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Discussion Starter #1 (Edited)
Shibuya DX Plunger Button vs Avalon Classic Button, the 7 dollar plunger

Those of you who regularly check in on alternative services may have noticed the appearance of a new budget plunger button. It is labeled the Avalon Classic Button, and from a quick glance appears to be nearly identical to the Shibuya DX plunger. Wanting a second plunger for my indoor arrows, I picked one up and figured I would share my findings for those interested in what looks like a Shibuya for a fraction of the price.

Please note that at this point I have not used the Avalon yet, but will update after testing it with my current arrows instead of my Shibuya. My current shibuya has been my main plunger for the past 10 months.

The Avalon was purchased on alternatives for ~$7
The Shibuya was purchased from lancaster through amazon for ~$35 (I believe it is $25 on alternatives)

First, several pictures:
IMG_2347.jpg
Avalon Clasic Button in original packaging. Note that as with the shibuya it comes with 2 hex wrenches, three springs, and two tips. This one comes with what appears as two plastic tips, where the shibuya comes with one teflon and one metal gold tipped.

After opening, I used the press together method and my riser to duplicate the pressure and center-shot settings. A side by side comparison of the plunger buttons:

(In all Avalon is the lighter one with the shinier finish, Shibuya is the darker threaded one with matte finish. Additionally the Avalon can be identified by what looks like thread scoring on the front of the metal barrel where the plastic tip comes out)
IMG_2351.jpg
IMG_2352.jpg
IMG_2353.jpg

And Finally what they both come with: (minus the zip storage bag and instructions the shibuya comes with)
IMG_2356.jpg

Summary of similarities:
1. Same form factor, operation, and weight (16g).
2. Same three (light, medium, heavy) tension springs.
3. Same hex wrenches.

Summary of differences:
1. Shibuya comes with a plastic storage bag.
2. Shibuya has one teflon tip, one metal tip, avalon has two plastic (feels like delrin maybe?) tips.
3. The avalon tip is ever so slightly longer, requiring 1/4 turn less to match center shot.
4. Tip material and shape is slightly different. On the avalon, the pressure curve is more even, but can feel the sides of the interior chamber slide against the tip. The shibuya is smooth enough (possibly just worn in) not to feel this, but has a less linear pressure curve where curve is steeper the further in you go, but does not apply as even pressure from the beginning.
5. Tolerances on the avalon are slightly looser for the pressure screw, when locking nut loosened the screw can wobble.
6. The material on the wrenches for the avalon bend easily.

As I feel some of the differences may just be from the shibuya being worn in already, I will update after several hundred arrows. In general though, right now this really looks like what you see is what you get, to me it is a slightly cheaper machined Shibuya DX, with the same adjustment and lock-up. I would not use this instead of my shibuya, but I think I may end up using it side by side for my indoor arrows or as a backup plunger.

Extra Note: You may have noticed the shibuya locking screws are different colors, this is because when I first got it I forgot to tighten the socket screws after tuning and lost two of them. These were very easily replaced, as this design takes a standard socket screw. For about $5 on eBay including shipping, you can get a 4 pack of (mine were DU-BRO 2168) 3mm x 3 Socket Set Screws, which for me fit perfectly.
 

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It looks like basically any budget plunger, just this time in the shape of Shibuya.
I like the fact that it has a plastic piston/tip however. I always avoid plungers with metal pistons.
The progressivity of the spring action is what makes the Shibuya good. Not the shape. If this has a linear/even pressure curve, it not going to shoot as well as the original.
 

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Discussion Starter #3
Ok, it makes sense to me that the pressure curve could change arrow flight, but what specific aspect?

Let's say you have two identical plungers otherwise, (let's say two shibuya or beiter) and one has a more linear pressure curve.
If you have the tension setting tuned so that at the same amount of flex on the arrow they have applied the same amount of pressure, why would it cause a noticeable grouping difference?
If at the same flex point and time, the correct amount of pressure is being applied by either plunger, shouldn't either of them be able to tune a good group?

