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Member postings for Alan Charleston

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

Thread: The Pitch Drop Experiment
09/01/2021 05:42:03

Hi Nick,

I don't think your assertion that glass is not a supercooled liquid is correct. If you look at the ternary phase diagram of the system Na2O - CaO - SiO2 (soda glass) there are a whole host of different compounds which can crystallise from it, most notably devitrite - Na2Ca3Si6O16. If molten glass is slowly cooled from above the liquidus temperature and held at or just below it, the mass will crystallise. The fact that it hasn't in your windows, is that the rate of cooling below the liquidus is such that the viscosity quickly rises to a level which prevents the atoms in the glass from migrating to take their places in a crystal lattice. Normally, a supercooled liquid is formed when the liquid is completely free of impurities which can act as seeds for crystal nucleation, and the system remains liquid below the liquidus temperature shown in its phase diagram. I would suggest that glass is in the same state - i.e. amorphous (non - crystalline) below the liquidus temperature.

As far as other materials (steel or wood for example) also becoming curved when supported at their ends, I would make the following argument.

I believe that liquid flow is the result of the elements within the substance rearranging themselves at an atomic or molecular level. This would be the case with an amorphous material such as glass. It would not however be the case in steel, where the rearrangement would involve crystalline components sliding past each other or wood which would involve the fibres sliding past each other.

Of course my argument is predicated on my definition of liquid flow which could be a load of bollocks.

Regards,

Alan

08/01/2021 04:31:39

Hi,

Glass does indeed flow over time. I used to work in a lab and there was a room set aside for glassblowing. About 20 years before I got there, the staff used to make glass coils for a gas chromatograph from straight lengths of thin wall soda glass tubing (OD about 4mm) which were about 6 feet long. These were stored in a wooden box which was about 5 feet long, so one end was in the box while the other end was supported by the top of the box. After 20 years or so, each of the tubes was permanently curved, with the middle of them being at least 6 inches away from a straight line between the two ends. This was presumably due the plastic deformation (flow) of the glass over that time.

If you want to see a really long term experiment, have a look at this:

https://en.wikipedia.org/wiki/Oxford_Electric_Bell

Truly amazing.

Regards,

Alan

Thread: Restoring a Boxford AUD ll
06/01/2021 05:16:27

Hi Finn,

I bought a new T Link drive belt when I restored my AUD from here:

http://www.lathes.co.uk/page4.html

Tony quotes 60 pounds for a 1.4 meter length which is required for a Boxford. This seems a lot more expensive than the 18 pounds/meter from eBay but on the other hand, mine hasn't stretched since I put it in a couple of years ago.

Regards,

Alan

Thread: Odd thread
06/01/2021 05:01:56

Hi,

Thanks for all the replies. I think I'll try option a or b as set out by pgk.

Thanks for the offer of a manual Andy but I found a pdf copy of one here:

https://physicsmuseum.uq.edu.au/abbe-refractometer

Regards,

Alan

05/01/2021 05:40:22

Hi,

I bought an old Hilger and Watts refractometer on the local auction site. It has a 6" thermometer in a metal case sticking out the side, which was snapped off during delivery. The metal case is attached to the instrument via a ring of knurled brass with male threads on both sides. This is the thing which broke, and I need to make a new one. The thread is however odd. The OD is 8.5mm (.335" and it has 40TPI. At first I thought it might be a 5/16" model engineers thread, but the 40TPI only applies up to 1/4" and then it drops to 32TPI and 5/16" is only 7.9mm in any case. I have made a piece of threaded rod 8.5mmOD X 40TPI using a 60 degree cutter and it screws nicely into the thermometer case and the instrument. The threads only extend about 5mm from the knurled disc in the middle, and I'm not keen on cutting such a short thread up to a shoulder. I would rather use a length of threaded rod screwed through the disc and loctite it in place. To do this, I need a tap. Anybody got any suggestions as to what the thread is?

Thanks,

Alan

Thread: Cutting Microscope Slide Glass
14/11/2020 04:59:30

Hi Ramon,

If you're going to use the scribe and break method, you may find that spitting on the scribed line (or licking your finger and running it over the line) will help to get a clean break. The glassblower who taught my laboratory practice class recommended this when snapping glass tubing.

Regards,

Alan

Thread: In flight social distancing
16/10/2020 05:35:20

Hi,

I get Emails from a crowd called Innocentive every so often. They ask for solutions to problems for organisations and pay for any ideas which are used. A couple of days ago I got the following:

" This Challenge is looking for an original layout design of commercial airplane cabins mixing both passengers and cargo in such a way that social distancing between passengers is guaranteed through the positioning of air cargo as barriers between passengers. "

So I guess one way of getting social distancing is to have a crate replacing every second seat. Not a bad idea really as there is a shortage of air freight capacity as a lot of it went in the hold of passenger aircraft.

