GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Cal on October 21, 2013, 07:01:18 PM
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On another form, a member has presented first data obtained by means of an inductive position sensor that plots the striker position as a function of time.
http://img.photobucket.com/albums/v398/pneuguy/HDDdata_zpsf7ca69a7.gif (http://img.photobucket.com/albums/v398/pneuguy/HDDdata_zpsf7ca69a7.gif)
I have tried to develop conversation there on how the method and data could be useful for advancing the developement of air gun systems, but have met the stone wall.
Anyone here care to comment on the data plotted in the image attached?
cheers
Ca;
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I'm interested but I not sure how much I can be of help. The best person here would be Bob (Rsterne) to shine in. I consider him the top guy here is research and development.
At least now I'm subscribed.
Best of luck
Daniel
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Dan
No expert air gun designer exclusive , can you read graphs?
I have my interpretations, but wait to hear others.
give it a go!
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Isn't that the guy that copied the other guys patient?
http://www.network54.com/Forum/79537/thread/1283613640/The+subject+of+the+John+Bowkett+Hammer+Debounce+Device+came+up+on+the+Chinese+page--- (http://www.network54.com/Forum/79537/thread/1283613640/The+subject+of+the+John+Bowkett+Hammer+Debounce+Device+came+up+on+the+Chinese+page---)
No?
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Well, you can see how it bounce. What would be interesting to see if there was way to measure the air waisted. What would be interesting to see is the different bounce at a set hammer force and different PSIs that way you could compare the air wasted.
My biggest issue with HDDs is that the reduce hammer energy. Due to friction. I think the only way to reduce hammer bounce all together is with a electronic hammer
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without any consideration for any striker multi hit,
I see the total valve displacement and that the valve open time (duration) is plotted.
In this particular plot, the valve opening event characteristics appear to be equal for both conditions. At least the displacement plots over lay.
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soft of...The HDD is a little lower so the valve is opening just a tad less. That little bit of difference can be a lot when you take in to consideration that this is happening in milliseconds and a .01 to .02 of an inch means less air which translates to less power at the mussel. That tiny difference can add up to more. I can guess that the more the hammer energy the less the gap between the two is. I can also assume that most people that are looking at a HDD are looking at lower power out of the gun so that gap will increase.
Another thing, is how constant the hdd is on the hammer. If the pressure that the hhd applies to the hammer varies from shot to shot that would translate to larger SD on a string. When ever I mod my gun I always try to keep my variables to a minimum. This gives me constancy. A HDD ads another variable and the you add the ware and tare for the hdd and the area where the hdd engages the hammer. Which in the long run will happen.
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Approx 0.030" lift over 2.5 milliseconds. Looks like the bounce didn't open the valve.
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I did not noticed that but you are right. Once the PSI goes down then it will start opening.
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I see no reason to believe the valve is opening on the bounce. I also believe this to be the best example he could generate in order to engage the, 'gracious! my hammer is bouncing paranoia'. There is no indication of valve stem motion, just the hammer bouncing. I found this to be able to open my valve when pressure was around 1k2 psi with a 30 gram heavier hammer. Like I have long gotten into trouble over there for saying, air wasting bounce is a tune-able qty with that rifle, and that is with the way heavy 79 gram hammer. Go lighter and quit worrying for one, careful tune will also do it.
Once again we have the worry quotient engaged, and still no guarantee that you'll get more shots...best to keep your money under those conditions.
cheers,
Douglas
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May I suggest that we limit this thread discussion to every aspect of the graph data and tool prospects EXCEPT
anything that has to do with the need for multi strike suppression? Only to speak of the function in objective description of the observed motion data.
That topic seems to reduce everyone's objectivity, and I for one have no interest in the topic.
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All the graph shows is that there is no air loose during the bounce and that there is a small loss of hammer travel with the HDD. That small loss can translate to a good amount of power a .01 or .03 in extra in area can be a significant amount of power.
