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Polini, Briggs and 447

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  • Guest's Avatar
    Guest replied
    Polini, Briggs and 447

    I have done 20 hours with BB Trya 03, Rotax 447, Hellix propeller (160 cm) this year. It consumes 7 ltr/h at 5500 rpm, ground speed average 75 km/h. (my weight 95 kg).

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  • Paul Dewhurst
    replied
    Polini, Briggs and 447

    Don't forget the Polini 100 and 200 engines use the same gearbox and clutch set up, and have been sold in quite large numbers and been out for a little while now, and I haven't heard of problems in this area yet.

    Also the Germans very keen on centrifugal clutches for some reason and run Rotax 582's with them using C gearboxes with rubber damper removed.

    The BMW R100 conversion in a UK Skyranger uses a c box and centrifugal clutch. If I remember correctly they got better results than with the rubber damper - the clutch proving to be a better smoother of large pulses at the low RPM range.

    Paul

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  • Mick Broom
    replied
    Polini, Briggs and 447

    Hi Dave,
    Traditionally you will only get problems at low revs due to the power pulse especially on a single cylinder unless there is a frequency problem in the drive train and as the drive is disengaged at low revs it should remove any problems.
    The clutch will lock up when engaged which happens at about 3000 engine rpm
    We are playing with different set ups at the moment so have not done any meaningful hours though all indications are good so far.
    Information from the factory is a bit slow but I suspect that is down to the supply train as much as anything.
    They have sent the early motors out with less than perfect carburetion and depending on what its fitted to you may need to experiment a bit.
    Paul took the Flylight demonstrator to Slovakia for the Europeans with basically a new motor out the box and it did not show any signs of trouble with no running in and two weeks of comp flying , much of which was flat out.
    Mick

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  • Dave Smith
    replied
    Polini, Briggs and 447

    Thanks Mick.
    Yes, it was the Polini.
    I ask because users of gears have traditionally had problems without a damper.
    I did think that centrifugal clutches locked up in both directions once up to speed, but perhaps there's a freewheel incorporated?
    Or perhaps there's very little torsion reversal once beyond the clutch revs?
    Hours so far?
    Dave

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  • Mick Broom
    replied
    Polini, Briggs and 447

    Dave,
    If you are talking about the Polini then the jury is still out as far as long term reliability of any parts.
    The engine has a centrifugal clutch so would not need a torque damper and together with a balancer shaft seems to be as smooth as you can get a single cylinder motor.
    Its a bit strange to watch the prop blowing around when on the ground and I have fitted a prop brake so we have that option in the air which must possibly make it a first trike fitted with three brakes.
    So we can stop it and are now working on the fine tuning to the going bit.

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  • Dave Smith
    replied
    Polini, Briggs and 447

    No mention of any kind of torque damper, and it has gears. How are they lasting??
    Dave

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  • Kevin Armstrong
    replied
    Polini, Briggs and 447

    Yesterday did some testing with a full tank of gas, as mine has a 35 litre tank the change in performance full to empty is quite noticeable; from rolling start it got to 650 feet in one minute; this was with the GPS equipped camera rolling so isn't wishful and I might stick it on YouTube.

    So not massive performance but gets much better as the fuel empties, however it has got a leaning device on and it is interesting what you can achieve with one:-

    I warm up with the leaning device open as you can see the slight exhaust smoke left over from choke to start disappear as it takes effect; it clears the excess and reduces bore wash from excess fuel, but this also means liberties with jetting precision can be OK too.

    The makers sell a 'high altitude jet kit' to drop the gas at over 5,000 elevation use, I ordered one but then decided to leave the carb alone and just lean as required during the flight, hardly stressful other than remembering to set back to full rich in the circuit.

    Built the leaning device for £10-15 using Hoselock micro watering tube and fittings, plus a £5 needle valve from eBay and a knob pressed onto the knurled top for gloved hands use; details happily given on request

    Looking forward to longer flights in Summer to see what max range and fuel burn is

    On the Polini you maybe could install a leaning device and fail safe back to rich if it starts heating?

    On a two stroke definitely only to be used with EGTs...

