This project was a collaboration between Bronc (Erik) and myself. The final product is Bronc's 4b bolt kit.
Development: (2008)
The goal was to create an upgrade bolt that could replace the previous Quest bolts, either the original stock OEM bolt or the slightly-upgraded Goldmember bolts. Development for this kit originally began in the spring of 2008; the project was shelved a few times, but the bolts were eventually finished halfway through 2010 and ready for sale afterward. The final design is a replacement for both the bolt and bolt pin. However, like many of my other replacement firing assemblies, neither upgrade part is compatible with the stock Quest bolt or bolt pin due to the drastic changes. In other words the 4b bolt kit cannot be mixed-and-matched with other Quest parts.
Here are the goals for the project, including general features of the bolt kit:
· Added bumpers for the forward and rearward bolt stroke. The bumpers are standard o-rings and are easily replaceable. They help to soften the movement and help improve bolt life.
· Completely redesigned bolt pin, featuring a two-piece design. No added o-rings.
· Internal volumizer within the new knob area.
· Tool-free removal and installation via a machined knob at the rear.
· Eliminate the stock bolt pin's loctite-sealed set screw. This is a potential leak spot that was nullified with the two-piece bolt pin design.
· Anti-rollback (ARB) bolt pin cone, designed to keep paintballs centered within the marker's chamber.
· New bolt face designed to take advantage of the ARB by cupping the ball around its crest, easing the transition through the breech o-ring into the barrel.
· Added tapers and roundings to the bolt's tip, designed to be more gentle on the ballstack, and ease the bolt's transition into the barrel.
· Optimized flow pattern through the inside of the bolt face (this is EXTREMELY different).
· Higher control over the amount of air released through the bolt porting.
· Modified dump chamber volume, minimizing the amount of wasted air for each shot. This was a popular "electrical tape mod" that could be done to the stock Quest bolt pins; the 4b bolt pin includes this as a standard feature.
· Improved bolt strength around the outside o-ring grooves.
· Quieter firing sound signature. This is due to the improved airflow along with the added bumpers for both the forward and rearward movement.
A nice render of the final, proposed design:
This project was lengthy due in part to the new bolt's completely redesigned flow pattern. I performed extensive testing on both versions of the factory bolts and had lots of ideas but the methods to impliment them wold prove difficult. My findings led to the conclusion that the factory bolts were designed with massive flow in some spots, but very constricted flow in others. This meant there was quite a bit of pressure shock during each shot, mainly at the transition into the bolt face where the airflow port shrinks to its smallest size. In practice this creates "dead spots" where pressure becomes bottled up and loses its potential energy. The act of adding angled transitions instead of abrupt 90º edges to the airflow path goes a long way to improve this; however it makes a product that is VERY difficult to machine correctly. The factory bolts represent a much easier bolt to produce, but control their airflow very poorly.
The second problem: the OEM bolt porting releases a huge amount of air per shot. The bolt ports exist on the largest diameter of any spool valve marker ever produced, and as stated above, pressure reaches a quick bottleneck down behind the bolt face. There's no reason for the bolt porting to be designed in this way, so I redesigned it to present a more "controlled" airflow.
Please observe the following diagram. It shows the exact amount of air volume that passes through the bolt during each shot, in graphical form.
Prototype 1:
After many stalled attempts at getting machine shops to make us a prototype, I decided to make one myself using manual machinery. Let me stress that these internals were NEVER meant to be machined on anything other than a CNC lathe due to their unusually curvy shape and complexity. I was able to successfully make a hand-machined version which took several hours to complete in total. At the time this was possibly the most difficult lathe workpiece I had made, but I was happy with the result...
With that finished, I began working on the prototype bolt....but I never got the chance to finish it because we ended up prototyping the bolt via CNC instead (due to the complex curves). oh well, the half-finished part is all I have now.
Prototype 2 & Production:
Partway during the prototyping, I begun working on a CNC version that was slightly more refined than the original ones. Around this same time I purchased a CNC lathe to be used for prototyping so the work proceeded relatively quick. Here’s a picture of the new bolt pin rear section during the first operation.
As soon as a full kit was prototyped, we immediately begun testing and refinement. I made a quick demo to assure people this bolt did indeed exist, and function correctly on top of it.
