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Member postings for SillyOldDuffer

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

Thread: Cost of deliveries
13/12/2018 20:11:30
Posted by Jon on 13/12/2018 18:17:56:
Posted by Neil Wyatt on 12/12/2018 12:08:38:
Posted by Jon on 11/12/2018 22:05:54:


But then you make the item unappealing to UK buyers, who are the most likely market.


True in one sense as we dont produce anything any more.



This is a common misconception and I doubt anything I say will change opinions. However the value of UK manufacturing is worth proportionally slightly more than it was in the golden age. In 2017 about £400Bn.

I think people believe UK manufacturing has disappeared because visibility has dropped and large numbers of jobs have gone. Modern manufacturing is often low-key. It's done by small numbers of people in relatively small nondescript units tucked away on business parks. It tends to be very mechanised and to be making high value products. In comparison, in the recent past British industry was high profile and very, very obvious: coal mines, smoke stacks, cranes, shipbuilding, iron ore, heavy chemicals, steel works, slag heaps, quarries, railways, factories, foundries, potteries, busy ports etc. Lots of labour intensive activity providing plenty of skilled and semi-skilled jobs. Good jobs too.

Trouble is much of this obvious industrial activity gradually came to be both inefficient and low-value. Times change. You do not get rich in 2018 doing basic engineering! And it is very dangerous to compete using out-dated methods with anyone operating modern plant with low cost labour. British industry had to change and it did. Successfully.

I can't defend the way it was done. Lot's of people got badly hurt in the process. All too often the change was done brutally, incompetently, or even maliciously.

Me too. If anyone out there is prepared to pay 1970 staff shortage rates for an ex-COBOL programmer let me know...

Despite appearances it's not true we've become a nation of hairdressers!




Edited By SillyOldDuffer on 13/12/2018 20:20:00

Thread: Mini-Lathe Repair
13/12/2018 15:17:15
Posted by Ron Laden on 13/12/2018 09:55:28:


The motor was around 10 degrees or more off the horizontal when mounted with the belt riding to one side of the motor pulley.



A fair wallop of force would have been applied to the motor via the belt in the short time before the plastic teeth in the gearbox broke. The crash might well have pulled the motor sideways. The mounting bolts allow movement for alignment purposes and aren't designed to hold strong sideways forces. Likely a good thing: if the motor hadn't turned on the mounting you might have bent the axle or put a ding inside one or more bearings. Shock loads can do surprising damage.

A slight worry about fitting metal gears is answering the 'what breaks instead' question. 3D-CAD packages often have force modelling capability. Anyone know if it's possible to model the forces experienced by a crashing mini-lathe with one of them? Could it be done in Alibre Atom3d?



Edited By SillyOldDuffer on 13/12/2018 15:18:18

Thread: Sourcing
13/12/2018 13:00:25
Posted by Paul Kemp on 11/12/2018 23:38:53:
Posted by Jim Nic on 11/12/2018 21:28:29:

... however can you ever be really sure what you are getting? Even if the supplier gives you a copy certificate unless the plate or bar is stamped you still can't be 100% sure!


You can never be 100% sure about anything. Aerospace and Defence both put far more effort into getting the specified product and even they get caught sometimes. There was a major counterfeit aircraft parts scandal a few years back in the US where dud parts were found fitted to Air Force One.

By volume most counterfeit products are made in China - at the moment. But it's a world-wide problem. Counterfeiting tends to be associated with developing countries where regulation is slack and people prepared to take risks, and a quick buck is more tempting than building reputation : before about 1920 the USA was a major offender, Belgium and Birmingham(UK) once had bad reputations, Germany, Taiwan, Russia, Japan and many others. What all these countries have found is that counterfeiting is poor economics - you make more money by selling decent stuff than cheap suspicious. What happens over time is that economies tend to move up-market. It doesn't eliminate counterfeiting because there's always somewhere else making a start in manufacturing.

