Paxton-McCulloch Supercharger History - Part IV
Paxton / McCulloch Supercharger History – Part IV
The Granatellis and The McCulloch DO-VS59
During 1957 Anthony, Vincent and Joseph Granatelli moved down from Chicago to Los Angeles, after selling their successful speed shop Grancor Automotive Specialists. The Granatelli brothers had extensive experience with McCulloch superchargers after modifying several for racing and installing hundreds at Grancor, and they joined up with John Thompson, the chief engineer at Paxton, to try and resolve some of the problems that the VS57 suffered from. Their collaboration, and confidence in the results, resulted in them purchasing Paxton Products from the McCulloch Motor Company in 1958 and resulted in developing the DO-VS59.
The VS57 was suffering from quality control problems during manufacture, and was becoming increasingly expected to perform at and above its design speeds due to larger capacity higher revving V8s coming onto the market, as well as the demanding requirements of racers. The quality control problems were mainly due to the steel balls in the planetary drive, which have to be matched to a fine tolerance to prevent imbalanced loading and subsequent wear during operation. These were being supplied to the factory in matched tolerances but were being mixed in hoppers during the manufacturing. The internal oil pump was also flawed in its oil pickup design, and was providing insufficient lubrication for the planetary drive. It had an inadequate capacity for high speed lubrication and it’s heavy plunger floated at high rpm’s, starving the balls and races when they needed lubrication the most. Failures as a result of these was giving the McCulloch a bad name and resulted in large numbers of warranty claims due to premature failure, and possibly contributed to the discontinued use of McCulloch superchargers by Studebaker. Some of these faults were corrected on the VS57, but more modification was required to allow the units to run at higher input speeds.
The research by the Granatelli/Thompson collaboration found that the planetary drive steel balls were also a significant contributory factor in the speed limitations of the VS57. Friction of the planetary drive balls on the races generates heat during the normal operation of the supercharger, with this heat being absorbed by the lubricating fluid. As the input shaft speed increased above the design limit of 5200 rpm the centrifugal force on the balls, and the extra impeller load caused the balls to slip on their inner race, generating excess heat with subsequent overheating of the lubricating fluid and galling of both the race and balls. The use of a wider contact path between the balls and their race was proven to lessen the slippage, allowing a higher rpm operation, but a wider contact path also results in more heat being generated.
The use of the engine’s high pressure oil supply to lubricate and control the VR57 superchargers had resulted in the VR57 superchargers running significantly cooler than the VS57 units. The Granatellis and John Thompson, as a result of earlier research into engine oiling, made the decision to use direct engine oiling on the VS57 to allow the unit to run cooler and to completely remove the problems associated with ensuring adequate lubrication of the balls and races. The resultant extra heat capacity facilitated an increase in the contact patch of the planetary balls on their races, and allowed the use of a stronger spring loaded pressure plate which kept the bearing races against the balls, thus reducing slippage. The resulting unit was the McCulloch DO-VS59 (‘DO’ stood for Direct Oil), which was introduced in 1958. The casing that was used on the VS57 was modified slightly for the DO-VS59 to allow the use of direct oiling. The dipstick opening now served as the inlet for the oil feed from the engine that was fed straight to the hollow input shaft, and consequently straight onto the units planetary drive. An outlet was added at the base of the supercharger to allow the oil to return back to the engine, relying on gravity to feed. The internal oil pump was replaced with a stainless hose, which carried the pressurized oil direct from the former dipstick housing to a modified ball driver shaft, which delivered the oil to the planetary drive and the other lubricated components.
The DO-VS59 (which was always marketed as a McCulloch and not a Paxton-McCulloch) was only volume produced for about a year and was offered with a 100% guarantee for the first 90 days or 4,000 miles, and a 50% guarantee for the next 270 days or 12,000 miles total. Andy Granatelli’s confidence in the product was such that he completely dropped the VS57 unit, and in a bid to stimulate DO-VS59 sales killed all VS57 support (with the exception of service parts) and pushed the DO-VS59 as a part exchange unit rather than rebuilding VS57 units. The DO-VS59 was poorly tested however, and consequently not a great success as owners either failed to change the engine oil at the required intervals, or added substances to the oil (such as STP) which were not compatible with the bearings and seals used in the units. Reliability was further compromised by the fact that acids generated as a result of the build up of blow by gases would corrode the ball drives and races, particularly if the supercharger units were left standing for more than a couple of weeks.
The SN Series
The McCulloch DO-VS59 superchargers were manufactured and retailed right through to 1962 (and possibly later) alongside the SN (Short Nose) series superchargers that Paxton introduced in 1959. Further research at Paxton resulted in the introduction of a more efficient fixed ratio supercharger, which used the planetary drive arrangement of the McCulloch VS superchargers and was marketed as the Paxton SN60. This supercharger lacked the variable speed of its predecessors, which was proving to be a liability due to belt slippage at the higher engine rpm it was expected to be driven at for the newer higher revving engines. The removal of the variable ratio drive resulted in the supercharger being 2.2 inches shorter than its predecessor, hence the term ‘Short Nose’.