On the bright side there won't be any disputes over who gets to use the armrests as crates tend not to have arms.

Regards,

Alan

Thread: Chinese BS0 Dividing Head
12/10/2020 06:20:20

Hi Henry,

I bought a vertex BSO dividing head about twenty years ago and I've been happy with it. The only problem I've struck with it is that the tapered hole in the spindle is a Brown and Sharp taper rather than a Morse taper. I'm not sure if they are all like that. The problem I struck was that I've got a set of #2 Morse taper collets which I couldn't use on the dividing head and I couldn't find any Brown and Sharp taper collets anywhere. I ended up making a 1/2" B&S taper collet out of brass together with a series of adapters with ODs of 1/2" and IDs of 1/8", 1/4" etc.

Regards,

Alan

Thread: Controlling air
11/10/2020 06:06:04

Hi,

I used to do the same as what you are planning to do when I worked in a factory. I hooked a pressure sensor to a tee on the air line and connected it to a data logger to measure the height of water in a tank. I originally tried to control the rate of bubble formation using a pressure reducing valve. The problem was that the flow rate varied with the depth of the liquid and I could never get a stable air flow rate.

I ended up using plant air at 110 psi through a ball valve.

Get the smallest ball valve you can find, shut it and connect between an air compressor and your tube. Put the tube into the liquid and slowly crack the ball valve open until you get the desired flow rate (bubbles/second). If the liquid level changes it shouldn't affect the flow rate as the supply pressure is so much greater than the variation in back pressure and the pressure drop change across the valve ( and hence the air flow rate) will be trivial. If you want to monitor the liquid level then put a tee in between the valve and the tube and connect it to a pressure gauge.

Trying to get a stable air flow by setting the pressure will not give stable operation.

Regards,

Alan

Thread: Threading trouble
03/10/2020 06:11:11

Hi Matt,

One way to power reverse would be to get a socket to fit the nut on the back of the spindle, weld a piece of hex bar into the square dive hole and use your battery drill to drive it anticlockwise. Of course you would have to make sure you didn't move the nut.

Regards,

Alan

02/10/2020 05:30:24

Hi Matt,

You don't need to keep the half nut engaged when cutting a metric thread on an imperial lathe if you have a thread dial fitted. The procedure to follow is:

After setting the tool to cut the correct depth, start the lathe in the forward direction and when the thread dial reads 1, engage the thread nut.

When the tool has advanced to the end of the thread, disengage the half nut and turn the motor off.

Withdraw the tool to clear the work.

Start the lathe in reverse and when the thread dial reads 1 engage the half nut.

Run the lathe in reverse until the tool clears the work.

Turn the lathe off but leave the half nut engaged.

Set the tool to the new depth and start the lathe in the forward direction.

Repeat till the thread is cut to size.

This method is useful because disengaging the half nut stops the tool a lot quicker than waiting for the lathe to run down giving a more accurate stopping point.

This won't fix your problem though if you can't reverse your motor. It may be cheaper to get someone who knows what they are doing to rewire your existing motor through a reversing switch than getting a new lathe.

Regards,

Alan

Thread: Emco V10p
23/09/2020 07:21:28

Hi Neil,

I used to have an EMCO V10P and foolishly sold it when I had problems with the headstock gears. Instead of paying to get them fixed I sold the EMCO and bought a Seig SC4 which I have regretted ever since.

I'm not sure about the gearbox, but when I first bought the Emco, I disconnected the wires from the 5 button electrical box without properly documenting where everything went and then couldn't put it back together again. I took the lathe motor and the box into work and showed it to the sparky who couldn't work it out and sent it out to a specialist motor guy who connected it up for me. I never did get the mill motor reconnected - instead I used a separate switch with a capacitor mounted on the wall behind the lathe.

Here is a link to the V10P manual which has a basic wiring diagram on the last page.

https://elcompptyltd.co.za/wp-content/uploads/sites/312/2019/04/Maximat-V10P-Instruction-Manual-RED.pdf

Good luck with it - it didn't help me much.

Regards,

Alan

Thread: Change gear alternative material
21/09/2020 07:28:46

Hi Paul,

I made a set of change gears for my Boxford AUD lathe using Delrin. It works a treat and is easy to cut. I cut them from a 10mm thick sheet rather than having to get a selection of round stock. Luckily the tumbler gears were stamped 20 P.A. so I didn't have to guess the pressure angle. You can get a full set of gear cutters from the Chinese site which dares not speak it's name on this forum for $100 or so.

