O.S. 110FS
Contents
1. COLUMN O S L1OFS A FOUR STROKE GLOW ENGINE O S is well known for quality products and innovation plus they have countless years of experience with four stroke glow powered engines In 2007 they introduced the 56F S a the first in the new Alpha series lineup of four stroke glow engines Next came the 81FS a followed by the 110F S a which is the subject of this review These new Alpha series engines feature an all new look plus some interesting new features aimed at minimizing the mess in and around the engine compartment of your favorite airplane all with mounting interchangeability light weights and compact sizes that make them easy to install into many airplanes hy to Buy The 110FS a is easy to start and tune has excellent idle characteristics transition and power plus it fits ath the same f n i TI ii _ E BY Mike Hoffmeister sS a ES ja The O S 110FS a comes well packed in a high quality bubble pack envelope and box and includes muffler instructions decals and a flexible extension plus knob for the high speed needle valve This side view shows off the 110FS a s compact size cool new look and superb finish amp lt N i poa P G This front view clearly shows the new cooling fin arrangement narrow profile and machined aluminum pushrod tubes The new logo on the rocker cover is also a2. engine very rich for several seconds then lean it until rpm come up and it s running clean at near peak revolutions Hold it for a few seconds and then immediately richen the high needle until the engine slows considerably and starts blowing a lot of smoke and fuel mist from the exhaust then repeat Over the course of the first two tanks of fuel this process is repeated over and over with steadily increasing durations of near peak rpm periods of operation This process is intended to run the engine through varying loads and rpm ranges and also to heat cycle the engine by getting it warm during running done with near peak needle settings then cooling and lubricating it quickly with a great amount of fuel when the needle is opened for the periods of rich running Once the break in was complete I tuned the low and high needles in a back and At first this looks like just another engine hardware layout but it s worth taking a very close look at each part This engine is truly a work of art with casting quality machine finish and an overall parts fit that is second to none forth manner until I had a slow and steady idle with clean acceleration even when the throttle was opened rapidly I set the high needle about 200 rpm on the rich side of peak a few clicks more open on the high needle than the setting that produces highest rpm The instructions include a clear step by step approach at tuning the ca
3. known for The F 5040 muffler allows substantial installation flexibility since the muffler can be rotated a full 360 degrees the outlet can be angled by rotating the rear muffler part relative to the front The 60Y carburetor is reversible and has proven to perform well and tune easily The extended venturi tube helps minimize reversion spit back of fuel out of the carb inlet which makes the engine cleaner running and a bit more fuel efficient Here is a close up of the crankshaft showing the helical cut gear teeth lobes and alignment mark used to assure correct timing during installation exception was the APC 15x10 propeller This one produced significantly more load than the others and it required a much richer setting on the high needle to avoid a lean condition and detonation For this propeller I had the high speed needle about a half turn richer than for the lowest load propeller tested the Master Airscrew 15x6 I was very impressed with how well the engine ran with a very wide range of propellers From the lightest load to the heaviest load propeller the peak rpm covered a range of nearly 2500 rpm but with each propeller it ran like a top Engine Hardware Layout All four stroke engines involve a certain amount of complexity to disassemble and more importantly to reassemble due to parts count and items like getting valve keepers back in place and cam timing set correctly But I have t
4. nice touch I t WA Z andall testing I mounting bolt pattern as the FS 91SII It also has innovative features which nearly eliminate fuel and oil mess in the engine compartment It has a reversible carburetor which allows installation flexibility and it can happily swing a large range of propeller sizes Plus it s backed by a two year warranty policy While engines in this size range are not inexpensive you can usually take advantage of a discount offer at towerhobbies com to take a chunk out of the purchase price Break in and Performance Testing I used Cool a Power 20 heli fuel for break in have found that higher nitro content in four stroke engines improves the idle transition and ease of tuning plus it gives a slight boost This rear view shows how O S has angled the intake manifold to get the carburetor centered side to side Reversing the carburetor is a two minute job plus access to the needle valve and glow plug is easy in power particularly when running a higher load propeller So I went with the highest nitro percentage recommended in the instructions Just make sure that the fuel you select complies with the requirements listed in the user manual The manual lists a huge range of propellers that are suitable for the engine from a 13x9 on up to a 16x8 I have several propellers in this size range so I elected to test five different propellers that wer
