is there hope?Can this engine be converted?
 

Unfortunately, we dont get the weedwacker engines in India and even if we go get the odd one its like $250 but there is hope yet!!The best local manufacturers supplies a 34 and 35cc version but its like way too heavy for rc use.

Attached is a pic of the 35cc version which weighs about 4.7 kgs!!! 1.5HP @ 7000rpm
The 34cc version weighs 4.1kgs and produces 1.1HP @5500rpm

The guy says that the fuel tank for this engine has to be always mounted on the top!!!!!! and that its a carby thing i.e. no diaphgram carby on this one and I heard that gas engines usually dont like back pressure!!

Do the ryobi, weebwacker, homelite type engines use Diaphragm carburetors?

Looking at the pic and specs, is there any scope of lightening this sufficiently and modifying this suitably for RC use??

http://www.greaveslimited.com/portableengines.htm

is there hope?Can this engine be converted?
 

Hi edge/fanatic/w8ye,
Could u disable this thread for a while as i have a similar post in the gas engines forum.
Since i didnt get any replies i thought it may not exactly be the right place :-)

Thanks...

is there hope?Can this engine be converted?
 

Cometravi

The float type carb depends on fuel level to be kept at a certain level and therefore not suitable for aircraft.

Yes the weedies use the diaphram type of carb where fuel level is not the issue.

You need to check if a diaphram type carb is available at your place and that can be mounted to this engine. You might require some modification.

I have many diaphram carbs with me and can give you one for free if there is any means to take away.

is there hope?Can this engine be converted?
 

Cometravi

Further to my previous post.

If you get the right carb then you can convert this engine. What I see from the picture, you should remove the old carb and the air filter (you will not need the filter for aircraft use)and fix the daiphram type carb. Also the muffler must looke to be heavy. You can either make a small alluminum muffler or if noise is not the issue at your field then remove the existing muffler and just put an alluminum exhaust pipe to direct the exhaust out of cowl. As to the front of the engine, you need to remove the cooling jacket and cut the flywheel fins leaving enough material for the magneto only. You will also need to make a prop hub that will be attached infront of the flywheel. If your engine has any pull starter etc then you can remove that as well.

Wish you success.

is there hope?Can this engine be converted?
 

Thanks ZM2000.
I was hunting around for a diaphgram type carb and came up wih one option. They make a suzuki 150cc 4 stroke two wheeler motorbike in india which uses a BS type (BS26) carby may be also known as the Mikuni BS26 carb. The specs say that it is a "The oval venturi, constant vaccum (BS type) carburettor is operated by the pressure sensitive diaphragm enabling smooth transition of power and ultra-low emission. "

http://www.lakozy.com/Suzuki/fierodet.htm

Will this be too big to use?

Also, do the ryobi's have a fuel injection system? If not then is the diagphram in the carby enough to maintain pressure?
Are most two wheeler carby's floating needle type? Will a regular small 2 wheeler carby (non diapghramed but floating needle) be OK?

is there hope?Can this engine be converted?
 

Cometravi

The Suzuki carb for 150 cc engine will be tooooo big for your 34 cc engine. Forget it.

Ryobi's dont have a fuel injection system and by the way fuel injected engines dont have a carb, they get their fuel delivered right in the combustion chamber, controlled by a microprocessor.

Yes most of the two wheelers have float type carb and as I said before you can not use it for aircraft because those carbs need to be kept near hotizontal level all the time.

You can find diphram type carb in chain saws and weed eaters and also the size will be close to your engine. Their venturi is about 9-11 mm that will suit a 34 cc engine. Keep the hunt on.

is there hope?Can this engine be converted?
 

Cometravi

I have to add:

Since you said that with your current float type carb you need to keep the fuel tank higher then the needle, so I assume that there is no fuel pump associated with your engine.

