SU Oddity?

[Bob Culver]

In have read that SUs were unsuitable on speedboats as the violent vertical shocks confused the pistons.

[Alan]

That’s why proper boats have sails, Bob.

[dickie65]

Hi Alan,
Thats a blow for for us !!!
They should have bowsprits and topsails too and leak like a seive.
I remember sitting on the head getting wet every time the bow dipped in the swell.
( 1896 boat painted black you could see out through the planks )

For everyone else
Back to the Su bject,
I used to use a D2 on the Type 65 it always missfired on hard cornering but only one way.
Right hand corners especially roundabouts.
The factory had problems which were cured with twin float chambers.
Float level is also critical, I have tried to make sure the float chamber is forward so that the mixture enriches going up hill and leans off going down.
Fuel surge, float jamming or piston jamming can cause problems.
A go pro type camera looking at the piston / butterfly could give a bit more usefull information.
I am back to using a semi downdraft but have not given it the hard cornering trial since the change.

https://www.med-engineering.co.uk/h4-su-...extensions ( Looks like the answer to a Maidens Prayer )

Time to play with the lathe again.


Its been a bit damp down in The We tcountry !!
I have 6500 Rpm available.

I have used downdraft Zeniths and had a high speed missfire which cleared as soon as I slowed down a bit this was caused by Carb Icing.
Even with the Nippy Hotspot.

[Zetomagneto]

Can’t see how the Medway extensions work, raising the fuel level will surely cause over rich mixture and poor running

[dickie65]

I wonder if the Medway kit lowers the bowl to compensate. or whether to extra airspace above the float helps.

[Colin Reed]

HI ALL,
DURING THE WAR Beatrice Shilling who was an Engineer developed a solution  for the su fitted to the Merlin engine in Spitfires,
During dives and rolls By fitting a small disc with a small orifice in the fuel intake just before the carb this enabled enough fuel normal running but if the float moved quickly opening the needle it restricted the flow and cut out flooding

Colin
NZ

[Tony Press]

Commonly referred to as Miss Shillings Orifice or Tilly's Orifice  (ooh! matron   ) 

[Steve kay]

Evidently still side effects from Cupid's arrows fired off at lusty humans on St Valentines Day. Wouldn't want to be at sea on a sailing vessel today, so a three cylinder compound would be preferable. Nor sure that any of us Seven sailors have experience beyond reciprocating machinery, thuogh our worthy historians may come up with a turbine powered Austin, if Solihull can manage it then surely Longbridge can.

[Paul N-M]

Became known as 'Mrs Shilling's orifice' thereafter I have heard related!!!!!!

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Ah, just noticed you got there before me Tony!

[Bob Culver]

Hi Alan

I agree. When my son was a sea scout I often went out in the sailing cutters. It was great fun and I was often bemused by the one or two wealthy occupants of fast power boats thudding past and wondered what they got out of it.
I am not sure if the now state of my back is due lifting Seven and Javelin engines or rowing energetically for nautical miles in the cutters.
(many of the youngsters adopted the view that, like walking to school, rowing was obsolete, and would make only token effort)