captinjohn

I am talking exact same everthing except for change in prop....and fuel mixture if needed!!!! Thanks Capti,n

rmh

Did anyone run a vibration check on this engine?
specifically --if mounted on a "floppy" board - how well does it do in the --say 2700 to 3200 rpm range -
In checking various singles - I find some engines have a low vibration in this area-some really shake .
there has to be some period of increased shake and most of these engines seem to put the unbalance at about 3000 rpm- then modify the ignition curve to reduce the shake thru this period.
mounted solidly to a heavy plank -this does not really show up as much--

strato911

Don't forget that when you mount them on a "floppy" board, there is a potential to create a harmonic vibration, which could cause a resonant frequency to show itself as a dramatic increase in vibration at specific RPM's.

Changing the length of the board will change the RPM at which it resonates. If you're finding that all your engines seem to have the most vibration at 3000 RPM, try testing again with the board shortened by 1 inch. You might be surprised to see the RPM of max vibration change.

Remember the infamous [link=http://www.physics.bcit.ca/netshow/tacoma.avi]Tacoma Narrows Bridge[/link]? (if not, perform a search)

Volfy

My Feedback: (23)

If I could find a "floppy board" that simulate the same effect as being mounted on an model airplane, I would use it for every engine I bench test. Fact is, the damping characteristics of an airplanes is different sitting static on the ground AND flying through the air, which can in turn be different at different airspeeds. Everybody has tried sticking a hand out a car window at speed. Ever try moving that flat palm up and down real fast? Not quite as easily as with no wind, is it? The same applies to airplanes engines. Singles can be big shakers, but their vibration modes are not at all complex and so a lot of it is easily damped by the airframe and the high-velocity (read high-energy) air moving past it. This is especially true if the engine is mounted vertically on the airplane, as most of the vibration of a single occurs due to the power pulses in that axis.

Multicylinder engines usually enjoy much better dynamic balance, but are more likely to generate higher frequency vibrations that cause problems for electronic equipment. The higher ones travels through the aiframe much easier and are not as easily damped out by the rush of passing high energy air fluid.

In my line of work, I sometimes do vibration analysis on oil field equipment like shakers, centrifuges, etc. We routinely stick multiple triaxial accelerometers onto these heavy machinery and analyze the input with various instruments and analysis software. I could do a vibration analysis on these engine, but I don't know of a good way of simulating flight conditions, where an airplane spends most of its life, hopefully. This is why it pains me to watch people break in their engines mounted on airplanes and sitting on the ground, where these little vibrator motors can wreck the most havoc utterly undamped.

Equally bad are some of the so called "vibration isolator"engine mounts, most of which don't do a darn thing but exacerbate the vibration problem.

At 46cc and of mildly oversquare design (IIRC), the Poulan is not too terribly bad a shaker. With the Synchrospark ignition, it ran very smooth through the RPM range. I easily tell the ignition advance/retard kicking in and out if I go real slow on the throttle movement, but no rough spots anywhere on the power curve. The only time I notice any excessive magnitude was at very low idle, which I believe is due to uneven power pulses caused by poor carburetion - etiher I haven't tweaked the needles quite right or the intake air velocity was getting way too low for the venturi size. But at idle, these low frequency vibration don't carry a lot of energy and so won't do hardly any harm to the airplane.

rmh

I did not explain my "floppy board" very well-
My test rig is a very solid angle iron setup -which allows a rectangular board to fit into a frame. I run 210's on this setup.
anyway - If the board is attached only at the sides -it can twist . vertically.slightly --etc..
All singles have this transfer point of unbalance-the twins (boxers) don't.
Resonant frequencies are most of the vibe problems in our models - I once made and sold vib isolator setups for glow four strokers - these held the engine solidly along the crank axis --then controlled the rotating forces -in an adjustable snubber.
using it properly ---one could cancel the resonant combo of the engine "kick" in a given airframe.
since then, I have seen various permutations of this same rig for gassers - some using hydraulic snubbers - which overheat easily. heavy and kinda clumsy
anyway - the reason I asked on the Poulan, is that the "overbalance on the cranks -on some indusrial setups are not as smooth as some modern gassers -designed specifically for model use.
Way back when - we mfg'd an industrial machine which utilized a large axial flow or a Roots type air pump.
These things could make an entire building "hum" -depending on the building construction.
We suspended the pumps -using various springs etc., and finally got them to self cancel -except during run up -which still made one nice "hum".

SilverEagleBW

My Feedback: (1)

Now what would really be cool is if someone made a spring starter for the poulan,like the quadra and the zenoah,,You do have a shaft sticking out the back.I am gonna get me two and see what i can rig up.Any suggestions on that one?

FLYPUCK

My Feedback: (8)

Hi All,
What techique are you guys using to keep the carb attached? I just picked one up and it has a small rubber hose connecting the carb to the side of the cylinder.

Thanks

RC Extreme power

My Feedback: (24)

wow
You found a old thread, I still have the engine that I converted when this thread was active.

to answer your question, do not know what tools you have but I used a peace of phenolic block and turned it round on the out side, The carb port on the engine is egg shaped so you have to mill or use something you have to make it fit.

Milton

skip1320

http://www.brillelli.com/page2.html,carb adapter,works good!

FLYPUCK

My Feedback: (8)

Thanks for the help!
Hope that engine is still running Milton.

=Doug=

FLYPUCK

My Feedback: (8)

Just my luck! I finally got around to running the Poulan 46 today. Fired right up but was missing a little at full throttle. Could just be the needle setting or perhaps sucking some air from the intake.
Anyway, now that I know it runs ok I logged on to the Brillelli web site only to find they are now out of business. They weren't last week but they are apparently goners today.
I've checked some sites and RC Extreme Power's post on securing the carb but I don't have the machinery or know how to pull off machining an adaptor.
Does anyone have an old adaptor off a spent engine they would be willing to sell or another source for one?
Any help would be appreciated!!

Thanks,
Doug

RC Extreme power

My Feedback: (24)

Check with Ralph, He used to convert the poulan engines.

http://www.rcignitions.com/

Milton

FLYPUCK

My Feedback: (8)

Anyone have a suitable piece of G10 they would be willing to sell? I am quickly finding out that no one is making these adaptors anymore. CH is considering it in the future but have no current plans to supply them. Unless I can come up with something, this fine running engine is just a paper weight[&o]

Thanks

APLANEGUY

Just wanted to throw this link out there. I'm considering converting a Poulan 46cc and have found this forum very informative so far. As stated above brillelli.com is gone but I found this site when doing some searching for conversion parts: brillellicustoms.com. Seems they've taken over where the other left off. Thought it might be helpful to some out there. I haven't yet decided if I'll be fabricating everything myself or maybe buying some of the pieces...

Pete