Today's Message Index:
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1. 07:26 AM - Re: props and engines (Roger Lee)
2. 07:42 AM - Re: props and engines (mikeperkins)
Message 1
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| Subject: | Re: props and engines |
Hi Ed,
Props, hubs, spacers and all the nuts and bolts forward of the prop flange are
not in balance. They all play a part and every prop assembly before going on a
plane should balanced. Everyone only thinks they should just check the prop,
but there is more attached to that prop. You can get a nice prop and wheel balancer
for about $125 and it is so easy to use a "Caveman could do it". I balance
everything in front of the prop flange except the spinner. They are all off.
You can use a standard washer on a bolt for the balance change. At the minimum
a full prop assembly should be static balanced. I also have a Dynamic balancer
that I use. I know most don't have a dynamic balancer, but you can seek out
someone who has one.
The other thing that causes these types of vibrations is a poor carb balance or
none at all. make sure the carbs are balanced. A lot of time on the gear box
(over 800 hrs) will cause this because the bellville washers become weak and the
friction torque on the gearbox gets low.
If you have questions you can call me.
Roger Lee
Tucson, AZ
520-574-1080
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Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center
520-574-1080
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=313697#313697
Message 2
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| Subject: | Re: props and engines |
As we've talked before, Ed, you might remember that I go back to the "Denny Days"
of '86-'87. I recall quite well that the entire reason Denny specified a three-blade
prop on the two-cylinder engines was to prevent harmonic vibration,
regardless of the gear ratio. Where there is vibration, there is also fatigue.
Minimizing vibration:
Static balance, checked with bearings and shaft on a bench, 1 gram
Pitch, checked with a protractor, 1/4 degree
Dynamic balance, checked with a dynamic balance instrument, zeroed
Static tracking, checked with a stick in the ground, 1/8" max
Dynamic tracking at RPM, checked visually by ground-running the engine, 1/8" max.
Carb balance, checked with a flowmeter. (I have one if you want to borrow it).
Mike Perkins
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=313700#313700
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