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 Post subject: Slingshot hammer test
PostPosted: Mon Jan 13, 2014 3:32 pm 
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Today I tested the 2240 using my version of a slingshot hammer. This time using .22 cal with a 14 inch barrel. The avg speed of the pellets were from 470 fps to 550 fps for an actual avg of 503 fps.This avg was achieved by adding all the shot speed,s then dividing by 60. 60 shots. Equals 8.9 foot lbs energy avg. 55 cc air reservoir. I understand that although most of the shot,s were above legal limits, it shows the potential gain using the slingshot hammer. In order to adjust the spring tension to regulate the pellet speed I used a 1/2 inch long allen screw with a 1/4 inch long head, and ground it down in increments until the first shots were under 500 fps. As the pressure dropped, the speed of the pellets rose steadily to plateau at 550 fps. A surprisingly small amount needs to be taken off to reduce the speed by 30 fps, about 1/100 of an inch. I will further reduce it so that all shots are within the legal limit, and test again. Really looking forward to getting an RVA.

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PostPosted: Tue Jan 14, 2014 3:03 am 
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joe hickey wrote:
Today I tested the 2240 using my version of a slingshot hammer. This time using .22 cal with a 14 inch barrel. The avg speed of the pellets were from 470 fps to 550 fps for an actual avg of 503 fps.This avg was achieved by adding all the shot speed,s then dividing by 60. 60 shots. Equals 8.9 foot lbs energy avg. 55 cc air reservoir. I understand that although most of the shot,s were above legal limits, it shows the potential gain using the slingshot hammer. In order to adjust the spring tension to regulate the pellet speed I used a 1/2 inch long allen screw with a 1/4 inch long head, and ground it down in increments until the first shots were under 500 fps. As the pressure dropped, the speed of the pellets rose steadily to plateau at 550 fps. A surprisingly small amount needs to be taken off to reduce the speed by 30 fps, about 1/100 of an inch. I will further reduce it so that all shots are within the legal limit, and test again. Really looking forward to getting an RVA.


Got pictures, Joe?
RVA's are on there way! :D

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-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


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PostPosted: Tue Jan 14, 2014 8:33 am 
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Here are a couple of photos of what I've done. There are a few factors to consider here. First the spring has to be left long enough so it doesn't come out of the end cap or the hammer when the hammer strikes the valve pin. It has to be strong enough to open the valve at the pressure you're using.C02 will need a less strong spring than the HiPac at 1500 psi. The spring shouldn't be too strong, or you will bend or break the cocking handle. The only reason I used the allen screw to adjust the spring tension was because I already had the spring clipped too short for this particular 22 cal setup, and I don't have another spring that,s suitable. The spring at the top is a stock 2240 spring. The hammer is about 3/8" shy of resting on the valve pin.
ImageImage
Here,s a couple of strings done with the above test The group on the right was the first 20 shots. under 500 fps and while making minute adjustment,s to the spring. The group top right were the next 40 shots. 15 kmh wind. 16 yard,s.
ImageImage

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PostPosted: Tue Jan 14, 2014 5:45 pm 
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If I understand you correctly, you haven't made a two part hammer where one part stops and the other keeps going to strike the valve stem, have you?.... Aren't you just using a short, stiff spring and letting the hammer carry on and coast into the valve stem?.... If that is the case, it isn't a true "slingshot hammer", but it is an excellent way to help prevent air-wasting hammer bounce.... It doesn't always work, but it usually helps prevent the hammer from reopening the valve, or at least reduce that effect....

Bob

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Proud Member of the 2000+fps Club!


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PostPosted: Tue Jan 14, 2014 6:06 pm 
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Yes Bob you are right. I have not seen a real slingshot hammer, so knowing that a slingshot "throw,s" the projectile at the target I assumed the slingshot hammer was based on the same principal. Whatever you want to call it, it work, s. The shot string, s I submitted in subsequent post, s indicate that it is more effective at increasing shot count and flatter shot string, s. I believe it is worth looking into, and tested with all variation, s of hammer fired gun, s. After all, the actual slingshot hammer had to start somewhere. This could be something new. The only expence to anyone wanting to try it is the spring and a few minutes of time.

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PostPosted: Wed Jan 15, 2014 1:10 am 
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Joe? Does the bolt face the hammer?
where did you get the aftermarket spring?

I try to stop in at any little hardware store to look at a variety of springs! Always have the hammer, sear and valve spring in a baggy, ready to compare!

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-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


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PostPosted: Wed Jan 15, 2014 6:25 am 
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rrdstarr wrote:
Joe? Does the bolt face the hammer?
where did you get the aftermarket spring?

I try to stop in at any little hardware store to look at a variety of springs! Always have the hammer, sear and valve spring in a baggy, ready to compare!