The diaphram type carbs have an integral pump that operates by the pressure pulses it gets from the crankcase of the engine. Usually there is a tiny hole (about 1 mm dia) in the engine body at the carb mounting flange that matches with a similar hole in the carb to transmit the pressure for pump diphram. I dont think that you have that arrangement in you engine (please check) so you might have to do that modification as well. If you have good knowledge of engines then you can do it or else see an expert.

is there hope?Can this engine be converted?
 

I think i'll have to see an expert and get the carb built!!!! Can i find plans of a diapghram carb suitable for these engines anywhere?

I spoke to the guys who manufacture these engines... they said that they had a requirement for a engine with a diag carb a whuile back but they coouldnt meet the requirement and to his knowledge no one makes these carbs in india!!!!

Is it easy to get one made from a auto parts manufacturer?

is there hope?Can this engine be converted?
 

Cometravi !!!!!

No I dont think you or a local workshop can make a diaphram carburetor unless you spend a fortune.

Even the engine manufacturers do not make the carbs themselves. They buy it from specialized companies like Walbro, Tillitson, Zama etc. These 3 companies cover 95% of the market. Its a state-of-the-art job.

is there hope?Can this engine be converted?
 

Point taken ZM2000. I'll try and look for an importer. The only problem is that with teh duty structures here, a weedwacker costs more than a zdz!!!lol

is there hope?Can this engine be converted?
 

no luck with an importer!!

is there hope?Can this engine be converted?
 

Cometravi

Ofcourse its not worth importing. You can ask somebody coming from abroad to get it for you. It costs USD 40-50 in Dubai or USA and only USD 3(used, but good) in Karachi.

is there hope?Can this engine be converted?
 

lol USD 3 sounds good!!!

is there hope?Can this engine be converted?
 

BTW.. the website forthe engine says rotation-clockwise.. ist that a problem!!?

is there hope?Can this engine be converted?
 

The rotation should be anti clockwise when viewed from the front. Otherwise you will need a pusher type propeller that is not as readily available as the normal ones.

is there hope?Can this engine be converted?
 

Can a float type carby be converted/modified in any way to power a docile airplane?
i.e. can a carby used in a 50cc motorbike/moped be modified.

Are there any other carby types apart from the diapghram type which can fulfil the requirement?

I did fine someone who manufacturers diapghram carbs in India but they start for 200cc onwards!!!!!!!!!!

is there hope?Can this engine be converted?
 

I was doing some research and it seems that some high wing aircraft use float type carby's with a 'gravity' feed system. And low wing airplanes employ a fuel pump system to keep a constant pressure.. (For airctaft that use carby's instead of fuel injection systems)

is this correct as i am confused now?

If it is correct then cant a moped carby be used with a gasoline engine and employ a simple fuel pump driven by the engine itself to maintain the fuel flow.?

if i plan to use the engine in a floater kind of plane that wont do any aerobatics, will i still need the pumps? Can you tell me any applications where small fuel pumps may be used?

is there hope?Can this engine be converted?
 

Cometravi

I really wish to help you but as regards to use of float type carb and gravity fuel feed, some body having more knowledge then myself (or less) will answer you.

The float type carb needs a certain level of fuel all the time or else it will overflow cutting your engine due to rich mixture. Even a floater plane will roll and pitch to some degree that will frequently upset the fuel level in the carb. That will be unsafe for your plane.

As regards to pump, there are some pressure operated pumps available but you have to see that they are good for petrol and not for glow fuel only. Small electric pumps are also used in cars but they are heavy and need 12V battery. I use one of them to fill my fuel tank. Most of the bikes have gravity fuel feed.

Looking at your enthusiasm I wish you do try all the options but be SAFE with your engine and plane.

is there hope?Can this engine be converted?
 

Motocross type motorcycles have been using float type carbs for yonks, and look at the crazy angles they get to, so I don't see any real problem there!
Having said that, it is possible for the mixture to be affected in a prolonged steep climb or descent

The float type setup probably wouldn't take too kindly to inverted flight.

