John Shipman's Engineering Notebook



John Shipman's Engineering Notebook


A notebook used by John for his engineering lectures.






31 handwritten pages


IBCC Digital Archive


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Ac2 J Shipman
Hut B.20 RAF Locking

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[inside front cover]

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[underlined] BASIC NOTES [/underlined]

[underlined] Hand Vice [/underlined] Body – steel with hardened jaws. Screw – mild steel.

[underlined] Bench Vice [/underlined] Body – cast iron, malleable cast iron, cast steel. Jaws – detachable, hardened steel with roughened surface. Screw – mild steel buttress thread.
Classified by weight of jaws (45lb – 4 1/2”)

[underlined] Hammers [/underlined] Head – high carbon steel faces hardened. Shaft - Ash or hicory [sic].
1/ Ball Pane. 2/ Cross Pane 3/ Straight Pane 4/ Hide Faced.

[underlined] Files [/underlined] [underlined] Blade[underlined] hard & brittle. Tang soft & tough
[underlined] Shapes [/underlined] – Parallel Tapered & Bellied
[underlined] Sections [/underlined] – Flat, Half Round, Round, Three Square, Square.
[underlined] Cut [/underlined] – Single Cut, Double Cut, Dreadnought, Rasp.
[underlined] Grade [/underlined] – Rough, Bastard, Second Cut, Smooth, Dead Smooth.
In describing state, length, shape, Cut or Grade, Section.

[underlined] Chisels [/underlined] Forged from high carbon steel, hardened & tempered at business end [deleted] left [/deleted] rest is left softer & tougher ground at 75° for hard steel 60° for soft & 46° soft metals. [underlined]
Types [/underlined] Flat, Cross cut, Diamond point & round nose.

[underlined] Hacksaws [/underlined] Frame, mild steel, Blades, High Carbon Steel. 22 to 32 teeth per inch for thin metal. 14 to 18 teeth per inch for thick metal.

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[underlined] Material [/underlined] High Carbon steel H & T at the business end

[underlined] Drills [/underlined] [drawings]

[underlined] Reamers [/underlined] High Carbon or Alloy Steel fluted to provide cutting edges
[underlined] Types [/underlined] Fixed Parallel, Expansion, Expanding, Shell & Taper. RAF Taper Reamers are measured by their diameter 1/3rd of the length from the smaller end.

[underlined] Threads [/underlined] BSW = British Standard Whitworth 55°
BSF = British Standard Fine 55°
BA = British Association. 47 1/2°
[underlined] American [/underlined] National Course [sic] & Nat. Fine.
[underlined] Other Types. [/underlined]
[drawing] square thread [drawing] Acme thread. [drawing] – Buttress usually found in vices

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[underlined] Taps [/underlined] Made from hardened steel in three sizes – Taper Second, Plug.

[underlined] A.G S Parts [/underlined] Light Alloy [drawing] Mild Steel – Plain
High Tensile Steel – [drawing]
High Tensile Stainless as above only with the letters S.S or Z on the head.

[underlined] Heat Treatment of Duralumin [/underlined]
[underlined] Annealing [/underlined] (to soften) heat to cherry red and then [deleted] quench in water [/deleted] allow to cool in air
[underlined] Normalizing [/underlined] heat to between 480° & 500° C and then [deleted] quench & scrub to remove salts. [/deleted] allow to cool slowly with ashes on fire.

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[underlined] PRELIMINARY ENGINES [/underlined]

[underlined] Olto 4 stroke Cylec [sic] [/underlined]
[underlined] Strokes [/underlined] [underlined] Induction [/underlined] to allow gases to enter cylinder.
[underlined] Compression [/underlined] which compresses gases against cylinder head.
[underlined] Ignition [/underlined] lights gases which forces piston down cylinder.
[underlined] Exhaust [/underlined] Valves open gases pass freely into air

[underlined] Inlet Valves [/underlined] opens 20° before TDC so as to be fully open in the suction stroke so as to keep up with the incoming mixture
[underlined [ Exhaust Valves [/underlined] Opens before BDC to allow the pressure of burnt gases to fall by atmospheric, this prevents back pressure on the piston when it has to push the gases out.
[underlined] Overlap [/underlined] is when both valves open [inserted] together [/inserted] before & after at T.D.C.
[underlined] Lead [/underlined] is when [inserted] exhaust [/inserted] valves open before [deleted] & after at [/deleted] B.D.C. Why? because it means greater efficiency to the engine.
[underlined] Lag [/underlined] Is when inlet valves remains [sic] open after BDC because it packs a greater mixture in the engine.

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[underlined] Valve timing on Gipsy Engine [/underlined]

1/ Find T.DC then DOR Exhaust valves always leads
2/ Turn crankshaft back 180° this puts inlet valves on back of cams.
3/ Trap 10 thou feeler in rotor arm rocker & valve head.
4/ Turn DOR to nip 5 thou feeler
5/ Take layshaft out to prevent crankshaft moving
6/ Turn 20° before TDC
7/ Replace layshaft gear.
8/ Turn back 45° degrees to remove backlash then turn DOR to 20° before TDC
9/ Turn back 180°
10/ Try 10 thou feeler then reduce clearance to 5 thou
11/ Then turn to 20° before TDC trying a 2 thou feeler.

