Member postings for Robert Atkinson 2

Not for production, that would be two part numbers for otherwise identical parts to make, stock and keep track of. That is extra cost. And the SRBF gear is probably cheaper anyway. But like so many of these things only the original designer knows the real reason. I've certainly designed things where you would not be able to guess why I chose a part.

Robert G8RPI

The broken gears do seem to be made from rod or tube rolled material rather than sheet so will have weaker teeth.

A couple of people have rubbished "Tufnol" however Tufnol is the manufacturer not the product. They make a wide range of materials, but we are talking about laminated phenolic resin materials. Within this product there are paper and fabric types. What most people call Tufnol is the fabric material. Even then there are different grades. The classic ones are Carp, Vole, Whale and Crow. Carp is the premium fine weave material. It has excellent properties and is frquently used in aerospace, both on aircraft and even more for jigs and fixtures.
Don't compare cheap imported material with a premium British product.

Robert G8RPI.

Edited By Robert Atkinson 2 on 18/03/2019 22:49:40

A PM DC motor will never make an alternator of any kind. The commutator rectifies the rotor output so they produce DC. They don't even make good generators as you cannot control the output voltage for speed or load variations. I guess you could use a 230V one with a switchmode step down voltage regulator but its a bit of a weird approach.

Robert G8RPI.

+1 for NFU Mutual. I have always found them very good for odd stuff like modified landrovers and gas turbine (jet) engines. They seem to be pretty pragmatic about things.

Big professional ones still exist too

www.zoro.co.uk/shop/power-tools/power-hacksaws/ajph200-hydraulic-hacksaw-machine-400v-3ph/p/ZT1028546X?

Lot of money £6000-£18000 for a saw though!

Robert G8RPI.

As it reverses by swapping the supply it is 99% certainly a permanent magnet DC motor. It looks like a PM. The odd 1% are the same as a "universal" (AC/DC) motor that has a full wave rectifier connected to either the field OR the armature winding. I've seen this on a couple of motors, it allows you to have a remote reverse switch with only two wires to the motor. It can be retrofitted to a standard universal motor. As you probably kinow to reverse a universal you have to swap just the field or armature.

Robert G8RPI.

Edited By Robert Atkinson 2 on 16/03/2019 22:54:31

The obvious answer to me is to ditch the gearbox and direct drive the leadscrew with a servo motor (or stepper) with a controller that is driven by pulses picked up from the headstock spindle (reluctance sensor off existing gear teeth or a new opto.). Any decent controller will be able to electronically gear the servo to the head at whatever ratio you need.

Then again I'm an electronics engineer.

Robert G8RPI.

Hi,

If there are 24 LEDs in the light then there must be 2 series strings of 12 wired in parallel. 1.7V (40/24) is not enough to light a white LED. For 10W wee need 0.25A at 40V So for resistor value (if we work on the peak voltage for a safety margin) the resistor needs to drop 320V - 40V at 0.25A so Ohms law gives us 320-40/0.25 = 1120 Ohms.
So say a 1000 ohm resistor. However the power rating of this resistor is 78 Watts (280x280 /1000) so it is not a practical solution unless you want a heater as well.

Robert G8RPI.

Two valves in series in liquid pipework have a potential issue that if you leave them both closed with fluid in the system thermal expansion can cause severe damage. The gauge will allow some expansion but if the pipe volume between valves is much larger than the volume of the bourdon tube in the gauge even normal UK daytime temperature changes could damage the gauge. One valve between pump and gauge will do all you need.

Robert G8RPI

Edited By Robert Atkinson 2 on 03/03/2019 21:54:30

Most likely for a measurement indication point that was relatively distant from the adjustment / setting location position. Now we would just use a electronic sensor with a remote display.

+ 1 for Devcon repair putty. As Clive said, drilling shallow damage is a good idea. I've seen a magnetic base drill with large cutter used on a big machine to turn spot damage into round or chain drilled depressions with sharp transitions from base metal to filler.

Robert.

Last thing you want is a published article on where to put a tracker, it will tell the theves where to look. Power for a tracker is a problem. Those in cars have internl batteriws kept charged from the main battery. Most steam models do not have a battery and generator. A hiding place where th antennas still operate is difficult on a metallic model. One thing every one should do is to to make a mark or number in a non-obvious place known only to you so the model can be identified if recovered. Don't forget to take photos of the marking.

