Author Topic: It's official... (Read 8056 times)

Guppy35 · « **Reply #180 on:** December 19, 2005, 03:59:29 PM »

Quote

Originally posted by gripen
There is some differences between the RR Merlin 66 and Packard Merlin 266, shortly:

Reduction gear:
66 0,477
266 0,479

1st SC gear:
66 5,79
266 5,80

2nd SC gear:
66 7,06
266 7,35

1st FTH rating +18lbs:
66 1705hp 5750ft
266 1710hp 6400ft

2nd FTH rating +18lbs:
66 1580hp 16000ft
266 1490hp 19400ft

Generally the 266 is very similar with the V-1650-7.

gripen

Point being that they came off the production line together and got their mark number based on the engine. Put a 266 in a current Spit IX and technically it's a Spit XVI. Both under the Supermarine Type 361 designator Spit VIII being Supermarine Type 359

Crumpp · « **Reply #181 on:** December 19, 2005, 04:13:39 PM »

Quote

W3248 was a very early production Spitfire FVb.

We will see when the report gets here. If the aircraft is over 600lbs light then I think it will make some good general conclusions. Without the report though we are all just guessing.

All the best,

Crumpp

gripen · « **Reply #182 on:** December 19, 2005, 04:18:24 PM »

Yep, I just wanted to point out that the 266 is more like a medium altitude engine. The XVI should have some 3-4k higher 2nd FTH than the LFIX and therefore also max speeds should be a bit higher.

gripen

Crumpp · « **Reply #183 on:** December 19, 2005, 04:26:04 PM »

Quote

3-4k higher 2nd FTH than the LFIX and therefore also max speeds should be a bit higher.

Wow, Do engines gain more power below or above FTH?? You should probably check that logic as it completely wrong.

All the best,

Crumpp

gripen · « **Reply #184 on:** December 19, 2005, 04:28:59 PM »

Quote

Originally posted by Crumpp
Wow, Do engines gain more power below or above FTH?? You should probably check that logic as it completely wrong.

Please explain what is wrong with the logic.

gripen

Crumpp · « **Reply #185 on:** December 19, 2005, 04:42:40 PM »

Look at these engine graphs:

Perhaps you can start another thread if you do not see it. I am sure there are plenty on this board who will take the time to explain it to you.

All the best,

Crumpp

Karnak · « **Reply #186 on:** December 19, 2005, 04:52:20 PM »

That is rather dismissive and insulting Crump, particularly given that he is right and you are wrong.

If you were right the Spitfire Mk XII would be faster than the Spitfire Mk XIV because the Griffon IV has a lower full throttle height than the Griffon 65, yet we know that this is not remotely true.

The higher that a full throttle height is the faster that aircraft will be, all other things being equal, because the engine with a higher full throttle height is producing that power where the air is thinner and therefor the aircraft can reach higher true airspeeds.

As such the Merlin 266 with a full throttle height of 19,400ft would make for a faster Spitfire than a Merlin 66, with its full throttle height of 16,000ft, Spitfire. That is only in terms of absolute top speed at fastest altitude. At 16,000ft the Merlin 66 Spitfire would obviously be faster.

gripen · « **Reply #187 on:** December 19, 2005, 04:57:13 PM »

Generally max speed will increase if the FTH is raised with higher SC gearing despite the shaft output is lower.

As an example:

Mustang III with V-1650-7 1505hp at 2nd FTH 24500ft 442mph
Mustang III with V-1650-3 1330hp at 2nd FTH 28000ft 450mph

Infact the same phenomena can be seen from about any performance graph showing two different SC speeds, including the Fw 190 graphs.

gripen

Crumpp · « **Reply #188 on:** December 19, 2005, 04:57:27 PM »

Quote

That is rather dismissive and insulting Crump, particularly given that he is right and you are wrong.

He is not correct. Engines loose power after FTH.