Throughout the testing process we did as much work as possible for the bolt kit's production. Here's the final fruit of the CNC's labor:
Several of the kits were assembled for long-term testing while the other ones were busy being anodized. I still use this raw bolt in one of my test Quests.
Below are some pictures of an internal cutaway model I made using defective workpieces. This helps to show the intricate internal geometry that is used to create all the features mentioned on this page.
Here's a finished kit, after having been anodized and packaged...
As you can tell from the above picture, the kits have been released and are available for sale by Thirtyfirst Outfitters located in California. Check the Thin Air Sports website for ordering information.
Performance & Results:
First, I have some unorganized thoughts on how things turned out (including some notes about the features being utilized in the design). You may find this interesting if trying to understand everything there is to know about this new firing assembly.
· The bolt was designed to be provide a slightly tighter fit onto the o-rings inside it. This was done as a stopguard against the moving o-rings leaking from one internal part of the firing assembly to another, only when the bolt moves. This problem can lead to all sorts of performance drops (unexplained loss of efficiency, mainly) and it's virtually impossible to diagnose since the marker doesn't seem to be leaking. There is virtually no performance difference with tighter o-rings....something I wish more developers would come to learn.
· In addition to the slightly tighter fit, there is an added undercut on the inside of the bolt. I included this as a way to theoretically allow a faster opening of the dump chamber. In reality I don't think this will actually make a difference, but only time will tell. HOWEVER the big thing is this causes the "catching feel" people have reported when moving the bolts by hand. It's normal, don't be worried :)
· If you are truely upset with the bolt's fit, you might be able to get away with using one-size-smaller o-ring on the bolt pin's three o-rings coming in contact with the bolt. Specfically, replace the three 14/70's with 13/70s instead. Please note that I don't really recommend doing this, since the 13/70 o-rings are not guaranteed to work correctly (was not designed to use them) plus the smaller 13/70 o-rings will be stretched out slightly more and theoretically wear out quicker. But it's up to you!
· During machining the bolt's slots were cut unusually rough. It was an artifact of how we machined the slots, which were the exact width of the endmill that was used to make them (Accupro solid carbide, 3 flute, 0.125" diameter, TiAlN coated). The endmill didn't have any room to make a "cleanup" pass which would smooth out the milled slots. After machining the slots were cleaned up to releive the sharp edges and ensure they don't trash the o-rings coming in contact with them.
· Suffice it to say, in the end the slots have a bit of a rough look to them. I figured this would be acceptable however people have also observed the roughness and mentioned it with a bit of confusion as to how it came to be. Like I said I'm not happy with how it turned out, and even less so now that I realized people noticed it. Naturally I won't make that same mistake next time, that's for sure!
· I'd like to revisit the tool-free removal, by making the knob easier to turn, yet no more pronounced visualy. Not sure if this is possible.
Now that the bolt is released I have an open ear to the populace on how to improve it in any way. These are the most common thoughts I hear from both our betatesters and people that bought the kit:
· Firing sound signature has dropped quite a bit.
· Most have reported an increase in efficiency even before adjusting the Quest parameters such as dwell or LPR pressure.
· Some have noticed the rough slot milling...see my lengthy note in the above paragraph.
· Many more have mentioned a drop in LPR pressure after installing the kit.
· I have heard at least two people mention a first shot sticking when the bolt is initially installed. I believe this is artifact of the shipping process and how the bolts are delivered without grease installed on the o-rings. If this is the case, the o-rings are getting squished down a little bit while the bolt is assembled, causing some temporary deformation. When you grease the o-rings and install it for the first time, the seals might need to contort a little bit to fit like they're intended.
MY ADVISE is to give the marker a short "break in" period prior to use. Dry fire the marker a few dozen times to get things moving. Regreasing after that isn't a bad idea either, since initial coats of grease like to be blown out of position after the fresh greasing (rebuild, o-ring install, etc).
· If you're one of the five or so people that received an "unbuffed" bolt pin, consider yourself lucky you got one of those parts. Most of the bolt pin knobs were buffed out to remove the machine marks but several slipped through the cracks that have some a "striped" look on the back of the knob. I thought it looked cool myself but not the guys in charge wanted them buffed clean.
· More to come...?!?!
If you have any questions or feedback in general, feel free to drop me an e-mail or post it on the forums someplace (PBN, Facebook, whatever). Please note that my responses on Facebook might appear as "Thin Air Sports" since I share the administrator account for the page. So a direct response from me might be masked.