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Going petrol, help needed

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Adam Chambers 220/07/2007 10:51:00
38 forum posts
Ive got a large flair hannibal and am toying with the engine needed. I can either go for a sc180 fs or a nice 26cc size petrol engine.

Im comfortable with four strokes but not petrol engines.I cant find the answers to my questions regarding petrol , so any help appreciated.

- Noise, does the standard siliencers work to the 82db limit?

- Do I need to purchase any kind of electronic ignition to start it? Most engines like zenoah come with a form of ignition coil and plug leads but Im not sure this is all I need.
Mark Lubbock20/07/2007 14:05:00
313 forum posts
13 photos
I have a Hannibal powered by one of the Champion 'Oldie' 28cc Mculloch engine as fitted to many strimmers. This engine is very quiet on a 20x6 prop & hauls the model about very well. Performance is slightly better with a 16x8 but still very quiet.
Ignition is via the standard electronic 'magneto' system which has proved totally reliable for me-the only downside is that it cannot be handstarted but needs an electric starter to achieve a good spark-this was my first foray into petrol engines & has been an excellent experience-the total reliability, ease of operation, cheap fuel & clean running seem to be the main advantages.
Hope this helps.
Adam Chambers 220/07/2007 14:11:00
38 forum posts

thats great. I want to go petrol but need to be sure the noise isnt going to be an issue. I assume the magneto you refer to is the built in system you see on models?

Do you have problems using a standard starter?
Mark Lubbock20/07/2007 14:15:00
313 forum posts
13 photos
That's right, it is the standard system.
These engines are fairly low compression so a satandard starter is fine-some of the more sophisticated engines (my oldie is very basic-you can easily convert from a strimmer) have easy start systems which allow hand starting I believe.
Adam Chambers 220/07/2007 14:29:00
38 forum posts
tops . A zenoah 26 it is!!

stuart knowles20/07/2007 15:35:00
2 forum posts
As petrol engines have a pumped carb, the space immediately behind F1 can be utliised for an additional silencer, with the tank located on the CG.

I have a Z38 / Hannibal which uses a Camping Gaz cylinder as a silencer.

Its all home made with copper pipe fittings, silver soldered. Cost nothing.

The engine noise from this model is drowned out completely if anything else is flying!

For me, the principle advantage is the clean running / non destructive fuel residue on paint and wood.

You won't be disappointed with the Z26
Stu k
Adam Chambers 220/07/2007 16:08:00
38 forum posts
WOW thats a good idea. Sadly I had already tried a different engine combo and your refit would involve a rebuild.

I like it though and will keep it in mind. I need to be sure the standard muffler is going to keep things quiet enough not to wake our safety marshall...
Mike Bell20/07/2007 16:11:00
269 forum posts
201 photos
I've just spent the last month or three getting to grips with a petrol jobbie (our Martin's) and have the following observations.
1 Standard dustbin silencers can definitely be a bit noisy. Fitting a larger can type silencer made a huge difference but at a price and you need the space to house it. Make sure a good, quiet exhaust is available for your chosen engine.
2 You need to be careful with gear installation because of the risk of interference from the ignition module. In most cases simply making sure the rx and module are separated by at least 12 - 15 inches is enough but in our case we seem to have had more trouble than most in getting to a satisfactory installation.

All the rest of my observations are positive ie clean fuel, reliable running, excellent pick up, easy starting etc. Don't be put off by the first two points, if you take them into account going petrol can be a very positive experience.
FlyinBrian21/07/2007 06:53:00
543 forum posts
The Zenoah 26 is a fine motor but do not discount others. See Puffin models web site for details of the 26cc MVVS which has a front mounted carb making throttle hook up easy. My own petrol experience has been soley of a ROTO 35 (see Falcon aviation or IAD web sites)and I have to say I have been very happy with it since I got it in 2004.

Most ingnition units are metal clad with the HT lead screened with wire mesh and the risk of interference is low however make sure you do a good range check (using a non PCM rx) to ensure there is no glitching. Install a pcm rx after testing if you wish.

Try to locate servos and batteries as well as the rx a min of 3"/75mm from all ignition components.

I have seen the following benefits from going petrol. cheap fuel 5gall! Extended duration (20 minutes easily from a 16 oz tank)Starting, running and reliability are all great.

The real Ron Truth21/07/2007 07:34:00
193 forum posts
9 photos
Can anyone comment on the noise of a standard muffler. Its a big issue for me and I need to be sure Im not going to end up investing in a better muffler straight away!!

Engine Doctor21/07/2007 11:15:00
2417 forum posts
31 photos
Hi Adam .I have three petrol jobs A Zenoah 45,a CCRP (Jamara)45cc and a Mckay 30cc the Zenoah has a new style Zenoah muffler which I have modified the outlet a little. That motor is very quite apart from the inlet roar. The CCRP is a very powerful motor but agian has a loud induction roar. The Mckay is in a different class and was designed for model aircraft use .This is fitted with an incowl silencer (Krumshfeld I think) supplied by stuart Mckay and is very quiet on a 20 x 6 prop; that pulled a 15 1/2 lb Cap232 vertical without excessive noise. Most of the port induction motors I have owned have had a very loud induction roar and need the air to be drawn from an air box . Another thing worth thinking about,if your using 35 mHz radio, is setting up you radio gear with a ppm reciever and doing a range check ,with engine running ,to check for and eliminate interference from the ignition circuit. Do not fly with this set up.Only when satisfied fit a good pcm with failsafe .If interference persist then try fitting an opto-isolator between your Rx and servos .Apperently ,so I am told the servo leads can act as aerials and pick up interference .Thhe opto-isolators are available from SM services and not expensive .One last thing ,all my petrol engines have taken a lot of running in.Unlike model glow motors ,petrol engines can take hours hours and get better and better . Hope it helps
The real Ron Truth21/07/2007 12:11:00
193 forum posts
9 photos
excellent doc,

I fear that the large alu cowl of my hannibal acts like a huge amplifier and will make it all a bit too noisy for my site.

