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Member postings for Macolm

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

Thread: Galvanic Corrosion
03/05/2022 14:17:18

spheretester.jpg

Despite intuitive doubts, I used this method to free very corroded hydraulic unions on Citroen rear suspension cylinders. You can see the design on this photo of a tester made from a such a cylinder. I agree that spot welder dissipation will be lower for aluminium, but with perhaps 5000 joules available over a couple of seconds, 10 grams can be heated by more than 300C. Then taking the differential expansion as 7 parts per million per degree C, we have 2 thou per inch (to mix units!), a very useful loosening of the parts. It does indeed work.

03/05/2022 10:29:29

I have had reasonable success with parts of that configuration using a portable spot welder. There needs to be access to clamp the jaws across opposite sides of the boss. After scraping to get contact, power is applied to heat it. The current only flows in the outer, so expansion tends to loosen the grip. With steel it takes maximum welder settings to get to near red heat as quickly as possible. Aluminium must obviously to be kept cooler, but expands more. If the parts move at all, it is then merely a case of working in penetration oil, and patience. The method can also facilitate oil penetration at lower temperatures, with just enough heat to result in a capillary gap.

The fast and targeted heating seems to increase the chance of success. The nearest alternative is fast heating with oxy-acetylene which is far more risky.

Thread: cutting pyrex tube to length
17/04/2022 22:20:00

A point about cutting glass is to score as lightly as possible. Too heavy pressure tends to cause small sideways cracks which may result in the snap not following the marked line.

Thread: Why is electricity so expensive?
06/04/2022 11:59:43

The magical thinking is that something new and different will prove better than an existing technology that has had the sharp edges knocked off over many years. Take wind generation, which is perceived as new and shiny. When was the first wind farm of recognisably modern machines? The answer is about 1978! Thus the technology is more than 40 years old, and it can be argued has just about reached its full potential.

 

A rule of thumb that fits the energy sector quite well starts with a successful demonstrator. Unless this leads to a satisfactory first of series within 10 years, the concept will not succeed. Try this to evaluate your favourite notion. Then remember that full infrastructure takes decades to put in place.

 

The world population has tripled over my lifetime, in no small part enabled by low cost energy to provide a myriad of essentials to our wellbeing. Such things as refrigeration and distribution systems, and pharmaceuticals and chemicals including fertilisers to name but two sectors. These things are the real baseload of the energy system, and it is unclear how any existing renewables can adequately support our lifestyle. On the other hand, reversion to an agrarian economy may not turn out to be popular!

Edited By Macolm on 06/04/2022 12:01:33

Edited By Macolm on 06/04/2022 12:02:16

06/04/2022 08:41:27

As soon as I switched off the computer last night, I realised I got my arithmetic wrong. One mega battery a day only equates with 2 days storage, it needs 10 a day. After 11 years, bingo, 20 days storage, and we can then continue installing them at the same rate in perpetuity to replace those at the end of life.

05/04/2022 21:41:11

The difficulty with storage to make good the variability of renewables is the vast amount necessary. Currently on average, the UK uses 30GW daily, which equates to about 700GWh of energy (0.7TWh). If heating and vehicles are to be powered solely by electricity, this will increase to perhaps 2TWh. For comparison, current pumped storage capacity is about 5GWh.

There can be many weeks with overall average wind power of less than 10% of capacity, and midwinter solar output is a few percent of capacity. So at least 20 days of storage would likely be required, say 40TWh. Large grid connected batteries of circa 1GWh are currently being deployed to stabilise the grid against wind power fluctuations, but 4,000 would be needed. Sounds OK? Well, it would be one a day installed for the next 11 years. The story using hydrogen is similar, many millions of 700 bar cylinders, cryogenic storage of about the same capacity as the UK current tank farm inventory, or chemical storage yet to be developed at scale.

