Nosedragger

We ran db meter tests at the feild and the short stacks are louder.

subarubrat

My Feedback: (1)

But again, we are talking about an engine that is closer to the electric spectrum than the glow or gas 2 stroke spectrum of noise. So what if it is 2db louder with short stacks? It is still quieter than a muffled .60 4 stroke.

What my edited retort was in reply to was the idea that it is some deafening valve burning monster that assaults your senses. The reality is that this engine with shorty stack is quiet to a ridiculous degree compared to what we normally hear. You are not in danger of loosing your field, you aren't melting valves. And my point was my experience was more relevant than someone who has never seen or heard the engine that is being discussed.

I love these 4 stroke gassers. They must be chosen for the right airframe. WWI and fly-on-the-wing planes are an example. They are modest on power but the sound is jaw dropping and they are quiet. A short stack GX35 will beat any noise standard. I just don't want for people to miss out on these engines based on comments that are simply wrong.

subarubrat

My Feedback: (1)

Ok, here is a video I shot and the sound is amped up big time. All I can ask is that you listen to the whole thing. Listen to the engine and at the end, compare it to how loud the wheels are on roll out. You know how loud your wheels are on roll out, so keep that in mind and you will get an idea of how loud this engine is on short stacks.

http://subarubrat.com/misc/sig4stroke.wmv

jtisch

I have to agree with subarubrat. The Briggs and Honda engines are so quiet that if any other fuel powered aircraft is flying, I can't hear my own aircraft. As far as losing airfields is concerned, gas 4-strokes are near the bottom of the list as far as problems.

J

Nosedragger

We did exhaust tests with a stub stack and compared it to the muffler, the fact of the matter is the muffler is quieter than the stub stack by far.
We compared a muffled zenoah g26 to the honda with open exhaust and the zen was quieter. The unmuffled honda is loud and has an annoying exhaust note.

paul246

My Feedback: (9)

Nice plane and engine. You're right, that engine is quiet and has a nice note to it, too. I have a couple GX31's, one is mounted on my wife's bicycle and the other powers my mini-tiller. Great engines and a bonus that they run in any position. Someday I would like to get one installed in a Nieuport.

Nosedragger

So what you are saying is if you took the muffler off your car it would be quieter or as quiet with a muffler?
We all know thats not true.

Thomas46

By seeing the picture it seems to me you used the engine from a hedge trimmer (original vertical position)
No problem by fuel filling?? No fuel leak at filler cap?

paul246

My Feedback: (9)

Hi Thomas,

The engine came from my mini-tiller, then later I bought another engine off Ebay to replace the tiller motor. The original position would have the pull start facing upward.

I just lay the bike on its side to refuel. The cap is designed for any position and doesn't leak. If you wanted you could rotate the engine to any position desired.

paul246

My Feedback: (9)

No, I didn't say that. Never said anything about car mufflers that I can recall, or anything about mufflers for that matter.

bogbeagle

Is there any chance that you could do an objective noise test, using a meter, Subarurat?

That engine sure does sound quiet, on the Sig Rascal. That has open exhaust, does it?

I recently did a noise test on a Zenoah 26, with 16 x 8 APC (as recommended by HH)...topped out at 92dBA. Quite fiercely loud. Hard to believe that the Honda would be more noisy, but a meter reading would settle the argument.

Nosedragger

Open exhaust on the GX31 on the meter is a lot louder than a muffled G26.
The honda is louder with open exhaust, after building 5 on these thing I know what they sound like. We got over 94 db on the meter with the open exhaust Honda, the muffled G26 was well under 88.

What ever, the only way to do an objective test is to put a MUFFLER on it and test, then run the STRAIGHT PIPE. I gauruntee the straight pipe will be louder.

He claims it does but it sounds like it has a canister on it with the spark arrestor removed. Big difference between that and a straight pipe.

L.Rorence

To Thomas46 .


Hello.
I want to buy prop mount & engine mount.
Can you tell me where is the shop?
I'm sorry I'm poor English.
Here is South Korea.

L.Rorence(Hyung suk Yoon)

L.Rorence

To Thomas46 .


