indeed - but I suspect that many of today's builds will probably collapse/disintegrate/whatever a lot quicker than did most of those built a century or two ago!Just like some of today's builds them
Kind Regards, John
Drums? Of cable
- Thread starter RF Lighting
- Start date
Kind Regards, John
I'm sure that's right - it's certainly the term I would normally use. However, one does also see the word "drum" being used - although, I think, most commonly in relation to cables far larger than one would see in domestic/commercial installations.
I think that, in some contexts, the word has been used over the years to refer to various cylindrical containers. For example, I seem to recall that, a long time ago, we talked about "drums" of table salt - and, now, "drums" of cable clips etc.
Kind Regards, John
And then there's drums of hum otherwise known as humdrum
just as a side note, in America most of the smaller lighting/power cables are supplied as coils rather than on drums/reels.
If you have a large quantity - especially a long length, then "drums" or reels cease to be practical. Data cables, such as the Cat5e and Cat6 network cables I deal with most come in drums or boxes - the boxes are wound in such a manner that the cable can be pulled out from the inside of the pack. Boxes are by far the most used form of delivery for these cables, and in some ways mirror the use of tanks for long submarine cables.
As an aside, at my last job I used to choose 500m reels instead of 305m boxes when we were doing a lot of office expansion. This was a matter of economy, since when pulling long runs, you ended up with more "left over" using the shorter length in the boxes. But, getting 8 reels all going at once took a fair pull, and more importantly, needed careful slowing down to avoid a rats nest - and it took a bit of strength to load 8 full reels on one pole (bit of 2" pipe left over from the sprinkler) and lift it onto the improvised stands.
But back from the diversion. A few years ago locally we had a talk on submarine cables (specifically the first transatlantic cables), and later a visit to a cable laying ship when she was in the local docks. it was during the ship visit that the chap was explaining the process whereby they would moor up - sometimes at the cable factory - and (up to) a few thousand miles of cable would be taken on board (potentially in one piece having been factory joined). The free end would be kept accessible - allowing the cable to be tested at frequent intervals during laying. Then a loop would be passed down into the tank so the cable goes down the inside of the outside of the tank and is then laid in a spiral on the floor - working inwards. At the inside, the spiral reverses and works outward on another layer. For cables with repeaters already factory fitted, the cable is looped out of the tank so the repeater can be stored on a rack and then back into the tank so coiling can continue.
What the guy did point out is that the laying up of the cable was done by hand. Whoever was doing it would wear soft soled shoes, and walk round and round as the cable came down into the tank, making sure it laid up properly. Turns were short - I think he said few could do it for 2 hours in one go before getting completely dizzy !
Laying the cable then was "simply" a matter of reversing the ship close to shore and paying out enough to reach the shore station, then setting sail and paying out the cable in a controlled manner.
In a similar manner, fibre optic cable (especially the smaller "blown fibre" cable) is generally handled in "pans" - same as the tanks on cable laying ships, but smaller ( around 4 foot across ?) and shallow. Again, cable is typically removed by simply lifting the free end vertically thorugh a ring in a frame above the pan. There is a similar but different process used here.
Unlike a subsea cable where typically the cable will be laid from one end, or perhaps two ends and joined in the middle, a fibre run may be many miles but the blowing technique doesn't work that far ! The actual distance blowable in one run varies with cable and duct size, and a few other factors. But lets say you can blow 250m and have a 10km run to install - how do you do it ?
Well you start with 10km (plus a bit) delivered in one pan. You go to roughly the middle of the run and start blowing fibre down the tube - measuring what you've blown as you go (the equipment has an odometer on it). When you've blown enough to reach the end in that direction you stop - and hopefully at the next duct joint there is now 5km less 250m (ie 4750m) neatly coiled up in a pan, if not the person responsible for it really cocked up and you start again !
So you put a second pan upside down on top of the pan holding the fibre, and flip them over. You now start blowing again, throwing the 4750m down the tube - and if it all works out you end up with a small loop which you carefully bow down until you can clip a joint on the tubes to fix them together. And hopefully, 250m down the road you now have 4500m in a pan. Keep repeating until you reach the end, then go back to the middle and start blowing the other way.
