Stem travel distance

[mr007s]

There is a discussion regarding reduced volume valve work for the 1377 on a previous thread. This has me wondering how far the stem travels when the hammer strikes  it.

Given that the spring combinations have an effect on the question, lets say you are using a heavy hammer spring and a light valve spring.

Anyone here recorded this during various testing?

[quickster47 †]

Not yet but would sure be an interesting series of tests.

Carl

[bdb12586]

Like you said Due to spring combination I would assume you could travel until it bottoms out the question is what variables dictate this. Carl posted hot rodding a 13xx in that article the check valves were different lengths. His findings if I remember right were the shorter check valve produced higher fps. Did this allow the valve to travel farther? Also consider lighter spring= longer spring I would think that spring bind could also limit travel. I’m just guessing but that’s what I came up with. so I guess the first thing would be to check travel on the valve out of the gun with the spring you would intend to use

[mr007s]

I have a stock 1377 valve for reference. The stem extends from the body around 1/2" It will compress the full length by hand. I don't think the hammer will actually cause it to travel to it's full stroke. If one wanted to reduce the volume of the internals, one possibility would be  place a spacer inside the spring. The problem is how much spacer length would restrict the hammer operation and cause negative results.
I have not found a way to measure the movement while the gun is assembled short of a cut away view and some high speed video.

[bdb12586]

how about a greese pen on the valve stem( the back by the hammer) take a shot and see how much was removed?

[NorthStaR]

Mockup a Clear acrylic body tube? Dunno about pressure but you could see inside. The one time a clear gun would be good!
Instead of reducing the internal volume, would shortening the stem work? It wouldn't open for as long.

[Daysailer]

Good subject.

Thinking from the intent of the reduced volume idea of the refered to post,
IE. Same amount of air in smaller space should create higher PSI to improve
velocity with fewer pumps. Like the very small valve that the Daisy 717 and 747
pistols use to get 360ish fps with one stroke.

I have a spare 1377 valve the may not have a stock check valve in it, but
trialed a .22lr shell inside the valve spring to see if a spacer was a vialble way
to take up some space in the valve.  With the empty shell in the spring, I could not
get any release valve stem movment.  So at least I know that the shell length
is too long, for the valve I was using.

One kinda long tedious method to try and determine stem travel distance...

Get some kind of 1/4-5/16" nylon rod or other material to make inside spring
spacers.  Then trail different lengths to see what restricted length prevents full
dumping of the air charge.  The difference between full restircted movment and
full air dumping, would indicate the travel distance.   

Lots of trial and error, but it might work.

The number of pumps would have to be part of the constants for this, as
fewer pumps would need less stem travel/open valve dwell time to get all the air out.
More pumps would need more stem travel to completly dump.  (i think this is'
why heavier springs are used by those body builders who like to 'pump it up' 

I am totally guessing... but would be surprised it the stem travel distance exceeds 1/8"

Please lets us know what you find..
I am just starting my 'one mod at a time' testing with a brand new 1377 for my
PPP project.   

[mr007s]

Thanks daysailer, I have done that. With a delrin spacer length of .437" the valve stem will move .125". My concern is if the hammer will bend or deform the stem if the travel is stopped too short.

And, it is a good bit of work to remove and replace the valve for testing different setups. I would really like to get it right the first try. Probably won't happen but I man can dream!

[Daysailer]

Good luck on your journey, and Thanks for the info and data.  

It will surely save me some time as I travel down my 'road less traveled' 1377 mods.
Most ducks are now in line...
Got my Chrony back.
Got a new unmoded 1377.
Got new glasses (eye strain from forum studies  )
Not many more procrastination excuses.   
Waiting on oring pump pins to make 'reentry' and remod easier.

[NorthStaR]

I know it isn't a 1377 but this idea would be similar to a degree. 

I was thinking, un-oh! But I was looking at a 2250b valve. The piercing pin point is near flush with the cart seal.
Is it fair to say the stem moves to a maximum distance of that of the pin puncturing the cart on cocking. So if the
piercing pin is only able to slide into an old cart one say 3mm and the o-ring is 1mm thick, the distance travelled would be 4mm. 

Those figures are examples, I haven't measured. Its just a theory! 

A hollow piercing like the way a hollow probe is drilled would be interesting. But fiddly to make?
Here's another theory! The gas cart with a standard piercing pin would be momentarily blocked when firing as the pin would reseal the cart
each time it slides on being hit by the hammer. If a hollow pin with the side venting hole slid in it would allow more gas
to enter the valve chamber on striking as well as in its rsting pos. Does that make any sense? 

[1377x]

i have been thinking about this for awhile now
back when i first started reducing the volume in my valve, a spacer that came in the old 1377 valves was used
the first thing i noticed was the stem didn't go all the way in like on a stock valve

[mr007s]

i have been thinking about this for awhile now
back when i first started reducing the volume in my valve, a spacer that came in the old 1377 valves was used
the first thing i noticed was the stem didn't go all the way in like on a stock valve

Sure would like to have a number to go with that info

[Daysailer]

Have been playing around with my spare valve today.

See pics below for clarity

The check valve is .380" long, 3/8"...this must be the shorter 1400a029 valve.
The exhaust valve body is .440" long , 7/16"
The spring is 1.119 long, 1 1/8" ( fractions are closest less accurate ruler readings)

With the spring removed the check valve and exhaust installed in the cone section
leaves about 3/16" of unfilled space the cone section of the valve.  

With the spring added in it proper position, the spring bottoms out, (coil binds(?)) with
about 1/32" of the exhaust valve still outside the cone section.  

This suggests that I could add a 3/16" spacer inside the spring and not create a shorter
valve stem movement than is already limited by the normal parts in the valve.

If the newer long valve is close to 9/16" long, that is probably all you can get and not
risk shortening the potential stem travel, unless you have a spring the doesnt need as
much room to fully compress.    

Pics continued in additional post.

[Daysailer]

Two more pics...

First one with no spring inside.

Second one demonstrating how deep valve is when spring bottoms out.