Thaba Raptor

My Feedback: (2)

I have a 33% H9 Extra 330s that is nearing completion and first maiden. Been working on and off on her for nearly a year now.

I am using a secondhand 3W 100cc engine. the carb is sitting below the centreline of the engine, between the exhausts. I am new to gas engines and large scale so pleae bear with me if this sounds like dunm questions:
1. What is the ideal relationship between the centre level of the fuel tank and the carb intake for gas engines? Carb and tank in line? carb below tank centre line ?
2. Somebody recommended that I instal a vent from the top of the tank exposed to atmosphere with the open end below the level of the tank. Why?
3. The person also recommended that i take a long piece of fuel tubing and snake it fron the stopper along the top of the tank and then out to the carb. Will this not influence the fuel draw to the carb?


Now a question on the 3W 100. this engine has the modification to the carb done (ballancing the pressure on the diaphram). Although there are spark from the electronic ignition i could not get the engine to start. What is the recommended carb setting for this motor?

Thanx

Thaba Raptor

FlyerRick

Hey Thaba, Twisted here! (Dietrich 260 50cc/DA-50R, H9 SU26MM Sukhoi/DA-85) Glad to see another "Gasser" in the makings and good luck in your upcoming maiden! To answer your questions...

1) Always try to keep the outlet of the tank to the carburetor a touch below the inlet of the carburetor when possible. Although with most of the big 3 gas engines running walbro carbs, this is not real critical as the carbs have pumps to handle fuel flow.

2) The vent should always be at the top of your tank and long enough to go around the top of the tank then down to exit the plane below and behind the tank level. This is done to avoid what we call "siphoning". In most cases if you run your vent straight out of your tank and down to exit, the air passing over the opening of the vent tube can cause a siphoning-off of the fuel from your tank. **Please be very careful when running your vent line and be aware of the vent line in relation to your muffler(s) if equipped with canisters!

3 Take your carburetor fuel line right out of the tank and go straight to the carb inlet. always keep this line run as SHORT as possible!

4) If you have spark but no ignition fireing...check your voltage output from the module, check your fuel quality, check your fuel delivery into and through the carb, and always be sure to check you plug's condition!

Again good luck on the maiden and besure to post up some pix! [8D]

MMcConville

My Feedback: (4)

Thaba, In general one of the great things about gas engines is that fuel tank location is not critical. Orientation relative to the carb is not an issue that I have ever noticed because the carbs are pumped. In most models its best to mount the tank as close to the CG as possible so you dont get trim changes with fuel burn. Try to get it near the vertical CG too. Not for fuel draw issues but for better model trim (again no change with fuel brun).

As mentioned above in item 2, this is a good idea. The loop back in the vent line will stop siphoning and makes a prett significant difference to flight time. I was amazed by the difference this makes.

You'll love gassers, they are very simple and user firendly to install and run.

Thaba Raptor

My Feedback: (2)

Thanx guys for your input.
I was able to get the 3W 100 B2 started yesterday evening. WOW what power! For a guy who's biggest engines until now was OS 120 and Super Tigre G2300 two strokes and Saito 180's, this is a real step up.

The motor has been standing for approximately 2-3 years before that it was flown a bit. When i tried to prime the motor fuel did not enter the carb, not even after by blowing on the vent line. I then removed the diphram and fiddled with whatever i found and then fuel were coming through. i replaced the diaphram and tried to start it. and tried to start the engine following the the intructions in the manual. i flipped it about four times with ignition off, choked it ignition on flipped it about 7 times before it attempted to start. Swiched off, choke open and flipped it once or twice to clear . then swiched ignition on and tried to start it at a low throttle setting. Did not want to start afrer about 10 attempts. Opened throttle to about 1/3 and tried again eventually did start but was iddling rough. let it run for about four minutes then reduced throttle and trim to see how slow it will idle. Engine stopped after a while. Swiched ignition off and after checking to see how hot the engine was and if all bolts were tight. I reset the low and high end needles to ther factory recommended positions i tried to start her again. No luck she just did not want to start. Fuel was dripping out the carb barrel so it was not starved. I let her be for about 15 minutes and tried again using the process in the mannual. She again did start after more than a few tries.