Bad though they are for making the junk in the first place it's too easy to blame China. Making counterfeit parts isn't very profitable. The big money is made by the people who enable these products to enter the local supply chain. Criminals. Think horse-meat in lasagne, not a chinaman in sight, and no-one went to jail...

The UK's latest financial scandal should probably be of more concern to forum members. After a 3 year battle to get information out of the industry a report has just been issued showing that overcharging reduces the value of some UK pensions by up to a third, though 20% seems more typical. It is almost impossible for individuals to find out what charges they are paying, but it appears that the industry has set up a multi-layered service management structure where each player takes a cut on every transaction. The extra complexity and costs do not appear to be justified. Consequently UK pensions are far more expensive than the same schemes in, for example, Holland. As the scale of the problem is much bigger than PPI, I expect every call-centre between Salford and Manilla will ringing me up offering help for the next 20 years. And I might well need it.



13/12/2018 10:18:51

Easier to say what to avoid than to identify sources of cheap metal that's worth having! DIY Store metal is not only expensive, it machines badly - apart from the Brass. Modern manufacturing often uses alloys chosen for properties other than machineability, so turning scrap on a lathe can be utterly miserable. Or it might be wonderful. As a begineer this uncertainty caused me severe difficulties. Had a bought a crap lathe? Had I bought crap tools? Was I setting the rpm wrong? Was the depth of cut or the feed-rate wrong?

I strongly recommend learning to use a lathe with known materials. It's worth finding an online or local supplier and investing some moderately serious dosh on some mild-steel, some free-turning mild steel, some brass, and an Aluminium alloy intended for machining. (Pure Aluminium and many alloys are gummy.)

Once you know how the real thing behaves it's much easier to tell if a bit of scrap is causing problems. Later, once you know what to expect, even a little experience makes it much less risky to approach a scrapyard or other source of unknown metal. Otherwise you can waste a lot of time struggling with bad metal - you can guess how I know!

How approachable your local scrappies and manufacturers are seems to vary wildly. My local scrapyards are all surrounded by barbed wire and are much more interested in buying metal than selling it. Not much manufacturing where I live, and the two firms I approached both refused. I wasn't surprised - my employer operated a policy whereby it was a zero-tolerance sacking offence for employees to take scrap. The reason is that it makes it easier to prove theft: it's not unknown for scallywags to "accidentally" convert new stock into scrap for the purpose of nicking it. When caught with a boot full of metal, the zero-tolerance policy makes it no defence to claim 'foreman said it was OK in 1973'

But it's worth enquiring - if you don't ask you won't get.

90% of what I do is done with new metal...




Edited By SillyOldDuffer on 13/12/2018 10:22:52

Thread: It's not rocket science
12/12/2018 18:52:53

Never saw Scotty using a mole grip. I expect the Starship Enterprise was made of tinfoil too!

Edited By SillyOldDuffer on 12/12/2018 18:53:35

Thread: Cost of deliveries
12/12/2018 18:46:07
Posted by larry phelan 1 on 12/12/2018 17:44:11:

No shorts and bare feet here on Christmas day,let me tell you !


Lucky you - I never get invited to that kind of party!


Thread: Squaring in the lathe
12/12/2018 17:36:21
Posted by J BENNETT 1 on 12/12/2018 17:14:07:

Can any one explain why lathes turn very slightly concave? I have observed this phenomena but could never work out why it happened. I am also intrigued by the suggestion that they are designed to do this. Please enlighten me!

It's because turning in the slightest bit convex means the resulting face cannot sit flat, whereas a concave surface will. Given that it's impossible to get and keep lathes exactly at 90 degrees through life, it's safer to deliberately allow a small concave error.


Thread: New Lathe Tooling
12/12/2018 17:27:57
Posted by Terry Kirkup on 12/12/2018 16:43:16:


JB1, thank you too. Warco may well not touch the thing between it arriving in Surrey and ending up in my garage but they have at least seen inside the box as that's where they stuck my milling slide and vise, ...

