I heard people talked about duel transfer port on the forum. But their idea was just drilling a hole through the probe, so you have a hole going straight through the probe. Imo that isnt really a duel transfer port, as the air is still going through only the bottom hole. Earnest just show a new version of a duel transfer port. It actually have 2 holes smaller holes, and air will go through both holes at same time. This imo is a true duel transfer port. Not the drilling a hole through the probe and call it duel port as air will only pass through one hole. How would this increase power over the single/standard port? My guess is, two smaller holes will act as 1 larger hole to let most air pass through, but are separated holes, so the pellet or slug will not dip into the port and jam like some of us are getting when we enlarge the port.
Duel transfer port vs single port?
- Thread starter 2fast2furious
- Start date
There won't be any benefit going above 100% bore size. The original dual port that Mr Rowe made was drilled straight through the brass and probe but also had a groove turned into the brass to let air go to the other side. Nothing will beat a well shaped single port.
Mr Rowe indicated in the comments of this youtube video that he will start selling power parts again via email from his website. Parts like these can be produced on a mill faster than hand shaped single ports so that's what it comes down to.
Mr Rowe indicated in the comments of this youtube video that he will start selling power parts again via email from his website. Parts like these can be produced on a mill faster than hand shaped single ports so that's what it comes down to.
Upvote 0
I wouldnt want 1 single 100% bore. It cause feeding problems and jams. I learned that first hand and had to order new one from fx usa. 2 smaller holes like his imo is the better choice to avoid jamming and any feeding problems and still have 100% bore.
Upvote 0
You misunderstand... you don't need to make the port wider to get 100% bore size(area), that's the purpose of lengthening it. Once you reach bore size you want to reduce resistance by making a smoother turn from vertical to horizontal.
Go to the kitchen and grab any spoon. Turn on the cold water in your sink fully. Hold the spoon between your thumb and finger so that it hangs loosely with the round side facing the water stream. Now move the spoon close enough that the round side touches the water.
See how the spoon gets sucked into the stream? This is caused by laminar flow and the reason you want a radius on your port from vertical to horizontal. Air flows almost exactly like water and the higher the pressure the thicker and heavier the air so it's harder to get it around a sharp turn.
Upvote 0
Wiith the dial port you have multiple benefits. First is the jamming issues are eliminated with the center support. Then you can obtain the perfect port sizes for a required air volume for optimal pressure, so there are no pressure difference between the port transitions. And lastly, and I think the most important, you will be able to contour the exit of the dual ports for optimal air flow into the barrel.
Upvote 0
Sir,
I’m curious if you mean full 100% through porting starting from where? Valve stem? TP? True flow through bolt systems like on old FX Elite or Air Force?
I’m also curious if by no benefit you mean for what most of us want. Or, in a very heavy slug, long barreled action, maybe even a dump valve. Would enlarging the TP to anything larger in diameter than the caliber of project show any gain?
@Dairyboy, very good you pointed out that another gun already has this system as I’d personally never take credit for something I didn’t invent or improve upon unless I directly stated where my inspiration came from. Do those bull pups with dual TP’s come in ambidextrous or lefty? Barrel brand & can I put my own 28-36” custom made barrel on one or would a tensioning system reliant on reservoir size limit my barrel length?
Upvote 0
I built a gun with a duel port. Works great.
Derrick Wall - Sent me a photo (below) of a dual port that I used to make mine.
The .300" TP in my gun would have allowed a .25 cal. slug to fall in during loading. The center support was mandatory, not an option.
I just made the two sides a total of .300" volume, plus an additional 20 % to cover any flow restriction factor. It needs to be machined "exactly" like the one in the photo. Angled post cuts with a ball end mill radius in the bottom, smooth edges ect........
I would use that design any time. My next build will have it for the same reason, the transfer port is larger than the barrel diameter.
Some things are more important than a "possible" small loss of efficiency.
Derrick Wall - Sent me a photo (below) of a dual port that I used to make mine.
