RE: OS 33GT Gasoline Engine for Pattern
 

Hi Tony,

A nose ring controls the side motion of the propeller during any maneuver where load increases beyond 1G. For hard mounted engines and certain types of "soft" mounts, it isn't required. However, for the Hyde style soft mounts which provide complete rubber isolation from the airframe, a nose ring really helps control the prop, maintaining its centering through any maneuver no matter how violent.

A plane still flies okay without it but you will notice some wander as you pull or push even moderately hard for squares for example.

Anyway, I will post some photos of my set-up soon.

RE: OS 33GT Gasoline Engine for Pattern
 

how would a focus 1 work with this engine?

what header and pipe would be needed?

biggest question, how is the weight limit handled at contests?

tony

RE: OS 33GT Gasoline Engine for Pattern
 

Local events don't care that much about weight or weighing anything. So if yours is a few ounces over none's the wiser since it doesn't much matter. Even at the Nats, unless you are a finalist in Masters or F3A, chances are pretty good that it won't be weighed. Except for this year, 2012, where Archie weighed everyone, (I think)

The Focus 1 was reasonably light regardless and unless it has been crashed a few times and pick up a pound or two, you shouldn't have much problem.

Headers and pipes are covered extensively herein
You may want to talk with Merle Hyde at Custom Hyde mounts, to see if he can build you one. I make my own

RE: OS 33GT Gasoline Engine for Pattern
 

how competitive would a gas powered focus 1 be?

tony

RE: OS 33GT Gasoline Engine for Pattern
 

I have no idea how good a pilot you are or what class you fly. It will be as competitive as you are a pilot. Powerwise there is no issue. If you use the muffler instead of a pipe, it will be loud and distracting so I'd suggest against that

Anyway, here is my nose ring set-up. The ring is 2 layers of 1/32" aircraft ply laminated with carbon cloth. The center hole is oversized and note the recess that surrounds the Hall sensor. Then a rubber ring is installed which is a snug fit around the case bearing housing

RE: OS 33GT Gasoline Engine for Pattern
 

We're gonna do a pic-tutorial on nose ring details

RE: OS 33GT Gasoline Engine for Pattern
 

Some more. Note the tight but adequate clearance in front of the Hall sensor. There is 1/16" clearance there after some careful carving of the Hall sensor housing. That's all that's needed to secure the nose of the engine

RE: OS 33GT Gasoline Engine for Pattern
 

and a few more....

The couplers for the exhaust system are home made. It has been discussed before but is worth repeating. I laminate ceramic fabric layers (at least 2 layers depending on thickness on hand) and impregnate the fabric with Permatex ultra copper gas resistant silicone. The lamination is secured onto the appropriate diameter mandrel, such as the actual exhaust pipe I'm going to use. The mandrel has first been wrapped with teflon tape to keep the mess from sticking and ruining my day. I learned that lesson the hard way.

Then more teflon tape is used over the top of the sticky fabric wrapped snug to make the assembly more uniform. This is allowed to cure for a day. Teflon tape unwraps beautifully and the coupler is easily removed from its mold. The great thing about this technique is that one can fashion angled couplers just the same, or any shape for that matter as long as the mandrel will allow release. No undercuts for sure.

Almost forgot....the couplers shown have over 50 hours of run time on them, over 10 gallons of run time. Still are fully functional and have lots of life left. The ceramic fabric I use was purcahsed from McMaster Carr. It is silica type but any of them will work, even the least expensive ones; more expensive than glass but worth it in the end. If you tackle this project shoot me an email....and definitely wear gloves. You have got to work the silicone into the weave with your fingers. You see, the silicone inside burns off in a couple dozen flights leaving the ceramic layers to protect the rest of the thickness.

This coupler is superior to anything else I've seen, including teflon. It seals easily and only needs a pair of plastic tie wraps to secure, just like old times with 2 stroke glow engines which run cooler than anything else. For a YS glow set-up which also tends to run almost as hot as gas, one coupler will last as long as one needs

RE: OS 33GT Gasoline Engine for Pattern
 

The tank is a 330 ml water bottle fitted with gas fittings I sell. If you need some shooot me an email at [email protected]. Very inexpensive and functional. The gas tubing is tygothane from McMaster Carr. But for convenience, I carry this too. Much less expensive than the yellow stuff and stays flexible inside the tank and out.

