Member postings for Robert Atkinson 2

The laws of physics don't change. While the references may be old the application note metadata indicates it was authored in 2000 and last updated in 2013

Data sheets hardly ever highlight the shortcomings of the device.

Thyristor SSRs tend to have short off periods at low load current excerbating this problem.

Robert G8RPI.

You should not use a zero crossing SSR with a highly inductive load like a transformer. Turning on at zero causes very high peak currents. See:
https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=13C3206_AppNote&DocType=CS&DocLang=EN

Robert G8RPI.

Edited By Robert Atkinson 2 on 25/03/2021 20:57:19

my employer, Marshall Aerospace still provides apprenticeships and the is plenty of hands on work with hand tools. They rotate through departments and attend college. If they wish they can do a part time degree with day release after they start working. Our chief engineer started as an apprentice so there is no limit to how far they can progress. No discrimination either, but a lot of applicants so you have to be good to get a place.

As Bill says, it can help fatigue life by removing transverse scratches from the edge of sheet or plate material.

I was taught this by Desmond Norman when helping make the curved spray bar supports you can see under the the wing in this picture:

https://s3.eu-west-2.amazonaws.com/abpic-media-eu-production/pictures/full_size_0243/1365100-large.jpg

I'm avionics based but A. my traning included "fitting" and basic machining and B. We were in a rush to get the aircraft out for a customer demonstration. It was "all hands to the pumps" so I started filing as did Desmond. While the factory was "sheet metal in, aircraft out", we had no CNC machines etc. The supports were band sawed roughly to shape and then filed.
When doing filing exercises during training we were not allowed to draw file because it was to easy to get a nice finish. And yes those are the actual items in the 35 year old photo, we only ever made one set.

Robert G8RPI.

The TCP is my favorite iron. I've used one I've used them for over 40 years. The Metcal RF heated curipoint irons are as good but much more expensive. The number on the bit sensor disk (curie point alloy) is the temperature in hundreads of degrees C. A 7 is good for 60/40 lead solder, a 8 is better for most lead free solders.

Note that the latest bits for these are two parts, a rear with sensor disk and a front "tip" while these are cheaper, they are not as good as the old one piece bits as the heat has to flow through the flat disk junction between the two halves and the sennso disk is better coupled to the heater than the tip.

Robert G8RPI

Well the original post said the current set-up was struggling with larger drills. This tends to rule out high speed motors like the brushless DC. While power is important, the speed of the cutting edge and available torque are the crtical parameters. A 300W 30,000 RPM motor will not be much use for drilling a 6mm hole in steel.

We also don't know what the original motor is other than "mains" a "universal" motor will be much more use than a small induction motor.

Generally I think buying a used 18V (or higher) two speed gearbox battery drill and using the motor gearbox assembly will be the most practical and cost effective approach. You migh need a bigger power supply though.
The better drills have a separate module with motor and gears rather than using the casing.

Robert G8RPI

Edited By Robert Atkinson 2 on 18/03/2021 12:57:36

The commentors on my methanol commen are correct meths is indeed 95% ethanol plus about 5% methanol. Not sure why I said otherwise.

Surgical spirit is NOT the same it is mostly Methyl Salicylate which is not hydroscopic. In fact there was an old magic of a mixture of surgical spirit and water is shaken and applied to a audience members handkerchief and then set on fire. The water is absorbed into the cotton and protects it while the sprit burns. Not so common now due to lack of handkies and excessive fire precautions.

Robert G8RPI.

Meths is mainly methanol which is hygroscopic. Over time it will absorb water from the atmosphre unless in a hemetically sealed container. Water conten will affet the flamability and probably the flame temperature.

Robert G8RPI.

One thing that makes a difference to he robustness of the system is what power supply you are using. Most modern supplies will let the voltage generated by the motor (and fed through diodes to the supply) to exceed the voltage rating of components in the drive or other circuits, causing damage. One solution is to put a voltage clamp like a zener diode across the supply. For example a 32V zener across a 24V supply. The zener must be large, a 5W one minimum. Another option is a fixed load (resistor) across the supply but this wastes power.

Robert G8RPI

Michael G. is correct, the sensor uses a directional source (Spot or slit) which is off-axis with the detector. Empty tube has two identical but opposing "lenses" so has little effect even if thick walled. When filled with water it acts as a cylindrical lens and spreads the light beam. This causes some light to hit the sensor. There needs to be some depth to the hole or slot on the source and detector to make them directional. A slot (must be parallel to tube axis) gives a stronger signal but less level resolution.
One trick is to use a LED identical to the source as a photodiode detector. They are cheap, work well and are spectrally matched to the source. Jut don't use a white one. Small red laser dodes are now cheap enough to consider as a source. If you have a red laser pointer it is good for visual experimentation.
I've used this in commercial products in the past.