The .300" TP in my gun would have allowed a .25 cal. slug to fall in during loading. The center support was mandatory, not an option.
I just made the two sides a total of .300" volume, plus an additional 20 % to cover any flow restriction factor. It needs to be machined "exactly" like the one in the photo. Angled post cuts with a ball end mill radius in the bottom, smooth edges ect........
I would use that design any time. My next build will have it for the same reason, the transfer port is larger than the barrel diameter.
Some things are more important than a "possible" small loss of efficiency.
Upvote 0
I built a gun with a duel port. Works great.
Derrick Wall - Sent me a photo (below) of a dual port that I used to make mine.
The .300" TP in my gun would have allowed a .25 cal. slug to fall in during loading. The center support was mandatory, not an option.
I just made the two sides a total of .300" volume, plus an additional 20 % to cover any flow restriction factor. It needs to be machined "exactly" like the one in the photo. Angled post cuts with a ball end mill radius in the bottom, smooth edges ect........
I would use that design any time. My next build will have it for the same reason, the transfer port is larger than the barrel diameter.
Some things are more important than a "possible" small loss of efficiency.
Great example of how you can make a dual port flow air the most efficiently and minimizing turbulence! Thanks for sharing.
Upvote 0
Please don't read this as negative or arguing. My goal is simply to educate on a subject I'm comfortable with.
There is no jamming issue whatsoever when the single port is done correctly. The gun will feed anything the same as unmodified. Messing up the port by making it wider is not a design flaw it's an execution mistake. Unless you're trying to drop down to 12 fpe the modified single will be most efficient by having the least restriction. To shoot 18gr jsb at normal speed in my 700mm .22 I would have the regulator in the 80-90 bar range. That's with a 5.8mm valve seat and without the larger plenums. Where most people make a mistake is in not turning the 90 degree angle into a radius from the single port into the barrel to reduce pressure drop. There's no need to reinvent the wheel. Splitting one sidewalk into two and then merging them back into one doesn't allow the one to move more people.
Upvote 0
My reference was to the barrel in this case but 100% porting is the goal from the plenum to the barrel. The valve should be as large as you can use without causing other problems and the ports should be at least as large as the barrel ID. Working in the constraints of the Impact, having the pellet inlet port larger than the barrel ID won't give any benefit. By lengthening the port you effectively reduce the 90 degree angle into the barrel but a radius is still better than making the entire port maximum length.
Upvote 0
Good News!! The Taipan Veteran if you can find one has the duel transfer port already as manufactured. Great efficiency
Upvote 0
Can you show us a pic of what a radius port looks like? How do you make a radius port on the impact?
Upvote 0
Here's a ruff exaggerated drawing. I can't get an actual picture to focus. the flare at the bottom covers the port that feeds it and you make the radius while elongating the port. If you move the whole front wall of the port forward then you would still have a 90 degree junction rather that the radius. The flare is blended deep into the port for smoother airflow, like a nozzle.
Upvote 0
Dual transfer ports (bridge port) are used on other guns because there is not enough room to extend a single port forward to make it the same area as the barrel ID and they can't go wider without a bridge because pellets would tip into the port.
Upvote 0
I built a gun with a duel port. Works great.
Derrick Wall - Sent me a photo (below) of a dual port that I used to make mine.
The .300" TP in my gun would have allowed a .25 cal. slug to fall in during loading. The center support was mandatory, not an option.
I just made the two sides a total of .300" volume, plus an additional 20 % to cover any flow restriction factor. It needs to be machined "exactly" like the one in the photo. Angled post cuts with a ball end mill radius in the bottom, smooth edges ect........
I would use that design any time. My next build will have it for the same reason, the transfer port is larger than the barrel diameter.
Some things are more important than a "possible" small loss of efficiency.
Well done!
Upvote 0
Just from looking at pictures it doesn't apply to this specific airgun but it's an old idea for getting greater than bore size amounts of air.
John
John
Upvote 0