Any ‘Twitchers’ Out There?

Hope you don’t mind me adding these pictures to your ‘frogspawn’ thread.

This bird-of-prey killed and ate a (whole) collared-dove in my garden the other day.

Poor pictures I know but I didn’t want to scare it off.

So what is it? Anybody know?

Not sure how much protection it would have afforded…

…it would keep the rain off I suppose but a 7.62mm would go straight through it.

Still, against IED and 9mm pretty cost-effective…and as has been said all part of aviation history.

Well done.

I agree with you on the master/slave rods, however the compression ratio , whilst being set as you say is a component of the mean indicated pressure in the combustion chamber. That is altered by increased pressure in the manifold. That is why “blown” engines (be it turbo or super) have a lower compression ration than a normally aspirated one.

We’ll have to disagree on that one.

Compression pressure is variable. It changes with all sorts of factors as you mention

Compression ratio is fixed and is defined as I’ve stated. The reason ‘blown’ engines have lower compression ratios is that compression pressures are limited by detonation and the lower compression ratio is used to offset detonation.

It raises an interesting question; the designers of the DB605 must have designed in the different compression ratios, that is it couldn’t have been an accident.

As has been suggested the reason may be something to do with the position of the supercharger.

Different pressures may have existed at the inlets to the different banks effectively leading to a loss of performance in one bank. Raising the compression ratio of that bank may have been the easiest way to restore that lost performance or at least mitigate it.

There is one that was a true single-row six but I can’t remember which one.

1928 Potez 6-cylinder single-row radial?

How about the B-36. Six p & w R-4360 with 28 cylinders, 56 spark plugs and 56 manually adjustable valves per engine and it had six, that is 336 spark plugs!

Surely that has to be a record…unless anybody knows different.

At the other end of the scale I can think of an aircraft (built in the thousands) that had only one spark plug…

…any guesses?

Cut the whole fitting out of an old rad and attach it to a plate which will bolt down onto the old outlet, will run an overflow pipe to a resivior.

I am also going to add one to the tank to stop it collapsing as it cools.

A second radiator cap?

I think you’d be better off with just one (on the manifold). With two radiator caps, one will always ‘lift’ first and ‘sods law’ says it wouldn’t be the one on the manifold where the air will tend to collect.

As long as your chosen cap will allow air/coolant to be sucked back into the system as the engine cools there should be no danger of the drum being crushed.

A simple air bleed valve will allow you to make sure that the drum is full of coolant before each ‘sortie’. I’ve used a bicycle tyre type valve (with metal housing) in the past.

I presume that the information that the plate contains should identify what aircraft these engines were fitted to.

I’m not sure you’ll ever discover what type of aircraft these data plates were from; there just doesn’t seem to be enough unique information on either one.

As you probably know the Hercules XI was a two-speed single-stage supercharged radial.

The ‘M’ and ‘S’ in the first column of data refers to the speed of the supercharger (which was gear driven) with ‘M’ being the low-gear and ‘S’ being the high-gear.

The supercharger speeds (gear-ratios) for the similar Hercules VI were 6.68:1 for ‘M’ gear and 8.36:1 for ‘S’ gear.

The other columns are self explanatory, RPM, Boost Pressure, Cylinder Head Temperature and Oil Temperature.

The difference in data between the two plates is basically that one engine is rated to run at higher cruising RPM with higher boost pressure and that engine therefore produces more power (but has higher cylinder head and oil temperatures).

The easiest way to explain this is that this is essentially an identical engine running on petrol with a higher octane rating.

How many of each type used these engines would be an interesting point.

As for the numbers of aircraft using the Hercules XI:

Stirling I (series II) – 117
Stirling I (series III) – 307
Albemarle I –
Albemarle II – 100
Albemarle V – 50
Albemarle VI – 250
Beaufighter I – 120
Wellington III – 1517

Just these quick totals above require 5770 engines…and I know I’ve missed some.

If I put a plate over the old outlet and weld a car header tank fitting and cap onto it I could use the carb manifold as the header tank?

That looks as good a point as any without significantly altering the manifold.

The manifold will not really act like a header tank in this case as it should be filled with coolant (without an air pocket at the top) when the engine is running.

However it looks like a good point to purge air (and excess coolant) from the system (via a car radiator type cap) as the engine warms up and to draw coolant back in as the engine cools.

Do you know the total coolant capacity?

If that oil drum is full of coolant you should have something like 60 to 65 gallons in the system…and no air…which means something like 3 gallons will have to escape due to expansion (depending how hot the engine gets).

You will need an un-pressurised reservoir to catch this (connected to the ‘radiator’ cap by a hose) so that it can be sucked back in as the engine cools.

I would say it was important to have a cap that allows coolant (or at least air) to be drawn in as your 55 gallon drum could be crushed as the engine cools.

I would also put an air-bleed valve at the highest point of the drum as air will almost certainly collect there during engine runs.