I think that is all the chart shows.
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Good data. Of cource there is going to be argument about what the data actually means, but isn't that true of all data collection?
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soft of...The HDD is a little lower so the valve is opening just a tad less. That little bit of difference can be a lot when you take in to consideration that this is happening in milliseconds and a .01 to .02 of an inch means less air which translates to less power at the mussel. That tiny difference can add up to more. I can guess that the more the hammer energy the less the gap between the two is. I can also assume that most people that are looking at a HDD are looking at lower power out of the gun so that gap will increase.
good observation, I had not noted the "slightly lower" displacement of the striker with the device fitted.
So true that a little difference could be a lot of difference.
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Good data. Of cource there is going to be argument about what the data actually means, but isn't that true of all data collection?
Well, It's hard to know if the data quality is "good",* but if there is anything to it, the inductive transducer will be a very useful tool!
I accept that each of us will see different meaning in the data. My hope is that you will tell me something that you see, that I may have missed!
*( I am somewhat concerned about the motives of the poster, I trust that the data is not just "graphic art" but accept even that. ;-)
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All the graph shows is that there is no air loose during the bounce and that there is a small loss of hammer travel with the HDD. That small loss can translate to a good amount of power a .01 or .03 in extra in area can be a significant amount of power.
I think that is all the chart shows.
Are not the time and displacement of the valve opening event of significance to you? I recall that some work was done with o-rings on valve stems to determine the same thing. and left the timing to complicated mathematics with several assumptions.
In these plots, the valve opening is clearly all values above the .73 value of the closed valve as shown by the straight line to the right side of the graph for both conditions.
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yes the displacement of the valve is important. But I think it is important across different pressures and not much on one pressure or at different hammer preloads.
Are you referring to the Bstanley mod? If you are this is very different. the oring are there to flatten the string as your go down in pressure in other words it is to remove peak of the bell curve. The oring might dampen any bounce but these are two very different things.
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The graph also shows the time periods between the three impacts of the striker on the valve stem.
From the data, the time period between the first and second strike is significantly greater than the time period between the second strike and the third.
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By itself, don't think this one graph can tell you much. Need to send the measurement device to Bob, where he would use it for data collection as he runs it through a range of scenarios/tests.
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May I suggest that we limit this thread discussion to every aspect of the graph data and tool prospects EXCEPT
anything that has to do with the need for multi strike suppression? Only to speak of the function in objective description of the observed motion data.
That topic seems to reduce everyone's objectivity, and I for one have no interest in the topic.
considering the source of the data, that is not possible. the conditions under which he operates require consideration. he's in business to sell a device to stop air wasting bounce; that the hammer bounces is a given. That it can re-open the valve is the issue at hand. That data put up does nto show it opening, so why would you care if the hammer bounces? for his purposes, showing the air opening bounce would be useful, and yet the best data he has does NOT show it. Nor is there any guarantee of getting more shots with his device( since under most conditions, there is no air-wasting opening ). The Marauder could be tuned to benefit, but the overall peak in the performance would be higher with a tune that does not require such a device.
Really, recognize this for what it is, paranoia-inducing salesmanship. I have no intrest in it, save for pointing it out for what it is.
cheers,
Douglas
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May I suggest that we limit this thread discussion to every aspect of the graph data and tool prospects EXCEPT
anything that has to do with the need for multi strike suppression? Only to speak of the function in objective description of the observed motion data.
That topic seems to reduce everyone's objectivity, and I for one have no interest in the topic.
considering the source of the data, that is not possible. the conditions under which he operates require consideration. he's in business to sell a device to stop air wasting bounce; that the hammer bounces is a given. That it can re-open the valve is the issue at hand. That data put up does nto show it opening, so why would you care if the hammer bounces? for his purposes, showing the air opening bounce would be useful, and yet the best data he has does NOT show it. Nor is there any guarantee of getting more shots with his device( since under most conditions, there is no air-wasting opening ). The Marauder could be tuned to benefit, but the overall peak in the performance would be higher with a tune that does not require such a device.
