PIRATE
New Member
what are the possibilitys of an ls3 being used with direct drive?
There isn't anything to prevent it mechanically.what are the possibilitys of an ls3 being used with direct drive?
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.... 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.
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.
Reply: In this particular case I think there are two main points of consideration.
The first point is that an auto engine was successfully adapted, and now the benefits of that change are being recognized
by the tow service. I'm not sure if that could be done legally in the USA because of restrictive laws on modifying certified
airplanes and using conversion or homebuilts for profit. Apparently the results have been very satisfactory to the people
who operate the tow service. It also points out another fallacy about auto engines being designed to loaf along rather than
be put in a high stress situation continuously. References are often made about the high power needed for takeoff, and yet
here is an engine not only operating at high power to takeoff, but dragging the additional load of another airplane. You can't
ask for a situation that demonstrates the ability and reliability of a conversion any more than repetitive tow operation.
The second point is that not only has it proven reliable, but cost to operate has also proven to be much less expensive.
I've ranted on some other threads about things that I feel are deficiencies in the design of aero engines that should be
addressed by the manufacturers. Some others are of the opinion that those deficiencies are an acceptable part of the
design and can easily be overcome by "correct" operation of the engine and increased piloting skills thru training. They
of course are correct for the most part. If you apply carb heat correctly you won't get carb ice. If you take the time to
slowly cool your aero engine you won't get shock cooling problems.
The problem is that pilots always seem to err in judgement and then have to deal with the results of that error financially
and sometimes physically. On the other hand, the water cooled engines usually don't have to deal with any of those issues.
It just seems logical to me that an engine that virtually can't develop a certain problem is better than one that can...even if the
problem can be handled by proper operation and experience.
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.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.
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'tI'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.
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.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.
Charlie