Once more at the edge of the drag wall it takes considerable power to make small gains. The difference in those two motors would have to be much greater to have a signifcant impact.

Gripen gets exactly what he dishes out. There are some people on this board I value there opinion and there are others who I don't always see eye to eye with but know their stuff. Gripen falls into neither catagory.

Please search the BBS Karnak before passing judgement.

All the best,

Crumpp

Kurfürst · « **Reply #189 on:** December 19, 2005, 04:59:15 PM »

Quote

Originally posted by gripen
There is some differences between the RR Merlin 66 and Packard Merlin 266, shortly:

Reduction gear:
66 0,477
266 0,479

1st SC gear:
66 5,79
266 5,80

2nd SC gear:
66 7,06
266 7,35

1st FTH rating +18lbs:
66 1705hp 5750ft
266 1710hp 6400ft

2nd FTH rating +18lbs:
66 1580hp 16000ft
266 1490hp 19400ft

Generally the 266 is very similar with the V-1650-7.

gripen

Tales from GripenWorld.

Nope, you are completely wrong. The Merlin 66 and 266 had exactly the same rating.

Same specs as the Merlin 66.

There goes the theory going to the trashcan. And frankly, it's awfully boring to witness that you are willing to make up any sort of nonsense always bearing the mark of same side bias. And never ever backing them up.

Guppy and Crumpp is right, the XVI is just a late production LFIX with detail improvements and pretty much the same engine. Almost the same as the G-6/G-14 thing.

gripen · « **Reply #190 on:** December 19, 2005, 05:07:47 PM »

I'm quoting directly the RR listing of ratings from the appendix of "The Merlin in Perspective" by Alec Harvey-Bailey.

gripen

Karnak · « **Reply #191 on:** December 19, 2005, 05:09:41 PM »

Quote

Originally posted by Crumpp
Engines loose power after FTH.

Agreed.

But that doesn't change the fact that an engine with a higher critical altude will make an aircraft faster than the same engine, but with a lower critical altitude.

Heck, even a less powerful engine like the Merlin 61 produces a faster aircraft due to the higher critical altitude. The Merlin 66 is losing power above 16,000ft whereas the Merlin 61 is losing power above 27,000ft. Is it any wonder then that the Spitfire F.Mk IX does 408mph and the Spitfire LF.Mk VIII does 402mph despite the Spitfire LF.Mk VIII being less draggy and having the more powerful engine?

Any ways, all kind of moot given that Kurfurst just posted data that confirms what I understood to be the case originally. That the Merlin 266 is a Merlin 66 built in the USA and with American tooling.

Crumpp · « **Reply #192 on:** December 19, 2005, 05:09:50 PM »

Quote

Mustang III with V-1650-7 1505hp at 2nd FTH 24500ft 442mph

Over how many flight test's? 8mph difference??

If you take the average speeds might increase over a small portion of the envelope. For example the FW-190A9 is faster only because it's has a greater output over a higher FTH. It also has a greater output, Gripen.

Raising the FTH alone does nothing for the top speed.

Looking at the Merlin specifically, if that were the case then the LF would not be the "low altitude" version.

Quote

Tales from GripenWorld.

Just like the FTH statements.

Karnak, you are one of those whose opinion I do value. I understand what you are saying but I do not think just raising the FTH alone is the reason for the gains. Unless it is a significant FTH gain to a much higher altitude and thinner air.

All the best,

Crumpp

gripen · « **Reply #193 on:** December 19, 2005, 05:14:02 PM »

Crumpp,
Why don't you just compare speeds at 1st and 2nd FTH in the graph you posted.

gripen

Crumpp · « **Reply #194 on:** December 19, 2005, 05:14:42 PM »

Quote

ny ways, all kind of moot given that Kurfurst just posted data that confirms what I understood to be the case originally. That the Merlin 266 is a Merlin 66 built in the USA and with American tooling.

Yep the engine discussion can move to a new thread.

All the best,

Crumpp