# How does the thrust rating of a push rod/linear actuator (I've seen it in both kg and N) relate to the amount of weight it can move?

I'm working on a custom RC project, and I'm needing to move a lever with a "weight" of 5 lbs. 5 lbs is required to actuate the lever, and I need to push it 5 mm. Gravity does not affect the system, as the lever is spring-loaded and being moved horizontally. After being moved, it will return to its original position. Small push rods and linear actuators seem to be the best way to achieve this given my available space, but what N or kg thrust rating would be required to move the lever? I've seen push rods with thrust ratings of 128 N and 4 kg, but never a rating for maximum weight capacity. I'd like to know what minimum rating is required to move the lever. Googling the relation/conversion from N to kg or lbs gives me conflicting answers. I've also tried using 7 kg high torque micro servos to pull the lever, but the gear teeth end up breaking after several successful pulls. I know the mounting distance from spline center plays into this.

This is probably simpler than I am thinking it is. Any insight would be appreciated.

Edit:

This may clarify some things: I'm wanting to make a homemade trigger pull for sighting in firearms, and using this as a learning experience with Arduino. As far as I can tell, trigger weight is measured simply in pounds applied before the trigger break. Every source I could find just refers to it with mass units instead of force units. Part of confusion is with how the trigger weight translates to calculating a motor's torque required to move the trigger. This could be a misunderstanding of trigger weight.

• If there are conflicting numbers, perhaps you have an incorrect conversion factor or a rounding issue. What are the contradictory numbers?
– Abel
Apr 3 at 3:39
• There shouldn't be any problem converting lb force to Newtons. 5lb =23N. Look Here: unitconverters.net/force/newtons-to-lbs.htm . I'm wondering if the problem you're having with the micro servos is that the lever comes to a stop after 5mm and this is causing them to break down? Do you think something like this might work? sparkfun.com/products/18591 (with 100:1 ratio) It's rated up to 5kg.
– Rich
Apr 3 at 3:53
• @Rich I've updated the post and added the Edit beneath the original. In summary, its trigger weight, and trigger weight is typically measured only in pounds and ounces. This may just be leaving off the ft/in unit of the measurement, making it sound like a mass unit instead of a force unit. Apr 3 at 16:22
• It's a force measurement: Trigger weight is a description of the force required to pull the trigger back enough to squeeze off a round. For instance, if a trigger has a 2-pound pull weight, it takes 2 pounds of force to pull the trigger far enough to fire a bullet. blog.gunassociation.org/trigger-pull-weight-gun
– Rich
Apr 3 at 18:29