Quote from: kerick on October 10, 2024, 07:51:49 PMThey're so much lighter than the piston engine so they have to be forward to maintain balance.

Now that makes a lot of sense - I was wondering why IRL they didn't shorten things. Thanks. 

Ultra BearCat is looking good. 

The very first turboprop was shorter, the RR Trent, but it had a centrifugal compressor, from the Welland, which was much shorter than the later axial  flow compressors.

By the time they got serious about turboprops later on axial flow compressors were the thing and they're longer as their multiple stages just take up space. Attempts to make them shorter by reversing the air flow inside the engine weren't really successful, the Bristol Proteus being a classic case as it took AGES to get it to work properly.

For reference, THIS happens when you put a lightweight turborprop into an inline engine's place... 

...and as a side note: a potential real-world powerplant for a turboprop Bearcat could be the General Electric T31, the first turboprop engine designed and built in the United States and used/tested in the XP-81 and XF2R. Quite compact, but would probably not have offered a significant improvement in performance. Still an attractive option, IMHO.

Quote from: Dizzyfugu on October 11, 2024, 03:00:08 AMFor reference, THIS happens when you put a lightweight turborprop into an inline engine's place... 

I have a kit of one of those, but it's difficult to know how to Whiff an aeroplane that's ALREADY a Whiff.   

Quote from: kerick on October 10, 2024, 07:51:49 PMI'm not sure that vise is strong enough to hold all that power!
I wouldn't worry about the length of the nose. Turboprops always end up sticking much farther forward than the piston engine they replace. They're so much lighter than the piston engine so they have to be forward to maintain balance.

My main concern with nose length is pilot visibility for carrrier landings at this point, but I expect it won't be too much worse than the Corsair.

Quote from: Dizzyfugu on October 11, 2024, 03:05:53 AM...and as a side note: a potential real-world powerplant for a turboprop Bearcat could be the General Electric T31, the first turboprop engine designed and built in the United States and used/tested in the XP-81 and XF2R. Quite compact, but would probably not have offered a significant improvement in performance. Still an attractive option, IMHO.

Well the whole reason for doing this is to get more power, I need more!  More than an R-3350, more even than a Wasp Major!   
The T40 is the most powerful turboprop of the era, at least that I'm aware of.  The Double Mamba doesn't even come close!

The Python comes close, (4100 bhp + 1800 lbs thrust) and was a LOT more reliable..................

Quote from: PR19_Kit on October 11, 2024, 06:24:16 AMThe Python comes close, (4100 bhp + 1800 lbs thrust) and was a LOT more reliable..................

The reliability I will give it, but the Allison T40 delivers a thousand extra hp.  If development had continued with it I suspect the problems could have been mostly ironed out.  Jet engines of the period largely had issues too.

Saw this recently and thought it looked appropriate for the Turbo Bearcat, so I think I'm going to do a '50s style grey scheme on it.

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Quote from: Spino on October 11, 2024, 07:04:28 AMThe reliability I will give it, but the Allison T40 delivers a thousand extra hp.  If development had continued with it I suspect the problems could have been mostly ironed out.  Jet engines of the period largely had issues too.

But they didn't have gearboxes, which were the prime problem with the T-40s used on the Tradewinds.

Almost everything can be fixed by development, you just need DEEP pockets! And the final result often bears little resemblance to the original article.

I speak as a development engineer for some years...................

Quote from: kerick on October 10, 2024, 07:51:49 PMI'm not sure that vise is strong enough to hold all that power!
I wouldn't worry about the length of the nose. Turboprops always end up sticking much farther forward than the piston engine they replace. They're so much lighter than the piston engine so they have to be forward to maintain balance.

Well the T40 (minus its gearbox) is actually about 200lb heavier than the R-2800, a bit concerning but I think it'll be okay.  It's a heck of a lot lighter than a Wasp Major and produces about a thousand more horsepower.

Quote from: Spino on October 11, 2024, 08:14:20 AMSaw this recently and thought it looked appropriate for the Turbo Bearcat, so I think I'm going to do a '50s style grey scheme on it.

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That will look cool. Or make the outer wings dark blue like the photo of a post war Corsair.

Quote from: PR19_Kit on October 11, 2024, 08:58:15 AM

Quote from: Spino on October 11, 2024, 07:04:28 AMThe reliability I will give it, but the Allison T40 delivers a thousand extra hp.  If development had continued with it I suspect the problems could have been mostly ironed out.  Jet engines of the period largely had issues too.

But they didn't have gearboxes, which were the prime problem with the T-40s used on the Tradewinds.

Almost everything can be fixed by development, you just need DEEP pockets! And the final result often bears little resemblance to the original article.

I speak as a development engineer for some years...................

This is true.

Trying to decide on the armament for this monstrosity, maybe a couple of Sidewinders and a drop tank or two.  And of course the four 20mm cannons.  As much as I'd like to give it a torpedo like a Wyvern, I think that's pushing it considering that the Bearcat has limited range, and this is supposed to be super fast and fast climbing to intercept bombers anyway.

The minimum length of the T40 power section only, the two T38s, is 84+ inches, the overall length
varies by dash number which is determined by the installation, i.e. the power section of the T40-A-1
used in the XF-84H is 86", the overall length, including propeller gearbox is 339.26", it's the only one
that didn't have the contra-prop drive attached to the front of the combiner gearbox. The T40-A-6
of the North American XA2J Super Savage, and the single pre-production example of the A2D-1 had a
power section length of 84" and an OAL of 167".
Note that while the OAL includes the power section plus the driveshafts and combiner gearbox it
does not include the length of the exhaust pipes.

Also a note about weight, the power section only of the T40-A-6 is 2,500lbs, the driveshafts, combiner
gearbox and contra-prop drive add several hundred pounds more to the total. The notion that changing
from a piston aircraft engine to a turboprop automatically means you have to move the engine fwd for
CG reasons isn't always true, it's completely dependent on engine type.

The firewall of the F8F Bearcat is not located in line with the aft end of the cooling gills of the cowling,
it is at Station 100 and is in line with the leading face of the main wing spar.
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The T40 version used in the Convair XFY-1 Pogo probably had the shortest overall length,
but it still wasn't what one would call short and took up half the length of the fuselage,
which was very similar in length to that of the F8F.
Shortening the driveshafts to bring the gearbox closer to the engine faces is problematic
because you still need room for air intake. Reduce the distance by too great an amount
and it will introduce flow problems.

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