Paxton also returned once again to the use of an internal oil reservoir eliminating the corrosion and lubrication cleanliness problems that had plagued the DO-VS59 units, and to a lesser extent the VR57/58 units. Technology improvements to bearings, seals and lubrication gave them greater power handling capabilities and reliability than the earlier McCulloch units. Significantly a redesigned oil pump which had an increased capacity, and which didn’t suffer from float at high rpm, allowed the SN60 blowers to be turned at higher rpm’s than their predecessors without risk of oil starvation to the drive bearings.
A big difference between the SN60 and the VS57 is the output shaft. An SN60 output shaft doesn't “pilot” in the end of the input shaft the way it does in the VS57. There's a change, to limit the oil flow out of the end of the input shaft, which goes with it. Another small difference is the size of the fitting in the volute, for boost reference to the fuel pump. It is 3/16 inch on VS, and 1/4 inch on SN.
When comparing part numbers, oil pumps and all their parts are the same between the SN60 and the VS57. All the ball drive parts, except for the output shaft itself, are also the same.
Incidentally, the Paxton part numbers for the drive balls and races, shown on Studebaker blueprints for the Avanti, are the old McCulloch part numbers for American made parts; not the better quality German made pieces. Of course, it's possible that Studebaker and Paxton upgraded parts and but didn't bother to change the part numbers.
As well as producing the superchargers Andy Granatelli also raced SN60s using Chryslers, Plymouths and Chevrolet Corvairs with single and dual blower set-ups during 1960 and 1961 and set numerous speed records. A switch to Studebaker in 1962, along with more successes resulted in Studebaker purchasing Paxton Products, and employing the Granatelli brothers with Andy Granatelli eventually becoming president of Studebaker’s STP division, and Vince and Joe Granatelli remaining with Paxton. The feedback from racing with the superchargers resulted in the SN62 being produced, and the Studebaker ownership of Paxton in conjunction with the fact that Studebaker’s president was former McCulloch Vice President Sherwood Egbert, resulted in the extremely fast SN supercharged Avanti’s being produced.
The VR58 was still offered by Paxton as a replacement unit through to the mid sixties, and was also offered through to 1970 in a modified form as a racing supercharger. This variant (the VR4) had the variable ratio planetary drive fixed in the high ratio through the use of an adaptor and an aluminum stud replaced the oil control valve. By replacing the drive pulley with a larger or smaller diameter unit, the boost output could be increased or decreased (as is the case with all VR units) to best suite the application. This supercharger retailed for about $250 and was intended for drag racing use only.
After splitting with Studebaker, Paxton dropped out of the supercharger business in 1974 (probably due to emission legislation effectively killing off the performance market, albeit temporarily), concentrating instead on centrifugal blowers for industrial and marine applications. Ironically the VR supercharger survived this and was reworked as a blower for moving air through the cabins of submarines. These units had oil reservoirs mounted on the bottom, and were completely reworked as single speed blowers, producing a high volume of air at a low pressure of about 3 psi.
Modern Day Paxton
Public demand persuaded Paxton to re-introduce the SN60 in 1979, and since then Paxton has modified and upgraded the SN60 through various variants (SN89, SN92, SN93, etc.,) to its current SN2000 guise. To all intents and purposes these ball drive units are basically the same superchargers as the earlier VS57 units, and consequently many parts from these later units are interchangeable with the earlier units. Paxton also introduced an advanced gear driven Novi supercharger in the late 90’s and no doubt the Novi name was used in tribute to the early 1950’s gear driven superchargers developed by Paxton for racing at Indianapolis.
Whilst the Granatelli brothers remained with Paxton Products, even during the mid 70s when superchargers were not a major product line, the company commendably maintained product support for all its superchargers, including the McCulloch VS57 (apart from that hiccup when they introduced the DO-VS59 in 1958) and to a lesser extent the VR57. This included all spare parts, rebuild kits, and product literature. In 1998 the Granatelli brothers split Paxton Products, selling off the supercharger and fuel systems divisions, and retaining the industrial blower division. The new owners, of the now named Paxton Automotive, junked most of the VS57 spare parts and units and only supported the newer SN units. This support was short lived and as part of a drive to concentrate on the more profitable supercharger sales, all rebuilds were outsourced to Craig Conley of Paradise Wheels in California. Further restructuring resulted in the merger of Paxton Automotive and Vortech in April 2001, and in June 2001 Paxton discontinued all SN series manufacture and support, focusing completely on the Novi gear driven units. In order to save the ball drive supercharger line Craig Conley purchased all of the manufacturing rights, spare parts, jigs, moulds, etc… for the SN and earlier units, and has continued to provide SN support.
As for Robert Paxton McCulloch, after the sale of Paxton Products in 1958 he expanded into outboard engines and in order to test his engines purchased land adjacent to Lake Havasu in Arizona and built up Lake Havasu City. In 1962 he famously (or infamously, as the mad American who thought he was buying Tower Bridge) bought London Bridge for $2.5 million dollars and shipped it back to Lake Havasu, where it was rebuilt across a part of the lake. The bridge rebuild was completed in 1971, and Bob McCulloch continued the development of Lake Havasu City until he passed away on February 25, 1977.
