F1 V10 Intake Camshaft Spec, a closer look

[Zynerji]

Great stuff, thanks for the well put together responses to my questions.

The logical side of my brain said that the camshaft would lag a bit behind the quill shaft due to the fact that it's a torsion spring. That didn't make sense to me as the clearances are so tight, that too sudden of an acceleration would have the piston hitting a valve.

The quill shaft would be much too stiff for that to happen. Think of its function in terms of soaking up large spikes in timing drive torque. These spikes are much higher than the average drive torque but very short duration. They will be positive and negative.

If you are electrically minded, imagine a low pass filter removing the AC component without affecting the DC.

I get it now... I was thinking more like the torsion springs on the suspension than a direct drive harmonic damper.

And I am far more of a "people math" person, so I'm much more familiar with leadership, psychology, NLP, and such, but I find very few congruencies with mechanical or electrical systems.

[J.A.W.]

Great stuff, thanks for the well put together responses to my questions.

The logical side of my brain said that the camshaft would lag a bit behind the quill shaft due to the fact that it's a torsion spring. That didn't make sense to me as the clearances are so tight, that too sudden of an acceleration would have the piston hitting a valve.

The quill shaft would be much too stiff for that to happen. Think of its function in terms of soaking up large spikes in timing drive torque. These spikes are much higher than the average drive torque but very short duration. They will be positive and negative.

If you are electrically minded, imagine a low pass filter removing the AC component without affecting the DC.

I get it now... I was thinking more like the torsion springs on the suspension than a direct drive harmonic damper.

And I am far more of a "people math" person, so I'm much more familiar with leadership, psychology, NLP, and such, but I find very few congruencies with mechanical or electrical systems.

Yeah Z, I figured maybe that was the case..
& so I cited Nikola Tesla ( inventor of practical electricity usage via AC current, amongst myriad things) accordingly..

[Brian.G]

https://i.imgur.com/XhG0Gb0.jpg
Needs some smoothing but you get the idea.
16mm lift is outrageous! Duration at 1mm lift is 268 crankshaft degrees.

Thanks for putting the graphs above together, I've been traveling since and just getting back to this now.



Brian,

[PlatinumZealot]

The quill shaft simply twists a little bit when there is torque spike. F1 doesnt use belts or chains but timing gears. Very hard timing gears.
The twist of the quill shaft absorbs energy. But it is not a large displacement. Timing gears and chains are not perfect either those too will have slight offsets in displacement and this is not a bad thing. Aerodynamics of the cylinder have on an even larger range of uncertainty.

[J.A.W.]

Gear-drives have always been preferred for cam-timing accuracy, on a cost-no-object basis.. since well.. ever, really..

[godlameroso]

Gear-drives have always been preferred for cam-timing accuracy, on a cost-no-object basis.. since well.. ever, really..

Anyone that's worked on old Mercs knows all about chain stretch and using offset woodruff keys as a band-aid fix.

[J.A.W.]

Yeah, it was the higher-spec, & heavy-duty (diesel) M-B's which came endowed with a durable duplex roller-chain set-up..

M-B likely figured that its 'select client-group' would find the threshing din of a gear-train.. aurally objectionable,
but the very idea of rubber band drives.. was also deemed.. unacceptable.. as unspeakably plebian..

( Incidentally G, those same 'hi-test' IWIS duplex timing-chains are now a 'go to' - as primary-drive chains..
- for several 70's classic motorcycles, such as Norton Commando & Laverda)..

[Jonny Quest]

Typically the intake valve opens BTDC. I think your open and closing points are incorrect.

Brian are you in USA? I'd measure the cam for you on camshaft measuring test stand.

[gruntguru]

The graphs do not mention TDC. The numbers start with zero degrees aligned with start of opening ramp. Without the complete engine or a specification, there is no way of knowing where TDC lies.

[Jonny Quest]

Ahh, I read what he wrote wrong.

Camshafts are typically measured at .1 degree intervals. There's a lot going on at the opening and closing ramps of cams that you can't see at 1 degree steps.

The intensity of the lobe is just as important as the lift and duration. The use of finger followers is one of the main reasons for this. You're limited to the flanks velocity based on bucket diameters.

[humble sabot]

As someone fairly new to camshaft profiles, my intuition tells me that they rotate too fast and that getting the valve to track the lobe perfectly isn't really achievable. But your comment about 'a lot going on' suggests that I'm effectively wrong about both?

[gruntguru]

The valve needs to "track the lobe" apart from variations due to elasticity of the components. If valve motion departs from lobe motion you have "valve float" or "valve bounce" and catastrophic failure soon follows.

[63l8qrrfy6]

Hi Mudflap. I was wondering which would be the dominant forcing input for camshaft drive resonances - crankshaft velocity oscillation or oscillating torque inputs to the camshaft from the valve gear? Intuition tells me its the latter.

A bit of a late reply - I wasn't sure either as I believe both scenarios are plausible.
For example an engine with a mild cam profile operating with some form of crank torsional resonance will probably cause a higher cam excitation than that produced by the interaction between lobe and valve/springs.

Initially I looked at some cam strain gauge data but it was difficult to work out what was producing the torques since the maximum amplitudes from both cam and crank are at firing frequency (in hindsight maybe I should have looked at phase angle offset too).

Then I checked some dynamic models for a couple engines at work (had to replace the cam lobe excitation with a mean torque to isolate the crank excitation, then replace the cam drive excitation with a mean torque to isolate the lobe excitation) and in both cases the cam oscillations were dominated by the lobe torques as you suggested.
Both engines I've looked at have gear driven cams with no compliant elements.
As a side note, the torques caused by gear impacts due to backlash seem to dominate everything else.

[humble sabot]

That all seems to make intuitive sense.

[gruntguru]

As a side note, the torques caused by gear impacts due to backlash seem to dominate everything else.

I'm sure they do - at least from a torque peak amplitude perspective. From an "energy per pulse" perspective its probably the cam lobe excitation.