rm

My Feedback: (27)

I bought another motor and have 78 flights on it now. Approaching 6 gallons. Running redline now at 40:1.

Have it at the St Clairsville contest this weekend thanks to Mark Hunt getting me the templates to be able to make another canopy after losing my original in the corn field.

Started running the apc 21x10 wpn this week. Turned 6700 when I tached it. That's on a 29" pipe. Planes not super fast but pulls like a mule and doesn't stop. Originally bought this prop to try on my YS 175 which turned it at 6300 the only time I ever tached it.

Bob Kane had a radio shack db meter with him, so we took it out and ran it up and got a reading of 93db over grass. Engine is hard mounted on a balsa, ply, foam airframe. I realize this isn't the most accurate meter in the world but it does offer some encouragement. We have the D4 year end meet at Muncie end of September and we're going to try and get the same sound meter used at the nats and get a good reading. Will try the 20.5x10 also. I did the sound testing for masters at this years nats, so I have a pretty good idea how this will compare to the other setups.

The sound factor has always been in the back of my mind. If it couldn't be used at the nats without penalty, then it wouldn't be overly useful to me as I like to fly there every once in a while. If it's successful, I can't think of any other argument that gas power isn't a realistic alternative for competition. Biggest problem would be finding an airframe.

MTK

RM,

The engine turns the 21x10 wpn okay. It is a little happier with the 20.5x10. On my set-up I get just about 7K using avgas. Premium gas will get another 2-300 rpm which is totally unnecessary. The extra 2 1/2 mm of stroke (compared to all other 30-35cc engines) gets you a lot of torque. The engine puts out similar power to the 185. And neither engine needs to run at full revs....ever....for any maneuver.

A soft mount will drive the sound down to around 90-91. The balsa/ply plane is the quietest test bed for IC

The larger disc area of the 21" should produce n even slower downline. The 20.5" results in quite the slow line though.

YS throttle response is a little better than the run of the mill Walbro throttle. Wish OS would develop a better carb for the 33. They did for their 15. But I doubt that will happen anytime soon. Just not the money in IC engines for Pattern to warrant the R&D. Unless OS wanted to go head to head with YS 4 strokes which won't happen. It's taken YS decades to get the throttle system they now have.

At the end of the day, the GT33 is a great sport engine adapted to Pattern. It's inexpensive to own and operate and gas just doesn't need bearings every 100 flights or rebuilds every 400 flights. The fact that it is pretty close to par with the thoroughbred YS is either genius or dumb luck. Had it come out in 2000 when the 140RX was all the rage it's simplicity alone would have bypassed everything else.

airraptor

My Feedback: (66)

if the 33 came in out in 2000 it may not have lasted a year lol as glow was very cheap then and the electric stuff was moving very slowly.

MTK

Spoken like a guy who didn't fly glow back then.

drac1

My Feedback: (4)

It's cheaper to run glow now than back in 2000.

MTK

How do you figger that one? Are you mixing your own? Come to think of it I think that's true.

Regardless, gas engines truly sip fuel where even 2stroke glow guzzles in comparison. 4 strokes well forget about fuel consumption

flywilly

My Feedback: (121)

Hey Matt,
I am a diehard glow guy (since my first Cox Pee Wee .020 back in 1967 when I was 10), but the OS gas engines seem very well engineered and I have been considering one. I remember back in the '80s when the TOC models started getting much bigger that many were powered with gas engines converted to methanol. Would that be feasible with the OS GT 33?
Thanks,
Will

drac1

My Feedback: (4)

Easy. Because my running costs are cheaper now than 15 years ago.
I'm not sayng it's cheaper than gas.

My YS 185's use around 250cc's per flight. And yes, I mix my own.

MTK

Will,

I have not done that so I don't know for certain, however it's been discussed. I don't see why it wouldn't work. You probably need a smaller venturi Walbro carb intended for glow fuel which is probably available. You should be able to run a standard OSF, KB1L or YSF glow plug and a regular glow pipe. It would be a lighter set-up possibly as much as 7 ounces (no CDI and shorter exhaust)

The major thing about methanol tho is corrosion. This particular engine develops more power than necessary on plain gasoline. No corrosion at all for years now; and zero maintenance (no 1 has about 130 hours of operation over the past 5 years). But if you read RM's tribulations, it's not bullet proof.

flywilly

My Feedback: (121)

Thanks Matt. No engine is bullet proof, but gas/glow 2-strokes come close. I've had good luck with YS 4-strokes, but don't push them as hard as some (15-20% nitro). The DZs are impressive pieces of machinery, but a lot has been written about their 'issues'. I have little interest in going electric, either.

MTK

Will, I forgot to mention that my early experience was also with the Cox 049's, 020's and one 010. The tiny mill was really something. Back in the day (maybe around '70 or so), I saw a Pitts bipe construction article in the old AAM so I decided to just use the drawing in the mag to make a tiny profile bipe for the 010, with about 16 foot lines. No handle, just looped the strings on my pinky and index fingers. Man did that little thing fly well but I had to be very careful with finger movement since it was very responsive. No need to move the wrist at all; just slight finger movement is all it took. Fully aerobatic, the little Pitts (about 10" span and maybe 3 ounces) was a hoot.

drac1

My Feedback: (4)

"issues"????? - Hmm, gives me a chuckle anyway.

flywilly

My Feedback: (121)

Hey Matt,
great story about the Pitts. I really enjoyed my 1/2a experiences with c/l and f/f, though the latter often involved tree climbing for retrieval, at least until I figured how to trim them effectively.

papaone

Hello

Friend of mine received (in France) carbon gasoline pipe from ES Composite
Awesome carbon building. It's ES 35G he wants to install in his Harmonie instead of alu pipe. Engine is RCGF 32, APC 19x11.
http://www.escomposites.com/prod01.htm

Do you think alu colar or ring (I don't know the right word) will damage the pipe ?
Any suggestions about fixation without damaging ?