Diagnosis: fuel comes through OK. When i checked the spark over the weekend it seened a bit faint. (I do actually not know how bright the spark is supposed to be....). My model still has the older innition module that runs on 4.8v. i am using a 4.8v 1100mA pack to energise the unit. The manual recommends 1200mA. Is 4.8v 1100 mA pack enough should i try a 6v pack or higher mA?

I have heard rumours about the 3W ignition modules giving troubles. How can I check the strength of the ignition pulse? I will chech the spark plug gap as well this afternoon. i seems that the NGK CM6 spark plug is not that easy to get hold off. the lawnmower guys dont have it an none of the hobbyshops in my area keep it any other make and model plugs that will also work on this motor?

What else can you guys recommend?


Thanx


Thaba Raptor

MMcConville

My Feedback: (4)

My guess is you are flooding it and fouling the plugs. Best start procedure for me is to turn the ignition on, turn the choke on and flip it. When it pops once, flip once more, then turn off the choke and flip again. It will normally start in 5 flips or so. This keep you from over choing and fouling the plugs because you get a po when there is adequate fule there.

Te spark is pretty small and hard to see. I doubt thats the problem. Tey the start up prodeedure and see how it goes.

FlyerRick

Thats kinda cool...my DA's start about the same as your 3W's Mike...Ignition ON, choke ON, 2 to 3 flips they pop...then one more flip, choke off, 2 more flips and they're running! Funny how things like that work!

I'd agree with Mike, sounds like you may be flooding it. One more thing...ignition modules aren't that expensive. If your in doubt, from what you've already said that the module your using is quite old, you might concider a new one which I'd bet would be an updated version from the one you have now. I really think that you would be helping yourself and your situation also if you'd seriously concider using at least 6volt 2000-2700 NiMeHi for your Ignition power.

Good Luck and keep us posted on your progress! [8D]

I have 3 of these 150 Twists that I have a lot of fun with too. One has a Saito 150, one has a 26cc gas, but the best of the 3 has an OS 120AX...what a blast these Twists are! Too bad they discontinued making them....what a shame!!!

Thaba Raptor

My Feedback: (2)

Hi guys,

Thanx for the starting procedures. Will try them over the weekend.


On the 3W website there is pdf documents that discuss the ignition modules. There are however 2 models a Model 4.1 and a Model 4.4. Mine is different to both. Dont have the red LED or the connection for the tachometer.

On my ignition module case it is stated that the operating voltage is 4.8V, nothing else. In the manual the sugested batery capacity is 1200 mA for a 2 cylinder engine.

if I go to a 4.8v 2300 mA sub C pack will it make a difference? if i go to a 6V 2300mA pack will I damage the ignition module?

Regards

Thaba Raptor

Thaba Raptor

My Feedback: (2)

Hi Guys, me again


I want to set-up my plane as per the construction mannual. (I have Futaba 9ZAP radio. ) to do this i need to measure the deflections on the control surfaces accurately.

Now i am running into a new problem: My Robart and Great Planes deflection gauges are too small (deflection angle and reach) to measure the angles and or deflections.
How do you measure the deflection angles on the control surfaces of these big birds?

Regards

Thaba Raptor

arobatx

Something like this works well, http://www.airwildpilotshop.com/More...product&id=542

MMcConville

My Feedback: (4)

[quote]ORIGINAL: TwistedRickster

Thats kinda cool...my DA's start about the same as your 3W's Mike...Ignition ON, choke ON, 2 to 3 flips they pop...then one more flip, choke off, 2 more flips and they're running! Funny how things like that work! "




Generally DA's and 3W handle the same. BTW, I have lots of DA's and Evolution gassers but havent owned a 3W for 10 years.

As for measuring control deflection ,this is the bes tool available (sorry to sound like a comercial).

http://www.horizonhobby.com/Products...?ProdID=HAN192

Grelker

My Feedback: (58)

You should not use a 6v battery for ignition unless it is regulated to 4.8 - 5.2v. You may fry the module if you do. The mah rating is only relevant for how much run-time you'll get out of the battery. I use 1100 mah for my 100cc engines and fly until i'm tired, around 6-10 flights.