... where I was unpleasantly surprised to discover my concrete pads are 60mm too far apart! ... I suppose I can let that much of the tailstock pedestal stand on a few inches of the flooring which is 20mm tongue & groove with half inch ply on top of that, the rest secure on the concrete.


My impression is that Warco open the case and run the lathe, probably very briefly, on the pallet. It would be easy enough to check the main functions are OK (motor starts/reverses, speed control, spindle turns, power traverses works, hand controls etc.) . I'd suggest Terry does similar superficial tests before fully unpacking in the unlikely case there's a problem and it has to go back. I don't think Warco get Dr Schlesinger out of the deep freeze to check all his limits.

Re flooring I strongly recommend supporting the tailstock end properly before installing the machine. The lathe may look like the rock of Gibraltar but the bed is surprisingly bendy when you put a DTI on it. Any twist will effect the accuracy, and vibration will cause poor finish. It's well worth making sure the lathe is properly supported at both ends.

Sorry to hear you have flu! I expect it's a computer virus...


Thread: Cost of deliveries
12/12/2018 10:48:54

Years ago my dad had a job that often took him to the US. A colleague needed some replacement parts for his 1960s Chrysler and - to save carriage costs - asked dad to buy them in the US and bring them back as hand-luggage. He had bother finding the parts, manhandling them on to the plane, and then back to his car.

Back in the UK he presented the bill. 'Good god!' said the ingrate 'this is more expensive than the dealer in Chippenham.' After that dad stopped doing favours!

Dunno if it's still true but the Aussies I worked c.2000 with were shocked to find good Australian Wines about half price in the UK compared with Australia.

There is no such thing as common sense...


Edited By SillyOldDuffer on 12/12/2018 10:49:16

Thread: If you bought this lathe what would you do?
12/12/2018 10:18:49

I agree Men Ifr needs to have a conversation with Chester but I'm not sure he's played his cards well.

The lathe has a number of faults that should have been noticed during first inspection. It has other faults, like the stuck half-nuts, that become obvious as soon as the lathe is operated. Assuming it's new I would have rung Chester almost immediately. Judging by past experience, Chester would simply have exchanged it.

When a new lathe is found to have trivial faults that can be easily fixed at home, I'm all for minor DIY repairs. But it's not a good idea to strip machines down and go looking for trouble. Dismantling a new machine will void the warranty, and Men Ifr now depends entirely on Chester's good will rather than his discarded legal rights.

From Chester's point of view, it would be a concern that a mill has been 'improved' slightly unwisely by the same owner. They would want to avoid the sort of extremist customer who wants to dismantle and return machines until he finds the one he wants!  (I'm not suggesting that Men Ifr is that sort, only that it might look that way.)

If I was Chester, or any other business faced with this complaint, I would remove the machine, give the customer a full refund, and decline to sell him another one. Not because I'm in business to dodge responsibility, but because it's not worth the hassle of dealing with customers who ignore the Terms and Conditions.

There are five ways of buying hobby machine tools. You pays yer money and takes yer chances:

  1. Buy a new high-end lathe from a 'quality' maker. This greatly increases your chances of the purchase being trouble free but expect to pay 6 to 15 times the cost of a similar Far Eastern machine. Very few hobbyists put their money where their mouth is by buying this way!
  2. Buy a new Far Eastern machine from an established UK supplier. Do not expect an immaculate tool-room lathe! Rather, you are buying a year's solid protection during which time a dud can be replaced, or your money refunded. You are financially protected, not given a guarantee that the machine will be perfect.
  3. Buy a new Far Eastern machine from an unknown vendor. Good way of getting a bargain at risk of considerably more trouble if you get a dud. Even if you get your money back, it's likely that you will have to pay to return the machine.
  4. Buy a second-hand high-end machine from a dealer. This de-risks your chance of buying a dud by providing a thin layer of consumer protection and a limited warranty. Dealers with a reputation to protect add considerable value to the transaction because they know what to look for in pre-used machinery, and are likely to be honest about condition. The down side is cost - the dealer has overheads and he has to make a living. And there are always a few rogues about in any trade!
  5. Buy second-hand privately. Cheapest way to buy expensive kit but you are on your own if things go wrong!

