adam2

The voltage rating of a fuse is the highest voltage circuit in which it may safely be used. Use on a lower voltage is fine. 640 volt fuse on a 240 volt circuit=fine. 240 volt fuse on a 640 volt circuit=potentially dangerous. It may be observed in passing that 640 volt circuits are very rare, as are fuses for such a voltage. Might be a typo for 240 volts ? or misread ? Fuses for dimmers should be fast acting, type F. Whilst it is often advised that fuses be replaced "like for like" that presumes that the blown fuse was correct and not what someone had to hand last time.

Use of audio cable for DMX will almost certainly work just fine, and I would not worry about an existing small installation that is working correctly. It would IMHO be preferable to use the correct cable for new or replacement purposes. I have only once experienced a problem with cheap audio cable used for DMX and that was with a most improbable length to some distant LED PARs powered by a car electrical system. It worked fine when tested, but later picked up interference.

My suggestion was that separate lamps and reflectors might replace the large PAR lamps, similar to raylights but available in a choice of beam angles. I don't expect halogen lamps to completely vanish for decades yet, but I do expect that the choice will decline and that prices will rise. A reflector will give more options as to what lamp is used with it. We have all seen the various ways in which the ban on GLS lamps has been evaded. Similar tactics seem likely with halogen lamps.

I suspect that the large, reputable, and well known lamp companies have either stopped production of most theatre lamps, or have stopped listing them in catalogues with a view to ceasing production in the near future. That however does not mean the sudden, total end of availability. In China and probably elsewhere there are factories that can make most types of lamp to order. These may be more expensive or of lower quality than the well known brands. The large PAR lamps may be gone forever. A Chinese substitute consisting of a separate lamp, lamp holder and reflector is a distinct possibility, but a true PAR lamp is very challenging to make in large sizes.

Yes, major manufacturers are steadily cutting back on the range of incandescent lamps. Often due to falling demand rather than a ban. I can remember when GLS lamps came in DOZENS of different voltages, most of which were available in clear or pearl, and in a wide selection of wattages. These days only 110 volt and 240 volt are readily available, and many of the really odd voltages have gone forever. 140 volt, 70 watt and 160 volt 80 watt GLS lamps are no longer available except if someone finds a handful of old stock and flogs them. For a bonus point, does anyone know what they were used for ? Series street lighting bulbs are no longer manufactured. Theatre lamps that are already obscure or in limited demand will likely disappear quite soon, the more popular types might be available for decades yet, but will become expensive speciality items only available from one or two niche suppliers. Carbon filament lamps used to be cheaper than tungsten lamps but are now hugely expensive and therefore hardly used. (excluding so called carbon filament lamps sold on fleabay, that are not actual carbon lamps) I expect that production of GENUINE carbon filament lamps may have already ceased and that those on sale are old stock.

Yes, that is IMHO an often overlooked factor. Years ago when this debate started with the prohibition on manufacture or import of GLS lamps, someone said "theatres will be exempt" and I said "possibly but that wont help if manufacture ceases" Tungsten lamps are going the way of carbon arcs, gas lights, and oil lamps, all of which are still used today for specialist applications but in tiny numbers. I can remember when the local hardware shop sold gas mantles, oil lamp wicks, and replacement glasses for gas and oil lamps. Many of the more popular spares for gas and oil lamps can still be obtained, but only on-line or via mail order from a handful of specialist suppliers and not from a local shop. The end of the incandescent era is within sight. Just as gas lights "went out with the war" at least as regards new installations, and with most existing gas lights gone by 1980. Note that gas lights are NOT completely extinct, thousands remain in use, but not much compared to the hundreds of millions of electric lights. In 50 years time I suspect that tungsten lighting will still be used, but will be as rare as are gas lamps today. I suspect that the more popular replacement lamps will still be available, at high prices and of doubtful quality but still available. Less popular types of electric lamp will probably become completely unavailable.

Also, as the light is reported to be the only one in the immediate area, that might suggest some form of test or trial before installing them on a large scale. That in turn suggests that the council might inspect the sample light regularly to ascertain suitability. Any tampering might therefore be quickly noticed.