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[underlined] Magneto timing on Gipsy Engine [/underlined]

1/ Find accurate TDC
2/ Set crankshaft 34° before T.D.C
3/ Check contactor breaker points with 12 thou feeler + or – 1
4/ Innsulate [sic] primary winding [deleted] screw [/deleted] by taking out centre screw and inserting oiled silk.
5/ Then turn magneto in DOR until the brush on the rotor faces the segment in distributor cover connected to the plug in No 1 Cylinder and offer up to magneto drive & get final adjustment with Simms Vernier Coupling (19 teeth = 18.9° per t & 20 teeth = 18° per tooth) [symbol] fine adjustment is .9
6/ Port Magneto is fitted first and it is different from the starboard magneto in as much that it as [sic] an impulse starter fitted. Turn through impulse starter (the impulse starter delays the passage of the space till just after TDC & also induces a hotter spark. for easier starting)

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[underlined] Questions & answers [/underlined]

? What is clearance
[underlined] Ans. [/underlined] Clearance is the space provided between 2 working parts
1/ To provide freedom of the movement
2/ Lubrication
3/ Variation of size or position due to heat or distortion

? What is a housing
[underlined] Ans [/underlined] Housing a hollow case the main purpose of which is to carry bearings or supports for working parts

? Splines
[underlined] Ans [/underlined] Splines are a series of axial ridges on the outer surface seperated [sic] by grooves of rectangular section to fit into similar grooved counterparts

? Serations [sic]
[underlined] Ans [/underlined] Serations [sic] are similar to splines but more closely spaced smaller & usually of different shape.

? Throw
[underlined] Ans [/underlined] Throw is the distance between the centre of a crankshaft & the centre of the crank pin

? Stroke
[underlined] Ans [/underlined] Stroke is twice the throw

? Backlash
[underlined] Ans [/underlined] Is the clearance between machine gear teeth

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or splined members, which must be taken up before driving in the reverse direction

? Preignition
[underlined] Ans [/underlined] Is the combustion starting before the passage of the spark due to some overheated part in the cylinder

? Volumitive Efficiency
[underlined] Ans [/underlined] Is the weight of mixture drawn into the cylinder, divided by the weight of a cylinder stroke volume full of air at standard atmospheric pressure & temperature

? Supercharging
[underlined] Ans [/underlined] Is the artificial filling of the cylinders on the induction stroke to a pressure greater than would have existed there.

? Bearing
[underlined] Ans [underlined] Bearing is the part of a machine which directly rotates a rotating shaft

? Burr
[underlined] Ans [/underlined] Burr is a rough or sharp ridge or projection at the edge of a working point or part

? Bush
[underlined] Ans [/underlined] Is a hollow one piece bearing

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? Cam
[underlined] Ans [/underlined] Cam is a projection from a revolving shaft for the purpose of controlling the extent rate of movement of other parts pressed against it.

? Bonding
[underlined] Ans [/underlined] Bonding is the provision of adequate conductors between operated parts of an engine to prevent any one part obtaining a higher potential than any other part with the consequent danger of sparking

? B.H.P (Brake horse power)
[underlined] Ans [/underlined] B.H.P is the useful horsepower obtained by an airscrew

? I.H.P (indicated horse power)
[underlined] Ans [/underlined] I.H.P is the H.P developed in the cylinder ie B.H.P/IHP = ME

? Mechanical Efficiency
[underlined] Ans [/underlined] Mechanical Efficiency is the amount of work done by the engine, divided by the amount of work developed in the cylinder.

? Screening
[underlined] Ans [/underlined] Screening is the provision of earth conductors round ignition apparatus to prevent interference with wireless transmission & reception

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? Compression Ratio
[underlined] Ans [/underlined] Is the clearance & swept volume over clearance volume i.e

? Detonation
[underlined] Ans [/underlined] Detonation is the instantaneous explosion of part of the mixture due to :–
1/ To [sic] high a compression ratio
2/ excessive boost pressure
3/ To [sic] advanced ignition timing
4/ Use of incorrect fuel.

[underlined] Piston Rings [/underlined]

Only 3 shapes joints – Scarf, Butt, & Stepped joint

The scraper above the gudgeon pin can be a U or Channel type, channel is drilled with holes. On bigger type engines another line of holes is drilled through below the piston on channel type. On late type engines no U type rings, type fitted are duel ring scalloped.

Gas rings are peined for elasticity. Rings made of closely grained cast iron.

Pistons are made from aluminium alloy.

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The joints are split sometimes at 45° & sometimes 90°, very brittle great care must me [sic] taken in removal & fitting.

The gap is tested by inserting in the cylinder & ensure it is square with the bore & measure gap with feelers.

Rings must be free to expand against cylinder wall. A small clearance is allowed between ring & groove to ensure piston doesn’t nip ring.

A 1° chamfer is made on outer edge of ring to allow wear to fit piston.

[underlined] Backlash [/underlined]

The clearance between meshing gear teeth or splined members, which must be taken up in the reverse direction before driving

[underlined] Arbour [underlined] An accuratley [sic] ground shaft for supporting & keeping in exact alinement machine parts or cutting tools during machining operations.

[underlined] Bearing [/underlined] the part of a mechanism intended to support a roting [sic] shaft.

[underlined] Bore [/underlined] the internal diameter of a cylindrical part

[underlined] Shimm [/inderlined] a thin peice [sic] of sheet metal cut to shape used between 2 surfaces to adjust accurately thin distance apart.

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[underlined] LUBRICATION SYSTEM [/underlined] (wet sump)


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[underlined] LUBRICATION [/underlined]

[underlined] Wet sump [/underlined] oil is carried in sump attached to engine

[underlined] Dry Sump [/underlined] oil is carried in sump away from the engine. Nessacary [sic] in Radial Engine to have dry sump because it has to have a small sump because it consumes more oil than it can carry in Wet Sump.

