Member postings for Colin Whittaker

And the cigar goes to Dave Halford!

The application of a wood working G clamp to the floating 4th foot made a huge difference.

I've now replaced all 4 of the rubber pads/feet (price 50p for a set of 4) and splashed out on some stainless steel nuts and bolts and lock washers to secure each foot to the wall bracket. And now it's really quiet.

The top panel is still vibrating a little and quietens when a damping hand is placed in the middle, so, when the sound deadening foam arrives I'll add some stiffening and foam to the lid and that will be as quiet as I can easily make it.

Thanks again guys.

Clive,

Everything you say makes a lot of sense. Increased mass to lower the resonant frequency and I may as well throw in the foam sheets for good luck.

Thanks, Colin

I've ordered some 3cm thick padding as it's really cheap from China to Thailand.

The machine is a Samsung split AC 1500W power in and 5400W cooling out single phase 220V. It's ancient, a non inverter, and appears to have 4 good rubber feet although one of them is floating.

I guess I could look for some superior rubber feet ...

The only use I've encountered for lead is nuclear shielding of X rays, gamma rays, and high energy neutrons. (Don't get me started on thermal neutron capture cross sections.)

Cheers, Colin

I have a particularly noisy air conditioning compressor cabinet. A fourier analysis of the noise shows (as expected) a fundamental at twice the mains frequency i.e. 100 Hz and strong but diminishing harmonics at 2x 3x 4x etc.

The simplest solution would be to buy some sticky backed acoustic foam of 2cm thickness and apply to every panel that shakes but would this successfully absorb such low frequencies?

Should I instead be looking to add weights to the vibrating panels to move the resonance away from 100 Hz?

Ideas? Experience?

Somebody commented on the liability of autonomous vehicles which reminded me of something that has puzzled me for a while.

Does a driverless car have to be 100% safe (whatever that means)? Or should we be happy if it is just 10% (or better) safer than the average road user?

Is there any chance of us being rational about this?

I have recently bought a slow start relay from China for a central vacuum cleaner. (The original slow start failed and a direct replacement from Europe was perhaps 10 times the price.)

The reason I say this is that if you want an electrical safety cut off that doesn't trigger under the start up current surge then you could consider installing a slow start relay such as this.

Cheers, Colin

This is a very old safety video about what happens when pressure lines and pressure vessels fail. Given that we are unlikely ever to see a boiler explode this is the next best thing with the added benefit of no death, injury or PTSD.

When working on a 3000 psi gas well I would treat them with the greatest of respect but I remember colleagues who seemed to lack the imagination of what would could happen at 100 times a typical car tyre pressure.

Michael,

Thanks, that search link worked,

It appears to be a work in progress. No indication of when it will get back 10+ years though.

Colin

Guys, don't jump on me. I did a site search for Adobe Flash Player and couldn't find any hits.

I'm trying to download the Grasshopper Escapement articles from June 2010 but when I go to open any of the possible Model Engineer copies I get pushed to install Adobe Flash Player, which can't be done.

I can't be the first to be stuck like this so could someone point me towards the appropriate Forum Post?

Thanks, Colin

At a graduate engineer BR management training course some 40+ years ago I encountered an M&E engineer and asked him what kind of coefficient of friction was seen between a locomotive wheel and a rail. He stroked his beard thoughtfully and said, "Well, it normally lies between 0 and 1."

After hauling a bunch of books around in plastics boxes for the last several years I've finally made progress in moving them to bookcases. The reason I feel I can brag here is because of the maths I used to compute the elliptical profile used. Elliptical all the way except at the tips where a constant radius of 50cm was used in order to make gluing a hardwood trim to the plywood shelves possible. The radius of curvature of an ellipse (and hence the point at which it reaches 50cm) needs the 1st and 2nd derivative of the curve and, in my case, a half day rediscovering what I was supposed to know after University. Anyway, here are the pictures ...

One more younger brother to construct and the last of my books will have been decanted!

