ADA: Ask Doc Anything!

[DocsMachine]

It gets really complicated when you consider heavier hammers and lighter springs really help get the pressure down, which in turn helps with efficiency.

Nope, sorry. Low pressure is a side effect, not a goal. That is, making the gun efficient often allows you to lower the pressure. Very often, if you shoot specifically for LP, it makes it less efficient.

The classic example is the old 'shoebox' Shocker versus something like a Phantom. The shoebox is one of the lowest-operating-pressure markers ever made, usually running around 160 to 170 psi. It's also widely famous for being one of the least gas efficient markers ever made. On the other hand, the Phantom runs straight, unregulated CO2, about 850 psi, and is considered one of the most air-efficient guns made.

Yes, that's comparing apples to pomegranates, but it illustrates the point: just making it low pressure does not make it efficient. The only way simply forcing the op pressure down 'adds' to efficiency, is it lets you go 'deeper' into the tank. That is, if one gun runs at 450 psi, and another at 180 psi, the other can use that additional 270 psi before losing velocity.

In a 'Cocker, a heavier hammer, in my experience, almost always leads to reduced air efficiency. Again, it has to do with valve dwell- how quickly the valve can open and close. That was the whole point behind the Tornado- the poppet was a fair percentage lighter than in other valves, and the relatively large cup seal area added to the 'push' of the air pressure in the chamber to help close it.

I would like to point out, however, that AKA springs are not all that heavy by comparison.

-Nobody ever said they were. What they were, were weighted about right for the average Tornado install. Made so you could buy a ready-to-go two spring kit, rather than an eight-spring suite and do a lot of tuning and testing.

I also must disagree with the statement about lightning bolts; at least when discussing cockers, lightning bolts are for sure the most efficient bolts ever made.

-Nope. They're good, yes, but still suffer from the standard problem- the port expands in volume as it extends towards the ball. That allows the gas column to expand before it hits the ball, and thus wastes some of it's energy.

The most efficient bolt is one that maintains the valve exhaust port size all the way from the valve to the surface of the ball. If the column of pressurized gas is only allowed to expand as little as possible before imparting it's energy on the ball, that uses the air as efficiently as possible.

I have actually done some research of my own on this. I just don't have it on YouTube because I did it before YouTube existed.

Back when I was playing with the Fastbacks, one of the things I did in fact develop for it was the bolt. Sergei wanted a huge open bolt because that's what everybody else was making. I tried a couple designs, and eventually went back to what Bud Orr told me personally, when he was up here for an APL tournament in 1998. Keep the hole through the bolt the same size as the valve port, to minimize how much energy is lost to expansion of the gas column.

I whipped up one of those for my prototype Fasty- which I still have, by the way- and immediately gained some 30 FPS over a more Lightning-style profile. (I have a Tornado in the prototype.)

I'm not going to say mine's the best ever, though. As I said, there's way too many variables, especially in 'Cocker builds. In some guns the bigger bolt does indeed add more velocity, in others it reduces it. But again, generally speaking, the best bolt is one that stays the same size all the way from the valve to the ball.

Doc.

[Magmoormaster]

It gets really complicated when you consider heavier hammers and lighter springs really help get the pressure down, which in turn helps with efficiency. And not to mention, heavy springing makes the gun shoot like ****. And like Doc said, super high efficient setups tend to be very finicky. I would like to point out, however, that AKA springs are not all that heavy by comparison. They're roughly equivalent of a blue valve spring and green hammer spring from maddmann kits. They're not SLPS springs but they're far from being heavy.

As a quick aside, it was Freeflow that made Tungsten hammers. Shocktech made (and still makes) brass-sleeved steel hammers that are only a few grams lighter than the later WGP hammers.

I also must disagree with the statement about lightning bolts; at least when discussing cockers, lightning bolts are for sure the most efficient bolts ever made. In every comparative text, AKA bolts have the highest chrono readings by at least 10 FPS, 20-30 when compared to the really low-efficiency bolts.

