| Author | Message | ||
     Graeme Söderlund Frequent User Username: graemeaus Post Number: 26 Registered: 6-2003 |
Hello again, Technical Experts. The handbook tells me that we should be using 30 SWG tinned copper wire, with a 22 amp rating. Can anyone tell me where to buy it? My enquiries have resulted in being told to use general household fusewire (which only comes in 8 amp or 15 amp ratings). Am I being pedantic in trying to stick to what the handbook tells me? I haven't been able to refer to my workshop manuals since I moved (they were packed safely into a box, one of about 30 and most of which are still to be unpacked!). I would appreciate any suggestions re Fusewire. Regards, Graeme. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 127 Registered: 4-2003 |
Household fuse wire will do fine. For most fuses, 15A is fine, but where a higher rating is required, twist 15A and 8A thoroughly together. The rating will be slightly less than 23A as the load sharing is not perfect. However, by twisting the wires the load sharing is optimised. | ||
| Bob UK Unregistered guest Posted From: 195.93.33.11 |
There are two ways of rating a fuse. continous and surge. I know these as slow blow and fast blow. I think household is continous and 15 amp is about 22 amp surge. I don't know which type of rating RR use. Fuse wire is available also from radio stores. Radio stores have a better selection of fuse wire for diferent applications. A tip when working on car electrics. I put a temporary fuse between the battery and the main fat lead. So that if I make a mistake while live the fuse pops. Also the engine won't start because the starter will pop the fuse. I use 2 wander leads attached to 2 nails in a bit of wood with fuse wire twisted around the nails. Also I have used a fine strand(s) of wire as fuse wire. On real fussy stuff you can use a micrometer and charts to work out the exact rating. With cars the fuse ratings are not that precise. For instance indicators --- 21 watt x 2 plus 5 watt repeater. 47 watts total will use 3.5 amps continous. -- at 13.5 volts ---so allowing for surge 6 amps. ( they surge every time they flash ) But 6 amps is not a standard value but 8 is. In any case designers will have say the stop lamps on the same circuit so they fit a 15amp. You don't always use the stop lamps and the indicators together so when braking the fuse protecting the circuit has 4 times the rating actually needed. Any dead short will pop the fuse immediately. The conclusion I have is that providing the fuse wire is within say 10% then it will be fine. ERR on the thinner side. Automotive glass fuses are usually marked continous. These are getting hard to get. I have soldered fuse wire across glass fuses for quick reliable repair when I can't get one. My van has those ceramic fuses which are the worst type. Rewireable are the best. Most expensive to make but cheapest to replace. | ||
| William H. Trovinger II Prolific User Username: bill_trovinger Post Number: 77 Registered: 8-2003 |
Graeme: Try eBay this item is running for another 24 hours and is in geniune RR/B packing. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2461635181&category=10076 | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 128 Registered: 4-2003 |
Fast fuses are usually encapsulated in sand in a ceramic cover. They are usually superior, but not really necessary on automotive 12 Volt applications. Cars generally have intrinsic protection through cheap and light high impedance wiring looms, with the impedance as high as the manufacturer dares (note the slow electric windows on many of our cars as a result). The best known fast fuses (used for example in semiconductor protection) are HRC (High Rupture Capacity) fuses. they are rated by I squared - t (basically the area under the current vs time curve) as well as a continuous current rating. They are carefully designed to rupture before the semiconductor or other device is damaged, a practice called discrimination. It is not the level of current which blows the HRC fuse normally, rather the rate of current rise. Normal slow-blow fuses are usually encapsulated in clear glass with one end of the conductor tensioned by a spring. Shadow fuses are mostly very ordinary fuse wire types and no special attention is necessary. Early SZ cars used Bulgin clear glass encapsulated fuses, and later cars used the common-or-garden Littel fuses as used by most manufacturers. Having said all this, as with all fuse applications it is most important not to mess around with the type or rating except perhaps just to get you home. Always keep an assortment of fuses in your fusebox as spares and you will never get caught out. Post war cars before the SZs even came with a supply of spare fuse wire in the fusebox, and later cars had severl spare fuses mounted on the fuse panel. | ||
| David Gore Moderator Username: david_gore Post Number: 203 Registered: 4-2003 |
