Rolling Thunder Comp Simulation Video

[Meat Target]

Here is a simulation video on the Rolling Thunder compensator I was playing around with.

Rolling Thunder Sim Video

After seeing that a lot of the big name 3 gun competitors were running the Rolling Thunder I figured I would do an analysis on it to find out what the deal is.

Didn't find anything special, just about average in performance as far as I can tell.

Here is a comparison with a simulation done on the Miculek comp.

As you can see from the graphs the Miculek comp works better for recoil but the Rolling Thunder has a slight edge on force pushing down. The results are similar to the findings from the compensator comparison article that Patrick Kelley published in Nov/Dec 2009 issue of Front Sight. Recoil reduction: Miculek 65%, Rolling Thunder 57%.

Not really sure why the big guns are using it, maybe the extra weight up front helps out? But I am also guessing that if some of these guys stuck a potato on the end of their rifle they would still win most of the matches.

Link to the Miculek comp simulation video: Miculek comp video

*Note: The forces shown in the Miculek video are a little higher than shown in the comparison graph. The comparison graph results were calculated at a higher resolution and are more accurate.

I also did a sim on a pistol compensator in the Open Pistols forum if anyone is interested. Pistol Comp post

And would someone please tell me how you embed the Youtube player into the posts. I have tried every combination of insert links I can think of.

Thanks.

[MarkCO]

I assume your modeling does not account for adiabatic expansion? When you toss that in, the numbers change, but the comparisons are still valid between the two. Pretty easy to see why the RT fouls the muzzle so bad as your model is pretty close in showing that the quenching temperature occurs back at the muzzle face due to the expansion chamber.

Edited January 24, 2014 by MarkCO

[TitoR]

Meat Target, I was wondering if there is an error in creating the down force chart above, since in the video of the miculek comp the down force varies from -50 to -85 N, but in the chart above, only -50 to -65. If plotted according to the video's chart both comps would be about the same, with a smoother force contour from the miculek. JMTC

[TitoR]

One more thing, looks like the rolling thunders last baffle is not used, while the Miculek's still contributed about 15% of the total force pushing forward. Maybe a shorter RT with only two baffles may help making it lighter.

[kurtm]

All this modeling seems to be taking the discarge as a gas, while I think it is more like a plasma. The "gas" collum is carrying alot more than just hot air, copper and lead vapor, carbon etc. Gas modeling is good for a comparison, but I don't think it tells the real story. BTW Mark is right about the quentch area...but it is a small price to pay. Just take it off occasionally and clean the crown. All compairison modeling is great, but it is how the comp interfaces with the rest of the package as to how effective it is, meaning rifle and rifle holder. I have shot a bunch of comps and what feels great on one rifle will not be good on another. Internal ballistics of the barrel and gas system effect each comp differently and each barrel/gas system is different. Think finger prints and snow flakes! And dare I say that is why there are a whole bunch of comps on the market.

Edited January 24, 2014 by kurtm

[P.E. Kelley]

Damn it Kurt!!!! Their can be only one! (best comp) The one you say or I say or Mark says. Or the internet says, or somebody else says.

I love the science behind all this but with so many comps that WORK....pick one and.....wait for it....wait for it....PRACTICE!

[larry weeks]

Kurt is correct about shooters, in my limited experience, and a smart guy overall. I've tuned my RT for me. Jerry was at our range, saw mine and asked to shoot it. He said, "It goes low left pretty hard, doesn't it?" It doesn't go low left for me, sometimes I think it is still moving right. If I relax my grip a bit, it goes right, hold tight, dead on. Seeing the scientific stuff is darn cool though and it's neat that we have folks on here who can do that sort of thing.

[iswope]

The science behind this is pretty fascinating but I think practice is the key. Regardless of comp used it becomes part of the whole of your rifle. People often approach the rifle as just a collection of parts, and in some ways it is, but a fully assembled rifle becomes a unique whole of its own and I've never seen 2 that shoot the same even when using the same comp as so many other factors play into it.

[MarkCO]

Some of you have seen my new comp and know how much "math" time I spent on it, but the final design still had some tweaks that were derived from experience and understanding of the system and the interactions of the variables. For those of you without an engineering background, any good, and honest, engineer will tell you that the models and the computer programs produce "approximations" based on multiple assumptions and that is why you don't go make anything based off a math model...or why that bridge has a factor of safety of like 3x. So don't get too twisted up in models, performance in the hands is what really matters.

[CarRacer]

Other factors play into it as well. I picked up a Rolling Thunder because I got it for $40. I know it's not the ideal choice based on reading what people with a ton more experience, who know what they're talking about, write.

I bought it because it was better than my birdcage FH and it was cheap. I still find it interesting too see posts like this though, as more data to make decisions with is a good thing and it's fun to learn how things work.

[kurtm]

" I know it's not the ideal choice "

Ahem, there are many top shooters that use the roller, many of them think it is ideal. Don't feel like you got the red headed step son!

[Therealkoop]

I have extra holes drilled in my RT.

It makes things different.

