Here is a list of all the postings Robert Atkinson 2 has made in our forums. Click on a thread name to jump to the thread.
|Thread: oxygen concentrators|
The other advantges of concentrators for home use is the removal of the safety hazards of high pressure cylinders and stored quantiities of oxygen in the home and and the logistics of supply and transport t multiple users.
|Thread: The sneering detractors|
I Have to agree with Dave (SOD) and Frances. We can't just ignore the bad stuff, certainly not the dangerous. No single person knows everthing or is always correct. Like dave I'm happy to be corrected or enter ino a civilised technical discussion. I probably come over as a bit of a health and safety concerned person, but I've no problem with people setting their own acceptable level of safety as long as it does not affect others. I certainly do things in my home workshop that I would never suggest others do, and some I would not even tell anone I'd done
|Thread: Power feed - 'which motor shall I buy'?|
I've looked at plenty of wiper motors over many years and fixed more than a few.
The one pictured in your album is typical, Adding a thrust ball to either the pressed steel motor cover or the cast alloy gear case should not be too difficult. Typically its the motor end that has no thrust beraing, typically just a self aligining (bll shaped) oilite type bush. There is normally enough room in the back of the housing to hold a suitable sized ball. A spacer / locator might be required but that's about it.
You could just put a bearing at the other end. A single ball for the spindle to thrust on would be good enough. Then you can auto reverse electrically. With tumbler gears you will have to stop rhe motor,move gears and re-start the motor.
Why have you got a tumbler reverse gear on a drive from a reversable motor?
|Thread: Used Lathe Pinnacle PL1340C Gap Bed|
A good rotary converter would run about 95% efficency at rated load. Most of this will be fixed lossses such as bearing drag and windage. I woud expect that a 185kW convertey would consume about 1kW off load. However you need to think kVA too because that's what the electricity meter responds to and can be a lot higher for an off load motor
If you are going to be running 3 or 4 5kW machine tools at the same time you should probably get a 3 phase supply. Otherwise modern solid state converters are probably the best solution. You don't HAVE to run a VFD att different frequencies, if you run it at 50 or 60 Hz it will run any machine if the voltage suits the motor.
However doing this requires some knowedge of power electronics and motors. The easy / safe solution is Clives number 3 suggestion to change the motor and use a VFD. It will pay for itself in power bill savingscompared to a rotary converter over the years and make the lathe more saleable of you don't keep it.
The same goes for other 3 phase machines. Try to buy one with a low voltage or Star/Delta motor or just change it. Don't forget you can sell the old motor to get some cost back.
I would not consider a rotary converter unless it was free and preferably delivered for free.
Edited By Robert Atkinson 2 on 17/05/2020 09:48:14
You can get any phase shift with an lnductor and capacitor with a fixed load. This is how the circuit you have seen works. Unfortunatly a machine tool motor is not a fixed load. The transwave and similar "converters" do this with component values for a typical motor and switched capacitor or taps for adjustment. It's not perfect but works. Often an unloaded motor is connected in parallel and turns all the time. It's inductance tends to swamp changes in the load reactance and it's rotating mass acts as an electrical flywheel.
This supply scheme is similar to that used in North America for domestic supplies. The NA one is 115V- 0-115V 180 degree phase shift to each house. It is used in some remote areas in the UK. Two wires are taken from the 3 phase high voltage (probably 11kV) supply and run to the remote location. Thi is of course single phase as there are only two wires. For each small group of consumers there is a transformer. In the simplest solution this would have a single 240 V (41.66:1 step down) output winding for the whole load at 240V. However the physics of transformer design means that a pair of windings connected 180 degrees out of phase use less core material. Splititng the load across two windings also means thinner wire can be used making winding easier. This scheme is called "Split-Phase" and uses a single (20.8:1 ratio) winding with a center tap. The center tap is the neutral for both supplies. Normally each consumer would only have a single 240V connetion but heavy users may have two. The voltage between the phases is 480V (if they were 120 degrees apart it would be 415V)
|Thread: Identify plastic glue|
if the old sealant peeled off, it clearly wasn'y solvent welded. The two part glues with mixing dispensers are typically epoxy or acrylic. Epoxy is not normally flexible so an acrylic is more likely. A two part silicone i also possible. For something readily available and durable I'd suggest a good quality clear RTV silicone. This may take some time to set fully so not so suited to a production environment hence their use of a two part product which are typically faster setting. At least with RTV you can remove it without damage.
