Interesting cam video

drikko

drikko

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Didn't realise the springs/cam followers rotate so quickly, also wondering what the smoke is, just heated up oil or perhaps gases from the cylinder getting past the valve guides?

 
Very interesting, them poor springs get a hard life.
I think the smoke is burning oil on a hot surface, if the valve stem is being wiped of most oil every rotation then the thin residue wouldn't need much excuse to smoke off the way this guy is revving - valve temperatures must be very high.
Of course I have been wrong before!

Could be mist, but the right one has more of it, so could that be the exhaust (i.e. much hotter than the other one).
 
That is amazing Drikko.. can see the rotation of the springs, retainers etc.. and how fast is it all working...??!! No wonder top end failures can be so catastrophic... :o remind me never to poke my finger in there... :LOL:
8)
 
Cam, I have tried the strobe trick a few times to see what is going on with a machine.  
I had a look at the Spin Tron stuff quoted in the video and it looks like they use a high-speed camera @ 4000 frames per second to analyse the spring behaviour. I bet that's not cheap!

While we are on this theme I noticed this little gem:

[youtube]http://www.youtube.com/watch?v=cy_yaAOKjA8&feature=related[/youtube]
 
No I didn't say the cams, I said the springs and followers rotate as they went up and down ensuring they don't wear in one spot.
 
ah - yes..., only read "cam"...  :-[ sorry... still: if you look at the video, at the high revs you almost can't see the cams are moving still. Now think of how fast the crank does, how fast the pistons go up and down - just under your chest when riding...  :o
 
Indeed, imagine the inside of an F1 engine which is limited to 19,000rpm! I believe they have solenoid driven valves though, ie no cams?
 
drikko said:
Indeed, imagine the inside of an F1 engine which is limited to 19,000rpm! I believe they have solenoid driven valves though, ie no cams?
Click to expand...

Apparently not - Renault started to develop the idea but the current implementation is to use pneumatics for closing the valve and a cam to open it 
On the end of the valve is the cam follower that doubles as a small piston. This runs in a cylinder mounted on the cylinder head. Air is trapped in the cylinder and as the cam opens the valve, the air is compressed. When the valve is released, the air in the cylinder acts like a spring expanding to close the valve again. In the real world, a full cylinder of air at atmospheric pressure does not have enough force to close the valve again so the cylinders are pressurised to around 100psi. Obviously no seal is perfect and the teams expect some leakage so the cars carry a reservoir of nitrogen compressed to more 2500psi. This is regulated and fed to each of the valve spring cylinders via a ring main and keeps them all topped up to the required pressure. Nitrogen is used because of its stability, however, with the changing temperatures of an engine, pressures would also vary wildly. To combat this each cylinder also has its own bleed valve to release excess pressures. This has the added advantage of bleeding off any oil that collects in the cylinders.
Click to expand...
 

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  • F1 valve actuation.png
    F1 valve actuation.png
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Yeah it was the Renault thing I was thinking of. So how come the bikes which do the same sort of revs can survive with springs? 
 
I will have a stab.
Nitrogen bottle (at 2500psi that could be lively if it blows up between your legs), inlet gas regulator, outlet gas regulator, non-return valve, gas lines - perhaps there is not enough room on a bike? Or is it too heavy?
 
Laverdalothar said:
ah - yes..., only read "cam"...  :-[ sorry... still: if you look at the video, at the high revs you almost can't see the cams are moving still. Now think of how fast the crank does, how fast the pistons go up and down - just under your chest when riding...   :o
Click to expand...

and that the pistons have to stop at the end of each stroke, then accellerate and decellerate?

Didn't Honda have a 50cc twin that revved to 22k in the 60s?


SimonR501 said:
I will have a stab.
Nitrogen bottle (at 2500psi that could be lively if it blows up between your legs), inlet gas regulator, outlet gas regulator, non-return valve, gas lines - perhaps there is not enough room on a bike? Or is it too heavy?
Click to expand...

Isn't that why Ducati have the Desmo to close the valves, so that you don't lose your testicles with an exploding Nitrogen bottle?

Mick....
 
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