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Discussion in 'Chevy' started by PIRATE, Nov 29, 2015.
what are the possibilitys of an ls3 being used with direct drive?
Pirate: for me one of the less educatued flyers what is Is3?????? and direct drive what a corvair , vw, subaru, ???
There are several threads concerning the LS series and SBC direct drive conversions.
I thought the LS 3 was a sailplane from the seventies
There isn't anything to prevent it mechanically.
Other automotive engines have been done that way. Its simply a matter of attention to details in how you make the mechanical connection. Gary
Spencers well known canard has a Ford with just a simple prop adapter. Personally I would want some type of housing with a bearing and shaft
to lessen bending moments on the crankshaft. It can be done fairly simply. A lot of Corvairs are using a direct bolt on "fifth bearing" which is a
small bolt on adapter with a housing around it. One thing to remember is that the LS engines have a thrust bearing that is in the center of the
crankshaft rather than at the back...so if you make an adapter you might want to include an additional thrust surface in it. It kind of depends on
how you design your drive setup. As mentioned earlier there are existing threads where a lot of information and opinion already exist on HBA.
Somehow or another people thought that if an auto engine could produce 400hp, then it needed to be capable of that when adapted to an airplane.
That thought of course meant that the engine had to be operated at a higher than usable rpm so a reduction drive was needed. Personally, I have
been pushing the idea that in most airplanes the higher horsepower isn't needed or even usuable. Operating at something like 3000/3200 rpms will
allow for excellent hp amounts and the propeller can be designed to still have good efficiency.
The first thing you need to consider is the actual airplane you want to use the engine in. In some cases there is enough room to move the engine rearward
or to extend the fuselage to offset the additional weight. The thing is, you have to be realistic as to whether the airplane of your dreams is capable
of using the heavier engine. I love LS engines. I have a brand new LS3 crate engine thats going in a pickup truck. I really want to use one in an airplane.
The problem is that I want STOL capabilities, and I had to finally face the fact that an LS engine was not going to produce what I want. A Rover or a Corvair
(maybe turboed) may give me a better option. Its 400+ lbs for a LS engine, about 300 for a Rover, and about 200-230 for a Corvair. When considering any
of these engines remember that its not just engine weight to compare. An aero engine may be lighter, but usually thats with a metal prop. Use a wood or
composite prop and you lessen the total weight and put less stress on the drive and engine.
I did extensive research on this subject, and prevailed on the wisdom & knowledge base of those who know about it. I set out to build a canard aircraft using the Ford V8 as in the aircraft above. Had a few conversations with the owner. He installed this some 20 years ago, and has 2000ish hours on it. His engine is 270hp and 337lbs dry. Makes this hp at 3500 rpm. Very fuel efficient at cruise speeds.
What made me change direction was packaging. Crank is in the bottom of the V8, so the thrust line of the propeller will be down there as well. I decided to use a Chev V6 & a prop drive that raises the thrust line about 5" (IIRC).
I also investigated LS engines, and talked to Dave at Waterthunder Airboats. Dave builds LS engines for airboat use exclusively, and knows what it takes to make them live in this application. Which is very similar to an application in aircraft. He advised me against direct driving a prop with an LS engine due to the thrust bearing arrangement...which in his (extensive) experience was not up to the task. He has since developed a thrust bearing arrangement with which to drive a prop directly and build a direct-drive (DD) airboat with an LS engine. It's performance was apparently pretty good, and surprised many of his critics. You can find the video on YouTube. Again, w/ DD V8 there may be packaging/thrust line issues.
LS3 with starter, alternator in ready-to-run form but w/o exhaust is almost exactly 400 lbs. Airboat prop drive adds another 70, but greatly boosts hp and alleviates packaging problems.
I've brought this up before, but it bears repeating here. An Australian glider club went to the trouble to get an automotive V8 engine derivative allowed on their Pawnee towplane. They saved enough money in fuel/maintenance/operating costs/towing performance over just a couple of years... to buy a brand new European training glider.
That was a few years ago, so I will guess that the automotive V8 developments have improved since then. If I remember the story right, the Aussies' engine wasn't even the lightest or latest V8 available.
These engines are set up to use less expensive fuel as well. It seems to me that the effort and cost required for a good aviation conversion (including whatever thrust bearings, redrives, and re-programming is appropriate) is well worthwhile. I would guess that the biggest factor will be whether your airframe is appropriate for this size/weight/power of an engine.
There are several/many truths about utilizing an auto conversion and its comparison to using a used aviation engine.
The basic idea is that someone without much common familiarity with engines would be better off to purchase a readymade and proven
performance aero engine with a reasonable amount of time left until TBO. They can probably purchase such an engine for $8000 or
less and may never fly it enough to reach that TBO.
I think thats a pretty logical choice if everything works out the way the builder/buyer expects.
The thing is that most everyone is looking for those good deals and have been for quite some
time. The laws of supply and demand have caused diminishing availability of those really good
used engines. Now many of the used engines either have questionable history or are high time
engines on their 2nd, 3rd, or even 4th go round.
If the buyer finds any questionable issues with the engine due to long inactive periods, missing
documentation, directives, or actual inspection findings,......then the cost perspective changes
immensely. A professional mechanics services may be needed along with expensive parts and
the original plan is shot to hell. Even if there are no initial problems, maintaining reliability will
need costly yearly inspections to insure continued reliability. It isn't unusual for the engine to need
parts replacement even though TBO hasn't been reached. When considering using a used aero
engine,the buyer should project out a reasonable cost for AP mechanic services for yearly inspections
and an expectation to have some major work performed during the time of ownership. Expect to
replace a couple of cylinders at a minimum and get an estimate to do so. Check what a complete
overhaul would cost.
