Discussion in 'The light stuff area' started by ryanjames170, Sep 29, 2018.
Anyone here messed with a 2A042 engine, and have HP numbers RPM?
Kevin said its making about 25 HP. He carves his own props. He also did some mods on the engine, all I can remember is raising the CR. He put a thousand hours on a Mini-Max with a 1/2 VW that was legal by about 2 lbs.
Mini-Max with a Hummelbird canopy.
Getting rid of excess weight is one of the tasks. Grinding of any excess barb is helpful and junking anything that does not need to fly. It was built military tough but military heavy for the size.
Yes, I was about t say you need to be asking about weight as well as hp.
IIRC in there army fourm they are around the 200lbs mark
I believe that would be the 4 cylinder 4A084, which comes out at about 120 pounds ready to fly. The OP asked about the 2 cylinder 2A042.
http://saturnsurplus.com/engine/5kweng.htm check it out 205lbs for the 2A042
Got one of the -042's that I'm looking at for a LePelican. Just don't have a mount, and have to be sure the motor is not too heavy to keep it from coming down on the nose!
That 250 pounds is the shipping weight, which includes the starter, air ducting and a create no doubt.
Percy in NW FL
if you get some time see if you can weigh it in its flying condition id be curious how much its weighs in at.. very little data that i can find on these engines..
And that includes all the parts that don't belong in an airplane!
You don't need the air shroud. Or the cooling fan. Or the governor. Or the alternator if you hand prop. And some guys even rip of the oil pan and replace it with a more sensible one.
Don't know about the 2A042 but there is a Yahoo group for the 4A084, but I haven't seen any activity on it for quite a while.
Also check around on the various airboat forums. The 4A084 is quite popular with them.
10 HP it says. I looked at this engine for powering my T-mono but the weight and HP just doesn't match up for my use.
I believe the hp is at 25,000 ft. Military derated. It's about 25 hp give or take. There were a couple at OSH in the swap meet tent. For the right price, I would play with one. Weight is as installed in original use; you have to wack it down if you want to use it.
25,000', 150F, 1 part fuel, 1 part camel urine. Air filter not been cleaned for 2,000 hours.
The stock rating is really, really pessimistic. It's a 42ci (690cc) engine. If you can't get 20+hp from it, you should stick to off the shelf stuff.
Those 032, 042, 084(20hp@10,000ft), All the other Gen Motors are also rated HP at 10,000ft. The Weak Points was the Rod Bolts, and they used a low CR. The most I ever heard getting out of an 084 was 60hp. Using a Higher Rpm, a Higher CR, a Special Ground Cam, and I think he even used some Bigger Valves. 84ci at 100% efficient at 3700rpm = 60hp. The guy that new 084's inside out was Less Smoote I think was his name. He did everything to them even EFI and that was 15+ years ago.
At Sea Level, the 084 is 45hp at I think they used 3300rpm, so that comes in at 85% efficient.
So 032 at 85% efficient at 3300rpm = 17hp
So 042 at 85% efficient at 3300rpm = 23hp
So 084 at 85% efficient at 3300rpm = 45hp
I sent you a PM with questions about your Le Pelican. Just wanted to make sure you saw it.
The most important thing to remember about the 2A042 & 084 (or any conversion other than the most common ones) is don't do it unless you really like working on engines. You might get to a level of reliability where you spend more hours flying it than you do working on it. Or you might not.
Just to add some semi objective information to this debate, I've attached the Mil Spec guide to installing a 2A042. From a quick look, it seems that there are guidelines for the moment of inertia of anything you're going to bolt on it directly. Plus there is some history with airboats, and there's been at least one ultralight. So I think it might not be quite as problematic as some potential installations. The specs say "Maximum horsepower at 3600 rpm" is 16.7, so things may not be quite as bad as they seem. They also say "maximum elevation for rated power" of 5,000 feet. And a maximum operating temperature of 120 F. So I'm thinking that means you can get at least the 10 hp under the implied hot and high condition. It's a questionable assumption, but if we assume that denser air means a corresponding increase in power, then that gets us up to 13 horsepower on a standard day at sea level. If we're fortunate, and that also applies to the 16.7 hp, we're up to 21.8 hp! Rumor has it that there's a restrictor plate in there, too. Recommended rpm goes up to 4,000, so perhaps when that restrictor plate is removed...
View attachment MIL-STD-1402 installation for 2a042 engine.PDF
I wonder how much that cooling fan uses up?
What I haven't been able to find anyplace is what a 2A042 weighs when you strip off all that junk it doesn't need in order to fly. Apparently it weighs 150 lbs with all the junk. Seems to me that's the most critical factor. And I'm a bit pessimistic.
BTW, if you want to keep tip speed down to 800 fps at 4,000 rpm, that limits you to a prop diameter of only about 46 inches! 5 feet would be better if not for that.
I've been wondering myself how much HP those cooling fansystem eat up myself.. could be easily 5hp
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