Spitfire 1500 valve springs

[johny]

55 minutes ago, Steve P said:

I thought it was to up the rev limit before valve bounce occurs, not that any 1500 would reach that without grenading the bottom end.

S

would have thought just a beefier single spring would do that....

[Pete Lewis]

double springs are there  to tune the hysteresis

 

[PeteH]

21 minutes ago, Pete Lewis said:

double springs are there  to tune the hysteresis

 

That would make sense?. The differing sizes and diameter`s would have different natural frequencies. whch is what comes through in the vid;.

Pete

[johny]

so theres no downside to double springs apart from cost😍 

[Clive]

10 hours ago, johny said:

so theres no downside to double springs apart from cost😍 

It depends. Camshafts suffer if he spring rate is too high. So care is needed to make sure the combined rate is mild enough.

I have a T shirt, possibly the uprated springs, possibly the cam quality. Supplied as a kit by Kent cams. Wouldn't touch them with a bargepole ever again. 

And yes, teh jag springs are quite mild, and I believe have a similar rate to the old Ford X-flow springs. Trouble is getting any spring that is a good mtach in terms of rate/length be it valve or suspension....

[Wagger]

Just watched Pete's video. Very good explanation of a natural phenomena. Resonance occurs all over the place. Sometimes it is desirable, at other times a nuisance. AM and FM radio depends upon it in order to work, So do pendulums and balance wheels. I worked as an Electrical and Electronic Engineer in an acoustic lab in my twenties. Speakers and micropnones also have many resonances, as do piano and guitar strings. It is almost impossible to make a perfect speaker cabinet. Listening to an orchestra also depends upon the size of the theatre and where you sit. Quite complex physics.

And then we have the Tides and the solar system, It goes on and on. Just like me.

[Pete Lewis]

we have drivers that never get to 3k never mind valve bounce revs .

my old 53 side valve minx we added washers under the springs and she would pull up to 7k  good for an old long stroke 

along with some bits from a wrecked sunbeam racer special .

then a crown popped off !!!!  replacement engine would stuggle to get 4k and wrecked what was great fun (in its day ) to a flat boring engine 

and the va varoom   was lost 

its all in the springs  

Pete

[JohnD]

I once acquired an engine that had been rebuilt, roller rockers 'n' all!  The oil was still golden, we ran it for a track day.    Noisy tappets so adjusted, but after a send run the tappets opened up again, and again.     Later inspection revealed that the camshaft journals had worn away the block, because the DPO had fitted extra-strong valve springs!   The block was scrap!

Twin springs is better, because the base frequency (or constant) of springs in parallel is their sum. (In series, you sum the reciprocal of their reciprocals!).    Thus, their base frequency, at which resonance will occur is twice (about) what a single spring would have.