Charlie, interesting project!
I've been curious what all goes into adapting an automobile engine to work in an airplane. On the surface, seemed as easy as plopping it in and putting a reduction drive between the engine driveshaft and the propeller, but obviously things are never that easy haha.
I'm curious: what do you think of Mercedes' M139 2 liter engine outputting 416hp? https://en.wikipedia.org/wiki/Mercedes-Benz_M139_engine
Seems like it would be the perfect automotive engine to stick in a plane? It's a Mercedes engine so you know it's going to be very reliable. And it's a 4 cylinder only 2.0 liters that is producing over 400hp. My guess is that weight will be the biggest problem? I believe it weighs 385 lbs. But given all of that power, the weight should be easily overcome so I suppose the real enemy will be CG?
Also, I'm no airplane engineer but how does one increase MTOW? Will extra power increase MTOW or is MTOW dictated by something else in the structure of the plane? Or will engine power increase MTOW slightly, up until you reach structural limits of the airframe?
So if engine power will increase MTOW then you don't have to worry about the extra weight of the engine, except for the CG, is that right? And then could you just add counter weights to rebalance the CG?
Charlie, interesting project!
I've been curious what all goes into adapting an automobile engine to work in an airplane. On the surface, seemed as easy as plopping it in and putting a reduction drive between the engine driveshaft and the propeller, but obviously things are never that easy haha.
I'm curious: what do you think of Mercedes' M139 2 liter engine outputting 416hp? https://en.wikipedia.org/wiki/Mercedes-Benz_M139_engine
Seems like it would be the perfect automotive engine to stick in a plane? It's a Mercedes engine so you know it's going to be very reliable. And it's a 4 cylinder only 2.0 liters that is producing over 400hp. My guess is that weight will be the biggest problem? I believe it weighs 385 lbs. But given all of that power, the weight should be easily overcome so I suppose the real enemy will be CG?
Also, I'm no airplane engineer but how does one increase MTOW? Will extra power increase MTOW or is MTOW dictated by something else in the structure of the plane? Or will engine power increase MTOW slightly, up until you reach structural limits of the airframe?
So if engine power will increase MTOW then you don't have to worry about the extra weight of the engine, except for the CG, is that right? And then could you just add counter weights to rebalance the CG?
Please someone prove me wrong and show me a successful plane with an auto conversion. If they were so wonderful, there would be a lot of them out there. There is so much more to an engine than water cooling, and prob reduction drives. Car engines don’t have the surface area on the rod bearings, or the beefiness in the crank and rods that aircraft engines do. Aircraft engines and their crank, rods and bearings are tremendously oversized for their hp load..low surface speeds on the bearings, wide crank journals, all add to their reliability. This isn’t meant to poopoo on the original poster and his project.. I support others experimenting with.. well, experimental aviation. I think it’s great that he’s doing something out of the box and having fun and learning from it. I was just addressing the guy who thought it may seem simple..
I?m reading the latest comments and following this thread with great interest. Wishing Charlie the very best...
I take exception to a comment ?Aircraft engines and their crank, rods and bearings are tremendously oversized for their hp load..low surface speeds on the bearings, wide crank journals, all add to their reliability?.
In my opinion aircraft engines are designed very light and must be spoon-feed very carefully to maintain reliability. Highly-leaded fuel must be used to prevent detonation. Likewise, very conservative ignition timing is used to limit pre-ignition / knock. Aircraft engines develop case and cylinder head cracks with regularity. Air-cooled cylinders don?t stay round and shock-cooling is the enemy. Acceptable oil consumption is something like 1 qrt/4 hours. Fill engine to full mark and it blows oil overboard.
Just adding my two cents?
... I just would have moved the radiator forward about 6" - 10". and may be even have a longer engine mount an inch or two. Minor, but worth the thought.....
II think that moving batteries closer to firewall would be first step. You'll save some weight from the shorter cables. Extending engine mount will add weight.
Finn
regarding the cooling filling, I recently purchased and used one of these vacuum fill setups. it's supposed to solve any trapped airbubbles problem:
https://www.amazon.com/UView-550000...e+Tool+Kit&qid=1596726370&s=automotive&sr=1-1
It seemed to work really well, and fast to fill the system. I haven't done a test flight yet (maybe I'll get to fly today).
Here is a guy using the same one on a truck:
https://www.youtube.com/watch?v=eMvalUMNyYU
My wife has joined me in wrenching on the plane, every day for 2 weeks to get this ready for the airworthiness inspection. She's an absolute gem.
It is tedious but we are making good progress.
One thing that stands out to be is how "sqatty" it is. Quite tail low. I put a 1.5" thick board under both tires and it is still quite squatty. I have always known the -6 still low compared to the -9 an -7 and I don't like it.
It makes for poor visibility. on landings. Larger diameter tires would help in several ways. 1) More stability, wider tires, stronger tires. 2) Better visability over the nose. 3) better larger brakes. Tires are actually cheaper too. The down sides are reduced speed, and some added weight. I care more about better visibility and stronger breaking and stronger tires than I do the reduced speed and increased weight. So I am 98% sure I am going up to 6.00x6 tires on the mains. I know this is unusual for a -6a. But the -6 guys do it all the time. I set it up this way and put a level on the longerons and it takes me from 5.2 degrees tail low up to only 3.7 degrees tail low with a 1.6" lift that I expect I would get with 6.00x6 tires.
Just food for thought....
Oh....I dont plant to run with pants. Seems like more hassle than the speed gains you get that are not that important to me anyways....
To those who have been patiently following, I received my Air Worthiness Certificate today. I am very happy about that.
If your batteries are pretty low you will see high amps initially and then as the levels get higher the charging amps will drop. Are the batteries fully charged?
Is your ammeter measuring the total amps being used by the system or only the amps going into / coming out of the batteries?
If the output of your alternator is below 15 volts, there’s nothing wrong with it. The current draw is a function of the batteries and other electronics.
-Andy
Well, good new on the alternator, it was fine. I after starting the engine I checked and the voltage was within range (I think it was 14.6 or close to it). So I let it run. Andy was right. Turns out the batteries were drained more than I would have thought 13.1v would have indicated. The trickle charger just did not bring it up to full charge. A good lesson for me on what to expect out of my ammeter.
I was able to get out on the runway today to get up enough speed to condition the brakes. They hold much better now.
Next up: A new gremlin in the headsets and more finish work to do on the radiator scoop.
My honda fit has 300,000 km on it and runs perfectly, never let me down. There is no doubt it is a great engine. Like every automotive installation in an airplane the devil is in the details. Every builder does it differently. And little details have become big problems very often in these types of installations.
I would say you should plan to have an engine out in your first 50 hrs. Depending on where you fly and how confident a pilot you are, that might be manageable. Like if your airport has 5000 ft of pavement and you can do your testing 3 or 4000 ft above it. But if you have a 2000 ft strip surrounded by built industrial area and it is always really busy... hmmmmm. Lots of practise of forced approaches... Planning for that scenario just makes sense based on past history of auto conversions of all types. You might not have any problem, but prep and planning is how you manage the increased risk. That’s how the pros do it.
I hope you are very successful.
Yes mechanical things do break for no reason, my first landing in suby powered
RV 4 was dead stick as crankshaft broke 1400’ above airport, exciting but no
Problem ! 2nd engine never even hicuped !
Scott,
My plans exactly. I am very fortunate I am based at KTDO which has almost 4500ft and is rarely busy.