Really, recognize this for what it is, paranoia-inducing salesmanship. I have no intrest in it, save for pointing it out for what it is.
cheers,
Douglas
Completely agree. The graph that would be helpful would be a graph that show the bounce at different pressures as I mentioned before. We all know that it bounces. And even more help full would be a graph of the valve movement and not the hammer.
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To me it makes sense that anyone with interest in the thread "Modeling PCP Valve Lift and Dwell" only two lines below would be very curious about the details of this instrumentation.
http://www.gatewaytoairguns.org/GTA/index.php?topic=48892.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=48892.0)
But I admit, it is at times difficult to get over personal bias
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But I admit, it is at times difficult to get over personal bias
Oh yes, personal bias about such things is clearly bad( darn it, I broke my sarcasm meter again ).
As to the modeling idea, this is a useful tool indeed.
As Tom pointed out, a full battery of experiments would show that it not required to spend any money on that device to improve the rifle. I make a living designing and testing stuff. I have to be able to look for missing parts in order to have them be no longer missing. I am pretty good at it. That data does not show what is claimed, and there is a whole host of other stuff going on that is, thank goodness, not sanctioned or protected here.
cheers,
Douglas
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Douglas
What do you think of the changing time period between strikes?
Not exactly to the T= 2pi X root of mass/spring constant.
Is there an explanation due to friction or the imperfection of the valve restoring force? It would seem that such real world defects would also show as disruptions from the smooth curves joining the peaks.
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Douglas
What do you think of the changing time period between strikes?
Not exactly to the T= 2pi X root of mass/spring constant.
Is there an explanation due to friction or the imperfection of the valve restoring force? It would seem that such real world defects would also show as disruptions from the smooth curves joining the peaks.
I suspect there is a reason one could justify with numbers. However, from another POV, if we take two cocked distances, and release the sear, the longer distance will take longer to reach the end of its travel. I recall being tortured by decreasing period and amplitude equations. I made quite an effort to never pick them up again...lol I will assume that no valve opening is happening during the shown hammer bounce. This leaves the valve stem as a spring, and the valve head against its seat( compressed delrin ) to kick the hammer back.
Do you see something else?
cheers,
Douglas
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You bring up a point,
There is no discontinuity in the motion maps that suggests the changing conditions associated with lifting the valve off it's sealing seat.
Perhaps lost in resolution and line width.
Regarding the spring travel time, As a spring is compressed, it's force (potential energy) increases. more force per unit weight, and the acceleration is increased as well,
Longer distance at a faster rate = same time. RxT=D
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I view that graph as near proof that the valve is NOT reopening, certainly not on the third strike.... and IF it is opening on the second strike, by VERY little....
The hammer position, at rest, in the non-HDD case (red line) is at ~0.72" of hammer stroke from cocked (the straight line on the right).... Draw that line all the way across the graph.... Is the peak at point #2 above that line?.... maybe, but not by much.... Compare this with peak #1 which is at about 0.77" (a lift of ~ 0.050").... The amount of air released by the valve is the area under the curve above the straight line where the hammer rests against the valve stem....
I see it as proof positive that hammers bounce (without an HDD or limiter).... and nothing else.... other than that they MAY not waste much (if any) air by doing so.... IMO....
On the other hand, the technology to do the measurement is amazing, and very useful....
Bob
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I thought you would be all excited over a tool that would so readily plot the time and duration of the valve opening event. The direct result of your extensive spring and hammer optimization work. After all, It is the valve event that is the important aspect. The striker is only a means to that end ;-)
But
I thought wrong....
Oh well ;-)
But it does cause puzzlement that this "real data" would be so much less interesting than plots of points based on computer calculated variables.
Even not knowing the details, I observe that the data generated displays strengths and weaknesses that would need to be understood if the analysis tool were to be applied in constructive ways.
