Edelrid presents with the OHM a possible solution for the climbing of rope teams, with a high weight difference.
If two people with different weights climb, the lighter, belaying person will be jerked off the ground in the event of a fall and will be pulled hard against the wall. In addition, the belayer is pulled far upwards, which significantly increases the climber's fall distance. If the climber is still close to the ground, the two collide roughly. In the worst case, the climber falls to the ground.
The use of a weight sack to reduce the difference in weight is a solution that is only of limited use - who carries a sand sack with them on the rocks? It also severely restricts the belayer's freedom of movement. Even in this constellation, the entire braking force must be applied by the belayer.
The Edelrid OHM with ballast resistor
The development of the ohm was supported by scientific investigations at the IFT Stuttgart. It is an upstream resistor installed in the first hook of the safety chain. In the event of a fall, the rope is pulled into the braking unit of the device and the lintel is progressively braked. That is, the device does not stop the rope abruptly, but slows down its passage speed, so that the fall can be intercepted dynamically by the belayer. The ohm thus increases the friction in the safety chain, regardless of the belay device used. As a result, the safer must apply significantly less hand force on the brake cable and is not pulled uncontrolled up or against the wall.
Due to its construction, the ohm does not restrict the handling of the rope in advance. It neither increases the friction in the lead, nor is the rope output negatively affected. Only with a fall, the braking effect of the device is activated. Even the release of a heavy climber is much easier to control due to the increased friction. Accidents during deflation can be avoided.
In this way, the ohm helps both the belayer and the climber: The safer is no longer pulled uncontrollably against the wall. The climber can go liberated to the cusp, without fear that his safer may not be able to hold him, or that the landing will be very hard.
The German Alpine Club and the Swiss Alpine Club (DAV¹, SAC²) recommend that the climber should weigh no more than the 1,33 fold of the belayer, ie a maximum of 1 / 3 (eg 60 safe, maximum climber 80 kg). In case of large falls, especially in the climbing gym, the highest degree of caution and attention of the belayer is required even with this weight difference.
Ohms in the safety chain significantly increase this factor. In this case, the ohms benefit particularly secure persons from a body weight of 40 kg. Especially in the lower weight ranges can be secured with the help of the ohms precursor, which are up to 100% heavier than the belayer.
Is the OHM really a solution?
At first we were a bit skeptical about LACRUX, but the video is quite convincing. The only open question is whether the OHM can really secure dynamic. In our opinion, that is of central importance. Logically, not on higher the first hook, but if the climber is already higher up. It is also unclear whether the OHM really causes any friction during climbing. This could only be judged conclusively by a test of the product. We hope soon to have the opportunity to test the OHM in practice and will then report on it at this point. Here is the promotional video by Edelrid.
Promotional video from Edelrid to the OHM
Credits: Image and information, Edelrid