The BBC will in the near future get rid of transmitters to aerials and expect all viewers to use the broad band network instead saving billions of pounds in maintenance and renewal costs. Progress?

That will need an awfully big reel of optical fibre in the boot of every car,

So now we can go into the pub and order 1/2 a micro acre foot of best bitter (including the head).

12 inches to a foot

3 ft to a yard

22 yds to a chain (and also a cricket pitch)

10 sq chains to an acre

10 chains to a furlong

10 acres to a square furlong

8 furlongs to the mile

1 inch to the mile is 1:63,360

16 oz to a pound

14 pounds to a stone

8 stones to a 100 weight

20 cwt to a ton

not to mention short tons and rods, poles and perches

16 fl oz to a US pint and 20 fl oz to an imperial pint.

2 US pints to a US quart, 2 Imperial pints to an Imperial quart.

4 US quarts to a US gallon, 4 Imperial quarts to an Imperial gallon.

42 US gallons to a barrel

and my favourite ...

1 British Thermal Unit = energy needed to raise 1 US pint of water by 1 degF

Are the people who want a return to imperial measurements smart enough to use them?

P.S. There must be a typo above. Please excuse it.

Edited By Colin Whittaker on 18/09/2021 04:55:18

While training at an engineering technical centre outside Alexandria in the early 1980s I learned the Egyptian approach to breakdowns.

1/ Breakdown. Pull over to side of road.

2/ Warning to approaching motorists. Scout around for the biggest boulder you can lift and place it around 10m behind the car and far enough into the road to make approaching cars swerve away from you.

3/ Change tyre or whatever.

4/ Remember how heavy the boulder was and mutter in arabic, "mallesh". (In English, "Ah **** it." )

5/ Leave the warning boulder where you'd placed it and drive off.

Driving at night on unlit roads and facing dazzling headlights made you good at detecting shadows on the road and steering around them. When you failed to see the boulder and wiped out a front tyre it was truly amazing how quickly 4 engineers could change a wheel in the dark.

Edited By Colin Whittaker on 10/09/2021 05:28:46

Edited By Colin Whittaker on 10/09/2021 05:29:29

Edited By Colin Whittaker on 10/09/2021 05:30:10

Edited By JasonB on 10/09/2021 06:59:13

At my old company a nuclear logging expert was giving a presentation in South America to an oil company on the accuracy and precision of a downhole measuring instrument. The prentation employed a simultaneous translation into Spanish but was not well received with lots of bored and/or bemused faces.

A post mortem revealed that the simultaneous translator was using the same Spanish expression for both precision and accuracy!

I have some experience of using a remagnetiser ...

It had a gapped square iron framework where the gap was bridged by the magnet and matching pole pieces for the individual magnet. The cross section of iron framework was at least double that of the target magnet.

Around the framework was wound a pair of huge coils that could be connected in parallel or series for 110V or 220V operations.

A push button switch connected the mains power to a bridge rectifier follwed by a DC ammeter and the two coils.

When the button was pushed the current slowly (over a few seconds) rose until a maximum was observed and the button released.

Tired old magnets were revitalised to (in my estimate) 2 or 3 times their previous strength.

Commercially speaking, we found this old piece of junk, fixed it up for a few 10s of dollars, used it on every permanent magnet in our Western Desert base and then returned it to its hiding place under a bench. We had a serial number of 00006 riveted to the base plate of the device while the company had >100 bases worldwide. I had never seen a magnetiser before nor did I ever see one again.

Martin,

Thanks for clarifying.

Michael,

Integrating the EoT is interesting. My initial plan is for a correction plate and a manual correction but the EoT shadow plates or spindles do look elegant.

Colin

So I can't use a wooden former to bend the brass to.

I've got to use a set of rollers. That sounds like aother project before I can start.

Thanks for pointing that out Martin.

Colin

So ...

1) trial bend

2) then check radius

3) then engrave a new one

4) then rebend and hope to achieve the same radius

Thanks all.