|Thread: Myford ML4 Restoration: Headstock bearings and spindle removal|
I've got to agree with Brian on the pulley / Bull gear locking. The Myford instructions clearly say to unscrew the grubscrew in the pulley. Some ML1/2/34 have had a groove cut in the front headstock bearing casting to give access o the Bull gear locking screw. I wonder it this was to counter a seized pulley.
what a tease! You can't read the dimensions! Any chance of putting a higher resolution scan of the spindle drawing in your album or giving us the magzine issue information?
|Thread: Source of CNC plastic for software proving purposes|
Driving a tool into a block of foam or wax is much less likely to wreck the machine than doing the same into a block of alloy. It's not the cost of making the material, it's what the market (big CNC companies) think it is worth. Even a minor crash that just needs re-alignment can cost thousands of pounds in lost production time. A easy to use test material can be a good investment
|Thread: Possible protection from Covid|
I'll just wear my full face twin filter respirator
|Thread: Fixing lenses and mirrors into mounts.|
Mirrors and other optics on scientific equipment I've worked on were almost always secured to aluminium alloy mounts in a recess and 3 or 4 small spots of adhesive. Typically this was a filled opaque epoxy probably with thermal expansion between glass and alloy. Some use toughed acrylic like Loctite 330 (sometimes repackaged as optical adhesive with much inflated price tag)
There is excellent guidance here
|Thread: Used Lathe Pinnacle PL1340C Gap Bed|
It certainly doesn't look cared for and its not clear what is included in the sale. If there is a 4 jaw chuck and a bunch of tooling that could make a difference. I notice he has put a phone number in one of the images which is against ebay rules because it indicates they ma be trying to sell off ebay to save fees. Trouble is while you might get a better price you loose your protection if you buy off ebay. The seller may not have usesed it much but what about previous owners?
|Thread: Box-Shifters and Quality Assurance|
Gee's in Cambridge burnt down in July last year.
|Thread: Thermal fuse reliability|
These thermal fuses have a spring contact held closed by solder with a specific melting point. When the solder melts the spring pulls the connection apart breaking the circuit. The solder can suffer from metal fatigue and this causes failure. If the units normal temperature control works with a new fuse then it was just an old age failure of the fuse. If the new fuse trips or unit overheats you have another fault and the thermal fuse was doing it's job.
|Thread: questions about setting up my Myford ML4|
|Thread: Oscilloscope kits - any recommendations?|
The Picoscope software has an FFT function built in so they also act as spectrum analysers. Their automotive software has specialised vibration analysis and balancing functionality and they sell accerometer kits for it. https://www.picoauto.com/products/noise-vibration-and-balancing/nvh-overview
Plus 1 for Picoscope. Been a happy customer personally and for work for over twenty years. For beginers 'scopes are a bit like welders, it's easier to get good results with a better model. There are two problems with the low end models, low bandwith (maximum frequency you can measure) and limited input voltage, often only 5V maximum. The latter can be made worse by non-standard input impedance which means standard 10:1 probes can't be used. A 200kHz 5V unit is just about good enough for looking at a caliper based DRO. A mid level range between the low end stuff and Pico Technology is sold by Hantek but I've never used one. If you have space a "proper" conventional oscilloscope could be a good option. Hameg, Philips and Farnell are brands to look at as well as the obvious Tektronix and HP.
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