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Old 10-11-2019, 01:48 PM   #46
musubi
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Re: My Invert Roller

It looks like I'll be building another invert roller, but for bluewater hunting. I bought one of Makoa's cuttled 120 barrels and I'm planning to do a similar setup, but with 4 sets of bands.

I've been trying to just evaluate every part of this setup to make sure it'll be stable and possible. I think one of the unknowns for me is how the bands will lay. I have a couple ideas of how to address.

Anyway, it got me thinking what kind of energy and speed my blue water gun shoots at (Abellan 130), so I can build this gun to shoot similarly. It came with 3 x 14 mm bands at 337% stretch. After doing the math, it shoots the 8.5 mm Hunt shaft at 144 ft/sec.

I tried to determine an estimate speed of a 7.5 mm shaft for a 120 invert, using 4 sets of 14 mm bands, similar to my current reef setup. Speed came to 156 ft/sec (about).

I'm trying to be mindful and tell myself that greater the speed isn't always better. I don't know enough to know where shaft whip will become an issue or when an effective terminal velocity will be reached. Plus this 7.5 mm RA shaft is not the same as the 8.5 mm Hunt. I think the best I can do is build it and test shoot it. Go from there.

My setup with the new invert is planned to be:
- MVD Handle
- MVD Ram Muzzle
- 7.5 mm RA shaft with the drop barb
- 120 cm carbon barrel
- 4 sets of 14 mm bands (unsure of the % stretch yet)
- 2x Harken 16mm Forkhead Block

So, a request for thought, for anyone following, with the Rob Allen drop barb shaft, it'll be a notched style shaft, with the line attachment at the very rear of the shaft. I typically use 400 lb mono, but this won't fit in the MVD mech. What will fit easily is my 1.7 mm jacketed Aussie Line. Anyone use this type of line for their shooting line? I'm guessing it tends to tangle easier than mono.

So my next thought is I could drill a hole in the shaft behind the last notch, but before the rear shaft taper. I'm thinking this placement wouldn't affect the stiffness of the shaft on the shot much or compromise the shaft strength should I have a fish on.

Or I could make a small loop with the aussie line just so that it fits in the mech and then attach the mono to that. Anyways, things I'm thinking about.
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Old 10-11-2019, 02:25 PM   #47
Mana'squal
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Re: My Invert Roller

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Originally Posted by musubi View Post
I typically use 400 lb mono, but this won't fit in the MVD mech. What will fit easily is my 1.7 mm jacketed Aussie Line. Anyone use this type of line for their shooting line? I'm guessing it tends to tangle easier than mono.
I use their stiff dynema which is what i think you're referring to, love the stuff. Does tangle a bit easier but i like it alot more than mono.
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Old 10-11-2019, 06:24 PM   #48
musubi
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Re: My Invert Roller

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I use their stiff dynema which is what i think you're referring to, love the stuff. Does tangle a bit easier but i like it alot more than mono.
Thanks! I'm leaning towards running with the dyneema line I have and see how that goes shooting with it. I prefer not to drill into my shaft just yet if I can avoid it.
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Old 11-25-2019, 03:23 PM   #49
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Re: My Invert Roller

I built another invert roller and I thought I'd update my thread (just so it's all in one place for me). The following are the specs:

- 120 cm cuttled barrel, carbon, gloss finish (bought from Makoa)
- MVD Handle
- MVD RAM muzzle
- 7 mm RA threaded shaft, wire finned, euro
- Mori Slip Tip
- 4 pairs of 14 mm bands, 12 inches from knot to knot, 1 inch of pre-stretch
- 2 Harken 16 mm forkhead blocks

It's taken me some to build this gun and I've tried to calculate and anticipate as much as I could, which overall has helped me.

The following are some pictures of the gun (I've also added in-water photos):





















The barrel I stuffed with a calculated amount of cut up clothes to weigh the gun down a bit. This is intended to be my bluewater invert setup, so no reel. The muzzle was weighed down a bit more with some shot pellets. Without the shaft, the gun floats evenly on the surface. With the shaft, it feels well balanced with the 7 mm shaft.

Originally I had intended on using the RA 7.5 mm drop barb shaft, but there were a couple issues. One being that I needed a line loop on the shaft, which required me to drill and pin the loop in. I couldn't drill the holes consistently. Long story. Second, loading the invert gun is a little more cumbersome than a classic band setup, so when you add the additional setup of the drop barb, it was rather time consuming to set things up all over again after the shot. In the end, I junked the shaft (since I destroyed it anyways) and moved on.

I test shot the gun with two different shafts this past Saturday. The first was the Hunt, 8.5 mm, 155 cm, threaded, mori slip tip. The second was the Rob Allen, 7 mm, 147 cm, threaded, mori slip tip. Both shot very well, and hit center at about 12 feet from the muzzle. Beyond this, the Hunt shaft started to drop, since that shaft is so heavy. It looked and felt like the Hunt shaft carried more energy at the end of the shot, pulling the bungee line a bit more than with the RA shaft. I may explore an in-between shaft diameter.

The water was murky and I wanted to test further distances, but the water conditions changed and visibility went down to like 5 feet. Called it day after.