Please if you will, what is your take on the changing time period between strikes?
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Regarding the spring travel time, As a spring is compressed, it's force (potential energy) increases. more force per unit weight, and the acceleration is increased as well,
Longer distance at a faster rate = same time. RxT=D
clearly, so something else is going on...:)
Also, taking Bob's .050" lift estimate, and the assumption that this was done at low pressure to exacerbate bounce behaviour, I'll bet that this done at a specialized tune just to show the worst possible behaviour. Given the likely lift of average power and low pressure being in the neighborhood of 2x this particular example, I see more proof of scare tactics in play.
It is interesting, I'd like to do something analogous with a high speed x-ray camera...LOL
cheers,
Douglas
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I must admit that I have questioned the motive as I've studied the data.
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I must admit that I have questioned the motive as I've studied the data.
The valve is opening. Steve said so. It is clearly drawn that way with arrows and everything. What else is there to this discussion?
cheers,
Douglas
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I must admit that I have questioned the motive as I've studied the data.
The valve is opening. Steve said so. It is clearly drawn that way with arrows and everything. What else is there to this discussion?
cheers,
Douglas
Lol Doug
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But
I thought wrong....
Oh well ;-)
I thought I commented that the process looked great!....
the technology to do the measurement is amazing, and very useful....
Guess you missed that....
I have no idea why the first rebound period is longer than the second.... As I understand the theory of a simple spring oscillator, the period is independant of the amplitude, even though that is counter-intuitive (the hammer is travelling further on the first bounce, albeit faster).... Perhaps friction is the culprit?....
Steve "says" that the valve is releasing air on impact 2 and 3.... However, the amount of air passing through the valve (assuming constant pressure) is proportional to the area under the lift curve.... Extend a line across the graph at the height of the red line after the hammer comes to rest (~0.72"), and tell me how much area there is on impact #2 compared to the initial impact.... 2-5 % maybe, certainly not 10%.... On the third impact?.... I'm not even sure the valve is moving further than the spring in the Delrin poppet material (which I measured on a Disco at 0.009" at 2000 psi).... ie the valve STEM is moving, but without cracking the seal.... I think the flexing of the poppet face is damping the third impact, preventing another bounce of the hammer....
Bob
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This decreasing period reminds me of the old SuperBall's or so they were called. Drop it and as it slowly bled energy the frequency increased. This is mass damper stuff only holds when they are attached...get a point where there is no force applied, and that period thing starts going to pot as distance changes...or so I think, pre-caffiene, while my tea is brewing.
cheers,
Douglas
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I understand that the spring preload has an effect on the period.... In addition, we are only seeing half the "normal" action of a simple spring pendulum, as it is impacting the valve stem at the center point (highest velocity) of it's travel.... That impact obviously has a damping effect as the amplitude is decaying very quickly, particularly in the case of the 3rd impact (where I believe there is evidence that only the Delrin poppet material is flexing)....
Bob
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'Not sure if any had followed the thread on the yellow, but the return reply to my "counting blocks to determine area under the curve" was on the order of
"because there is no pell in the bore, and hence no resistance to filling, the gas moving past the small opening on secondary strikes will be substantially more than is evident by graphical area alone. And so, area under the curve determinations are not valid."
My consideration of same is that in the brief time of opening, the difference between open and closed bore conditions will be insignificant. The volume between valve and pell location being sufficient to accommodate "most" of the "waste".