This is not a "IBM/Simplex Synchronous Correction cycle" clock as suggested by SOD, it's a minute impulse with sync. Normally 1 ppm on red back pair but if out of sync a (normally manually initiated) series of rapid pulses on the white / black fast forwards until the cam switch opens. A capacitor discharge as suggested by Bazyle is a good idea. charged to between 12 and 24 V by a series resistor and discharged by a transistor through the coil.

Note that the IBM system is different in detail to the British ones.

I could be persuaded to do a circuit for you if you wanted. For a little extra I could put an rubidium standard in it so you would have your own atomic clock with 1 minute resolution

Robert G8RPI

Please don't destroy this artefact by putting a normal movement in it. They are fairly simple to drive and if you don't want to DIY, have a look at this

**LINK**

Off the shelf module available, but low cost is relative. For DIY you could hide a quartz clock with a disk with holes in place of a hand and a slotted optocoupler detecting the holes and driving the coil. just adjust the holes for the pulse rate needed. (for mains use a synchronous motor and gearbox with a microswitch or if you are that way inclined a PIC Arduino or RPi

Robert G8RPI

Flash-over can be deadly.
I know of one case when a technician was working on some "low voltage" (240V) instrumentation in a cabinet with a 44kV underground cable termination in it. The instrumentation was blowing a small sand-filled ceramic fuse. The technician ran out of fuses and replaced it with fuse wire. The fuse wire blew and the plasma created in the cabinet caused the 44kV feed to short out. The cabinet exploded and the technician was killed.

Most DLPs use a simple rotating filter wheel but some of the early high end ones use a combiner similar to the splitter shown but it's easier to combine colour than split them so simple methods are used. The spliter uses "dichroics" that reflect one set of wavelengths and transmit another.

Similar devices are used in fluorescence microscopes. I designed equipment using this stuff for several years but have now gone back to aviation .

Neil may be interested to know that I used to use Starlight Xpress cooled CCD cameras in instruments. They were sooo much cheaper than "proper" scientific ones that used the same, normally Sony HAD, CCDS. This come back to topic because these CCD are monochrome and intended to be used 3 at a time for high end video cameras that use dichoric splitters like the one pictured (but smaller). Being for a small market CCD availability was sporadic.

Robert G8RPI.

Neil is correct, but the simple expanation is that it is from a older colour TV camera where they had individual detectors one each for Red Green and Blue. The device separates the colours and feeds them to the correct sensor, probably a Vidicon vacuum tube. They are still used in higher quality CCD cameras -3CCD types.

Robert G8RPI.

Anything over 50V AC is potentally lethal. Just because you touched xxV and lived to tell does NOT make it safe. Unfortunatly the people who died are not on here to tell you how it went wrong. You can't be lucky everytime. Relying on dry hands, shoes etc is just plain stupid. Yes skin is the main thing that limits current but a burr on a screw head or wire strand can poerce your skin and bypass that.

The correct way to check for a dead circuit is to use a test lamp and a proving unit (low current battery operated 200V supply) 1st you check the lamp work with the proving unit then test the circuit with it. Next best is a multimter with low impedance like a Fuke with VoltChek, a contactless voltage detector or a neon screwdriver.

Ideaally have an isolator switch in the feed to the workshop, turn it off, and iif anyone else is around put a padlock on it. Over the top? Nanny state? Heleth and safety overkill? maybe, but you only get it wong once!

Robert G8RPI.

Edited By Robert Atkinson 2 on 01/02/2019 21:38:59

Is the item on the left spring loaded? If it is and the index mark moves it could ne for measuring thickness of a elastomeric material under a pre-defined load.

Robert G8RPI.

The Nilfisk will have a "universal" motor (brushed). These will run from AC or DC so an easy way to reduce the speed and noise is to half wave rectify the mains. This just needs a single diode (and a switch to short it out if you want to maintain full speed capability). The diode needs to be 600V and current to suit the motor. A 6A device should be OK A P600J (or K or M) would be a good choice. just connect in series with the live. Direction does not matter.

Robert G8RPI

Edited By Robert Atkinson 2 on 26/01/2019 21:36:35