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Member postings for Andy Stopford

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

Thread: Barograph 'stiction'
12/05/2022 19:35:48
Posted by David Jupp on 12/05/2022 17:48:42:

I also seem to recall that PTFE gives lower friction if there is at least some moisture (humidity) around - strange given that it was allegedly developed for the space programme...

The space programme thing is a myth - PTFE was discovered (more or less by accident) in the thirties. Its first notable use was in the Manhattan Project to protect the plumbing of the Oak Ridge Gaseous Diffusion Plant from the corrosive effects of Uranium Hexafluoride.

Interesting about the poorer performance for oscillating systems. I wonder if its the same for other slippery plastics like nylon and acetal.

Thread: Emergency Radio Format
03/05/2022 21:24:23
Posted by pgk pgk on 03/05/2022 15:45:01:

This link suggests you have no-where to run:


100 megatonnes? Standard Russian TV propaganda bombast.

The most powerful nuclear weapon ever tested was the Tsar Bomba with a design yield of 100 MT, but reduced to 50 MT to reduce fallout or, some say, because the design team (led by Andrei Sakharov) feared the fireball would extrude out of the earth's atmosphere, and they didn't know what the consequences of this would be.

The Tsar Bomba was a completely impractical willy-waving exercise and modern nuclear weapons have far smaller yields, which isn't to say they're inconsequential - see this link (which has been receiving a lot of visits lately):

Thread: Which Collet Chuck?
29/04/2022 20:12:31

I have a WM180 and an ER32 backplate-mounted collet holder. I have no problems with lack of registration, you can take the assembly off, turn it around, put it back on, and the work remains true. The mating spigot seems very accurately made with absolutely minimal clearance (I recently read that this mounting method is an ISO specification).

The chuck/backplate came from ARC, so no connection between the manufacturers of lathe and chuck, except that they both apparently took note of that ISO spec.

I use it a lot, and I think a MT variety without a through hole would not be nearly as useful.

re. collet chuck accuracy - I do have an ER20 2MT holder (for the mill) which displays considerable run-out - it was a very cheap ebay purchase. I replaced it with one from ARC which is far better (I can't remember the figures off hand, but I think the cheapo one was at least 10x worse).

Thread: Is it really a joke
07/04/2022 20:50:37

There was a chap from National Grid on the radio a few months ago. He said that they weren't worried about increased demands from charging electric vehicles - much of the load (managed by smart chargers/meters) would be in the small hours when other demand was low, and existing infrastructure could easily handle this.

He did say that a widespread switch from gas to electric heating would be more of a problem, and National Grid are working to increase capacity to cope with this when it comes. Improving insulation in domestic properties would presumably help to mitigate this.

Thread: Rumely Oil Pull engine
01/04/2022 20:56:42
Posted by John Rutzen on 01/04/2022 08:32:22:

Hi Jason, no it's a copper fuel pipe and the float is made of copper foil. The fuel in the stainless steel tank seems ok. I wonder if it is reacting with the aluminium float bowl, that seems to be where the gunge was concentrated. Robert, what is fuel stabiliser please?

I think you're very likely right about the float bowl. I would guess that the aluminium corrodes to form aluminium hydroxide gel which is what you found lurking in the carburettor.

re. using octane booster, unless this does something else apart from increasing the octane number, I'm not sure it would help, since the only significance of octane is its anti-knock properties (probably not important with the compression ratio you are using).

The simplest course of action is probably to drain the fuel from tank and carb if laying up the tractor for any period of time, e.g. over winter - I'm sure it wouldn't do any harm leaving it fueled for a few weeks.

Lovely model by the way - it sounds great!

31/03/2022 20:58:08

Ethanol absorbs water which can cause corrosion of aluminium float chambers, etc., so definitely worth draining for storage.

Mind you, old school petrol deteriorated over time too, with the lighter fractions evaporating off (and possibly other chemical changes taking place) leaving an oily, stinky, not very inflammable goo.

Avgas (aeroplane petrol) is reputed not to suffer from this problem, perhaps because its all all 'good stuff' rather than mostly cheap stuff, blended with a small quantity of good stuff. It smells nicer too.

Thread: Why aren't carbide chop saws used?
31/03/2022 20:01:47

I don't know the thickest stock an Evolution saw will cut, but they work amazingly well with very thin sections. I once had to adapt a curtain pole to fit a bay window. It was made of very thin-walled steel tube. I didn't fancy trying to cut the mitres on-site with a hacksaw so I decided to give my then new Evolution saw a try, despite the coarse tooth pitch. There was a fair bit of surplus length in the tube so I was able to do a couple of test cuts first.

I gingerly lowered the blade and it made a perfect burr-free cut - the only thing to watch for was lifting the blade back up while it was still turning - this would result in it catching and putting a little dent in the cut edge.

I should emphasise that the blade was pretty much brand new at the time.