[underlined] Wet sump in Gipsy 1 [/underlined]

Oil is drawn from the sump by means of a Space gear type pump, oil enters between teeth & casing, and is then forced out with pressure. The intake is greater than the output because the outlet is restricted to build up a pressure. It then goes from the pump to a relief valve which is fitted to maintain a constant pressure of oil to all pressure fed bearing (Good oil is free from parrafin [sic] wax. Always use oil with low viscosity) Then from check valve to the filter chamber from there by an outside pipe to the gallery pipe to No 1 bearing first which feeds outside journal only, No 2 lead feeds No 2 bearing,

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& journal also No 1 & 2 Crankpin & big end bearing No 3 lead feeds just its own bearings, No 4 feeds itself & No 3 & 4 crankpins, No 5 feeds itself.

Then from [deleted] a [/deleted] No 5 lead by a pressure pipe to Magneto drive, there is also a pipe leading to a pressure guage [sic] in cockpit. Pistons, gudgeons & cylinders are sprayed from a calibrated hole in big end bearings, the edges of oil hole champhored [sic] to stop them chipping. Camshaft tappets & guides are fed by mist & splash from the big end. Overhead gears for valves are hand pressure fed. Gears in timing case all fed by the oil running over them.

[underlined] Dry Sump [/underlined]

The oil falls by gravity to a filter then from there to a space gear type pump, on which is the relief valve any surplus oil is passed back again to intake side, the [sic] past the check valve to pressure guage [sic].

The Whole shaft is hollow so one lead can feed all bearings. When bearings is fed it drops down and is carried away, back by scavenge pump to carburretor [sic].

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[underlined] TYPES OF PUMPS USED ON ENGINES [/underlined]

There is a pump know as a centrifugal pump these are efficient for cooling because they increase speed with the engine. When the pump is working with full throttle open it can pump approx 120 galls per min. The method to stop [indecipherable word] is to put restriction washing in block.

Fuel Pump is Diaphram [sic]
Space Gear Type for oil.
Plunger Type for oil
Excentric type pump is for oil.


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[underlined] INLINE ENGINES [/underlined] (things to swat)

1/ Setting of tappet clearance
2/ Changing broken valve springs
3/ Priming crankshaft with oil.
4/ Cylinder Numbering
5/ Cleaning agents
6/ Timing & running clearances
7/ Magneto timing & proceedure [sic]
8/ Tappet clearance & external connections
9/ Inserting scraper rings
10/ Examining & fitting airscrew hubs.
11/ Direction of rotation of crank.
12/ Layout of coolant system.
13/ Repacking pump gland.
14/ Prop. hub centralizing cone & locking sleeve.
15/ Relationship of stroke to throw.
16/ Meausuring [sic] backlash of gears.
17/ Grinding valve faces & seats.
18/ Testing crankcase.
19/ Testing faces & determing [sic] joint ring thicknesses
20/ [deleted] Mg [/deleted] Mag timing.

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[underlined] RAIDIAL ENGINES [/underlined]

1/ Changing broken valve springs
2/ Oil priming
3/ Position of nipples.
4/ Removal of pushrods from rods
5/ Setting of tappet clearances
6/ Cleaning Agents
7/ Finding highest Dwell.
8/ Checking angles of attack.
9/ Jointing material
10/ Hand oil priming

[underlined] COOLING SYSTEMS [/underlined]

Cooling systems is necessary to remove the surplus heat which would have otherwise cause [sic] trouble by destroying the properties of the lubricant and by distorting the working parts.

To [sic] much cooling leads to a loss of power & irregular running, a constant correct temperature is desirable.

[underlined] AIR COOLING [/underlined]

The air rushing over the exposed surface of the cylinder & cylinder head carries away the heat.

To get rid of the heat quicker fins are provided of large area but small thickness

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Control of air flow is affected by cowlings moveable shutters or gills the details differing from engine to engine. Sometimes a thermometer in the cockpit records the cylinder head temperature.

[underlined] LIQUID COOLING [/underlined]

The liquid contained in a jacket round the cylinder & cylinder head absorbs the heat and carries it to a radiator which has a large surface exposed to the air. Here the liquid is cooled & carried away by the air, then the liquid is returned cool [deleted] by [/deleted] to the jacket. Circulation is affected by a small centrifugal pump driven by the engine, by speeding up the flow less liquid can carry away the same amount of heat. Drains taps are provided at the lowest points in the system to ensure complete drainage when required.

[underlined] TYPE OF LIQUID USED [/underlined]

The liquid coolant used may be plain water, ethygene [sic] glycol or a mixture of the two. Ethylene Glycol has a higher boiling point & lower freezing point than water. A higher working temperature can be used without loss of coolant through cooling & damage by frost is prevented. The higher temperature of working makes the use of a lighter and smaller radiator possible. Water if used by itself must be pure & soft rain water is best, failing that the water must be tested for its hardness & treated by the necessary chemicals.

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[underlined] HOW TO FIND TDC [underlined] (PPI METHOD)


(a) a spring loaded lever pivoted in a block which screws into the plug hole is used, one end bears the piston the other moves over a scale. If the engine is turned till this pointer moves to its extreme position on the scale the piston is approx at T.D.C.