Thank you everyone for sound practical advice - The use of a 15A/8A made-up composite wire fuse as a replacement for the factory-specified 22A wire is the most practical solution however I suggest as circuit breakers are fast replacing wire fuses for household use; it is the right time to buy a number of fuse wire cards and put them away for the benefit of future custodians of your car. I have just returned from buying out "Supa Cheap Auto" Rockdale's stock of 1AG 10AMP Bulgin fuses for a Finnish owner who cannot obtain these in Europe as well as providing future supplies for DRH14434 after I "bite the dust"!! I still have some original 22A wire on the bobbin in the fuse panel so will check the cross-section against some 25A rated household fuse wire I use for property maintenance and will post this information later this evening. | ||
| Graeme Söderlund Frequent User Username: graemeaus Post Number: 27 Registered: 6-2003 |
My thanks to all who offered so much good advice re fusewire. I guess I can be a bit pedantic when I go to a shop and am told that "sorry - that isn't made anymore"". I specifically took down all the details from the handbook and insisted that that was what I wanted - didn't get it though! I will try the twisted pair method and see how we go. The car hasn't come to a shuddering halt, just that the clock etc is not working and it is a nuisance having to open the boot each time I want to fill up with petrol. Special thanks to Bill Trovinger for the advice re e-bay. David, your comments re the Finnish situation & Bulgin Fuses reminded me to go get some. I bought the last four packs from the local Super Cheap and will need to go find more on the weekend to keep in stock for when I pass the car on to its next custodian. I guess I will have to ensure that there is a supply of "consumerables"" as country New South Wales doesn't have many Rolls Royce afficionado's. Regards Graeme. | ||
| David Gore Moderator Username: david_gore Post Number: 204 Registered: 4-2003 |
As promised, here are the dimensions of the R-R standard fuse wire and equivalent Australian Standard domestic fuse wire: 22Amp rated R-R fuse wire: 0.325mm diameter 8 Amp rated domestic fuse wire: 0.315mm diameter 16 Amp rated domestic fuse wire: 0.5mm diameter 20 Amp rated domestic fuse wire: 0.6mm diameter 30 Amp rated domestic fuse wire: 1.31mm diameter These results suggest Bob's comments re the automotive wire being rated on surge current rather than continuous current is correct. Accordingly, it appears a single strand of 8 Amp continuous rated domestic fuse wire is equivalent to the R-R standard wire and a combination of 15A/8A wire as I suggested above is well above specification. Time to make up a test circuit and blow some fuse wire I guess!!! | ||
| Bob UK Unregistered guest Posted From: 195.93.33.11 |
Warning from an electrical expert mate. The explianation I didn't understand. But using circuit breakers instead of fuses on low volt systems is not a good idea unless the breaker is backed by a fuse or fusable link. Radio Spares --- RS have a very large mail order department and web site. Ask for a catalogue. The one at work is 8 volumes of about 500 pages each. The glass cylinder fuse is going to be around for many years to come because it is cheap simple and does the job well. And is used on many other things besides cars. As for fuse wire once you know the dia you need then any old bit of copper wire will do the job. This information will be in any electrician's data book. Count our selves lucky because some of the modern fuses I find on cars are £2 each. Check stray strands on rewirable fuses you can short out to another fuse and cause weird things to happen | ||
| David Gore Moderator Username: david_gore Post Number: 205 Registered: 4-2003 |
Thanks Bob and you have misunderstood my reference to circuit breakers - I was detailing the fact that demand for fuse wire is mainly for household use not automotive and the use of wire fuses in houses is rapidly decreasing due to the benefits of breakers. Accordingly, availability of fuse wire for automotive applications will diminish as retailers stop stocking a product with little/no demand. 1AG glass fuses are almost exclusive to British/early post-war Australian cars and whilst they are still available at least here in Australia; these will also disappear from retailers shelves due to slow sales in the future. Current cost for these fuses is AUD4 for a pack of 5 fuses. As a matter of interest I purchased a stock of 12V 1W LES [Lilliput Edison Screw] bulbs used for the switchbox/wiper switch illumination at 68 cents each yesterday [for Australian owners, these are available from Dick Smith Electronics as part number P8159]. | ||
| Graeme Söderlund Frequent User Username: graemeaus Post Number: 28 Registered: 6-2003 |