Speaking to the gun, you'll see in the photos above that I added a bent SS pin to the muzzle. It's for line wrapping purposes, but something I needed to arrange my line management at the guns' side. The shooting line sits on top of the cuttled portion, away from the bands. When I shot my reef invert gun with the lines beneath the gun, with the bands, everything would tangle like 50% of the time. I lost one fish because of it (insufficient penetration) and never went back to that line wrapping orientation. Oddly that's what MVD recommends for their guns.

I also added that SS line wrap. I know it's not pretty, but it's functional and sturdy and just fits where I needed it to.

The gun's first two pairs (4 bands) is fixed and has 1 inch of band pre-stretch. One of the pairs goes through the hole in the MVD handle, while the other pair goes through the trigger guard. So, yes, I need to pull back 2 pairs at the beginning. This amounts to 90 lbs at full stretch and pulling that dyneema isn't the most comfy, but doable. Loading the last two pairs is easy and hooks right on to the handle hook at the bottom.

The 4 pairs of rubbers rub against each other and against the barrel, but I can't see this as making any huge difference in the power output. They could lie nice and even when loaded, but it's too time consuming for me to do that every time and I'm thinking it wouldn't make much of a difference in performance anyway.

The recoil is hardly felt with the 7 mm shaft. It's little more with the 8.5 mm, but nothing near a classic band setup. I was concerned about the 7 mm being too flimsy for the amount of power I'm putting into this gun, but so far it appears to blast on through the target straight. I would need a setup like maj's foam boards to confirm. Ultimately, I'd like to try a 7.5 mm or an 8 mm shaft. Anyone know a good straight shaft brand for a 7.5 mm, threaded, shark fin, euro cut?

I suspect that because the force on the shaft is applied more as a push vs a snap with the classic bands it helps with the shaft deflection. Terminal velocity is a different issue though and will probably need to checkout penetration results later.

In that last picture, it just shows the line release I fabricated to hold an additional line wrap.
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Old 11-25-2019, 04:37 PM   #50
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Re: My Invert Roller

Any thrumming from the bands when you turn the gun in the water, cocked to shoot?
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Old 11-25-2019, 04:47 PM   #51
musubi
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Re: My Invert Roller

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Originally Posted by popgun pete View Post
Any thrumming from the bands when you turn the gun in the water, cocked to shoot?
That's a good question. While I didn't notice any, I didn't turn my gun much in the water. I'll definitely pay attention to that next time I take it out.

Thinking of my reef invert, I don't have that issue there, say if I'm tracking a fish.

I'll update on this later.
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Old 11-25-2019, 08:43 PM   #52
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Re: My Invert Roller

I love seeing all this experimentation. I think it's important to keep in mind what is a baseline standard for a simple 2 band Classic set up so that you can weigh performance gains vs any added complexity. Rollers need to outperform classic guns in order to be worth the added complexity. Sight picture is great, lack of recoil isn't really an issue compared to a 2 band wooden gun with a Reel on it, there's not a lot of Recoil.

Here's some video of a 120cm (Band stretch) 2 band classic gun for comparison.

https://www.youtube.com/watch?v=a4K-j0WQ6lw

I figure 16' from the tip is really at the end of the range I'd pull the trigger on a Mu or Uku. This gun has more range than that. You can see it's penetrating 5" of foam at 16'. I think we tested out to 22' for accuracy.

The question becomes. What are the performance differences between that gun as it is set up vs. in a Classic 2 band configuration? Is the Juice worth da squeeze?
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Old 11-25-2019, 09:28 PM   #53
musubi
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Re: My Invert Roller

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Originally Posted by Behslayer View Post
I love seeing all this experimentation. I think it's important to keep in mind what is a baseline standard for a simple 2 band Classic set up so that you can weigh performance gains vs any added complexity. Rollers need to outperform classic guns in order to be worth the added complexity. Sight picture is great, lack of recoil isn't really an issue compared to a 2 band wooden gun with a Reel on it, there's not a lot of Recoil.

Here's some video of a 120cm (Band stretch) 2 band classic gun for comparison.

https://www.youtube.com/watch?v=a4K-j0WQ6lw

I figure 16' from the tip is really at the end of the range I'd pull the trigger on a Mu or Uku. This gun has more range than that. You can see it's penetrating 5" of foam at 16'. I think we tested out to 22' for accuracy.

The question becomes. What are the performance differences between that gun as it is set up vs. in a Classic 2 band configuration? Is the Juice worth da squeeze?
In my opinion, if you can get a classic band setup to shoot consistently and accurately and with enough power for the game you're after, the classic band setup would be without question the go-to setup. It's simple and easy to load.

Of course your video proves that and I can hear everyone saying that multiple classic setups exist, so why anything else? For me, I suddenly got into invert rollers because of how accurate they are for me. I don't feel like I have enough experience with a variety of guns to make any judgement in the gun world yet, but from my past guns, it's been hard for me to get the accuracy I've been looking for.