Agree, I would strongly advise against any form of tampering with the public street lighting. Especially whilst still new and therefore more liable to inspection, though not a smart idea even if old. If despite this, you are determined, I would try a deep orange colour. There is probably some ancient law whereby you can be imprisoned in the tower of London for this sort of thing though. I HAVE gelled street lights, but only short term to facilitate filming and we did have written permission to do this.

I agree that standard pine floor boards are preferable to large sheets of plywood. Whilst the PERCENTAGE expansion and contraction is probably similar, it is far less of a problem with floorboards since each one will only expand or contract minutely. When fixing the boards, leave very small gaps between them, use pieces of 0.5mm thick cardboard as temporary spacers, removing these as the work progresses. To limit warping, paint both sides of the boards before fixing, the colour of the underside is of no consequence and old, surplus or mixed paint may be used. Worn or damaged boards can be replaced as needed. Plywood can be a disposal problem at end of life, real wood may be burnt in a wood burning stove.

In my youth, I worked for a company that manufactured and serviced radio frequency heating equipment for industrial uses. The power supply for such equipment was typically several amps at several KV. I recall an order for several of the power supply units "with extra smoothing" The input was three phase and the output about 3 amps at about 2,000 volts. The intended application to supply HT to a very large audio amp. That was in about 1975, when valves were still used for some high power equipment.

I bet that members of HM forces can not cook breakfast in a frying pan heated by a skyward pointing LED par can, as has been done with the halogen ones ! I think that there is a photo of this being done

I have achieved acceptable results with a cheap stick welder purchased cheaply DECADES ago ! Just about works from a 13 amp plug, but really needs a heavier supply for serious use. Have also used a large inverter welder for a one off heavy welding job, which proved easier than I expected considering my lack of any formal training in welding.

Series street lighting in use recently. Note the relatively gradual start up as distinct from the almost instant on of a timeswitch or photocell connecting a lamp directly to the supply.

Series lighting as described above used to be more common, but is now largely confined to airfields. Series street lighting was popular in America and IIRC at least one installation remains in use. Series street lighting used lamps rated by lumens and amps, not by volts and watts. Common currents were 6.6 amps and 20 amps. Early installations used no transformers so lamps near the ends of the series strings could have a thousand volts or more to earth. Here in the UK some early street lights were carbon arcs, commonly worked in series strings of 8 to 10 arcs between outers of a 3 wire system. When high wattage and reasonably efficient filament lamps came into use, some street lighting arcs were replaced with 50 volt 300 watt GLS lamps in similar series strings, this saved altering the wiring. The filament lamps burnt for 1,000 hours without attention unlike the arcs which needed daily servicing.

Thankyou for that. We had drifted rather off topic, but at least it was not religious, political, or d0m3stic. Before the last war, many different voltages and frequencies existed in the UK. DC for lighting and power was usually 3 wire at anything from 420 volts to 500 volts between outers, though some 2 wire systems existed. DC for traction was usually 500 to 550 volts for tramways. The Southern railway used 650 volts, later increased to 750 volts. AC for domestic or industrial use used almost any voltage in the 100 volts to 250 volt range and could be derived from three phase or other systems. Frequencies included 15 cycles, 16.3 cycles, 20 cycles, 24 cycles, 25 cycles, 40, 50 and 60 cycles. The government commissioned a report known as the Weir report after the chairman of the committee Mr Weir, later Lord Weir. This recommended that all new small supplies should be at 240 volts, single phase, 50 cycles, with an earthed neutral and usually derived from 3 phase 4 wire systems at 240/415 volts. And that larger supplies would be 3 phase at 240/415 volts also with an earthed neutral. 240 volts was chosen as being about highest voltage already in general use. There was relatively little 250 volts in use. 50 cycles was chosen as being the highest frequency already in general use. There were systems operating at 60, 80 and 100 cycles, but not many. 50 cycles was also about the minimum for d0m3stic lighting. Existing DC systems and non standard AC could remain in use, and minor extensions and additions could be made to such systems, but all new systems were to be at the new standard. Implementation was much delayed by the war, and by immediate post-war shortages of labour and materials, but eventually was achieved. After the war, the 13 amp fused plug system was adopted for d0m3stic and similar purposes. These plugs and sockets were only to be used for 50 cycle AC supplies at 220/240 volts and with an earthed neutral. Where legacy DC systems, or AC at non standard voltages or frequencies remained in use, the older BS 543 plugs and sockets were to be used. The presence of a 13 amp socket was meant to indicate the presence of a standard supply into which a non technical person could pug anything with a matching plug.