[DavidBoren]

Thank you. Very much so.

That puts a nail in the coffin pursuing custom brass strikers just to pretty much tinker with in an attempt to figure this all out on my own.

I'm glad I asked you first, before investing a bunch of money and energy to learn what is already known. I appreciate you taking the time to have this thread and share your knowledge.

I will have to go change some mainsprings around in a few of my STBB's... I was purposefully running light, but long, springs to provide pretty much constant preload on the striker. It was low tension, but definitely preloaded due to length. I thought that by eliminating the free flying fling at the end, I would be able to achieve a higher level of consistency. I figured that the uncontrolled flight would not be guaranteed the same each time.

The tension/preload is not enough to overcome an AKA valve spring, even degassed... I run light, light springs because I think the stock striker (even the skinny one) weighs A MILLION. And the preload helps me sleep at night, because I also secretly think that the mainspring is too light. Lol.

I have an Alamo City fatty, too... I just literally hate powerfeeds SO MUCH that I don't run my Classic. I might have to get over myself and fire that thing up...

[DocsMachine]

Is there any significant difference in efficiency between using a heavy striker and light springs, versus a light striker and heavy springs?

-Very much so, and an excellent question!

Now, of course there's a million combinations of valve, bolt, striker, etc. out there in a hundred different kinds of marker, so we can't give a definitive answer that covers every single thing. BUT, generally speaking, the light striker with a comparatively heavy spring should be more air efficient.

It has to do with dwell time- how long the valve is open, how long it takes to close. In a typical 'Cocker or blowback marker, the striker hits the valve and pushes it open, letting gas through to the bolt. After a certain period- a few milliseconds- the force of the valve spring and air pressure pushing on the cup seal, push the valve back closed, and push the striker back the other way.

A heavy striker has more inertia, and all else being equal, it takes longer for the valve spring/air pressure to overcome that inertia than it would were the striker lighter. And in the case of a blowback, it takes more air pressure- more energy- to push a heavier striker back to recock.

Now, the trick here, for both kinds of gun but specifically for the 'Cocker, is that if the spring is too long, the spring maintains force on the hammer even when all the way forward, which also increases dwell. So the ideal setup would be to have a relatively lightweight striker, and a spring with sufficient force to open the valve properly, but which does not apply significant pressure on the valve stem at rest.

Clear as mud, right? Simply put: when at rest, the hammer not cocked, but the gun pressurized, when the hammer is resting on the tip of the valve stem, the spring should be putting either very little or no pressure on it. That way, when fired, the spring 'flings' the hammer forward, which strikes and opens the valve, but then, the valve doesn't also have to overcome residual spring pressure in order to close again.

That way, all else being equal, that lets the valve close as quickly as possible, which is a big key towards gas efficiency.

Is it the opposite of strikers and springs when considering the mass/weight of the ram, and the pressure operating the ram? Not with Autocockers, but things like the Impulse or Intimidator (although I don't see much variation in Timmy ram mass).

-Inertia is inertia. The Intimidator may not use springs to drive the "hammer", but the principle is the same. The faster the striker can retract- at least to the point of allowing the valve to close, generally speaking the more efficient the system will be.

I have a hard time believing that they are equally efficient.

-They're not, and by a long shot in some cases. A good example would be to compare a Spyder clone to an old VM-68. The hammer in a VM is something like a pound, the striker in a typical Spyder clone is an ounce or two. The VM wastes a great deal of gas- energy- trying to force the hammer back and close the valve, compared to the far lighter clone striker.

In the 'Cocker world, we used to (and in some cases, still do) try to make heavier and heavier hammers, with I think Shocktech coming out with a Tungsten hammer. We'd smash the valve open with heavy hammers and springs, ironically often to make up for INefficient valves, bolts and barrels.

Modern setups like the Inception guns are not the most efficient possible, as that can tend to be pretty fiddly, taking a lot of fine-tuning for different conditions. But they are fairly well balanced, giving pretty good overall performance over a wider range of conditions.

