnt SATA Power Connector

The SATA power plug. I think I see the problem here...

Burnt SATA power connector - molex plug of adapter cable

The Molex connector which fed the SATA power adapter cable. Note the damage to the insulation on the 5V line

Burnt SATA power connector - molex plug and wire of adapter cable

The Molex connector of the SATA power cable adapter. Note the break in the 5V wire where it was vapourised.

My guess is that the SATA connector, where it plugs into the drive, had some sort of short between the pins on the drive’s socket. It must have pulled a lot of current to so completely melt the connector, and vapourise the 5V (supply rated for 30A) copper conductor. There was no obvious damage to the circuit board or drive, ruling out a failure on the board/drive causing a short.

Using find in a bash script

Here’s something that will hopefully save someone the frustration that I experienced getting this working. I am writing a script that needs to traverse a directory structure, then operate on the files it finds (read DICOM tags, modify/add tags). The reading and modifying was simple enough, but I could not get find to work inside the script, so basically resorted to running a command like:

$ find . -type f -exec {} \;

That worked fine, but I really wanted to have it all integrated into a single command. The problem I had was that the output of a find command couldn’t be used to iterate in a for loop – as a scalar (FILES=`find . -type f`) it was a single string, and as an array (FILES=(`find . -type f`)) elements would be split on spaces and newlines, which breaks if your paths have spaces in them.

The trick here is to change the IFS variable, which tells bash what to split strings on (by default it is space, tab or newline).  In my case, the output of find is separated by newline characters. Change it to a newline and now it works as expected. yay! Here’s the code:

# IFS controls how bash splits strings (by default, whitespace.
# change to newline
# dummy function for demo
fileops () {
    echo $1
FILES=(`find "$1" -type f`)
    for i in "${FILES[@]}" ; do
fileops "$i"
# restore IFS

Potential safety issue and poor warranty support- Tasman Eco Sienna Cot

A problem I have encountered with the Tasman Eco Sienna Cot.

Approx 4kg of force applied to dropside causing deflection   pin detached from guide channel, causing gap

Description of problem:

The drop side rail is coming loose from the cot. The slide mechanism no longer retains the rail securely, and the cot dropside has been damaged by the locating pin as a result of dislocation.

At one end of the cot, the upper guide pin of the dropside mechanism no longer engages the channel in the cot side. It appears that a tensile loading on the pin (eg outward force placed on the cot end) has damaged the plastic channel material, in particular, the ‘lip’ of this channel which retains the head of the guide pin. No excessive loads have been placed on the cot – only normal usage. On inspection, it appears that the plastic channel lip is not of sufficient strength to withstand forces in normal use, considering that they support any outward load on the cot ends.

Any light loading on the cot end (eg infant leaning against, carer applying any light pressure) is sufficient to dislodge the guide pin from the channel. This is unsafe as the dropside is now only supported at three corners. This could present a falls risk if the infant stood and leaned against the unsupported corner and it deflected sufficiently to allow passage. Alternatively, it could present a pinching hazard as the gap present between the drop side and cot end is v-shaped, and would channel and trap digits and small limbs. As the dropside mechanism no longer functions, the cot side either needs to stay in the up position, creating a back injury hazard for the carer, or in the down position, potentially allowing infants to egress over the dropside, causing a falls hazard.

A service agent has replaced the dropside guide channel, however the problem is still present. Changing the dropside position dislodges the guide pin and damages the guide channel as above. The service agent mentioned that this is in fact a common problem, and it is caused by misalignment of the guide pin or screws holding the guide channel, usually caused during manufacture.

Tasman Eco have not yet resolved the problem, despite having lodged a warranty claim more than one month ago.

This problem has been reported to the ACCC (via They have not contacted me for further information, most likely as they are still monitoring the market for complaints. I would encourage any users encountering similar problems to report them via so that they are made aware of the extent of the problem, and investigate further.

The Rat Arrow

Both Rat in that it is made from scrounged urban materials, and Rat in that it can be used on small game (including rats, if you were so inclined). There’s a lot of traditional archery enthusiasts, but I wanted to try making a “modern traditional” arrow. The sort you’d find in use in the slums of a big third world urban slum, or a post-apocalyptic wasteland.