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[underlined] ATTENTION TO VALVES & SEATS [/underlined]

[underlined] The springs [/underlined] must be tested [deleted] by [/deleted] for strengh [sic], the test consists of loading spring with specified weight & notice that it has not compressed to less than a specified length.

[underlined] The valves [/underlined] are examined for pitting & burning on the sealing face Badly affected valves are reconditioned by a special grinding machine slightly affected valves are lapped to their valve seat.


[underlined] The valve seatings [/underlined] may be pitted & burned. Special cutters are used to remove bad pitting, slight pitting is removed by lapping. [underlined] Note [/underlined]:- before reconditioning the valves or seatings is done, always check the dimensions using the appropriate guages.

Lappings consists of rotating the valve forwards & backwards on its seating with a small amount of abrasive between. The valve should be held firmly on seat to help the abrasive to work (a special tool is provided) every few half turns it should be lifted & placed in a different position

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This helps to stop the formation of hollows. The lapping is continued until the whole face is making a perfect seating as listed by marking with a thin coat of liquid colour. Every trace of grinding paste must be removed when finished.

[underlined] Gaskets & Joints [/underlined]

Gaskets sometimes called joint washers are thin sheets of metal cut to shape & inserted between the face to make an airtight joint. (Aluminium & Vellumoid or a sandwich of asbestos rubber & other materials. Jointing compound is a sticky substance to form airtight joints.

Where accuracy of joints are nessecary [sic] dont use a gasket, but a very thin coating of jointing compound.

[underlined] Gears [/underlined]

Alinement is the most essential thing in fitting gears, also it is important to see the mesh is the right depth. Next take notice that the backlash clearance isnt too much or there is the danger of the teeth breaking off, allow just enough for lubrication & expansion.

The Type more common is Space Gear which are very effective. Bevel type gears are at an angle. Other types are Worm Gear, Helical Gear

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& Skew Gear which is very awkward because it will only drive one way & also there is a terrific amount of friction. Epycyclip [sic] Gear is an [sic] combination of gears to drive the airscrew

[underlined] SPARKING PLUGS [/underlined]


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Body – Machined steel with hexogan [sic] for spanner. One end of body as [sic] earth electrodes, also it as [sic] an internal thread for the centre of plug which is called the centre assembly. There is a small gap at the end of the centre pin to keep it off the earth electrodes, also the centre pin as a copper sleeve & [deleted] uns [/deleted] insulation to keep it off the body. The material used for this insulation is mica or at the present day aluminium oxide which is white, but plug makers colour it for identification purposes. The gland of the plug assists in making a gastight joint between centre Assembly & the body, also between gland & body is a washer usually made of iron soft, copper, phospher [sic] bronze & nickel, but in Mica insull a copper sleeve is used. In modern types of plugs we have what is called a [deleted] sleeve [/deleted] screen which is an extension from the gland nut in form of a tube to cover external insul. the reason for the screen is where radio is used. On inner side of screen there is a Mica lining to prevent H.T current from the terminal to the screen itself. The part of the plug in the cylinder gets a

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carbon coating, but in cases of Aluminium Oxide insul. it burns itself clean.

In using sparking plugs they have to be cleaned every 30 or 40 flying hours. Most common makes of plugs used by RAF. are Lodge K.L.G & A.C Sphinx.

The Al.XIDE type plug is called Seramic [sic] type. In order to fit different engines there are 3 sizes in millimetres 12-14-18

[underlined] Cleaning & testing of Mica Type [/underlined]

Cleaning, inspection & testing all 3 very important items. All Acoro engine plugs are made demountable ∴ a bench jig & stock & die nut must be used to dismantle & assemble. Mica type plugs, never mix up parts of plugs because they are not interchangeable.

Wash all parts in lead free petrol type used is DTD224 then proceed to clean plug parts on Plug Cleaning Machine. A split collet is provided to hold the plug in the chuck of machine. Clean insul. with No 0.0 Glass cloth & oil after this repolish with Crocus Powder & oil then

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for a final polish use rouge & oil or chamois leather which must be dry.

To clean carbon out of body of the plug, use wire brush or scraper.

[underlined] Inspection [/underlined]

Look for damage to thread & hexogans, cracking of metal parts & security of electrodes & condition of mica insul.

[underlined] Testing [/underlined]

1st test is called insul. test of centre assembly (Insul. test ring) to set gap of test ring insert ring guage the “not go” end should rest on the points & the “go” end should drop thro, spark jumps across gap is [sic] plug is clean & [deleted word] insul.

2nd test is for gland leakage, replace new washer every time the plug is dismantled. Test on gland leakage tester. Insert plug then pump up tester 100 lbs per sq inch, then immerse plug in a beaker of Sozol if it bubbles retighten plug in bench jig if it still bubbles plug is US.

3rd Test is sparking under pressure, test is carried out on Spark Plug Tester

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pump up tester up to 100 lbs 100 lbs per [symbol] inch window to look in for protection of flying glass. Then apply H.T current on plug terminal, observe sparking earth electrodes & centre pin failure to spark at 12,000 volts means a U.S plug.

Mark all US plugs with red paint.

[deleted] [underlined] MAGNETO’S [/underlined] [/deleted]

[underlined] Ceramic Type Plugs [/underlined]

Aluminium Oxide which form insullation [sic] goes through a process of cindering which means a very high temperature. The above plugs are sometimes called Cinder Aluminium Oxide Type, it is very hard & as a high melting point up to 4000° C it also wont burn & will not allow H.T Current to flow through it & it is not affected by fuel which is used in modern engines.