I also don't like to think that the best compromise is somewhere in the middle... that just seems lazy to me. Surely, when using efficiency as the metric by which they are to be judged, one combination is going to be superior in both theory and practice.

-It is indeed. I once set up a 'Cocker body, using an early custom Bob Long body where they'd bored out the valve chamber (this was in the pre-2000 days) and capped it with brass, to bring it back down to the pre-2K front bolt size. I used pretty much a full AKA setup: Lightning bolt, Tornado valve and AKA springs, all capped off with an early Max Flow running about 165 psi.

With good paint and a good barrel fit (this was also pre-Freak) I got right around 1,600 shots per 68ci/3K fill.

And since we now know the Lightning was not the most efficient bolt, I'd bet with a little more experimenting, I could have gotten it maybe even a little better than that.

The problem with a setup like that, is that it's quite sensitive, especially to paint. The paint-to-barrel fit has to be very good- not too loose, not too tight, and also not too short (like a 5-1/4" freak insert.) That 1.6K above was using quality paint through a 14" .687" Long Shot barrel. Switching to a 12" .689" Autospirit dropped my velocity by something like 40FPS.

That sort of thing is fine for a tinker-freak (raises hand ) but for most players, they just want to pull the gun out of the bag and go play. And especially in these days of all-day-air and 4500 psi tanks, squeezing the last little bit of gas efficiency is not as important as it once was. So most manufacturers set it up a lot closer to the middle of the proverbial road. Maybe not as good as it possibly could be, but also not terrible, and as such, works under a wider range of conditions and setups.

Doc.

[lew]

-Yes, it's 10-32.

-snip-

Thanks for the response and the thread specs. That will help immensely.

Regrettably, I'm very limited with tools, and someone else is doing the printing, so Delrin is out. I'll keep that in mind with the solid fill.

No worries on the parts. I'm set for solenoids and Max Flos. Cheers!

[DavidBoren]

Is there any significant difference in efficiency between using a heavy striker and light springs, versus a light striker and heavy springs?

Is it the opposite of strikers and springs when considering the mass/weight of the ram, and the pressure operating the ram? Not with Autocockers, but things like the Impulse or Intimidator (although I don't see much variation in Timmy ram mass).

I have a hard time believing that they are equally efficient. I also don't like to think that the best compromise is somewhere in the middle... that just seems lazy to me. Surely, when using efficiency as the metric by which they are to be judged, one combination is going to be superior in both theory and practice.

[DocsMachine]

Regarding the Shocker Sport and its associates:

1) Do you know the thread dimensions for the bolt stem to the back of the bolt head?

-Yes, it's 10-32.

2) Regarding the fire piston, what are your thoughts on this: 3D printing the entire piece as one piece with grooves for the o-rings on the ends, thereby omitting the Delrin glide ring and the o-rings underneath?

-An interesting idea. Personally, I think I'd be more inclined to machine it from solid Delrin, but that's my machinist bias. I do know the pushrod puts a fair amount of force on the fire piston, so you'd want to make sure the end is reinforced, maybe thicker/longer and with a nearly-solid infill if you can pull it off.

Try it and let us know.

3) Do you happen to have any spare Shocker parts floating around?

-Nope, sorry. Most everything I had has been slowly sold off over the years. Pretty much the only things I have left is an early Max Flow rebuild kit, which I want to keep as I still have three or four of those, and somewhere I have maybe two or three sets of a Parker solenoid very similar to the Sport units, but have a plastic plug-in assembly. They could be used in a Shocker, I think, but somebody would have to crack off the plug housing and solder on a set of proper leads- and I think you'd be risking breaking the fine coil wires.

I did have a guy ask about the little rubber bumpers that go in the tray and help hold the solenoids in. He saw my new-manufacture Mega-Z bolt bumpers and asked if I could make those too. I whipped him up like three or four, but didn't bother after that. If you need some of those I could make some, but I kind of doubt that's a high-demand item.

