hybrid

[Chris B]

Grumpy - the following is just to put a bit of meat on the bones of this discussion...

Empirical physics tells us that where small pipes are concerned, flow rate is inversely proportional to pipe length. So, given a fixed delivery pressure head, if you double your fuel hose length but nothing else in the system changes, your fuel flow delivery rate through that pipe will reduce by 50%.

That's a big drop in flow - but then it gets worse.

If your fuel hose has an internal diameter of 6mm, its unobstructed x-section area will be about 28.27 sq. mm. However, if you then insert a 4mm restriction in that pipe (which I'm guessing is going to be the approximate I/D of your aluminium coupling tube) the effective x-section area of your fuel pipe will reduce to around 12.56 sq. mm. In other words, the internal coupling tube chops more than 50% off the pipe's original x-section area.

With the above in mind, if your original fuel flow rate was adequate but didn't have a healthy margin above that which the carburettor is demanding, it doesn't take much imagination to realise that the two modifications mentioned above are highly likely to cause fuel starvation.

I'll go away now!

C

[Grumpy]

Chris and Charles uk. None of your info and or advice is either beyond comprehension or not fully appreciated.
Makes me smile and recall how at the start of ww2 the famous spitfire with a gravity carburetor could not compete in acrobatics with the me109 which had some type of electrical pump .
Just spoke to someone the other day about that.
Suppose my problem is less important
Its 2a.40 am so I had better get back to my beauty sleep.

However i do totally understand how I have to and will revisit and change the fuel line with a clearer understanding of the problem .I will say that I did take care with the aluminium tube joiner, burring all edges and ensuring it was well rounded and I used these hose clips, less strength than the clamps , 2 on each side to hopefully seal the line without squashing it out of shape .
And it does not leak .
The length of the new fuel line , on this silver century, is determined now by the fact that the villiers fuel inlet is now facing the other way towards the front thus the fuel line has to wind past then back onto the carb.
One of my start ups did produce a good response and a quick entry to normal running.
Will be up fresh tomorrow to get this fuel quantified and if i have enough fuel line I'll get to and create a new line

Cannot and will not give up now.
Thank you.

[Chris B]

Yes, the ME109 was powered by a sophisticated, fuel injected, inverted V12. Made by Daimler Benz I think.

But the Merlin, as you say, used carburettors which were sensitive to G-forces - particularly the violent negative acceleration generated by performing an outside loop at high speed. Not really what you want in a combat situation. The problem was eventually solved by a lady engineer called Tilly Shilling, who designed a very precisely engineered orifice that was inserted into the Merlin's fuel flow.

Tilly Shilling was a highly regarded research engineer at the RAE Farnborough and one of my colleagues (another aeronautical engineer / mathematician, long since retired) worked there with her in the 1950s. I gather that Ms Shilling's solution to the fuel flow problem had a fancy name, but I've been reliably informed by my colleague that the Farnborough research team and test pilots nicknamed it "Miss Shilling's Orifice."

So you're in good company - other people have had to solve fuel delivery problems too!

Cheers,

Chris

[40TPI]

FWIW in this discussion I've worked out the fuel useage for my recent FPC Thames trip. I know the fuel used was 32.9 litres and the approximate distance 126.5 miles after taking into account various double backs towing rafted canoes and searching for moorings at dusk etc etc. I recorded cruising time between locks for the first couple of days and pretty much hit an average of 5mph spot on. Take it at 5mph for now and therefore I probably did an accumulated 25.5 hours of cruising. That implies an averge of 1.29 litres per hour, or 21.5ml /minute. And for amusement, 17.3mpg... which a lot of Landies can't match... And no it wasn't WOT.

[ For comparison BS's marketing data for a 40Plus ( Note, not an FPC) gives 0.96Litre /hr at 3/4 throttle but I've suspected that was very optimistic ]

So, in conclusion, if you can drip out around 25ml /minute into that yoghurt pot with the float bowl off you have more than enough to feed an FPC/EFPC and a 40Plus......