I had been running a 240 ml tank previously and it gave around 12 minutes of run time, not quite enough for 2 Masters schedules back to back. Also used a 550 ml tank and that allowed 25 minutes flying which made my flying buds b..i..t..ch too much.....LOL! Electrics...Bah Humbug!!

Note the hole in the firewall. That helps equalize pressure for the carb so no carb issues are encountered. The firewall is standard 1/4" cross grained balsa laminated with carbon cloth on both sides. This has been covered extensively before so I won't go into any detail. Plenty strong and super lightweight.

RE: OS 33GT Gasoline Engine for Pattern
 

Mike Muller wanted to know how I fasten my pants and axles on the landing gear so here's another short pic-tutorial. Maybe this one needs its own thread but.....

I make the pants and gear struts so customizing is no big deal. The aluminum threaded nut hard points are installed during pants lay-up on top of the carbon cloth reinforcement. Alignment is done in the mold. If anyone wants pants done this way it is straight forward to do on commercial pants too. If you want me to make them, they are not cheap!

I glue the pants onto the struts. Some noob was saying never to do that....well sorry to disappoint but this works better than anything else available and is super light. Been doing it for at least 10 years this way. Anyway, I'll let the pictures talk

EDIT*** note how the spinner is mated to the nose of the plane. I leave clearance here on purpose to allow some cooling ram air. My reasoning is simple: this air in the immediate vicinity of the spinner cone is some of the most disturbed, swirling air on the plane. I let it enter the engine compartment to help carry some of the heat of the crankcase eventho the crankcase is cooler than the cylinder. It helps

RE: OS 33GT Gasoline Engine for Pattern
 

The axles are 8-32 aircraft grade aluminum bolts. They work fine on an 11 pounder but remember that my struts are designed to be strong but springy. They take most of the landing abuse so the axles don't have to. Springy struts also transfer lower loads into the airframe.

BTW- in case you're wondring how heavy this whole set-up is, the RTF weight of the whole landing gear is less than 5 ounces. Also, the technique I've devised for mounting thegear is very light adding just about another ounce to the the whole gear set-up in a plane. Look that up in my Derivative thread if interested

RE: OS 33GT Gasoline Engine for Pattern
 

what is the tan colored material on the back side of the nose ring, shown in the pic on post #307?

thanks
tony

RE: OS 33GT Gasoline Engine for Pattern
 

Post 305...rubber

RE: OS 33GT Gasoline Engine for Pattern
 

MTK, I love what your doing here, I'm all for the idea of finding a gasser with performance/delivery that we're after.
The only thing that causes concern is the nose ring/hal senor problems and it's great to see you're making progress.
Still, the cut out for the sensor and the critical positioning of the nose ring due to the sensor mount still doesn't look like the optimal solution.
Couldn't help thinking that if you have access to a machine shop, why not try doing something like I've illustrated.
A smooth round machined collar thats bolted to the crank case encapturing the sensor/mount and providing a solid base for a traditional, albeit larger nose ring.
The width of the collar allowing plenty of flexibility for engine movement.
Of course I've draw it solid to explain the point... but it could be skeletonised thus saving weight, not to mention making it rather pretty.
And F3A guys love those pretty bits!
Keep up the good work and call me when you've machined a few. I'll have one.

RE: OS 33GT Gasoline Engine for Pattern
 

David, thanks, I think....

Actually, the real sensing element is far smaller than the housing. The real sensor can be glued to the crankcase and reduce the footprint substantially. But it's too much fussing and not really necessary......

Yes that was the original device I came up with also and in reality, if it surrounded only the sensor element, would be far smaller. I spoke to Todd Syssa about making a few of them but that never materialized.

I've considered getting a combo lathe set-up but that's not in the cards right now.....I don't have easy access to a machining center so I dropped it for something I could build at home with hand tools. Indeed my sub-ring was "skeletonised". Weight would have been around 7 grams or so, if built from ally. I haven't completely discarded the idea of making a mold for plastic parts. It's on a back burner

BTW- the nose ring design I show is not a prototype. It is a fully functional device that has seen service in several airplanes and 6 different engines in 3 years of flying, (lessee, 2 SAP180's. a DLE55, a Mintor 38, a ZDZ40, the current OS33 and will soon see service on the PTE36) some 30 gallons of gasoline and some 150 hours of service. It works great! Try it......

RE: OS 33GT Gasoline Engine for Pattern
 

So far, all 30-40cc engines I've played with with tuned exhaust display a significant boost in power (a jump in rpm) at around 4k rpm. For the OS33 the boost is there but seems a little softer, broader than the SAP's boost for example, probably due to more conservative exhaust timing.

