MTK

I am finally ready to re-install the engine in my pattern plane. Took a week or so to get my workshop in a better state so I can start to build in some comfort...

So many side projects, so little time..... I'll have some numbers this week IF THE SUCKER STARTS and runs properly

labebe

Fellows, I have an OS gt 33. I need to buy a pitts style muffler, where can I find it??? or do you know another muffler brand that can easily fit ??????
Alex

airborne2.4

Wow, pplleeeaassseeee don't tell me OS missed this step.

labebe

yes they do, but Jtec said that the DLE 30 exhaust is the same , so mufflers for that engine will fit the os gt 33

PlaneKrazee

My Feedback: (14)

The engine comes with an engineered quiet pitts style muffler. Why do you need to buy one?

labebe

It is real nice and Wrap around, it doesn't fit between the firewall and the rear carb, it is bulky, I need a smaller one or a side inverted muffler type

MTK

The engine comes with a large muffler. From some accounts, it is apparently quiet enough.

But in this pattern forum we discuss tuned pipes for the most part. I doubt many will use the included muffler for pattern planes....could be a bit too bulky to fit the front end of most pattern types.

Talking tuned silencers, I just purchased a tuned exhaust (header and pipe) for the Mintor 38 cc from Area 51. The price was terrific so I couldn't pass it up. This same pipe will work fine on the 33GT. The header will not since it is the 4 bolt type intended for the Mintor. The pipe is only 1 ounce heavier than the ESComposites and is aluminum. The reflector ring is located at the same place as that of the ESComp......

MTK

Finally got to install the 33GT in Temptress last night. Took three flips and she was running. That's good news! The needle settings that came from Hobbyservices were way off so it needs tuning but the fact that it started right away is good.

We should have nice temps Saturday. If we also have moderate winds, I will fly it this weekend....Wish me luck

cmoulder

Congrats, Matt. Hope it keeps running well this time.

How many different engines have you installed in the nose of Temptress?[8D]

MTK

Hmmm, lessee
webra 145, webra 160, os 140, mintor 170, moki 180, sap180, and os 33gt.

Temptress has been a true friend and a workhorse but she will retire after this series of testing. She deserves it after close to 2000 flights and 8 full seasons. She managed to keep the weight off after a couple mishaps in that time. Debut'd her in 2003 and flew her in 2003 and 2004 Nats.

PlaneKrazee

My Feedback: (14)

Matt, You are at a slightly different elevation and running a tuned pipe. Your needle settings will be different than running the stock muffler. If for some reason your tuned pipe setup isn't timed right it will be stuffing exhaust back in and will run lean and over heat. Could be header length, convergent cone location, stinger length etc. Different engine exhaust port timing requires different pipe timing as does going from glow to gas. Heat and flame spread also effect tuned systems.

Too bad you don't run it with the factory tested exhaust to simply see how it acts, could be it doesn't like your setup. I had the OS 160FX on a Jett incowl turbo muffler. Gained 1000 rpm on a Bolly 18X10 carbon but never landed with the engine running. Tried richening the high, the richening the low, leaning the low and all possible combinations. Ran great on the ground but would either blow the plug (lean) or just quit in the air. The engine had baffles all around it and 1 to 4 air in to out. Ran perfect on both a Jtec Dual snuffler and a Bisson ST4500 pitts.

Of course if it runs fine now that it's back, Hobby Services fixed something but the world may never know. If it tunes like the 160fx it will never run correctly if the low needle is lean.

choihjin

My Feedback: (1)

Congratulations, MATT K

Hoping you get some good weather in this weekend to hear a good news.

Regards

MTK

Flew one flight today. However my arm almost fell off flipping the damned thing....I am undergoing a definite learning curve on the care and feeding of this beastie, just like I did the SAP 180 almost 3 years ago.

Weird thing is, with my particular engine, there is no real warning...the engine doesn't pop or burp or nothing, it seems. Just decides to get going at some point after 100 flips. At home, on the bench, it started easily

I am going to get a heavy duty starter after all....

The pipe is an ESComposites 40G. Header is Hatori with an extension; distance to reflector from exhaust flange is 28". Prop is 18x12 MDK Hybrid, not apc, It is a wood/carbon composite that I make. RPM's not sure but by ear I think around 8K. The plane is around 10 1/2#. I had the SAP30cc in it before and it struggled on this prop...just too much for it. Lower rpm and couldn't pull a vertical without bogging down. The OS33GT is turning this same prop very well, putting out very useful power for the kind of flying (Masters Pattern) that I do.

