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  #211  
Old 01-23-2019, 01:02 PM
12vaitor 12vaitor is offline
 
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From some research I did a couple of years ago for my Viking 110, the "Torsional Damper" is a SGF GAB01-017 Drive Shaft Flex Disc used on a BMW 525i E39. The original one-piece disk is cut in thirds, midway between the thicker cross-sections for the six bushings. You can see the internal construction in the SGF Flex coupling in the following document.

https://www.sgf.de/tl_files/theme/pd...0couplings.pdf

I presume this is a custom part for BMW as it is not listed in the SGF catalog.

It appears the flex disk was used as a one piece unit at some point and then sectioned into three pieces to address a problem. I suspect the problem may have to do with the drive pins (flywheel side) and driven pins (gearbox side) not being parallel or spaced precisely to distribute the load equally. I recently changed the aluminum flywheel to a steel one and replaced both the flywheel side and gearbox side pins. Installing the flex coupling as a one piece unit found some binding on a couple of pins, that goes away with the sectioned coupling parts. There is an installation note to make sure the flex coupling sections are installed to keep the gearbox side drive in tension as the engine rotates.

John Salak
RV12 N896HS
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  #212  
Old 01-23-2019, 08:30 PM
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charosenz charosenz is offline
 
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Johns post is correct. But just to clarify, individuals are not cutting these up in the field. The ones that Viking sells is sectioned, as John describes. As always it is up to the individuals whether they want to use the disc whole, or as Viking supplies, sectioned.

These are used in most of 300-500 series BMW drive shafts, and many other vehicles as well.

As far as the "why does he section them"...that would be something Viking should answer.

Charlie

Last edited by charosenz : 01-23-2019 at 08:32 PM.
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  #213  
Old 01-24-2019, 09:57 AM
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Piper J3 Piper J3 is offline
 
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I'm following this thread with great interest. Thanks...
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  #214  
Old 01-24-2019, 11:13 AM
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rv6ejguy rv6ejguy is offline
 
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A couple guys have reported failures at low hours of these parts on earlier Viking drives, not sure if the present part is the same as on the earlier version.

Cutting something like this doesn't sound like a good idea or being based on any science or recommendations from the manufacturer.

Redrive makers should really invest in the proper equipment to test for TV and use appropriate means to fix any concerns which show up.
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  #215  
Old 01-24-2019, 08:39 PM
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charosenz charosenz is offline
 
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I am not familiar with any failures, or even problems with the flex discs. Ross, please post here what you have heard. It would be of interest to me and I am sure others.

I am pretty active on the Zenith forum where a lot of folks are using the Viking engines and redrives. That forum is not controlled by Viking and hence people are free to post info, including complaints or troubles. The only troubles I have read about that I can remember seeing is relating to the issue of venting. I know Viking did experience some high oil temps on the gearbox when they mounted the redrive on the turbo charged engine. That caused them to create a new HD "Turbo" unit that has larger bearings and an improved venting system.

I personally don't "see" a need to section the guibo. The un-cut disc I use slips on and mates the engine and the redrive nicely.

I think it is good to look hard at the unit, the redirve, the flex disc, etc.

The only thing I would ask is that before we go down the path of "Looks good to me" or "You should not do that" or "I would not do that" I
respectfully ask that critical statements be coupled with the person posting the critique what their level of training, experience or education is. It really helps all of us as we contemplate the advice.

Make sense?

Thanks.

Charlie

Last edited by charosenz : 01-24-2019 at 09:07 PM.
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  #216  
Old 01-24-2019, 08:40 PM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by Piper J3 View Post
I'm following this thread with great interest. Thanks...
Welcome to the party. It is a good group, IMHO, who are willing to ask questions, offer advice and respectfully debate the merits of the project. There are many encouraging words of support as well.

Charlie
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  #217  
Old 01-24-2019, 09:38 PM
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rv6ejguy rv6ejguy is offline
 
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I recall getting an email from someone with a 110 who had 2 failures in less than 40 hours a few years back. I'll search my emails at work Friday but likely been dumped by now.

