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: Free Electricity|
There is such a thing as free electricity (in the UK). As long as you own an electric or plug-in hybrid car and your employer lets you charge it at work. HMRC changed the rues last year and it's no longer a taxable benefit.
|Thread: Bending copper pipe|
One advantage of Cerrobend is that it expands slightly on freezing making a tighter packing. Lead shrinks. Water expands too, maybe too much.
|Thread: Gold Plating|
Another thought came to me. Electroless nickel immersion gold plating (ENIG) has become popular on printed circuit boards for electronic assemblies. This two layer system will work on brass. If you have a PCB manufacturer near you it might be worth giving them a call.
Well first you need an EPP licence for the potassium cyanide (despite this people still seem to be selling kits on ebay). Have you checked with professional plating services? it may not be as expensive as you think especially if you are not in a rush.
|Thread: Aircraft General Discussion|
Unfortunatly most modern British airships have not been a great sucess commercially, but the Airlander could be. It's a lifting body design that has many advantages.
|Thread: 540 Motor as a generator|
Can you explain this "simple op-amp crcuit" please? Perhaps you mean a boost mode switching regulator. A boost regulator will give you a constant output at higher voltage but there are limits to what it can do.
Cheap chinese version
|Thread: Gatwick Drone 'Attack'|
NO it's not. The police have specifically stated this was not the case and ther were several credible witnesses. Police only flew their drones after the airport was closed. The Air Navigation Order applies to them too.
1/ Why would a criminal register a drone? Limiting supply or sales would be difficult with a global market and even DIY kits **LINK**
2/ You don't need an operator. Drones can be pre-programmed and could be pre-placed on a roof days previously. GPS is not the only navigation option and you can't go jamming GPS at an airport anyway.
3/ If active "man in loop control" was needed then there are various methods that could be used for long distance control.
This is potentially a big problem and there are other variations that could make a drone more of a hazard but I'm not going to give potential wrongdoers any hints.
|Thread: Safety Valve Operation|
The boiler test code 2018 volume 2 section 13.1.5 says
"It is considered good practice that every time steam is raised in a
so sounds like it's not mandatory but I think you would need a good reason not to use a testable valve. Maybe boiler inspector can comment.
|Thread: Assistance asked from Optics Fundi's please|
the graticule goes under the eypiece see page 31 of
http://www.science-info.net/docs/b-l/BL_Stereozoom.pdf (original sales info too)
Microscope service manual including cleaning cn be downloade here
Lots of graticlues cheap on ebay, most from China.
They are a nice 'scope I have one and used them for work in the past.
Edited By Robert Atkinson 2 on 05/01/2019 13:40:04
Edited By Robert Atkinson 2 on 05/01/2019 14:43:36
|Thread: Gatwick Drone 'Attack'|
In reality they don't need additional laws, it's virtually impossible to operate a UAV from a public place without breaching the exisiting law (Air Navigation Order). even if you waited until the area as clear before taking off you can't stop somene wandering into your landing area.
Edited By Robert Atkinson 2 on 04/01/2019 17:51:06
Edited By Robert Atkinson 2 on 04/01/2019 17:51:26
There are lots of options available to a determined wrongdoer. You don't have to use off the shelf devices with known technology. I bought a high speed jet propelled UAV from Holland several years ago
This was pre-gps and could fly a pre-programmed route using internal sensors only. £1200 including the ground support and flight programming equipment.
I'm not going to go into other options on a public forum and suggest others don't either.
|Thread: An electric motor actuated vice|
Not really, you don't know when to stop the motor on a vice, unless there is a sensor which has not been mentioned. In simple terms a stepper motor has good static holding force i.e it resists counter torque. but they are very bad at producing a constant torque output. I guess one option would be to put a spring between the motor and load but you still need a sensor to stop the motor drive. A microswitch activated by the spring movement would work. A DC motor and current limit circuit seems much easier.
That is a different situation your system did not stall, it was slowed to a halt. The drive signal was stopped and the motor is still in sync. In the stall situation the rotor is out of sync with the drive signal and magnetic field. Typically the rotor is stopped (or in Georgineer's case moving in the opposite direction) while the magnetic field continues to rotate at speed. To re-sync the field rotational speed must be reduced until the rotor (and load) can re-align and lock together. If you increase the drive speed on a stepper it will accelerate smoothly to a point and then suddenly stall. There are other factors such as the coil inductance and supply voltage (these lower the current available at speed) but primarilly it's loss of magnetic lock that is the issue.
|Thread: Model engineers - enlisted in war efforts?|
Probably the bigest hobby contribution to WWII was amateur radio. They contributed listening stations from home as well as using their "hobby" for war emplloyment either as radio operators, training, development or manufacturing.
|Thread: An electric motor actuated vice|
Georgineer is correct. When a stepper being driven at speed is stalled it looses virtually all it's torque as the time for the poles to magnetically/mechanically realign is much longer than the time the pole is energised. if ther is an opposing force it has no chance. Before the stall it depends to a large extent on inertia to stay in sync. You have to ramp the speed up and down to get full performance and any resonaces in the system can cause issues. Some stepper systems have intertial dampers (elastomeric mounted balance weights) on their shafts to help with these issues.
Edited By Robert Atkinson 2 on 02/01/2019 20:10:33
If the vice is powerful enough to cause injury then it needs safety precautions. Just because it was good enough in the past does not mean it's good enough now. Old lathes had no chuck guards or zerovolt releases, new ones do, even the new (and most refurbished) Myfords.
If you use a "normal" permanent magnet brushed DC motor this is very easy to do. The torque of the motor is directly proportional to the current so all you have to do is use a constant current supply. As long as the maximum current is less than the maximum continuous current rating of the motor it will sit stalled producing the set torque and automatically take up any slack. You would probably want a geared motor and a ballscrew would be better than a plain nut. Speed is directly proportional to voltage so this can easily be a separate control.
The biggest issue I can see is safety. This is essentially a horizontal press so would need a guard and possibly a two hand operating control. Neither of these are much use for a vice. As the law currently stands you have to be compliant with CE regulations, certainly if using for business or supplying (Inc. giving away) to another party. This means Machinery directive, EMC directive and possibly Low Voltage directive. Note CNC vices operate behind guards.
While your friend may be happy to take the risk, if there was an accident his insurance company may not take the same liberal view and come after you and your house or other assets.
|Thread: USB memory sticks|
Sandisk from Tesco is a good price quality compromise. Ebay and the like is just too much chance of gettng a fake.
|Thread: Simple and accurate home "switch"|
Why silver contacts? Silver is not suited to precision low current switching. It tarnishes for s start. It's not suited to any kind of reliable low level (below 100mA 10V) switching. Commercial index switches are available such as the the Omron D5A but they are not cheap.
I'm not an armchair or shade tree engineer, I'm a chartered engineer who has designed and built motion control systems with 1 micron resolution and 10 micron repeatability. This was confirmed using laser interferometry with nanometer scale resolution.
Edited By Robert Atkinson 2 on 31/12/2018 11:39:32
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