Question: How do racquet manufacturers get air into the yoke?

Djokovicfan

Semi-Pro
On all the YouTube videos they show them hooking up air tubes tp the bottom of the tube (where the buttcap will be. But how do they inflate the cross section that connects each side of the throat? (is yoke the right term for this part of the racquet?)

Does it have a separate air supply from the racquet hoop? Do they just stuff the mold full of carbon fiber in this area so they don't have to inflate it?

Thanks to anybody who can answer....
 

Zoolander

Hall of Fame
The bridge? Good question. I thought the bridge was usually a solid piece or so it looks when you pull grommets out, though that one appears not, yes?
 

WestboroChe

Hall of Fame
At 3:09 the animation shows the bridge filling with air as the rest of the frame it. That would imply that they are cut and joined so that there is a channel between them. Of course they could also make a separate bridge (hollow or solid) and then glue it in. I would imagine both methods are used.
 

Djokovicfan

Semi-Pro
At 3:09 the animation shows the bridge filling with air as the rest of the frame it. That would imply that they are cut and joined so that there is a channel between them. Of course they could also make a separate bridge (hollow or solid) and then glue it in. I would imagine both methods are used.
> "separate piece and glue it in"
That sounds like apocalyptically dodgy engineering to just glue on a bridge. I would assume a racquet without a thoroughly bonded bridge would perform worse than a Chinese counterfeit pile of shizer.
 

Djokovicfan

Semi-Pro
The bridge? Good question. I thought the bridge was usually a solid piece or so it looks when you pull grommets out, though that one appears not, yes?
I'm just thinking about it being difficult to string an air tube together that connected the hoop to the bridge. It would have to be airtight, and I doubt it would be easy to put it all together. My guess is that they just use a shizer load of carbon fiber and just shove it into the bridge part of the mold, hoping that the heat will mold the bridge into form and afterwards they can sand the bridge down to size. Maybe they rely on the inflation of the hoop to exert pressure inwards on the bridge, compacting it into a solid piece of carbon that fills the entire bridge part of the mold?
 

WestboroChe

Hall of Fame
> "separate piece and glue it in"
That sounds like apocalyptically dodgy engineering to just glue on a bridge. I would assume a racquet without a thoroughly bonded bridge would perform worse than a Chinese counterfeit pile of shizer.
Not if it’s fitted properly. After all the frame is just carbon sheets glued together.
 

Djokovicfan

Semi-Pro
N
Not if it’s fitted properly. After all the frame is just carbon sheets glued together.
The bond between the bridge and the hoop would be weaker and less dynamic than carbon resin bonded to carbon resin. A separate bridge would not flex as congruently with the hoop under stress either.
Anyways, the video makes it pretty clear that glueing a piece to the throat is not the way they do it. The tech shoves a ton of carbon layers into the bridge.
 

insiderman

Semi-Pro
There is a "pellet" inside the wrapped fibers of the added throat area/piece that when being heated in the mould (when in the oven) "blows-up", (thus, expands) and then dissolves completely. A common / typical procedure with any carbon-based moulding process whereas their is a small piece that is needed to be added to the product, yet not fully a part of the main 'tube'.
 

WestboroChe

Hall of Fame
There is a "pellet" inside the wrapped fibers of the added throat area/piece that when being heated in the mould (when in the oven) "blows-up", (thus, expands) and then dissolves completely. A common / typical procedure with any carbon-based moulding process whereas their is a small piece that is needed to be added to the product, yet not fully a part of the main 'tube'.
That works.
 

WestboroChe

Hall of Fame
N


The bond between the bridge and the hoop would be weaker and less dynamic than carbon resin bonded to carbon resin. A separate bridge would not flex as congruently with the hoop under stress either.
Anyways, the video makes it pretty clear that glueing a piece to the throat is not the way they do it. The tech shoves a ton of carbon layers into the bridge.
The video is only applicable to the specific frame. And the problem you describe could be overcome via a spline made of layers of carbon over the joint.

It does seem like an inferior way to do it and I wouldn’t be surprised if it’s been tried in inferior racquets.
 

Djokovicfan

Semi-Pro
There is a "pellet" inside the wrapped fibers of the added throat area/piece that when being heated in the mould (when in the oven) "blows-up", (thus, expands) and then dissolves completely. A common / typical procedure with any carbon-based moulding process whereas their is a small piece that is needed to be added to the product, yet not fully a part of the main 'tube'.
Thats fantastic. When you say the pellet “dissolves” do you mean that after the string holes are drilled in the bridge the pellet is flushed out with a water or some solvent it dissolves in?
 

Racketdesign

Semi-Pro
There are a few variants on the materials used but essentially it's the same process. Carbon is wrapped around a small bag of PU beads or a rectangular piece of PU foam. The heat in the moulding process causes the PU to expand and push the carbon into shape whilst it cures. If you cut through the bridge section of a racket you will see a foam core which may not be present anywhere else in the hoop.
 

Zoolander

Hall of Fame
There are a few variants on the materials used but essentially it's the same process. Carbon is wrapped around a small bag of PU beads or a rectangular piece of PU foam. The heat in the moulding process causes the PU to expand and push the carbon into shape whilst it cures. If you cut through the bridge section of a racket you will see a foam core which may not be present anywhere else in the hoop.
Awesome! Thanks Paul for explaining. Im off to cut my racquet up!
 

Djokovicfan

Semi-Pro
By the way thanks insiderman and racquetdesign for explaining. I was literally pulling my hair out trying to figure out what was missing from all the 'how it's made' style racquet manufacturing videos.
 

Djokovicfan

Semi-Pro
One more question- is the effective pressure exerted by the pellet as high as the pressure applied to the hoop by the air supply? Also since the pellet will increase in pressure gradually as the mold is heated, is the air pressure increased slowly to balance with the pressure in the bridge pellet section? Or is the full air pressure applied right from the beginning?
 
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