Microtraxion vs Roll’nLock: A Tale of Two Top Rope Solo Back-Up Devices

This post is for informational purposes only and is the result of my personal experiences. YMMV.

I thought I’d use the time to write this up while the weather is not cooperating for being out on the rock. Snow, ice, freezing rain and mud are not my cuppa tea! Hat’s off to all you folks who thrive on those conditions!

First some general info re the MT and R'nL. There is no significant difference in size/weight or feed on the rope. Both use a cam to lock on the rope against the pulley/bushing but they differ as to how they initiate the lock-up. The R’nL has sharp “V” cutout with ribs to grab the rope and initiate the pinching of the cam against the bushing, while the MT uses conical teeth to grab the rope to initiate the lock-up of the cam against the pulley. The MT has a sealed bearing inside the pulley. The R’nL just has a bushing inside the smaller diameter pulley which is integrated into the cam lobe. Both are rated with specs that are adequate for TRS as a primary or back-up device. When loaded onto a rope, the MT cam is completely enclosed inside the device while the cam on the R'nL sticks out below (a bit of a safety concern if the R'nL is used as a primary device above another device).

In my TRS rigs, I always use a MT or R'nL as a backup. Early on I found it a hassle to take either one off the rope to rap. I was seeking to optimize my system so I didn’t have to take the back-up off at the top of the route when doing laps. Both devices have lock-out modes so they can be held open and stay attached on the rope while sliding freely down the rope when rapping. The R’nL’s lock-out feature is extremely positive and hands free once locked out, though it often takes two hands to do that. (I previously devised a finger loop to allow one-handed operation for that: https://sicgrips.blogspot.com/.../rollnlock-as-tr-solo... )

The MT’s lock-out feature on the other hand, is finicky and less reliable in my experience. With the MT I’ve randomly experienced both locking-open and locking-on the rope when not wanted. (Could this be why Petzl removed the feature in the new Nano??? ) This could be a result of the size and condition of the ropes I was using but I was never able to isolate the issue. When rapping, it’s annoying to come to an abrupt and sudden stop when it unwontedly locks-on and bites down on the rope. Conversely, it is down right dangerous if it happens to lock-open when climbing and you weight the rope or take a “fall” and your primary device fails. Not likely but could be possible.

CAUTION: Any device that can be locked open is subject to user error by forgetting to lock it on the rope before climbing/after rapping. ALWAYS DOUBLE CHECK!

A solution for the MT's unpredictability, is to grind off the lock-out nub. Problem solved - at least for safer climbing. However, then the device can’t be locked-open for rapping and I'm forced to remove it from the rope. My solution is to add a simple thumb loop shown below. By this addition I insert thumb and pull up which manually opens the cam while grabbing the rope between the rappel device and the MT when rapping. This positions the hand in the perfect spot for tensioning the rope while rapping with a Lov2, Vergo, or GG or what-have-you. However, this is a manual operation and it is only unlocked while you’re holding it open with the thumb loop. This gives the added benefit of serving as a back-up (like an auto-block would) during the rappel.

The mod involves adding a thumb loop of accessory cord. I used 1.5 mm accessory to keep the knots as small as possible and out of the way. One end is fed down through the molded in hole in the plastic housing that is intended for an optional keeper cord (older MTs don't have this). A simple overhand knot neatly tucks out of the way in the knot pocket in the housing. The other end of the cord is fed through the hole at the end of the of the toothed cam. This can be secured simply with an over-hand knot that acts as a stopper knot like the other end. However, I’ve chosen to use a Scaffold knot which centers it and keeps it out of the way on the backside of the cam. It took me a bit of experimenting to get the loop exactly the right length for my hand, trying to keep it as small as possible but still be able to easily slip my thumb in and out and be able to grab the free rope strand.

For me, the beauty of this mod is when using it as a backup for the Lov2 or Vergo, at the top of route; whenever I “fall”; or, any place I want to work a move; I simply hang on the primary device, insert thumb and pull up on the quick release loop on the MT, and descend using the Lov2 or Vergo.

Note: the fatter the rope the more attention is needed to keep the cam open and teeth out of the way. I use it on 9.4 - 9.9 ropes.

BONUS!

The following mod is only helpful if using the MT as both a primary and secondary (back-up) device. If it is only used as a back-up device, then the basic thumb-loop above is adequate. If it is only used as a primary device, then then just a tow loop is necessary: 

By tying an extra overhand loop off the main thumb loop, the MT can also be used as a primary device held vertically by a necklace/sling. This extra loop provides a connection point that isolates it from the MT's cam and prevents it from opening in the event of a weird fall. The main thumb loop should never be used as a connection point to hold vertically! It might seem simpler to not have a separate tow loop, but in a fall backwards/away from the device, the thumb loop-sling connection can open the cam on the MT. 

