Re. Great planes. With all due respect Mark, and I mean that sincerely, their has been the same man at the heart of Great Planes from the beginning and one of the owners and still directing the engine department and most other aspects of GP. By the way look at all the changes Corvair has gone through and the break-aways if you know what I mean. Not a lot of companies keep the same owners and CEO. Just my .02 On Jun 21, 2016 7:14 PM, "Mark Langford via KRnet" <krnet at list.krnet.org> wrote:
> Some random thoughts that I feel must be said: > > Turbocharging a VW would be a recipe for disaster IMHO, and insurance that > you wouldn't do much flying. Don't forget...it's all about flying, not how > fast you can say your plane would go if it were running. > > GPASC has proprietary parts...flywheel, adapter, hub, crank, bearing, and > case come to mind quickly. Having built one of these several times, I'm > not a fan of the keyway setup. The slots are in hub and crank are shallow, > and the key is provided as a square key that you need to grind (or mill) > down to something way thinner to fit between hub and crank. Getting a good > fit with maximum material is trial and error. The key is only there to > ensure the timing mark stays constant if the hub is removed. The taper is > where the power is transferred. > > Crank and hub are also matched sets due to tolerances on the angle. The > hub still needs to be lapped onto the crank, which is a two-hour chore by > hand. > > The hub/bearing clearance is not consistent. The crank and bearing are > sold as a set, and getting a new bearing for an existing crank is iffy. > I've torqued the case to 8 ft-lbs and the crank still spun, then when I > torqued it to 14 the crank seized. No amount of refitting cured that one. > I'm not a great fan of the prop bolt...1/2" RH threads. Revmaster's is > .75" LH threads, which can be torqued higher for a better connection. > Otherwise, a simple engine backfire can unscrew the prop, despite proper > torque and Loctite 620 on the bolt threads. > > If the crankshaft's oil seal leaks, the hub isn't going to come off > without a 20 ton press, so tear the engine down to replace the seals, and > hope the next seals work better. My luck with those seals has not been > good either. That's the only place my engine has lost oil. > > If you're working with the hub before it's torqued and remove it while the > keyway is facing down, the tiny key falls down into the cavity below the > cam gear, and you get to tear the engine down again to retrieve it. Yes, > I'm stupid, but it could happen to you as well. > > Buy the GPASC manual and read it. There's a lot of trial and error work > to be done in there, not to mention the basics of case and other > clearancing when boring and stroking a VW engine. I guess the 2700cc > Corvair really spoiled me...no machine work or trial and error. > > Generally, VW heads have a tiny area of air passages between the top and > bottom of the head, even after serious deflashing. This has gotten even > worse over the years, rather than better, now that factory VW heads have > dried up. Corvairs have way more cooling passage area, hence they cool far > better. N56ML would fly around on the hottest of days at cruise speed and > it might be 320F. This VW is closer to 380F. The "cure" for this is to > move the CHT probes to the head studs, so the temperature will read a lot > lower. Makes you feel better, at least. Fiberglass plenums are my next > experiment, and probably a set of heads with larger cooling air passages, > if I can find them. > > Keep in mind that I used to be a VW mechanic, and am no stranger to trial > and error with details like chamber volume, but this is ridiculous, and > apparently never ending. > > GPASC is on its third owner in less than a year, so consistency is not > something I'd count on. > > I could write more, and someday I'll have time for further details, but I > feel obligated to get this said. For the moment I'm off to adjust the > valves again. > > Stirewalt's right, I "make" time by not getting enough sleep, and it's not > getting any better... > > > Mark Langford > ML at N56ML.com > http://www.n56ml.com > > > > > > _______________________________________________ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options >