Insullator [sic] is light coloured. KLG are White LODGE pink, AC Brown for recognition.

It is very little defficant [sic] in construction

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from Mica Type & when run at very high temperature any deposit on insullator burns off.

Three main items are Cleaning Inspection & Testing. Sand blast cleaner for plug with 1lb Silver Sand in it. Four precautions when using 1st Correct Air Pressure 2nd clean it only for 10 seconds maximum time. 3rd Apply compressed air intermittanlly [sic]. 4th Rotate plug while cleaning. Body is cleaned with sand blast as above.

[underlined] Inspection [/underlined] Much as on same line as Mica Type. Inspection Thread, Hexagon & Body for cracks also insullation, screen & mica-lining & gland washers.

[underlined] Testing [/underlined] is carried out in 3 stages as later type.

1/ Assemble on Constant Torque Fixture with weights as specified.

2/ Gland leakage test @ 150 lbs per [symbol]” with white spirits DTD 224.

3/ Sparking under pressure @ 100 lbs per [symbol]” constant sparking at plug electrodes.

[underlined] Marking [/underlined] Etching Pencil, centre punch & file, red paint for US plug.

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[underlined] Life [/underlined] 180 Flying hours

[underlined] Inspection [/underlined] 30, 60, 90, 120, 150, 180

[underlined] Cleaned [/underlined] 30, 60, 90, 120, 150, 180

[underlined] Gap Setting [/underlined] 15 thou gap on all plugs is standard distance. Errosion [sic] is the burning away of electroe’s [sic] in order to check gap a gap guage is used 12 thou at one end & 15 thou at the other.

1/ Oval Centre Pin applys [sic] only to 12 mm Mica Type

2/ Hammer & Pin Punch for Heavy Nickel Electrodes

3/ Gap Setting disc & setting tool

4/ Lodge tube & lever

5/ KLG Composite Gap setting tool

6/ AC Gap setting Pliers

High Voltage test of Bronze Harness Insullation

1/ High voltage test plug.

2/ Earth body of H/S Mag to A/F

3/ Connect lead to dist. segment & place plug on appropriate plug connected

4/ Turn H. Starter Mag Indication: - constant sparking = good innsullation.

5/ Test all leads same way.

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[underlined] Old type CISE [/underlined] End of block is split like clamp. first slacken locking nut, then slamping [sic] screw and adjust to .012.


A [underlined] CLEANING [/underlined]

1/ Wash in lead free petrol.

2/ Wash in hot water 70 to 80° C

3/ Rinse in fresh hot water

4/ Dry thoroughly

B [underlined] INSPECTION [/underlined]

1/ Inspect block for warping, distortion cracks & clearness of vent holes.

2/ Inspect segment & rotor brush for excessive burning & corrosion

3/ Check for good connection of H.T Leads (Lamp & Battery or visual)

4/ Check width of auxhilary [sic] spark gap .011 to .019 is correct width.

[underlined] Lubrication of Magnetos [/underlined]


1/ Inductor rotor & distributor rotor ball bearings are grease packed by makers or M.U. sufficient for 500 FH.

2/ Rocker arm wick 1 drop of oil at 1.1.0

3/ Cam lubricating pad is grease impregnated

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and is changed complete with clip every 120 hrs

4/ [underlined] Contact Breaker [/underlined] base spigot wipe clean & resmear with lightly with grease H.M.P at 1.1.0.

[underlined] N.B [/underlined] Always refer to instructions & above all. avoid excess. The oil used is D.T.D. 109 Winter Grade

[underlined] BREEZE & MARCONI HARNESS [/underlined]

7 Millimetre Lead for low voltage current.

9 Millimetre Lead consists of stranded wire which can be copper but later type is stainless steel, round that is wrapped pure rubber & round that a coating of vulcanized grey rubber & on top of that is wrapped cambric tape & a layer of metal braiding which keeps in magnetic field when current is passing through

[underlined] Continuaty [sic] & Insul Test of H T Leads [/underlined]

Put lamp on each end of lead & take out the 1 thou Holmes resistance block if lamp lights it a good lead.

[underlined] Insull Test as on Plug Bay [/underlined]

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[underlined] Advancing & Retiring Magneto’s [/underlined]

1st method contact breaker.

Run normally in advanced position because the engine is run at high speed.

To advance move base opposite DOR

To retire move base DOR.

Advancing moves contact breaker round cam ∴ advancing opening of points.

But it affects internal timing & gives weak sparks where large are required.

[underlined] Automatic Timing Device. [/underlined]

One part is driving members with 2 small cams fitted. The driven member as 2 weights with 2 small rollers, also a serrated coupling for small measurements. Used for advancing mag in relation with the engine. Advantage, does not affect internal timing keeping advanced all the time.

[underlined] H.S Magneto’s [/underlined]

2 sparks per revolution, every time handle is turned the E.B points turn 5 times ∴ 1 turn of handle gives 10 sparks this is operated by gears inside mag. From mag there is 2 leads to dist rotor of main mags.

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[underlined] CARBURETTOR’S [/underlined]


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[underlined] Carburettor [/underlined]

Petrol wont burn unless Xd with air.

The mixture of air & fuel is always taken by weight, because when engine starts climbing weight of the air decreases. At normal atmos pressure, 15 lbs of air is needed to burn 1 lb fuel [deleted] when ready for combustion. [/deleted] Less air is needed to burn fuel when under compression ∴ only
13 lbs of air needed to burn 1 lb fuel when ready for combustion this is correct Xture. 10 to 1 for rich Xture. Weak Xture can be 16 or 17 to 1 needs more air, sometimes as high as 22 to 1.