I like glows as they tend to be well muffled and work to the 82db rule.
Doug Ireland22/07/2007 02:29:00
2088 forum posts
42 photos
I have a 45cc MVVS petrol burner and it drags my CAP 232G all over the sky no problem. Not sure about the noise though, doesn't seem any louder than an equivalent methanol job!
Paul Moore22/07/2007 08:08:00
23 forum posts
Adam, I can appreciate your concern about the noise but try to consider this. Noise tests will be taken with the model static and I am sure that the standard Zenoah installation will pass that ok. With regards to the plane in the air, you should have no problems either as the Hannibal is not "normally" flown in the sam way as the aerobatic CAP's etc where they use a lot of nearly max throttle and all of the throttle range, which is where you will find the maximum noise from all the air sucking!
Not sure how you intend to fly your Hannibal, but I know once mine is in the air and apart from a few high wing overs and dashes along the strip, it flies at about half throttle and is more quiet than some of my fello members 61 glo powerd stuf at high revs.
Go petrol, you will not regret it.
Shaun K23/12/2008 03:13:00
192 forum posts
38 photos

If anyone is still listening on this thread I'm keen to get feedback from those that have done their own conversion from a chainsaw / whipper-snipper/weedwhacker /weedeater engine for RC aircraft.

In the process of attempting to repair a recalcitrant Ryobi Lawn Hornet I've managed to get hold of a 2nd hand engine with very low use and good compression for $30 aussie dollars - that's less than 10 quid to the UK folk for a 30cc petrol motor that just needs a little engineering work to convert it!

There are some excellent web sites in the USA and it seems like there's quite a big community of keen converters on that side of the world.

If you've done similar conversions I'd be keen to hear the results. I've got what I think promises to be a great little engine for something in the 120-140 size range and now I'm keen to work out what to put it in.

I wouldn't mind scaling up Peter Miller's Feugray 260 plan as a contender...

Ralph Yeates23/12/2008 06:09:00
218 forum posts
18 photos

Also the fuel cost saving is great on petrol and they run longer.

All the people that have mentioned making silencers do you have any posts on how you did it as I have tried in Aluminium but not been very successful as my standard silencer is the wrong side of the DB limit and a replacement is over £100. Pictures, thoughts are most welcome.

Shaun K23/12/2008 12:32:00
192 forum posts
38 photos

Check out the site here for a home-made concept.

You'll need to adjust the sizing to suit your engine but I've done this with a small glow engine and had great results - less noise and no noticeable drop in power. As the above site suggests I used a metal epoxy similar to JB Weld and it worked well, but for the epoxy to take properly I roughed up all contact surfaces with coarse sandpaper first.

To help cut the noise I used two smaller outlet pipes that extend about half way into the main chamber. The total outlet pipe cross-section area is slightly greater than the original larger single outlet on the factory pipe, but since there's no straight through path for the gases to flow the noise level was much lower. If there's any other planes flying at the same time I can't hear my own!

Without proper tube bending gear I had trouble bending a header pipe to fit within the cowl so I used two smaller pipes that bent more easily and used aluminium solder to soler the header section together.

Since I've crashed the plane and haven't finished repairing it yet I can show a photo of the exhaust off the plane.

Ralph Yeates23/12/2008 13:51:00
218 forum posts
18 photos
Thanks Shaun need to raid the wife's hair care kit then hit the shed quick and start fabricating
Simon Chaddock23/12/2008 19:32:00
5621 forum posts
2987 photos
Hi Adam

I made these silencers (see Build Blog "Airframe for my 5cc") for my petrol engine out of baked bean tin material. It is light and solders well.

The "headers" (to use the American term) are copper (heavy but easier to bend) with silver soldered brass flanges but the rest are ordinary solder joints.

Each exhaust pulse of a 4 stroke tends to be a quieter than a 2 stroke because of the way the exhaust is released and as each pulse is twice as far apart (at the same revs) a simple exhaust expansion chamber with a relatively small outlet is very effective at muffling the sound. A long exhaust system also makes things quieter. However do remember that at some point in exhaust silencing the prop itself will be making as much noise.

Ralph Yeates24/12/2008 10:07:00
218 forum posts
18 photos
Simon amazing it's great that every one is posting pictures as I have loads of ideas now on exhaust fabrication. The hair mouse can is under construction at the moment and I just need a bit more work before I can do the Db test to see if I have reduced the noise of the stock muffler. It's not as pretty as yours but as long as it is quiet I can work on making a second one pretty but it will require a lot of bends and curves

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