5. oz 672 About the only engine 4 EET otal Weig oz 672 grams maintenance required for E APC 15X10 Engine Only 19 2 oz 600 grams the 110FS a is the occasional 2 ao Matarae 16Xe Weight gt Master Airscrew 15X6 j adjustment of valve clearance OO MufflerWeight f 2 3 oz 72 grams This is well documented in the 0 2 000 3 000 4 000 5 000 6 000 7 000 8 000 9 000 10 000 11 000 Buonrshatt ae 24 instruction manual including Threads illustrations As the engine Dreakg i IE yaNe CERTANCE This graph shows how thrust relates to engine rpm for each of the five propellers change slightly and readjustment tested of the clearance is necessary to maintain optimum performance If allowed to get too tight the valves may not fully close allowing leakage and loss of compression If valve clearance gets excessively large there will be an increase in valve train noise and power loss due to the valve not opening as far or staying open as long This is nothing new for the 110FS a and it is common to all four stroke RC aircraft engines I checked the clearances after RPM Propeller Range 13x9 16x8 Rpm Range 2000 to 11 000 rpm Fuel 5 20 nitro Mounting See towerhobbies com Dimensions Muffler Type Cast dual chamber Cylinder Type Plated sleeve Carb Type Barrel Two Needle Valve Crank Type Dual Ball Bearing Great Planes P O Box 9021 Champaign IL 61821 Phone 800 637 7660 Static Thrust Ibf O
6. Static Thrust Ibf O all of the test running and found 4 o APC 16X6 i Pe Web site greatplanes com ope e E APC 15X10 l APC 15X10 them to be within specification h E a ends 2 4 Master Airscrew 16X6 Medusa Research Inc so no adjustments were required G gt lt Master Airscrew 15X6 288 Plymouth Avenue I have found O S engine Xoar 15X8 Wood 0 ee eee Fall River MA 02721 castings and finish machining o gt ae re pa BA pa m ma 0 10 20 30 40 50 60 70 80 Phone 508 675 0202 to be of extremelv hich qualit ae itch M Web site medusaresearch com e e eam Throttle Stick Position Pitch Speed MPH but they have raised the bar ee Hobbies P O Box 9078 even further with this er This graph shows how thrust output varies with throttle position As throttle is This graph shows how static thrust and static pitch speed relate to each other For Champaign IL 61826 9078 have never seen casting so finely advanced to about 80 there is a steady increase in thrust and past 80 thrust maximum static thrust pick the one with highest thrust but to trade off some static 800 637 4989 orders finished with sections carefully remains relatively constant As an example for an 8 Ib 3D airplane a Master Airscrew thrust for more pitch speed this graph provides visualization of the trade off Web site towerhobbies com thinned down for weight savings 16x6 prop would h
7. e previously used to test a similar size four stroke glow engine This includes the APC 16x6 and 15x10 Master Airscrew 15x6 and 16x6 and the Xoar 15x8 After securing the engine to the test stand fueling the test stand tank connecting the hoses and double checking everything I slowly turned over the engine a few revolutions until I saw fuel in the hose all the way up to the carburetor Then I turned it a couple more revolutions A quick bump from a Sullivan Dynatron starter immediately brought the engine to life biik The 110FS a engine and F 5040 muffler both share distinctive styling and the muffler mounting offers 360 degree adjustability The 110FS a is shown in action mounted to my thrust test stand with the camera flash freezing the APC 16x6 prop The throttle servo can be controlled by radio control using a Spektrum DX7 radio for break in and carburetor tuning or switched over to computer control for a test run with all data being displayed and recorded by the computer The 110FS a is attached to the test stand via adjustable mount legs The small circuit board just behind the propeller hub is the optical tachometer which is part of the Medusa Research Power Analyzer Pro data system The break in process requires running the engine wide open but with a widely varying high speed needle setting Basically you run the