If I take just the spring from the avalon and put it in the shibuya and re-bareshaft tune, would I get worse groups / more arrow wear?
Or is it just that the spring will wear out faster because it is applying more pressure earlier?
(^Now I really want to try this as the springs appear compatible)
 

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There are two things that are really important in a plunger, apart from the obvious that the precision in the mechanics have to be good enough to provide a smooth, reliable action.

Nr 1 (and also priority 1): The weight of the piston.
According to my experience, lighter is always better here. It doesn´t matter how good the spring characteristics is if the piston is heavy. The reason is that a heavy piston is too slow to react, both inwards and to return during the extreme short amount of time where it have contact with the arrow. The plunger only have about 3-6 thousands of a second of time to move. The lighter, the piston, the more "pure spring action" you get instead of a dominating moment of inertia from a heavy piston. A lighter piston does not only shoot better. It is also a lot easier to tune, since spring adjustments have a more logical impact on groups and hits when the effect of inertia is reduced. I made some tests once where I compared different pistons from very heavy (added weights) to very light (ultra light modified pistons) and the difference is very clear. Light is good. Heavy is bad. The test was btw made to see if a, back then recently introduced, magnetic plunger with extreme progressivity was good or not. It didn´t work at all, no matter how nice the magnetic action was, and the reason was piston weight.

Nr 2 (second priority): The spring character.
In most applications when springs are used, you want a spring with a "linear" behavior. In archery in the shape of a plunger however, you want the opposite which is often called a progressive spring. The term linear is commonly used, but is not really teoretically or mathematically correct. What we mean is that the first mm of compression needs the same amount of force like the last mm of compression, so it´s might be better to call it constant force plunger or whatever, but since linear is well known, I'll stay with that. Progressive means instead that the force needed to compress the spring gets higher and higher the further the compression goes.

What happens in a shot is that after the release, the arrow bends towards the riser and compress the plunger at one single time. Both the amount of bending and the exact position of the string and shaft varies slightly from shot to shot, depending on shot quality. That variation leads to that the plunger piston is pushed in slightly different from shot to shot, especially if you compare a good and a bad shot. Some shots creates less plunger compression and some shots creates more plunger compression. If you have a progressive spring, it will be more easily compressed until the normal point during shots that pushes less on the plunger, and then it will resist to be compressed any longer than the normal point on shots that pushes more on the plunger. That means that the sideway angle of how the arrow leaves the bow will vary less with a progressive spring character. This leads, ofcourse, to better groups.


You will be able to tune the bow perfectly with any of the plungers or springs, as long as you shoot (olympic) recurve, and by perfectly mean that the bareshaft hit right in the fletched group. The difference will instead be seen in grouping in the long run. You will, almost surely, shoot slightly more points with the more progressive plunger. The only situation where I prefer a linear and also soft plunger is indoors with really thick and long aluminium arrows. For some reason, I tend to group better with linear plungers then.

If you shoot WA barebow(stringwalking), however, you will not be able to get a good tune with the linear plunger. You will then get to much variation on short and long distances, because of the different forces delivered into the arrow on different crawls.

The Shibuya is very good when it comes to not wearing arrows out. Probably the Avalon copy is too. What you should avoid if you worry about arrow wear is fiber reinforced pistons without teflon/brass tips. The springs normally never wears out, even in very low cost plungers. What you could do however, is to put all pistons on a scale and choose the lightest one. That plus the any of the Shibuya springs will most likely be the best best shooting combo, no matter if its the Avalon or the Shibuya parts.


Ok, it makes sense to me that the pressure curve could change arrow flight, but what specific aspect?

Let's say you have two identical plungers otherwise, (let's say two shibuya or beiter) and one has a more linear pressure curve.
If you have the tension setting tuned so that at the same amount of flex on the arrow they have applied the same amount of pressure, why would it cause a noticeable grouping difference?
If at the same flex point and time, the correct amount of pressure is being applied by either plunger, shouldn't either of them be able to tune a good group?

If I take just the spring from the avalon and put it in the shibuya and re-bareshaft tune, would I get worse groups / more arrow wear?
Or is it just that the spring will wear out faster because it is applying more pressure earlier?
(^Now I really want to try this as the springs appear compatible)
 
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