Why are timing belts always used nowadays! As I remember, some great engine designs had timing gears like Ford Capri's or the old VW beetle. No need for labor intensive cambelt replacements. Are they so inefficient that they aren't used anymore!
morrisman1,
Jun 9, 10:22am
maybe with DOHC designs the cams are just too far away from the crank to make it an economical option. When the cam was only 6" away from the crank then it was probably quite a good option
greeny,
Jun 9, 10:23am
bit hard to fit with an over head camChains and gears were used when the cam was in the blockof course some maker still use chains and there seems to be a move back to them
NZTools,
Jun 9, 10:23am
What model capri had a great engine design!
ralphdog1,
Jun 9, 10:28am
Not an efficiency issue, it is about the relative locations of the crank and cam(s) as morisman1 says, belt is also less noisy and cheaper.
xs1100,
Jun 9, 10:37am
the 2.0 ohc
tonyrockyhorror,
Jun 9, 10:39am
They don't use gears because they're noisy, expensive (excessively so when you're trying to get accurate backlash across a series of gears because of the accuracy required), and less efficient.
nightboss,
Jun 9, 10:40am
Duck!
NZTools,
Jun 9, 11:03am
Which had a belt, not gears.
carclan,
Jun 9, 11:07am
Polyagonal vibration
franc123,
Jun 9, 11:11am
Timing belts are actually getting more rare by the day, most manufacturers are reverting to chains, due to basically everything being DOHC these days its simply not practical to use gears. The gears used on those old British Ford Essex V6 engines were actually terrible because of crappy fibre that sheared or even melted teeth if it got hot enough, they only worked if they were made of steel or the better quality nylon used in the german cologne motors.If you think changing belts is labour intensive wait until the chain on your modern engine needs changing, and they often need it sooner than you think due to poor engineering and cheapskate single link designs that stretch and cause various engine sensors to have a spazz and put warning lights on and do silly things. You are better off with the belts but the nitwit belt phobic public don't realise this.yet.
wizid,
Jun 9, 11:29am
o u gotta b kidding
pge,
Jun 9, 12:01pm
Just my thoughts
1) Gears are hell of a lot noisier - especially straight-cut 2) Manufacturing costs are lower for chains or belts 3)Gear backlash is critical, and heaps harder to set up perfectly -- then you run into wear-problems 4)When helical-cut gears used, thrust washers add complications
clanky,
Jun 9, 7:55pm
Just my 2 cents worth.the marine diesel engines I work with (only 2 major slow speed and a few medium/high speed) are either chain or gear driven, no belts. Latest engines don't even have a camshaft, so the question becomes moot. These are decent sized engines with up to 10,000 BHP per cylinder, so no cam is a saving on weight and allows for far superior timing of the exhaust valve due to torque twisting of the crankshaft (torque measured in tonne-metres).
bill-robinson,
Jun 9, 8:04pm
All down to cost. Belts are cheaper than any other form of cam drive. the company accountants would like 2 strokes. less parts and fittiing costs same retail price = more profit.
the-lada-dude,
Jun 9, 8:29pm
i thought most big marine diesels were 2 stroke with turbo blowers . theres no reason you can't run an ex valve being slow speed. are the ex val opperated by electric solinoids !
carclan,
Jun 9, 9:00pm
Correct, hydraulic actuation via electroinc operated solenoid valves. I was at the B&W factory a few years back when one of these engines was on the test bed
Lada and carclan - correct, I was in Copenhagen last month. They ar still developing their camless engine further, but Sulzer/Wartsila have the RT Flex in service. Not only 2-cycle T/C, but solenoid operated fuel injection and exhaust valve hydraulic operation. Probably the most advanced engines in the world, to be honest. Makes most car and truck engines look like something that should be fitted to Fred Flintstone's car! Love to see the sideways hat brigade doing burnouts where the engine has 2 or 3 7-tonne turbos fitted!
msigg,
Jun 11, 3:08am
My Nissan safari(diesel) has gears.
sifty,
Jun 11, 3:13am
The old HQ's had a habit of shearing their crappy fibre gears.
A common replacement was fitting alloy ones, which made a nice whirring noise, like a mini supercharger whine.
elect70,
Jun 11, 3:24am
HA yeah& every garage had 1 in stock &cortina/sierratiming belts, bro had his HQ done atgarage atTurangi,shat itself along desert rdwith all the family on board2 days after Xmas .The garage guy opened up & did it for them.Try & get that sort of service today , theyd tell you to F off
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