[underlined] Fuels [/underlined] [deleted] 1 [/deleted] 73 octaine [sic] (antidetonation properties) colour should be orange. 2nd 87 octaine either red or blue. 3rd 90 octaine is mixture of [deleted] 1 [/deleted] 87 & 100 octaine anything from the blue green to brown. 4th 100 octaine which is green.

[underlined] Simple Carburettor [/underlined] worked entirely an [sic] pressure differences the whole time with U tube principle. A slight restriction is made in air intake to cause a low depression round fuel pipe. The reason is the air as to pick up speed through the

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restricted part to make up the same amount of pressure, the other side, this resistance is called the CHOKE or VENTURI.

[underlined] Disadvantages [/underlined] the more the throttle is opened the richer the Xture gets. A Diffuser is fitted to help this it controls the amount of mixture drawn in the air intake to make an even ratio with the air drawn in.

During the cruising range flying is done on economic Xture 14-15 to 1, with a weak Xture a slighty [sic] slower spark because of more air than fuel ∴ mag as to be advanced. Normal Xture burns normally. Rich Xture gets a slower flamerate [sic] than the normal.

[underlined] Slow running [/underlined] pilot jet is put in to give a correct Xture for very small throttle openings. Pilot jet is taken up to depression against edge of butterfly throttle & down into the float chamber.

[underlined] Pressure Balance [/underlined] your 13 to 1 mixture strenghth [sic] is maintained by constant pressure difference between choke & float chamber. Pressures in the air intake vary according to flight. Increase or decrease of pressure will vary Xture strength owing to increase & decrease of pressure

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float chamber & air intake are joined together by pressure balance passage, thus ensuring constant pressure difference

[underlined] CLAUDEL HOBSON CARBr A.V.T 80.B [/underlined]
(A V.T Aero Vertical Twin) vertical means up draft. 80 ins the diameter of the throttle tube in millimetres. It is a double carbr made in 2 halfs [sic] the joint is made of vellumoid glass jointing compound.

[underlined] Bottom Half [/underlined] are 2 pipes which leads to the float chamber these are the Pressure Balance Passages. There are 2 float chambers because when the aircraft banks the centrifugal force isnt enough to keep the fuel at the bottom, the 2 float chambers doesnt allow 1 feed pipe to starve. The floats are made of cork in 3 layers (a laminated cork float).

The needle valve is made of stainless steel. In the base of each float chamber there is what is known as a Main Jet Wells which are put there to collect all foreign matter which might get into the jets & block it up. Before removing plug for cleaning ascertain the fuel is turned off secondly

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have a receptacle handy for the fuel which will drain out of the chamber. By removing the whole of the main jet well you can remove the main & S R Jets without splitting the carbR. To clean jet rinse out in fuel if it then isnt clean apply compressed air reverse direction of flow. [underlined] Dont [/underlined] use any metal to clean out the calibrated hole. The washer on top of the jet well & should be removed each time (made of cork)

[underlined] Slow RUNNING [/underlined]

The slow running jet is only a small restriction in the tube itself the whole thing is screwed into the main jet which is screwed into the diffuser body. The body is screwed into the top half of the carb. The top of the SR tube is connected to the SR Nozzle box. In between Butt Throttle & throttle tube is clearance of 6 thou when engine is slow running. The only way the fuel can get into the SR jet is through the M. Jet holes. The depression exists throughout the whole length of the throttle this is when the engine is SR. Before the fuel gets to the nozzle box there is some

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air already Xd with it through a hole in the tube which is put there to vapourize [sic] the [deleted] the [/deleted] fuel before it arrives at the box. You also get a very rich [deleted] Xture [/deleted] vapour from the hole to the top through the air coming in from the main jet. The fuel goes evenly through the holes in the throttle & so gives an even distrib of the Xture. Slow running Xture is rich for 2 reasons. 1st we require a rich Xture to get a very even burning rate as the engine is only ticking over slowly. 2ndly is because of condensation when the engine is cold. The xture a SR is rich enough to start with so that by the time it reaches the cylinder it is correct. When the engine is hot you do not let it stay SR because of rich Xture doing damage to the engine.

When the throttle is opened up the depression will fall on the lower hole in the nozzle box. The second hole is put there for more of an overlap between jets so as there are no flats spots. The fuel will flow through both holes until the lower choke depression is great enough to draw

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the Xture through the main jet

[underlined] Slow Running Cut off [/underlined] is for stopping the engine providing the throttle is in the slow running position. The waisted portion does not cut off the Xture but when pulled out a wider portion at this end stops the flow of the Xture. Pull the cut out first then stop the flow of the Xture. If engine catches fire cut off fuel & then open the throttle. Fuel must not be cut off damage to the fuel pump which is lubricated by the fuel flowing through it.

[underlined] Main Jet & Diffuser [/underlined] forms 3 functions

1/ It corrects the Xture for all throttle openings after slow running.

2/ It vapourizes the fuel from the main jet

3/ It provides a reserve of fuel for acceleration.

4/ As throttle opens depression [inserted] in [/inserted] choke & diffuser draws air through P.B.D which picks up the fuel in vapour form.