A further thought. Crossrail will have taken 14 years (including detail planning) if completed in 2022. When it kicked off, the technologies were all available and mature, the task was fully defined, and the funding was understood. And this electrical transformation will be completed in just 13 years? Is there really a feasible plan?

05/04/2022 17:07:53

The quietly hidden trigger for the current energy price escalation was forcing coal, nuclear and oil out of electricity generation in Europe. This would have been fine if there was a competent plan to ensure that feasible replacements were available promptly. The coming crisis was clear enough to see when large price spikes in wholesale electricity prices started happening in 2019 in the UK and many other counties. There was simply too little spare capacity.

Covid restrictions reduced demand and the problem seemed to disappear, but with the start of economic recovery last year it re-emerged, and now more serious due to further loss of dispatchable capacity in the interim. What had started in the electricity sector quickly affected the whole gas market. No doubt suppliers took their chance for a fast buck, but where do we go from here?

Thread: Searching for a good quality, metric-only, 300mm steel ruler
22/03/2022 21:19:07

Search for Starrett C331, though perhaps only available easily in USA. It has 1mm graduations one edge, and short 0.5mm on the other, and is 300mm long so can readily be used reversed. Not cheap!

Edited By Macolm on 22/03/2022 21:19:44

Thread: Cheap silver oxide batteries.
08/03/2022 14:54:16

Do Internet search for brand and type you want eg Renata SR44, and you should find you can get a pack of 10 at an acceptable price. Indeed be wary of ebay, but it is possible to buy genuine cheaply there.

 

Edited By Macolm on 08/03/2022 14:56:09

Thread: Vickers Metropolitan Capacitor Motor 1/4 hp BKC 2410
03/03/2022 21:24:17

A low risk way to test a motor like this after doing the basic checks is to connect it in series with an old fashioned quartz halogen security light, assuming you can find one. A 500 watt 230V mains lamp will reach 125 ohms when hot, but start at 12 ohms or so when cold. If the motor (without mechanical load) is OK, it will run, and the lamp will not light up much. If the motor does not run, the lamp will light fully, and the current will be limited to less than 2 amps.

Thread: Spectacles
18/02/2022 21:46:20

The field of view is very small with what are effectively small telescopes. They are good for their intended purpose, but unlikely to be suitable for most engineering tasks. The headbands with additional lenses as in the previous post are more suitable.

 

Edited By Macolm on 18/02/2022 21:49:07

Edited By Macolm on 18/02/2022 21:49:53

Thread: The demise of UK fossil fuel Power Stations
25/01/2022 17:37:02

Driving out coal and nuclear generation in the UK and most of Europe has been very successful, and there is also a presumption against further gas fired generation. The monumental failure of governments has been to put in place any practicable replacement.

A parable. You quite like lettuce, and your wife is crazy about them. To have fresh lettuce every day, you plant twenty rows of twenty, a total of um er, is it 400? Enough for a newly picked lettuce every day of the year, and some spare. What could possibly spoil such a brilliant plan?

Unfortunately, this appears very close to the thinking behind our electricity system, where the average output of renewables is assumed as always available, and without practicable provision for the prolonged periods of low wind that occur.

As a comparison, consider the Crossrail project. If it opens this year, it will have been 14 years from initiation. At the start, all the technologies were available and well proven, all that was needed was detailed planning and execution. A similar timescale is proposed for the electricity grid to become CO2 emission free, but in contrast, the key storage or backup technologies are currently not proven as practicable, or are even unidentified. Over last summer there were more than 10 weeks consistently low wind generation. To cope with such a situation would require an impractical amount of storage for current technologies.

Finally, from https://www2.bmreports.com , here is current UK grid data and prices. Yesterday, the balancing cost reached £4 per kwh. Today only 53p!

electricity250122.jpg

Thread: Chester Conquest Mill Spindle
13/01/2022 21:20:13

Try not to mangle it! I usually manage to grip such keys in a milling vice. It will probably need an equal thickness spacer to keep the jaws parallel, or perhaps even a slightly thicker spacer to ensure gripping along the inner side of the key. Start with it really tight, once it slips off, the chances of success reduce. A vice with rounded jaws is hopeless.

