Member postings for Robert Atkinson 2

Maybe for model engineers, but there have been cases of wings folding on aircraft (e.g. Tiger Moth) due to threads on replacement tie bars not being formed correctly.This causes stress concentrations and fatigue cracking.

Robert.

Fridge compressors ar good quiet option but fairly low flow. A few things to watch out for though. They are normally lubricated by oil in the closed system so you need libricator on the inlet. Not a problem with running engines or misters but you also need a cleaner on the tank outlet for other uses.
They are capable of very high pressures if left to run on their own. A pressure relief device on the output is a must.
It is illegal to relese the gas from a fridge so either buy a new compressor or get a qualified company to de-gas the fridge for you.

Robert G8RPI.

Normally plastic battery cases are heat (friction, ultrasonic) or solvent welded. The join around the different materials of the teminal posts may use adhesive. I'd suggest standard (not rapid) Araldite epoxy. This has reasonable acid resistance so should be OK if not immersed.

Apart form the conditional "excessive" (nothing is designed for excessive anything by definition), this is incorrect. One of the principle reasons for using TRBs is their ability to accept axial and mixed loads. The only conition is that a single row can only accept load in one direction.
It's the taper on the rollers that allows them to roll without skidding.

The thrust bearings called up are NTA 411 which are indeed needle roller type. https://www.motionindustries.com/productDetail.jsp?sku=00094460

To answer the original question, yes there will be some skidding in this type of bearing, so a drop of oil is a good idea, but it is obviously far less than the friction between two flat surfaces. The NTA 411 is rated to 26,000 RPM at 522 kg force so I think it will be OK on a cross-slide

Robert.

Parrafin and Kerosine are just different names for the same thing. White spirit, also known as Stoddart Solvent, is a more refined version. In the USA and Canada it;s called Mineral Sprits. A lot of barbeque lighter fluid is refined or de-odourised kerosine. There are various grades of all of them.

The stories about water in parrafin are old wives tales, based on the fact that parrafin heaters cause lots of condensation. When you burn a hydrocarbon like parrafin, water is created from the oxygen in the air and hydrogen in the fuel. You can dissolve a tiny amount of water in parrafin but it's insignificant, you will get more water condensing onto cold metal than from cleaning with paraffin.

Correct way to dispose of used parrafin etc is to take it to your local recycling center and put with the paint or used oil.

I agree with Howard, not a problem. Hundreds of helicopters use multiple V belts to transmit power from the engine and act as clutches without significant issues. See https://www.atsb.gov.au/media/4120236/ai-2009-038_final.pdf for an interesting investigation (The R22 uses double V belts but otheres use multiple singles or polyvee. Theis service note even gives instructions for gluing down loost strands at the edge of the belt!
http://enstromhelicopter.com/wp-content/uploads/2012/03/SDB0117R2-Drive-Belt.pdf

Most main dealers would be trying to sell you an new alternator belt for you car if they saw that level of dmage.

Robert.

A 50Hz field should not affect a UHF receiver if it has any kind of tuned front end, which it should. It is possible that the 50Hz field is gettinng into the control wiring and causing issues.

It easy to find out if it's radio or wiring interference by halving the distance between the remote tranmitter and the tower for some tests. If it works at half the distance the problem is RF interference not 50Hz.

Robert G8RPI.

Hi,
The field the chart you refer to is that generated by the 50Hz power. This is not what is causing the interference to the remote control which will operate on a much higher frequency. The interference will be caused either by arcing / corona on the line due to faulty insulation or, less likely, radio signal being transmitted on the lines.

The answer is to move the antenna (or receiver and antenna) closer further from the lines and closer to the transmitter. How yuo do this deends on the type of antenna. If it plugs into a coaxial connector you just need a coaxial extension cable with male and female connectors to match. If it's just a bit of wire it may be more difficult.

Moving the antenna 20 ft from he line will reduce the intereference by a factor of four.

Another option would be to use a directional antenna. A reflector plate behid the existing antenna mightt work but it depends on the frequency and the type of existing antenna. Do you have any information on or psctures of the receiver / antenna?

Robert.

Look at a laser cutting firm like LaserMaster not only will they cut the holes in plain sheet they will cut the outline shape too. You could even try fancy hole shapes or patterns. Cost is generally quite reasonable.

https://www.lasermaster.co.uk/materials/brass-copper

Robert

Some of the early explorers suffered from lead poisoning caused by the solder used to seal the tins. I have some ex US military MRE (Meals Ready to Eat) that I've had for over 20 years (traded a polo shirt for 3 boxes in the Jordanian desert) the outer boxes specifically said that they did not need refrigeration and had no expiry date....

Back on topic I've also had a plastic bottle of drilling fluid (not Rocol) split in storage and leave a sticky mess.

Robert.

If the OP's component is connected across the mains (L & N) then it should be a class X capacitor (this is what I think it is). If it's connected across the switch a snubber would be more appropriate.

Robert.

The component Neil mentioned is called a Snubber. It limits the rate of change of voltage across a contact (or electronic switch like an SCR). While not a EMI suppressor per se, reducing the rate of change reduces the EMI.

Robert G8RPI.

I know of a current large machine where a complete subsystem is supplied to the machine maker free of charge and the subsystem manufacturer makes profit purely on spares. There are no routine replacement or "wear-out" parts in the system. Hardly a model for making reliable machines. The accountants must love it.

Electronics has gone through a huge obsolescence period of the last several years. Banning lead, corporate takeovers and changes in packaging for has lead to devices that were common disappearing from stock virtually overnight. It's a big issue for industries with long product life cycles like defence and aerospace.

If you want expensive nuts try buying aircraft ones.

Robert.

Unless you have a very good reason to want a flypress I suggest you consider buying or making a hydraulic press. The only advantage of a flypress is speed and compared to a simpe frame an open working area. The downside is they are heavy take up a lot of space and are dangerous. If you don't crush a finger you will at least bang your head on the handle. A frame made of U section structural mild steel and a hydraulic jack is all you need. Compact, powerful, lighter (and can be dissasembled to move o store) make the cross mean movable and you can fit taller items in.

Robert.

Those sums look about right, a bit less than 4kWh or about 55 18V 4Ah batteries for the run.

What this does not include of course is the much larger amount of energy needed to raise the water to boiling point in the first place.

Robert.

AC still electrolyses the water, it just swaps the anode and catode around so you don't erode the anode.
It's not unsafe s long as the case is well grounded. Early designs of electric water heares and showers had a bare resistance element immesed in the water.

Robert.

A few calculations shows it's impractical.
Firstly the battery rating is misleading. 20V is the off load fully charged voltage, not the rate voltage which is 18V. (Dewalt tools in the USA are "20V" but the same tool in Europe is 18" due to consumer laws.) So using the correct rating 18V x 4Ah = 72Wh a watt is one joule per second so thats 72 x 3600 = 259.2kJ (about the same as 6g of coal) Specfic heat of water is 4.186j/g or 4.186kJ/l so our battery will raise 1 litre of water 61.9 degrees or from 20 to 81.9 degrees (at ses level ambint pressure)

Even if you start off at boiling, the heat of vaporization of water iss 2261kJ/kg so a fresh battery will boil away 115ml of water.

Robert.