Author Topic: F4U/190 supercharger question (Read 1012 times)

Seeker · « **Reply #15 on:** February 21, 2002, 10:21:28 AM »

I wonder why Fw used a "geared" supercharger when the 109 had the variable speed compressor, which seems at first glance to me more suitable.

fats · « **Reply #16 on:** February 21, 2002, 02:03:29 PM »

hah strato buffs... Ta 152 at 47K. yawn.

funkedup · « **Reply #17 on:** February 22, 2002, 02:10:49 PM »

Seeker, the blower speed on the DB engines was controlled by clutch slip. By definition this was an inefficient mechanism.

HoHun · « **Reply #18 on:** February 22, 2002, 02:29:37 PM »

Hi Funked,

>Seeker, the blower speed on the DB engines was controlled by clutch slip. By definition this was an inefficient mechanism.

On the other hand, fixed gearing required the throttle to be closed somewhat below full pressure altitude, which is inefficient, too.

Like everything in aviation, it was a compromise: Fixed gearing provided higher peak power, but fell off quickly if you left design altitude. Hydraulical clutches gave lower peak power, but maintained a high power output over a broader altitude band.

Regards,

Henning (HoHun)

funkedup · « **Reply #19 on:** February 22, 2002, 02:53:22 PM »

Of course Hohun. But mechanical engineers like robust and efficient mechanisms like gears more than clutches. Especially P&W engineers. And the BMW engineers learned to design radials by license production and reverse-engineering of P&W designs.

Vermillion · « **Reply #20 on:** February 22, 2002, 03:18:27 PM »

Wilbus, I would have to do alot more checking around to be sure, but check out this chart, from the Ta152 book I've been referencing lately. Specifically look at the entries for the Ta152-H0, with the Jumo 213E. (note that this is not a C model, its the first run of the H models)

According to that chart, this aircrafts top speed at altitude with WEP(the number in parenthesis) is 742 km/hr at 10.7 km , which according to my calculations is exactly 461 mph at 35,105 ft.

If you also look at the WEP Sea Level speed of the H0 on the same chart you can compare the 580km/hr or 360 mph, to the HTC chart and see that it also closely matches.

Just some additional information, if you go back and look at the evidence, it appears that only 3 of the total 48 production aircraft were H1 models with the 470+ mph you reference, and the other 45 aircraft were H0 models which lacked MW50 and GM1 due to production difficulties. There was an excellent thread on this subject about a year ago, where NathBDP and myself discuss this issue in depth.

Just a quick guess on my part

http://www.vermin.net/fw190/translated-fwchart.jpg

Wilbus · « **Reply #21 on:** February 23, 2002, 06:56:29 AM »

Check out the charts in your TA152 book Verm, the ones with curves. There are no for the H0 and H1 models there, there are only for the C models (shorter wings basicly) with different kind of engines, C with Jumo 213 has the same speed as our TA152 in AH. The TA152 C with DB engies seems to to be a beast at the deck but those engines hardly existed.

Will have to read up some more, but still think it's the wrong engine.

Vermillion · « **Reply #22 on:** February 23, 2002, 09:29:57 AM »

Wilbus, Your right the performance curves your talking about do not have the H0 on those charts. But if you look at the table (which I provided a link) you will see the numbers for the H0 which matches the AH performance right on.

Wilbus · « **Reply #23 on:** February 23, 2002, 09:37:43 AM »

But AH has got H-1.

Allso, the H1 had slightly longer wings then the H-0 + GM1 and MW50 boost wich gave it better high alt performance (GM1 specially). Think the Boosts might be a bit undermodelled and my guess is the our TA152 has got the Jumo 213 E engine and not the Jumo 213 E1 Engine as the TA152 H-1 had.

mrsid2 · « **Reply #24 on:** February 23, 2002, 09:45:01 AM »

Actually AH planes don't have any engines, just a bunch of code trying to simulate them. Sometimes this 'has' thing makes me smile a bit.

HT changes a couple numbers in the code and the 'Juno' engine starts to have a performance like a UFO.. lol.

HoHun · « **Reply #25 on:** February 23, 2002, 01:25:56 PM »

Hi Funked,

>But mechanical engineers like robust and efficient mechanisms like gears more than clutches.

Are you aware we're talking about a hydraulical clutch here? A hydraulical clutch resembles a turbine operated by hydraulic oil much more than the automotive slip clutch you seem to be thinking off. I don't see any reason to consider a hydraulical clutch anything else but robust and efficient. It's not like they were only used by German manufacturers - Allison and Wright are two US manufacturers who employed hydraulic clutches in their aviation engines, too. And if you talk about efficiency, remember that closing the throttle to avoid overboosting from a fixed-gear supercharger results in a decreased volumetric efficiency of the engine as well. Like everything in aviation, fixed-gear superchargers were a compromise.

Regards,

Henning (HoHun)

funkedup · « **Reply #26 on:** February 23, 2002, 03:16:26 PM »

Yeah I assumed it was a friction type clutch. Even with a fluid coupling, the mechanism is not as efficient as a gear train. I'm referring to the efficiency of the mechanism, not of the entire engine/supercharger system. Shaft power output divided by Shaft power input.

Wilbus · « **Reply #27 on:** February 23, 2002, 03:29:24 PM »

Uhmm, Mrsid... that wasn't very clever. You know very well what I and others mean by it, AH doens't have any airplanes in the case either, right? To discuss like that is just plain silly. AH Has got planes, with modelled engines, weapons, armor etc.