I don't see any harm in buying a new Chinese machine with the intent of stripping it and making everything wonderful. But don't expect to change your mind half-way through and expect to make a warranty claim!

My approach to new machines is rather different - provided it works I don't care much about minor imperfections. After a visual inspection, I put the machine through it's paces - I would rather worry about faults that matter in practice than blemishes. So far I haven't found much wrong that mattered. Whilst Far Eastern kit suits what I do very well it's not for everyone. Others enjoy owning and using expensive tools in perfect condition; buying Far Eastern is unlikely to make them happy, even if the machine is fully functional.

I hope Men Ifr gets a quick resolution to his problems and is able to get back to having fun!



Edited By SillyOldDuffer on 12/12/2018 10:27:56

Thread: Cost of deliveries
11/12/2018 22:23:35
Posted by larry phelan 1 on 11/12/2018 20:06:57:

Came across a post here regarding the high cost of deliveries from England to anywhere else,often much more than the cost of the items involved.


Strange to say,not all suppliers seem to be bound by this creed,very odd !


It's beyond me exactly how it works but there's an International arrangement organised by the Universal Postal Union that allows postal authorities worldwide to recover the delivery cost of items received from abroad.

The system is gob-smackingly complicated and the rules are written in legalese. Recovery costs are paid in a currency called SDR (Special Drawing Rights operated by the IMF), which is referenced to the US Dollar from the daily rates of a basket of currencies consisting of the US Dollar, Euro, Pound Sterling, Renminbi and Yen.

Then different rates are applied to developed economies and undeveloped economies. Undeveloped economies pay less to encourage growth, but everyone is gradually moving the higher group. Movements between groups take place in a 5 year cycle. Bottom line - you tend to see higher charges between countries like the USA and Australia, than say Australia and Thailand.

Another reason for high or low costs is the way post is moved. I believe everything posted between the US and UK travels by air, which is top-rate. Heavy items can individually shipped but this is also expensive. Much of the stuff we receive from China travels at the lowest possible rate - in bulk in shipping containers. It is possible to reduce charges by routing goods via third party countries, but I'm not sure it's entirely legal.

More costs arise each time an item crosses a border. Inside the EU there many are opportunities to reduce costs because the countries involved can operate as a single unit with lorries moving freely over long distances. Not quite so easy to economise within the EU when items have to be delivered across a sea-way to the UK and Ireland, but generally UK - Germany will be cheaper than UK-USA.

Mixed in with this are the commercial carriers, with whatever rates they care to apply. Depending on capacity and commercial considerations some rates are loss leading, others profit taking.

It also seems that the big guys can use their financial muscle to get preferable rates based on volume. It's possible for the small guy to to get cheap rates too but he has to sort out the details for himself, and his time costs make searching expensive. If you buy from someone who doesn't have an existing arrangement, or someone who isn't prepared to look for the best rate on a case by case basis, you're liable to pay over the odds.

Not sure this is anything like a proper explanation. What's charged for the same item can vary over an incredible range. Strong suspicion that some ebay sellers make their money out of post and packing, not what's in the parcel.

It's another mess! Brexit makes it more unpredictable.


Thread: Warco WM 280V Variable Speed Lathe With AC Motor Inverter Drive
11/12/2018 18:11:14

Pleased with mine. Decent amount of grunt (1500W) and able to handle largish jobs as well as small ones. (The lathe is bigger than a Super 7). Power traverse for facing as well as normal cuts is a boon. Runs at full speed in forward and reverse. Main objection is it's a bit noisy - two cooling fans running continuously, with metal gear clatter when it's running. Not unreasonably noisy in a workshop, but loud enough to just stop me listening to a radio at normal volume.

