Thomas46

Dear @ll,

writing from Germany to let you know that we are also working on GX35 and to make it usable for model aircraft.

If you like you can check out our favorite German platform by using the link

http://www.rc-network.de/magazin/art...rt_033-01.html


Sorry the report is in German language only, but much pictures. Also you can ask questions to me here. Apologise my poor English.

Just briefly which conversions have been done:

Remove all unneccssary things

Main jet drilled to 0,5mm, but mixture is a little to rich. I am waiting for 0,45mm (it's ordered) drill to lean.
Plastic inlet manifold drilled to 10mm diameter.

Replaced exhaust box to outlet manifold and other silencer.

Made test with CDI. Sparking became better, easy to start the engine by hand.

That's in short.

Next test is to change the carburator to Walbro WYK-194 ordered in Utah ;-)) with L and H needle.
Later Cam will be reworked to increase valve hub for better combustion room filling.

Best of GX 35 is compared to GX 31: It runs well in inverted position without any Oil loss.

I've forseen the engine to use firstly in Senior Telemaster Clone>> T240 to finish dynamic test. Later, let`s wait and see.

Thats all so far from me, any question, let me know.

Greetings

Thomas

fokker38cc

Hello
Oh, my dream, good job, but in Argentina , this is very expensive,near 200 Euros ( five days at job).Engine only.
I have no option, take chinese chainsaw 35cc engine only at 75 Euros.
I see your link, it is to enjoy.
Happy landings
Jose

Thomas46

Jose,

Engine is expensive in Germany too between 270 and 320 Euro, depending the conditions and not easy to get.
Special prop mount additional 40 Euro.
China clones much often offered in ebay but so far I'm doubting the quality level of these.

But at at the end of the day it is a very nice power plant.

Regards
Thomas

arobatx

crap...posted in wrong thread. sorry

Thomas46

Some News,

original carb was not nice to adjust the mixture.
Therefore I tried Walbro WYK-194. It was ordered from Daves Motors in Utah.
Perfect, this carb is fully adjustable. Max RPM increases to 5600rpm with Menz prop 20x10

Has anybody made some experience with such carburator? Currently my knowledge is only from the test bench. Not flown the engine yet.

You can check out additional report here:
http://www.rc-network.de/magazin/art...rt_056-01.html

Sorry it's in German but much pictures.
In case of questions do not hesitate.

Cheers
Thomas

Thomas46

UPDATE:

GX35 is now airborne in T240 (Senior Telemaster)
Here some pictures

Propeller is now 22x8 Menz, wood.
It turns with 5700rpm.

Carburator WYK-194

Report is available here:
http://www.rc-network.de/magazin/art...rt_015-01.html

At the end some movie where you can hear the fantastic engine sound.

Greetings
Thomas

fokker38cc

Hello
nice to see your beatifull plane and little 4 stroke flying.
I can see too many hours at job to convert the little gem.
I am put your german post in google translator and see you have problems with crankshaft, I am sorry, but this happens.
In the club a modeler get a Honda four stroke like yours, dont know how many cc have but come from a weedeater dissasembled because the engine start to burn too much oil. Need repair and spare parts are expensive here.
Your engine have chromed cilinder liner?
Thanks for posting your job, numbers.
Good white fumes , do not have problems clogging the little diameter tube to heat the liquid for smoke?
That engine is my dream, but I will buy four stroker when to Argentina come the chinese clones, cheap, dont know when, but when I catch one you will be the first person to know how perform the engine.
Compliments for your fine job.
Jose
Argentina

adrian222

My Feedback: (1)

G'day Thomas

Would it not be easier to get a Sthil 4 stroke engine over there I think they would make a better engine as they have no oil in the engine and run on 2 stroke mix and come in various sizes. Have a look here.

http://www.stihl.com.au/dspArticleIn...msArticleID=86

Adrian.

Thomas46

Hi Jose,

the problem with the crankshaft was caused by me during start. Plane made a very fast double back (like a rabbit). I stopped the engine directly, but 9.5kg gross weight went streight in our airfield hedge. In the hedge we have some steel poles and ropes. Prop washer hit such pole and bent the crankshaft. **** happens.....

Cylinder liner? I don't know if chromed or Nisil/Nikasil surface. Anyhow the engine has now more then 10 hours on the clock, no oil consumption, no leak, nothing.
Regarding the smoke system. No problem with the diameter, it is common and working system. Only thing I will change next time is the position of the tube nearer to the engine, to get more heat for the smoke oil.
THX for the compliment, you are right, it was huge work but also challenge, and at the end of the day it is now a very nice and well working engine.
Important is that the base of the engine is good and in my opinion is Honda or Stihl best what is to get. Than the time investment is not blown later.

