Jan,

I often get questions about why the rubber disc is cut, and I suspect other builders do as well.  Most question why anyone would cut up a disc that was not designed to be cut up.   Seems like a fair question and one that I cannot answer. 

Can you share with us in more detail what lead you to do this?    Did you have any engineering done, and if so are you willing to share it?  Were there issues with the discs when they were whole?   Were there early problems that cased you to cut the discs in parts?

Thanks. 

P.S.  Even though I have not installed the new HD Turbo gearbox, I am very impressed with the new design.

Charlie 

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Can you provide a little more detail on the rubber disc, for us not familiar with this item.

Charles, do you have any photo's of what you're taking about?

My apologies I should have explained this more.

I am referring to the rubber disc that connects the engine to the gearbox. Commonly called a "guibo", or "Flex disc".

This must be the rubber coupling you are talking about?  Funny, many people have viewed our builders page (over 100) and not one person has ever asked about the rubber coupling.  I don't see a problem with it myself, but in any event maybe Jan will find the time to discuss.

No photo description available.

yes, that is the piece.   I active on the Vans airforce net and several have asked me to explain why Jan cuts up the disc knowing it was made to be installed as a whole piece. i don't know the answer to this so I thought I would ask Jan to post the answers here for others can benefit too. 

The other group said they hear of early failures of these parts and have not heard of any problems at all, has anyone else?

Charlie 

Don't look up "Flex disc" on the internet.

Of course we're going to google it after being told not to.   Hilarious, first thing that pops up is what's used by women where the sun does not shine.

This is completely speculative, but to me also, it looks like a coupling that would go inside some receptacle. With relative movement, the pauls or dogs will rotate pushing against the ID of this receptacle arresting the relative movement. Why the mounting ring is split, could be design, but it looks to me like you might need a new one.

Even if Viking repurposed the rubber coupling to fit their use by cutting it into three sections, what exactly is the downside?  

It would be good to learn more about this from Jan.  Hope he can post the info here.  I will try to connect with him on the Viking site.    

Charlie 

These couplings come in all sizes.  They are also copied by aftermarket replacement part manufacturers.  An OEM BMW or Mercedes part cost about $250.  A Chinese made copy, as little as $20.

Viking only use the OEM part and modify it according to the torsional damping required by a particular engine / gearbox / propeller combination.   

Jan, Thanks for the follow up. There has been some interest in knowing if there was any engineering done that led up to cutting the discs. and if so, if you could share that with us? I.E. what kinds of test were done? Was there some troubling results with the disc left whole? I have always appreciated how much you are willing to share the details of your work, and I look forward to learning more about any testings you have done.  

Thanks. 

Charlie 

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