Overall I’m fairly happy with the arrow. Flight is reasonable, and it is very tough. The difficult part would be making a set with matching spine, but as a one off this is reasonable. Here’s how I make it.

(All measurements are in metric, cause imperial are the sorts of units that bitches use.)

The shaft is made from a small culm of South Kalimantan Bamboo, a small clumping bamboo variety. Pretty much any type of bamboo with appropriately sized culms could be used though. Bamboo garden stakes are a good source if you don’t have access to any plants.

The shaft was cut to approximately one metre. Straightening was achieved by heating with a butane blowtorch, straightening, then setting by wiping down with a wet rag. The shaft was then cut to approximately 840mm (33 inches for the bitches). The shaft was sanded down, in particular the nodes to reduce the bulging.

A self nock was then cut by sawing a slit with a tenon saw, then enlarging with a thin file. Electrical tape was wrapped just ahead of the nock to reinforce it and stop it from splitting.

It is important to note that the nock is at the narrow end of the shaft. This is something I’ve noticed isn’t talked about too much, but it is important to nock at the narrow end, not the thicker end as you might expect. My initial reasoning was that since it is being driven from the nock end, the strongest/stiffest portion of the arrow should be there. However, for correct flight, the arrow’s centre of gravity needs to be forward of it’s aerodynamic centre (given the simple shape of an arrow, it’s aerodynamic centre is, unlike a plane, pretty much the same as its actual centre). One of my initial attempts had the nock at the thick end. This lead to very unstable flight, with a lot of yawing during the flight. Centre of gravity was pretty close to the aerodymanic centre. Adding weight via wraps of solder at the tip helped this, although at the expense of a heavier arrow.

The head of the arrow is an M5x20mm hex head bolt, weighing around 6 grams (again, for the bitches, around 100 grains). The hollow was enlarged by hand with twist drills, then it was epoxied in. Electrical tape is again used to reinforce the bamboo around the head.

(the screw in points I have all have a shoulder that is approximately 5mm diameter – these can be expoxied into the hollow. Inserts for 1716 alu arrows should be around 6.33mm, so could be used for larger diameter bamboo arrows)

Fletching was made from chicken feathers (thanks to Ethel and the other ladies). Polyester thread was used to bind the feathers front and rear, and superglue along the fletching and to hold the threads in place.

Finished, here are the specs:

  • Total Length: 845mm
  • Weight: 55g
  • Centre of balance: 355mm from tip, which is 8% forward of centre (in terms of the entire arrow’s length)
I’m happy with how it shoots. Plenty of punch. Here’s what it did to some 7 ply 11mm plywood board, at around 7m from a 32lb recurve.

I’m planning on making a spine testing/fletching jig, so for subsequent arrows I’ll be able to roughly match for spine, and also apply feathers/vanes more consistently. I am also going to make some steel dies which I can force the culms through, hopefully reducing the need for sanding nodes down to get roundish shafts.

Some general bamboo arrow making tutorials which I found helpful are here and here.




Slingshot laws in Queensland

I thought I’d do a bit of research to find out exactly where we stand with regards to slingshots in Queensland. Basically, as far as carriage and use, they’re treated very similarly to firearms. As with knives, self defense is specifically stated as not being a valid reason/excuse for carrying.

First of all, getting them. Customs prohibits the import of slingshots which feature a forearm brace, but any others they let through.

On possessing slingshots, this is governed by state law. The Queensland Weapons Categories Regulation 1997 makes no mention of slingshots or similar devices falling under any category. The Queensland Weapons Act 1990 does make several mentions of slingshots, mainly to do with lawful possession and use. A summary:

  • Must not discharge a slingshot on private land without the owner’s permission
  • Must not possess/carry a slingshot on private land without the owner’s permission, unless it has been disassembled and cannot be readily discharged
  • Must not carry a slingshot in exposed view in a public place
  • Must not carry a slingshot capable of being discharged in a public place
  • Must not discharge a slingshot in, into, over, towards or through a public place
  • Must not engage in conduct that will cause injury/death, damage to property or alarm to another person.
  • Must not possess or use a weapon if under the influence of alcohol or drugs.
  • Self defence is not a valid reason/excuse to carry a slingshot

What really stands out for me (besides common sense) is that if I am carrying a slingshot, it is best to have it disassembled (band removed), and not to have one at all if I have had even just one drink. Other than that, provided I don’t use it in public or on someone else’s land, and don’t act in a way which could be viewed as threatening, I should be fine.

