OS GT15HZ 600 + OS Trex 600 Conversion... First Impressions

[LoveToFly1]

Originally Posted by Dylanss180

I was thinking of making a muffler out of titanium. But I would need a tuned pipe to measure in order to make a new one.

The beauty of making it out of 6AL4V titanium is if you get in a crash the material will not dent or break. Unfortunately it is really hard to work with. But, I might give it a shot if the opportunity arises.

order a tuned pipe from Todd at QD, setup for a heli. get your measurements, and sell me the tuned pipe for a big discount (since its not brand new anymore) and then you can make one!

jk....you can order the tuned pipe in pieces before its welded though, and you can get your measurements that way.....

or I can take detailed notes on my tuned pipe and send them to you.....does that type of material retain heat and stay good and hot? or does it disperse heat very well? it will need to keep a fair amount of heat in it for it to work properly. the air and soundwaves change with the heat.

[Dylanss180]

Originally Posted by LoveToFly1

order a tuned pipe from Todd at QD, setup for a heli. get your measurements, and sell me the tuned pipe for a big discount (since its not brand new anymore) and then you can make one!

jk....you can order the tuned pipe in pieces before its welded though, and you can get your measurements that way.....

or I can take detailed notes on my tuned pipe and send them to you.....does that type of material retain heat and stay good and hot? or does it disperse heat very well? it will need to keep a fair amount of heat in it for it to work properly. the air and soundwaves change with the heat.

I could take detailed dimensions and from there I can figure out if I can make one out of titanium.

The thermal heat conductivity of steel is around 35 Btu/(hr oF ft)
The thermal heat conductivity of Titanium is around 46 Btu/(hr oF ft)
So, it would dissipate heat faster than steel. I don't know if that is good or bad.
I guess if you really wanted to you could add a little weight to the system and insulate it.

Let me know what you think.

[Sowa]

Originally Posted by LoveToFly1

Most TUNED pipes are made from steel. steel doesn't absorb any of the sound waves, thus working much better and more efficient than a softer material like aluminum.

Do you have actual data for this statement? My biggest concern with this is the lack of data to back it up. I have yet to see a steel vs aluminum vs carbon comparison of the same exact pipe geometry. What I'd like to see even more is data with each pipe optimized for the base material as well. I get the feeling a lot of the info out there is speculation.

I don't have any data claiming carbon pipes work better than steel so I can't say for sure as well. Just from my knowledge of composites and talking to those who manufacturer composite pipes I think a carbon pipe can perform just as well as a metal pipe with much less weight. Only testing my theory in reality will be the sure fire way to find out.

Originally Posted by Dylanss180

So, it would dissipate heat faster than steel. I don't know if that is good or bad.

I don't think the rate of dissipation matters as long as the internal temp of the pipe stays constant. That is one of the advantages of carbon over aluminum is that the internal temp is much more consistent throughout the flight.

[Dylanss180]

Originally Posted by mitsudriver274

I don't have any data claiming carbon pipes work better than steel so I can't say for sure as well. Just from my knowledge of composites and talking to those who manufacturer composite pipes I think a carbon pipe can perform just as well as a metal pipe with much less weight. Only testing my theory in reality will be the sure fire way to find out.

.

mitsudriver,
I am no expert when it comes to exhaust so forgive my ignorance. But, I don't think you can make exhaust out of carbon fiber. The temperatures are too hot for the enamel matrix to hold. Most high performance exhausts are made out of titanium and the only carbon fiber you will find on it is the outer lining on the muffler because of the lower temperatures.

You could make an exhaust pipe out of pure carbon. We use that stuff all the time at work in excess of 2200 degrees Fahrenheit. The only drawback is it is as brittle as hell. The vibrations alone will break it apart.

As for temperatures and materials needed to make it perform I don't have a clue. Hopefully someone with some experience can chime in.

I think it would be neat to try to make one out of titanium just for the cool factor. You can do some trick oxidizing colors on it and make it look real badass.

[Sowa]

This guy's whole business is carbon pipes. Link

They have really good reviews in the planker world. I have been talking with Ed from escomposites about potentially using his existing molds for a gt15hz pipe, however a new mold is roughly $2k that would put a halt to the project in a hurry.

Given the displacement, he thinks he may have something that will work. I need to figure out the timing which means I will most likely have to pick up a spare sleeve to trace, and get my servo issues figured out so I can pick a rpm range to target for the pipe.