Thread: Rulers - my pet peeve
23/03/2022 20:06:29

Donald, those are Rabone Chesterman No 47 R rules Rotagrip are selling the 600 mm version on ebay:

Thread: Mill DRO X/Y axis + and - on readout
21/03/2022 20:31:45
Posted by mgnbuk on 21/03/2022 20:05:54:

Swapping the A and B channels in the scale plug will reverse the count.

These systems mostly seem to use 9 pin "D" connectors on the scale cables, so not too bad to get in with a soldering iron - always assuming that the manufacturer didn't use crimped on pins !

Nigel B.

I might look into doing that - though I bet they are crimped!

Thread: Advice on Cluttered Dimensions in Drawings
21/03/2022 20:28:52

Ordinate dimensions can help with 'de-cluttering', and work well with a DRO-equipped mill.

Take care though, that you don't do what I did last weekend and read the last hole position as the length dimension of your workpiece. Its exceedingly annoying to find that the last of the numerous holes that you've so carefully, so precisely, drilled lies on that misplaced edge...

Thread: Mill DRO X/Y axis + and - on readout
21/03/2022 19:51:21
Posted by JasonB on 21/03/2022 19:37:15:

Actually if you are going to use the ARC function of a DRO then you do need to get the direction correct.

Y should increase as handwheel turned clockwise just as it does on the handwheel dial

I have this problem - on my mill the only way to mount the X axis DRO is with the scale moving and the pick-up fixed. Vice versa for Y. I can make the display increment or decrement in the correct sense using the setup page, but the displays for ARC and ARRAY are then reversed - it doesn't really matter, you can ignore the pictorial representation and just step through as normal, but it is slightly annoying if you get distracted and forget which step number you did last.

Thread: Milling - first cuts
16/03/2022 21:18:46

And just to make life complicated... climb cutting can sometimes be better, with less vibration and a better surface finish.

This is true even for small mills. I have a Sieg SX1L, which is about as lightweight as you can get, and often climb cut with it. Be cautious at first if you try this, and make sure your gibs are adjusted properly, but not too tight or you won't be able to feel what's going on.

edit: NDIY beat me to it

Edited By Andy Stopford on 16/03/2022 21:19:53

Thread: yet another angle plate
16/03/2022 19:39:56

I've got one of the ones in the second link - the minimum hold down spacing is about 100 mm, maximum about 115. You have to be careful with the length of the studs and nuts, otherwise they foul the table adjusting nuts. Some time I might make a couple of dedicated toe clamps which would put the hold down nuts outside the base of the table.

It is good and rigid.

Thread: Any advance on the highlighted comment ?
14/03/2022 19:35:10

I did quite like the cable crimper - it looks like it works better than some of the (not cheap) ones I've bought.

Think I'll pass on the power hammer though.

Thread: Tomato seed recommendation?
07/03/2022 19:37:06
Posted by Ady1 on 07/03/2022 16:41:03:

Tomatoes seem to be very variable in our climate

The Boss grew them very hit and miss year on year, one year got an amazing monster crop which got turned into a cupboard of chutney.... followed by a disaster crop the following year

All grown in grobags in the same suntrap spot each year

Edited By Ady1 on 07/03/2022 16:43:53

Tomato yield depends on 'Heat Summation': in order for the fruit to develop and ripen satisfactorily, they need a certain number of hours above a certain temperature (the exact figures depend on the variety). I can't have a greenhouse (shared garden) so my toms (and chillies) are at the mercy of the elements. Last year, after a good start, was terrible in the south east with weeks of cold weather and consequent almost complete failure of the tomato crop, and the ones that did ripen were tasteless. The year before was great, and I was giving the things away.

If you're limited to outdoor growing, I've tried and recommend the first three varieties on this page (unfortunately sold out now):

Being early, you have a better chance of sufficient heat summation, and they seem pretty blight resistant. They also don't require pinching out or anything elaborate in the way of training.

There's no problem saving seed from these, use the method described by Dave Halford above, and save at least two separate batches, just in case.

Thread: Cross-slide fixture plate considerations
06/03/2022 19:18:49

I'd suggest drilling and tapping the holes as and when you need them. I've made 'universal' pre-tapped fixture plates in the past, and the holes never seem to be in the right place.

Thread: Greenwashing
02/03/2022 20:41:30

Absolutely Bill!

02/03/2022 20:12:59

And a Henry can survive multiple tumbles down the stairs - try that with the products of James (Winner of the Queen's Award for Hypocrisy) Dyson

Thread: Oops
28/02/2022 19:55:43
Posted by Mark Rand on 28/02/2022 18:53:29:

Yes, ammonium chlorate flux could get "quite exciting". laugh

It might be quite exciting as a coating for licorice sweets too...

Thread: Songs about Engineering
23/02/2022 20:09:25

For a problematic interface between man and machine, how about "The Widowmaker" from "Captain Lockheed and the Starfighters"?

Come to think of it, "Death Trap" by Hawkwind describes mechanical failure

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