Here is a list of all the postings Martin W has made in our forums. Click on a thread name to jump to the thread.
|Thread: Wow, what a battery|
I note that they say before first use charge for 10-12hrs. If we assume that the unit is supplied in a fairly discharged state, the input charging voltage is 5v, see USB cable supplied, and the output voltage is 5V standard USB then the charge current would need to be something approaching 90 amps. Therefore I suspect that the charging cable they supply must be fabricated from a superconducting material. My problem is that I don't have to hand 100 amp 5V power supply to suit, that said I wonder if Tesla might be interested in the technology as a stack of these 'small' batteries would have the ability to power a car and not take up too much space.
Then it might be that my thoughts may be incorrect and, as Andrew says, the info is just a load of "b*****ks"
John you evidently type faster than me
Edited By Martin W on 04/04/2020 01:13:12
|Thread: What Did You Do Today 2020|
Looks like a nice job Steve. I have been meaning to fit one to my mill but haven't found the right "Round Tu-It" yet, hopefully will do soon.
|Thread: Mystery Sandvik inserts|
That also explains why the table on the back of the packet has been left blank which confused me .
|Thread: How can I remove this mould from painted surface?|
The best product I have used for the removal of black mould and the staining it produces is 'Kilrock BLAST AWAY Mould Remover'. While I don't know what the effect might be of applying it on the painted surface of your telescope I have used on a variety of surfaces including emulsion paints, oil based paints, various plastic surfaces, silicon sealant, acrylic sealants, bare plaster and have not noticed any detrimental effects to any of these surfaces. That said one of its constituents is clearly a bleaching agent similar to normal household bleach probably sodium hypochlorite. Not only does it remove all traces of the mould, including any staining, it also seems to actively inhibit regrowth especially on the more porous surfaces.
It might be worth testing some on a small inconspicuous area to see how quickly it removes the staining/spores and check if it has any detrimental effect on the coating. You can purchase as a liquid spray or brush on gel from various high street outlets or from ebay.
Usual disclaimers other than I have found it to be extremely effective and usually have some about just in case I find some mould about the place.
Hope this helps
|Thread: Bottom of the beginners heap|
You have only got to ask and there are plenty of members of this forum who will be only to willing to help you with any questions you might have. Remember we all started knowing precious little about things but by asking questions and talking to others is how most of us learnt. Also if you don't know the answer then there it is never a stupid question. As Hopper has said post some pictures of your kit and accessories with your questions and you will get answers.
Welcome aboard this crazy ship and good luck.
|Thread: Now is a good time|
Wise words Hopper, no need to say more. I'm lucky to still have my better half after 50 years together but it won't last forever.
|Thread: A very elegant mechanism|
I must admit that I had never considered why I had not seen a slack spider' web. I expect like many others I had just thought that the silk had enough stretch built in to accommodate movement. This is a brilliant and as you say quite astonishing revelation. Thanks for posting it and I shall definitely look at this type of spider's web in a new light from now on.
Here is an extract from the World Health Org site.
"It is not certain how long the virus that causes COVID-19 survives on surfaces, but it seems to behave like other coronaviruses. Studies suggest that coronaviruses (including preliminary information on the COVID-19 virus) may persist on surfaces for a few hours or up to several days. This may vary under different conditions (e.g. type of surface, temperature or humidity of the environment).
If you think a surface may be infected, clean it with simple disinfectant to kill the virus and protect yourself and others. Clean your hands with an alcohol-based hand rub or wash them with soap and water. Avoid touching your eyes, mouth, or nose."
The inference is that touching a contaminated surface carries minimum risk, however if you then touch receptive areas on your face this gives the virus the opportunity to enter the body and cause an infection.
The strange thing about any virus is that it is not, apparently, classified as a living organism as it doesn't consume any form of food and can not reproduce on its own. To reproduce it needs to hijack a compatible living cell by injecting its DNA into it. This DNA then takes over the cell function and forces it to just make copies of the virus. Once the cell can no longer function it then ruptures releasing a vast number of replica viruses, think of the scene from Alien but on an epic scale.