    Kev

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  • Mick Broom
    replied
    Polini, Briggs and 447

    Hi All,
    I have the PKW carb on the 250 Polini ( fitted to a Flylight Dragon) and it is a bit of a pain but Dave and myself are enjoying the messing around to sort it and after all its just a carb if made down to a price.
    Two stroke fuel burn in general is more than a four stroke but you need to factor in the extra weight of the four stroke which with modern two stroke design redresses the difference in fuel burn and oil out the back.
    Will let you know what the consumption is when we fit the fuel computer.
    As an example my Shadow fitted with the 503 Rotax can get 5lts/hour with even me driving it and with Dave in comps the best was 3.5Ltrs.
    At the end of the day if you are interested in performance forget weight at your peril.
    Just saved 1.5Kg off the Polini installation and now await to see if it works.
    This dereg is so much fun. :-)
    Mick

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  • Wally Hayward
    replied
    Polini, Briggs and 447

    Paul

    " - good for flying upside down though..."

    You have just reminded me why I have a Tillotson on my NMZ201:-)

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  • Paul Dewhurst
    replied
    Polini, Briggs and 447

    The three 200's we have on Dragons all have the float bowl PKW carb and ditto the 250 we are fitting. Looking at the website it seems the Walbro is an option on the 200 - but listed as though the standard supply is the PKW. Standard on the smaller engines though.

    My laymans thoughts are that diaphram carbs like the walbro are OK on smaller engines, but show their weakness on larger engines and arent as accurate at mixture settings and dont have the adjustabilty for optimum setup across a range of RPM and loadings.. - good for flying upside down though...

    Paul

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  • Guest's Avatar
    Guest replied
    Polini, Briggs and 447

    Ah that may explain my misunderstanding, the engines that I saw were equiped with the Walbro carb, this was giving mid range problems. One guy was experimenting with a Bing which he claimed was looking promising.

    Ginge

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  • Guest's Avatar
    Guest replied
    Polini, Briggs and 447

    Hi Guys,
    The Polini can come with two carb types, the conventional PKW carb or a Walbro, Iím not sure what carb goes with what engine capacity, but my Thor 200 has the PKW carb.
    Paul, you are correct in saying it comes from the factory set rich, so rich it will hardly run. The EGTís show this well. I have dropped the idle jet right down to a 35 and it still starts first time with little or no choke, Iíve just ordered a 30 along with some smaller main jets so should get better fuel economy and an EGT around 580 Ė 620 across the range. Still have a very small hot spot mid range-ish, this may need a slightly different needle profile or different slide cutaway to cure, but itís me just being anal! Ben will confirm this attribute!! The needle is set to its second from the top slot & I should be able to drop the needle right down, but only once I have cured the afore mentioned hot spot.
    The Thor 200ís manufactured before March of this year have got a factory mod sent out that lowers the compression & alters the reed valve movement to help address some of the ďpiston melting problemsĒ that some of these engines have had. The newer ones have this mod done to them. These problems have mostly been in the paramotoring world, but in a lot of these cases its guys who have altered the carb settings and not had an EGT fitted to see whatís going on in the engine. Iím sure this might not be the case with them all, so I apologise now if I have upset any of our paramotoring friends who might read this.
    Working with Pat Gardner, who also has the same engine in his Dragonfly, we have had identical EGT & general running results from adjustments made which confirms a good manufacturing consistency, well done Polini!
    I think we are now close to getting the carburetion perfect; I am now going to start playing with Lord engine mounts to make an already very smooth running engine silky smooth to the point where you will hardly feel it running, as Ben said, ďanal!Ē But thatís what I love about SSDR, you can tinker to your heartís content and as Iíve just bought a lathe & milling machine, I have to do something with them!

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  • Paul Dewhurst
    replied
    Polini, Briggs and 447

    Its the same carb. Jetting may be different though. I believe its set up quite rich to help cooling on the 200.

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  • Guest's Avatar
    Guest replied
    Polini, Briggs and 447

    That sounds encouraging, it seems that with the latest model they are trying to address the carb problem, friends in the paramotoring world seem to rate the Polini. Is the new carb adaptable to your engine?

    The combination of lightness, smoothness and power could make it ideal for SSDR use

    Ginge

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  • Guest's Avatar
    Guest replied
    Polini, Briggs and 447

    peter.finlay@nov.com[/U]

    [3]Cheers,[/3]

    [3]Pete[/3]

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