Meat Target Posted December 17, 2013 Author Share Posted December 17, 2013 I use smaller ports in my comps. I have bad elbows and I made a bunch of comps with different size ports, different number of ports, different shaped ports, and it seems, at least for me, that having smaller ports (which results in more vertical surfaces for the gas to push against) feels better on my elbows. Others have also noticed that my comp doesn't have a lot of flame or gas coming out the top. I figure all that flame and smoke coming out the top (of other comps) is gas/pressure that can't be used to reduce felt recoil. Anyway, the smaller ports seem to work good for me. I also add an area between the end of the barrel and first port for the gas to expand before it hits the first port. I haven't done any flow model like you but my setup seems to work pretty good. It would be cool to see my design run through your model. D [edited for typo] The real trick to compensator design is with the spacing of the baffles, if it’s too close a lot of gas goes through the hole in the baffle if it’s too far away then the gas expands and misses the baffle surface. There is a sweet spot which balances these two losses. As you have found out that typically smaller ports closest to the barrel “high pressure port” work better (at least in simulation anyways). As the gas passes through each baffle the pressure drops and the gas expands at a lower angle making the “sweep spot” farther away than the preceding baffle distance. Looking at the compensators on the market most seem to be designed backwards from this in that they have the largest port first and then the smaller ports. With muzzle flash that’s a whole other science that’s harder to predict. But my best guess would be the high pressure of the small port allows the gas to expand at a quicker rate cooling it faster before the gas mixes with enough air and a secondary flash can occur. Link to comment Share on other sites More sharing options...
Snapple Posted December 17, 2013 Share Posted December 17, 2013 Very interesting! Link to comment Share on other sites More sharing options...
Meat Target Posted December 18, 2013 Author Share Posted December 18, 2013 Here is another simulation I did of a very popular rifle compensator. Not quite as interesting as the pistol compensator sim. http://youtu.be/ihGolwXN54s Link to comment Share on other sites More sharing options...
jid2 Posted December 18, 2013 Share Posted December 18, 2013 Last two baffles don't do much! Link to comment Share on other sites More sharing options...
jid2 Posted February 10, 2014 Share Posted February 10, 2014 (edited) Thanks to Mike for helping me with the CFD model setup! I spent the last week going through lots of iterations on compensator designs. Going through the simulations helped me understand some basic stuff that you sometimes over look. Here are a few of my notes. - Holes in the barrel create downward force, they do not put much into pulling the gun forward. - You can balance more down vs forward effect from the comp by using holes in the barrel. If you have no holes then you get more gas flow through the comp. - Holes in the barrel make a big force spike down at the start of the pressure cycle. Not sure if this is good or bad, but it's there. - Ports want to get bigger as you move away from the muzzle and loose pressure as Mike said. - Shape of the port can effect how efficient the gas is used. Since my barrel already has two 3/16" diameter holes in it, that's what I designed around, along with the use of the EGW ream which is .369". I wanted to get as much downward force as I could (flat shooting). With different port layouts you can reverse the effect and get more forward pull. But I wanted as much down as I could given my existing barrel holes. Reviewing data from other comp designs shows that anything works to create some force down and forward, but you can tweak the balance for sure. With that, I got this. Machined with love and care from Titanium. Based on everything I can find this is the lightest comp out there. It weights 1.78oz, which was important to me because I have a heavy (2.6oz) Akai comp on my gun right now and I really don't like how front heavy it is. It ended up longer than I had planned, but the data wanted it just the way it is - so I obeyed. There are some more photos in the gunsmith section in the CNC thread. Edited February 10, 2014 by jid2 Link to comment Share on other sites More sharing options...
Aircooled6racer Posted February 11, 2014 Share Posted February 11, 2014 Hello: Interesteing design. Not sure it is going to work that well with that large last port. The side ports on the last port will not be doing much and will not be needed. The real test will be in the shooting of the comp on the gun. Thanks, Eric Link to comment Share on other sites More sharing options...
jid2 Posted February 11, 2014 Share Posted February 11, 2014 ^^^ That's what your eyes tell you from looking at comps that are just built off of gut feel. The data says that the last port should be that big. The last port is a small contributor to the overall force in general, but the goal is to make it as effective as possible. I didn't want to sacrifice potential flatness by putting the side bleeders in port 1 or port 2, but I wanted some amount of side venting. But yeah, we will see how it shoots, there is a chance that real engineering analysis isn't smarter than a dude making stuff up on his own. I'm pretty confident in it, and if nothing else looking forward to the gun having better balance. Link to comment Share on other sites More sharing options...
frankie Posted February 11, 2014 Share Posted February 11, 2014 keep us posted on your results. I also have 2 3/16 holes in my barrel. Link to comment Share on other sites More sharing options...