Oh, and somewhere I still have a small stack of RIP triggers- just the trigger, I don't have any of the leaf swtiches or the mounting brackets. The triggers would still have to be finish-machined, but I've got 'em.

Doc.

[lew]

Doc,

Regarding the Shocker Sport and its associates:

1) Do you know the thread dimensions for the bolt stem to the back of the bolt head? I don't want to take any of my bolt assemblies apart to measure them if I can avoid doing so.

2) Regarding the fire piston, what are your thoughts on this: 3D printing the entire piece as one piece with grooves for the o-rings on the ends, thereby omitting the Delrin glide ring and the o-rings underneath?

3) Do you happen to have any spare Shocker parts floating around? I've got a miniature fleet of them and am obviously stocking up on spares.

[Brew]

Hey Doc,

Thanks for the update. I figured there would be a longer wait during these crazy times. 👍🏻

Yes I did place an order. I sent payment via PayPal. I was the guy who just missed out to an online order. You gave me the option for a refund but I opted to wait for the fresh shipment from anno. (Shoot me a PM if you like).

Thanks, I'm looking forward to owning a finely crafted piece of your work! 😀

Brew

Sent from my SM-G950U using Tapatalk

[DocsMachine]

How's the anno coming on the L-stocks?

-Oh, don't even ask. I have two batches out for anno, to two different companies (one bulk, one fancy) and both are overdue. To be fair, both companies said there'd be a delay, as they have to sort of 'swing shift' people to conform to virus regs. I didn't think it'd be this long, though... I also have several orders out for product, and my supplies of those are also way behind as well.

Considering what percentage of my income comes from part sales, and on top of sales being generally depressed anyway because nobody's playing, I've run out of four of my five best selling parts because the CNC shop I've been dealing with has been shoving my small orders aside to work on more lucrative orders. That all puts a bit of a dent in the ol' pocketbook.

Fortunately I'm used to subsisting on dollar-store Ramen and expired boxes of mac & cheese-like powder substitute.

I've sent you a PM and an email concerning my order. Any info would be much appreciated.

-Did you actually place an order, or were you one of the ones waiting 'til the parts came in from anno?

I can't blame all the delays on other people. I'm WAY behind on email replies and other work, and I'm backed up in the shop too.

Getting things sorted as quickly as I can.

Doc.

[Brew]

Hey Doc,

How's the anno coming on the L-stocks? I realize Covid is slowing everything down. I understand. I've sent you a PM and an email concerning my order. Any info would be much appreciated.

Thank you sir! 👍🏻

Brew

Sent from my SM-G950U using Tapatalk

[DocsMachine]

Which Carter pumps don't have removable barrels?

-Another one I can't answer with any real certainty. I'm certainly not as familiar as I'd like to be with the Carter lineup.

That said, generally speaking, I thought pretty much all Carters were fixed-barrel, until the advent of the later stock-class Buzzards. Not sure on that, and Carter, being a custom shop that made the guns pretty much to order, and by hand, could easily have made early removable barrel versions, or later fixed-barrel.

That said, of those eBay Carters, with the possible exception of the first and last ones on the list, the rest are pretty much definitely solid-body. The bottom one might have a removable barrel, but I couldn't say for certain. The top one is a less likely possibility, but could be as well.

Sorry I can't be of more help. I'm a big fan of Carter pumps, but I've had very few of them filter through the shop over the years.

Doc.

[DocsMachine]

Which volumizer/low pressure chamber from another gun will work on a Brass Eagle Raptor?

-Good question, and one I can't immediately answer. I have a Raptor around here somewhere, but it's buried deep, and I couldn't even promise I know what room it's in.

One can always be custom-made, of course, but no idea what existing factory or aftermarket ones might fit Never really did much customizing or even repairs of the entry-level blowbacks.

Doc.

[Carp]

Which Carter pumps don't have removable barrels?

[dartamon]

Which volumizer/low pressure chamber from another gun will work on a Brass Eagle Raptor?