On another aspect,
Looking carefully at the slope of the line of striker position/ time, It is evident that little or no acceleration of the striker occurs after a travel distance of about .4. At least that is what I see by placing a straight edge on the monitor ;-)
This could be significant in optimizing over all striker geometry with a mind to compactness. Such optimization of piston stroke may result in an increased tendency to support "bouncing" however ;-)
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I don't visit the Yellow, I think I would last over there for a very short time before getting the boot.... Steve probably does have a valid point about more air escaping from the valve for a given lift and dwell (area under the curve) once the pellet has left the bore (ie on the 2nd impact), however.... Quantifying that gives quite a bit of "wiggle room" for the argument for HDDs.... The ultimate proof is how much air they save when tuned to the same FPE level.... I would suggest that the answer on a properly tune, regulated gun, is very little.... while on the low pressure end of an improperly tuned, unregulated gun, is quite a bit....
little or no acceleration of the striker occurs after a travel distance of about .4
Just as with a pellet in a barrel, the highest rate of acceleration takes place initially.... Likewise, however, just as a longer barrel results in a higher velocity, the same happens with the striker.... You can prove that experimentally in any adjustable hammer that does not change the preload as you change the hammer travel (an MRod does both simultaneously).... Useful hammer energy and momentum can be gained through increased travel provided the spring preload has not dropped to zero, after that, you start losing again....
Bob
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On another form, a member has presented first data obtained by means of an inductive position sensor that plots the striker position as a function of time.
http://img.photobucket.com/albums/v398/pneuguy/HDDdata_zpsf7ca69a7.gif (http://img.photobucket.com/albums/v398/pneuguy/HDDdata_zpsf7ca69a7.gif)
I have tried to develop conversation there on how the method and data could be useful for advancing the developement of air gun systems, but have met the stone wall.
Anyone here care to comment on the data plotted in the image attached?
cheers
Ca;
Talk to Michaelthomas he seems to be very tec savy and is manufacturing his own PCP rifle with electronic valve and trigger
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Soft tail
This thread is not particularly about valves, electronic or conventional. Rather a sample of data obtained by tracking the motion of a common spring loaded striker as a function of time and distance being explored. The novel aspect is the introduction of the inductive sensor to obtain the data.
To my awareness, this is the first presentation of such real time data.
It is my hope that different people with differing views and objectivity would see different bits of information in this non theoretical example. And then share those observations with others interested in such things.
I am sure M. Thomas would see things in the plots that you or I may not.
What do you see?
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Soft tail
This thread is not particularly about valves, electronic or conventional. Rather a sample of data obtained by tracking the motion of a common spring loaded striker as a function of time and distance being explored. The novel aspect is the introduction of the inductive sensor to obtain the data.
To my awareness, this is the first presentation of such real time data.
It is my hope that different people with differing views and objectivity would see different bits of information in this non theoretical example. And then share those observations with others interested in such things.
I am sure M. Thomas would see things in the plots that you or I may not.
What do you see?
I'm just starting the exploration of this side of AG's and will look at the data later today and see what I can figure out
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little or no acceleration of the striker occurs after a travel distance of about .4
Just as with a pellet in a barrel, the highest rate of acceleration takes place initially.... Likewise, however, just as a longer barrel results in a higher velocity, the same happens with the striker.... You can prove that experimentally in any adjustable hammer that does not change the preload as you change the hammer travel (an MRod does both simultaneously).... Useful hammer energy and momentum can be gained through increased travel provided the spring preload has not dropped to zero, after that, you start losing again....
Bob
[/quote]
Yes, perhaps the continued acceleration of the striker is lost in the noise. Small gains near the maximum result in large changes of availble energy (MV^2)
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I had another look at the graph, and my "eye" tells me the line is curved right to the end.... My straight edge shows that curve from 0.4" to the end, although slight....
Bob
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I had another look at the graph, and my "eye" tells me the line is curved right to the end.... My straight edge shows that curve from 0.4" to the end, although slight....
Bob
You may be right, I only placed a pencil on the screen as reference for my previous comment.
But just now,.... Using the Libre Draw application to display the graphic, at 310% expansion, any "Curvature" between .4 and .72 is a pixel or less.Having used the line function to draw a tangent line, Which "appears" to be a parallel line. Certainly the graphed line is not convex!
Where are the first derivatives when you need them?
But, I have no expectations of exactness in this first demonstration, it is only a comment about what information the plot may contain.