F1 V10 Intake Camshaft Spec, a closer look

[63l8qrrfy6]

No need for quills in production engines.
Camshafts have higher torsional frequencies in 'normal' engines while excitation frequencies coming from the crank are much lower, in line with the engine speed.

Also chain and belt drives used by most automotive engines are very effective decouplers.

[J.A.W.]

Would anyone mind explaining the quill shaft, what it does, and why it's useful in this application? It would just seem to add a variance to the position of the valve in my mind, leading to possible in-cylinder collisions with the piston.

Im super interested in understanding this concept, so any explanation from the group would be most welcome!

Nikola Tesla noted the gist.. well over a century ago:

"If you want to find the secrets of the universe, think in terms of energy, frequency & vibration."

[strad]

Tommy is what you're saying that it , the quill shaft, saves them from what they used to have to do, produce the cam with a built in twist so that when those forces twisted the shaft it would then be straight?
Long time ago I admit.

[bill shoe]

Would anyone mind explaining the quill shaft, what it does, and why it's useful in this application? It would just seem to add a variance to the position of the valve in my mind, leading to possible in-cylinder collisions with the piston.

Im super interested in understanding this concept, so any explanation from the group would be most welcome!

Here's an additional explaination of the camshaft quill shaft- It's a (rotational) vibration absorber, so it smooths out the non-smooth rotational accel and decel into something closer to steady-state. This stops camshaft vibration from going into the camshaft gear-drive, and/or it stops gear-drive vibration from going into the camshaft.

From a design point of view, it's a neat way to simplify the problem. Don't kill yourself trying to design key components around meeting certain vibration targets, just put the quill vibration absorber in there and figure out a reasonable compliance for it when everything else is done.

[roon]

Also, notice that the quill engages with the hollow camshaft between the first and second cylinder, reducing the longest span of the camshaft. So not only will it absorb torsional loads/shocks, but it will also allow for a more evenly loaded camshaft. Effectively a four cylinder and a single cylinder span from the drive input. Good work, Brian.

[gruntguru]

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.

Interestingly, if you CMM a poorly ground cam and use the measured lift profile to differentiate acceleration you end up with very similar high frequency "errors" which in reality do excite spring frequencies and fatigue them much quicker than a perfect acceleration curve would suggest.

The errors are normal for lift data that has been obtained manually like this. Differentiating twice across 1 degree intervals that have been measured with a precision of perhaps 0.2 degrees (20% uncertainty) is always going to look like that (worse actually - I did do some smoothing).

[FastFreddy]

Thanks once again for the though provoking images and information!

I can’t help but notice there is what appears to be a Ditch or Dam on the backside of the intake valves. My first though is that would not be great for flow/performance, or is this a mechanism to increase fuel atomization, trading flow for better combustion efficiency? It seems that at the rpms generally associated with this engine and given multiple injectors per cylinder, fuel atomization would be pretty good. Is there actually a problem with raw fuel wetting of the ports that this type of turbulence generating mechanism might help? Or, do these engines run in batch fire mode (two squirts per cycle) that dumps raw fuel in the intake track at low air flow times which then congregates around the back of the valve at the seat/throat area?

Next it kind of looks like the valve seats on the head near the back edge of the valve face, the valve face looks to be a single angle and very wide? None of which at least as far as I am aware is a good thing for flow, performance or durability. Why would you want to have all of that valve face sticking up above the valve seat and in the chamber? Seems that extra valve diameter in the chamber would also cause more shrouding issues near the cylinder walls? That darker band around the valve face at the back is exactly what a valve seat looks like after a slight lapping to the head, at least in my book.

Our normal mild street performance valve face has a minimum of three angles on the face of the valve, a valve seat angle with top and bottom cuts differing from the seat angle by no more than 7 degrees. My understanding is that any abrupt change in angle of a surface greater than 7 degrees can generate turbulent non-laminar flow, something we have always assumed was not a good thing in and around the valve seats particularly from about ¼” to ½” (6mm to 13mm) above or below the valve seat. Our racy stuff gets more bottom cuts to blend the seat angle to the stem to head radius of the back of the valve. Following this general prescription has in general most times netted improvements in flow numbers as well as demonstrable performance increases.

Or, is this just a box stock valve blank put in the head for demo and or imaging purposes, and I shouldn’t read anything into the images?

[e36jon]

Have you checked out Brians earlier cylinder head post? He has some amazing photos of the ports and seats: viewtopic.php?f=4&t=15385 No steps. Smooooth.

Edit: I see that you were on the prior thread (linked). The first post there has all of the images, and down towards the bottom he has sectioned views of the ports and seats.

[godlameroso]

Would anyone mind explaining the quill shaft, what it does, and why it's useful in this application? It would just seem to add a variance to the position of the valve in my mind, leading to possible in-cylinder collisions with the piston.

Im super interested in understanding this concept, so any explanation from the group would be most welcome!

The cam is splined to the quill, the quill has some flex in it and takes up any resonance from the cam drive gear. In other words it acts like a lost motion assembly.

[63l8qrrfy6]

Just because quills seem to confuse people:


Compliant drives are used to lower the natural frequency such that the ratio of forced frequency to natural frequency (x axis) increases - generally values of just over sqrt(2) are targeted as this is the cross over point where the transmissibility starts to increase with damping.

The objective is to minimize the transmissibility (the ratio of input amplitude to output amplitude - in this case the input being the crank vibration amplitude while the output is the cam vibration amplitude).

If fd/fn is close to 1 the camshaft will have a resonance where the quill is the node and the transmissibility decreases with increasing damping, while if fd/fn > sqrt(2) the transmissibility increases with increasing damping.

IIRC the v10 (TJ/VJ) did not have a damped quill shaft but the v8 (CA) did - this goes to show you can successfully design on both sides of the sqrt(2) point.

[godlameroso]

Just because quills seem to confuse people:
https://www.researchgate.net/profile/Ps ... atio-2.png

Compliant drives are used to lower the natural frequency such that the ratio of forced frequency to natural frequency (x axis) increases - generally values of just over sqrt(2) are targeted as this is the cross over point where the transmissibility starts to increase with damping.

The objective is to minimize the transmissibility (the ratio of input amplitude to output amplitude - in this case the input being the crank vibration amplitude while the output is the cam vibration amplitude).

If fd/fn is close to 1 the camshaft will have a resonance where the quill is the node and the transmissibility decreases with increasing damping, while if fd/fn > sqrt(2) the transmissibility increases with increasing damping.

IIRC the v10 (TJ/VJ) did not have a damped quill shaft but the v8 (CA) did - this goes to show you can successfully design on both sides of the sqrt(2) point.

Do you think this was because the V8 had more inherent resonant frequencies than the V10's? If I recall correctly the V10's didn't have a fixed 90 degree bank angle, and so allowed more favorable bank angles to reduce vibrations.

[63l8qrrfy6]

Correct, v10 bank angles were not regulated. For the same engine speed , an even firing v10 will have a 25% higher firing frequency compared to an even firing v8. On top of that, the longer crank and camshafts of a V10 would have had lower torsional natural frequencies so that the fd/fn ratio would have been significantly higher.

The Cosworth design philosophy has always been to choose the best firing order for gas exchange and live with somewhat harsher torsional vibrations. The risk is that whatever extra power can be gained from that might be lost in the myriad of dampers required to tame the vibration.

[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.

Thanks for the graph, that helped most!

[gruntguru]

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.

[gruntguru]

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.