Does Jan say how he tests his drives or what led him to recommend these mods to the coupler? Unless he can tell you something based on facts and testing, this sounds like a shot in the dark.

Seriously, anyone making and selling drives to customers needs to have a proper test program in place, not relying on customers to find issues because insufficient engineering and testing went into it to begin with.

Yes, we know these are experimental parts at Experimental prices and it's up to the user to decide if it's a good idea to use them. I hope your experience with the drive is good and above all, safe.

I'd be interested in your observations of any signs of TV in the 500 to 1500 rpm range.
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  #218  
Old 01-24-2019, 10:25 PM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
I recall getting an email from someone with a 110 who had 2 failures in less than 40 hours a few years back. I'll search my emails at work Friday but likely been dumped by now.

Does Jan say how he tests his drives or what led him to recommend these mods to the coupler? Unless he can tell you something based on facts and testing, this sounds like a shot in the dark.

Seriously, anyone making and selling drives to customers needs to have a proper test program in place, not relying on customers to find issues because insufficient engineering and testing went into it to begin with.

Yes, we know these are experimental parts at Experimental prices and it's up to the user to decide if it's a good idea to use them. I hope your experience with the drive is good and above all, safe.

I'd be interested in your observations of any signs of TV in the 500 to 1500 rpm range.
Ross, I will ask Jan about testing he has done that prompted him to cut the disc. I agree, it seems counter intuitive at best. Like Dan said, it certainly goes against what SGF designed. That said, I just have not heard of any issues.

Dan share with us if you get the Newton Meter ratings on the GAB01-017. For the sake of the topic, this particular model has a 96mm bolt circle, with 12mm lugs and it is 30 mm thick. There are other discs with the same bolt circle and lug diameter that are thicker. I presume they have more -strength. The thicker discs are used in more powerful and heavier vehicles, i.e. the Cadillac CTS, etc. One of the more comprehensive lists of discs can be found at

https://www.powertrainindustries.com...ber+Flex+Discs

For those who want to look deeper in to the "cut" disc topic Viking has videos on their website and on youtube where they describe this in their own words. Better you see it and hear it from Viking direct than from me.

As far as my own experiences, I only have probably 30-40 hours on the test stand. I have ran it up to 5000 rpm many times (that was really fun for my neighbors) and I did not notice harmonics from my anecdotal observations. But in fairness I was not directing my attention to this. I was more focused on nailed the programming values of the ECU.

I also want to state that what I experience with my set up may not be representative with what anyone else may experience. I moved my alternator over to the other side of the engine to balance out the weight with the turbo. That along with the prop extension and prop will create its own unique pattern of frequencies. I am open minded that it may turn out great, and it may not. So far I am very pleased with the performance. once the migration to the airframe is complete and functional. I will move on to purchasing a larger prop ( IVO MAGNUM 74" 3 Blade?) so I can work the engine harder. The 3 bladed 68" warp is a great prop, but it does not seem to be enough to really work the engine.

Charlie

Last edited by charosenz : 01-24-2019 at 10:29 PM.
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  #219  
Old 01-24-2019, 11:53 PM
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Major-Tom Major-Tom is offline
 
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Charlie, you sad earlier that the Viking Gearbox was almost a straight fit. 3 holes lined up excactly and one not. Was it the upper right point (frontview) that needed a little adapter?
And to add one more stupid question... Would you imagine it possible to bolt lycoming style mounting ears to the R18 and use the original Vans engine mount?
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  #220  
Old 01-25-2019, 10:09 AM
BillL BillL is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
Seriously, anyone making and selling drives to customers needs to have a proper test program in place, not relying on customers to find issues because insufficient engineering and testing went into it to begin with.
+1, this is especially important (essential) for torsionals. Many times there is no external indication of trouble until parts escape their enclosure.
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