5/ As throttle opens level of fuel with drop in diffuser because the engine is demanding for more fuel than the main jet will pass ∴ more holes all uncovered in diffuser this

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lets in more air to break down the depression & ∴ break down the fuel supply this happens only on cruising range. The diffuser [deleted] helps [/deleted] prevents you getting to [sic] rich a mixture when you open the throttle. In the cruising range the main jet is calibrated to give us an economical Xture.

[underlined] RATING [/underlined] is the maximum power position

[underlined] Power JET [/underlined] comes into operation when the lever is moved from cruising to rating. The additional fuel wanted to mix with the change of air due to the opening of the throttle at maximum speed. The power jet is operated by means of a cam and the throttle layshaft. It is so timed that when the lever is moved to rating position in the cockpit a cam works on the valve head, as the cam is pressed down the valve opens & allows fuel to pass thro’ a waisted bolt & by pipe to the choke

The power jet is always delivered from the starboard side.

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[underlined] ACCELERATOR and DELAYED ACTION PUMPS [/underlined]


When engine is running at any throttle opening we should be producing from carbR. 15 to 1 ratio. Acc. Pump if fitted to overcome a flat spot, when the throttle is opened, [deleted] the air increases its weight of flow [/deleted] caused by temporary weakening of the Xture due to the fact that when the throttle is opened the air increases its weight of flow very much faster than the fuel does. The acc pump is provided to mass discharge the fuel to overcome the

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temporary weakening of the mixture. The delayed action pump operates after the accelerator pump & it corrects the Xture by supplying a measured amount of fuel during the remainder of the accel period. We want the accel pump to come into operation every time the throttle is moved so it is connected to the throttle layshaft from which it is operated. The accel pump is held to the Del. action by means of a distance rod & spring which measures the amount of fuel Both pumps [indecipherable word] in a housing which is bolted to the bottom of the float chamber.

The fuel flows through accel pump chamber down to the D.A pump chamber from there it can go by a duct to a N.R Valve underneath & into the bottom of the D.A from there it is delivered through a N.R. Valve by a duct to the port delivery tube. The fuel on top of the pump is also delivered to the [deleted] top [/deleted] port chamber by means of a N.R. Valve. The pressure that holds the D.A pump back is the fuel having to go through a very small hole, with the pressure of the top

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S.L valve pressing & holding it back but as soon as the fuel between the 2 valves is released it then comes into operation

[underlined] MIXTURE CONTROL ALTITUDE [/underlined]

As the aircraft climbs the density of the air decreases this gives us a rich Xture. So we have to cut down the amount of fuel supplied this is not weakening the Xture but correcting the weight of both are in direct relation with each other.

There are 3 types of mixture control.

1/ [underlined] Variable jet type [/underlined] fitted so [deleted] as [/deleted] to SU CarbR & is entirely automatic, its worked off the old barometer principle, fuel is controlled as aircraft climbs the needle is lowered into the jet further & controls the amount of fuel supplied.

2/ [underlined] VARYING AIR PRESSURE CLAUDEL HOBSON [/underlined]
[underlined] Air leak or bleed type [/underlined] On modern carbs the Xture is controlled automatic. In this type we break down the depression over the diffuser by allowing the air from the pressure balance passage to leak through a mixture control cock. The pressure

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passage leading to the centre of the cock as the cock is rotated we can bring the 2 square holes opposite 2 others in the cone & from there they lead down to the area above the diffuser so it depends on the opening of the cock on how much air is let down over the diffuser. As the aircraft raises [sic] the cock is Automatically opened & more air gets into the diffuser ∴ breaking down the depression but the amount of air must be calibrated otherwise the fuel would cease to flow.

[underlined] Vacuum Type [/underlined] comes into operation at roughly about 15’000 ft when the control cock is coming into the fully open position, vacuum type is automatic bought into operation, the small hole comes opposite the small duct leading down into the float chamber. This cock is operated from the Xture control layshaft.

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[underlined] SUPERCHARGING. [/underlined]


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[inserted] 9/32 F.1.7 [/inserted]

[underlined] SUPERCHARGING A.B.C. [/underlined]

As the aircraft climbs it is lowering the compression ratio all the time owing to the decrease of pressure of air. The only reason for supercharging is to try to maintain a same pressure in the cylinder at a high altitude the same as at sea level which is 14.7 lbs per [symbol]”. We supercharge an engine by using a revolving fan which rotates in a very small housing. The outlet from the supercharger is taken to the inlet valve where the pressure is built up. The impeller is driven from the crankshaft through a train of gears & can run anything from 5 to 12 times engine speed On a single speed supercharger 5 to 7 times engine speed. To save supercharger from backfiring with the engine it is driven through 3 centrifugal clutches. At low engine speed the impeller can be held stationary. The air intake comes in the centre of the impeller where it can pass between the centre of the vanes where it is thrown into the casing as soon as the

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engine is made faster the needle on the boost guage goes round to + and the impeller revolves instead of idling because the gears come into operation. When this happens the air is flung off the end of the vanes into the balloon casing where it pushes the air to the valves, then the pressure is recorded on the guage, O being atmos, pressure ∴ the guage will read plus. The more the throttle is opened the more gas passes into the cylinder ∴ making the engine go faster & makes the impeller run faster causing more boost pressure.

