hangup (LP10)

scerir · Post by **scerir** » Tue Mar 25, 2014 12:30 pm

About LP10 (or LP1).
Let us imagine our first stage is 350 grams and our second stage is 150 grams. Total weight is 500 grams, exactly.
Now we turn unticlokwise the “first stage travel adjustment screw”, and we have a longer first stage travel. Our first stage is now (say) 400 grams, because its travel is longer. Ok?
Now, by means of “first stage pressure adjustment screw” we reduce the weight of the first stage to 350 grams. Ok? Total weight should be 500 grams again, because we did not touch the "second stage pressure adjustment screw".
What if we find that the real, actual total weight is not 500 grams? What does that mean?

renzo · Post by **renzo** » Tue Mar 25, 2014 1:55 pm

Any, ANY time you fiddle with the trigger adjustments, you have to check your trigger weight to be over 500 grams, ALWAYS. That's why most of us have a homemade trigger weight at home or at the range.

That way you are not liable to uncomfortable moments at Equipment Control in the moments previous to a match, when yourmind must be set exclusively on the upcoming shoot.

By the way, I NEVER adjust my AP trigger to less than 530, preferable 540 grams, just in case the EC judge is somewhat brusque when lifting the pistol, or the weather gremlins decided to play a game with my gun.

I'm still to find the shooter who can tell 500 from 540 grams IN HIS OWN TRIGGER!!

scerir · Post by **scerir** » Tue Mar 25, 2014 2:13 pm

Renzo, you are right, but that was *not* the point here. Here it does not matter whether the total weight is 450 grams or 500 grams or 550 grams.

I was trying to point out that if you turn the "first stage travel adjustment screw" (anticlockwise or clockwise) you are also changing the weight of the first stage (which is obvious) ... but you are also changing the weight of the second stage (which is not obvious at all).

scerir · Post by **scerir** » Tue Mar 25, 2014 2:22 pm

see attachment for "first stage travel adjustment screw"

renzo · Post by **renzo** » Tue Mar 25, 2014 4:05 pm

Scerir, please excuse me for dissenting, but I think it is just the point.

You're telling me that you will change a setting in your trigger (albeit a partial one) without checking the final result in weight??

Aniway, in my experience (shot some years a LP-1C and since 2010 a LP-10, among a host of different FWB's) every time I modified the first stage weight and/or travel, the final setting of the trigger needed adjusting from its previous state.

Silvershooter · Post by **Silvershooter** » Tue Mar 25, 2014 4:22 pm

First stage travel adjustment screw does not affect weight (as I understand it)

From the manual.
WARNING: Mind total trigger pressure! It is the sum of first stage
pressure plus second stage pressure (also see chapter
6.3)

My LP10 failed EQ at a comp 2 weeks ago and no matter how much I turned the First Stage Pressure adjustment screw it would not pass. First stage was set at just under 400 gm. I had to increase second stage pressure adjustment to get it to pass.

rmca · Post by **rmca** » Tue Mar 25, 2014 9:27 pm

scerir wrote:Our first stage is now (say) 400 grams, because its travel is longer. Ok??

No. This is where you made the wrong assumption.

The first stage is heavier because you are compressing it's spring more before you contact the second stage lever.
Have a look at the drawing.

Springs don't behave in the same way all through their compression. It takes less force at the beginning and a lot more at the end. I'm sure someone out there with an engineering background can explain better.

So if you adjust the first stage weight back from 400 to 350, because of the longer first stage, you'll still have a more compressed spring than you had to before.

That difference, the first stage spring more compressed, implies more force to keep it moving. Add that to the second stage spring and you have more than the original 500g.

Also, because both of the first stage's weight and travel screws are at different distances from the pivot point of the trigger, it means that equal adjustments in both (for example half a turn anticlockwise) will result in a different total weight.

Hope this helps and makes sense...

j-team · Post by **j-team** » Tue Mar 25, 2014 10:21 pm

Silvershooter wrote:First stage travel adjustment screw does not affect weight (as I understand it)

Yes it does. If you lengthen the 1st stage the spring must be compressed more before the second stage comes in and vice versa.

