| Author | Message | ||
     Bob uk Unregistered guest Posted From: 94.197.122.77 |
Standard thinking is that discs are better than drums. This ain't necessarily so. Because drums have a massive advantage of wrapping. Which is similar to drilling through a blanket, the blanket will wrap around the drill. The self servo action is very powerful. Twin leading shoe brakes don't work well in reverse. The selfservo action works when the drum is static so handbrakes are powerful. Tip If more handbrake grip is needed use foot brake to force shoe against drum and use handbrake to lock the shoes on. Best set up for brakes all drum is twin leading shoe front and single leading rear so that the brakes work in reverse hand brake to the rear. Which is many old car designs. But they are prone to fad and need adjusters. Disks are not so prone but have no servo action and there fore liable to be heavy. Static grip is not so good. Handbrakes are weak. Where the handbrake works through the main caliper the tip above works. The best system is maybe merc and Volvo 4 discs drum hand brake. Simple reliable robust. Add RR power circuit. Would a Shadow be ok with drum rear brakes. The Cloud is the answer. But no doubt RR would have tried it. And maybe it's a case of keeping up with competition who knows. Opinions welcome. (Message approved by david_gore) | ||
| Jan Forrest Grand Master Username: got_one Post Number: 580 Registered: 1-2008 |
IIRC Rolls Royce were so 'late' in moving over to discs was due to their need to see evidence to prove that they were at least as reliable and efficient as drums. If there was any discernible evidence that drums are as efficient they would still be used in F1 cars, although the weight saving - especially unsprung weight - is worth it in its own right. Anything that allows the tyres to stay in contact with the road has got to be worthwhile as long as the ride - at least in a luxury saloon - is maintained to the same standards of comfort. | ||
| Norman Geeson Unregistered guest Posted From: 82.6.223.129 |
Rolls-Royce was late in placing disc brakes into production almost solely because of the difficulty in eliminating squeal. Their patent to prevent disc brake squeal was granted circa 1966 and consisted of winding approximately one mile of wire around the periphery of the disc. It was estimated that at mid 60's prices the cost was in excess of £100.000. They already knew the potential efficiency and reliably factors from the results of fitting discs to a Canberra Bomber. The first Rolls- Royce product to be fitted with disc brakes was in fact a Bentley R type, experimental chassis no 15B.Dunlop supplied the disc brakes, in fact they were the only company at the time who could do so with any chance of the system entering production. These brakes were fitted by the R-R experimental garage at Crewe. On the subject of drum brakes, there is more to a system than leading/ trailing shoes that make successful drum brakes. If a student examines a Rolls Royce drum brake, he or she will find that in every case, from Ghost to Phantom VI the drums always have a steel face plate, in fact the early cars had complete steel drums. Later the friction areas were cast but the steel face plate was retained. (Message approved by david_gore) | ||
| Bob uk Unregistered guest Posted From: 94.197.122.84 |
Jan You are correct of course because also did they same with tyres. I personally like the rear disc with drum in the middle because of they massive advantage of having a handbrake that easily locks the rear wheels it that extra bit of safety A 245 Volvo will easily lock tear wheels at 20 mph and probably faster So RR got it more or less right except for the Dunlop handbrake. Still what the hey it works. Younger mechanics see the drum as inferior old technology. What often find with older diyers is that they know the above but it is fragmented I try to explain all the gaps in plain language so that car stuff becomes intuitive. Car stuff is a huge subject . (Message approved by david_gore) | ||
| Bob uk Unregistered guest Posted From: 94.197.122.75 |
I have seen wire wound discs in a book somewhere. Nodula cast iron is about the best for road use. Motorbikes preference stainless for bling and ss is not very good for disc. Drums are the same noddy iron. Easy to cast and machine and cheap Mild steel does as well and drums with thin bits are a cross between noddy iron and steel like close grained wrought iron it's almost steel. I could easily make a Shadow disc from mild steel on a 6 Inch swing lathe from msteel and it would work fine but not quite as well as noddy the vents I can't but I can cross drill. But easier to find ready made very close from.another make. And modify. Never by welding. RR has always taken other makers cars apart to have a look. So do the others they go to swap meets. Because once a car is on the road their is no secrets I think the car you describe is the Tibet. Approx 1955 1960. 1958 pressed steel Ltd made Rover P5 bodies and clouds Rover and RR made jet engines. Pressed steel are experts in monocque bodies The P5 could be a Bentley. Fast back. The Tibet had live real axle. And the store keeper from RR is married to mavis at rover I wonder. (Message approved by david_gore) |
