Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
...
However, did the fundamental design limit development of the integral supercharger - did the design limit or prevent a multi-speed supercharger and/or an integral 2-stage supercharger?
.Ironically, the RR Merlin, perhaps not designed with the mass production philosophy and modularity of the V-1710, turned out to have much greater supercharger development potential, with multi-speed and multi-stage versions being developed
Was the V-1710 basic supercharger design flawed in this regard?
[/QUOTE]From Wikipedia:
....
This approach allowed easy changes of the supercharger(s) and supercharger drive-gear ratio. That gave different critical altitude (the maximum altitude at which the engine could produce full power) ratings ranging from 8,000 to 26,000 feet (2,400 to 7,900 m).
Thanks guys, great replies!
I wasn't thinking so much about the history and attributes, but the mechanical engineering aspect of making the V-1710 supercharger multi-speed or 2-stage.
It seems that either this was much more difficult or impossible to do on the V-1710 than with the RR Merlin, or Allison did not have sufficient resources to do the job.
Is that why it took so long for 9.6:1 supercharger V-1710s to enter production? I've been wondering about that, but considered it was related to other issues like charge heating issues with earlier variations of the supercharger or simply lack of demand/interest.There may have been a physical aspect. The original rear accessories gear case was too narrow to fit the thicker gear needed to handle the desired 9.60 gear ratio. if the desired air flow was 10,000lbs per minute the 8.80 gear needed about 210hp while the 9.60 gear needed 250hp to drive it. If there wasn't room for a thicker gear was there room for a two speed drive mechanism?
I wonder if sending such proposals to individual aircraft manufactuers might have been another option for securing funding ... or at least swaing the Army for its need. Then again, I'm not sure how that sort of action would mesh with military bureaucracy at the time, or if it could have caused friction between Allison and the Army.With the modular design it was certainly possible to develop a 2-stage or even more stages of supercharging, and Allison offered this option to their primary customer, the US Army Air Corps on at least 2 or 3 occasions and was told no thanks each time. Allison ws a relatively small company and when your major customer does not want to fund a development, it doesn't get funded by anybody ... and it didn't.
...
As it was, the 9.6:1 ratio engines were only slightly weaker at altitude than the likes of the Merlin 45 or 20 series (or V-1650-1) and even that discrepancy was probably due mostly to the excellent Hooker-based supercharger designs rather than inadequecies on Allison's part. (ie a larger supercharger might not have helped much ... just a universally more /efficient/ one -ie better boost with less charge heating for given power consumption)
Not sure if going higher than 9.6:1 would have hit other mechanical limits ... again, but charge heating involved would have certainly limited max boost. (depending on fuel type and possibilities of ADI/water injection -I assume a water injection system would have been much simpler and less costly to engineer than a 2-stage supercharger configuration ... then again, WI would have been a godsend to early model P-38s with intercooler issues yet nothing was forthcoming there ... )
I wonder if sending such proposals to individual aircraft manufactuers might have been another option for securing funding ... or at least swaing the Army for its need. Then again, I'm not sure how that sort of action would mesh with military bureaucracy at the time, or if it could have caused friction between Allison and the Army.
Were Pratt and Whitney's 2-stage supercharger developments funded in-house or NAVY supported? I seem to recall the auxiliary superchargers used on the R-1830 and R-2800 were somewhat similar in configruation to the sort eventually employed on the V-1710 (hydraulically clutched and running independently from the integral single-speed supercharger stage, including lacking any sort of intercooling -until late model R-2800s- though water injection was offered fairly early on for the 2-stage 2800s).
Aside from that, the V-1710 itself had some nice advantages over the Merlin in terms of production cost/volume, maintanence, and ability to run lean at significantly lower RPM (and specific fuel consumption). Especially for that latter reason. (the latter advantage alone might have been enough to make even the intercooler-less 2-stage Allison's more attractive on the likes of the P-51 than the Merlin 60 series ... had they been in volume production by early 1943, and available for testing some 6 months prior to that)
Is that why it took so long for 9.6:1 supercharger V-1710s to enter production? I've been wondering about that, but considered it was related to other issues like charge heating issues with earlier variations of the supercharger or simply lack of demand/interest.
Not sure if going higher than 9.6:1 would have hit other mechanical limits ... again, but charge heating involved would have certainly limited max boost. (depending on fuel type and possibilities of ADI/water injection -I assume a water injection system would have been much simpler and less costly to engineer than a 2-stage supercharger configuration ... then again, WI would have been a godsend to early model P-38s with intercooler issues yet nothing was forthcoming there ... )
I wonder if sending such proposals to individual aircraft manufactuers might have been another option for securing funding ... or at least swaing the Army for its need. Then again, I'm not sure how that sort of action would mesh with military bureaucracy at the time, or if it could have caused friction between Allison and the Army.
Were Pratt and Whitney's 2-stage supercharger developments funded in-house or NAVY supported? I seem to recall the auxiliary superchargers used on the R-1830 and R-2800 were somewhat similar in configruation to the sort eventually employed on the V-1710 (hydraulically clutched and running independently from the integral single-speed supercharger stage, including lacking any sort of intercooling -until late model R-2800s- though water injection was offered fairly early on for the 2-stage 2800s).
The 2-stage R-1830s were in production around the time of the Battle of Brittain even ... though the altitude range those engines manage weren't really spectacular compared to single-stage engines tuned well for high-alt. (I think some 2-speed R-1820s even came close ... and German designs certainly did well with mostly single-stage superchargers; still, I suppose the point here is P&W's design philosophy could have fit very well with Allison's ... P&W just got the engineering funding much much earlier)Good thing for the Wildcat too given the F4F was a dog without that engine.