This is the engine which may revolutionise speedboat racing
The engine used inwards the record-breaking skiff Southern Maid is fitted amongst a "Holden" engine adapted to "Dunstan" rotary valve and fuel injection equipment for which patents have been applied.
Advantages of a rotary valve are: Almost unlimited breathing capacity, liberty of reciprocating motility, absence of hot spots, compact combustion chamber, whatsoever desired control of turbulence. The results are: High ability outputs (limited entirely by balance too strength of crankshaft, con rods, bearings, etc.), high antiknock rating and high efficiency. The existing engine at xi-i compression ratio volition run on whatever fuel from second grade petrol nigh 75 octane) to pure Methanol too running changes tin can live made past manual control of fuel pump setting, as no critical jet sizes are involved.
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This shows a Holden engine conversion on the dynamometer simply alongside the rotary valve head removed. The engine was after dry out-heart ped past driving the pumps off the camshaft gear. Swashplate fuel injection heart is shown (driven at half speed). This has a distributor to ensure fifty-fifty furnish to high or depression cylinders whets starting just has no useful use under normal running conditions when the jets could live sprayed continuously and simultaneously. |
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This is the beginning Dunstan rotary valve applied to a full sized engine. This version had vi classify floating cylinder heads. The fuel injection is past Dunstan swash plate type pump. Mixture control past swash plate angle is not shown inwards the thought |
Most of the running has been with a standard Holden half dozen volt curl ignition system alongside 12 volt applied. However, between raising the 135 cubic inches restricted hull course tape from the previous holder'sec 53 1000.p.h. to lx.624 together with our latest 63.015, we fitted a Lucas magneto which is undoubtedly preferable to scroll ignition at speeds over 6000 r.p.k. Most of the racing is done on standard or super petrol (near eighty octane) amongst improver of A pint 0/two-stroke oil per gallon for valve lubrication; i pint for touring. Methanol fuel, because of its high latent caput and rich mixture, increases output well-nigh 12 per cent, over petrol as well as this fuel is used for special occasions. About ii per cent. of castor rock oil is added to the Methanol to lubricate the valve which incidentally never shows whatsoever sign of vesture or scuffing. A few foreign bodies such as jet tubes have inwards fact been through the valve and cylinders without affecting seal or performance. This is of form not recommended performance procedure. It is possible of course to correspond a metering lubrication organisation of depression consumption to eliminate the involve for adding oil to the fuel. Although alongside self-mixing oils now available petrol/rock oil is no bother. A cleaned upward version of this design is beingness position into production for the Holden engine and this volition live sold to speedboat, road and rails racing machine enthusiasts or private motorcar owners on the basis of valve head solely, or head plus enclosed front end terminate cause for valve together with accessories, addition fuel organization if required, or consummate dynamometer tested engines suitable for oars or boats. Many orders in addition to interested inquiries have already been received as well as efforts are being made to expedite completion, testing and manufacture of the new model. Such a valve could be fitted to any type of engine, using one valve for each banking company of cylinder in the example of a Vee engine. However, all acquaint efforts are existence concentrated on "Holden" which is readily available at low price in addition to fits into contest classes rattling good in addition to besides stands a remarkable amount of "hotting-up" for a production automobile engine. The valve is of gray cast iron together with runs the total length of cylinder block in addition to is hollow for H2O cooling. It runs at a quarter of engine speed in addition to has 2 opposed pockets at each cylinder station. These pockets operate on succeeding cycles. The master engine has six sort out lower heads inwards floating contact amongst the valve. The novel version has 1 aluminium head, split on centreline of valve, alongside half-dozen floating inserts which primarytain valve contact in addition to seal. The new head could be fitted inwards lieu of the ordinary overhead valve caput in well-nigh an 60 minutes. Arranging a campaign for the valve is, withal, more involved, especially if a forepart stop campaign is required to leave flywheel and clutch available for normal role. Valve diameter is some the same as the cylinder bore (iii") as this gives reasonable proportions of ports over a reach of useful timing diagrams as well as too gives a satismanufacturing plant residue of pressure areas to ensure valve seal without scuffing. The heads have primary ports nigh 1" ;" wide by 21" long in addition to 1" or more than deep depending on compression required. These ports are besides the combustion chambers. Compression ratios of upwards to 12 to i tin can be achieved with criterion apartment acme pistons. We power mention that the master set up of standard pistons are withal adept later on 12 months frequent racing, although the cylinders were late linered every bit the bores were tapered too ridged and were breaking rings. The spark plug is 10 mm. as well as because of space job in the original engine the points are i" downwardly, a five/xvi" diameter hole, but fire perfectly. Because of the shielding of plugs, plus cooling of the aluminium heads virtually of the racing has been alongside yard.L.yard. x L30 plugs which are quite "soft" for such an engine. Recently we accept used one thousand.L.1000. x L80. Plug problem is unknown. The latest engine used thousand.L.K. 10 L100 for racing at 7000-7500 r.p.1000. The inlet as well as exhaust ports are just about horizontal together with on opposite sides of the valve in addition to are near t" x ii,ane". The valve pockets connect these alongside the chief primal port or combustion bedroom according to the timing desired. The edges of the combustion chamber port as well as the edges of the valve ports command the exhaust opening and inlet closing points and the lower edges of the exhaust in addition to inlet ports control exhaust closing as well as inlet opening or the overlap timing. Valve timing can be adjusted inward particular by machining or filing port edges together with the timing can be moved bodily by way of slotted setscrew holes inwards the principal chain bike. Valve timing of introduce engine is just about: exhaust opens lxx degs. earlier bottom d.c., closes 30 degs. subsequently elevation d.c.; inlet opens twenty degs. earlier meridian too closes sixty degs. afterward bottom. This is non necessarily ideal every bit this is nearly how the original shapeings cleaned upward and no changes, apart from bodily varying timing (which is not really critical) accept yet been made. The motor (132.5 cubic inches standard Holden bore and stroke) has developed 200 b.h.p. at 7500 r.p,k. The rotary valve will, of form, not reach greater torque at whatever given capacity and compression ratio than poppet valves at moderate speeds. It does, even so, enable higher compression ratios to be used with ordinary petrol too this raises torque and efficiency. It likewise tin be made to hand breathing capacity adequate for whatsoever desired speed such equally 7000 r.p.thousand. as well as to x,000 up to even xv,000 r.p.m. if the crankshaft, rods, bearings, pistons, etc., were designed for such speeds. I have a design on which I am working, of a 139 cubic inches engine weighing 225-250 lbs., which is much more compact than a Holden too which would function safely at 12,000 r.p.one thousand. with fifteen,000 r.p.one thousand. over-runs. This is 8 cylinders 111 ii banks with two rotary valves. The stroke is quite brusk too in that location-foie piston speeds are low, every bit are the inertia loads. In racing conditions, such an engine would (IrnsuperchargerVi develop 300-400 b.h.p. The pattern allows for a moderate modify of capacity between say ii,000 c.c. to 2,500 c.c. past varying stroke or bore. |
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