This all relies on laying up the cable in a spool in a tank or pan, but at the end of it you can install an effectively unlimited length (certainly much longer than the length you can blow in one go) of fibre with no joints.
And on another diversion ...
I gather that in cinemas (at least those still using proper film), it's common to join up everything into one reel of film - the main feature may be delivered on perhaps 12 reels in order to be manageable. That way, there's no breaks for changing reels*, and the projectionist just has to switch on at the start of the program and off at the end - which can explain why problems can take a while to deal with, if someone has to find the projectionist when it's a nice evening to sit in the sun on the roof
With 70mm film as typically used in cinemas, all that is a lot of film - and it weighs a lot. While it is possible to hoist this up and mount it on a horizontal spindle, they actually normally coil it up on a horizontal turntable. The start of the film is then drawn from the inside of the coil, passed through the projector(s)**, and then coiled up on another horizontal turntable - neatly also avoiding the need to rewind the film between showings.
* Back at college, three of us got practiced enough to change reels on the 16mm projector the film club used without stopping it and with only something like a 10s break. In fact, at least one person refused to believe we didn't have two projectors. Mind you, being an autoloader did help "quite a lot".
** If showing the same film on multiple screens, they would just run the film from projector to projector via pulleys - so one film print multiple screens, just a few seconds delay between them.
You'd struggle to pull t+e from a box! Small flex or singles might work but drums/reels are the only way for anything bigger than CAT6.
Prysmian put their T+E on a drum in a box and the box lasts about 5m
Prysmian put their T+E on a drum in a box and the box lasts about 5m
I thought that they used (at least, used to use) dual projectors, used alternately, and were very clever at synchronising when to start up 'the next one' so that the changeover was 'seamless' (hence, hopefully, not noticeable)?
Kind Regards, John
It's been quite a few years since that was done, the film is joined and is run from a large platter. Less work to do, and the film can be run through several projectors one after the other. There is also no need for short runs to allow for replacing carbon arc electrodes with widespread use of xenon short arc lamps.
How many cinemas even use film any more? The two local to me, at least, are all Sony 4K digital now
I don't know, but how boring is digital compared to proper film. I remember when I was younger at a small cinema and the film breaking in the projector, you don't get that sort of excitement now!
Quite, and the absence of the 'flammability' issue must make for much less potential excitement for the projectionists!
Kind Regards, John
You certainly don't get the flecs of dust and hair on the projection like you used to!
I'm not particularly nostalgic when it comes to old storage mediums, they fell out of favour for a reason.
I do miss the MiniDisc though, shame that never really took off, that was a good format.
I'm not particularly nostalgic when it comes to old storage mediums, they fell out of favour for a reason.
I do miss the MiniDisc though, shame that never really took off, that was a good format.
Indeed, but the technology has rushed ahead so much that it's getting a little silly in relation to temporary storage/transfer of 'small' (by today's standards) digital data. I frequently have the need to transfer files totalling maybe a few dozen MB (upo to a small number of hundreds of MB), sometimes less, in situations in which transfer methods using the internet are not appropriate, acceptable or possible. A CD is around 700 MB and, although one can still get 1 GB memory sticks, 8 GB ones are often cheaper. I almost cry each time I put an 8 MB stick in the post which has, say, 100 MB of data on it
Kind Regards, John
Yea, the effort+time involved in burning a CD/DVD make up for that though. You should just get a bulk order of 1/2GB memory sticks from china for about £1 each then it's less painful.
I have removed all optical drives from both my desktop and laptop to make more room for hard drives. I have something stupid like 12GB in my desktop across 6 drives. (Ordered 2x3TB WD drives from amazon and by mistake they sent me 1x3TB and 1x6TB, I was mighty pleased)
I have removed all optical drives from both my desktop and laptop to make more room for hard drives. I have something stupid like 12GB in my desktop across 6 drives. (Ordered 2x3TB WD drives from amazon and by mistake they sent me 1x3TB and 1x6TB, I was mighty pleased)
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