SBCs have had that for years, no timing chain jumping.
1
2
-
July 29, 2010 6:09 a.m. 914Driver SuperDork
-
July 29, 2010 6:16 a.m. mad_machine SuperDork
Knurled wrote:
mad_machine wrote:
maybe too efficent for what it cost to produce. It is cheaper to cast rocker arms and cut down pushrods to the correct length.. and they work 90% as good
Um.
There is never any such thing as "too efficient"!
Ford had two geardriven OHCs that I can think of. The DOHC tank engine I mentioned earlier, and the Foyt Indy engine, which was a race-only engine.
I had to edit this because I got my engines mixed up. http://www.bacomatic.org/~dw/engine/fordv8/foyt/foyt.htm Foyt engine.
I meant more in a cost to benefit ratio. It is easier and cheaper to produce a chain and sprockets than to set up a head full of precisely machined gears. Especially when that chain can do 95+% percent of what the gears can do.
That same mentality works well on pushrod engines. It is easier and cheaper to cast some rockers and put balls on the ends of hollow tubes that can do 85 to 90% of the work for a LOT less money and work.
Gears only really work on a pure race or military application that requires precise timing to get the most out of the engine
-
July 29, 2010 6:24 a.m. 4cylndrfury SuperDork
Im REALLY interested in learning more about the jackshaft idea....
-
July 29, 2010 8:14 a.m. Teh E36 M3 Reader
How many gears does it take? each of those has some lash... I thought the belt was the best compromise for long runs like that.
Neat looking (and probably sounding), but.... no.
-
July 29, 2010 8:50 a.m. mad_machine SuperDork
lash is a problem.. in all manner of valve train. Wether chains, belts, or gears.
-
July 29, 2010 1:32 p.m. GameboyRMH SuperDork
F1 engines have gear-driven cams IIRC...but that probably has more to do with the nearly 20krpm redline.
-
July 29, 2010 3:02 p.m. erohslc Reader
Roller chains and cogged belts have nearly zero parasitic loss, no matter how much power is transmitted. Vs 2-5% proportional loss for each gearset mesh. (remember that meshing gearsets are sliding)
-
July 29, 2010 8:12 p.m. mad_machine SuperDork
I would doubt that... I have done enough rubber timing belts to know that the belt slides a bit too,
ALL of the systems have some parasitic loss...
and yes, gameboy probably has it right. at 20Krpms.. the gears are probably a LOT more stable
-
July 29, 2010 8:47 p.m. shadetree30 Reader
Knurled wrote:
Ford had two geardriven OHCs that I can think of. The DOHC tank engine I mentioned earlier, and the Foyt Indy engine, which was a race-only engine.
IIRC they also had a 427 SOHC. Race-only also IIRC.
The Ford DOHC Indy engine was called a Ford before AJ bought all the inventory and production....