Hi Adrian,

from view of modellers who want to convert 4-stroke engine you are right.

But the Stihl design is for me not more than an OS or Saito 4-stroke. Just fuel has been changed. OK this opinion is a little to simple, but the Honda design idea is very professional.
Who can built an all direction engine with closed lubrication system, no leaks. Means, just check engine oil level and fill normal gasoline. nice....
Also the Robin 4-stroke has lubrication problems when engine is used hanging inverted.
And at least the Honda engine you can order as power plant at the dealer. No need to buy a complete weedeater. So far I know, Stihl is not offering, that makes it very expensive.


Many Regards
Thomas

Nosedragger

The bore in the GX35 is plain diamond turned and the piston has a coating on it.

Chris Cobain

Quick question for Thomas46 - why are your thrust values in kg? In the metric system, shouldn't thrust be measured in Newtons?

I have a Honda GX35 arriving today. You have presented the best information available on converting this engine to aircraft use. Thank you!

Thomas46

Hello Chris,

physically your are right,
but practically I have just measured the thrust with a digital Fish scale and this showed me the result in kg.

Thank you very much for the praise.

Asking you for all the other 4-stroke "converters" in this forum, please distribute your conversion here, that we can learn other ideas and how to make.

Chris Cobain

Thomas,

Did you machine your own propeller hub? Now that Carr Precision is out of business, do you have any recommended sources for a complete propeller hub?

Thanks -

Chris

jtisch

The nice thing about the Stihl engines are that they are compact. The GX35 is a nice engine but quite bulky. A Stihl 65 is more compact than the GX35. Stihl 32s will fit in a proper 1/4 scale WWI rotary engine cowl( Fokker, Nieuport, etc). What I really want to get my hands on is a 36cc Stihl.

J

adrian222

My Feedback: (1)

That's the engine I am after too.

Thomas46

Hello Chris,

if you like to have that what you can see in the picture, please write a PM to me. This is nothing to talk about in this thread.

The parts are professional made on a CNC lathe, not cheap but very good quality.

Center bolt is a metric M10x1.25mm, that means it is not the standard threat (M10x1.5mm), but fine one. Not so much torque needed to get the right press force for propellers.

RCSPORT FLYER

My Feedback: (11)

Is Carr Precision out of business? I see they still have their website up.

Chris Cobain

The owner told me he had sold the machine shop, and was limited to stock on hand.

nitro joe

My Feedback: (2)

I was curious when I read that statement last Friday,so I sent them an e-mail.
Seems strange to me that someone connected with selling stuff let this go unchallenged.


To: [email protected]
Sent: Friday, October 09, 2009 1:40 PM
Subject: ordering parts

Post #13 states you guy's have gone out of the RC engine conversion parts business...True?

http://www.rcuniverse.com/forum/m_7869275/tm.htm

From:
"Dave" <[email protected]>
Subject: Re: ordering parts
Date: Friday, October 9, 2009 5:33:42 PM

no we are still making parts and kits for the small string trimmer type engines.
thanks dave

Nosedragger

I don't think they get on here.

But its odd, I did hear the same thing a couple months ago and I'm sure there was a post here regarding that.

Mark Twain "The reports of my death have been greatly exaggerated."

subarubrat

My Feedback: (1)

Just another note on weight and size. I replaced my muffler with a 90 deg elbow about 2 inches long. Exhaust sounded "snappier" but did not seem any louder.

Nosedragger

Its louder depending on where you stand. Its not a good idea to run a short exhaust like that, the exhaust valve will burn up and risk losing your flying field with the noise.

Ralphbf

My Feedback: (27)

The trick is running long enough pipes so cool air can not reach the valves.

We use to put rags in our drag pipes to prevent this.
It's suppose to keep the valves from warping.

Nosedragger

actually the short pipe causes the engine to run lean, which is what burns the valve.

subarubrat

My Feedback: (1)

"Its louder depending on where you stand. Its not a good idea to run a short exhaust like that, the exhaust valve will burn up and risk losing your flying field with the noise."


Nearly FIVE YEARS of actual experience. The engine runs 100% like new, the valve is not exposed to cool air even with this shorty pipe, and the sound even mufflerless is FAR quieter than any muffled two stroke and most glow 4 strokes. People have often mistaken it for electric when it is no right around the flight line.

You have never heard the plane, you have no experience with the engine, and yet you are disputing my factual experience with your speculation.

The record on this has to be set straight.