Split coupling?

[Figment]

I'm replacing my propshaft this year for a handful of reasons, so it didn't break my heart to just cut it behind the coupling for easier removal. Previous removals have been far less pleasant, going through the usual routine of pressing the shaft out of the coupling with shim after shim, all working via the typical horrible access.

I can't help but think that things would be a LOT easier in the future with a split coupling.

Are split couplings available for such small (7/8") shafts, or is it just not worth the trouble?

[bcooke]

Horrible access problem solved.



-Britton

[Figment]

oh goody, a stalker.

[JOLLYBOAT]

figment - howdy, you may have heard that am the proud owner of an A-4 again. Anywho, I am sure that you can get a split coupler for a 7/8 shaft.
Have you contacted, S and S machine or Essex Machine yet.

[marthur]

Hey guys, what is a split coupling?

[JOLLYBOAT]

A coupler is the hardware device on the shaft that allows the final drive on the gear box to connect to the shaft. Most couplers are keyed and slide onto the shaft and are then pinned with set screws. After a while a coupler can weld itself to a shaft via corrosion. A split coupler is comprised of two halfs, length wise, that can be separated with the split connecting hardware removed. The fact that a split coupler can in fact split makes them very easy to install and remove without the use of a puller - especially in small spaces like that of a Triton's stuffing box area for example.

[Figment]

Yes, a split coupling is a coupling made in two halves which bolt together over the shaft, vs. a solid coupling which has the shaft pressed into it.


It has occurred to me that the problem with a split coupling on an A4 may not be the small shaft, but may be the three-bolt pattern. The more I think about it the more I realize that all the split couplings I've seen have been 4-bolt.

No of course I haven't discussed the issue with any actual machine shops yet. That would be research. ugh.

[msmith10]

I wouldn't think there would be a problem with drilling 2 additional holes in the split coupling you show, permitting it to mount to the A4. I'm not an engineer, but I doubt if it would weaken the flange enough to cause harm. If you were worried about it, you could have the 3 holes you weren't using plugged with either a weld or tapped and filled with threaded inserts

[Chip Hindes]

The problem with drilling only two additional holes is that they would create an assymmetrical hole pattern which would unbalance the rotating coupling. At the low speed of the A4 this might not be a problem, but personally I wouldn't risk it.

The only way to create a symmtrical bolt pattern with the existing holes would be to do a 12-bolt pattern: eight additional holes. This is not a particularly highly stressed part of the coupling and I don't think even the swiss cheese nature of this solution would be a problem, strength wise.

That's a whole bunch of extra holes. The suggestion to tap and plug three of the existing holes seems a workable solution as well. That won't do much all for structural strength, only balance; also note that the minimum web thickness between adjacent holes is the same for four plus two as it is for twelve holes. If you use this method, fix the plugs in place with Loctite and grind them flush to the flange.

Any machine shop or even a reasonably skilled amateur with access to a drill press ought to be able to handle either of these.

I would avoid welding because of the possibility of warping, unless you're prepared for the possibility of subsequent heat treat and remachining.

[MikeB.330]

Atomic 4 engine with gear reduction have a 4 hole coupling. I wonder if one could simply swap the tail pieces?

Mike

[Don Moyer]

Mike,

The four-bolt output coupling of gear reduction units is much larger than the direct drive coupling, so it would not fit on a direct drive engine. For whatever it's worth, our prop shaft coupling manufacturer is currently making us a prototype of a split prop shaft coupling which we'll "air" as soon as we receive it.

Don

[Bob Wine]

I would be happy if I could find a replacement coupling (1") for my V-drive. Moyer parts dept. says they don't carry. Anyone know where I could find one?

Thanks,

Bob

[tenders]

I purchased a "blank" coupling about ten years ago for my V-drive (3-hole pattern) from Walter Machinery in Jersey City, NJ.

"Blank" means the flange had three bolt holes in it, but the coupler had no hole for the shaft at all. The machine shop that made my 3/4" shaft bored (drilled) and broached (cut the keyway slot) into the coupling itself. They may have cut the hole for the set screw, too. Technically I believe the broaching operation was a "blind broach" although I don't know what was blind about it; obviously you can see all the way through the coupling.

Why do you need a new coupling? They clean up quite well, however rusty they may appear.

PS: Walter is still around: http://www.waltergear.com/
The A-4 coupling may not be a stock item.

[lat 64]

I have a reduction drive; I got one(coupling) for my boat at:
getaprop.com
301 30th Street
Anacortes WA 98221
UNITED STATES
360 299-8266
http://getaprop.com

Paragon Split Coupling 4"S -
Shaft Size: 1"
Flange Diameter:4" Bolt Diameter:3/8" $76.12
Shipping $14.32
Total: $90.44

They only sell a solid one for Atomic four direct drive.

For the future reference, a solid coupling was not too hard to cut off. I used a sawsall to cut the old rusty one lengthwise. It was not that hard to do with the engine out. I split it right over the brass shaft key so that when it cut through I didn't hit the shaft; just the brass key.
Then I cut from the opposite side , but stopped cutting 1/16" before I hit the shaft and then just cracked it open like a walnut.

As far as unbalancing the unit with new holes; I would not even worry. That close to the center of the circle of rotation, and just a few grams of missing metal, at 2,000 rpm is just not a big deal. For some perspective, old Mercedes diesel engines had a tolerance of around eight or nine grams on the piston connecting rods. Those were rated at around 4,500 rpm.

If you need to balance it, just put one or two hose clamps on the naked part of the shaft. position the screw on the same side as the missing metal.

Good luck,
Russ

[m_galligan]

For Bob Wine,

Fill out the profile on the bulletin board, so we can tell where you are.

Local to me, two places likely to have the coupling are Rose's Oil in Gloucester, MA, and H&H Propeller in Salem, MA.

-Marty