Day 747, Solo waxwing

No previous owners.

High mileage.

Very blurry.

Going for a song.

Honestly, it's in there somewhere.


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Day 746, Street Mole Rat

Right under your feet, everywhere you go, perhaps even under your bath.

The street mole rat is with you.

Behind the wainscoting of society.

In fact here's one now, peering at us from its lair.

Actually not as impressive in real life, and rather like a plastic bin for delivering groceries.

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Day 745, Off, on, off, on

In, in, out, out - in, out, in, in.

For best results it would be ideal to be in rather than out.

In the case of the DE9 or DB9 subset of the RS232 standard the pins are configured like this:

1	Data Carrier Detect	in
2	Receive Data	in
3	Transmit Data	out
4	Data Terminal Ready	out
5	Signal Ground	-
6	Data Set Ready	in
7	Request to Send	out
8	Clear to Send	in
9	Ring Indicator	in

Interestingly the 'ins' outnumber the 'outs' by a ratio of 62.5:37.5

Surely it ought to be more equitable however you look at it.

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Day 744, On balance

This should have been obvious, hard disk drive spindles have balance weights added to ensure smooth running.

It never occurred to me that they would have balance weights, but then I've never thought about it in any particular depth.  But hey, when did ignorance of a subject stop people from making massive assumptions.*

So why are there balance weights and why should it be obvious?

An imbalance can occur in a rotating object when there is a disparity between the centre of gravity of the rotating system and the centre of rotation for the rotating system.  An imbalance in a rotating system causes vibration.**

Let's consider this in the context of motor vehicles and their wheels.  A vibrating car wheel can be felt through the steering column and will be noticeable in uneven wear of the tyre, there is also a strong likelihood of earlier than normal failure of a wheel bearing due to the increase in stress and wear.

In a system such as a hard disk drive assembly, where there is are very fine tolerance of distance between read/write heads and the disk surface, a few nanometers,*** any vibration of the disk surface will lead to an increase in data read and write errors.  Over time there will also be greater wear on the hard drive spindle which will exacerbate the existing imbalance and lead to premature failure of the disk drive.

In both the case of the motor vehicle and the disk drive spindle small weights are added in places appropriate to remove the imbalance in the rotating system.  When you next walk along a pavement take a look at the shoulder of car wheels, just next to the tyre, and it won't be long before you start to spot the lead balance weights attached to the wheel rim.

If you've ever heard of wheel balancing before, for cars, bikes, buses, etc, then why would it not be obvious after a small amount of consideration that there might be a similar requirement in other types of rotating system.  Of course it would only be obvious if you have a particular amount and type of prior knowledge.****

The tiny weights below shown removed from the disk spindle, presumably colour coded to indicate different mass.

* You know what I'm getting at.
** Don't take my word for it, here are some experts explaining this at great length in a patent application.
*** Don't take my word for it, here's an article from IEEE Transactions on Magnetics where some experts explain it at great length and in great detail.
**** I actually went "oh look, balance weights!" and was momentarily (a few nanoseconds) surprised, thus giving me an excuse for an overly verbose blog.


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Day 743, Off track

Here it is, an off-track, on-roller, turbo-trainer tyre.

I have no idea whether any of the hyphenated words above needed hyphens or not.

It should probably be 'turbo trainer'.

However, it doesn't really matter does it.

Just get on and ride off.

Although essentially there is no 'off' as you will be stationary.

Unlike an envelope.*

* e for envelope - stationery.

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Day 742, This is not a language

The BBC Master, kit off, chips out.*

The BBC Master below is displaying all the signs of having lost its settings, the batteries are dead.

In fact the batteries aren't just dead, they are also giving off decompositional fluids.  How very delightful.

Leaking batteries?  No problem, first check to see whether the batteries are alkaline or acid - these are alkaline.

Use white vinegar to clean alkaline battery leaks.  Once the batteries were removed from the container I poured white wine vinegar (all I had available) over all the affected parts until they stopped hissing.  Once the fizzing and hissing stops that indicates that the alkali has been neutralised.

For situations where acid batteries have leaked then use bicarbonate of soda - bicarb can also be used to stop reflux if you've run out of a proprietary remedy, it is disgusting but better than reflux...**

Even though it wasn't possible to do any further testing until the battery compartment dried out after cleaning I did type the ROMS command.  This machine appears to be chock-full of add-ons, albeit ones it hasn't loaded due to the lost CMOS settings.

The battery compartment with it's payload of unpleasant alkaline residue, like the stuff left after a massive coal-fired party from the last century, is pictured below.  These batteries are dated January 1999.***

The BBC Master would originally have had a rechargeable Lithium battery but that has long since failed, this BBC has been modified to work with non-rechargeable batteries.  The cable connected to the top of the battery pack has had a resistor and a diode inserted in-line in the positive power cable, this is to prevent the BBC Master from being able to recharge non-rechargeable batteries.

To recover and reset the CMOS memory the BBC has to be powered on with the R key held down, then press CTRL F BREAK, then type in these three star commands (each followed by Enter):

*CONFIGURE LANG 12
*CONFIGURE FILE 9
*CONFIGURE MODE 7

Assuming you've also replaced the batteries then when you power it off and back on again it will present the standard BBC BASIC prompt.


* This is a Partridgism.
** Better still, prevent reflux by eating earlier, changing your diet (eat less fat), and getting more exercise.  Partridge, again.
*** Party like it's...


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Day 741, Hissing Model B

It's not the most erudite piece of BASIC coding ever but it shows the machine works.*

After quite some faffing about to get the video working it became apparent that I actually had the right sort of input on one of my monitors.  With a bit of judicious wire poking into the BNC socket on the back of the BBC Model B it released some video, and below is the output.

It was obvious that the PSU on the Model B was suffering slightly so I didn't want to leave it on for too long.  The capacitors were making a high pitched whistling sound indicating that they need replacing, which is to be expected on a machine this age.  I'll replace the capacitors.

As can be seen by the 1770 DFS displayed at boot time it has successfully detected the disk ROM, there are also a couple of disk drives, although I have no disks.  I should have typed the ROMS command in case it hadn't revealed all at startup, that command will list all installed ROM chips.

* Far less rude than the sort of things that used to be displayed on any early 1980's department store computer which they had been foolish enough to allow adolescent boys near unsupervised.  I never did such things myself.

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