I agree that a high tank or fuel pump would be necessary.

If the specifications say that the rotation is clockwise, they probably mean at the output shaft, typically it will be at the opposite side to the flywheel, modellers normally attach the prop to the flywheel side, to get anti clockwise rotation. This suits the most common props.

I am wondering about your power to weight ratio, that cylinder barrel looks like it could be cast iron, (I could be wrong ),

However, give it a try and if it doesn't work, then try something else, it's the best way to learn.

is there hope?Can this engine be converted?
 

I also noticed that this partcular engine does not appear to be fan cooled and so the shroud is probably only used for covering quite a large magneto flywheel with no cooling vanes.

It looks like the old outside type, with the coil and points tucked inside.
In the interests of safety, it would be unwise to try to lighten this type of flywheel.

Both the cover and the rope pulley will have to be removed, and the pulley replaced with a prop driver.

Again these are only observations from what I can see from the photo, and from what I know about motorcycles etc.

I don't want to be seen as criticising ZM 2000, who seems to be a methodical and experienced modeller, with much more aircraft experience than I have.

Good luck with your project.

is there hope?Can this engine be converted?
 

i'll check it out to see if it indeed has cooling fins etc. BTW this engine is most widely used for backmounted crop strayer apps where the guy carries thsi engine around on his back..

is there hope?Can this engine be converted?
 

Willdo

Thanks for the compliments !!!!

I agree with your views.

is there hope?Can this engine be converted?
 

Thank you.
I'm not really much of a flier as yet.
I have played around a bit with two strokes, but I'm not a real expert with aircraft applications.
I am too old for motorcycles etc., and this looks like fun.

Was wondering how they cool that little engine in the sprayer application, I see no evidence of a cooling shroud on any of the photos of it, It has quite large fins though.

is there hope?Can this engine be converted?
 

Willdo

I think the cooling shroud might have been part of the sprayer from which that engine is removed though I agree the picture shows no sign of it.

is there hope?Can this engine be converted?
 

i seen 50 cc motor bike engine mentioned that would be more suitable to convert with an addapted walbo carb if nothing else can be found

is there hope?Can this engine be converted?
 

ZM 2000,
I believe you are right about the cooling method on the sprayer, you would expect the hot air to be directed away from the operator. so there may be a fan on the output end of the shaft.

However, all this still does not address cometravi's problems, and I think that unless you are an engineer with your own equipment, or have a friend who can do the job, it all could be rather expensive and needs to be balanced against importing a weedeater motor, (maybe secondhand? ).
If you persevere, I'm sure you will find an answer, your enthusiasm should carry you through.

Volksman,
50cc motorcycles would make great aircraft engines except that the cranks are normally full circle types which are extremely heavy, and of course you might have to change to a pumper carb as you say.

is there hope?Can this engine be converted?
 

HI Guys,
Thanks for your interest!! I think i may be pretty close to getting a Walbro carb. I have located a local supplier who can supply the carb of a 35cc gasser meant for RC!! Well the catch is that its as expensive as the engine :-)!! and it'll take a month to get here.

Just one thought though.
Is the hp of the engine, to a large extent, determined by the carby? At the moment, this engine gives 1.5Hp with the carby it uses. Will the Walbro carb improve this?

I think the colling of this engine is done by the fins to a large extent. But the fins look like very big to me. Can i look at reducing the fin size to reduce weight?

Type 2 Stroke, Single Cylinder
Displacement (cc): 35
Bore (mm): 35
Stroke (mm): 36
Fuel: Petrol
Compression Ratio: 6:1
Spark Plug: Mico-W175Z\ Champion PL7YC
Power:
KW (HP): 1.1 (1.5)
Speed (RPM): 7000
Starting: Rope
Dirn. Of Rotation at PTO: Clockwise
Ignition System: Fly Wheel MagnetoCB\TI Optional
Weight (kg.): 4.7

In their stationary engines, the cylinder is made of Cast Iron. I'll find out today what the cylinder for this engine is made of.
I have attached a pic of the engine mounted on a sprayer:

is there hope?Can this engine be converted?
 

