Honda Power Unit

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
ncassi22
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Re: Honda Power Unit

Post by ncassi22 » Sat Jan 13, 2018 2:12 am

PlatinumZealot wrote:
Sat Jan 13, 2018 2:04 am
I dont see how friction to turn the cam would change much versus pneumatic if the springs are designed properly. Pneumatic is also addtional complexity and space taken up.
I didn't take into account that the air would need to apply the same pressure as a physical spring would to keep the valve closed or pressed against the rocker. Pretty dumb on my part :lol:

PlatinumZealot
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Re: Honda Power Unit

Post by PlatinumZealot » Sat Jan 13, 2018 2:19 am

No. not dumb actually!
above higher rpms there is a point where the spring has to be made stiffer to prevent hysteresis, resonance and all sorts of effects and not necessarily because increased spring presssure is needed for the valve. In those cases air will be an advantage you since can use less pressure there. But i think the rpms of the current regs being sub 13,000 rpms, is in the realm of springs and with F1 know how applied you can bet that those springs will be specially designed to be light and soft as possible.

Tommy Cookers
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Re: Honda Power Unit

Post by Tommy Cookers » Sat Jan 13, 2018 11:46 am

'prevent hysteresis' - nonsense !

hysteresis is an inherent characteristic of the material and not something that can be changed by design
metals have little hysteresis and higher strength versions of metals ie spring materials have less than little hysteresis
so the best qualified spring materials via high strength are also the best via low hysteresis

hysteresis can down in the region of ten parts per million and should be close to that in a race valve spring
ok such a valve spring will be generating hundreds of times per second that hysteresis (loss of strain energy) as self-heat
which will certainly need removing by properly designed coolant flow

force measurement in eg wind tunnel tests of race cars or when buying a piece of steak depends on the low hysteresis of metal
the load cells or balances work by measuring the dimensional change in metal with change in load
hysteresis would show as a residual error ie the output not returning to zero when the load is removed

true hysteresis is the residue after unloading and allowing the self-heat to disperse
most load cells are fortunately small enough for natural heat dispersion within the time taken by the calibration procedure
but with large load cells the calibration procedure should allow for this (but probably hasn't)
anyway various behaviours of the strain-sensing side tend to add to overall attribution as measurement 'hysteresis'


regarding eg triple valve springs (or similar doubles) ..... afaik
interference friction develops at incipient surge resonance of main spring(s) and by design this won't be at continuous rpm
in an engine committed to lasting several events untouched
Last edited by Tommy Cookers on Sat Jan 13, 2018 1:12 pm, edited 3 times in total.

Mudflap
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Re: Honda Power Unit

Post by Mudflap » Sat Jan 13, 2018 11:51 am

bill shoe wrote:
Fri Jan 12, 2018 10:28 pm
Google "triple valve springs", then go to images. It's the standard high performance valvespring config. I think the middle spring is often there to provide control and light damping to the inner and outer springs that do most of the heavy lifting.
http://www.jegs.com/images/photos/200/278/278-1248.jpg
I have not denied their existence - my point is that as soon as you need more than 1 spring and friction damping you are already better off using a pneumatic system.

That being said, I still believe that it can be done with a well engineered single spring.
How much TQ does it make though?

hurril
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Re: Honda Power Unit

Post by hurril » Sat Jan 13, 2018 1:01 pm

amho wrote:
Fri Jan 12, 2018 8:23 pm
hurril wrote:
Fri Jan 12, 2018 8:15 am
ncassi22 wrote:
Fri Jan 12, 2018 7:22 am
Also it says something about injectors on the exhaust side??? Translation errors or something else?

Injectors on the exhaust side is nothing strange. The injector merely sits on the cylinderbank together with the exhaust valves instead of with the intake valves.
I always thought that the injector is placed in the top of prechamber, but If injector is in exhaust side (as motor fan pic. indicates) how do they have rich mixture in the prechamber? there might be multiple injection first one when piston is near tdc to mainly fill prechamber?
https://drive.google.com/open?id=1tpCUl ... SY3ZJV5gNa
I know, right? I've wondered that from the start and the only thing that seems possible is for the injector to create a denser cloud close to the holes in the pre-chamber and then hope that enough of it gets sucked/ pushed in there by the compression. (The pressure gradient is evened out/ lowered so that it is equal on both sides of the "membrane" that the holes form, thereby pulling the fuel with it.)

There seem to be so many concurrently active factors that go in to this though and it's not that easy to form a working picture of all of them I think.

PlatinumZealot
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Re: Honda Power Unit

Post by PlatinumZealot » Sat Jan 13, 2018 1:16 pm

Tommy Cookers wrote:
Sat Jan 13, 2018 11:46 am
'prevent hysteresis' - what nonsense ?!

hysteresis is an inherent characteristic of the material and not something that can be changed by design
metals have little hysteresis and higher strength versions of metals ie spring materials have less than little hysteresis
so the best qualified spring materials via high strength are also the best via low hysteresis

hysteresis can down in the region of ten parts per million and should be close to that in a performance valve spring
ok a race valve spring will be generating thousands of times per second that hysteresis (loss of strain energy) as self-heat
which will certainly need removing by properly designed coolant flow

force measurement in eg wind tunnel tests of race cars or when buying a piece of steak depends on the low hysteresis of metal
the load cells or balances work by measuring the dimensional change in metal with change in load
hysteresis would show as a residual error ie the output not returning to zero when the load is removed

true hysteresis is the residue after unloading and allowing the self-heat to disperse
most load cells are fortunately small enough for natural heat dispersion within the time taken by the calibration procedure
but with large load cells the calibration procedure should allow for this (but probably hasn't)
various behaviours of the strain-sensing side tend to add to an overall measurement 'hysteresis'


regarding eg triple valve springs (or similar doubles) ..... afaik
interference friction develops at incipient surge resonance of main spring(s) and by design this won't be at continuous rpm
For my simple view Hysteresis is when the rebound properties of the spring are different from the bound properites.. Making the spring slighlty unseat at high cycle speed..

