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Member postings for Colin Whittaker

Here is a list of all the postings Colin Whittaker has made in our forums. Click on a thread name to jump to the thread.

Thread: BB22 Headstock Lathe Bearing
09/05/2022 03:52:06

Ketan,

Thought I'd let you know ...

My son finally chivvied me into stripping down the lathe and replacing the bearings.

The bearings were the sizes you advised.

After reassembling the lathe the headstock shake is reduced but still detectable. This seems to be because there is no way to adjust the preload. I'm now waiting for some bearing shims to arrive.

Thanks again for you assistance.

Colin

Thread: Time to Say Goodbye
09/05/2022 03:43:48

An archive that can't be viewed because of obsolete software to view.

No online editions of MEW and ME for months.

And now a reminder that my subscription is expiring!

I've taken that as a reminder to cancel my direct debits.

Ant ideas for a replacement home engineering subscription?

In sorrow, Colin

Thread: What's happened to the last few month's magazines?
26/04/2022 13:10:16

I can see copies of the Model Engineers' Workshop I'm missing on Pocket Mags but none here. Am I doing something wrong or has the MEW a new online home?

Thanks, Colin

Thread: Imperial v Metric Measures
09/04/2022 04:22:35

sorry 20cm is 8" give or take, I asked for 8 inches.

Edited By Colin Whittaker on 09/04/2022 04:23:54

09/04/2022 01:53:55

I went to my local wood shop in Phuket Thailand.

I'd like some 2cm thick planks says I. She pulls out a ruler squints and says OK 3/4 of an inch.

Right thinks I that makes my 20cm wide plank 6 inches. By 6 inches wide says I.

Out with the ruler again and she says that's 20cm.

I give her a funny look and say 2.5m long? Success!

It's a weird mish mash of length units out here. But the hard wood is very cheap and very pretty when stained/varnished.

Colin

Thread: Acoustic Damping/Attenuation
12/03/2022 01:10:28

Follow up from killing the noise ...

The black foam tiles arrived and were glued in place. Result? The noise got worse!

So with the help of my son I removed all the panels and finally gained a view of the compressor and its rubber shock mounting feet.

perished shock absorber.jpg

The one on the left is obviously the before and the one on the right the after. The after was purchased in Phuket town where a set of 3 cost approx. 2 GBP.

With three new feet the air conditioner is much quieter, probably as quiet as when it was installed 7 years ago.

Now, this is the tropics and the air conditioner has been working hard with a compressor that gets unpleasantly hot to the touch but does 7 years seem like a reasonable life for a rubber shock mounting? It is less than I would have expected.

Thread: Songs about Engineering
24/02/2022 06:51:42

An engineer told me before he died

as learned at the UK's foremost engineering university in the late 70's

Edited By Colin Whittaker on 24/02/2022 06:52:54

Thread: Acoustic Damping/Attenuation
19/02/2022 01:52:32
Posted by Dave Halford on 15/02/2022 12:27:53:
Posted by Colin Whittaker on 15/02/2022 04:21:10:

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 ...

Cheers, Colin

I suspect fixing the 4th foot mount down to something solid to start with will make a fair difference.

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.

15/02/2022 10:42:54
Posted by Clive Foster on 15/02/2022 09:31:14:

Fix depends on whether the sound is being transmitted through the panels and vents or comes via excitation of vibration modes in the sheet metal panels.

Acoustic foam and similar absorbing / deadening materials are good for direct air transmission through vents and panels as they reduce the energy bouncing around in the air inside the cabinet before it can escape.

Panel vibration modes need the panel stiffened to prevent it shaking. Although lead sheet is the traditional way pretty much anything reasonably stiff will do. Lead works primarily by adding mass so iut takes much more energy to excite the panel and, usually, alters the frequency response. Biggest advantage is that a thin layer makes a decent difference. Direct stiffening by gluing a layer of plywood or similar works fine but does need to be thicker. Couple of inches of rigid foam sheet combines both strategies and is effective but usually the thickness needed cant be accommodated.

Rubber feet and similar mounts are primarily to reduce coupling into the structure that the unit is standing on. Structural coupling can give vey unexpected effects.

A few months back I moved my hydrovane compressor from the hutch outside into the sectioned off garden shed part of the workshop building and hit a resonance. Despite still being on the same concrete slab. Probably due to the sectioning wall being only single skin chipboard. Fixed by standing on a pallet style structure. The wood sections and joints absorbed the vibration before it got to the floor. Old tyres laid flat on the floor with a plywood top for the offending unit to stand on are really good at this job but hardly practical for your situation. Small pallet style base sitting on a carpet off-cut could probably be made aesthetically acceptable if structural coupling is the issue.

Clive

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

15/02/2022 04:21:10

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

15/02/2022 02:21:31

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?

Thread: New highway code rule.
06/02/2022 00:52:25

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?

Thread: Motor protection
04/02/2022 00:35:10

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

Thread: Catastrophic Failure of Pressure Vessels
14/01/2022 05:12:44

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.

Thread: Adobe Flash Player
08/11/2021 12:34:13

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

08/11/2021 12:11:52

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

Thread: A question about traction.
29/10/2021 12:04:29

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."

Thread: What Did You Do Today 2021
29/10/2021 11:57:00

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 ...

img_20211020_194138_8.jpg

img_20211024_141438_4.jpg

img_20211024_182315_2 (1).jpg

img_20211024_182235_2.jpg

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

Thread: SKY abandoning their satellite customers
11/10/2021 11:18:50

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,

Thread: Back to Imperial
20/09/2021 15:06:39

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

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