The pipe guns I've tested or used in the past have never shot well for me. Maybe over powered, but my bands were 2 x 14 mm @ 320%. I've tried different handles and custom grips. Still did not shoot well. (aimrites included)

For reef, the gun I stuck with the longest was my wooden 110 cm (KAP, enclosed track). Fairly accurate, but my invert out performs it in consistency.

The things I like about my invert reef has been clean sight picture and being able to shoot at weird angles without much support at the handle. Normally with my classic band guns a good straight grip was needed for an accurate shot and to control recoil. I don't need it with the invert. Not saying you can't do this with your guns Jon. Again, this is just my limited experience.

Really though I'm more stuck on this track of inverts because I found one thing that works well and I'm just exploring more about it.
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Old 11-26-2019, 12:42 AM   #54
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Re: My Invert Roller

I am just curious how the trigger doing with all of that bands ?does it shoot smoothly all the time or you have to pull hard in order to release the spear ?I think this ( Trigger Predator) if it smooth same like ermesub DR triggers .

Last edited by doyenofcastle; 11-26-2019 at 12:54 AM.
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Old 11-26-2019, 12:13 PM   #55
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Re: My Invert Roller

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I am just curious how the trigger doing with all of that bands ?does it shoot smoothly all the time or you have to pull hard in order to release the spear ?I think this ( Trigger Predator) if it smooth same like ermesub DR triggers .
The trigger mech and the pull is still smooth and functioning normally. The bands may look powerful with 8 of them there, but the pulleys reduce their force by half.

The total estimated force on the trigger mech is 180 lbs, which is around what a 2 band classic setup would exert on a mech, so it's nothing out of the ordinary or extreme.
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Old 11-26-2019, 02:50 PM   #56
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Re: My Invert Roller

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Originally Posted by musubi View Post
The trigger mech and the pull is still smooth and functioning normally. The bands may look powerful with 8 of them there, but the pulleys reduce their force by half.

The total estimated force on the trigger mech is 180 lbs, which is around what a 2 band classic setup would exert on a mech, so it's nothing out of the ordinary or extreme.
Just to give a ballpark figure Rob Allen tests his mech at 120 kg or 265 pounds of pull using a pressure loading device to cycle the firing and cocking of a speargun assembly. At a 100 pound draw a four band gun can have 400 pounds (and more) on it to propel a decent sized shaft to ensure "death and destruction".
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Old 11-27-2019, 01:15 AM   #57
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Re: My Invert Roller

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Originally Posted by musubi View Post
The trigger mech and the pull is still smooth and functioning normally. The bands may look powerful with 8 of them there, but the pulleys reduce their force by half.

The total estimated force on the trigger mech is 180 lbs, which is around what a 2 band classic setup would exert on a mech, so it's nothing out of the ordinary or extreme.

Unfortunately that trigger will gall (scratch) and it will cause an inconsistent trigger pull which you might not notice ... but it will hurt your accuracy as the break point of the trigger will be different and inconsistent. I never realized this problem until I started accuracy testing in the pool. Shot groups would actually "walk" or move on the target depending on where the trigger broke. This is the problem when you have 2 stainless steel sears rubbing against each other at high load. This can be alleviated if less pressure is applied, or if you use additional levers to reduce tension on the sears ... but it eventually will happen. The solution is to use a roller or to use a softer material on one of the parts, usually the trigger sear as it does not interact with the shaft notch. This cold welding or galling problem is a well know phenomenon with stainless steel.

I discovered this problem about 5 years ago with a Pathos D2 trigger, but later realized that it was not only a Pathos problem but rather a general problem with friction triggers. Proof of this problem has finally been shown in the lab by Rob Allen and I think he has done a great service for putting that out on youtube. You can see it here

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Old 12-02-2019, 02:23 PM   #58
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Re: My Invert Roller

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Any thrumming from the bands when you turn the gun in the water, cocked to shoot?
Reporting back, no thrumming with the bands loaded. I tried moving the gun faster through the water with both hands and still no thrumming.
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Old 12-02-2019, 03:28 PM   #59
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Re: My Invert Roller

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Reporting back, no thrumming with the bands loaded. I tried moving the gun faster through the water with both hands and still no thrumming.
Good, one of the aims of cable guns, which is what an inverted rollergun is, was to eliminate the bands sitting up off the top deck and vibrating and causing a lot of drag when cocked to shoot as you swung the gun through the water. It is also the reason for cord limited stretch "shoelace" bands on the top deck of rollerguns and improves the sight picture. The ultimate cable gun, if we ever get to see it, will be the "Dreamair" compressed air powered Arbalete.
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Old 12-17-2019, 03:11 PM   #60
musubi
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Re: My Invert Roller

I ordered and received a 7.5 mm Addiction Spear from Dean Koutras. It's threaded 6mm, 148 cm in length. I've never ordered a custom spear before, but I was very pleased with the quality. I'm usually picky on straightness of my shafts and this shaft is very straight. I have an arrow spinner I test my shafts on.

I also ordered the Ermes Invert Pulleys for my 6 banded reef gun. Honestly, I'm not sure if I'll swap them with my Harkens yet. The tiny pulley bolts got me questioning their strength with the band force I got on them. I'm sure they're proven, but my Harkens are built much stronger. I'll have to look into the diameter and shear strength later.





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