Engine Mounts and Flexible Coupling

[Vic Suben]

Has anyone had experience installing engine mounts and a flexible coupling from R&D Marine?  If so, what were the problems/benefits, etc. with the installation and use of their systems.

Thanks,

Vic Suben
Surprise, C-34 Hull 453

[Ron Hill]

Vic : I've written a few Mainsheet articles on both.  MANY posts on this Message Board on engine mounts, both the K50s & K75s.
I installed Vetus mounts, a Vetus flexable coupling on the old engine and an R&D coupling with my new engine.  I like the R&D coupling and it's a straight fwd installation.  
Don't know what you're looking for, .... so!?  

[David Sanner]

Ron,  so you've tried both... does the R&D reduce vibration
as well as the Vetus?  (I tried to find your Mainsheet article
on the R&D but no luck)

I have K75 engine mounts and more vibration that I would
like at, especially at a couple rpm ranges, with my 2 blade
folder.

Planning on shortening the shaft to remove some of the excess space
aft of the strut to help with vibration but thinking it might make
sense to only make one cut and add some some sort of flexible
couple at the same time. (Though I may not have enough key
left to do this and be forced to use the Bullflex).


The Bullflex is around $500... the R&D are closer to $150.

[Vic Suben]

From the literature, it appears that the R&D coupling uses the same flange that  currently holds the prop shaft.  In the Vetus literature it appears that their coupling replaces the flange on the drive shaft.  I would rather not cut the shaft.  So please let me know if my reading of the vendors' literature is correct.

Also, any idea whether the R&D engine mounts are better vibration dampers than the Vetus?

Thanks,

[Ed Shankle]

Ron,
What influenced you to try the R&D coupling this time?  Seems from passed years' posts you were advocating the benefits of the Bullflex. Did you run out of room with the new engine?

thanks,
Ed

[David Sanner]

Vic, I think with either coupling you'll need to cut the shaft otherwise
you'll have too much space between the propeller and the strut.
(ideal spacing about 1/2 inch)

Here's a project page for installing the BullFlex
[wiki]Flexible_Coupling_Installation[/wiki]

[Ron Hill]

David & Guys : Ed hit the nail on the head, with the new engine (longer M25XPB + longer Xmission ZF10/Hurth100), I had to get a R&D coupling as I needed a "two part" (in length) coupling - because I ran out of space between the packing gland and the rear of the Xmission.

I had/still have the Uniflex Vetus coupling (in the attic) which works great which I installed (M25XPA w/Hurth 50) in the water without cutting the shaft and it works great.  A few thoughts

[Ron Hill]

Vic : On the R&D coupling you must remove the hard coupling as the R&D attaches directly to the transmission.  It seems to do as good a job as my Uniflex Vetus as far as vibration.  The only draw back that I've seen so far is that the R&D metal is NOT stainless and I'm glad that I sprayed it with BO-7.
The Vetus Uniflex is some kind of alloy that doesn't rust!! 

David : The rule of thumb for the prop distance behind the strut is "one shaft diameter" or in the C34s case = 1 inch.  I put mine at 3/4". 

A few thoughts

[David Sanner]

I've heard that the spacing should be no more
than 1/2 the shaft diameter or in our case 1/2"
... rules of thumb ...  3/4" sounds fine to me as well.


My old three blade was set closer than that and with a bent
blade I had no vibration.   When the prop shop setup my new
SS shaft I wound up with a spacing a bit over 1.25 inches and I noticed
more vibration even though the propeller had just been balanced.

When I put on my folding prop the spacing was nearly 2 inches.  Considering
the  center  of mass on my folder is probably a couple inches further aft
(and a good bit more mass as well) I think shortening things up
an inch or more will help. 

My next haul is in six months so I'll find out then.

Either way I'm a big fan of my 2 blade folder, boat
sails much better and with the larger and thicker
blades even powers better.

[Ron Hill]

Guys, Susan and D.Gill : Just make sure the there is some space between the front of the prop hub and the aft portion of the strut.  The cutless bearing is lubricated by water so don't cut off that flow.
 
Again the rule of thumb is "one shaft diameter" and as David pointed out the further aft of the strut the prop is mounted the more vibration and wear on the cutless.  A few thoughts

[Roc]

The Federal Flexible coupling, which is a true flexible coupling, is in this post.  However I can't figure out where the picture is.  It's not in the post anymore.


http://c34.org/bbs/index.php/topic,625.msg2540.html#msg2540

[Stu Jackson]

The photo disappeared because it was from the way old message board which at the time, as Bob Kuba explained on one of the posts in that topic, you needed to "link" it to a photo on a website.  Those requirements don't apply anymore, you can directly upload photos under "Additional Options" when you post.

If you still have the photo on your computer, just upload it here.