The built-in 3-speed gearbox isn't as useful as I expected when threading. I usually find that the next thread needed requires change-gears to be moved, rather than being in gear selector range. The banjo is the straightforward type and easier to set-up than that on a mini-lathe. Belt change between high and low speed ranges also easy provided you can get at the right-hand side of the lathe.

Worked out of the box and only required a mild clean-up. After 4 years only one fault, a loose wire on the contactor. In very cold weather the computer type cooling fan on the VFD sometimes rubs on first start-up, but it's no where near worth fixing (yet). Finish under the tailstock a bit rough but OK where it matters.

One problem with owning a lathe with a few convenience features like the 3-speed gearbox is that I would like more of them. A clutch would be nice...

Not seen a lot of complaints about quality issues on this particular model.


Thread: Soldering
11/12/2018 16:05:56

My only qualification for offering suggestions is that I had trouble too. There are a few things to get right and it pays to tick all the boxes. I think silver soldering and brazing is much easier to do when you have plenty of heat from a powerful torch. I make do with the cartridge kind, but they are relatively limited.

It's easy to use the wrong sort of firebrick for the hearth. There's a type designed to soak up and retain heat. Heavy, dark and solid. Mine came from a night storage heater. They resist flame extremely well but you probably don't want to use them because they can eat all the heat a small blowlamp can throw at them. Only after you've fully heated a hearth made of these can you start soldering! The other type of firebrick is intended to insulate. Various materials, but typically light weight, whitish and soft. They reflect rather than absorb heat so more of it concentrates on the metal.

To maximise heat from a smallish torch, I find it best to shield the job inside a kind of insulating oven structure made of insulating firebrick with an insulating floor. It has front and side walls and a bit of a roof, leaving just enough access to comfortably access the job. Nothing special or permanent about it - a few loose insulating bricks arranged to suit. You need a lot more heat on an open hearth than a shielded one.

Flux, metal and solder all have to be compatible - see CuP Alloys advice. Flux moistened rather than wet.

In my experience small DIY blowlamps are a bit underpowered for your lump of metal, but I've used the next size up successfully on that size.  I experimented with two small torches and found it didn't help - time wasted faffing with two heat sources spoiled the joint. Someone more skilled might have done better. Butane torches produce more heat than propane.

Practice, practice...

Another mistake I made was not setting the hearth up so it was comfortable to work with. To reduce the fire risk and shelter the flame I built it low and had to sit on the floor to use it. Not smart. I did far better set up outside at waist height on a still day with plenty of room and no distractions. Getting hot quickly and applying solder at just the right moment is important - no dithering. When soldering works properly it's easy. With limited equipment and skills it can be a pig.



Edited By SillyOldDuffer on 11/12/2018 16:07:48

11/12/2018 13:10:56

Iain's photo looks very like my early attempts. The cause in my case was insufficient heat coupled with taking so long trying to get a flow that the flux went off. I don't think my inexperienced technique helped either - I was distinctly sluggish!

I'm still not very good at silver soldering but buying a bigger torch and arranging insulating bricks around the job to keep the heat in made it a lot easier!


Thread: Vertical milling attachment vs combo lathe/mill??
11/12/2018 12:59:00

I agree with all the negative comments about milling vices and combination machines. Both are very constricting compared with separates. But both are useful if you are short of space and can put up with being restricted to light milling on smallish objects only. It's amazing what can be achieved on limited kit by determined operators with imagination and skill. My advice is buy a combo if you are short of space, never buy one to save money.

On the subject of threading, it's true that a minimum speed of 150 rpm is awkwardly high for threading under power, though it's not such a problem if you use carbide inserts and run the lathe in reverse. Most Chinese lathes can do this.

Another good alternative if you're not doing loads of thread cutting, is to make a hand-crank to grip inside the spindle so you can turn the lathe by hand. A hand-crank gives total control and - as long as you haven't got several long threads to cut - it's not seriously tiring. The downside is threading takes longer, but if you only need to cut a few threads every so often and aren't in a hurry, it does a perfectly good job. It's also less stressful because no way will you crash the saddle into the chuck and break something! Worth knowing also that most small threads are cut with taps and dies; lathes are usually reserved for big diameters and/or unusual threads.