Further Fusewire information. I have found the following information in the FARNELL catalogue.(Farnell Components, Wetherill Park NSW, and the Newark Catalogue USA - same thing). I have included the Newark reference for Will Trovinger and other US browsers. Newark & Farnell use the same part numbers/same stock. Both list TINNED COPPER WIRE, suitable for shorting links, discrete wiring, PCB track repairs etc. Conforms to BS4109. SWG 35 at 5A, 250g reel part no 301-882 AU$15.26 SWG 25 at 15A,250g reel part no 301-814 AU$13.85 SWG 24 at 17A,250g reel part no 301-826 AU$27.74 SWG 22 at 24A,250g reel part no 301-838 AU$26.16 I am no technical expert, but I feel the 22SWG, 24a would be suitable for the cars. David, would you agree with this assumption? Some of the Techo's that I work with in the Aviation Industry felt that the 24A would be suitable, and would provide a better fusable link than a twisted pair. Will await comments. Graeme.} | ||
| David Gore Moderator Username: david_gore Post Number: 206 Registered: 4-2003 |
Graeme, Thanks for tracking this supplier down and will be purchasing some wire when I am out West next week. I am on a stocking-up kick at the moment to provide sufficient consumable part supplies for future custodians of our car. I just hope they resist the temptation to turn the stock into cash when supplies run out! I agree with your adviser's comment that a single wire fuse is far preferable to a twisted pair fuse from a reliability and accuracy perspective and the 22swg rated wire is within the acceptable [to me anyway] tolerance for the factory specified 22A rating. | ||
| Gabriël Viljoen New User Username: gabriel Post Number: 4 Registered: 3-2004 |
When purchased, my 1971 Silver Shadow had on some places more than one strand of fuse wire, up to three wires are twisted together on some of them. Is this correct, or should each of the black plastic linkages in the fuse box only have one wire on them. Is all of the small glass fuses 10 Amps, or do they vary? | ||
| Mark Tomlinson Frequent User Username: mark_tomlinson Post Number: 19 Registered: 9-2003 |
Gabriel, As you are looking down on your fuses you can pull out a metal plate from the bottom of the fuse panel that will explain what each fuse is for and the load rating it should be. | ||
| Bob Reynolds Frequent User Username: bobreynolds Post Number: 70 Registered: 8-2012 |
Just digging this topic up from the past.  I have the fuse board out of my SS1 on the bench at the moment, and am renewing all the fuses and diodes, etc. There seems to be a lot of conflicting information in this thread. The conclusion seems to be to use 22SWG for the wire fuses. But RR clearly specifies 30SWG wire. This is only 0.315mm in diameter, whereas 22SWG is 0.71mm diameter. That's a BIG difference is cross-sectional area. Also, the grooves in the fuse holders are not really large enough to accommodate 22SWG wire properly. Yes, you can make it fit but it is too big to wrap around properly. It is clear that the fuse holders were not designed for 22SWG wire. Now, if I fit 30SWG wire I am concerned that it is only rated at around 8 amps according to the table above. Are these fuses going to keep blowing? Yes I know I could just fit the 22SWG wire anyway, but it's clearly not the right size. I just wondered what other members used. And the second question: Is there a (UK) supply of the small 10A glass fuses? I have found a supply for the large 30A ones. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 758 Registered: 6-2009 |
Bob, Although I can't tell you if there's a specific supplier in the UK for the 10A fuses, I can tell you that they're still readily available online. The size in question is AGA (also known as 1AG). Ideally you'd want AGA/1AG 12V 10A, but often you'll find the voltage rated higher which, it turns out is OK. You can read up on that on the Cooper Industries Fuse Selection Page. Every AGA/1AG fuse I've found so far has a 32V rating on its data sheet. I've found AGA/1AG 10A 32V fuses at waytekwire.com. I presume our cars use fast-acting fuses, but have never been able to nail down whether the original Bulgin fuses are fast-acting or time-delay. I haven't had any of the replacements I've used, which are fast-acting AGA fuses, blow. Brian | ||
| Bob Reynolds Frequent User Username: bobreynolds Post Number: 71 Registered: 8-2012 |
Thank you Brian, helpful as ever. Yes the voltage is irrelevant, it's only the current that matters. In fact I'm struggling to understand why a voltage is quoted at all. As for the wire fuses, I'm going with 25SWG, which is in between the 2 sizes mentioned above, will fit the holders better, and seems to be the thinnest size of tinned copper wire which is readily available. Yes, your simple wire fuses will be fast acting. Slow blow fuses usually have a spring in the middle and a blob of solder. The solder heats up relatively slowly and breaks the circuit when it melts. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 761 Registered: 6-2009 |
Bob, Well, somehow voltage is relevant, since they tell you that it's fine to use a higher voltage fuse with the amperage you want in a lower voltage situation but not the reverse. I think the example is that it's fine to use a 32V 10A fuse in a 12V application but not alright to use a 32V 10A fuse in a 125V application. I hate electrics in general, but believe the advice I receive from my EE friends and the device manufacturers. Brian |
