Kermit Weeks Napier Sabre hot-rod?.

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

Kiwiracefan..have you seen, or operated the display Bristol sleeve-valve unit at the Wigram RNZAF museum?

It has a smoothly precise mechanical action compared to radically cammed high spring-rated poppet valve mills..

From 'Some Unusual Engines' P.62;

"All that can be said in argument may be summed up by the facts that Bristol ran one of their 6.5 inch sleeves up to 8,000 rpm in a single-cylinder test engine without anything going awry, & that the Napier Sabre could blip up & down the rev-counter scale like a car engine."

" It is worth pointing out that sleeve valves featured in the most powerful piston engine to fly [...Napier Sabre] & in the most reliable [the last version of the Bristol Centaurus, which holds the record for piston engine overhaul life [TBO] at 3,000 hours], & have been proven to allow higher compression ratios, higher exhaust back pressures, & higher outputs, for a given capacity or weight than poppet valves could."

& I would submit that all aircraft engines ought - as a matter of principle - 'be very carefully looked after'..

[Apteryx]

Re: Kermit Weeks Napier Sabre hot-rod?.

Apteryrx, do you know if any modelling [virtual or scale-flight] was done on the flying characteristics of the N-Heston?

Sorry, I've lost track of the friend I had, that was working on the project. I know they were challenged with design changes, after they were unable to come up with an engine. I don't know of their progress since then.

Paul

[BillRo]

Re: Kermit Weeks Napier Sabre hot-rod?.

Actually the Napier Heston crew in Sydney have a couple of Griffons that they are planning on using with a front case to swing a single prop.

BillRo

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

Thanks guys for the replies N-Heston-wise..

I guess an issue with flying `30s race designs with actual high torque 2,000+hp engines is in the yaw/directional instability inherent in short-coupled airframes with small tail surface/keel areas..

..lessons learned in late WW2 service fighters which mostly needed significant stretch in those aero-zones..

..sometimes not a good thing to test new airframe & engine together esp'in the case of the Napier Sabre, since the
Heston Racer, Martin-Baker MB 3, & Typhoon prototypes all crashed, putting their programs in bother..

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

Kiwiracefan, this is how a Kiwi Tempest pilot - Ron Dennis - regarded [& hammered] the Napier Sabre..

"The engine loved tough handling & never objected to maximum revs or boost for extended periods".

Ron & his wingman went in hot pursuit of an Me 262..
.. running their Tempests WFO for 50 miles to catch it & shoot it down..

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

& This is what long-serving [he made C.O.] 486 [NZ] Sqd pilot Jim Sheddan wrote in his book 'Tempest Pilot'..

"Of all the Allied fighters in action during the last 12 months of the war the Hawker Tempest,
powered by a Napier Sabre sleeve valve engine was in a class of its own.

In the hands of an experienced pilot it was more than a match for any aircraft flying on either
side of the lines." [at its rated heights]..

He adds..

"...the procedure was to to cruise at about 8,000ft. At that height it was possible to
see without being seen, dive almost vertically when a speed of about 600mph would be
reached, then after the attack, zoom back to our original patrol height.
The main advantage for the Tempest for this form of attack was its ability to pick up
speed when diving, its steadiness & ease of handling at high speeds & its initial zoom climb.
Pull the nose straight up & it fairly rocketed to the 5,000ft mark, the height where the
ground tracer fire was beginning to curl over. Above this height & the light flak could not touch it."

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

In the `50s the RAF were still utilizing the Sabre powered Tempests in the air-to-air gunnery training role
-as a drogue target tow plane..

A visitor asked if the old piston fighter was up to providing realistic training for the jets..

He was told..

" Make no mistake, without the drogue those Tempests have no trouble giving the
Vampires the run around at low level."

The Tempest has a placarded Vne of 540mph IAS below 10,000ft..not bad for a WW2 aircraft..

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

& vs P-51..

Another Kiwi ace [Bob Spurdle] wrote in his memoir, 'The Blue Arena';

" On Sortie No 551 some USAAF Mustangs jumped us.
Enraged, I turned on my particular tormentor & scared him
fartless by firing bursts 1st on one side then the other,
while he twisted & turned helpless against the far superior Tempest.
Formating alongside, I shook my fist at the stupid jerk & then
zoomed away.
We should have hacked a few down to teach them aircraft recognition.
We were sick of their trigger-happy stupidities."

[AAFO_WSagar]

Re: Kermit Weeks Napier Sabre hot-rod?.

LOL... it's a good thing those American's and their P-51's were there to fend off the hun so the Brits had time to develope that aircraft!!

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

Ah, yeah Wayne,
- I think ol' Bob was maybe a bit grumpy after 550 operational sorties..

..the 1st of which was flown fending off the Hun..during the Battle of Britain..

[& he survived having a Spitfire - P 7364 - disintegrate on him in a WFO dive while chasing a 109 in the B.o.B. too]..

Has anyone got a top-flite race performance out of an All-American GM-Allison powered Mustang?

What happened to those late ADI Allison V-1710-engined F-82s?

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

For anyone interested in some 21st Century revisionist/academic views on sleeve vs poppet valve aircraft mills..

http://www.enginehistory.org/members/articles/Sleeve.pdf

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

The venerable Green listed the wartime Tempest V as good for..

"392 mph at sea-level; 416 mph at 4,600ft; 435 mph at 17,000ft."

& per ' Flight ' Oct 7 1948 P.422, [-on line archive]..

The postwar standard Tempest 6 was tested with a Sabre 7 running + 17.25lbs boost,
giving..
418 mph at S-L; 435 mph at 5,000ft; 455 mph at 17,000ft.

vs P-51H [at Wright AFB] on test at 90in/hg,
giving..
401 mph at S-L; 431 mph at 6,800ft; 451 mph at 21,200ft.

So the Napier Sabre could have some Reno potential, maybe?

[boomtown]

Re: Kermit Weeks Napier Sabre hot-rod?.

I have a question: Does this engine fire 2 pistons simultaneously? That would make sense to me. Basically you have 2 12 cylinder banks one on top of the other firing a cylinder on each at the same time.

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

The Sabre has its twin crankshafts geared/timed 180`from each other to allow optimal harmonic/balance factors.

They run 120`[even firing] crank throws - so firing order is equivalent to a V12.

Listen to the musical howl they make in that recognition video, typical of 120`triples & multiples thereof.

Incidentally, even with only 4 cylinders, the TZ 750 Yamaha fires 2 simultaneously, being a 180`phase 2 cycle mill..

[J.A.W.]

Re: Kermit Weeks Napier Sabre hot-rod?.

If you want to see another [very interesting] way of firing 2 at once..

Check out the Napier Deltic mill..

http://www.wis.co.uk/justin/deltic-engine.html

- As used by the USN in the `Nam - to power its 'Nasty' class fast patrol boats..