Thread: Baldor Bench Grinder wont get to speed
11/12/2018 12:08:23

In addition to NDIY's suggestions:

That the motor starts and runs at all implies that the start Capacitor is OK

Slow running can be caused by shorted windings - if so they convert your nice old Baldor into an expensive old Baldor! Cure with new motor or a rewind ( £ ) .

Another common cause of slow running is a faulty centrifugal switch. They can fail mechanically or the contacts can stick and may be fixable. (It's a nice Baldor after all!) This photo pinched off Quora is an example of what to look for inside the motor. When the motor is spinning fast enough part marked P on the rotor operates the switch marked S. What the switch does depends on the exact type of motor you have. It might just disconnect a winding, or it might switch in a Run Capacitor. The Run capacitor (if you have one) could be faulty, an easy fix.


There a few guys on the forum who know far more about motors than me and their answers are worth waiting for. In the meantime are you able to put some photos up?


Edit: What I want for x-mas.  An unwanted smiley exterminator. sad

Edited By SillyOldDuffer on 11/12/2018 12:09:53

Thread: Source of Aluminium Lined Plastic Water Pipe?
11/12/2018 10:35:18

Morning Joe,

What fun - in these days of globalisation it's odd to run into trouble finding a commonplace item like pipe. For some reason that particular type hasn't caught on in the UK. Plug-in plastic plumbing, no problem, but not if you insist on an Aluminium barrier. The main use of aluminium here seems to be underfloor heating and brownfield protection, both a little expensive.

I would never have guessed that a site 40m away from the sea would be a poor HF location. But, like here, the main problem is noisy neighbours!

Interested to read why you abandoned your transmit loop. They're not miracle workers and I'd much prefer a wire antenna if possible. A friend tried a magnetic loop with much the same results as you. He had most success receiving on the loop while transmitting with a low dipole. But he soon got fed up having to turn the loop to get the best signal to noise ratio for each and every contact!

For broadband receive up to four untuned loops can be connected to this LZ1AQ broadband amplifier making an active antenna. (other makes available). A description of how it works with various loop configurations in this pdf. It has some chance of solving my receive noise problem by only reacting to the magnetic part of the wave, by being well-balanced, and because I might be able to null out the worst local noise. As you know there's a great deal of untrustworthy antenna lore about. I hope this approach will work for me, but don't be too surprised if I report failure in a week or two!

One reason I bought the KiwiSDR is that it displays on a web browser and can be accessed over the internet. As the other home-owners in my family have better locations than me, it might be possible to operate with a remote receiver. Not quite sure how I shall persuade them to fill their gardens with poles and wire...

Thanks for the offer of a vacuum capacitor - that's extremely generous! Can I hold fire on that until I decide to build a transmit loop? I wouldn't want to sit on a hard-to-get component like that unless I was definitely going to make good use of it!

A tower is the best technical solution to my problem. Apart from the cost, it would require planning permission, be a centrally placed hard to miss eyesore, and I'm nervous about owning anything that might fall on a public road or into someone else's property. Moving house seems a bit extreme - I'm not that keen on amateur radio!

Apologies to anyone bored by our drift off topic - it's related to 'Interests other than Model Engineering'.


11/12/2018 09:29:44
Posted by JasonB on 11/12/2018 07:22:23:

Dave, you can get it on e-bay my the meter but it does work out pricy, same seller does 5, 7.5, 10 and 20m lengths.

20m seems best buy for you at £18 inc postage

Jason, you are my hero! That's a better price than any of the suppliers I found yesterday and I don't have to buy a 50m roll! I've just ordered 20m.



10/12/2018 22:01:43

Posted by Joseph Noci 1 on 10/12/2018 20:04:50:


I am not quite sure what type of loop antenna this is - maybe Dave can enlighten? Is it a loop tuned across an open end by means of a variable capacitor? How do you feed the RF input? Is it via a smaller inductively coupled loop, or a tuned stub?

