Talk:Republic XP-72

message: I see that this wiki page carries the same general wording as the William Green source: " . . the 28-cylinder Wasp Major, the turbo-supercharger for which was placed aft of the cockpit, being geared to an extension shaft extending backward from the engine . ."
As I understand it, the P-47 fuselage was so large because of the decision to locate its turbocharger aft of the pilot, which meant a large duct (carrying HOT exhaust gas from the engine to the turbine of the turbocharger), and another large duct (carrying compressed air from the supercharger to the intercoolers).  It appears the same rationale was used on the P-72; its fuselage is larger than needed merely to fair with the engine diameter, and its three-view clearly shows a ventral exhaust dumpgate ahead of the tailwheel, similar to that of the P-47.  So, the question: why drive a turbo-supercharger with both hot exhaust gas and a mechanical shaft?  That doesn't make sense, but since Green included it in his P-72 entry, he must have had a reason.  Does anybody know??? Raymondwinn (talk) 19:05, 13 January 2008 (UTC)
thread_title: Shaft-driven turbo-supercharger?

message: In 2001 I published a book on the Wright Tornado aircraft engine that included a section on the Republic XP-69, one of the aircraft that was intended to use the engine. Please see
http://www.weakforcepress.com/
At that time my book contained the most complete information that had been published on the XP-69. In 2001 available sources all agreed that the XP-69 was a mid-engine fighter with the propeller driven via an extension shaft.
I have since discovered a drawing of the XP-69 at the U.S. National Archives that clearly shows a conventional tractor engine installation. This is the only drawing of Republic design AP-18 that I have ever seen. Please see
http://www.weakforcepress.com/tornado_errata.htm
 
I apologize for the poor quality; the drawing was too large to duplicate with any of the equipment available at NARA, so I was forced to hang drawing and photograph it in sections.
The drawings clearly show the engine in front of the pilot and the space behind the pilot filled with the ducts, radiators, intercoolers, etc. required for a liquid-cooled turbosupercharged engine installation.
The unfortunate thing is that I discovered this drawing AFTER I had published my book on the Wright Tornado. In retrospect, I DID have details of the ducting and heat exchangers behind the pilot and should have realized while writing the book that there was no room for the engine behind the pilot.
The Republic AP-18 design is thought to be an evolution of the AP-12 design, which DID have a mid-mounted engine. It appears historians may have incorrectly assumed the AP-18 was a mid-engine aircraft also.
May I respectfully suggest a change correcting information related to XP-69 engine configuration?Kmccutcheon (talk) 20:14, 5 August 2011 (UTC)
replies: text: There is a photo of the XP-69 mock-up on page 155 of US Experimental & Prototype Aircraft Projects by Bill Norton. The aft fuselage is huge, with several vents not found on the front-mounted P-47, et al. As such, it's best to present both views, without preference to either one. Anyway, it's probably best to create a separate article for the XP-69, and deal with the issue there. - BilCat (talk) 21:05, 5 August 2011 (UTC)
replies: text:  If you view the complete XP-69 (AP-18) drawing set at
http://www.weakforcepress.com/XP-69/index.html
I believe you will see that the aft fuselage, huge as it is, to be filled with turbosupercharger, radiators and ductwork.Kmccutcheon (talk) 15:50, 6 August 2011 (UTC)
replies: text: I can see that. I do realize that the R-2160 block is compact compared to the R-4360, with nearly half the displacement, and does fit quite neatly in the nose of the XP-69. However, do we know for certain that this is the only version of the design? Without all of the ductwork, would there not be room for the engine and the supercharger? Perhaps there was an intermediate design that previous published sources are reporting. It does sound like a good subject for a future book, or at least part of one! :) Until that happens, though, it's still OR, and WP relies on what is published in reliable sources. - BilCat (talk) 16:55, 6 August 2011 (UTC)
thread_title:  XP-69 Engine Behind Pilot with Extension Shaft???