Saber 12-Hole 2.25 Extension on O-320

LarryT · #1 03-07-2010, 01:10 AM

I am confused about this installation with my new Catto prop - sure wish there was a drawing, but the Saber instructions are written only.

I only have time on the weekends. Of course I can call Sam on Monday but then will have to wait another week to do the work, which is the reason for this post.

First the Sensenich prop and extension was removed. I note that there are six drive lugs in the crank flange. Four protrude and two appear to be a slip fit.

I get that the counterbored holes in the extension are for the short bolts that attach the extension to the crankshaft flange.

Here is what I don't get: It seems like the counterbored holes should line up over the lugs in the crank flange. However the backside (crank mating side) hole diameter is too small. On the other hand, the holes that contain the threaded drive lug inserts to mate the propeller to the extension do have large enough diameter holes to fit over the crankshaft drive lugs.

Seems like either the drive lugs in the crankshaft flange have to be pressed back so they don't protrude or the diameter of the holes that contain the extension to crankshaft mounting bolts needs to be larger diameter on the crankshaft mating side of the extension. The former would result in the bolts carrying shear loads rather than the crankshaft drive lugs carrying them. The latter would mean the extension was not completely machined. The real answer is probably that I am clueless. Can someone please straighten me out?

corbinace · #2 03-07-2010, 10:04 AM

Not sure I have your problem 100 percent in focus but;

Is there a possibility that the front/prop drive lugs are pressed into the wrong set of holes? The second set of front holes are for crank bolt pass-through/installation, as you probably know, and should be lined up with the crank drive lugs.

You do for sure need the drive lugs on both flanges. No shear allowed here.

RickWoodall · #3 03-07-2010, 10:32 AM

Not sure this helps, but one bone head thing we had an issue with is figuring out that one one of the holes is bigger and it slips onto to the lug with the shoulder. Measure each hole on the extension, one is larger, find the lug with the shoulder and line it up...we were slow on that process, but got it figured out. Also, Saber is awesome at support, I emailed one day and he called me 5 minutes later and called again that night to ensure I was good. Cant beat that. Great product, great service.

LarryT · #4 03-07-2010, 03:28 PM

Measured the lug diameter and the hole diameters that I thought were the mating holes. I guess it is what the machinists in the shop referred to as a "honeymoon fit." Hopefully the true position tolerance for the location of the drive lugs and the true position location of the holes in the extension are very close to a perfect match.

Personally I find this installation somewhat nerve wracking. I now believe that the individual hole diameters match the drive lug ODs, but I am very nervous because I have no way to determine that the mating hole patterns are exact. It would be miserable to put a burr on the edge of a hole that was supposed to fit line-to-line with a drive lug.

Larry

LarryT · #5 03-07-2010, 11:18 PM

Installed all 3" bolts in extension. Very gradually tightened each bolt until the extension was finally seated. Glad i didn't bugger anything up. Whew!

Larry

pierre smith · #6 03-08-2010, 06:18 AM

....compared to brand 'X' from the Orient

You did remember the Loctite?

Best,

LarryT · #7 03-08-2010, 10:29 AM

I remembered the loctite. Bought a fresh tube.

Thank you for checking, Pierre.

I always read the directions, which is not to say I always understand them! There is an opportunity for the dirctions to be a little more explicit in this instance. It might be possible without gentle progressive tightening, for example, to get the extension cocked on the lugs and create a burr.

Larry