Like I said earlier though, I feel packaging will be the main issue.

[LoveToFly1]

Originally Posted by mitsudriver274

Do you have actual data for this statement? My biggest concern with this is the lack of data to back it up. I have yet to see a steel vs aluminum vs carbon comparison of the same exact pipe geometry. What I'd like to see even more is data with each pipe optimized for the base material as well. I get the feeling a lot of the info out there is speculation.

all I am going on is what I have learned through lengthy discussions with Todd from quickdraw. they make the quckdraw tuned pipe. according to him they have tried various materials, and stuck with steel for the reasons that I have mentioned in my previous posts. other than that though, no I don't have any data. but remember, what works on paper doesn't always work IRL the way it does on paper.....I run into that all the time here at work.

[Sowa]

I completely agree with you, that's why I want to test out a carbon pipe.

Remember though, Todd at Quickdraw is limited to the materials being used on his tuned pipes based off his manufacturing method. The ideal aluminum alloy for a pipe would be 7075 but I'm sure because the sections were welded together this could not be used. 6061 is a much softer material. So that is probably one of the reasons steel was chosen in the end.

[LoveToFly1]

ok, see, I have no idea what you guys are talking about now...lol! I know aluminum as aluminum, and steel the same thing. I don't know anything about the alloys and things. maybe something like that could be made to work very well then.

[Sowa]

I'm not an expert on the matter either.

In the process of doing all the calculations, for the geometry of the pipe, waiting on my RC crankshaft degree wheel. Hopefully Ed and I will be able to come up with something. I'll keep you guys posted.

[TODDC]

Aluminum will kill some power due to the heat releasing off of the aluminum. Yes it is lighter but does not work as well. The boat guys have found once the exhaust note changes from a loud tone to a dull sound out the pipe it is no good anymore. Bolt a new aluminum body on and noisy again and power back. The carbon pipes were tried before in the boats. The resin gave it up because of the heat. There may be better stuff though too nowadays? Headers run between 1000 to 1200 degrees normally at the headers when loaded. Not saying it will not work but alot of gas airplanes are usually running like 8500 rpm or so. Alky fuel setups will be even lower due to amount of fuel going through it and the temps. The hotter you can keep the exhaust the better.

Dylanss180 Titanium pipes were made by a place in the boating area but were rare and cost a lot. Being stronger is not always a good idea either. You take a hard enough crash and it may not dent the pipe but the tradeoff could be broken cylinder casting at the bolt holes from all the stress going there looking for the next weaker link.

[Sowa]

Exhaust findings:

Crank degree wheel showed up, got to nerd out with a new tool. Talking to Ed from escomposites he was also worried about the resin holding up. Because the header pipe is much shorter and the motors do run at a higher rpm at full power when compared to planks. This maybe a hurdle to jump over if testing proves this true. I'm also talking to my old composites professor from wwu about different resins as well as coatings. Looking into what's feasible in regards to cost.

Hopefully the tuned pipe experts can chime in on my maths as they seem incorrect to me. And to the guys who actually manufacture pipes, please take this info to develop your own pipe! I'd love to see something come out of this, whether it's my own or not. I measured the exhaust opening multiple times, for some reason I was expecting a much longer open period, but I swear it's correct.

Formula I used:
L = (V×E)/(N)

Exhaust open period = 154 degrees** = 2.8780 rad (E)
Wave speed = 1700 ft/sec** = 518 m/s (V)
Engine speed = 15500 rpm** = 1632 rad/s (N)

L=33.6 in

That seems very long to me, but I'm still learning.

Edit: I have found a off the shelf tuned pipe system from macspro.com, David has recommended using his 15 cc pipe (p/n 1403) with either the 5983 or 5984 header.

** Edit: Did some more reading these are the correct units for this equation. No need for converting, for some reason I thought I needed to. That gives a tuned length of 16.89 Inches, sounds better.

For anyone that cares, I weighed the Hatori exhaust system, comes in at 247 grams.


Engine inspection (1 gallon in):

Looking inside the exhaust port, I see no scratches or signs of overheating, the sleeve looks really good actually. Looks like it's running pretty rich as I see a lot of carbon deposits. I picked at the side of the piston and it just flaked off exposing clean aluminum. One thing I didn't like was the wear seen at TDC. I haven't seen enough two strokes but I feel this is abnormal, most likely due to the large tolerance at ambient temperature. It's hard to capture engine wear in photos but I tried my best.