Dean P and I worked on that yesterday. Dean suggested that I restrict the exhaust stinger of the pipe to help reduce or broaden the pipe boost transition. I installed a simple tie wrap on the exhaust tube (5/8" silicone rubber tube) restricting the exhaust down to about 5/16". The boost was still there but it seemed a bit softer, broader in transition rpm to me. Another beneficial thing was noise reduction. I also richened both needles slightly, about the width of screwdriver blade, but that much richening was too much. I will return the needles where they were.

The prop, 20x10.5 PN apc could use some tweeking to pitch. Dean thought it tended to rip a little and could use higher pitch. I will twist the prop to get another inch of pitch on it. Should help load the engine down some more and hopefully will clean up transition some more. And should help reduce ripping and further reduce noise....R&D continues.......

RE: OS 33GT Gasoline Engine for Pattern
 

The OS 33GT looks great, can we fly the masters sequence with ease with this engine? in comparison to the electric power or YS.

RE: OS 33GT Gasoline Engine for Pattern
 

Hifly, considering that the guys running the YS170-175 run the same props as I am, I'd have to say the OS33 puts out a little more HP than the YS's do. The extra HP however, is not required or necessary to fly F3A or masters.

The OS has very useful low end grunt just the same as the YS does, which has been an eye opener to me. I used to think no 2 stroke gas engine in this size could compete or compare to the low end of the YS 4 cycle. The OS has made that thinking obsolete. The fuel is avgas 100LL, but premium autogas works the same with a slight increase in power at the top, power which is completely unecessary for any schedule we fly. I opt for avgas because it is stable over time and doesn't stink... Avgas is purchased at any airport, usually around 2$ higher than autogas per gallon

I don't throw accolades like "impressive" or "stump puller" trippingly off the tongue; this engine simply delivers!!

You're here in NY....Do I know you? You might want to take a drive down and see for yourself

RE: OS 33GT Gasoline Engine for Pattern
 

Iflew Matt's Aesthesis this past Saturday with the OS 33GT. It's a little overweight, butthe OS has plenty of beans to spare to haul it through the Masters.It was a good power day, but I've seen Matt fly it on hot muggy days and there's no issue with power in those conditions either. Like any piped 2C, it has that extra bump in power when it gets on the pipe, but as Matt mentions, he's working on ways to soften that. It's not a sharp jump in power andis manageable, but would be a nicer throttle response in the lower 1/3 to 1/2 throttle range if the softening experiements work out. Iexpect that Matt will get the improvements he's looking for.

RE: OS 33GT Gasoline Engine for Pattern
 

can you lengthen the header to smooth out the tranistion?

understanding of course you will lose a little top end as a sacrifice.

tony

RE: OS 33GT Gasoline Engine for Pattern
 

Not forCD ignition. Glow responds to such pipe changes but gas doesn't. . Even stretched 3" there is no difference in engine performance. Stretching any more than that becomes impractical

RE: OS 33GT Gasoline Engine for Pattern
 

Would an ignition controlled by the transmitter be useful here? The ignition curve would be programmed in the transmitter. Simple with modern radios. It would seem the close ties between OS and Futaba would make this easy.

I wonder if OS has any pattern aspirations at all. A 44GT rear exhaust would be interesting.

RE: OS 33GT Gasoline Engine for Pattern
 

Just wondering how can the ignition curve be controlled by the tx? The ignition box is programmed to do this electronically.

RE: OS 33GT Gasoline Engine for Pattern
 

MTK,

Take alook at the figure enclosed, it is probably the "B" in the figure that you donot have., and hence have a "jumpy" pipe.
Regards

RE: OS 33GT Gasoline Engine for Pattern
 

Dag,

I'm not sure I see what "B" is referring to.

The "jump" of the ESC carbon pipe is very small and manageable on the OS33. It sounds like the engine clears its throat. In comparison, the jump on pipe of the SAP30cc that I was using last year was fairly large. I suspect it has more to do with exhaust timing....the SAP's was around 170 degrees and the OS's is around 150. We may need something even more milder timed than 150 degrees for smoother all around handling, but it is quite smooth enough now for general flying and competitive flying....

Maybe a tuned pipe isn't the correct exhaust system. Maybe something like a Bolly muffler would help. There's more than enough power so sacrificing a little isn't a big deal.....