But I'll see how it behaves later in the spring in warmer temp and higher humidity and after full break-in. Today it was 54F (fantastic for January) and low humidity.

speedracerntrixie

My Feedback: (29)

Matt, I was just looking at where the crankcase pulse comes from for the carb. Appears to be the back plate. Maybe after the ring seats it will give a better pulse and the carb will prime better. I wonder if anything can be done to increase the pulse?

kochj

Matt
If it makes you feel any better.. You are not alone with engine woos...
DA170 on re3 pipes:
"I went out to practice with the Suk on Sunday and 3 minutes into the first flight the motor stopped on a down line, it did not feel right when turning it over by hand and when I pulled the motor yesterday and looking in the exhaust port I see the piston moving laterally in the cylinder about a 1 mm when slowly turning it over-it looks like a bearing is toast and maybe a ring is broke so off to DA it goes today. " The engine had 5-flights...
This wasn't my engine so I can' comment much more ..

Did you say, you had tried running the engine with other ignitions??
I guess the starter is the way to go with this one....

One good thing out of this is that when using a starter...you don't run the risk of wrecking the cowl with miss hits from you hand or chicken stick...
Perhaps though, when you get into the 20" size props there isn't a risk of this as much as when using smaller props in the 15-18" range!....

kochj

This guy was the originatior of the smart starter....even though someone else has make a kit for this...

http://www.youtube.com/watch?v=0q0q5...7fTZviTM7erYzP

MTK

Speedracer,

I changed the tube early on. They had a length of 3/32" yellow gas line as the pressure pulse line. As I was investigating, I saw that the tube was slightly pinched against a corner and had a definitely dimple. I changed to a length of 1/8" neoprene from McMasterCarr and moved the nipple a bit to eliminate the pinch point.

The 1/8" line doesn't change the pressure pulse to the carb. Pressure is unchanged (whatever the crankcase pressure is) but the larger hole in the tube allows a little more volume due to the increased cross section. But since it a static situation and the runner length is short (1"), I doubt it matters much.

MTK

EBay has a couple Dynatrons for sale. My neighbor just picked one up for 40$. That would work fine for me

PlaneKrazee

My Feedback: (14)

Gee wizz Matt,

Sorry to hear it's still a bear to start. There must be something different between your bench and installed setup. Any ideas? Sounds like it won't pull prime with the choke closed. Maybe you could try soldering the hole in the choke plate shut.

What is your proceedure for priming? On my updraft twin I close choke, advance the throttle to full, rock the prop twenty times or so, check to make sure the choke plate is wet, then set the throttle to high idle, turn the ignition on with the choke closed, flip once and get a pop, open the choke and two flips it's running.

MTK

I wish it were that simple. I've used the rocking technique with the SAP30's and DLE55 with no problem....I've also used the "choke-full throttle-ignition on-and flip til it pops" technique with both engines and my ZDZ, Mintor and BME engines. All of these engines are simple to start with these techniques.

Not so with the 33GT. Anyway, the dynatron will be here Thursday. I hope to get a few more flights before it gets too cold. Saturday was a near perfect day but was largely lost due to lack of fire. I was just happy to get one flight in and ran the tank completely dry

PlaneKrazee

My Feedback: (14)

I never run the tank dry, always a wet diaphram and full fuel line ready to pull prime. In fact I store it with the tank 1/2-3/4 full. Same Tygon, three years old. I did buy some wiz bang Viton or something tubing (need to find the receipt, it is compatible with alcohol and gas) but haven't needed to change the clunk line yet. However the fill line is very stiff.

I forgot to ask what oil and oil ratio are you using? I've been very happy with the Stihl Ultra @ 40:1. Even 6 month old fuel mix worked fine. Must have stabilizers built in.

MTK

The dynatron arrived yesterday. A bit disappointed in it's performance in trying to turn over the OS with the 4 cell lipo I have on hand. I guess I need 6 cells minimum.

RC11

My Feedback: (7)

Matt,
I had a geared Magnum from from Hobby People and ran it on a 4 cell 2350. It cranked the SAP 180 with ease. I gave it to a friend who cranks his Moki 210.
Really compact and powerful.

Best to you,
RC

cmoulder

Matt, it's rated for up to 24 volts. However, it will start to get hot if you run it for more than about 10 seconds @ 24 volts. After about 5 or 6 10-second runs it will be quite hot.

Ridiculous that a gasser takes this much effort to start!

kochj

D