8. ents or extended periods of idling The test stand is run and monitored by computer so it s possible to do exactly the same test over and over with minimal variation The The piston is fully CNC machined from bar stock with careful attention to weight reduction while retaining rigidity and strength standard test that I run has the engine running for five seconds at stable idle then five seconds at 20 throttle then five seconds at 40 throttle and so on with the final five seconds at wide open throttle All the while the data system is capturing rpm thrust ambient temperature and cylinder head temperature on the back side of the head between two fins In a test taking This close up of the crankcase casting shows off the great lengths that O S developed in order to minimize weight and size while maximizing cooling efficiency and rigidity less than one minute a large amount of data is captured which then allows graphing of the results for easy interpretation and comparison of various propellers After this first test I then changed propellers several times until I had a good clean test run for each of the five propellers included in this review I found that the high needle did need to be adjusted with each propeller change but most of the time it was only a few clicks The one This close up of the connecting rod shows the beefiness of the part and finish quality that O S is
9. er seen due to As the oil flows through these the FS 915SII which it shares compact and lightweight It is the unique lubrication system various passages and parts of the mounting bolt pattern and easy to tune produces excellent and extended carburetor venturi engine it is serving the purpose Whether you are equipping a new of lubricating the various parts Koar 15X8 model or upgrading the engine along the way O S has also This view of the crankshaft shows two small holes that are part of the oil system The Onan existing model the O S added a purposefully designed larger hole to the right of the cam drive gear directs most of the excess oil from the 110FS a is a great choice To see crankcase up into the cam box while the smaller hole to the left of the cam drive gear provides lubrication to the front ball bearing which supports the crankshaft long venturi tube that attaches to the inlet side of the carburetor to minimize spit back more accurately called reversion The other benefit of this venturi tube by eliminating fuel lost out and hear the engine run please see the video at rc sf com J Type Four Stroke Glow ignition of the carburetor fuel efficiency 10 engine engine to stay quite clean and an 1 196 in 30 4 mm dry with very little fuel oil mist l o Stroke 976 in 24 8 mm landing on and speckling the test 6 stand S Cylinders Single j Total Weight 21 5
10. o say the O S 110FS a is as easy as they come The engine does not use any paper gaskets with all interfaces being sealed by rubber seals or metal to metal contact of the very finely machined surfaces This makes maintenance much easier with minimal fear of experiencing a torn gasket Also the propeller hub is locked rotationally to the crankshaft by a Key so it isn t necessary to use a puller to get the drive hub off the crankshaft it simply slides off allowing the key to be picked out with bare fingers The 110FS a features a lubrication scheme that eliminates the overboard crankcase breather that is common to most four stroke glow engines by directing excess lubricating oil that accumulates in the crankcase forward through the crankshaft up through the cam box and pushrod tubes and into the rocker cover area where it is finally fed to the intake port to be recycled COLUMN This table shows the top rpm static thrust and pitch speed achieved with 0 S 110FS a Four Stroke Glow overall size with and it delivers power and happily swings a very each propeller tested Static Thrust Ibf Pitch Speed MPH Conclusions very similar performance to wide range of propellers It is seecccsceccscecscscsccccscscssscsccscsces PERM The O S 110FS a provides a competing engines in the same one of the cleanest running four substantial power increase vs size range in a package that is strokes I have ev
11. over the plane at about 30 throttle
12. rburetor With the larger propellers the engine could easily hold 1800 to 1900 rpm idle without stumbling upon quick throttle opening and it also held steady rpm at full throttle The exhaust note is quite pleasing with the dual chamber On the left is a view of the cylinder head with the rocker cover and intake valve spring retainer removed Note the small hole below the valve spring seat this is where the excess lubricating oil is routed to the intake port to be recycled thereby eliminating the need for a messy crankcase breather On the right a view of the combustion chamber with the intake valve removed shows the same small hole just above the larger valve guide hole COLUMN The crankshaft is a beefy one piece unit with a super smooth precision ground surface on the areas that mate with the crankshaft bearings and connecting rod bearing aluminum muffler doing a nice job minimizing noise I plan to start reporting sound levels in my future engine reviews but did not get the data in time for this one For this size engine the 110FS a has a soft exhaust note which is pleasing to the ear and to your neighbors around the airfield The first propeller I ran for break in and performance testing was the APC 16x6 It turned an impressive 9 025 rpm producing just under 14 lb of thrust with a 51 mph pitch speed Idle was very steady and the engine simply ran flawlessly regardless of throttle movem
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