From then on it's up to your immune system to identify the virus and attempt to eradicate it, if it fails then you just become another statistic on the news. The good news is that if you survive the infection the immune system remembers the viral fingerprint and is ready to attack the same virus, the bad news is that virus's of this family can and do change their signatures leaving the immune system in the dark when they infect again. The common cold and flu are typical examples and this is why it is virtually impossible to make an effective vaccine for them.
|Thread: Internet crash|
In view of the above comments regarding potential internet speed problems I decided to run a speed test. I don't think my connection speed had varied much as it is still running at it's normal pedestrian rates of 216 Mbps download and a miserly upload speed 20 Mbps. I will keep a close eye on it and flag up any significant changes regarding the speed thereof.
PM sent re roller cleaning for the MG3200 series printer/scanners.
Hope it helps
And every sheet of that 50,000 tons of Izal paper will have GOVERNMENT PROPERTY printed on it in a precisely specified place and font. One side rough and t'other smooth, rumour had it that it like that to accommodate both male and female use.! Long gone are the five hole planks in the garden privy with the various types of paper hung on a nail driven into the wood. Mind you were never alone with all the insect life that decided this was a good place to call home. Ah those were the good old days.
|Thread: Tooling Choices, identification & WM290 Feed Question|
Kevlar body armour, hard hat, several pairs of safety goggles and you will be fine.
Whereabouts are you, nearest town will be fine, as there might well be somebody local that who could have a look at it and even repair it.
|Thread: WM18 - Broken it again :(|
The fans on these motor are standard bladed fans that are pressed onto the motor shaft and are internally mounted. Change motor direction and this changes air flow direction unlike some of the fans that can be seen on power hand tools etc. which are centrifugal and can shift a lot of air through the motor when running at a reasonable speed
Edited By Martin W on 23/02/2020 10:04:30
If you use a 12V fan similar to those found in computers then a relatively small wall wart psu will be adequate and they are only a few quid each from the likes of CPC or Ebay etc.
Fitting one directly to the motor could be problematical if there is a motor reverse function as then it would be opposing the air flow from the motor. However being aware of this and not running it for extended periods in this mode would mitigate this problem.
While the use of a power meter might give some indication of the instantaneous power and total power being consumed it is far from ideal and can lead to a very false sense of security. Primarily this type of digital power meter is designed to measure sine waveforms, as one would theoretically expect to be supplied by the energy company, and usually makes a good stab at it plus or minus a few percent.
However when the measured waveform deviates from a a near sine wave then the readings can be grossly inaccurate. This can happen when these meters are used to measure the power being absorbed by a phase switched load as the load current is now a chopped up part of a sine wave. Even what are supposed to be 'True RMS' digital meters have a limited form factor for which they are accurate.
The main problem with these and similarly cooled motors is that when run slowly the cooling becomes very inefficient couple that to being fairly heavily loaded and it spells problems. The current is going to be high, as are the I2R (I squared R) heating effects with limited cooling. I suppose a fairly good analogy would be using a car with the cooling system blocked off and towing a heavy trailer up a long and steep hill. Frequent stops to let it cool down and all would be fine but try it in one go and the engine would soon emit a different type of magic smoke irrespective of build quality.
The use of a Power Meter could be a good idea if they were anywhere near accurate when used under these conditions at least one could monitor the total power being used and set a safe maximum time v power limit.
Edit as post crossed with S.O.D. Dave's post
Edited By Martin W on 18/02/2020 11:19:10
Edited By Martin W on 18/02/2020 11:20:13
If these motors are run within their specified limits and duty cycles then there doesn't seem to be a problem with overheating. Again it comes down to price and what people are prepared to pay for a machine. Like most products the features and to some extent quality will be set to meet the minimum standard that customers will accept at a given price.
There are many examples of same problem manifesting itself even on tools supplied by respected manufacturers, a classic example was using mains powered variable speed hand drills at low speed and high loads for extended period of time. Result the same problem damaged motors or hot hands plus magic smoke. I don't whether it is the same now but in the past welding sets used to be issued with duty cycle information to restrict self heating and prevent damage to the machine.
The problem with DC brushed motors is that if they are not turning at a reasonable speed then the cooling fan is ineffective and they can overheat. To stop the Asian kit critics trotting out their usual mantra this is a problem with any motor that is dependant on cooling from a shaft mounted fan when it is run slowly and heavily loaded or as in this case looking as if it was overloaded.
|Thread: Chester DB7 speed control board? NVR switch doesn't lock|
Good news and I hope that they will replace the defective switch without too much faffing about.
|Thread: Fradley Canal Crane Progress|
For them that's interested pictures can be seen here, if moderators think this infringes on IP then please delete.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.