Cometravi

The carburetor of about 9-11 mm venturi will be enough for it. HP depends on many things and a still bigger carb will not improve it.

The weight is too much but you need to see the actual weight after you get rid of everything that is not required for a flyer. My Ryobi weighs 65oz while Zenoah G23 weighs about 50oz.

You will also need to replace the spark plug with a "R" vesrion like Champion R7Y or similar to avoid radio interfrence otherwise a suitable capacitor will be needed but I do not recommend that(more parts, more risk of failures).

The fins are usually about 1/2" deep, if your engine have bigger ones then do not reduce them at this stage, I suggest leave them till you try it once in aero mode and then decide taking into account engine temperature with prop on.

Good Luck.

is there hope?Can this engine be converted?
 

Cometravi,
The reason for using a pumper carb such as the Walbro, is so the engine can be used in any position. This carb will not make the engine any more powerful unless it has a larger bore, if it has a larger bore, then the inlet tract on the engine will have to be matched up to the carb,
Also, because the mounting method may be different, you may have to make an adaptor of some kind to suit the carburettor, making sure that the inlet tract remains the same length as before. This is because this length is worked out to suit the piston port, and is quite important.
You will also have to drill a small "pulse hole"down to the crankcase from the carb adaptor somehow, to correspond with the "pulse hole" in the carb. ( if you have a problem a small hose could be a possibility). This hole transmits the alternating pulses from the crankcase to operate the pump diaphram in the carb.
So it's not just a matter of bolting on the new carb and "hey presto"!

Don't remove any material off the cooling fins ( unless you have definite proof that the engine is running too cool), - don't modify anything without a very sound reason! and some knowledge of what you are doing! - I said earlier to give things a try, but didn't mean you should do it without thinking about it carefully beforehand!

Do you have a good knowledge of the basic operating principles of the two stroke engine? If you are interested ( let me know ) and I probably can find you some links to good sites on this subject, and although many of them tend to be for racing etc. they give you a much better understanding of the subject.
There is a good book by a guy called Gordon Jennings, who sussed out the two stroke, and passed on the information to us all. An old book now, but is still as relevant today as it was 20 years ago, and in many peoples opinion has never been surpassed.
Sorry for the sermon!

ZM 2000
Looking at the engine mounted on the sprayer, I notice that it drives a large centrifugal fan, and it looks to me like some of the air is bled from this to cool the engine, what do you think?

Looks like you and I sent in a post within seconds of each other, hope I didn't repeat, or contradict anything you said.

is there hope?Can this engine be converted?
 

Willdo

I figured exactly the same that cooling comes from some outlet of the fan.

No you havent contradicted anything. I mentioned the same about the fins and also the pressure pulse in my earlier posts.

RE: is there hope?Can this engine be converted?
 

Hi guys.. just a quicl update... no walbro carb yet...
A thought did cross my mind though...
If i use something to pressurise the fuel tank and ensure that fuel flow is maintained to the engine, can i use the float or any other type of easily available carburettor? I think ZM said that the float type carby may overflow..

RE: is there hope?Can this engine be converted?
 

A couple late thoughts from left field. Check out the Walboro web site so that you under stand how a Walboro works. Make a large two needle R/C model carb, get a repair kit for and large Walboro and use the parts to make a regulator. Use crankcase pressure to move fuel from the tank to the regulator.
If your engine MUST run CW then using a production pusher prop mounted on the front will work. Of course you will need left thrust built into the firewall.

RE: is there hope?Can this engine be converted?
 

I sure hope the sprayer version has an all aluminum short block. Otherwise, you're gonna have a very tough time finding a plane that will fly with a 35cc engine that weighs 4.7kg (10lbs).

