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Introduction
New engine? Everyone wants to know all about it! Recently, I had the opportunity to fly one and see just what’s “new” about the OS Max-46 AX engine. OS is retiring the venerable 46 FX, an engine I’ve flown for years. “Don’t worry,” states the ad, “there’s still a lot of the .46 FX in the .46 AX.” They are referring to the dual bearings, long crankshaft and locknut assembly, the ABL cylinder liner, and the identical bolt patterns. This last feature made it easy for me to fly both engines using one plane for the purpose of comparison. As it happens, I have been flying a .46 FX on a World Models Super Sport 40. Since I am comfortable with this plane/engine combination, I felt it made a great test platform to evaluate the performance of the two engines.
Before mounting the new AX, I compared it to its older brother. The AX looks quite like the FX…the engine configurations and parts locations are similar, but from there on, things begin to look different. The new E-3010 muffler is a bit boxier looking than that of the FX. The high-end needle valve sports a new bracket and composite housing, which was designed to prevent heat from the head from affecting needle settings.
Another noticeable difference: there is no throttle-stop screw poking up from the top of the carburetor barrel. I liked this feature. On my FX, this little beastie requires periodic checking to ensure that the spring-loaded screw doesn’t back out over time, changing engine performance. On the AX, the “rotor guide screw” as it is now called, screws into the back of the carb housing, presumably because it shouldn’t require frequent adjustment.
Because of its new location, one should remove the carburetor to tighten or loosen the slotted-head screw without chewing it up. By the way, the carburetor fixing screws on my FX need periodic checking to ensure they are tight; otherwise, they have a habit of coming loose at times, which changes the fuel mixture and kills performance. The arrangement on the AX appears to be much the same
The newly mounted high-speed needle valve offers two new features. The mounting bracket permits convenient changing of the valve position from horizontal to vertical, and the needle valve and housing are re-designed. Two Phillips-head screws hold the needle valve to the bracket; two screws hold the bracket to the engine. I found it easy to make the change, although I returned it to the factory-set position of horizontal to accommodate the test plane. The AX needle-valve housing is made of a composite material and is said to prevent engine heat from affecting needle settings. After break-in and during my test flights, I found needle settings to remain steady. Incidentally, the low-speed needle valve has a new taper, designed to reduce “surge” during throttle-up. Once set, the AX ran smoothly and did not hesitate during climbs, rolls or aerobatic moves. It responded smoothly whenever I gave it full throttle, even after “coasting” at idle. (Enjoy its great new sound in the 2 videos, below.) Time needed to set both low and high-end adjustments was minimal. I have found my FX to be rock steady once these adjustments have been made. Most changes in temperature and humidity require only one or two clicks of high end (lean or rich, depending on the change in weather) with no change needed to the low end. In the short time I have worked with the AX, it seems to behave just as reliably. As someone who prefers to fly rather than to tinker, this feature has made for many enjoyable flying days. One other feature I noticed is the cylinder head is fastened with only four screws on the AX, v. six on the FX. I think only time will tell whether this arrangement is better, although it appears that removing and replacing the head will be easier. OS brags that the new design automatically centers, levels and seats the head upon replacement. FX survived a crash.
One aside here, I once lost a plane in a mid-air. The same FX used in this evaluation was onboard when another flyer put his plane right through the middle of mine. I was flying inverted circles at the time. The wing broke in two and the fuselage came down like the proverbial lawn dart onto the tarmac. One result of the crash was that the needle-valve assembly (which is a part of the engine rear cover assembly) broke off. However, the engine ran fine after the crash, and after fitting it with a new rear cover, the FX was back in business. Perhaps the new bracket will reduce the potential for that kind of damage in crash situations.
SPECIFICATIONS:
Set-up
The AX comes nicely packed with an OS plug, silicon tubing, the muffler and bolts, and an owner’s instruction manual. OS motors always come well packaged. This one’s no exception. Mounting the AX on the test plane was a snap, because, as mentioned previously, its bolt patterns are identical to those of the .46 FX. The throttle linkage is in virtually the same position too, so that took no time at all to hook up and re-adjust. I popped off the FX and, using the same bolts, I installed the AX in less than 10 minutes.
Break-inDay one - Sunny and 70.
I brought the plane with the engine already mounted to the field. I like to break new engines in with 5% nitro high castor oil glow fuel. Break-in was simple. Following the instructions in the owner’s manual, I fueled up and cranked the AX. It started right up and ran well, not quitting until the last of the fuel was gone and the engine leaned out and stopped. I ran 6 tanks of fuel through it on the ground before flying it. While the directions call for only one tank to be run while varying the needle valve every 10 seconds, I ran the first two, as is my practice: varying 2 - 4 cycle operation every 10 seconds for the entire tank. I ran the next three tanks “rich” and the final tank, gradually leaning out the high end until it was just slightly rich.
