gruntguru wrote:The interesting bits in the D-B article are:
1. The low boost pressures tolerated by the DB601. The power-up raised the boost from 4.25 psi to 6.0 psi. Apparently piston "weakness" was the limiting factor. Cylinder filling would have improved more than the 9% attributable to the boost increase due to the "hot cam" and "port & polish" mods that were also part of the power-up.
2. The massive increase in valve overlap from 42* to 105*. Probably to increase scavenging as much as anything. Increased scavenging would cool the combustion chamber (including the "weak" pistons). Direct injection of course permits unlimited scavenging without loss of fuel.
Suggest it was for commercial reasons.J.A.W. wrote:For the Jumo 213, the Germans used increased rpm (to TBO threatening piston speeds) as a means of power-boost.
& @ T-C, re: the sorry saga of the Rotodyne..
..This was another (sadly typical) British example of snatching defeat from the jaws of victory..
..by political, rather than technological reasons..
The Napier Eland was killed by R-R - after their take-over, & again - due to non-technological reasons..
http://www.flightglobal.com/pdfarchive/ ... 00336.html
The production Vulture used a different system to the ealier pivoted type. It was in two pieces with 4 clamping screws. The faces of the master rod and cap were serrated, so no movement between them should have been necessary.Tommy Cookers wrote:btw Wright found that big-end fretting could be prevented by silver plating the mating faces of the rods as required they told all US manufacturers maybe this would have saved the Vulture ?
Don't think Vulture's troubles were related to harmonics.J.A.W. wrote:Vulture conrod problems were more substantial than a bearing material issue, likely an X-configuration harmonic thing,
- & no X mills were successful in any useful military/commercial way..
No, I do not know what they did for the Pennine. Though it was capable of 2800hp @ 3500rpm early in development.J.A.W. wrote:R-R (& others) were keen on X-configuration mills but none ever really made the cut..
A radial is a 'different kettle of fish', & 4-stroke radials such as the R-2800 run odd-numbered sets/banks of cylinders.
W, do you know how the R-R Pennine big-end/con-rod arrangements differed from the Vulture?
Curious that R-R seemed to admit defeat & went to a twin crankshaft scheme for their last 24cyl..