Stock high speed needle setting is 2.5-3 turns out, I'm still running running 3 clicks rich from 3 out. I did notice some oil build up, I think it's from raw fuel coming from the carb, as the inside of the fan shroud has residue from the end of the carb track down.

Motor doesn't sound lean, telemetry temp is reading around 310F at the top of the head opposite to the exhaust port. I usually read a two fins down from the top of the cylinder, but this cannot be done because of the Hatori exhaust. I'm not to worried about the temps and only refer to them after multiple gallons to really get an understanding of how the temp is related to the tune. OS states an operating temp around 266F.

[LoveToFly1]

yea, my Zenoah engines operate at around that 260F temp too with a standard muffler or a modified muffler. with the tuned pipe, I can see much higher temps without damage though.

[Sowa]

Out if curiosity in what location do you measure temp on your engines?

[Steve Bae]

I bought GT15HZ600 power boost combo set & conversion kit from RC JAPAN three months ago.
Unfortunately I replaced pistons and clinders, rings, retainers two times due to one piston pin retainer fell out.
New retainer part 28117020 also has same issue.
I guess this engine has serious overheating and retainer fell out issue.
I gave up this engine, and got zenoah engine.

[Sowa]

That's unfortunate to hear. Did you contact OS about your issues or replace the parts yourself? I also had the wrist pin retainer fall out once in this engine, luckily OS stood behind their product and warrantied the engine. It's been running strong for over a gallon now, however time will tell how truly reliable this engine is. But some have over 10 gallons through their 15HZ with no issues, which is keeping me hopeful.

Where was your main needle set when this happened? How long into your flights did this happen both times? I still don't understand fully how these motors are throwing retainers. But it does seem like the last piece to make them reliable.

My hypothesis is that the piston hits a frequency that happens to be the natural frequency of the wrist pin retainer which causes it to work it's way out. It also always seems to be the retainer on the inspection plug side. If this happens to me again I will try and hunt down a spiral retainer.

[Don White]

What was the indication that the wrist pin retainer came loose? Did the motor lock up or some thing else? I'm flying the same conversion. 3 Tanks so far.

[Sowa]

When the wrist pin retainer falls out it destroys the internals. The biggest indication is a loss of compression. I found bits and pieces of the retainer everywhere in my engine.

From what I've read on here and my experience the retainer that falls out is on the inspection plug side. So if your in doubt you can pull the inspection plug and see how the retainer is sitting.

What I would like to gather is at what point in the flight is the retainer falling out. Mine fell out within 2 min of taking off. The engine was not at operating temp when this happened.

Steve, if you have moved to a Zenoah, I would like to purchase your grenaded gt15hz.

[joecass2]

I also had the retainer fall out 2 times both times doring brake in. I just got it back from OS of japan and I ran my fist tank yesterday. I hop I can make it past brake in. I would really like to see how much power it has. For me it seemed like when I started to increes head speed that is when it poped off both times. The one on inspection plug side. If it happens again I'm going to try the OS 91 retainers

[Sowa]

Joe how far into the flight were you when it happened to you?

Also at what headspeed did you encounter the retainer falling out.

[Steve Bae]

Originally Posted by mitsudriver274

That's unfortunate to hear. Did you contact OS about your issues or replace the parts yourself? I also had the wrist pin retainer fall out once in this engine, luckily OS stood behind their product and warrantied the engine. It's been running strong for over a gallon now, however time will tell how truly reliable this engine is. But some have over 10 gallons through their 15HZ with no issues, which is keeping me hopeful.

Where was your main needle set when this happened? How long into your flights did this happen both times? I still don't understand fully how these motors are throwing retainers. But it does seem like the last piece to make them reliable.

My hypothesis is that the piston hits a frequency that happens to be the natural frequency of the wrist pin retainer which causes it to work it's way out. It also always seems to be the retainer on the inspection plug side. If this happens to me again I will try and hunt down a spiral retainer.

I ordered these parts from RCJAPAN,
The price of ordering these parts and international shipment are almost same.
So I ordered and replaced them alone .

Actually the other two guys bought and built their own trex600n GAS conversion kit with GT15HZ600 togather. they also had experience this issue after 4~6 tank flight with rich mode (3+1/4 open) and less than 1900 rpm head speed.
Tried oils are Motul 2T offload & AMSoil saber 100.
Now they all gave up this engine after two times of replacement of these parts.
They have been good memory with long experience of OS nitro engine. but now it is not from this engine.