[underlined] Automatic boost control [/underlined]

Controls the amount of air allowed into the induction stroke of the cylinder. The A.B.C controls the B. Throttle. The snag of supercharging is that it as to be same at sea level as at high altitude but it enables it to become airborne quicker. The A.B.C is fitted on the rear cover just above the CBr. main components :– aneroid which fits into

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the aneroid chamber. And that is fixed to the lid of the chamber, attached to the bottom of the aneroid is the piston valve which works in a sleeve. On one side of the casing is a cylinder wherein a Servo Piston works, the union on the side is joined up to the inductor system of the pressure side of the supercharger. Pressure oil is fed into the system by 2 holes the top one to let in oil & the bottom to the scavange. The A.B.C is adjusted to the amount wanted by the engine. Screw in for high boost & out for low.

The time when the throttle is full open at rated altitude is the height to which the engine can maintain its Sea level power.

To obtain maximum power for take off we overide [sic] the boost in other words we give the engine more boost pressure than it was originally designed. To do this we push the whole aneroid & piston valve down by means of a lever which presses on top of the aneroid ∴ opening the throttle. It takes more pressure to bring the piston valve

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back to normal position when the aneroid is depressed.

Detonation will set in with overiding [sic] the boost, it is cured by cooling the inside of the piston with fuel. The Xture is corrected for take off with the Enrichment [deleted] valve [/deleted] Jet & provides additional fuel for internal cooling of the cylinder a rich Xture as a slower flame rate than a normal Xture this cuts the temperature down.

[underlined] Enrichment jet [/underlined] cam, spring loaded valve same as power jet, it is on the port side of the float chamber, into jet housing, when the valve is compressed by cam, it allows the Xture to flow to the jet in the port intake. Boost Overide & Enrichment jet are both operated from the Xture control layshaft. To overcome any detonation the enrichment jet is bought [sic] into action before boost overide.

[underlined] Adjustments [/underlined]

[underlined] Slow running [/underlined]. Is a small screw on the end of the butterfly throttle shaft (on port side) this adjusts the slow running speed by

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varying the gap between butterfly throttle & throttle tube. By screwing it in the gap is made wider ∴ letting more fuel in making the engine go faster.

[underlined] Power jet adjustment [/underlined] adjusted to come into operation at 42° of butterfly throttle opening, adjusted by means of a serrated ring

[underlined] Boost Overide [/underlined] is timed to come into operation at [deleted] a [/deleted] take off after the enrichment jet, it E.J is timed to come of 2 marks after arrow

1/ Cam on EJ VALVE
2/ EJ in operation
3/ Forks just on aneroid
4/ B overide in operation


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[underlined] SHOWING BOOST STAGES [/underlined]


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[underlined] DIFF BETWEEN 80B & 85E CARBS [/underlined]

1/ The size of the throttle tube is 5 mm wider than the 85E.

2/ IT also has larger jets.

3/ In the 85E the enrichment valve is incorporated in the casing.

4/ In the 85E we have 3 delivery tubes, P. Jet Starboard side, Enrichment jet, Port Side & the Acc & DA pump have a pump seperation [sic] on the port side.

Round the throttle tube is fitted an oil filled carbR jacket, the hot oil is pumped in one side & out the other back to cooler & sump, this is to try & prevent icing up of butterfly throttle.

[underlined] Test on jets [/underlined]

[underlined] Acc Pump [/underlined] Move throttle from closed to open with the engine stationary, 3 times only & observe petrol in air intake. Allow sufficient [deleted] for [/deleted] time for petrol to evaporate before the engine is started.

[underlined] Power Jet [/underlined] 1/ Do it by flowometer [sic] in the feed pipe, run engine, then move throttle lever into the rated position, note amount oflow [sic] with power jet in rated, then stop the engine remove power jet & put a dummy power jet in, run engine again, & note the difference of flow it should be 8-7 pts per minute difference.

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2/ Practical way with engine stationary, switch off fuel supply & put throttle lever in slow running position, move the lever to cruising position, in this position the main jet should only be operating, when the throttle is in this position there should be no fuel flowing from the plug holes.

[underlined] Enrichment jet [/underlined] with the throttle in cruising range, & when the jet is removed there shouldn’t be a flow of fuel from the jet.

[underlined] Hot & cold air intake [/underlined]

Fitted to carb is an attachment which gives us an hot & cold air intake. The bottom cowling is the cold air intake. The two on either side are the hot intakes. Either can be banked [sic] off by two securing plates on the inside. The hot air intakes are in a position behind nos 5 & 6 cylinders. The hot air intake must not be used for starting the engine because if the engine backfires you are liable to get a fire inside the cowling.

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[underlined] The A.V.T. 85 M.C. Carburettor [/underlined]

The operation is the same as 85 E type carbR. The jets are all on the base of the float chamber altogether. The jets are all marked for identifaction [sic].

On the back is 2 automatic controls, one is Automatic Mixture control which automatically opens the cocks this is on Starboard Side, on the port side is the A.B. Control. The [sic] are 2 miture [sic] control cocks, 1 on either side, no vacuum type M.C is fitted. The slow running cut off is controlled by a lever at the side of the carb. There is only 1 operating shaft on this which is controlled from the cockpit, this is the throttle layshaft

From Starboard to Port it Operates.

1/ Enrichment jet. 2/ Acc & D A Pump, 3/ Then the 3 cams for 3 stage boost control. 4/ The cam for the power jet. On either side of front carburettor are 2 pipes, 1 inlet & 1 outlet for oil which operates the Automatic Controls. At the bottom is the 2 Servo pistons. There is a seperate [sic] main & slow running jet. The power jet is delivered from the port side.

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[blank page]

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[indecipherable words]


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[inside back cover]



John Shipman, “John Shipman's Engineering Notebook,” IBCC Digital Archive, accessed January 27, 2023,

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