B45C22 Posted February 11, 2014 Share Posted February 11, 2014 My guess is that you will feel. Much more noticeable difference in felt recoil with different combinations of bullet weights and powders that with a huge range of different comps. I have shot most of them and the biggest difference is between loads, not comps. That being said, I'd love to hear your results. Link to comment Share on other sites More sharing options...
jid2 Posted February 11, 2014 Share Posted February 11, 2014 (edited) Here's a plot of the comp with everything exactly the same, but with and without the holes in the barrel. These are two 3/16" holes. I haven't played with different holes sizes etc. You can see that the combination of these holes along with the comp work really well. It would be interesting to see if you can create a comp alone that can get near this especially in the Z force down. The holes leverage the higher pressure in the barrel. I might play around a little and see what I can come up with without using holes. But I find the 3/16" holes to be very pleasant. I didn't notice any increased noise or blast when I first added them to my other gun, which is why I put them in the new gun as well. The holes take away a little of the X force in the start of the pressure cycle, but you can see a major improvement in the Z force down. It's also worth noting that the first .0002 seconds of simulation would be effected by the bullet passing through, so those first sections of the graphs should be used for more of a reference. Edited February 11, 2014 by jid2 Link to comment Share on other sites More sharing options...
McCringleberry Posted February 11, 2014 Share Posted February 11, 2014 I was just going to ask that about having holes versus no holes in the barrel. With my first Open gun, I have two holes (I think 3/16) and it took a lot of powder to make Major. So on the next few builds, I got them without barrel holes and it's easy to make Major but I have noticed more movement. However, there has got to be a way to make the comp work the load and not having to drill into the barrel. What about making the comp so that first section simulates the barrel, put holes there, then open up to the chambers? Might be sort of long but with Ti, you can still make it lightweight. One of the best comps I've used so far has been the Dawson DP2 so something with length may not be a bad thing. Thanks for all the time and work you guys are putting into this! Link to comment Share on other sites More sharing options...
Aircooled6racer Posted February 12, 2014 Share Posted February 12, 2014 Hello: If the comp is designed correctly then you don't need any barrel holes. I would be interested in your results after you shoot your comp as well. I know it may take more than one prototype to find the one that works the best. It took me about 8 or so before I felt I have the correct one. Let us know. Thanks, Eric Link to comment Share on other sites More sharing options...
jid2 Posted February 12, 2014 Share Posted February 12, 2014 (edited) The great thing about the simulation is that I'm on my 35th prototype right now and I've only had to build one of them. I've got the comp installed on the gun now, so I should be able to go test it out this weekend. I expect the gun to feel more balanced than it did before, which just pointing it around I already like it more. I also expect the dot to track a little better up and down with less movement than before. I'm traveling for a few days and will run some simulation without holes and see if I can get something with a similar force curve from the comp itself. I saw your heart shaped ports on the Open Gun thread Eric, I'll run those through and see what they look like. Here's a graph showing my comp with different size barrel holes: .125", .187" and .25". When I originally put holes in my barrel I thought that 1/8" was too small, and I knew that 1/4" was too obnoxious, which is why I landed at 3/16". The data shows that 1/8" makes only a slight difference over no holes at all, they are too small to get any real flow out of them. And 1/4" are pretty serious, which for 9mm Major is likely a bit too much. Here's that plot below. Edited February 12, 2014 by jid2 Link to comment Share on other sites More sharing options...
Shadow Posted February 12, 2014 Share Posted February 12, 2014 (edited) How about trying the other way too, and run a model/s with 4 barrel holes? Edited February 12, 2014 by Shadow Link to comment Share on other sites More sharing options...
Iceman2733 Posted February 12, 2014 Share Posted February 12, 2014 ^^^ That's what your eyes tell you from looking at comps that are just built off of gut feel. The data says that the last port should be that big. The last port is a small contributor to the overall force in general, but the goal is to make it as effective as possible. I didn't want to sacrifice potential flatness by putting the side bleeders in port 1 or port 2, but I wanted some amount of side venting. But yeah, we will see how it shoots, there is a chance that real engineering analysis isn't smarter than a dude making stuff up on his own. I'm pretty confident in it, and if nothing else looking forward to the gun having better balance. You guys are doing amazing work. Question tho you say you didn't want to sacrifice flatness by putting side bleeders in port 1, could you elobarate on that. Please do not take it as me being rude I am curious of the affect of putting bleeders holes in port 1. I have a Dawsome DP2 TJ which I agree is awesome!!! and I am looking at purchasing another for another build down the road but now this has me wondering wheather to purchase the TJ which has a bleeder hole in port 1 and port 4 or just the standard DP2 comp. Please keep up your great work man I think you are guys are onto something awesome Link to comment Share on other sites More sharing options...
andersonj55126 Posted February 12, 2014 Share Posted February 12, 2014 My gun smith has designed his own comp and he talks a lot about the timing of the comp and how it can extend the duration of lockup. When simulating a comp design is the X axis or the pull forward on the barrel what drives the timing of the comp. Link to comment Share on other sites More sharing options...
jerson0208 Posted February 22, 2014 Share Posted February 22, 2014 I'm interested to see how it performs at the range. Keep us posted when you get a chance to shoot it. Link to comment Share on other sites More sharing options...
jid2 Posted February 22, 2014 Share Posted February 22, 2014 I shot a match last weekend, first one in a long time so I was good and rusty! The comp performed exactly how I thought it would. Based on the simulation it was looking to be a little better, and flatter than my Akai comp. And it was much lighter. I am really digging the balance of the gun now. I was unhappy with how front heavy it was with the Akai since the second I put it on, and building a titanium comp has been on my to do list since then. As I said, I feel like there was a small but noticeable improvement with how the gun tracked up and down, and a major improvement in overall balance with less weight hanging out there. I'm very happy with this setup now. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now