- Oct 18, 2003
- Saline Michigan
I think that there are many parallels between homebuilt aircraft and homebuilt cars, especially wrt kit planes and kit cars, which, in both categories account for the vast majority of completed machines.One of the reasons of the existence of the homebuilt aircraft is because there is no much people with money to buy a brand new GA and operate with the costs of GA, we don't see a lot of people building cars in their garages because car is cheap.
Viking's rubber torsion damper is easily inspected in a very few minutes and replaced if needed. Multiple videos of owners / operators commenting on how smooth the engine is at all RPM settings idle / takeoff / cruise.My observations about these auto converted option until now are:
1- I think Jan solved the issues with torsional vibration, I think Aeromomentum too, there is no cases of broken crankshaft that I know.
It make sense, the friction grows a lot with the speed, there is an old relation between rpm and lifespan where low rpm=high lifespan that justifies the long lifespan of the locomotive engines and ships, but they also have a good liquid cooled system that keeps the temperature constant, I think the low RPM is another point for the lyconentals, but themselves are going to way of liquid cooled auto conversions with their new diesel engine series. Including Porsche all the automotive brands no longer are using air cooled engines. That's why I think aircraft engines seem stuck in the past, that's works, but the 6 cylinders of Porsche 911 air cooled also worked very well, but it's no longer available.Frictional losses at high rpm generally hurts the BSFC of geared auto conversions but if you're burning Mogas and the engine is a lot cheaper to buy, I don't think this is a big concern. You need to look at initial costs and operating costs to work out a cost per flight hour.
This is the first estimate, providers usually don't show prices on the internet, to find out the actual prices I would need to make some phone calls, not yet. I'm going to seriously think about the next year or 2 years ahead, for now I'm deciding which direction to take.You're probably over-estimating the cost of the cylinders and a couple of other items (check other suppliers), but vastly underestimating some other costs and not accounting for many thousand$ in other needed items to build a complete, working engine. For instance, the magneto gears (not included with the mags) are hundreds of dollars each. You'd need connecting rods, of course. Nuts & bolts could easily run over a thousand $ (rod bolts are big buck, single use items). And you're without doubt rolling the dice on an ebay crank and/or crankcase. I'd be shocked if you were lucky enough to build a reliable Lyc from collected parts for less than a mid-time 'runner' from someone you trust. Actually building one is relatively straightforward (it's basically a big VW Bug engine), except for all the little 'bite you in the butt' items you need to know that will only come from working with someone who's done it, or *very* careful research & following the overhaul manual (and all updates) to the letter.
The Lyc 360 & Cont. 470 live in different universes, purely in terms of weight. Airframe choice pretty much dictates picking one or the other.
Yes, is almost 130 lb of difference, in this point the auto conversions and O-360 are almost similar.I'd stick with a timed out or half time Lyc 360. Lots of support and clone parts out there. The 470 is really old and a bit of a boat anchor. The 470 has more power but is a lot heavier.
Tim, I'm doing my own project, is a 4 seats low wing all metal airplane, I have worked in this concept last 10 years and I started the build this year, I have the background of 20 years working in automotive industries how design engineer and worked for different car brands in a lot of projects, then I decided to take this adventure using the knowledge that I got in CAD/CAE for my own airplane. Someone can say I'm crazy, but the raptor designer was a TI guy and his airplane flew (not as well as predicted, but...), maybe I being an mechanical engineer I can humbly got a good result.
I think Rotax did it very well. The 9xx series are high RPM engines with no complains about reliability and very fuel efficient, light weight, but low power (max 150hp) and equal expensive. But they are the proof that PRSU can also work very well.Reliability of the PRSU's is my largest concern, they are the weak point in the conversion. I predict one day though, someone will engineer a PRSU that will either use a torque converter or some other means to lower engine RPM in cruise, lowering operating costs even further. (Just a personal thought).