Another possibility is vice-grips or a mole wrench. Again, probably needs to be the genuine article to have much chance, and again as tight as possible. Tap shaft with a copper mallet, or if not available, apply hammer via a piece of aluminium etc to avoid bruising.

Thread: Recomendations for a Keyless Chuck?
31/12/2021 12:50:15

Clive

Interesting find, and should be good for intended purpose. Like the ordinary low cost keyless chucks that come with portable drills, closing may be very low geared. Another possible source of quicker closing traditional keyless and locking is Metabo, the first type on the following webpage are well made, again for percusion use. Whether easy to get in the UK I don`t know. They are long though.

 

**LINK**

Edited By Macolm on 31/12/2021 12:52:36

31/12/2021 10:21:02

Most of the annoyances of ordinary keyless chucks can be much reduced by the reverse lock type. Here is what a Rohm model looks like, I think it is 1.5mm to 13mm and is a thread mount. You can see the lock ring with release direction arrow. I made up the arbor to minimise the height, which is little more than a key type.

rohmchuck.jpg

Operation of the locking ring is very intuitive, scarcely noticed once you are familiar with it. In fact, the chuck is sold primarily for impact use on a portable drill, but is made to a high standard, and concentricity is excellent. It does have holes for C spanner release, but this has never been necessary in ordinary use on the mill.

30/12/2021 22:15:58

Note there are "reverse lock" keyless chucks. These have a ratchet that prevents loosening, released by a ring at the arbor end. Though not particularly useful on the lathe, I would not be without one on the mill. It is secure enough to grip milling cutters for spot facing, though of course not stiff enough for actual milling.

Thread: bantam 1600 electronic problem
20/12/2021 14:36:10

Even if it is a MK 1, if using with a VFD I would suggest a 2 pole 2800rpm motor if changing from what you have. This would get spindle up to 2000rpm or more which seems within the capability of the bearings, if somewhat noisy due to straight cut headstock gears. It is useful for small work though probably not used much. Lowest gearbox range is 22 times reduction from that, so a nominal 72rpm, and less than 20rpm available via VFD. Torque clearly is increased by 22 times relative to top speed.

As usual, there should be no switches between the motor and the VFD, so the original wiring is best discarded.

Thread: Pin-hole in oil pan - which product to patch it?
18/12/2021 21:54:32

You will almost certainly find it impossible to get a bond with ordinary epoxy with any oil contamination. Petropatch now seems to be an epoxy putty - I suppose it might be formulated to work with existing oil contamination, but I doubt it. It was once akin to jointing compound, and a cloth patch. Also, there was a Bostik two component acrylic adhesive that would adhere to an oily surface, absorbing the oil. As an aside, there are epoxies that bond polythene ski sole material, so clever chemical action is possible.

Try search for oily surface adhesives. I found ThreeBond 1217M, but there should be others. Be prepared for a shock when you see some of the prices!

Thread: Shortening Screws
13/12/2021 17:31:10

If your lathe can be used in reverse, mounting the screw from inside a threaded sleeve allows the excess to be parted off. I have an interal grooving tool that works for this. I just hold it in a three jaw chuck, which is adequate for most purposes.

screwholder.jpg

Edited By Macolm on 13/12/2021 17:33:33

Edited By Macolm on 13/12/2021 17:34:17

Thread: Axminster Drill Clamp
22/11/2021 12:35:34

I should mention that the implementation shown suffers from the deficiency that there is a considerable bending moment at the junction of stud and clamp body. It was originally intended to buttress it here with a large diameter threaded sleeve, say M10 inside and about 20mm fine outside for the clamping wheel thread. This was not done because no suitable combination of tap/die/bolt was found. Despite this, it has so far been satisfactory.

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