Thursday, July 2, 2009

Hands On: Holt Nautos XR Clutch


New from Holt Nautos is their line of XR rope clutches. It's available in two sizes and features an innovative double action cam system that offers greater leverage for both opening and closing the clutch. Both sizes (creatively named the XR1 & XR2) are available in singles, doubles, triples, and quads. Here are the basic specs for these clutches:

ClutchLine Diam.SWLHole SpacingWeight
XR11/4" - 1/2" (6 - 12 mm) 1,653 lbs (750 kgs)3 - 1/8" (79 mm)13.3 oz
XR23/8" - 9/16" (10 - 14 mm)2,645 lbs (1,200 kgs)2 - 3/4" (70 mm)1 lb 4.9 oz

Looking at the specs, the first nice feature of these clutches is that Holt matched the hole spacing on the XR to that of the comparable Spinlock clutch. So, the Spinlock XAS matches up with the Holt XR1 and the Spinlock XTS matches up with the Holt XR2 -- by doing this, it's really no problem to swap out an old Spinlock for one of the new Holt clutches. Replacing a Lewmar clutch is possible with their smaller D1 clutch as the XR1 matches up, but the hole spacing is different between the larger D2 and the XR2.

Both the Holt XR and the Spinlock XAS and XTS clutches use a similar cam system to jam and hold the line (the Lewmar D1 & D2 both use a "falling" domino system); however, the manner in which the cam pivots up and down is where the Holt clutch looks to carve its niche'. The Holt clutches feature a unique double-action cam system that provides more leverage for the user to release the clutch under load.


Here's a rundown of how the Holt Nautos XR works, referencing the image above:
Position #1: The clutch is closed and locked.
Position #2: The handle has been lifted but the clutch is still engaged - it's from this position that you gain your leverage to throw the handle forward.
Position #3: You can see the handle is vertical but the cam is still mostly in the down position. It is at this stage that the line will release under serious load but not under light loading.
Position #4: The clutch is fully open and the line slides through easily.

One thing that we did notice was that the line will run in Position #3. When testing the XR clutches, we mounted them to our rigging bench and loaded up a line with a 6 : 1 purchase system. With the purchase system loaded up, we opened the clutch to Position #3. This caused the the line to jump forward by about a foot, causing the purchase system to go slack. When we tensioned the system up again, the line continued to slowly drag through indicating that the line would be on the run if it was constantly loaded.


Functionally, these Holt clutches operate with cam system similar to the Spinlock -- both rely on a pivoting cam on the top and a fixed plate on the bottom of the clutch. You can see in the picture above the two cam surfaces and the insides of the XR1 clutch. Both clutches are easily disassembled by removing the 5 bolts holding them together. The clutches can also be side mounted by using longer bolts in those same holes - the bolt holes have raised edges to allow the clutch body to sit flat against a deck so no extra parts or adapters are needed.

While doing a little initial research the XR, I called and asked the folks at Holt Nautos for a little history/inside information about the development of the XR clutch. They basically said that a lot of time was put into engineering a clutch that would be kind on the rope while providing solid holding power. In other obvious news, the Earth is round and blondes really do have more fun...

Anyways, the Holt XR clutch goes about accomplishing these goals in two different ways. First, the upper cam on the XR2 is channeled to provide better grip without point loading the top of the line. It should be noted that the XR1 has a standard, non-channeled cam -- the loads are lower and lines are smaller on the XR1, so the concern of point loading is slightly reduced.

The other "line friendly" feature of the XR clutch is the double action of the cam, as it greatly reduces line slip when it's initially loaded. But... there's a catch. To take full advantage of this feature, you have to "double pump" the clutch handle when closing it to get the maximum hold out of the cam. The "double pump" causes the cam, which rotated down at an angle, to lift up just a little bit when you move the handle back up. When you put the handle back down, it drops the cam down vertically, reducing the cam set that occurs when the line is loaded up. Since it's a little hard to explain, I've illustrated what I mean below:


So, when I tested both the XR1 and XR2 clutches using 5/16" Paraloc Pihrana line, I loaded it with the 6:1 purchase we had set up. When you first close the XR clutch from Position #1 to Position #3 you can see that the cam pivots from the upright position all the way down to the closed position. When in Position #3 we found that, on average, the line slipped about 5/16 of an inch on both the XR1 and XR2 when it was loaded up.

Again, this is pretty common on cam clutches, because the force of closing the clutch never loads and fully rotates the cam -- the cam only fully loads and rotates when the line loads up, causing the cam to rotate down and back even further before getting a firm hold. While the cam is rotating to its full grip position, the line is allowed to slip.

However, when the clutch was given an extra pump of the handle (Position #4) and is then closed again (Position #5), the cam lifted up, rotated backwards and came back down in its fully loaded position. This elimated the time where the line is allowed to slip while the cam sets and thus line slipage was reduced to only 1/8 of an inch on the XR2 and 1/16 of an inch on the XR1.

This really is the biggest advantage offered by the Holt XR clutches. When tailing your jib halyard you can close the clutch to Position #3, winch it up to where you want it, do the "second pump" and then take the halyard off the winch and be confident it's going to stay there.

So, in short what do we think?
The Good
The ability to prevent halyard slip when initially loaded is a new idea - in my experience cam style Spinlock clutches will always slip a bit when the line loads up. Obviously we're not talking about a lot but I've certainly had times when I forget about that fact and then have to grind it up a bit more.

I also think the opening mechanism does offer increased leverage in comparison to other clutches. Position #2 in either diagram presents you with a solid surface to get some force into opening the clutch.

The Bad
I'm not 100% sold on the double-action opening system. You could really chew a halyard up if you only opened the clutch to Position #3 in either diagram, as we noted that the line will start to run if its loaded.

More importantly though, I have concerns about the handle locks. On the XR2 the handle locks down with the barely visible (look hard...) rounded nubs on the side of the handle tip and on the XR1 the handle locks into the little red plastic tab.

These handle locks are important because if the handle isn't locked down, the clutch may pop open if you tail a line through it. I was told by Holt Nautos that replacement parts are available, including that little red tab, which is good because I don't think that piece will last the life of the clutch.

Also, when the handle is locked down we found it difficult to open at weird angles, such as from an arms length and reaching behind our back (similar to the position a pit person would be in while trying to open a clutch from the rail in preparation for a rounding).

Testing Methods
We mounted both an XR1 and a XR2 to a 2 X 4 and put it in a vice on our rigging bench. We then put a line through the clutch and connected that to a 6 : 1 purchase. I do not have any measurements as to how much we loaded the lines using the purchase system since we don't have a load cell to measure that with. To measure the line slip I put tape on the line where it met the clutch and then pulled on the purchase as hard as I could and measured how far the tape moved from the clutch.

Since I don't know how much I was loading the line I do not know how close to the SWL of these clutches I was operating. I would imagine it was not more than half of the SWL. I also did not test the clutches at the outer edges of their line diameter range.


Conclusion
The new Holt XR clutches are, for the most part, similar to the Spinlock XAS and XTS models. They both are cam-based, operate similarly and share the same hole pattern. The Holt sets itself apart by offering the ability to reduce initial line slip. Additionaly, it should be kinder to lines and cause less wear -- but that can only be determined for certain with extended use and obviously varies greatly depending on how it's used, line material, etc.

If you're thinking about replacing your clutches, the Holt XR's have some pluses and minuses, just like any other clutch. Their upside is huge though, which is why I would certainly recommend using them. I can imagine that once your pit person gets used to them, they'll perform swimingly.

FYI - Holt has the clutches in-stock in the UK and we expect delivery of our stock within the next two weeks.

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