DC is used throughout the London underground for traction. London underground used to have, and may still have a 33.3 cycle AC supply for signalling and other purposes. I can remember when this was used for emergency lighting at Earls court underground station. The main lighting was by large modern HID lamps mounted at high level and presumably supplied from AC public mains. In addition, smaller incandescent fittings were mounted at low level (only just out of reach) along the platforms, these used the 33.3 cycle supply. Before the war, London transport owned a large mansion block near Baker Street station. This was supplied from their own 33.3 cycle system and found little favour with the residents as this frequency is rather low for lighting, especially d0m3stically.

The channel tunnel uses single phase at 25Kv nominal for each running line. I presume that a center tapped 50Kv supply is used with the center tap earthed and connected to the running rails. One pole of the center tapped supply to each overhead wire. Thus each track and each train thereon receives a standard 25Kv supply, but the use of 50Kv distribution reduces resistance losses. I would be very surprised indeed if true 2 phase, with a 90 degree phase angle was used on a modern project. True two phase is believed extinct in the UK and becoming rare elsewhere.

True 2 phase systems with a 90 degree phase angle were never popular in the UK and are probably now extinct. Used to be a bit more popular in the USA but now rare. As an historical note, the large hydroelectric plant at Niagara falls originally produced 2 phase, and at 25 cycles rather than the more common 60 cycles. Lower frequencies used to be favoured for electric motors including railways. In Belgium they still use 16.66 cycles for some railways. Frequencies of less than 50 cycles are unsuitable for lighting, especially d0m3sticaly.

The generally accepted international way of describing AC supplies is to list the number of current carrying conductors (excluding protective earths) and the number of phases. as follows. Single phase 2 wire, as used d0m3stically in many places. Also used to describe 2 wire circuits derived from any multi phase system. Single phase 3 wire, as used in the USA at 120/240 volts and less commonly in the UK at 240/480 volt. Sometimes called "split phase" in the UK. two phase should be reserved for true 2 phase systems, with 90 degrees phase angle between phases. Believed extinct in the UK. Still used to a limited extent in the USA. Comes in 3 wire and in 5 wire. 3 phase, 3 wire. Little used in the UK at utilisation voltages. Most high voltage UK systems are 3 phase 3 wire. 3 phase, 4 wire. Widely used for households and light industry throughout the world. Common voltages include 120/208, 240/415, and 277/480 volts. Systems with more than 3 phases are almost unknown. TRANSFORMERS with a 6 phase output are relatively common but are largely confined to feeding rectifiers when DC is desired. 6 phase or any other number of phases beyond 3 is virtually unknown for a distribution system. Note that the "diametric transformers" to which I referred earlier should strictly speaking be called "3 phase, 7 wire" no one does, they are called "6 phase" which is not consistent with the above but is the accepted terminology.

RE post 42, an interesting picture, thanks for posting. Single phase transformers of that size are rare, I don't think that I have ever seen one like it. Two transformers of the type as illustrated would work fine on the same system without needing one to be of reversed polarity. Small transformers of a few dozen KVA capacity with a single phase 11Kv primary and a single phase secondary are very common, they are widely used for supplies to rural homes and farms when either the load does not justify three phase, or when the 11Kv supply is only 2 wire. Large ones are very rare. My earlier remarks regarding the need for one transformer needing to be of reversed polarity, were in reference to old street mains intended for 3 wire DC and the need to supply AC via such mains. This requires that each 3 wire main be supplied with about 500 volts between outers and 250 volts between each outer and the neutral. This requires the use of either a pair of three phase transformers, one with reversed polarity, or a single diametric transformer as earlier described. In theory, THREE of the transformers illustrated in post 42 COULD be used. Connect one third of the existing 3 wire mains to each transformer. Connect the 11Kv primaries so as to balance the load between phases. first transformer between phases A and B, second one between B and C and the third one between A and C. Never heard of this being done though.

