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Member postings for Robert Atkinson 2

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: Storing Machinery In Damp Conditions - Advice Please
23/10/2018 07:30:38

LPS-3

**LINK**

Not cheap (£12 for a 300ml spray can) but very effective.

Robert G8RPI.

Thread: Safety Switch/Circuit Design?
23/10/2018 07:27:36

You did not answer Bazyle's question, is the foot control ON/OFF or a variable speed control?

Also you imply that the power is going to the "potentiometer" I assume this is a manual control knob fir the speed controller and not an actually carrying power to the motor?

Normal arrangement as said is a momentary start/stop button but this does not directly tie into a pedal control. Having to press a start button each time defeats the purpose of a pedal control (other than as a secondary safety function which is not your case). My solution would be to have an "ARM" button. that enables the footswitch for a limited time. Functionally, pressing the arm button would start a time delay (relay) enabling the foot switch. if the foot switch is pressed within the pre-set time the machine runs and the time delay is reset and starts again when you release the foot switch. If you don't press the foot switch (again) within the pre-set time the foot switch is disabled until you press the arm switch again.

The timer could be an electronic circuit made for the job or a general purpose industrial timer like those made by Omron IMO etc. It could even be a microprocessor like a PIC. An "ARMED" light would be a good idea.

Robert G8RPI.

Thread: 3 phase
21/10/2018 19:05:51

A number of people have commented on the inability to use VFC/VSD on equipment with control gear or multiple motors. While it is true that there are difficulties using the variable speed capabilities due to the associated variation in voltage, there is no reason why a converter / drive cannot be left set on 50Hz 100% voltage to provide a 3 phase supply for such machines. You loose the advantage of variable speed but at least get the unit working. Some converters may need a small fixed load for stability but this could be 3 small lights or heater elements.

Robert G8RPI

Thread: Finger trouble
20/10/2018 11:27:21

Having had a couple of cheap ones shear off when using a DeWalt 1/4 hex battery driver I bought a Wera one part no 870/1

http://products.wera.de/en/bits_holders_adaptors_holders_adaptors_connectors_adaptors_870_1.html

You can also get a set https://www.machinemart.co.uk/p/040212181/

Robert G8RPI.

Thread: How would this lathe tool be used?
19/10/2018 21:42:10
Posted by Hopper on 19/10/2018 07:42:12:
Not really
The radius is more theory than practice.

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.

Thread: which compressor
17/10/2018 15:55:29

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.

Thread: Battery Glue
17/10/2018 15:22:13

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.

Thread: Needle thrust bearings
17/10/2018 14:45:30
Posted by not done it yet on 16/10/2018 17:25:43:

<SNIP>

I don’t think tapered roller bearings are generally designed for excessive continuous thrust - they are only preloaded to a suitable amount so the bearing elements roll rather than skid.

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.

16/10/2018 14:07:39

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.

Thread: Cleaning with Parafin?
14/10/2018 00:04:38

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.

Thread: Multiple vee-belt lathe drive
11/10/2018 13:29:12

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.

Thread: High Voltage influence on a remote control
07/10/2018 11:12:46

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.

06/10/2018 19:50:08

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.

Thread: Perforated copper sheet
04/10/2018 19:39:06

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

Thread: Rocol RTD shelf life
04/10/2018 12:55:23

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.

Thread: Myford super 7 Positioning servo's on Spindle and main infeed
04/10/2018 12:27:48
Posted by Muzzer on 27/09/2018 12:33:58:
Posted by blowlamp on 25/09/2018 13:13:59:

Buy a kit from cncyourmyford.com

Martin.

Wow. £3300 plus painting and a lot of fitting. Pigs and lipstick come to mind. For that cost plus the cost of a Myford you could probably pick up a proper CNC machine and spend your time bringing it back to life, with some likelihood of ending up with a decent machine.

Murray

Plus stepper controller / drive x 2, power supply, case connectors and wiring. I'd have thought the bit's that are selling are the "easy" bits for the average model engineer, and the electrical bit's being more of a challenge.

Robert.

Thread: Help wanted in sourcing sewing machine motor capacitor
03/10/2018 22:57:42

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.

03/10/2018 20:17:05

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.

Thread: How much do Colchester spares cost ?
03/10/2018 07:36:18

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.

Thread: Fly presses - weights and capacity
02/10/2018 21:54:46

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.

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