MTK

No mill yet but am looking at a lathe-mill combo. Basic hand work

cmoulder

Matt, how is the Tygothane tubing holding up? Any downsides?

MTK

Bob,

It's been one whole year now and about 20 gallons gas through a few and various set-ups. Tygothane is still as good as new. No swelling, no crazing, no hardening, inside the tank or out. I also use it inside and outside on the main gasoline jug I use.... In contrast, the yellow Tygon for gasoline has been replaced a couple times in some areas. I have nearly eliminated the yellow stuff from my equipment.

Urethane is one of the toughest plastics we have....abrasion resistance is another strong suit. No downsides seen yet. As a matter of course, I tend to use either a small tie wrap or shrink tube to secure fitting ends

Neoprene from the LHS is no good at all eventhough it should be. The stock my LHS has, apparently was extruded without anti-oxidants. In 3 months the stuff crazed and eventually leaked around various barbed fittings.

Of course, Viton is the best of the best for our application but at about 4$ a foot, it's 10X the cost of Tygothane. Also, have not been able to find soft and flexible Viton (haven't looked very hard tho). I'd settle for thin walled to produce flexibiliity but the thinnest has been 1/16" wall and that's a bit too stiff. I've made a clunk line from Viton by grinding the wall with a dremmel sanding drum and it worked but it was a pita.

cmoulder

Matt,

Glad to hear that it is still working well.

I suspect that some varieties of Tygon were formulated more like Tygothane. This is because some of the "Tygon" I purchased later in my gasser experience held up well and remained flexible while the older stuff turned stiff in less than half a year and was very stiff in cold weather even when new. I'm sure I'm not the only one who crunched a nice model because of that crap.

choihjin

My Feedback: (1)

Successful maiden flight of Smaragd powered by OS GT33 gas engine on a Hyde mount with Hatori header and Canister: After rain, our runway was not good for maiden flight; but weather was OK, 10 deg C (50 deg F), 50% humidity and some wind. Honeycomb light wall isolate the canister muffler from electronics and gas tank, photo attached.
To make sure idle setup checked again; video attached: http://www.youtube.com/watch?v=ke2sO_nC30w . Starting engine by hand crank was not easy and several back-ward starting. But very reliable idling on around 1950 RPM with 18x10 prop, not much vibration on a Hyde mount, and glow-like sound with Hatori header and canister muffler. Highest RPM reached up to 7670, no vibration on Hyde mount.
After several safe flights, engine sound was slightly changed to crackling, and could not stop the engine even with fully closed throttle. One of two bolts tightening the muffler header was missing. Does it make sense even fully closed throttle? I think it might be, air can get into through exhaust outlet, it is my first experience.
On a test bed, all OS GT33 engine with stock pitts style muffler and a stock gasket was working fine. I think based on several threads, engines mounted on planes with canister mufflers with other gasket in my case, Starting engine was not easy and even backward starting. Wide opening of throttle, more than 50%, resulted in successful forward starting, but it is dangerous. The stock gasket was good to tight the stock muffler, it is melted to fit on the muffler, it is difficult for reuse. I hope to buy it from Towerhobbies, but not in the parts list. I need a good gasket again.
I will post a video on high speed running gas engine on Hyde mount later after fixing the exhaust header fitting.
Regards

speedracerntrixie

My Feedback: (29)

I stopped using gaskets on my gassers for this very reason. They just don't hold up. I started by making the header flange flat by sanding it with the paper on a plate of glass. Usually the welding process warps the flange. The engine side is usually OK unless your muffler/header has worked loose and ate through the gasket and was banging against the engine case. Make sure the surfaces are clean, I use acetone for this including the tapped holes. Put a thin layer of Permatex orange high temp RTV on both surfaces and bolt together with red locktite. The red locktite can be stubborn to remove so usually I will hit the screws with a 35 watt soldering gun to heat them up before trying to loosen them.


As for the backward starting, Usually it's because then engine is over primed. Perhaps with a different starting sequence. It's common to flip a gasser with the choke on until if pops and then floods out and quits. Maybe try to start by choking for a few flips short of popping and then try with the choke off. More run time, tuning and familiararity may just fix that one.

speedracerntrixie

My Feedback: (29)

Double post...........

MTK

I use Permatex Ultra Copper hi heat gasket sealant. A thin layer on the flange and in the holes. I have also used NordLoc washers under the bolts and that combination is solid. I've heard others use red Loctite but I have not.....Ultra Copper is the best material I've used so far and it seals and locks everything long term. Lost header bolts just don't happen anymore.....

I am really hoping that Hobby services comes through for me this week....

speedracerntrixie

My Feedback: (29)

I'm wondering why OS went from front intake on the 55 to rear reed induction on the 33? Any ideas?

David Bathe

I guess it's nothing more complex than size... or lack of it to accomodate the carb at the front.

PlaneKrazee

My Feedback: (14)

+1

Ultra Copper and no locktite, Nordlocks are great. Lubricate the threads to achieve proper torque on bolts.

If you can't find Nordlocks in small quantities, Micro fasteners sells Dyna-Locks ranging from M3- M6 and appear to be Nordlocks. Expensive at over $5.00 for 10 pair but still well worth the price. Install your muffler or header and it will not come loose until you remove it.

airborne2.4

Yep, Permatex Ultra copper hi heat gasket sealant with Nordloc washers work

choihjin

My Feedback: (1)

Thanks a lot for informations

Permatex Ultra Copper hi heat gasket sealant (101BR) is available here, but I can not find the Nordlocks.

