Timed 3 Large Silers Today

[Larry Pletcher]

Today Steve Chapman and I timed three Siler locks.  Each was a modified one with unique features.  We did 20 trials each.  We were aware before we began that  the multiple differences  in these locks would make it difficult to draw conclusions about what made each lock fast.  By the time we were done, it didn't make any difference.  The locks were so close in performance that the differences were not an issue. In fact, it shows that a good lock can be set up different ways by different tuners and still provide great performance.  

An example of the differences is the strength of the frizzen spring.  There is a large difference in spring strengths but the performance was almost identical.  My complements to Sam Everly on his tuning job.  His ball bearing lock (#4) was silky smooth and easy to work with.

My complements to Jim Chambers also.  His rebuild of my test-bed Siler (#2) was slightly faster than the other two.  It's the one with the bronze bushing.   The other lock (#3) was one Jim and I collaborated in 1992.  We tested the lock 6 different ways, and this lock has the best of those 6 tries.  The MB article was with this lock.

Below is a sheet that outlines the modifications and notes the spring strengths.  Note that on locks #2, #3 the pull weight was less going to full cock than going to half cock.  That could be felt during the trials.  When I add this to my web site I'll include a list of all the trials, but for now here is a summary:  




My thanks to Steve for helping out today.  This is more fun with another flint fan to work with.  If I forgot something, I'm sure he'll step in.

Regards,
Pletch

[hanshi]

Interesting about the "compound bow" effect of the tuning.  My stock Chambers Colonial Virginia is a bear to pull to half cock but is a pussy cat after that.

[California Kid]

Pletch, whats Larry Niday doing these days? I remember him from WKU '88.

[Dphariss]

Forsythe describes the "heavy first lifting". It is one indicator of a well designed lock. That the pressure requires lessens as the cock/hammer is drawn back is a function of proper tumbler geometry and a proper spring.
The primary advantage to this is reducing sear notch pressure and the higher pressure on the hammer when at rest holds the hammer on the cap better during the pressure cycle. In flint guns the increasing pressure helps maintain speed as the flint scraps down the frizzen face.

Reduced sear notch pressure makes it easier to get a light trigger pull.

Dan

[Larry Pletcher]

California Kid,
I haven't had any contact with Larry Niday for years.  I hope he is well.  With all the folks assembling lock kits, Larry would be on my short list of fine lock men.

Dan,
Thank you for the comments from Forsythe.  It makes sense that reduced sear pressure would desirable outcome.

The matter of flint speed down the frizzen is valid as well.  Many years ago I timed a lock whose velocity down the frizzen increased.  I could tell this by high speed stills taken at three locations during the flint contact with the frizzen. In equal amounts of time between pics, the flint traveled a larger distance in the lower photo sequence.  Few locks will do this.

-----------just checked---------------

The lock above was the Davis "Twigg" lock.  The September 1992 issue contains the article, "Lock Timing Part 2".  It's also on my web site.

Regards,
Pletch

[Blacksmoke]

Dan is correct!   With his comment on hammer tension.  Going from "resting forward" to "full cock" the hammer tension or poundage should decrease NOT increase !  The lock makers of today seemed to have forgotten this important feature.   We should not have to tune every lock as it comes from the factory.      Actually it is a simple law of physics called MA ( mechanical advantage). The closer to the Axel of the tumbler the tension of the mainspring is applied the lower tension on the hammer and the further from the Axel the tension is applied the greater pressure on the hammer as it flies forward.  In the full cock notch the sear should have minimum tension against the tumbler and there by easier to release.   Just that simple                Hugh Toenjes

[Leatherbelly]

Huey,
 Funny, chatted to Taylor this morning about tension and mechanical advantage.Makes the lock gentler on flints and extends the lock life.