Regards,

Alan

Thread: Motorising the feed screw
16/08/2020 07:29:37

Hi,

I'd like to do the same. I have a couple of stepper motors but I can't figure out how to control their speeds using a potentiometer. I'm sure it's a trivial matter using an arduino to someone who understands these things, so trivial in fact that I can't find anywhere on the interweb which explains completely how to do it.

Deleted see Code of Conduct.

It looks like what I'm after but I'm not sure what else is required. Can anyone help, or give an idiots guide on how to achieve it with an Arduino. Don't worry about insulting me by stating the obvious, you can't underestimate how rubbish I am at getting anything useful out of an Arduino.

Regards,

Alan

Edited By JasonB on 16/08/2020 07:31:47

Thread: Triumph motorcycle auction
09/08/2020 07:13:03

Hi,

For the last 5-10 years I have been puzzled as to why manufacturing jobs are being lost to low wage economies. With the advent of CNC machines, I would have thought that the cost of capital rather than the cost of labour would be the determining factor as to where articles are manufactured.

I could envisage a factory making lathes for example which employed CNC machinery for machining the components and automated systems for supplying raw materials and moving the finished components around, assembling them into the final products, packing and despatching them with no human workers in sight.

The cost of a product coming out of a factory like this would be dependent on the capital required to set it up rather than the cost of labour to run it.

I don't know about the UK, but the USA is known for its ability to raise capital for manufacturing enterprises, so why are (I nearly said jobs but with an automated factory there's not many of those anyway) the factories moving to Asia?

Any economists out there who can enlighten me?

Regards,

Alan

Thread: Melting bronze
03/08/2020 07:08:13

Hi,

I used to work in a factory which had a glass furnace. The flow rate of the glass was checked by running it into a steel container over a timed interval and weighing it. A sheet of newspaper was placed in the container first, and it burnt out leaving a layer of carbon between the molten glass and the steel which stopped the glass sticking to it.

Regards,

Alan

Thread: Measuring Gears (including pressure angle)
22/06/2020 07:36:31

Thanks Andy. It's good to have all this info in one place. I've printed it out for reference. I've always been stumped when it comes to determining the pressure angle. I'm not sure how to measure the span across the flanks. Are the tips of the caliper presented to the circumference of the gear, which will measure the span fairly high up the tooth, or to the side of the gear where the span can be measured fairly close to the root?

Regards,

Alan

Thread: Problems bending 3/16" dia copper pipe without kinking
14/06/2020 06:59:14

Hi,

I've had success bending 1/8" copper tube by inserting a length of nylon strimmer line into the tube before bending. 1.65mm line is a snug fit. The line is removed after bending the tube using a metal plate with a 2mm hole drilled in it. The line is threaded through the hole and the end of the tube butts up against the plate. The line is grasped with a pair of pliers and levered out by pivoting the pliers against the plate. I can get tight bends with no kinking.

It's important that the line is removed after each bend is made as the resistance to being pulled out increases with each bend until it snaps off instead of coming out. Then you are up for heating the tube and applying compressed air until molten plastic is squirted across the workshop.

I'm not sure strimmer line is available in the diameter needed for 3/16" tube, but if it is, it might be worth a go.

Regards,

Alan

Thread: Spot Facing With Slot Drill?
18/05/2020 07:19:23

Hi Ron,

I'm not clear as to how you milled the teeth. From your picture, I can see that the bottom of the cutter is in the same plane as the angled part of the tooth but the side of the cutter doesn't line up with the part of the tooth which is parallel to the drill. If the teeth were cut as shown, wouldn't you end up with a negative rake? Did you file the side of the tooth after milling to give a neutral rake?

Regards,

Alan

Sorry Ron, I've looked at your post again and I see you say you filed the cutter after hardening to sort the rake out. I initially thought you meant you had filed the top of the teeth to provide clearance after milling the top of the teeth to ensure they were all the same height.

Alan

Edited By Alan Charleston on 18/05/2020 07:30:11

Thread: Insulating board that won't drop powder as it is touched
30/03/2020 06:44:54

Hi,

I would agree with Dick that painting it with a solution of water glass (sodium silicate) would fix the problem. Years ago I made a small oven for use in a lab and it was insulated with a putty of powdered asbestos and sodium silicate solution. It was plastered on and dried by turning the oven on. The surface was stable and I used it for years.

Regards,

Alan

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