Robert G8RPI.

The straight type of cable gland shown by the OP applies axial load to a short fairly thick wall rubber seal. This makes a very good seal without crushing the cable / pipe running through it. The "dome" type use a thin wall seal compressed by fingers under the dome. This puts high local pressure on the cable / pipe. Many years ago I actually used the straight type with silicone grease to make a waterproof seal on a switch shaft.

Digikey have a UK office, per the link Price is plus VAT but there is no duty or fees to pay. If you mke it up to £30 odd pounds with other items shipping is free.

Robert G8RPI.

At the day job I have actually used small PIC microcontrollers in designs were a 555 timer would have don the job. problem is the 555 needed more components and an expensive capacitor to get the required accuracy. overall cost was much higher.
Conversly a few years ago I used transistors and diodes to implement a control system (several inputs and outputs a bit of timing and a 3 state sequencer) that would have been a much simpler job to implement with a PIC. It ended up with 25 transistors plus a bunch of other components. Why would yo do that? It was a aerospace application with very low production quantity. Even though it was a low crticality system (DAL C) the cost of documenting and validating the software (to DO-178) was a very significant cost, hundreds of man hours.
Another advantage as I was able to do the environmental qualification by analysis rather than test. Funnily enough though fully approved by the regulator our customer sold one on and the final user decided that they wanted to test it. They ran a full set of relevant tests (DO-160G) and fortunatly (but not surprisingly) it passed.
For high volume production the saving of even a few pence per unit is significant. Using a microcontroller also allows the addition of new functionality (or fixing bugs) without changing the hardware design or bill of materials. However connecting everything to the internet is a very bad idea IMHO.

Robert G8RPI.

I got a pair from ARC for christmas

www.arceurotrade.co.uk/Catalogue/Measurement/Calipers/Digital-Calipers-150mm-300mm-6-12

Very pleased with them so far.

Robert G8RPI.

I have some first surface mirrors that should suit. send me a PM.

Robert G8RPI. (Cambridge UK)

Yes,

You will have to have the software on the XP machine, but you can install that from a USB stick or CD-ROM.

One thing that has not been mentioned is Start Stop controls. You really need to to switch at least the start switch (button) with the motor. You don't want to push the start on the mill and have the lathe start turning!
The Stop and E-Stop circuits for both machines can be wired in series (parallel if normally open) to the VFD so pushing stop on either machine will stop whichever is selected.

EMGEE sugessted a switch with auxillary contacts for the Stop circuit but this educes safety and does not address the start issue.

Personally I'd use a pair of electrically interlocked contactors and a 3 position (Lathe OFF MILL) rotary switch. An indicator light on each machine would be an added safety feature to let you know which is live .

Robert G8RPI.

The biggest issue with the ML-10 / Speed 10 that can't be overcome is the 3.25" centre height and lack of a gap.
Obviously this limits the maximum diameter you can turn to 6.5" compared to 7" (10" in gap) on a Seven or similar.
Some model engins etc have their castings, especially flywheels, sized to fit in 3.5" center height gap bed lathe.

If that's not a problem for you then it looks like a reasonable buy.

Yes there is.

Hold a brake disk in the chuck and rrange the brake caliiper so you can measure the force it reacts. This could be a bearing held in the tail stock with an arm holding the caliper. This, if unconstraned,would allow the caliper to rotate concentrically with the disk. constrain the movement with a one foot arm and spring balance. If the brake is applied so that the balance reads 10lbs you have 10 lb/ft torque. scale to suit lathe power.

Robert G8RPI

You can't judge a standards system by a single article. I think you are being somewhat partisan.

UL is not the be all and end all. Interestingly many fuse holders rated at 15 or 16A by UL are only rated at 10A by other standards e.g.
http://www.farnell.com/datasheets/2343262.pdf

Even Littlefuse (an amrican company recommend de rating from UL " Even small variations from the controlled test conditions can greatly affect the ratings of the fuse holder. For this reason, it is recommended that fuse holders be de-rated by 40% (operated at no more than 60% of the nominal current rating established using the Underwriter Laboratories test conditions). "

http://www.farnell.com/datasheets/1480080.pdf

Robert G8RPI.

You get what you pay for.

Components designed to reduce emission of ,or susceptibility to, electromagnetic interference (EMI) do not contribute to the basic function of the equipment. They are however essential for the safter of that equipment and other things like aircraft navigation systems. The problem is they are not cheap so some manufacturers leave them out or fit lower value, cheaper parts. The equipment still works without them until EMI causes issues. Often the circuit boards have spaces for them but the actual parts are not fitted or y compoin the case of coils, wire links fitted. A fully equipped unit would have been used for certification tests (if any were ever done). The same applies to other safety components like thermal overloads.

Robert G8RPI