[Grumpy]

Test results.
30 july 2019 7.55am , overcast ,slightly wet , 12degrees, freezing winter , silver century block, Villiers carb , tank a tad over 1/2full, 10-1 mixture, top off tank , bowl removed, tap opened and shut after exactly 1 min. I wonder if Nasa goes this far to collect data?
136 mils,
Please tell me its enough
Have to now shower, yuk, and shoot off to an old friends funeral later this morning.
He did not ever have a seagull outboard so I wonder how he is to cross the river?

And great info about the spitfire.

[Charles uk]

That's more than enough for wide open throttle under load.

What's the throat diameter of your Villiers, measure with a 1/2 inch drill bit, it's either 7/16 or 1/2 inch.

Silver Century cylinders are normally fitted with a 15mm Amal twin jet or a 16mm Amal 416, what colour is your spark plug running with the Villiers?

How did your beauty sleep work?
Unfortunately I never found it very effective!

[40TPI]

You certainly look to have way more than enough flow rate through our usual 50/234V Villiers carb to produce a stoichiometric mixture sufficient, when correctly set up, to run any 40 Series 64cc power head. I’d also say the same if you were running it on an older 102cc Century head which also used the same carb.
What I’d missed was that you have a Villiers carb plus a locally produced adaptor plate on a later Silver century block where an AMAL is expected. My bad for missing that, although my 20 odd ml figure is still good for ball park comparisons.
I’d not place too much of a conclusion on how well it will/might be expected to run until I’d run it under a proper load on a transom and not in test tank. Having realisedit is smaller than stock AMAL carb I’d not expect it to ever run and produce as much output as a stock built Silver Century; even before any limitations introduced by an adaptor plate are taken into account. BS went straight to a larger carb when moving from Century to Silver Century for a reason.
I think tube blockages, tickling, choke time and filters are a red herring when you are hoping to get Silver Century performance out of a smaller than stock carb bolted on an adaptor plate. People on here trying to squeeze an extra few hundred revs out of a Silver Century are going in the opposite direction and resort to fitting bigger/later AMAL 416 carbs et al, or wickedly drilling out a few extra thou of inlet bore diameter and still hoping to make stoichiometric without re-jetting.
As a last point if it is making 6000RPM no load that might, as someone has also hinted, mean it is running lean, ie you’re getting the volume through but the needle jet is not providing enough fuel. Put a load on and it would die. That Villiers carb is fixed jet so after you run out of screw/clip adjustment you have nowhere to go. It might also prove interesting to get it to behave under power over the whole range in this set up.
Begs the question why you are taking on more work with a non-stock carb, unproven adaptor plate design rather than taking the easier route sourcing the stock AMAL? But it’s interesting!
Charles suggested I put up my fuel data for info but I don’t know if he’d also spotted the Villiers/Silver C combo. He’s certainly the chap with the technical knowledge and past experience of doing all sorts of non std engine adaptations…..

Ah I see he's posted while I was off typing.....

[Grumpy]

I am using a villiers on this silver century really because I had bits left over , some bits that appear v/g, and then I became enamoured with the s/cent head and my only complete carbies left being Villiers. Absolutely no chance of creating an amal carb from my bits.
Plus some years back I had got tucked up buying a bitsa with this interesting home made bronze adaptor for such a project.Its a snug fit for both the amal and Villiers .
Was tired of being a good looking hunk, everything at my beck and call and just liking the Villiers decided to give it a go thus taking me back into the realm of the common folk. My beauty sleeps are really efficient and productive although it will cost you for the inside info.

Not wanting , only as a joke, to produce high rpm figures but just to get it going efficiently and reliably. Very interested in whether the Villiers could also power up the silver century and if not I would still have a nice solid machine on par with my 1956 lls century {comes with a Villiers"}. Also something to do over the winter as I'm done and dusted buying seagulls having got 11 or 12 {cant remember} in the shed.All going but I'm going to redo all the points come spring as its proving to be as winner.

And if it were to break down while traversing the north west passage I could not blame anyone else and that finally would guide me towards maturity.

I will never buy another seagull, never, not even if I got offered a marston at a bargain basement price.