I don't quite understand the bolt question. The bolt in a 2240 cant be any other way than it is. As for the spring, I think it was in a bag of spring,s I bought from Princess auto.

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PostPosted: Wed Jan 15, 2014 6:31 am 
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this test is worth a look as it compares my hammer set up to the stock set up.topic59848.html

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PostPosted: Wed Jan 15, 2014 6:45 am 
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joe hickey wrote:
rrdstarr wrote:
Joe? Does the bolt face the hammer?
where did you get the aftermarket spring?

I try to stop in at any little hardware store to look at a variety of springs! Always have the hammer, sear and valve spring in a baggy, ready to compare!


I don't quite understand the bolt question. The bolt in a 2240 cant be any other way than it is. As for the spring, I think it was in a bag of spring,s I bought from Princess auto.


Maybe I should call it a screw. The little 10X32 that is inside the hammer spring.

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-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


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PostPosted: Wed Jan 15, 2014 7:43 am 
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rrdstarr wrote:
joe hickey wrote:
rrdstarr wrote:
Joe? Does the bolt face the hammer?
where did you get the aftermarket spring?

I try to stop in at any little hardware store to look at a variety of springs! Always have the hammer, sear and valve spring in a baggy, ready to compare!


I don't quite understand the bolt question. The bolt in a 2240 cant be any other way than it is. As for the spring, I think it was in a bag of spring,s I bought from Princess auto.


Maybe I should call it a screw. The little 10X32 that is inside the hammer spring.


Oh OK. doesn't matter. As I said. I only used that screw because my spring was too short. You could just cut or grind down your spring a little at a time till you get the speed you want. Any heavier spring that will fit into your cap and hammer will work, as long as it is heavy enough and long enough so as not to fall out of either hole, and still open your valve to give you the speed you want. The whole idea is to not have your hammer pushing on the valve. You can feel and see how much clearance you have when you pull back the cocking bolt. I have no set measurement,s for how far from the valve you need to be. I suspect any amount would work.

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PostPosted: Wed Jan 15, 2014 8:50 am 
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rrdstarr wrote:
Joe? Does the bolt face the hammer?
where did you get the aftermarket spring?

I try to stop in at any little hardware store to look at a variety of springs! Always have the hammer, sear and valve spring in a baggy, ready to compare!


Me too! I'm forever picking up springs in the hope that they will be useful. It seems much harder to source an equivalent hammer spring than I would have expected. I currently have some (or maybe just one, the listing was ambiguous) Century C-680 on order. I'm hoping that will be a good fit and stiffer than stock so that I can try this flying hammer trick. Previously I've been using the 2" springs from home depot, but they are just a bit on the weak side even for 177. For my 1377 I finally gave in and clipped the factory spring (I've been trying to keep the factory springs untouched in case I ever need them), as it needed more strike than a home depot spring could provide. I sure hope the C-680s work, as it would be nice to have an affordable replacement for experimenting with.


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PostPosted: Wed Jan 15, 2014 11:46 am 
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The spring I'm currently using is a fraction wider than the stock spring. It barely fits into the end cap and hammer. Honing out both might be required if the spring you find is close enough.

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PostPosted: Thu Jan 16, 2014 6:22 pm 
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Joe?
Have you sen this about Daystate's Slingshot hammer?
2nd video.
http://daystate.com/huntsman.htm There is no audio component to it.

_________________
-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


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PostPosted: Thu Jan 16, 2014 7:05 pm 
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rrdstarr wrote:
Joe?
Have you sen this about Daystate's Slingshot hammer?
2nd video.
http://daystate.com/huntsman.htm There is no audio component to it.

The video doesn't show much about the hammer. However I did find some photos of the slingshot hammer and my version of it is nothing at all like I envisioned. I guess my idea should be called a throw hammer. Whatever name you might want to call it, I have tested both the stock version and my version with both the Hipac and C02 a number of times and each time the result,s were the same. more shots per fill, more consistent fps and better accuracy. I don't know what the best use of C02 is on record, by what gun. I would like to see some data regarding this, to compare. I think 50 shots at 475 fps avg is good, but there might be better result,s from a stock gun somewhere.

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PostPosted: Thu Jan 16, 2014 9:46 pm 
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Quote:
I don't know what the best use of C02 is on record, by what gun. I would like to see some data regarding this, to compare.

I managed a total of over 600 FPE from a 12 gr. cartridge (the blue line on the graph below).... That's about 130 shots at 520 fps avg. in .177.... Steve in NC over on the Green Forum held the previous record at 552 FPE in .22 cal....

Image

My current 2550 is doing pretty close to 400 FPE from a cartridge in .25 cal.... Anything up in that range (400 FPE total) is pretty decent from a 12 gr. CO2 cartridge, IMO.... 400 FPE is the equivalent of a PCP shooting at an efficiency of 1.00 FPE/CI, which is about average with a half decent tune....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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