Never tried the Miculek so cant say. Awesome video, very interesting. Maybe Ill get an RT and cut the last baffle off, making it legal length for some of the local "non gamer" matches. (The ones where everyone just runs a surefire or PWS but makes me take off the RT).

Edited January 24, 2014 by Therealkoop

[Meat Target]

I assume your modeling does not account for adiabatic expansion? When you toss that in, the numbers change, but the comparisons are still valid between the two. Pretty easy to see why the RT fouls the muzzle so bad as your model is pretty close in showing that the quenching temperature occurs back at the muzzle face due to the expansion chamber.

The simulation was run using propellant gas temperature and ratio of specific heats obtained from military research documents on the CFD analysis of rifle muzzle blasts. That’s the best information on the properties of propellant gases I have found so far. But it did not calculate heat transferred into the muzzle brake as it had very little effect on the results.

Here is a picture of the gas temperatures at 0.0002 sec once everything has stabilized a bit.

You are right about the muzzle face it does take quite a beating.

[Meat Target]

Meat Target, I was wondering if there is an error in creating the down force chart above, since in the video of the miculek comp the down force varies from -50 to -85 N, but in the chart above, only -50 to -65. If plotted according to the video's chart both comps would be about the same, with a smoother force contour from the miculek. JMTC

Nice catch, but you missed my disclaimer " *Note: The forces shown in the Miculek video are a little higher than shown in the comparison graph. The comparison graph results were calculated at a higher resolution and are more accurate."

One more thing, looks like the rolling thunders last baffle is not used, while the Miculek's still contributed about 15% of the total force pushing forward. Maybe a shorter RT with only two baffles may help making it lighter

If the compensator is designed well two ports is all you realy need. The Mickulek comp's ports are a lot smaller so a bunch of gas makes it to the third port.

Edited January 25, 2014 by Meat Target

[alma]

Any chance you can do the same comparison with the Seekins ATC comp?

[Meat Target]

All this modeling seems to be taking the discarge as a gas, while I think it is more like a plasma. The "gas" collum is carrying alot more than just hot air, copper and lead vapor, carbon etc. Gas modeling is good for a comparison, but I don't think it tells the real story. BTW Mark is right about the quentch area...but it is a small price to pay. Just take it off occasionally and clean the crown. All compairison modeling is great, but it is how the comp interfaces with the rest of the package as to how effective it is, meaning rifle and rifle holder. I have shot a bunch of comps and what feels great on one rifle will not be good on another. Internal ballistics of the barrel and gas system effect each comp differently and each barrel/gas system is different. Think finger prints and snow flakes! And dare I say that is why there are a whole bunch of comps on the market.

Some of you have seen my new comp and know how much "math" time I spent on it, but the final design still had some tweaks that were derived from experience and understanding of the system and the interactions of the variables. For those of you without an engineering background, any good, and honest, engineer will tell you that the models and the computer programs produce "approximations" based on multiple assumptions and that is why you don't go make anything based off a math model...or why that bridge has a factor of safety of like 3x. So don't get too twisted up in models, performance in the hands is what really matters.

I totally agree with both of you in that there are a lot of other factors involved that can't be simulated on the computer. Simulations are just another tool to play with, at least it can give you an idea of what going on and may help out in the design process. But Its a lot better than guessing and randomly drilling holes into a chunk of metal.

I do have a design that shows a 25% improvement in recoil reduction over the Miculek comp but that doesn't mean that it will work better in the end. In reality with the AR platform once you get to certain amount of recoil reduction the bolt cycling will have a bigger influence on barrel movement. It could be that the weight of the compensator and balance of the rifle will have a bigger influence over the amount of recoil reduction.

Just sharing some work I have done, not trying to sell anyone on it.

Edited January 25, 2014 by Meat Target

[TRUBL]

Mark,

I've seen your comp.......looks nice and I like it......HOWEVER; I am still waiting for Mr. Kelly to actually say it is the best comp out there before I ask you to make one for a .625 barrel.

Edited January 25, 2014 by TRUBL

[Meat Target]

Here is something interesting that I had a feeling about when I first saw the Rolling Thunder comp. If you flip the hole pattern around it should work a little better for recoil reduction.

[Jesse Tischauser]

Dammit I've been working on a reverse rolling thunder design and now you have ruined it. I already have a cleaver name too. The Thunder Rolls Comp.

I too would like to see the Seekins ATC. I'm luvin' it!

Edited January 26, 2014 by Jesse Tischauser

[alma]

Rednuht Gnillor comp?

[Meat Target]

Dammit I've been working on a reverse rolling thunder design and now you have ruined it. I already have a cleaver name too. The Thunder Rolls Comp.

I too would like to see the Seekins ATC. I'm luvin' it!

If someone has a good CAD model of the ATC they would send me I could do a run on it. Another popular comp that I would like to do a simulation on sometime is the SJC Titan.

Kind of hard to justify dropping the money on them just to get some measurements.

[waktasz]

I have an old Titan that is sitting collecting rust in my garage if you want it. I took it off to clean and test a different comp and it's totally rusted over now. Oops. I guess the solvent I used took off the blueing?

Edited January 26, 2014 by waktasz