Source: 2003 Q2 Beartracks, by Mike Meador
Let’s hear a little bit from Tom Yeoman about his Lycoming (formerly Ford) powered Bearhawk from the Bearhawk Yahoo group:
Hi Group, I just uploaded a few pics of my bird with its new paint and Bob’s O-360-exp engine. I am feeling much better with not worrying about anything I may have done with the Ford conversion that was in it. Continue reading
Deciding on an engine is usually something that Bearhawk Builders always have on their mind. Bob and I would like to suggest our idea of the ideal Bearhawk engine.
In part V of the Engine Choices series I had a breakdown of the perfect combination O-360 Lycoming for use in a Bearhawk. The photo below shows the Lycoming O-360 as built for Tom Yeoman (#75) and is a good example of the type of engine that you should consider.
Many builders think that bigger is better, and that may be true up to a point. The largest engine that Bob recommends for the Bearhawk is the O-540 260HP Lycoming. This engine gives fantastic performance and in the hands of a disciplined pilot it can be operated economically. It is not a difficult engine to obtain and like most Lycomings, it is easy to work on. The 540 does have its drawbacks, mainly in the form of a lot of weight out on the nose. The Bearhawk can handle the weight, but you have to play around with the battery location to get the CG just right.
As desirable and effective as the O-540 is, there is a better choice in the O-360. The prototype proves that the O-360 is a more than capable powerplant for the Bearhawk. The acquisition costs and operational expenses for the four cylinder are a great deal less. Your flying range is extended with lower fuel flow and lighter airframe. Your useful load is maximized because the engine is not as heavy, a smaller battery is used, shorter and smaller cables are used, and a lighter prop can be used. The O-360 Lycoming is a good fit for the original Bearhawk mission- to carry a large load and operate effectively from short grass strips.
As an example of what you would expect for engine prices, R&B Aircraft sells the “Bearhawk Standard” Lycoming O-360 for about $13000- that’s ready to run, magnetos and carburetor included. A 6-11 month lead time is typical for an engine order of this sort so don’t wait until the last minute to start lining up your powerplant.
If you have any questions about the suitability of an engine for use in your Bearhawk, give us a call and we can discuss it.
Source: 2002-Q4 Beartracks, Mike Meador and Bob Barrows
Sometimes it is difficult to put into words (particularly written words) that which you know. To transfer knowledge that has taken many years to acquire in a few short paragraphs is not a skill that I have mastered very well. I marvel at other writers’ ability to take a difficult subject and make it understandable to me. It would be easy to give yourself a list of part numbers and say “Here you go! Assemble it according to the manual and you should be OK.” Stuff made today is almost idiot-proof, but, I am an example that they are making better idiots every day. I thought that this series of articles would serve to show you how easy it is to put together your own engine. Instead it has served to be a list of generalizations that can only steer you in the right direction to a destination- mainly the perfect Bearhawk engine.
In this final installment, let’s discuss fuel delivery systems and various ways to light your fire.
As you already know, the Bearhawk will operate via gravity flow for a carburetor, so no fuel pump is needed. If a fuel injection (FI) system is desired you will need not one pump, but two: the mechanical pump attached to the engine, and an electrical boost pump for backup. FI systems are more expensive, and as a result of needed fuel pumps, weigh more than a carburetor. The main advantage of FI over carburetor (for the Bearhawk application) is the difficulty in developing intake, or carb ice. FI is expensive, and can run as much as $1000 more than a comparable carburetor, and that does not include the extra fuel pumps!
There is a middle ground between the two systems called a pressure carburetor. It requires a fuel pump but has a lot of the advantages of FI system that are not really needed on a Bearhawk. The ability to fly inverted is not something that I think you will need to be doing very much of anyway.
The ideal Bearhawk engine will take advantage of the “free” gravity flow and use a carburetor. The limitation of carb ice is something that you should have been trained to deal with in your flying lessons. There are devices that can warn you when ice is building up, or you can keep your manifold pressure gauge (if so equipped) in your instrument scan. A slow drop in manifold pressure during cruise indicates a building restriction due to possible carb ice. Most carburetors are shop rebuildable, where as the FI system needs very specialized tools and training to work on. Finally, the carburetor is the most cost-effective way to deliver the fuel/air mixture to the cylinders. We are in the business of keeping it simple, and carburetors do just that.
