Today I replaced the extractor fan in the downstairs toilet.  It has a timer, selected by sucessive pressing of a push switch. The delay off timer starts when exiting the WC. – settings are 30 seconds, 5 minutes, 10, 20,30mins.  All very clever, but I would have liked a variable resistor so that I could choose anywhere between zero to 30 mins.  Surely that would have been cheaper than the logic, eerom and an LED array to show what you had selected.

Is it a case of over engineering ??

Bob

Bit of a delay but castings cleaned up and nice and square ready for detail work.

Odd piece of random uselessness by the internet..

Hi, a few weeks ago, one of my sisters lent me a load of paperwork that he did during his time in the RAF during WW2, he was a Leading Aircraftman, and was posted in Iceland. So I’ve been scanning some now and again, and found this small note that may interest some.

I’ve no idea if you can get any of these salts these days, or if anyone would do such an exercise, but it might be interesting to know if it is.

Regards Nick.

On 9 February 2026 at 14:43 Nicholas Farr Said:

Hi, a few weeks ago, one of my sisters lent me a load of paperwork that he did during his time in the RAF during WW2, he was a Leading Aircraftman, and was posted in Iceland. So I’ve been scanning some now and again, and found this small note that may interest some.

I’ve no idea if you can get any of these salts these days, or if anyone would do such an exercise, but it might be interesting to know if it is.

Regards Nick.

Don’t think you would be able to buy sodium nitrate or potassium nitrate without a special licence these days as both can be used to make gunpowder and other explosives.

Hi, well Nitriding can be done on low carbon steels, as well as a few other metals. It is in fact a case hardening process. I remember seeing a film about it during my tech college lectures, where they were doing a large gear ring, there were a number of gas burners around the ring, playing flames onto it, and when it reached the required temperature, Nitrogen gas in the most part was applied to to it.

Nitriding process

Regards Nick.

I have just finished one of those “Please can you fix this?” jobs. My sister’s trolley affair that she uses for shopping – one of those things with rotatably-mounted groups of three wheels each side – had broken where one of the axles had smashed through the plastic fork on one side. I wasn’t too difficult to cut off the axle (Dremel), and turn up a new stainless steel axle that fitted the much-enlarged hole on one side of the forks. The wheel was reamed 7/32″ too, to suit the new axle. Rather than riveting it up as per the others, I shoved on an M5 thread and fitted a Nyloc nut and washer.

Job done? Perhaps not… those other wheels were all rather wobbly and as a result, the tyres had begun to cut through the forks. Better open up the axle holes in the wheels and fit larger axles, a nice fit on the wheel to cure the wobble. It didn’t take too long. At least they all look alike now with Nyloc nuts!

I should have left it at that. My biggest blunder was to then start shaking my head at the wobbliness of the 3-wheel assemblies on their central axle. Surely I could remove them and re-bush them? I wish I hadn’t. There was a bop-on plastic hubcap securing the assembly, which did eventually yield to persuasion and came off, fortunately undamaged. With the sub-assembly of three wheels in my hands, I thought I’d remove the steel bush affair on the inside of the thing. I tried to remove it, but too late I discovered that it wasn’t a bush but an extremely scabby, worn and ill-fitting ball bearing. By this time I’d wrecked it even as a scabby bearing, so it had to come out. It wasn’t easy; I eventually got the inner race and balls out, then found that the outer race seemed to be moulded into the plastic fork. No way could it simply be pulled or driven out! Fortunately I had a suitable bearing in stock, so I bored the plastic wheel and also removed the remains of the outer race to fit the new bearing. I fitted a brass bush as an outer wheel bearing, a good fit on the existing axle and then fitted it all together. Result!

No, I am leaving the other wheel sub-assembly firmly alone – they’re wobbly, but they can stay that way!

The perils of trying to repair things that clearly are not meant to be taken apart! Ah, well; I’ll have earned some Brownie points from my sister – but what will she have me mending next?

Not engineering related, but I feel the need for a grouch. Got dragged to IKEA, fully intending to buy a bathroom cabinet. Long before I’d tramped round and round to get to that bit I’d lost the will to live,  so I just found  short cut to the exit. I’ll pay a bit more in a normal shop where I can just go straight to what I want.

Same problem with supermarkets who move stuff around in the hope you’ll impulse buy something in your search. No if I can’t find it where it used to be I’ll manage without. Told the manager at my local Sainsbury’s but he didn’t seem interested. No wonder Internet shopping is taking over.

On 9 February 2026 at 17:04 Andrew Crow Said:

On 9 February 2026 at 14:43 Nicholas Farr Said:

Hi, a few weeks ago, one of my sisters lent me a load of paperwork that he did during his time in the RAF during WW2, he was a Leading Aircraftman, and was posted in Iceland. So I’ve been scanning some now and again, and found this small note that may interest some.

I’ve no idea if you can get any of these salts these days, or if anyone would do such an exercise, but it might be interesting to know if it is.

Regards Nick.

Don’t think you would be able to buy sodium nitrate or potassium nitrate without a special licence these days as both can be used to make gunpowder and other explosives.

Potassium nitrate is available from Amazon.co.uk

Well, a bit of a few “Todays”…..

Two workshop equipment projects under way:

1) I built the overhead-crane “crab” (the cross-travel truck carrying the hoist itself) with a cross-bar held in keyhole slots in two parallel plates, to suspend a commercial chain-hoist – but also so the cross-bar alone could form the static axle for the top sheaves of a rope block-and-tackle. So it is easy to lift out to thread the pulleys on.

Chain hoists are great for risking yards of hefty steel chain clattering about all over the work, catching on fittings, chipping paintwork, bending things…

Also my workshop is of very limited headroom. It’s only a glorified garden shed, albeit built of concrete blocks, with a gently-sloping roof and ceiling.

So after a little finishing work, the crab will also have a smaller version of the chain-block suspension, for the upper of a pair of 2-sheave blocks (“Screwfix” items) taking 6mm cord, giving a 4-fall rope tackle that will handle the bulk of the crane’s duties.

The blocks being small and their mounting in the frame higher, will also increase the headroom by some inches, at full height – i.e. “chock-a-block”. (Yes, that is the colloquialism’s original, maritime meaning.)

…

2) A trip to Bridport, no not to the Foundry but to Townsend Bearings at t’other end of town; to purchase pillow-blocks and a pulley for the belt drive for the Denbigh horizontal mill undergoing re-commissioning. These plus other parts are now on a picnic-table in the dining-room so I can “design” the framing to hold it all.

I have two fairly “powerful” worm-gears that were candidates for the massive speed reduction necessary, around 1350 : 70 rpm, but experimenting showed this route not really viable.

First stab at a replacement tray for 1/4″- 3/8″ socket set.  Big print head crash after about 7 hours of printing.  The printer lost the “Z” reference and no amount of resetting would sort it out.  Finished by doing a reset to Factory setting.

It needs a few dimension changes and will have another go perhaps tomorrow.