I reckon not although not come across an engine that does not have them like that.
saw this: and those circles are presumably for gears to take the drive to the cams?
can't get my head round this without drawing and thinking it but but does the camshaft(s) need to rotate in same direction as crank?
I reckon not although not come across an engine that does not have them like that.
saw this: and those circles are presumably for gears to take the drive to the cams?
Quite a few engines (such as the earlier ford cologne V6s) drove the cam through gears instead of belt or chain, so they would rotate opposite to the crank.
They usually rotate in the same direction but there's no reason why they couldn't be "cut" in reverse.
It's also normal for them to rotate at half the speed of the crank.
You could have them going the opposite direction if you cut them reverse and you could have them rotating at crank speed but the profile would be
harsh and there would be large empty spaces on the cam (not ideal)...
quote:
Originally posted by BenB
You could have them going the opposite direction if you cut them reverse and you could have them rotating at crank speed but the profile would be harsh and there would be large empty spaces on the cam (not ideal)...
quote:
Originally posted by BenB
you could have them rotating at crank speed but the profile would be harsh and there would be large empty spaces on the cam (not ideal)...
The cams in my engine are - one on each head is belt driven from the crank as normal , then the other on each head is geared from the belt driven one
.
The strange thing's are , the cambelt drives the inlet cam on one head and the exhaust cam on the other , and the gears mean the inlet and
exhaust cams rotate in opposite directions...
All of which made it a bit of a challenge to work out the fireing order for the EDIS and coilpack
quote:
Originally posted by MikeRJ
quote:
Originally posted by BenB
you could have them rotating at crank speed but the profile would be harsh and there would be large empty spaces on the cam (not ideal)...
Nope, this wouldn't work. If the cam was running at the same speed as the crank, it would have to open and close both valves in one crank revolution.
quote:
Originally posted by 02GF74
yep I agree. for 4 stroke, in one revoution the exhaust is moved without moving the inlet then somehow cam on the next crank revolution opens the exahaust without touching the inlet. I cannot see how it can be done with a solid cam.
But both would move in that one revolution, so it wouldn't work. They could move at different times, but they would still have to move. They need to open the valve once for every two rotations of the crank, so it's not possible with 1:1 speed ratios.
As above - cant have a cam spinning at crank speed on a 4 stroke! Valve cycle has to last 2 revolutions of the crank so to be implemented with a
camshaft it must spin at half crank speed. If a camshaft span at engine speed, whatever it does during one crank revolution would just be repeated in
the next.
Liam
The crank can run either way round, it really doesn't make any difference, the pistons still just go up and down. The cam(s) has to run in the
direction it's been designed for though, the open and close ramps are profiled differently. That and on a single cam the lobes will be in wrong
place.
EDIT: that's assuming it's a 4 cyl with 1342 firing order. Odd fire v6 won't work backwards, the firing order will go all wrong. Need
to have a think about v8's, I reckon some will be alright...
[Edited on 11/6/08 by martyn_16v]
[Edited on 11/6/08 by martyn_16v]
Actually, it's true- I'm talking ballcocks.
If you had the cam spinning at crankshaft speed you'ld need half a cycle per rotation which clearly isn't possible....
It's a good thing I'm not an engineer