Hello.
I want to buy prop mount & engine mount.
Can you tell me where is the shop?
I'm sorry I'm poor English.
Here is South Korea.

L.Rorence(Hyung suk Yoon)

earlwb

One thought since this thread was resurrected is that a small company started making the AHC or OHC A-38cc gas engine. It is based on the Honda GX-35 internals, but they made a new crankcase, cylinder and so on for the airplane engine conversion. It actually runs pretty well and is fairly quiet too. Granted it isn't as quiet as the generators are, but it is much better that the regular gas engines though. Plus it shaves a lot of weight off of doing your own conversion and it is ready to go as a airplane engine. It also has a muffler available for it in case you don't want to use a straight exhaust pipe.

I sort of like the open rocker arrangement. It isn't a problem to give it a little oil now and then. It gives it a bit of a retro look. Plus it saves a lot of weight not having a rocker box on top too.




















https://www.youtube.com/watch?v=hltzsCuJ75Y

bogbeagle

Have you flown it, earl?

earlwb

Soon. I have it setup for a large AT-6 scale plane. Just finishing up things. Maybe at the local 114th RC Warbird Fly In in October. I had too many things happen lately thus I ran out of time to do stuff. I didn't even get to fly all that much this year either.

bogbeagle

OK.

Looking forward to hearing (seeing?) it perform.

There hasn't been much flying here in the UK, this year. At least, not for me and my mates. The weather has been remarkably uncooperative, and there seems to be a general apathy in the "flying community".

Can't understand the latter ... 'cos we have more stuff than ever, at a cheaper price. But, I feel that apathy, too.

earlwb

Yeah I am looking forward to it too. It has been something of a terrible year for RC flying.
First at the beginning of the year it was super windy all the time. Then the epic spring rains hit. Something like a monsoon season here in Texas. The lakes all flooded out and overflowed. Thus they had to close all the parks and our club flying field was included. Then towards the end of summer, they allowed a limited restricted access to our flying field. They finally opened it back up no restrictions at the club field, but now I got stuck having to work a lot and having to do chores at home and family stuff got in the way too. Can't win for losing. I did fly a few times on the rare occasion that everything came together, but not like when I was doing it a few times a week though. I still have a Gaui X5 RC helicopter that I haven't maidened yet either. All I have done is use the flight simulator for helicopter flying this year so far. We do have a club warbird fly in coming up in October. I hope to maiden the AT-6 plane with the engine on it before then and then fly it at the fly in too.

It does hand start once you get the hang of it. But using a Sullivan Dynatron works good too.
https://www.youtube.com/watch?v=MK1atJhnHUQ

spaceworm

"Very Interesting, but strange" It looks very (top) heavy and tall. How much does it weigh, and how tall is it? Thanks.
Sincerely, Richard
AMA 861960
Club Saito #635; Saito 56, 100, 120abc, 130T, 180;

av8tor1977

My Feedback: (6)

I had a Honda GX 31 on a Giant Eindekker. It had about a 5" long straight stack and neither I nor anyone else found the sound/noise the least bit objectionable.

It's just an old wives tale that straight pipes will damage valves, and I speak from many years of direct experience.

AV8TOR

earlwb

Actually it is fairly light in weight. It isn't really top heavy either. When compared with say a ASP 1.80 four stroke or one of the big Saito 4 strokes even, it is quite competitive in weight. it tends to weigh less than some of the other big four stroke engines. A Saito FG-40 weighs in at 1250 grams engine only. A OS GF-40 weighs in at about 1200 grams for the engine only.

all up weight with everything:


just the engine itself without the CDI unit, etc.

earlwb

I like the way the A-38 engine sounds. It has a nice mellow sound to it, not objectionable. It is quite a bit more quiet than a Saito engine of about its size. I think the Saito has a much more aggressive cam in it that causes the louder noise or bark. At low idle speed the A-38 tends to sort of have a burble (bubble popping) like sound to it. You can hear it in this video clip at about 6:30 when I was playing around with the engine.

https://www.youtube.com/watch?v=ydanHkO1pJU