A similar shape washer, HEICO WEDGE LOCK WASHER is available. Is it a same kind washer?

And how can a video file be posted in RCU?

Regards

PlaneKrazee

My Feedback: (14)

Post the video to youtube and post a link to it here.

airborne2.4

A video of how Nord-Lock washers are the best way to prevent loosening. http://www.youtube.com/watch?v=mgwmuZuJ02I

I got mine from these guys: http://www.fastenal.com/web/search/p...Z1z13zy4&Nty=0

MTK

I suspect it has to do with reducing the crankcase volume.....one way to pack the case a bit more than the rotary valve (of front induction) would allow. This can improve power output if the porting is right.

There may be a weight advantage also. Crankshafts don't need to be as massive when there is no hole to provide strength for.

About the only down sides of a reed set-up is reed float at high rpm and lack of intake timing control. I suppose reeds are noisy so that's another down side for a Pattern application, but that's easier to control. At the rpm we operate, reeds are an excellent, simple solution. And fitting a 3 blader up front helps reduce noise a lot

Choihjin, I get my NordLocks from McMaster Carr. The M5 size comes in two outside diameters....I buy the smaller OD. If you decide to buy from them, you can get the Ultra Copper there too

MTK

Contacted Hobbyservices today and my engine apparently was run at their shop. The guy said it ran fine....Why don't I believe that?

The guy also said that one of the mounting lugs was broken in shipping. The rear plate has to come from Japan so I'm probably looking at another 4-6 week wait over the 3+ weeks already

I am very disappointed in this whole ordeal

jgg215

So they ran the engine with a broken mounting lug? hmmm

DagTheElder

Hi,

Take a good look at the figures attached. Look for the duration of induction of air in the two exsamples.The more air the more fuel can be burned resulting in more power.

This may be a good reason for rear induction.

Best regards

PlaneKrazee

My Feedback: (14)

Matt,

I'm very sorry to hear this. Hopefully when you get it back it will run properly. Personally I'd run it inverted with the stock muffler first to see if it does run then connect the pipe and see if it still starts and runs.

tele1974

Doesn't sound good at all.

MTK

Just spoke to them again today. Still no backplate from Japan.

I asked the guy how they could run an obviously damaged engine (they told me they received the engine with the cracked backplate from shipping damage) and particularly one with a broken backplate, and could hardly believe my ears....the guy again stated that it was run twice and it ran well. Didn't answer the question

Apparently a starter was used to get it going. The next thing was they wanted me to buy a 100$ heavy duty starter and another 80-100$ for lipos and charger to run that. And BTW, Tower has these parts in stock.These fools are unreal!! Never again

Bax

My Feedback: (11)

A note:

The rear cover needed is out of stock. It is cracked, but the engine can be mounted and run. We don't have engines in stock, or we'd take one out of stock and get the part. We've been assured that one is coming from O.S., in Japan.

We have successfully run the engine twice. It runs normally and very, very well.

Please note that the instructions for the engine do state that it is intended to be started with an electric starter. Please see the last paragraph of page 16 in the instruction manual. The engine can be hand-started, but you must get it really flipping fast, because the engine does need to have the prop hub moving fast enough to excite the sensor. It's not surprising that hand-starting could be difficult because of this.

MTK

The first 4 starts I made were hand starts, 2 on the bench and 2 for flights. No issue with the first 4 runs....I have no electric starter and don't intend to buy one. My flips are faster than the minimum rpm required (> 100 rpm per the manual)

Problems started immediately afterward. It wouldn't even pop when hand cranking and I used 2 other CDI units other than the OS, which have no extra software regarding minimum rpm.

Look....I am very intrigued by the engine's power that's why I have not chalked this 420$ up to experience. I truly hope it runs as well as you claim and does so reliably for 1000's of runs. I intend to run the engine in pattern applications (piped) so relaibility is an absolute. And as much as I practice every year, I don't want these unexpected sidetracks

speedracerntrixie

My Feedback: (29)

Bill, I have a few questions/comments. While I am not the owner of this engine and have no real business getting involved other then being a consumer whom at some point may consider buying an OS gas burner in the near future. I do have 2 50cc airplanes under construction now and the OS 55 was a consideration.

First off, I am curious as to why you have taken the time to run the engine twice knowing that you will have to split the case to make repairs. Obviously you will have to run the engine again after this work is complete. To me it just seems like a waste of time setting it up on the bench multiple times.

The other thing is the use of a starter. IMO the market you are trying to reach with this engine is used to hand starting engines. This alone is enough to make me skip over the OS offerings as I will not buy an engine that can't be easily hand started. OS could easily fix this via ignition timing ( Adjust the ignition firmware ), port timing or both. Obviously I'm not sure of which one or both that prevent hand starting. Having to turn over the engine fast has nothing to do with the sensor. What I think is going on is that OShas programmed the IC that controls the ignition not to trigger the coil until a certain RPM is reached. They most likely did this to prevent accidental starts. It's a simple fix, edit the firmware. Again IMO Great Planes, Hobbico and any US based hobby supplier needs to be more focused on customer service, especially now with all the available stuff outside the US. There are still lots of us that will spend the extra money on quality products as long as the customer service is up to par.