I am not a "googly" type of poster.. But i did a sanity check on google amd this is what i got. I don't think i am too far off the mark.
Compression Spring Hysteresis:
The mechanical energy loss that occurs as a result of the spring ends' tendency to rotate when compressed during cyclic loading and unloading.

Mudflap
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Re: Honda Power Unit

Post by Mudflap » Sat Jan 13, 2018 3:59 pm

You are both right I think.

TC is talking about stress-strain curve hysteresis which is material specific and is negligible provided that loading is kept below the proportionality limit (and it is for a spring).

PZ is talking about energy dissipation through friction which can come from several sources such as spring/spring, spring/retainer, or contact between the coils of a single spring. This is normally manageable for a single spring and becomes atrocious for interfered springs.
How much TQ does it make though?

Tommy Cookers
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Re: Honda Power Unit

Post by Tommy Cookers » Sat Jan 13, 2018 4:48 pm

iirc about a million Honda CB450 and CB500Ts etc had torsion bar valve springs
so external friction hysteresis was minimal and internal hysteresis was minimal and strength high due to pure torsional loading
these engines were somewhat related to the 1964-5 F1 engine

Mudflap
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Re: Honda Power Unit

Post by Mudflap » Sat Jan 13, 2018 5:15 pm

I reckon there is still a fair amount of friction in the splines.
In terms of loading the torsion bar setup trades hertz coil contact for hertz spline contact - which may well be a bit of an improvement.

The real advantage is that dynamics are easier to deal with as there is only the torsion mode of the bar to worry about. By comparison one needs to assume about 4 degrees of freedom per coil when modelling springs resulting in 4x number of active coils of modes that have a significant participation.

As a disadvantage I would guess that the inertia is quite a bit higher compared to that of a conventional spring.
How much TQ does it make though?

roon
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Re: Honda Power Unit

Post by roon » Sat Jan 13, 2018 9:56 pm

Tommy Cookers wrote:
Sat Jan 13, 2018 4:48 pm
iirc about a million Honda CB450 and CB500Ts etc had torsion bar valve springs
so external friction hysteresis was minimal and internal hysteresis was minimal and strength high due to pure torsional loading
these engines were somewhat related to the 1964-5 F1 engine
Interesting. Thanks, Tommy.

Image

Image

PlatinumZealot
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Re: Honda Power Unit

Post by PlatinumZealot » Sun Jan 14, 2018 1:52 am

Nice information there. I didn't know such a mechanism exists. The torsion bar is in two peices. One half enveloping the other. Smart. Would be interesting to see how it works for paired valves.

wonk123
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Re: Honda Power Unit

Post by wonk123 » Sun Jan 14, 2018 9:45 am

godlameroso wrote:
Fri Jan 12, 2018 11:50 pm
I mean Honda made single coil springs that could handle 9,100 rpm and 400,000km of service back in 1999. I would not be surprised if they had valve springs capable of handling 13k for 7,000km 19 years later.
One of the biggest reasons for the massive power increases in the last 20 years in NASCAR and drag racing is the development in valve spring technology.
As an example pro stock engines can have valve lift of 1.2 inches and max rpm of 12,000. They don't exactly last for 7,000km though

Mudflap
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Re: Honda Power Unit

Post by Mudflap » Sun Jan 14, 2018 10:52 am

PlatinumZealot wrote:
Sun Jan 14, 2018 1:52 am
Nice information there. I didn't know such a mechanism exists. The torsion bar is in two peices. One half enveloping the other. Smart. Would be interesting to see how it works for paired valves.
You'd just need to have one more arm coming out, rigidly connected to the first.

Or keep a single lobe with a single arm and have a valve bridge to connect the 2 valves.

Of course you'd then need to double the torsional stiffness which is quite neat as all you have to do is reduce the length of the shaft.
How much TQ does it make though?

gruntguru
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Re: Honda Power Unit

Post by gruntguru » Sun Jan 14, 2018 11:03 am

That would then run into a strain energy issue. Assuming an optimised design, you need twice as much metal in the spring if you want it to control twice the reciprocating mass.

The nicest thing about the torsion spring is undoubtedly its lack of resonances. Recip' mass shouldn't be a problem if the finger also serves as a cam follower. Packaging would be the main downside.
je suis charlie

Mudflap
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Re: Honda Power Unit

Post by Mudflap » Sun Jan 14, 2018 11:21 am

Not quite sure what you mean by the strain energy issue.
You'd just design it like a normal quill shaft - calculate the diameter to take the required torque then determine the length to achieve the required stiffness.

The fact that you have the outer shaft also contributing stiffness gives you even more opportunities to optimize it.
How much TQ does it make though?