Claude

MTK

Claude, the aluminum strap should not be placed directly on the carbon pipe. In the past, I have always protected my pipe by adding a layer of rubber directly where the aluminum would hold the pipe. This isn't elaborate....I used a short length, 20-25mm, of bicycle inner tube of about 1 1/2" OD. The diameter isn't critical. Just slide the rubber tube over the pipe.

My pipe mounting method now is much different and doesn't use straps; the carbon pipe doesn't require protection because the soft mounting is epoxied directly onto the pipe (I use regular epoxy, not high temperature). If you look back at some of my threads I show how this is done. I think I have it in my Derivative thread. It is more secure, far simpler, and much lighter way to soft mount the pipe.

papaone

Matt

Thank you for you quick answer.
I found the pic about Derivative carbon pipe.

Claude

MTK

Claude, you can see looking at the pipe how I epoxied some carbon roving around the pipe (at its CG) which locked in the nut that later would hold the Lord mount. The Lord isolator is simply screwed into the nut epoxied on the pipe. The pipe is carefully inserted into the belly of the model until the Lord screw hole is seen through the mounting hole in the fuse's belly.

The Lord isolator is secured to the airframe using a flat head screw from the outside of the model. The belly area is reinforced with a layer of 1/32" aircraft plywood to spread the load. Try it...it isn't tricky to set up and is so much more convenient to use. The main assumption is that the pipe length is known and will not be changed; if a change is wanted then some surgery will be required

Note also the bent orange coupler. This is the same coupler arrangement I have discussed before. It is custom molded using ceramic fabric and Permatex Ultra Copper sealant. Bends, dissimilar diameters, conical transitions, after mufflers, are all straight forward. Just need imagination

MTK

RM and all,

I had my first engine operational failure this week. This is what happened:

After priming, I flipped the prop with my chicken stick and it bumped except it backfired throwing the prop. Hmmmmm it has never done THAT.....

I quickly shut it off; I tightened the prop and restarted with the stick except it backfired again and started backwards. Ignition immediately off stopping the engine. As I turned the prop slowly by hand, I realized that something had gone terribly wrong since the engine had no compression. I dissembled the plane and went home.

I took the engine apart and saw score marks in the steel liner. The piston's top also had some evidence of shrapnel. I removed the access screw to the piston pin retainer clip and found no clip. AHA!!

I think that when the engine kicked back throwing the prop, the retainer clip popped off. It got caught on the piston skirt scoring the liner and ruining the piston. Compression gone! We are in the market for a new piston and liner. It could have been much worse of course.

After some 130 hours of operation, I suppose it was due for something to go. Problem is that when something metallic let's go, the piston and ring probably are toast.

rm

My Feedback: (27)

Hey Matt,
My 3rd one is frozen solid. Heard it make a clank sound and stop. I've pretty much had it with this motor. Haven't touched it since it happened, planes been sitting in the corner for a month. I'm eventually gonna send it to hobby services without touching it and be told how its my fault.

MTK

Yes it's a shame that Hobby Services seems to assume that we are all inexperienced sport pilots. Then again, the vast majority of claims are made by them so I can see HS response.

I am curious though if your retainer let go. The only disassembly needed for that is removal of the large aluminum port screw and inspecting the piston pin's end. Of course if the opposite retainer let go, you won't be able to tell unless you took the piston completely out. If it's frozen then piston removal is the only option and would be best if HS did the work since they have the right tools. Heating the case with a monokote heat gun will help with sleeve removal. It doesn't take a lot of heat; hot water warm is good enough (120-130 degrees)

I priced the piston, ring, liner and retainers and that's quite pricy even with the 20$ Super Saver discount. I guess I will keep the remaining parts as spares.

rm

My Feedback: (27)

I'll ck the retainer when I take it out. RCjapan would be half the cost, but shipping would prob run u around $30. Guy on FG reported same situation but got quite a few hours out of it before it happened.

MTK

Thanks for the RC Japan tip. The parts needed (piston, ring, liner, retainer clip) are about 7700 yen which is about 65$. Even if shipping was 30$, I'm still ahead by at least one third. That's significant cost savings. I also priced the Hatori header for the engine. That was an eye opener at less than 10 bucks (compare at 75$ from local source). Ordered that too.

Commissioned one of my spare engines but kept the ignition module. Engine fired right up; back in business and hope to fly today

"Edit" the actual shipping cost was 2190 yen to New Jersey ($18.50). Better than expected; I would use them again ....

MTK

The parts just arrived from Japan. Just over two weeks is pretty good from halfway around the world. All are genuine OS, in OS packaging. I bought the following:

Piston and ring
Liner
Circlips
Rear bearing
Back to center header from Hatori.

The approximate cost was 90 +18.50 for S+H. You can do the comparison to local sources.

Thanks again RM

big_G

Would be nice to know the root cause of failure.

drac1

My Feedback: (4)

I buy all my YS parts from RC Japan. Around 1/3 the price of Aus and US. They are actually 10-15% cheaper than YS direct.

5 days shipping from Japan to Australia.