The final systems to consider are the ignition systems. Up until recently you really only had the choice as to what brand of magneto you wanted to install. There are now several different types of electronic and mechanical systems that you can choose from. There is a reason that the magneto has reigned supreme for nearly 100 years- it works. Any electronic ignition system (EIS) that you choose must have a built-in redundancy to prevent engine failure. The main disadvantage of the magneto is that once you have set your timing it is set for good regardless of power setting. With the exception of startup (due to impulse coupling) you are locked into the advance you set the mag at. This is where the EIS really prove their worth- variable timing. Another advantage of the EIS is a much hotter spark that results in an improved flame front and better fuel burn. Currently Unison Industries (Slick) is considered to have the most advanced EIS on the market.
The Slick system is actually two magnetos with a piggy-backed electronic ignition built in. In effect you have four ignition sources- sounds like a lot of sparks. The Slick system is certified and is available to home builders. There are at least two other non-certified EIS available. So far the results have been generally good, and that is promising. Most of the engines that we ship out of our shop that have an EIS also have one old-fashioned magneto for backup.
Another system that looks intriguing uses miniature catalytic converters to light off the fuel/air mixture; it has no moving parts. I’ll take a wait and see approach- in other words, you go first.
That about wraps up your Bearhawk engine. As you can see you have a bewildering number of choices. So I would like to present you with what I consider to be the perfect Bearhawk engine. The following listing has been worked up with the Bearhawk in mind:
This is nearly the exact engine on the prototype Bearhawk. It is relatively inexpensive to build and a brute of an engine. The angle-valve head keeps things cool during those long climb outs and the large valves let it breathe a lot easier.
Source: 2002-Q3 Beartracks, Tom Yeomans, #75, Edgewood NM
Hi Bob and Mike, here are a few pictures of the auto-powered unfinished Bearhawk.
The first flight of no. 75 was June 26th, 2002. I don’t have a lot to talk about as far as the flight characteristics of the aircraft itself at this time. Control time spent in the air has been very straightforward with no bad habits to report. The first flights have been short due to engine concerns. During the first flights I was able to do some adjusting of the control systems to get all of the cabling adjusted correctly. The aircraft has a short takeoff run, likes to climb, and a straight rollout in a three-point landing.
The engine is a Ford Duratec 3.0 24-valve engine I have converted myself. I am using a 2:1 belt reduction, electromotive aftermarket ignition/fuel injection, stock Ford injectors, starter, induction, and alternator. Most of the time spent so far has been dedicated to cooling, ignition, and a few mechanical items that do not reflect on the aircraft design at all. I knew going into the auto conversion that I would need to do some changing. I elected to not do an exterior finish until I had all the bugs worked out with the engine. The first flights had the engine sounding good and the RPMs seemed good. During the fifth flight I had an ignition misfire that had me digging into the problem quickly after the flight (I did finish a normal flight). The exhaust was looking very rich and the fuel burn was very low (sounds confusing). No guess at the real horsepower, but can’t be much. I did get a new chip for the onboard computer and offline software.
I have the cooling system temps running under 200 degrees during climb now and the ignition system is very close to a final dial in. I have a little more testing on the ground to do but should be back in the air early September. The fuel burn is now in the 8-GPH range according to the software.
Lessons learned here are, if you want to get in the air faster, talk to Bob about one of his engines, or if you want an auto system without tinkering with your own conversion, look at one of the companies that have lots in the air already. Hope everyone has a great finish to the year and many get their projects flying soon.
Source: 2002-Q3 Beartracks, Bob Barrows and Mike Meador
The one area of engine building that offers the most choice of services is the cylinder. You can choose to have your cylinders cleaned and checked and overhauled. You also have the option to buy new. If the cylinder is low-time (less than 300 hours) Continue reading
Source: 2004-Q2 Beartracks, Mike Meador and Bob Barrows
Well 6890 Romeo was looking a bit tired after just 900 hours of service. We decided to do a bit of sprucing up and a very careful inspection of the engine, engine systems, and airframe structure.
Continue reading