PerformanceDay One ContinuesNext, I fueled up with 10% glow fuel, re-adjusted the high end, and flew the plane. The owner’s manual says the low-end factory setting should be good, but it was a bit rich and hesitated when I throttled up quickly. So I landed and tweaked it, leaning it out in very small increments, ending up about 1/4 turn leaner. Here it ran fine and responded very well. The manual also says to avoid flying nose-up for the first three or four flights, so I did. I couldn’t help sneaking in an occasional snap roll, or a split-ess to change direction. All the while, the AX was smooth and responsive. After several flights, an impending storm front announced its imminent arrival with gusty winds and an occasional droplet of rain, so I called it a day and packed up to go home.
Day Two - Windy and 40.I Arrived at the field around 8 a.m. and had the place to myself. From the temperature, humidity, and barometer differences, it was clear that the front has passed through during the night. I started the engine cold; it turned over right away, idling easily even after I removed the glow-plug starter and with no extended warm-up. I noticed the tight, clean sound of the new engine as it purred at idle. With the increased humidity, it needed but one click rich on the high end to resume the slightly rich running of the previous day’s workout. With a 10-12 knot wind blowing almost straight down the runway, I throttled up the engine and took off.
Videos by Matt Cernigliaro. Great job, and thanks, Matt! The wind was becoming stronger with each minute of the flight, but the OS ran steady and strong. To see how the AX compared to my FX, I did a few snap rolls and split-ess turns into the wind. The AX performed smoothly and without hesitation. I turned the plane over and flew inverted. No problems or hiccoughs. The OS ran smooth and the RPMs did not vary as I flew a circular pattern around the field a few times. I tried several high-speed low passes to check out the new muffler. The AX does run somewhat quieter than my FX. The new muffler has a softer, mellower tone. As the winds increased, and my fingers began to numb, I lined up for a landing and brought the plane down. The engine, once shut off, was just barely warm to the touch.
Day 3
Another not-so nice day. Gray and gusty, to about 15 knots, but flyable and an opportunity to test the AX power. The wind was switching constantly from a quartering wind to a crossing wind and other pilots were having debates about which way to take off. Once we decided, I taxied out onto the runway and lined up for take-off. The AX took full throttle without a beat and climbed into the wind. I flew several loops around the field at full throttle and the AX began to vary a bit, so I landed and richened the high-end one click. Climbing again, the AX was rock steady and smooth as the day before. I did some slow passes to see how the engine would do in the wind. It ran steady despite the buffeting from the gusts. I nailed the throttle to gain airspeed and the AX responded quickly and smoothly. High passes were also fine, although the turbulence caused the plane to bump around quite a bit. With the wind quartering, landings were a bit bumpy and the plane weather-vaned into the wind when I cut the throttle.
Props - performanceThe AX does fine with the suggested props. I needed only minor needle-valve adjustments after the change-outs. As with the FX, the AX runs predictably and reliably. It’s easy to adjust and a pleasure to fly. I flew the 10.5x6, the 11x6, and 12x6, all on the same plane, so this was not a true test of the engine under different conditions, but each time, the engine did just fine, achieving the expected result of pulling power or increased speed. The AX did not seem to be working any harder as I switched through the range of props. However, the AX seems to like the 11 x 6 best of all, running a bit cooler than with the 12 x 6 and being up to the task of pulling the Super Sports 40 along quickly. With the 11 x 6 prop, I can almost hold the plane in a hover and it will climb almost out of sight.
SummaryKey Features List
Flight ConclusionsI have flown OS two- and four-stroke engines, and they have proven to be quite reliable and ready to work with relatively little care. During the warm season, I often put them away after a weekend of flying without applying after-run oil. The next week, they start right up. I fly them hard and they perform without constant adjustments. Once set, they continue to run well, and usually require only minor tweaks on the high end. They idle smoothly without quitting, and transition smoothly as well. While I have only a few days’ experience with the AX, it is already demonstrating that it a great running, well-engineered engine.
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May 16, 2006, 01:40 PM
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#2 |
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Registered User
Join Date: Jan 2005
Posts: 6
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Nice engine ad but not a review. No mention of rpms at all...or even once. Sorry, but this is not a very good evaluation of an engine.
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May 29, 2007, 06:00 PM
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#3 |
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Registered User
Join Date: May 2007
Posts: 1
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Sorry, but RPM WERE mentioned, and more than once. This obviously is not an engineering article, but it does cover how a regular user feels about the engine. And the video is pretty impressive!