Below are copies of the relevant sections of the Weapons Act 1990.

56 Discharge of weapon on private land without owner’s consent prohibited

(1) In this section—owner of private land includes the occupier of the land.private land means land that is not a public place.weapon includes an antique firearm, spear gun, longbow and slingshot.

(2) A person must not, without  reasonable excuse, discharge aweapon on or across private land without the express consentof the owner.Maximum penalty—20 penalty units or 3 months imprisonment.

(3) A person must not carry a weapon on private land without theexpress consent of the owner unless—

(a) the person has a reasonable excuse; or

(b) the weapon is unloaded, broken or for another reasoncan not be readily discharged.Maximum penalty—20 penalty units.

57 Particular conduct involving a weapon in a public place prohibited

(1) In this section—weapon includes—

(a) an antique firearm, spear gun, longbow or sword; and

(b) a replica of a weapon; and

(c) a replica of a thing mentioned in paragraph (a); and

(d) a slingshot or shanghai.

(2) A person must not, without reasonable excuse, carry a weaponexposed to view in a public place.Maximum penalty—20 penalty units or 3 months imprisonment.

(3) A person must not, without  reasonable excuse, carry in a public place a loaded firearm  or a weapon capable of beingdischarged. Maximum penalty—60 penalty units or 1 year’simprisonment.

(4) A person must not, without  reasonable excuse, discharge aweapon in, into, towards, over or through a public place.Maximum penalty—100 penalty units or 2 yearsimprisonment.

(5) It is a reasonable excuse for subsection (2) to carry a swordexposed to view in a public place—

(a) to perform a lawful activity, duty or employment; or

(b) to participate in a lawful entertainment, recreation orsport; or

(c) to exhibit the sword; or

(d) for use for a lawful purpose.

Example for paragraph (a)—A person may carry a sword for ceremonial purposes at anofficial function attended by the Governor.

Example for paragraph (b)—A person may carry a sword as an accessory while playing in apipe band.

Example for paragraph (c)—A person who collects swords may exhibit them at a fete oranother public gathering.

Example for paragraph (d)—A person may carry a sword as part of an official uniform theperson is entitled to wear.

(6) It is not a reasonable excuse for subsection (2) or (3) to carry aweapon in a public place for self-defence purposes.

(7) In deciding what is a reasonable excuse for subsection (2) or(3), regard may be had, among  other things, to whether theway the weapon is carried, or when and where it is carried,would cause a reasonable person  concern that he or she, orsomeone else in the vicinity, may be threatened or harmed.

58 Dangerous conduct with weapon prohibited generally

(1) In this section—weapon includes—

(a) an antique firearm, explosive tool, captive bolt humanekiller, spear gun, longbow or sword; and

(b) a replica of a weapon; and

(c) a replica of a thing mentioned in paragraph (a); and

(d) an explosive; and

(e) a slingshot or shanghai.

(2) A person must not—

(a) without reasonable excuse; and

(b) by the physical possession or use of a weapon;engage in conduct, alone or with another, likely to cause—

(c) death or injury to a person; or

(d) unlawful destruction or damage to property; or

(e) alarm to another person.

Maximum penalty—100 penalty units or 2 years imprisonment.

59 Possession or use of weapon under the influence of liquor or a drug prohibited

(1) In this section—weapon includes—

(a) an antique firearm, spear gun, longbow or sword; and

(b) a replica of a thing mentioned in paragraph(a); and

(c) a slingshot or shanghai; and(d) an explosive.

(2) A person must not have physical possession  of or use aweapon if the person is under the influence of liquor or a drug.

Maximum penalty—20 penalty units.