Member postings for Robert Atkinson 2

Trouble with blueprinting is that the linens will outlast the blueprints. Same for dyeline. Why no cameras? Are they on a secure site? Even then you can normally get permssion for a specific purpose. A camers fixed to a frame for document copying is not much of a security risk. A older "prosumer" DSLR like a Canon EOS 40D can be picked up for next to nothing and will give perfectly adequate results with a a 50mm lens. If you really want to reduce distrortion then a quality enlarger lens is excellent and low cost but a mount would have to be fabricated.

Wide format scanners and printers are still common at graphics and printing companies. Peter aand Duncans comments on scanning are spot on.

Photography is a DIY option. Do it with the drawing vertical on a vacuum hold down box and LED strip lights. Use a digital SLR or similar camera with a good lens (I'd start with a 50mm prime lens). The vacuum box cam be a box (MDF or similar) with a face of perforated hardboard. This needs framing behind to keep it flat. Vacuum from a vacuum cleaner on low is enough to hold a sheet.

V8 comments on contacting the professionals on preservation is also spot on. That said linen and india ink are very durable materials. Mould is one risk.

Robert.

Probably a fault in the unit rather than use of single phase. I'd expect any simple 3 phase VFD to at least power up without any load when powered from a single phase.

Robert.

Machine Mart sell a selection.....

This tool was supplied to RS by Eclipse-Spiralux then Advel. I have one and they did sell M6 and M8 madrels and nosepieces for them. I have a full set. The largere sizes are easier to set than the M3 which is very easy to break.

See photo for some part numbers. The 7488-9500 number is Advel.
https://www.farnell.com/datasheets/884973.pdf

They seem to have been taken over by Zygology http://www.zygology.com

Dave (SOD) said:
" Frequency varies too: the grid originally maintained a strictly accurate 50Hz, but at some point it was realised peak loads can be managed by altering frequency slightly. Now if the system starts to overload, cuts can often be avoided by dropping frequency a little so less energy per second is delivered to consumers. TVs carry on as normal, but kettles take longer to boil. "

Not quire correct. The average frequency is held accuratly to 50Hz. Changing frequency does not change the power consumed by resistive loads like kettles or electronic equipment. Induction motors will change power with frequency but only if the change in speed alters the power consumed mechanically.

That said, the power stations DO vary the frequency of their indiividual generators slightly to control power. This is to control the power supplied to the grid by that particular generator. It may be easier to think about the resulting phase shift controlling the power.

Robert.

Purchasers should remember that VFDs (even the branded ones) are not consumer items. They are not even finished equipment. They are components that are intended to be designed and built into systems or equipment by suitably qualified and experienced persons (SQEP) aka professionals. It is the users responsibility to ensure that they are properly and safely employed. This includes com[lince with relevant regulations.

Robert.

Chris P said "

It is important to realise that not only will an MCB or main fuse not protect you in the event of a lost neutral, neither will an RCD of any sort.

If protecting "you" means against electric shock then a RCD WILL protect against electric shock to "ground" The RCD does not care which wire you touch it only cares about a differentc between live and neutral. The only shock a RCD does not protect you against is if you touch both live and neutral with no significant connection to earth.

The change in the bonding of gas and water pipes is due to a number of issues:
Many more houses having plastic water and gas connections

The introduction of RCDs

Concerns about hazards caused by high fault currents flowing in pipework in the case of a failed nutral in the external supply. The IET are quiet on this as it was a flaw in the orgininal scheme. The house with the best earth could carry the reurn current for all houses on that phase.

Note that is is not a requirement for isolation (yet) just an option not to bond. Personally I think it is flawed as changes to the pipework or even the environment can cause a pipe that wasn't an extranious conductor when tested to become one. For example if part of a pipe is in contact with an earth subfloor or concrete it might pass a test on a dry summer day but become a hazard in wet weather.

ISO42 or 68 is pretty standard and shoud be OK.
Have you considered a VFD rather than single phase motor?

Robert.

SOD said:
" EVs can trickle charge at any time they're not actually rolling: on the drive at home, from street-side charge points, in car-parks at work or whilst shopping. "
That's fine if you have a drive and charging at work. Same for on-street and car parks. There is no public on street charging in the city near me. The local large supermarket has at several hundred spaces but only 6 charging points.

No I'm not anti-EV, just pragmatic. I own a PHEV. I can actually charge at work but with a10kW limit and only If one of the 6 spaces (shared with over over 1000 employees) is free.

Double pole RCBOs are not normally used. Apart from cost they take upe twice the space.

Ex mobilty Fiat Doblo.
Built in ramp and winch....

The supply to the transistors is is via diode D1. They are running from a negative supply with respect to ground. The mains neutral (connected to PNP transistor emitters) is connected to earth at the mains supply.

Robert.

They built a new shopping center in Bournemouth about 20 years ago and had trouble with the car park. The concrete wasn't strong enough and poor design. It was supported with hundreds of acro props for a year or so while they sorted out liabliity and a solution. Lots of pillars and beams added.

https://www.dorsetecho.co.uk/news/5414006.castlepoint-warning-over-car-park-flaws/

What are you actually starting? I guess an IC engine driving a feed pump?
Depending on skill sets, parts availablity, design requirements and compromises gearing or using a different starter may be better options. Typically external starters don't need the engagement solenoid for example.

Robert.

All a matter of scale. The earth leakage trip may be 30mA if the wiring is 0.1 ohms it only takes 0.003V to generate 30mA of current. Triple that for N-E loop resistance of 0.3 ( earth conductor is smaller)ohms and you get 0.009V. A load of 0.1A will generate 0.01V in a 0.1 ohm neutral.

So if there is pretty much any load on the ring connecting neutral to earth will trip the leakage device.

Robert.

Exactly what model starter is it? A photo of the brush gear would help too. It might require slots cut in the cover to allow external links to cross the connections. I have done this before on this type of motor. I did it twice, undoing once, on the back-up hydraulic pump motor used on Thrust SSC. First because the hydraulic designer didn't check the rototion of the parts he bought. It was then undone because the gear type pump could have it's ports reversed instead and then redone because he forgot that the pressure regulation by-pass valve was built in and had to be on the output.....
The brush offset mentioned by Duncan is to compensate for armature reaction wher the rotating fieldcaused by armature current distorts the fixed field effectively moving the optimum brush position. Might cause a bit of sparking at the brushes. You will have to try it and see.

Robert.

Hi,
You need to reverse either the brush connections OR the field connections but not both.
It's normally easier to reverse the brushes.

Robert.

Edited By Robert Atkinson 2 on 08/04/2023 14:03:04

A flame is ionized and thus electrically conductive. The circuit connected to the probe detects the conductivity.

One thought is to use ground shoulder bolts in reamed holes for the main joints. Do inital assembly with the thread size e.g. M6. When all square and level replace one fastener at a time. Drill and ream each hole to to shank size e.g. 8mm. you can re-use the nuts at least. Not super cheap, but no movment in the joints and if disassembled will go back together perfectly. An example bolt:
https://uk.rs-online.com/web/p/shoulder-bolts/0399173
Other and lower cost suppliers avalable but that link is likely to last longer than most.

Robert.