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Kick-back: the ultimate solution?

 
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air.guerner(at)orange.fr
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PostPosted: Tue Dec 14, 2010 3:00 am    Post subject: Kick-back: the ultimate solution? Reply with quote
Hi all,I am the unlucky owner of an engine (912ULS) which is prone to kick back on cold starts. During the 6 years and 500 hours of operation I have tried EVERYTHING suggested by the Rotax factory, Rotax distributors worldwide and operators writing on this forum, including the SoftStart module from Conair. All these alleged solutions have had some positive effect such as a reduced occurence of the kick-back and a less violent one, but none of them, even when combined together, managed to withdraw the kick-back completely.
Now the good news is that Rotax has introduced (at last!) new ignition modules and a new flywheel hub to fix this problem (see SI-912-020 R3). The new ignition modules do exactly what the SoftStart does: they prevent the ignition timing to switch to the 26 degree before TDC as long as the starter motor is activated. In fact the switching to 26 degrees occurs a few seconds after the starter button is released. The new flywheel hub (see attached drawing) features extended trigger cams giving a 3 degrees after TDC ignition timing during the cranking phase instead of 4 degrees before TDC. Obviously the engine cannot kick back as long as the ignition happens after TDC, so I strongly believe this change is a radical solution to the kick-back problem. I do not need the new ignition modules as I already have the SoftStart. So I will replace the flywheel hub only.
Here are my questions:
1. The price of the new flywheel hub is 315 Euros, French VAT included. To avoid spending that amount, I am thinking at modifying the existing hub. I would weld a 7 millimeter extension to the trigger cam trailing edge and machine it on a lathe or adjust it with a file. It is not necessary to modify both cams as only one is used with the SoftStart module, the other one being inactive during the cranking phase. Does anyone know what material (presumably a variety of ferromagnetic steel) the hub is made of? Any suggestion on how to do this cam extension?
2. Removing the flywheel hub is very easy, even without removing the engine from the aircraft. But a special tool is needed to extract the hub from the crankshaft tapered end. This tool (Rotax P/N 877377) cost 76 Euros VAT included. This is not very expensive but is too much for a tool I intend to use only once! Does any one have this tool available and would lend it to me? Are there many other owners who want to do this mod? If yes we could ask the Europa Club to purchase the tool for use by the members.
Waiting for your answers
Regards
Remi Guerner
F-PGKL


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kheindl(at)msn.com
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PostPosted: Tue Dec 14, 2010 5:06 am    Post subject: Kick-back: the ultimate solution? Reply with quote
Hi Remi,

That is very good information, but I can only find SI-912-20 R4, a 25 page bulletin, including some of R3. There is no mention of the flywheel. The Rotax website does not have a search facility. 
Karl

From: air.guerner(at)orange.fr
Subject: Europa-List: Kick-back: the ultimate solution?
Date: Tue, 14 Dec 2010 11:55:43 +0100
To: europa-list(at)matronics.com

Hi all,I am the unlucky owner of an engine (912ULS) which is prone to kick back on cold starts. During the 6 years and 500 hours of operation I have tried EVERYTHING suggested by the Rotax factory, Rotax distributors worldwide and operators writing on this forum, including the SoftStart module from Conair. All these alleged solutions have had some positive effect such as a reduced occurence of the kick-back and a less violent one, but none of them, even when combined together, managed to withdraw the kick-back completely.
Now the good news is that Rotax has introduced (at last!) new ignition modules and a new flywheel hub to fix this problem (see SI-912-020 R3). The new ignition modules do exactly what the SoftStart does: they prevent the ignition timing to switch to the 26 degree before TDC as long as the starter motor is activated. In fact the switching to 26 degrees occurs a few seconds after the starter button is released. The new flywheel hub (see attached drawing)  features extended trigger cams giving a 3 degrees after TDC ignition timing during the cranking phase instead of 4 degrees before TDC.  Obviously the engine cannot kick back as long as the ignition happens after TDC, so I strongly believe this change is a radical solution to the kick-back problem. I do not need the new ignition modules as I already have the SoftStart. So I will replace the flywheel hub only.
Here are my questions:
1. The price of the new flywheel hub is 315 Euros, French VAT included. To avoid spending that amount, I am thinking at modifying the existing hub. I would  weld a 7 millimeter extension to the trigger cam trailing edge and machine it on a lathe or adjust it with a file. It is not necessary to modify both cams as only one is used with the SoftStart module, the other one being inactive during the cranking phase. Does anyone know what material (presumably a variety of ferromagnetic steel) the hub is made of?  Any suggestion on how to do this cam extension?
2. Removing the flywheel hub is very easy, even without removing the engine from the aircraft. But a special tool is needed to extract the hub from the crankshaft tapered end. This tool (Rotax P/N 877377) cost 76 Euros VAT included. This is not very expensive but is too much for a tool I intend to use only once! Does any one have this tool available and would lend it to me? Are there many other owners who want to do this mod? If yes we could ask the Europa Club to purchase the tool for use by the members.
Waiting for your answers
Regards
Remi Guerner
F-PGKL


[img]cid:DCCFCDD1-EFA6-4C5D-BDDA-4B2FC1622FC3[/img]

- The Matronics Europa-List Email Forum -
 

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Remi Guerner



Joined: 14 Dec 2010
Posts: 284
PostPosted: Tue Dec 14, 2010 1:39 pm    Post subject: Re: Kick-back: the ultimate solution? Reply with quote
Hi Karl,
Look carefully at section 74-00-00 of the SI-912-020 R4. Page 1 of this section mentions the new fly wheel hub and its timing characteristics. Page 4 shows the drawing I attached to my previous e-mail. Pages 1 to 3 of this section are in fact Rev 3, but I was not aware of this R3 until R4 was published on December 12. May be R3 has never been published !
Regards
Remi

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kheindl(at)msn.com
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PostPosted: Tue Dec 14, 2010 4:32 pm    Post subject: Kick-back: the ultimate solution? Reply with quote
Remi,

Many thanks for clarifying this. I have got it printed off now, and I am very interested in this mod.  Please let us know the outcome whenever you get it done.
Cheers,
Karl
Quote:
Subject: Re: Kick-back: the ultimate solution?
From: air.guerner(at)orange.fr
Date: Tue, 14 Dec 2010 13:39:02 -0800
To: europa-list(at)matronics.com

--> Europa-List message posted by: "Remi Guerner" <air.guerner(at)orange.fr>

Hi Karl,
Look carefully at section 74-00-00 of the SI-912-020 R4. Page 1 of this section mentions the new fly wheel hub and its timing characteristics. Page 4 shows the drawing I attached to my previous e-mail. Pages 1 to 3 of this section are in fact Rev 3, but I was not aware of this R3 until R4 was published on December 12. May be R3 has never been published !
Regards
Remi




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