So, if you lengthen the 1st stage the overall trigger weight increases, and, if you reduce 1st stage overall weight reduces.

In either case an adjustment on the second stage is required to get back to original overall weight.

conradin · Post by **conradin** » Wed Mar 26, 2014 12:43 am

Silvershooter wrote:First stage travel adjustment screw does not affect weight (as I understand it)

From the manual.
WARNING: Mind total trigger pressure! It is the sum of first stage
pressure plus second stage pressure (also see chapter
6.3)

My LP10 failed EQ at a comp 2 weeks ago and no matter how much I turned the First Stage Pressure adjustment screw it would not pass. First stage was set at just under 400 gm. I had to increase second stage pressure adjustment to get it to pass.

I set mine at 425/75. I have a weight by Gehmann. It is interesting to know that when I am this close to 500, I would weigh it and passed, then weigh it again and it failed, etc.

scerir · Post by **scerir** » Wed Mar 26, 2014 1:14 am

rmca wrote:
scerir wrote:Our first stage is now (say) 400 grams, because its travel is longer. Ok??
No. This is where you made the wrong assumption.

The first stage is heavier because you are compressing it's spring more before you contact the second stage lever.
Have a look at the drawing.

Springs don't behave in the same way all through their compression. It takes less force at the beginning and a lot more at the end. I'm sure someone out there with an engineering background can explain better.

So if you adjust the first stage weight back from 400 to 350, because of the longer first stage, you'll still have a more compressed spring than you had to before.
That difference, the first stage spring more compressed, implies more force to keep it moving. Add that to the second stage spring and you have more than the original 500g.
Also, because both of the first stage's weight and travel screws are at different distances from the pivot point of the trigger, it means that equal adjustments in both (for example half a turn anticlockwise) will result in a different total weight.
Hope this helps and makes sense...

Yes, I think we are saying the same thing. First stage spring more compressed means more weight on the first stage. (But - keeping the travel of the first stage - I can reduce the weight of the first stage if I unscrew the first stage pressure adjustment screw).

The point I'm trying to make is *not* that the first stage travel adjustment screw has an effect on the weight of the first stage (and on the total weight, first stage + second stage).

The point I'm trying to make is that the first stage travel adjustment screw has an effect on the second stage (its weight, its amplitude, its feeling).

rmca · Post by **rmca** » Wed Mar 26, 2014 8:42 am

scerir wrote:The point I'm trying to make is that the first stage travel adjustment screw has an effect on the second stage (its weight, its amplitude, its feeling).

It can't.

The second stage lever stays in the exact same place no matter what you do to the first stage. The only thing that changes is the compression of the spring in the first stage and the angle it's lever has when it makes contact with the second stage lever.

The second stage lever has it's own adjustments, in weight and travel (sear engagement). If you adjust the sear engagement then it will change your first stage as well, because it determines the position of the second stage lever which in turn will determine the rest position of the first stage lever.

Have a good look at the image with my 6 year old type drawing (kind of hard drawing with the mouse...), it will make this much clearer.

Hope this helps

scerir · Post by **scerir** » Wed Mar 26, 2014 9:27 am

rmca wrote:
scerir wrote:The point I'm trying to make is that the first stage travel adjustment screw has an effect on the second stage (its weight, its amplitude, its feeling).
It can't.
The second stage lever stays in the exact same place no matter what you do to the first stage. The only thing that changes is the compression of the spring in the first stage and the angle it's lever has when it makes contact with the second stage lever.

You wrote the good one. "The only thing that changes is [....] the angle it's lever has when it makes contact with the second stage lever." Exactly that.

I've got the idea that the "angle of contact" and possibly the very "point of contact" between the trigger lever and the second stage lever changes if you turn (clockwise or anticlockwise) the first stage travel adjustment screw. Changes a bit, but it changes.

And this fact changes the weight of the second stage, its feeling, its amplitude. It is not just a personal impression. It is a measurable thing. If you turn the first stage travel adjustment screw anticlockwise, the second stage becomes longer and not so dry. The more you turn that screw clockwise, the more the second stage becomes dry and short. (Of course the trigger-stop does not enter in this cinematics, and the sear engagemant is kept untouched.)

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