RE: is there hope?Can this engine be converted?
 

The description says the PTO runs C.W. so if you make a prop hub for the flywheel side a conventionat prop will work. Many older light planes had the fuel tank mountd just ahead of the windshield with a wire going through the fuel tank cap with a cork on the bottom. this was the fuel gauge. Conventional float carb. Don't see why it wouldnt work as is in a Cub, Champion. etc.

RE: is there hope?Can this engine be converted?
 

A float type carb should work so long as you don't try to fly upside down, and as long as the fuel can get to the carb float bowl, ( eg gravity ).

The engine could be lightened by removing the heavy flywheel and having an aluminium prop hub made, (or if the original flywheel hub has the contact points cam on it, you could use that instead), then use a battery pack instead to supply the power, this battery pack mounted in the tail could be used to counterbalance the heavy engine up front. (If the cylinder barrel is cast iron, there's not a lot you can do about it, just don't go chopping off fins)
An aircraft with a short nose would also help, (you'll probably be looking at a high wing slow flying aircraft for this engine).
I think that your wing loading would need to be around 29 or less. - Someone please correct me if I'm wrong.
There's no harm in trying things but be prepared for the odd failure, it's all good experience, but always think carefully before you change anything permanently.

RE: is there hope?Can this engine be converted?
 

The plane I had in mind for this was a SPAD CLT (Cub Like Thing). And thanks for the encouraging words on the float carby. The walbro carb is impossible to find in this part of the world.

So the Q stands, If a maintain the fuel supply using a fuel pump for e.g. like the the one used for fuelling, rather than gravity, will that suffice? There is a way to feed fuel using a simple tank and pump arrangement like the one used to pump water to the windshield. But using this kind of arrangement, wont the float carb overflow if the pressure is greater than the one exterted in typical gravity feeds?

Is there any other type of easily available carby used in bikes, automobiles etc which is not too tempramental to odd aircraft attitudes? I was thinking, these stunt dirt bikes go all over the place and yet keep running... dont they use a float type carby?

RE: is there hope?Can this engine be converted?
 

Cometravi ! !

Welcome back.

Let me clarify regarding float type carb and fuel pump.

1. You can use high tank and gravity fuel flow.

2. You can use the flaot type carb with certain reservations. The problem is fuel level that will be frequently disturbed due to bank and pitch of the plane, even if it is a floater type of plane. This upset happens in motor cars and bikes as well but they can live with it because the engine is connected to wheels that keeps it turning. In airplanes such upsets can stop the engine and you need to land immediately. So better go ahead and give it a try. Let us also know the results.

3. You cannot use the windshield washer pump because a) the material might not be compatible with petrol b) they dont have a system to stop & work on demand.
The fuel pump in motor cars can be used but they are too heavy for a model airplane. Pressure is no problem, the float type carb is made to handle it.

Good Luck.

RE: is there hope?Can this engine be converted?
 

Hi ZM,
Just Wondering, if the pressure is no problem, then why does the windshield washer system need to stop and work on demand?
So i take it that there is no other type of automobile carb that is not too tempremental to odd aircraft attitudes (bank roll etc)

RE: is there hope?Can this engine be converted?
 

Hi Again,
I have located a local supplier who can supply Sthil carburettors for about $60. The problem now is which carby!!! What kind of carby should i look for. According to him the carby can be used on 30cc engines.
As far as throttle control goes, do these carby's have throttle control built in or does that vary from carby to carby?

WIll it be easy enough to fit the carby to the engine mentioned?
I asked the price for the Sthil engine but its prohibitively expensive:
its like USD400 just for the engine!!!!! so i'll stick with the local sprayer engine only!!!

RE: is there hope?Can this engine be converted?
 

If you are willing to pay $60 for a carb, how about just buy one from a vendor here in the USA and ship it over there? I've bought them off E-bay for as little as $8 a piece. Shipping can't be that expensive to India.