Merlin???

Yes, I`ll stick to aircraft engines I think!
I don`t think it would worry Peter Svensson, he is usually up for most things. Do you know him?

Pete

That’s a common swedish name and I know a few of them. Probably not the one you refer to, though.

Christer

Pete,
it would require a big trailer to haul that one around … :diablo: … !

Christer

Yes, I`ll stick to aircraft engines I think!
I don`t think it would worry Peter Svensson, he is usually up for most things. Do you know him?

Pete

Pete,
it would require a big trailer to haul that one around … :diablo: … !

Christer

MerlinPete,

I have a friend who has been working most of his life as an engineer on big freight ships and he has said that the engines are “two storeys (spelling?) high”. 15 m/s piston speed and 90 RPM gives a stroke of 5 m (five meters) and it seems to fit my friends description … 🙂 … !

Christer

Looking on the Wartsila web site, http://www.wartsila.com/,en,productsservices,productportfolio,product,,24079490412160704,no,8001.htm they quote the m/s figure for all their engines, and it seems to be around 8.5 m/s. The strokes are typically 2 to 2.5 metres. Still, for such a huge stroke it still makes a good comparison with any other engine and proves the point nicely!

Pete

MerlinPete,

… and I would guess that if you did the maths, a large marine engine, albeit a diesel, running at 90rpm would not be far away either.

I have a friend who has been working most of his life as an engineer on big freight ships and he has said that the engines are “two storeys (spelling?) high”. 15 m/s piston speed and 90 RPM gives a stroke of 5 m (five meters) and it seems to fit my friends description … 🙂 … !

Christer

That boat sounds & looks like the Barcardi Silver boat.
Here it is averaging 202 mph !!! over a kilometre on a river.
http://uk.youtube.com/watch?v=uBmJ2cuFTcE
It is powered by twin supercharged V8 Chevys, 1500 hp each (probably reving to about 6000rpm) & does not sound like supercharged V8s you would find at the drag strip , so sound is not everything.

Kin ell…………….:eek::eek:

And I agree that the OP question that it isn’t a Merlin, and also it’s a traditional bost as opposed to a hydraplane in which Merlins were usually fitted…plenty of piston powered hydraplane racing clips on that youtube link for a sound comparison.

Just too much fun….
http://uk.youtube.com/watch?v=3NjlnJ3EoSY&feature=related
But is it or isn,t it,sounds too revy to be a Merlin seeing they only go to 3 to 4 gran??:confused:.

That boat sounds & looks like the Barcardi Silver boat.
Here it is averaging 202 mph !!! over a kilometre on a river.
http://uk.youtube.com/watch?v=uBmJ2cuFTcE
It is powered by twin supercharged V8 Chevys, 1500 hp each (probably reving to about 6000rpm) & does not sound like supercharged V8s you would find at the drag strip , so sound is not everything.

Stuart
That`s right, but at least some of the 3600 rpm rated Merlins used in Air racing run with cropped propellers for that reason.

Christer.
People often ask me why the Merlin is “low-revving”, and piston speed is indeed the answer, in fact it should compare favourably to a modern car engine.
The benchmark for an average petrol engine is 3000 ft/min, which equates to 15.2 m/s, and happens to be what a Merlin acheives at 3000 rpm. The Griffon at its rated 2750 rpm is 15.4 m/s and I would guess that if you did the maths, a large marine engine, albeit a diesel, running at 90rpm would not be far away either.
Other examples taken from Wilkinsons aircraft engines book:
Sabre 14.8 m/s
Hercules 15.9 m/s
R-2800 13.7 m/s
R-1830 12.6 m/s
Gipsy Major 11 m/s (No surprise there!)
Jumo 207 Diesel 16 m/s or 3150 ft/min

Junkers also made various Jumo 213s rated at 3250 rpm, 17.9 m/s and a 213J rated at 3700 rpm, 20.4 m/s. Remember, this engine has the bore and stroke of a Griffon!

Finally, before I bore you lot any further, the Merlin and Griffon, and probably others, have a maximum terminal velocity dive rpm which is rated for a limited time and at full throttle only to prevent a vacuum load on the rods. In the case of some Merlins this is 3600 rpm.

Pete

For the engine itself, disregarding propeller efficiency and tip speed, piston speed is what limits RPM. The higher the piston speed the higher the G-loads on the crankshaft and bearings. Light weight design and limited stroke are requirements for high rpm. I don’t remember exactly but in an F1 engine, piston speed is 22-23 m/s.

For a Merlin, that piston speed and ~152 mm stroke (6.0″) result in ~4400 RPM.
For a Griffon, that piston speed and ~168 mm stroke (6.6″) result in ~4000 RPM.

Merlins, Griffons and “light weight” are never mentioned in the same sentence and I doubt those theoretical RPMs are achievable.

Christer

Is it not the case , that the Merlin, (and Griffon), are limited to around 3000 rpm, purely because beyond that engine speed, the propellor fails to deliver anymore thrust; hydraplane racers do use Griffons, and do blow them to pieces, and in theory, there is no reason why any engine can’t be made to run at high rpm, for a short while at any rate.

Plenty of Merlin noises on the internerd, here are few good ones to compare it with:
http://www.youtube.com/watch?v=9Vy7UgCwEkk

There are many others to link to from that page.

The Spitfire is a Griffon (I think!), you can tell by the characteristic irregular firing effect.

Pete

Plenty of Merlin noises on the internerd, here are few good ones to compare it with:
http://www.youtube.com/watch?v=9Vy7UgCwEkk

There are many others to link to from that page.

I will put money on that NOT being a Merlin, if a someone managed to get a Merlin to sound like that it would only last for a few seconds before you would be left with a carrier bag full of broken bits!!.

John.

They do sound like that at Reno…. but your description of what happens to them isn’t far off the mark on occasion.

Cheers,
Richard

This does sound right….
http://www.youtube.com/watch?v=Ub0hwAPiidM&NR=1

I will put money on that NOT being a Merlin, if a someone managed to get a Merlin to sound like that it would only last for a few seconds before you would be left with a carrier bag full of broken bits!!.

John.

whatever it is, it sounds deadly 😀