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miami_guy
Joined: 10 Jan 2007
Posts: 6
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jetboy
Joined: 22 Jul 2006
Posts: 233
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 Posted: Wed May 14, 2008 1:14 am Post subject: Re: Gearbox with no overload clutch..... |
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There is a preload test for the "dog clutch" which requires locking of the crankshaft with a pin threaded into a hole on the side of the crankcase nose. Then prop is pulled with tension scales to determine if the slip torque is within spec. over the play range of the dog (15 degrees or 30 degrees for the later ones) I have helped do this test and the clutch was replaced, it is a separate item from the optional slipper clutch and all 912 boxes should have one, despite what I'm told by some. If this part has got slack, starting the engine may become difficult.
Ralph
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Ralph - CH701 / 2200a |
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peter.rees01(at)tiscali.c
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| Posted: Wed May 14, 2008 1:46 am Post subject: Gearbox with no overload clutch..... |
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I think that this test is titled 'Torsional Vibration Damper' in the
rotax manual. Rotax current recomendation for this parameter is (from
memory) 400 inch pounds. Ours was down to 200 and as Ralph suggested,
we had starting problems (which mullered the Sprag Clutch). The test
is very simple to do - if yours is low, gearbox has to come off and a
shim fitted - cheap to do, expensive not to do!
Peter
----Original Message----
From: sanson.r(at)xtra.co.nz
Date: 14/05/2008 10:14
To: <rotaxengines-list(at)matronics.com>
Subj: Re: Gearbox with no overload clutch.....
nz>
There is a preload test for the "dog clutch" which requires locking of
the crankshaft with a pin threaded into a hole on the side of the
crankcase nose. Then prop is pulled with tension scales to determine if
the slip torque is within spec. over the play range of the dog (15
degrees or 30 degrees for the later ones) I have helped do this test
and the clutch was replaced, it is a separate item from the optional
slipper clutch and all 912 boxes should have one, despite what I'm told
by some. If this part has got slack, starting the engine may become
difficult.
Ralph
--------
Ralph - CH701 / 2200a
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=183069#183069
_______________________________
Free games from Tiscali Play - http://www.tiscali.co.uk/play
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Wed May 14, 2008 4:48 am Post subject: Re: Gearbox with no overload clutch..... |
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The 912UL gearbox does not normally come with the overload (slipper) clutch but can be fitted with one. All the 912ULS gearboxes do have this clutch, at least those sold in recent years. See attached introduction which came from the Rotax 912 Line Maintenance Manual. The procedure is described after this introduction.
In April we did the annual inspection on a Diamond Katana with 912F3 engine. This is the 80 hp certified engine with constant speed prop and gearbox with the slipper clutch. We did the friction torque test (slipper clutch equipped gearboxes only) per the maintenance instructions but used a known weight at the proper distance from the prop center on a horizontal prop blade to determine if the slipper clutch was within specs, and it was. You don't need a spring scale which may or may not be accurate. If you use my method, make sure the prop blade is close to horizontal. If the first crank lock position does not give you this keep turning the prop until you find a crank lock position that does give you close to horizontal. The test is very simple and quick but applies only to gearboxes with slipper clutches.
Our Allegro has a 912UL engine without the slipper clutch. Rotax states that the gearbox internal inspection is to be carried out on gearboxes without slipper clutches at 400 hour intervals. Gearboxes with the slipper clutch are supposed to be inspected at 600 hour intervals. If yours needs inspection, let me know. I'm set up to do gearbox inspections and I'm cheaper than Lockwood.
Thom Riddle
Power Plant Mechanic
KBQR
Buffalo, NY
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| Gearbox maintenance introduction |
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