In addition to the initial cost, pick a cost somewhere between a complete overhaul and replacing two
cylinders. Add that to the total cost for a yearly engine inspection (x number years) and then throw
in the cost of expected oil changes and expected fuel costs. I've probably forgotten a few things.
Anyway, when deciding to use a used aero engine, that scenario will probably get someone closer to a
real world cost for using an aero engine. To the builders out there who truly know nothing about engines,
the aero engine is probably the best way to go no matter what the cost.
To the bold people out there who are willing to accept a challenge, adapting an auto engine can prove to be
very rewarding....not just in capital outlay, but personal satisfaction to having accepted a challenge and
successfully completing the project. Expect not to have to pay anyone else to maintain your engine, but
also expect a big savings in operational costs when done. Although there will be some people who have
to continue to work thru problems, for the most part your initial investment should reflect most of your
total investment. Once you have a working conversion, YOU will not need any more really expensive outlay
of cash, no matter what problem might develop later. Most problems will require minimal expense and
operating costs should also be substantially lower.
The chances of successfully building an aero engine powered airplane are greater than for an auto engine
powered airplane because of the wide variety of engines used and the fact that each engine type..as well
as each individual conversion will require solving many problems unique to that builder/airplane. There are
more opportunities to make mistakes due to the wide variation of builder knowledge and experience.
Did not know about a V8 but I know a Blanton 3.8L Ford V6 conversion was done on a Pawnee in Australia for a glider club. Originally equipped w/ a 540 Lyc, the plane was losing cylinders at an alarming rate due to shock cooling (apparently it wasn't a myth in this case). Full throttle climb to drag the glider to altitude, then chop it and head for the deck to get the next one.
Apparently this Ford w/ the belt drive was a real champ. Way more reliable in this workhorse role than the Lyc it replaced. 230hp and almost no downtime. There was a write-up done and posted on this site someplace.
Water cooled would keep things far more constant with a thermostat!
That's pilot error of they are shock cooling the engine. Not knowing how to use the equipment is not a defense.
While you are technically correct, to operate an air cooled a/c engine on a glider tug without shock cooling it would require taking 3 or 4 (or 5, or 6...) times as long to get back on the ground as it does to get to altitude. The articles I've read about a down under glider tug operation using auto power talks about doing as many as *10 tows an hour*. See why the a/c engine was shock cooled? They'd be lucky to get 1 or 2 tows an hour & still avoid shock cooling. Just not economically feasible.
Some links I've found:
Newsletters | Gliding Club of Victoria (starts on pg 27)
http://www.ddsc.org.au/private/autotug/Replacement engine optionv2.pdf
I'd have to google it but there is one LS series that comes in FWD platforms that has a very compact layout that I could see being beneficial to a aircraft use.
I've also envisioned a gear reduction unit that bolts onto the bell housing that either was integral with the oil pan and used a wet bath of some kind or if you could re purpose the power steering pump to pump oil through a geared redrive............The later seems the more feasible of my daydreams but with 3d printing and casting techniques becoming easier on the hobby level it's not as far fetched as before.
LS4.. It was developed for use in front wheel drive vehicles. Its block design is shared with the Vortec engine of the same displacement, but is cast from aluminum. The crankshaft had to be shortened 13 mm to fit, and it was the first LS engine to get GM’s Active Fuel Management technology (Displacement on Demand). Not too much aftermarket development has been done with these engine as the platforms they were offered in never really were geared toward performance.
You could find it in:
2006-2009 Chevrolet Impala SS
2006-2007 Chevrolet Monte Carlo SS
2005-2008 Pontiac Grand Prix GXP
2008 Buick LaCrosse Super
The LS4 boils down to a slightly shorter engine than the rest of the LS series. the main problem is it's small (5.3) displacement with no effective avenue to punch it out much bigger. It would take a very specific set of circumstances to want to use this particular engine in an aircraft.
I'd love to put one in a Porsche 914, personally.
If you decide to run a redrive, the simple way is to tap into an oil gallery and run a line to the redrive and a gravity feed tube back to the oil pan.....but you have to choose a place where you won't
divert too much oil from the engine....or use a Corvette 2 stage oil pump and plum the extra line to the redrive. Best case is to just run direct drive. You don't need a redrive unless you need more
than appx 200-250 hp available at about 3000 rpms.
I agree on the hp required issue; it's pointless to put 400+ hp on a plane designed for 200. And I know direct drive's been done, but most of the ones I've heard about that have high time on them also have basically a short drive shaft & outboard bearings to protect the crank. (I suppose Gary Spencer's might be the exception.)
The issue with direct drive on non-aviation engines is that the output end main bearing isn't long enough to keep bending loads away from the 1st crank throw. Even the VW & Corvair guys are adding an outboard bearing, and they swing really short, light weight props. Once you add enough structure & a crank extension for an outboard bearing, you're not that far away from the weight of a reduction drive which can provide bending load isolation and torsional tuning in addition to reduction. And with bolt-&-go airboat drives going for <$2500, it's difficult to develop a one-off direct drive outboard bearing setup for less $time$ and money. And if you want STOL performance, swinging a big prop at lower rpm is another big advantage.
I think I can do a direct drive extension system that incorporates 100% of the propeller loads AND provides an oiling system for a CS prop for less than 25#. It's a chunk of weight, yes, but a far cry from a PSRU.
I agree with you on the need for an extension shaft and bearing to isolate prop from the crank. LS has thrust bearing in center of crank rather than at the back like Spencers Ford or smallblock Chevy.
Direct drive with a bearing should weigh maybe 1/2 of a reduction drive built to handle over 200 hp. 25 maybe 30 lbs. while the old Geschwender chain drives were about 80 lbs.
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