Prop size on a Zenoah 26 in a WW1 bipe?

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martin collins
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Prop size on a Zenoah 26 in a WW1 bipe?

Postby martin collins » November 5th, 2017, 8:18 pm

Got to run the engine in my Fokker Tripe today, the plane is fitted with a well used Zenoah 26 mag engine and i was shown the motor being started and run when i picked it up using an electric starter. However i could not get it to start on a flick despite trying for over an hour :roll:
It will cough all day on the choke and does the same once the choke is off, it is trying to start but won`t take the cough into full running, in the end i borrowed a starter and hey presto it lives! I was trying it on a 40:1 mix but have now switched to 50:1 in the hopes that it will lessen the chances of the plug oiling, the plug gap is correct and is very wet when it is removed after trying to start. Anyho it does run using the starter and throttles up well, the prop fitted is a plastic 16x10 which i am thinking is too much pitch for this type of model, i would also rather use a wooden prop as i am expecting that this will end up on it`s nose at some point. What are your recommendations on the prop, i am going to buy one of the JEN geared starters so may look to them for a prop at the same time................Martin

Alan Cantwell 1131
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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby Alan Cantwell 1131 » November 5th, 2017, 9:29 pm

18x8 wood should return 7500 rpm, but it sounds like a new ring may be a good idea,

martin collins
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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby martin collins » November 5th, 2017, 9:33 pm

New ring? It seems to have plenty of compression Alan, almost stops the starter at the compression high point..............Martin

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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby Tony Collins 1073 » November 5th, 2017, 11:14 pm

Hi Martin. The main reasons that a magneto engine is difficult to start could be the magneto air gap, and/or the cranking speed.
The voltage generated will be too low to create a good spark if it is not turned over fast enough.
There is a technique to swinging a mag engine which some may find not too difficult and others may swing all day without
success. How about fitting a quick start booster.
Tony.
PS. make the air gap as close as possible while maintaining sufficient clearance to prevent touching.

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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby Alan Cantwell 1131 » November 6th, 2017, 7:23 am

Wot e said, drop some note paper on the flywheel, turn the engine over till the magnets attract, tighten up the screws, pull the paper, job done,

Bob Thompson1894
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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby Bob Thompson1894 » November 6th, 2017, 8:54 am

For a WW1 you dont need high pitch. A wooden 19x6 or 18x8 would be better. Always 50-1 oil mix, I use Rock synthetic as it is very clean. Nothing wrong with using a starter, there is a definite knack to starting a mag engine. Check the gap as Alan says, I use two pieces of computer printer paper. A new plug will not go amiss, either.

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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby Peter Siggins » November 6th, 2017, 9:31 am

Hi Martin I use classic 18 x 8 Prop on my tripe with a 26 Zenoah ,it’s been on 8 or 9 years and survived a few 3 point landings ( 2 wheels and prop :mrgreen: :mrgreen: ) without damage .Wood props wouldn’t survive many.
I have 2 26’s with this prop on and find it to a certain extent has a flywheel effect and run well at slow speeds for fly byes.

Just my tuppenorth

Pete

Bob Thompson1894
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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby Bob Thompson1894 » November 6th, 2017, 11:50 am

After almost being killed by a plastic prop on a King 60 breaking in flight and sticking like a thrown knife in the ground behind me, I would urge caution with plastic props and nose overs. Look for cracks around the boss. I only ever use wood.

david walker
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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby david walker » November 7th, 2017, 11:20 pm

Martin, I have a 26 in a Nieuport 17 and run on an 18X8 Menz with a 50/1 fuel ratio. There is as Bob says a knack to starting the 26. I had the same problem as you when I first tried to start the engine, cough all day but no start.
The 26 does not have a single magnet in the flywheel and does not start with a tradition "Flick".
I set the prop at 12.00 against compression as a start point.
You pull the prop through fast rather than a flick.
Choke on and with the prop turned back to 6'00 pull the prop over compression until it fires.
so engine should now be wet.
Choke off and same again start at the 6'00 position pulling the engine through so all the magnets are passing the pickup. Takes a bit time master but you will soon get thw knack.
I usually start at 2 clicks open on the throttle as full idle may be a bit slow.

If all else fails I have the 6 x 1 reduction starter from Just engine which works fine on the 26 Zenoah.

Hope this helps Dave Walker.

martin collins
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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby martin collins » November 8th, 2017, 9:27 am

Thanks again for the replies, i have borrowed a starter for the moment which gets it going though struggles through compression, i will be buying one of the JEN starters, is it worth the extra money for the 6:1, i will be running it off a car battery at the moment so 12v rather than 24, what slave battery are you using Dave?................Martin

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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby Alan Cantwell 1131 » November 8th, 2017, 6:15 pm

Did you close the mag gap up? Its so hard to diagnose when it’s not in front of you,

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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby stuart knowles 1611 » November 8th, 2017, 7:01 pm

The Jen 6:1 starter is very good and best used with a four cell Lipo, (although 12v lead acid will be fine) It is a better starter than a Dynatron.
I bought one at Cosford for either £30 or £32, The following year I went to buy another and it was £55. They said 'Exchange Rate' but I thought not

martin collins
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Re: Prop size on a Zenoah 26 in a WW1 bipe?

Postby martin collins » November 8th, 2017, 7:45 pm

Alan presumably the mag gap is at the rear of the engine? If so it is going to be a b*gger to get to as it will require the removal of some wood which is glued in place to stop the tank moving. Once the tank is out of the way i can get at the bolt heads to remove the engine. At some point over the winter i am probably going to recover it in a WW1 scheme as it is in the LOLA scheme from `The Great Waldo Pepper` at the moment and the covering is distinctly `tired`. When i strip it to refurb i will be removing the engine so i will check the gap then, i agree it may well be the problem as i had a Z62 a number of years ago that was a pig to start and that is what the problem turned out to be on that. For the moment i just want to fly as is and have some fun before the refurb so a starter will get me airborne. Thanks for your advice, i am sure you have the answer correct...............Martin


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