Hawker had to meet the `30s RAF requirement that fighter aircraft be 'light enough on their feet'
Yeah, the author is a member here, but seems a tad reticent to jump in on this thread...Billzilla wrote: ↑Sat Jan 22, 2022 9:23 amFWIW this is supposed to be a very comprehensive & thorough book on the subject. A little out of my price range right now unfortunately. And even more expensive at ABEBooks.
https://www.booktopia.com.au/the-secret ... 58504.html
He is the guy in the podcast, I think.J.A.W. wrote: ↑Sat Jan 22, 2022 2:26 pmYeah, the author is a member here, but seems a tad reticent to jump in on this thread...Billzilla wrote: ↑Sat Jan 22, 2022 9:23 amFWIW this is supposed to be a very comprehensive & thorough book on the subject. A little out of my price range right now unfortunately. And even more expensive at ABEBooks.
https://www.booktopia.com.au/the-secret ... 58504.html
Perhaps due to a few issues in his book, that ah, drew some flak here, on technical grounds.
(To be fair, I have posted some of his literature review research cache, as Calum kindly put it up
on his site - being notably useful - & esp' since the 'Flight' archive is no longer available, on-line).
supercharger efficiency was improved greatly both with and without added complexity ....
It misses the essence however, since a less efficient engine can be 'forced' to make more powerTommy Cookers wrote: ↑Mon Jan 24, 2022 6:40 pmsupercharger efficiency was improved greatly both with and without added complexity ....
raising engine efficiency in every aspect .....
NACA's head of propulsion Dr Pinkel said that the supercharger was the important thing not the engine
the book discussed iirc covers the advanced throttle/vane thing of Junkers etc via the USSR engines
afaik the same thing was invented by a Polish person in or given to France c.1939 and there seen by the RAE etc
and eventually earmarked for the BRM V16 ? (but never used)
I clicked on this because it had Bristol probably not the appropriate thread but.....Tommy Cookers wrote: ↑Mon Aug 30, 2021 10:03 am(though I don't see what that has to do with the Sabre architecture) ....J.A.W. wrote: ↑Sat Aug 28, 2021 12:32 amAs regards this view T-C, which you have reiterated in this thread, you might find this
period graph to be of some interest since it shows the Sabre's architecture did in fact
suit the volumetric efficacy of sleeve valves, versus big 2V hemi/4V pent-roof poppets...
the main 'American 2 valve poppet' engine then was the 1820 Wright Cyclone (made for 25+ years)
conveniently for this discussion it had the same bore:stroke ratio as the Bristol engines shewn
but more impressively the later Cyclones at takeoff ran at 2800 rpm - ie 16.3 m/sec or 3850 ft/sec mean piston speed
and the Cyclone supercharger efficiency was improved from 60% to 75% during WW2 - and more post-war
this improvement (as I said before) relieved the suggested problem of poppet valve breathing
over a few years the 1820 Cyclone doubled in power
logic says (though authors don't think of this) that historical improvements in strength ....
(allowing more piston acceleration/rpm but demanding relatively bigger ports/valves at some point)
imply that the ideal bore:stroke ratio would have increased over the years
ie that the old low bore:stroke ratio engines were right for their times
because (strength considerations say) rpm can increase in proportion to the square root of a stroke reduction ....
reduced cylinder volume (eg given bore:stroke ratio) increases breathing (relatively) of both sleeve-valve and poppets
reduced cylinder volume (eg given bore:stroke ratio) increases rpm so increased breathing is handy
these were the basis of Ricardo's and Heron's US Hyper program suggestions ie improving the volumetric 'efficiency'
ie displacement per unit time was raised by raising rpm - but unlike motor sport WW2 didn't have any engine rules
and increased bore:stroke ratios (as Napier) ie tend afaik to reduce the sleeve-valve's breathing (relatively)
(the port height reducing with stroke so port area doesn't rise with rpm rise)
though increased bore:stroke ratios (as Hyper) does increase the poppet-valve's breathing (relatively)
(so only 2 poppets were deemed necessary)
presumably cylinder size/bore:stroke reduction would allow poppet valve breathing to equal sleeve valve breathing
the Sabre was apparently intended for 4000 rpm but only got there via a convoluted and protracted route
T-C, there are other factors to consider, esp' given advantages in engine output/performance whichTommy Cookers wrote: ↑Sun Apr 24, 2022 10:35 ammaybe an original or replica Hucks starter
https://www.rafmuseum.org.uk/research/c ... s-starter/
I have seen them hand-starting it (that takes 3 people)
and ....my latest and overdue attempted refutation of JAW can be reduced to .....
the true measure of volumetric efficiency is the volume of air disturbed (to perform a given military task)
a volume wider and deeper with the Tempest due to its excessive weight - following from the Sabre's excessive weight
.. somewhat analogous to the arguments often used by F1 fans in favour of one car over another
that excessive weight could have been avoided by V12 close-pitched cylinders - ie having cylinder-side ports only
this of course reducing volumetric efficiency in the usual (meaningless) sense
the '2000 hp' class engine concept wasn't better than the '1000 hp' class unless its power:weight ratio was better
If you think the 'Hucks starter' is fascinating (& it was a method retained by the Soviets through