Brodhead Pietenpol Association

Original Posted By: "D.J.H."
Subject: Pietenpol-List: Notes on Piet+Corvair+PSRU (long)>For the few of you that are interested in this subject, I've learned a bitmore>over the past couple of weeks. Just thought I'd pass it along. I recentlyhad>a phone conversation with Bob Sheffield, who appeared in the mailbag of the>BPAN #60 with the announcement that he had completed building up a Corvair>engine with a PSRU. In fact, he and a friend of his had each assembledCorvair>mills with their own version of the Rinker Drive. He had strong opinions.>First of all, he confirmed that the VW reduction gear that is used in the>Rinker Drive must be from a Type 2 VW (transporter, kombi, single cab,etc.)>from between 1964 and 1967. Not sure why earlier or later models cannot be>used, but it could be because the '64-'67 have the thickest shafts (13/8").>Now, these aren't so hard to find. I've learned that everyone who has aType 2>from this era wants to get rid of their transaxles for some unrelatedreason,>and the guys that build dune buggies collect these for installation intheir>baja bugs. They seem to be a pretty good source. The problem is thatthere>were 3 different gear ratios built during this period, and the rarest isthe>one most suited for our purpose. It's known as the Mountainous Terraingear>ratio, 19 teeth on the drive gear and 27 on the driven gear, for areduction of>1.42 to 1. However, the most common reduction box has a ratio of 1.39 to1.>>Bob Sheffield assembled his unit with the 1.39 : 1 gear, and he's veryhappy>with the engine performance, although he has not yet flown. Says it startson>the first pull every time. He's turning a 72" prop, but doesn't yet knowthe>pitch. Other characteristics of his engine which diverge from thePietenpol>conversion are:>1. He removed the fan, alternator, and harmonic balancer (running andimpulse>mag).>2. high capacity oil pump.>3. 140 hp motor>4. Cast aluminum oil pan>5. get this...a carburetor from an old outboard motor (from a boat) on a>four-legged intake manifold above the engine.>6. Did not adjust engine mount; he figures the 3 inches gives him moreprop>clearance.>>In case you're not convinced that this guy really wants to stretch thelimits>of the Pietenpol classification, he's building this as a Chad Williebiplane.>He says he'll send me some photos, so I'll scan 'em when they arrive.>>I also received a response to questions that I posed to Jim vanDervort. He>built a Corvair/Pietenpol with a Rinker Drive many years ago. I don't knowhow>many hours he has on it, but the last 225 hours have been without the PSRU.He>said the disadvantages are the added weight (nearly 50 lbs) and added>vibration. Bob Sheffield and his friend avoided much of the weight bycasting>the gear housing from aluminum, instead of using the standard VW cast iron,and>their thrust bearing has eliminated vibration. Since Jim removed the PSRUfrom>his ship, his climb rate has decreased (take off distance went from 400 ftto>800 ft...he's a BIG guy), but top speed is about the same. He's says he's>still faster than nearly every other Piet he's flown with. Never heard of>anybody with problems related to thrust loads on the crankshaft.>>So, that's what I've learned so far. I still don't know if I'll continueto>pursue this PSRU idea. Sounds like advantages are just about equal to>disadvantages.>>--Peter>>________________________________________________________________________________

Original Posted By: Phil Peck
For the few of you that are interested in this subject, I've learned a bit moreover the past couple of weeks. Just thought I'd pass it along. I recently hada phone conversation with Bob Sheffield, who appeared in the mailbag of the BPAN #60 with the announcement that he had completed building up a Corvair engine with a PSRU. In fact, he and a friend of his had each assembled Corvairmills with their own version of the Rinker Drive. He had strong opinions. First of all, he confirmed that the VW reduction gear that is used in the Rinker Drive must be from a Type 2 VW (transporter, kombi, single cab, etc.) from between 1964 and 1967. Not sure why earlier or later models cannot be used, but it could be because the '64-'67 have the thickest shafts (1 3/8"). Now, these aren't so hard to find. I've learned that everyone who has a Type 2from this era wants to get rid of their transaxles for some unrelated reason, and the guys that build dune buggies collect these for installation in their baja bugs. They seem to be a pretty good source. The problem is that there were 3 different gear ratios built during this period, and the rarest is the one most suited for our purpose. It's known as the Mountainous Terrain gear ratio, 19 teeth on the drive gear and 27 on the driven gear, for a reduction of1.42 to 1. However, the most common reduction box has a ratio of 1.39 to 1.Bob Sheffield assembled his unit with the 1.39 : 1 gear, and he's very happy with the engine performance, although he has not yet flown. Says it starts onthe first pull every time. He's turning a 72" prop, but doesn't yet know the pitch. Other characteristics of his engine which diverge from the Pietenpol conversion are:1. He removed the fan, alternator, and harmonic balancer (running and impulsemag).2. high capacity oil pump.3. 140 hp motor4. Cast aluminum oil pan5. get this...a carburetor from an old outboard motor (from a boat) on a four-legged intake manifold above the engine.6. Did not adjust engine mount; he figures the 3 inches gives him more prop clearance.In case you're not convinced that this guy really wants to stretch the limits of the Pietenpol classification, he's building this as a Chad Willie biplane. He says he'll send me some photos, so I'll scan 'em when they arrive.I also received a response to questions that I posed to Jim vanDervort. He built a Corvair/Pietenpol with a Rinker Drive many years ago. I don't know howmany hours he has on it, but the last 225 hours have been without the PSRU. Hesaid the disadvantages are the added weight (nearly 50 lbs) and added vibration. Bob Sheffield and his friend avoided much of the weight by castingthe gear housing from aluminum, instead of using the standard VW cast iron, andtheir thrust bearing has eliminated vibration. Since Jim removed the PSRU fromhis ship, his climb rate has decreased (take off distance went from 400 ft to 800 ft...he's a BIG guy), but top speed is about the same. He's says he's still faster than nearly every other Piet he's flown with. Never heard of anybody with problems related to thrust loads on the crankshaft.So, that's what I've learned so far. I still don't know if I'll continue to pursue this PSRU idea. Sounds like advantages are just about equal to disadvantages.--Peter________________________________________________________________________________

Original Posted By: "D.J.H."
What does the PSRU mean I'm still new at this and have learned a lot justreading what many of youhave done through . thanks Terry________________________________________________________________________________

Original Posted By:> TLC62770(at)aol.com
Prop Speed Reduction Unit

Original Posted By: Gordon Brimhall
Propeller Speed Reduction UnitDon________________________________________________________________________________

Original Posted By: Peter P Frantz
Peter, I've heard over and over that of all the corvair engines the one notto use is the 140 HP due to the large valves dropping and causingcatestrophic failures. Let us know how yours works out.Dom. Bellissimo-----Original Message-----

Original Posted By:> Raffaele Bellissimo
The 140 hp and 110hp ENGINES have the same comp.ratios of 9:25to1. Perservice manual specs.Doug

Original Posted By: ADonJr(at)aol.com
> > What does the PSRU mean I'm still new at this and have learned a lot just> reading what many of youhave done through . thanks Terry________________________________________________________________________________

Original Posted By:> D.J.H.
> > Doug,> The 140 has lower compression. the 110 HP is 9.25. perhaps it's too greata> compression.> Dom.> -----Original Message-----