I have made a few loop antenna for the HF amateur bands, some used a tunable vacuum capacitor and some using a home-brew vane capacitor, but all made from plumbers copper tubing - very easy to make with that tubing, very rigid and quick to modify. A 1.2m diameter loop easily covers from 5MHz to 18MHz with a 30pf to 1800pf tuning capacitor, so if the bespoke tubing is not easily found, try copper tubing with a small increase in diameter.




This is a vane type variable cap I made - the two copper tubes on the left fit into the loop open ends.

The cap was able to withstand 8KV, ie, 500watts on HF..





Thanks Joe,

Nice pictures from you as usual - I wish I had your brains, energy and skill. I love a well-made variable capacitor that can handle a bit of power!

I'm in the process of discovering that my house is in a painfully poor HF location. My garden is on the small size and the position of the house makes it awkward to run and feed wire antennas. The really difficult part is I live on a street corner and the house has telephone wires on three sides. Quite noisy in a village at the best of times due to overhead power lines everywhere but ADSL and VDSL leakage has added another level of misery. Got even worse after dark last week - I strongly suspect xmas lighting.

I've started using WSPR to test alternative transmit antennas from 80m up. But there's not much point in transmitting if I can't hear replies due to noise. I've bought a KiwiSDR as part of the investigations. It can waterfall 0-30MHz in one go and has 4 separate receivers, and is proving useful as a way of seeing how the noise is distributed as well as identifying the sources.

The antenna I'm making is an untuned broadband receive loop to feed the Kiwi. I had some success balancing noise out with a doublet (unfortunately not suitable as a permanent solution) and am hoping a small loop might do better.

Building a tuned transmit loop like yours is also a possible solution. The hard part is the high voltage capacitor, tuning it remotely, and keeping it dry! I'm concentrating on wires for transmit at the moment because I'm more interested in 3.5, 7, & 10 than the higher bands

Edited By SillyOldDuffer on 10/12/2018 22:03:20

10/12/2018 20:54:34

I'm in darkest Somerset, so Buxton is a bit of a stretch. As is importing it from the continent (thanks ANOther!)

I was hoping to find the European version readily available in the UK. It's recommended because it's cheap and easily bent to the right shape - a few minutes work. It's a DIY store product abroad. What I'm finding is that the UK types are rather heavier, significantly more expensive and harder to source. I can buy it by the roll from the internet, but 25 or 50m is more than I need.

Here's an example of a cheap pipe loop - very straightforward, and I need two:

It is possible to make the loop from other types of pipe. This pair is in 10mm copper:

But see the additional complication. Each loop is made as a pair in parallel to reduce the inductance. The copper is also a bit pricey.

Professional loops of this type are made from Aluminium tube. Two objections: the 3m length of stiff tube I would have to transport; and bending it neatly. The professionals have bending machines.

Copper is easier to bend than aluminium but it would soon get expensive if I kinked the pipe and had to start again! Again 3m lengths are inconvenient for me to handle. To bend the pipe without a machine I would fill the pipe with sand and wrap it round a former - I feel that's less trouble than bending it section by section on a short coil spring. Certainly do-able but far more trouble do this in copper than pulling a bendy plastic pipe into shape!

Rules of the game:

  • Copper or aluminium : wall thickness doesn't matter.
  • Preferably no joints.
  • Easily bent in a circle. (Circle preferred to other shapes because it maximises the area enclosed within a minimum inductance.)
  • Two similar loops required. As performance depends partly on balance, ideally the two loops would be identical but it's not that critical.
  • Diameter of tube big rather than small to minimise inductance (10mm requires parallel loops). But wide tubes are harder to bend.
  • Cheap
  • Able to resist ordinary bad weather for a year.

Suggestions so far have been very helpful. If I don't end up with a simple cheap solution it wasn't for lack of trying!

Thanks again,



Edited By SillyOldDuffer on 10/12/2018 20:58:28

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