I'm getting one of these engines. First, I'll make a trainer, and then a WWII plane. |
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Jun 07, 2007, 11:26 AM
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#4 |
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Foamphobic
Join Date: Dec 2003
Location: Laguna Beach, Ca
Posts: 396
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I just bought one of these engines with the intent of using it in a Funfly 3D plane. I hope it really makes the plane hover. WS about 1.44 mts and 1.4 kgs.
Will be using an APC 11x5. |
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Jun 21, 2007, 04:05 PM
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#5 |
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stevo
Join Date: Feb 2007
Location: monster maryland
Posts: 546
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im also bought 1 imma gonna use it in a ultra stick see if it ill ake that hover
funkworks must be blind |
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Jun 21, 2007, 04:06 PM
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#6 |
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stevo
Join Date: Feb 2007
Location: monster maryland
Posts: 546
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im using an 11x8 apc
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Jul 16, 2007, 03:34 PM
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#7 |
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Registered User
Join Date: Jan 2005
Posts: 6
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sorry spitzelder. I freely admit not to being the sharpest knife in the drawer..haha. However, the only mention to RPMs I noticed in the article were under the specifications section which are actually what the company advertises. I wouldn't buy into the advertised rpms so easily. Robert started well in going to the trouble of trying different props but it would have been nice if he'd taken a tach reading for each. Its a lot more objective than just discribing how the plane "felt" with each prop.
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Aug 21, 2007, 05:56 PM
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#8 |
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PlaneCrazy
Join Date: Sep 2003
Location: Central California
Posts: 2,493
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You want an rpm reading 17,500 with a 9x8 using a nelson pipe on 15% fuel.
Doug |
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Oct 24, 2007, 01:33 AM
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#9 |
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Registered User
Join Date: Oct 2007
Location: Springville, Alabama
Posts: 4
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Rpm
RPM has nothing to do with performance unless you are in a race. High rpm setups generally do not have it in a straight up pull. They tend to start slipping which is the same as cavitations in water as experienced in a boat. High RPM as experienced with the use of small diameter props tend to produce setups with non repeatable flights as far as performance is concerned and drastically reduced idle performance. There is little or no flywheel effect so maneuvers which require throttle control suffer. RPM and performance varies from plane to plane and set up to setup thus making the RPM factor almost useless except for bragging.
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Oct 29, 2007, 03:37 PM
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#10 |
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OK,so what's the speed of dark
Join Date: Aug 2006
Location: Glenwood,GA
Posts: 799
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Sorry Mr. Sparks, but that statement just is not true.
It was a good review and interesting, but I would have liked to see some RPM readings with the different props and it would have been nice if you had done it for both engines with each prop, just to see if there was any improvement with the new engine. Nice to know how the engine pulled the plane with the different props though. Keep up the good work. Ed |
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Jan 10, 2008, 07:34 AM
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#11 |
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Registered User
Join Date: Dec 2006
Location: Newark, Del., USA
Posts: 3
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For a "non-engineering" review I found it pretty worthwhile, though tach readings would certainly have helped.
But I was HORRIFIED by your video. Making a giant C-Clamp out of your body with the plane of the prop slicing thru it, while hanging onto the tail, working the throttle and finagling a spinner flip is not what Dr. Safety recommends...!! Nice to know it starts so well, though. Reminds me of my OS-25 Fp from years ago. It was a C/L engine which I simply converted to RC by putting a throttle-carb on it. It always started with a single flip at any throttle setting, even with a single AA battery when I had no Ni-starter! Ash |
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Aug 13, 2008, 09:36 AM
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#12 |
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Registered User
Join Date: Feb 2008
Posts: 7
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can itbe the i used acaculating program and it sho me that i have 4KG,s thrust?
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Oct 19, 2008, 08:55 PM
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#13 |
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Proudly Canadian Modeler!
Join Date: Aug 2008
Posts: 744
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Thanks for the great review. I just bought the engine, and experienced reliable preformance right from break in.
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Jan 21, 2009, 06:05 PM
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#14 |
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Stress Be Gone
Join Date: May 2000
Location: Snohomish, WA
Posts: 2,735
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I wish they had chucked the remote needle valve and just went with the newer slanted needle valve such as on the 35 and 55AX.
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Feb 02, 2009, 12:06 AM
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#15 |
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Registered User
Join Date: Jun 2007
Posts: 83
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Replace an EVO 46 with this Engine?
I have a brand new Evo 46 in a H9 Pulse XT 40 PNP, I have had three flights on it. 1st flight, I dead sticked it to a fence post and ripped the wing off the fuselage, 2nd and 3rd flight ended in dead stick landings again. IT will not stay running. I am getting fed up with it. (My 1st glow plane). If I but an OS 46 AX is it a direct replacement for the EVO 46? What changes might I have to make? Beside the throttle linkage?
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