The Napier Dagger engine was the poppet valve H24 precursor to the sleeve valve H24 Napier Sabre. It was used as the Dagger III in the Hawker Hector and Dagger VIII Handley Page Hereford. It was the first engine with the innovation hydraulic tappets and was designed to metric dimensions by Frank Halford. Another innovation was the use of magnesium for valve train casting blocks, an approach carrying over to the Halford designed dH Gypsy King 12 cylinder engine used in the dH Albatross and Sabre engines. Making materials with differential expansion work in high RPM, air cooled designs was pushing the design envelope, and the Dagger tells a story of both Napiers as a culture and the highly competitive, company betting innovation culture characteristic of 20th century founder-directors in their prime. If anything, telling this story and permitting the young to be prodded into risk taking by historical example is worth forcing a Dagger back to life. There is some remaining footage of Hectors in flight with the astonishing, guttral growl of Daggers in full roar. The sound is like a deeper, more urgent, more three dimensional Merlin, twice the cylinders moving at a higher RPM, with an obsession around balancing every nut and bolt to get the short throw pistons up to 5000RPM. Through the kindness of the Napier Power Heritage Trust a Dagger powerbank core has been obtained. This might have originated from a famous scrapyard lost in the mists of time, but apparently a number of these engines ornamented said yard. Would it be rude to ask if anybody has any Dagger bits laying around? These would be gratefully reunited with the core in a long term project to get a Dagger going again.
By: powerandpassion - 31st August 2024 at 08:31
Thank you Fargo for the link. Dagger material will be in clumps of ‘known unknown’ engine detritus. Probably the only startling piece would be a 24 lead distributor cap, which the reasonable man might think belongs on a Sabre, but it does not. Perhaps an ‘unplaced’ Hobson carburettor that does not fit Mercury or Pegasus.
By: Fargo Boyle - 26th August 2024 at 18:40
I was going to suggest contacting Guy Black at Aero Vintage but I see that they’re having a stocktake at the moment so no sales currently. Might be worth keeping an eye on the website though
By: powerandpassion - 26th August 2024 at 11:30
If AI can cough up an old furball of a topic then I can too ! Surely somebody has some old Dagger bits used as a doorstop.
By: mark_pilkington - 14th September 2022 at 15:42
I recently purchased this 1926 Napier Lion Piston fixed to a base with a placard referring it to being “875 HP Napier Lion Schneider Trophy 1927” and hence it is assumed to be from a geared mk VIIB 875 bhp (652 kW) (racing) as fitted to the Supermarine S5 which won the 1927 Schneider Trophy air race, flown by Flt Lt S.N. Webster
The piston is a 5.5″ bore, stamped with an assumed manufacture date of 19.10.26.
By: powerandpassion - 31st August 2022 at 20:21
Thank you kindly Oracal. Ahh, Pobjoys, a terrible vice, a cruel addiction !
By: Arabella-Cox - 31st August 2022 at 16:31
All the APs are held at the RAF Museum. Some of those on the list are also held at TNA Kew.
Hector aeroplane with Dagger III engine. AP1518 Vol 1 (1937, 2nd edition). A copy is held at the RAF Museum. A copy of both the first and second editions (both 1937) is held at TNA, Kew.
BTW, I’m teetotal, but always hopeful that those Pobjoy docs may fall out of the storage facility…
By: powerandpassion - 31st August 2022 at 14:29
A very wonderful bibliography Oracal ! A brewery’s worth ! Is the AP list held anywhere ? Does this extend to the Hawker Hector ?
By: Arabella-Cox - 31st August 2022 at 13:30
P & P,
Dagger III engine, AP1531 Volume 1
Dagger III engine, AP1531A Volume 2 Part 1 General orders and modifications
Dagger III engine. AP1531 Volume 3 Part 1 Schedule of spare parts
Dagger III engine, AP1531A Volume 3, Part 1, Schedule of spare parts
Dagger VIII engine; AP1531B Volume 1
Dagger VIII engine, AP1531B Volume 2 Part 1 General orders and modifications
Dagger VIII engine, AP1531B Volume 2 Part 3 Instructions for dismantling, assembling, overhaul, repair and salvage
Dagger VIII engine, AP1531B Volume 3 Part 1 Schedule of spare parts
Napier Bibliography to December 1939 (source – Bibliography of Aeronautics, Part 34 Engines by Manufacturer)
There are several Dapper articles post-1939, but they rehash much of what is on the list.
By: powerandpassion - 31st August 2022 at 09:32
CD and Oracal, please do not Meghan this thread ! Rumours of it’s death are exaggerated, as Mark Twain might have said. I have used a bore gauge to explore whether the Rapier cylinder bore shows the same tapering and it appears not. I wonder if this is a tweak that carried over to the Sabre design of it was a problem only with early Y alloy pistons, superseded by the evolution of low creep piston material. Certainly machining tapering bores would have added complexity and hints at the reason why Napier engines are beloved by engineers and loathed by accountants. I am grateful for the posting of any information on the topic and any interest shown in it. Any poster wins a beer, but due to distance, quarantine and convenience considerations, I must drink this, in sufferance, on your behalf, but it is the thought that counts !
By: Arabella-Cox - 31st August 2022 at 06:28
What a snowflake!
By: Creaking Door - 30th August 2022 at 23:36
So, your last three posts; two patronising and one insulting.
Did you actually even read the words “finally found time” or wonder why the word ‘archives’ was in inverted commas?
Were you pleased, or even intrigued as to why, somebody had bothered to scan and post a drawing (even an unattributed drawing!) on a four-month dead thread?
By: Arabella-Cox - 30th August 2022 at 16:00
Unless the source of the information is given, it’s not of much use, is it? Point in fact is the large number of aviation books that lack such detail. Person “A” say his book says one thing, person “B” disagrees as his book say something else. Source? A bibliography which is of no use to anyone.
Showing source information is basic to historical writing, as is the type of source the information came from. Does it matter on a forum such as this? Yes, of course it does.
By: dhfan - 30th August 2022 at 15:05
You have to remember – Oracal knows everything.
By: Arabella-Cox - 30th August 2022 at 14:54
Well, not anything of much use.
By: Creaking Door - 30th August 2022 at 13:23
Frankly, it doesn’t surprise me nobody bothers to post anything on this forum any more.
By: Arabella-Cox - 25th August 2022 at 19:34
CD. Unless you attribute the source of a quote, it’s not of much use to your audience.
By: Creaking Door - 25th August 2022 at 19:03
Finally found time to search my ‘archives’:
“The bore tapers from the head end to the skirt, this being necessary to allow for expansion due to the heat generated at the combustion end under working conditions.”
By: powerandpassion - 21st April 2022 at 09:50
Dagger piston, very Lumsdenesque.
By: powerandpassion - 21st April 2022 at 09:48
CD, I hereby apologise to the late A Lumsden Esq and retract my absinthe soaked ejaculation in respect of metric dimensions for bore of Rapier and Dagger. To be sure the Rapier bore shewn below is 90mm-ish but this would obviously fit a smaller piston
By: Creaking Door - 19th April 2022 at 20:32
Napier Sabre piston for comparison.
Sign In
October 18, 2021 at 11:02 am