[Grumpy]

Charles uk, throat of Villiers 1/2in,
Been down and started the beast, usually now even from cold 1-2pulls and no more than 10 seconds to running without choke.
Seems to run great .
Have found some spare marine fuel line which I can use to make myself a single full length one to fit the Villiers.
Forgot to check colour of spark plug!!!!!!!!!!

will do next trip down when the sleet has eased up.
Feeling real positive about this, need to keep my eye on all info supplied but want also to check the rpms asap.

I'm coming to realise that although she sounds mighty info online indicates perhaps I will end up with a century performance.
Will be very happy to see a higher rpm than 4000 though.
grumpy

[Charles uk]

The spark plug colour will tell us how it's running (rich or weak).

Seagull changed to the larger, more expensive 46N carb for a reason, as 40TPI so rightly said, logic says that reason must have been, higher power output.

Change the fuel pipe if you want, but as the extended one is flowing four times the maximum flow required, I wouldn't worry your pretty little head about it.

[Grumpy]

Will keep trying. No harm in that,We all know that pushing the boundaries can sometimes prove worthwhile. If not its no sweat of my back and my pretty little head survives another day and Ive learnt more.
Reckon this topic is stone dead but I'll still put up the rpms reached even if just for my sake.
Cheers

[Grumpy]

Test done in tank today and with the seagull spitting fire and brimstone the tacho read 4700 to 5100 rpm.
Very excited until Nudge explained that that is due to turbulence in the tank and he suggested it probably was around the 3800 mark or thereabouts or close or within cooey. He had similar results previously.
It sure rocked and rolled.Had me thinking it could do a piston.
So there we have it.
The Villiers carb does not produce the full power out of the silver century although it still sounded very nice and something to keep and use if possible.
So Its staying as is maybe even with a provenance that it was a one off production and highly collectible .

[Chris B]

All's well that ends well!

Just one minor loose end remains. A few days ago you reckoned that the carburettor required extended tickling followed by about 30 seconds of choke during a cold start. That's what got me interested in this thread in the first place. But you didn't mention the tickling time again, and more recently you reported that the choke requirement has reduced to about 10 seconds. From what I can gather, that change apparently occurred spontaneously.

If so, then perhaps the mysterious change in behaviour might be due to the petroil mixture having started to separate in the fuel tank while your engine was sitting idle for a little while. In which case the oil (which has a higher SG than petrol) might have begun to slowly migrate to the bottom of the fuel tank, resulting in a fuel lean, oil rich and slightly more viscous mixture arriving at the float chamber.

Hence the original symptoms: longer choke and tickling times - and (I'm guessing here) possibly a bit more smoke than usual during start up? Or to be technical about it, more than the SSSO (which of course stands for Standard Seagull Smoke Output).

Handling the engine, plus engine vibration during running, will have remixed the oil and petrol in the tank, causing the original symptoms to reduce or disappear.

It's only a minor detail and probably doesn't matter now - but details can be interesting, and they sometimes contain devils!

Cheers,

Chris

[Grumpy]

Yes you are correct.
The tickling and choke problems disappeared together.
The gull now starts easily, first pull and does not smoke excessive and only needs minimal choke.
In the first few starting I did experience loud and heavy one off back firings which quickly stopped and none since.
Could be as you say about the fuel mixture and if so should show up after I leave it idle for a period of time.
Suppose this could indicate less than perfect behaviour for long life.
Just hope it does not reappear while crossing the manukau bar in a 5m chop.

[Chris B]

Ah - is that so? Well that would make sense.

Because the more I look at the emerging small details, the better the petrol / oil separation hypothesis fits - especially as the symptoms you originally mentioned seemed to magically vanish of their own accord after you'd run the engine for a bit.

If that's what the problem was then you'll easily be able to prevent it happening again.

In future, when you've finished running the engine, turn off the fuel at the tank tap and let the engine run itself to a stop, so that it uses up whatever it can drag out of the carburettor and fuel hose. Next time you want to use the engine, give it a good shake BEFORE you turn on the fuel tap.

I think you'll find that the above routine might prevent a recurrence of the weird symptoms you mentioned, plus hopefully a reduction in the pops and bangs that you've reported. I say "hopefully a reduction" in the pops and bangs because I don't know how your experimental Villiers carb and the rest of the engine are getting along together.

Good luck with it all.

Chris