Surely they are identical transformers.Wouldn't one merely reverse the secondary winding (or primary).Having said that I would guess it would be less messy to use CT transformers which will achieve the same thing. In principle, yes, but in practice reverse polarity transformers require special manufacture. A standard substation transformer has three HV windings that are permanently connected in delta at the works. This requires but three HV connections and not the six that would be needed if each end of each winding was accessible. The transformer also contains three LV windings that are permanently connected in star at the works, there are only 4 external LV connections, the neutral and the three phases. Commonly the bottom ends of the three LV windings are connected together and form the neutral, and the top ends of the three windings are connected to external terminals for the three phases of the output. To manufacture a reverse polarity transformer, Either the top ends of the three LV windings are connected together and form the neutral, with the bottom ends forming the three external phase connections, OR ALTERNATIVELY the 3 LV windings are wound in the opposite direction. For small transformers as might be found within appliances, it is usual to make each end of each winding accessible in the interests of flexibility. Substation transformers have as many connections as possible pre-made. They cant easily be altered afterwards, remembering that we are talking not of wires but of substantial copper strips. Center tapped three phase transformer do exist and are used, usually known as "diametric transformers" they achieve a similar result to the pair of transformers. DNOs also keep small stocks of these specials. A diametric transformer has three HV terminals and seven LV terminals, neutral, the three phases and the three antiphases. Diametric transformers are "very non standard" whereas the reversed polarity transformers are a relatively minor change on the production line from standard types.

The two transformers referred to above were probably not truly identical. One would be a standard type, the other a special with reversed polarity. Each with a 3 phase 4 wire output. The three phases of the standard transformer would be called red, yellow, and blue in line with accepted practice. The three phases of the reversed polarity transformer would be written as red*, yellow * and blue* or in the spoken word referred to as red antiphase, yellow antiphase, and blue antiphase. Existing street mains originally intended for three wire DC would be connected one third between red and red*, one third between yellow and yellow* and the rest between blue and blue* The neutrals of both transformers would be connected together and earthed, the center conductors of the old 3 wire mains would be connected to this neutral. Each 3 wire main therefore had 250 volts between either outer and the neutral, and 500 volts between the two outers, reducing to about 240/480 volts on load. Smaller consumers would be connected one outer and the center or neutral wire and would thus receive a single phase, 2 wire supply indistinguishable from any other standard supply. Larger consumers would be connected to Both outers and the neutral and get a 3 wire supply at 240/480 volts. By convention, in the consumers installation, the two poles of the supply are identified by red and blue, no matter to which phase it may be connected at the substation. A minor drawback of this system is that if both poles of the supply are used, then switchgear, fuses and circuit breakers need to be rated for 480 volts rather than the more common 415 volts. Most industrial HRC fuses at rated for more than 480 volts, but a lot of cheap MCBs are not. The other drawback is risk of a prolonged outage if the reversed polarity transformer fails. Normally failed transformers are handled by backfeeding at LV from adjacent mains on different substations, cant do that with reversed polarity and 3 wire mains. DNOs still keep a small stock of reversed polarity transformers in case of failures, but delivery from a distant stores department, crane hire and cable jointing are unlikely to be achieved within 3 hours.

As has been said there is no law in the UK that specifically prohibits the flying or showing of a noose. I would still advise great caution to avoid potentially fatal accidents. Don't leave it lying around, lock away or untie it when not in use. Consider suspending the noose in a non loadbearing way. Warn all cast and crew that NO horseplay or fooling around of any description whatsoever is allowed with the noose. Accidental strangulation still results in loss of life regrettably often even without a "proper" noose. Dressing gown cords and straps on school bags becoming looped on bunk beds or bannisters seem to feature all to often. A "proper" noose would seem to be a still greater risk.

Yes it is a very old thread, bumped to the top by an advert, which I reported and which was soon deleted. The question asked and the replies thereto are still relevant today.

Cutting a thread in plywood is unlikely to work, well. For fixings INTO plywood, wood screws are almost certainly best. For fixings THROUGH plywood then consider a suitable bolt or machine screw with washer and nut on the back.