The proportion of the thumb loop's legs to each other are critical. 'Y' should always be 2-4 times as long as 'X'. This insures that when it is connected to a sling/harness as the primary device, held vertically, and towed up the rope - the 'Y' portion of the thumb loop will be slack and the weight of the device/rope friction is totally held by the 'X' leg. If 'Y's not slack, there is the possibility that it will open the cam when towed up the rope or during or during a "fall" where the climber falls out way from the device. However the other extreme should be avoided also: 'Y' should not be too long in relation to 'X' as to create a huge loop that could catch on something. The second photo below shows an ideal amount of slack when connected as a primary device. In the video below, the ratio of 'X' to 'Y' is a little too great and creates too big a thumb loop when when connected as a primary device. Hope this all makes sense. If not you can respond below. 

The extra connection loop isolates it from opening the cam. It also makes it easier to connect and disconnect because nothing has to be fed through the MT 'biner hole to connect to the necklace/sling. The MT can be opened and closed without having to remove the connection point (cord) like other setups. It took a bit of experimenting with the size and relative locations of the loops to optimize them for my set-up.

This video clip shows how the double loop can be used either as a connection point to be used as a primary device, or as a quick release for rapping when used as a back-up device. The thumb loop also aids in opening the toothed cam after a fall or weighting the rope by inserting thumb and pulling up. In order to do this, the rope needs to be tensioned below the MT or it needs to be un-weighted. (Also note as stated above that in this example the leg ratio of 'Y' to 'X' is  little too great. The overhand knot tow loop should be re-tied to reduce that ratio. This is also the beauty of this set-up, in that it is easy to re-tie the overhand loop to adjust the relative leg lengths.)

BACK TO THE R’NL

Nowadays, if I’m using it as my backup, I’ve found an easy and comfortable way to grab the device and open the cam while grabbing the rope just ahead of the device. See photo. This allows me to keep the cam open and grab the rope at the same time. I grab the R’nL cam with the lower part of my hand and pivot the cam up using my lower part of my hand and fingers to keep it open and wrapping my hand around the rope and device together. Simple to do and I don’t have to use the finger/thumb loop; and, the cam is still active should my hand come of the rope while rappelling so it would act like an auto-block. Plus, I still have the option to lock the R'nL open if I desire.

Sooo, bottom line: Both do their job well. Both are suited to be either a primary or a secondary/back-up TRS device. Both devices can easily be used in series with each other for a TRS rig: one as primary, the other as secondary. The drawback being that a GG, ATC, or some such rappel device has to be added in order to rap (unless using a Lov Taz2 or a Vergo). Neither are rated as a primary device for LRSing, but both can serve as a cache loop manager and then be used as a primary or back-up for TRSing back to the anchors.

SUMMARY

MT

Positives: Pivots slightly less when locking up; Better/more efficient for hauling or any time there is a significant bend in the rope with weight on it (because of bearings in the pulley); it’s slightly more compact; As a TRS primary device with the double loop mod, it’s easy to connect/disconnect to chest sling/necklace. With thumb loop (and tab removed), it’s always safely locked on rope.

Negatives: If the lock-out tab is not removed, it is finicky and can be a PITA when rapping and dangerous if it locks open un-noticed; slightly more friction with fatter ropes/‘biners when ascending (though not significant); just slightly harder to remove from rope once it’s weighted (thumb loop alleviates that); no easy way to manually hold open while rapping (without thumb-loop) if you’ve ground the tab off. Needs modifying to be optimal IMO (or buy a new Nano that doesn't have the lock-out tab).

R’NL

Positives: Positive hands-free lock-out if needed; easy to manually hold open device while rapping without a thumb/finger loop; slightly less friction when used as a primary device; half the cost of the MT; little to no possibility of it unwontedly locking open

Negatives: Pivots a slightly more when locking up because of length of device; a bit of a hassle (even with finger loop) to lock open the cam because the cam must be rotated significantly. Not the best if you’re going to do a lot of hauling. The external location of the cam outside the housing is a safety concern when using as a primary TRS device above another device.

SO THEN…

Question: which one is better as a back-up?

Answer: It depends - they both have have positives and negatives. If your leaving it on the rope when rapping and want it to be hands-free, then the R’nL is the answer. If you’ve ground the tab off the MT, then using the thumb loop and manually hold it open while rapping is super slick. If you don’t have either device, pick the one that has the most positive features for your intended uses.

Question: Should you switch from one to the other?

Answer: Probably not, unless one of the methods for keeping it open while rapping has a significant advantage for you or unless you plan on doing a lot of hauling also, then, defiitely the MT would be better.

Update: There have been recent claims that the R’nL will not lock up if twists on the rope. I think this would be more of a concern if using the RnL as a primary device. Test and use at your own risk. I’ve mainly used it as a back up and in the lower position the top device should keep it from twisting on the rope. If this is a concern to you, by all means use the MicroTrax.