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-   -   Ermessub Double Roller Trigger Test (http://www.spearboard.com/showthread.php?t=193094)

Behslayer 04-06-2017 09:11 AM

Re: Ermessub Double Roller Trigger Test
 
Majd, I think it's up to you.. sorry to say, but your the one with the pool, the mech, the know how, and the same gun settings etc.. to determine if there is any adverse effect on accuracy. It's very easy to cut a Square notch using hand tools and calipers. Though I may be biased having done it so many times in the past. Take a Grinder with a Metal cut wheel and cut the Outer sides of the notch carefully and to just above the right depth. Then you can remove the middle fairly easily with the grinder wheel, then flat file, and Buff with Wheel. I'm not sure if you have those "Fix anything" Machine shops in Kuwait like they have in Indonesia. They have a few milling machines, and lathes? As a Spearfieherman, it's great to have a relationship with those guys and a few fillets goes a LONG way in developing their interest in helping you. I figure most of the shafts used in the USA are Square Cut. And certainly almost all of the larger diameter Shafts, so if it's possible to use with this mech it's a big PLUS.

spearq8 04-06-2017 12:42 PM

Re: Ermessub Double Roller Trigger Test
 
Of course I could hack one of my nice shafts to american cut by just using some files ... I have done that before. But you need to test with more than one shaft to make sure it fits many american cut shafts. With euro shafts I made sure it fit about 20 different euro shaft makes. You would need at least 10 different american notch shafts and make sure they all fit.

I actually checked the fit today with euro and the american cut shaft I had ... and was surprised to find that the american cut shaft actually had a better fit on the cradle than the euro shaft. It took a while to figure out, but then I noticed the roller was 6.78mm rather than our designed for 7mm size. Apparently in the polishing process of the roller the 7mm roller became .22mm thinner. I doubt that difference will hurt the euro shaft experience as it shot incredibly well as is, but that was a bummer to see as for my usage a euro fit is more important. I guess an idea would be to cut the rollers from 17-4ph american sized shafts which are around 7.2mm ... after polishing they would be about 7mm and would be a perfect fit for euro ... but maybe then they wouldn't be able to accept an american shaft. That would be much easier than re-designing the cut for the cradle to be .1mm higher. Or maybe just leave it as is and accept a little tolerance for the euro cut and have one trigger work for both shafts.

Behslayer 04-06-2017 12:57 PM

Re: Ermessub Double Roller Trigger Test
 
1 Attachment(s)
Hi Majd,

Maybe you are overthinking this. If you cut a shaft like this and it works. It works.

popgun pete 04-06-2017 04:26 PM

Re: Ermessub Double Roller Trigger Test
 
It would be simpler to buy a US shaft as given the time expended to date the delivery time will be of no consequence. I would expect a square cut tail to hold the roller tooth up in the side slots, unless the shaft tail was tilted slightly downwards in the sear box. With the roller tooth being pushed from the 9 o'clock position there is nothing to squeeze it down, unlike a euro shaft tail where the roller is pushed at between 10 and 11 o'clock, a consequence of which is the flat on the top of the tail is held parallel to the sear box roof.

Behslayer 04-06-2017 05:05 PM

Re: Ermessub Double Roller Trigger Test
 
Pete, you'd be surprised how accurate and quick you can be with a Hand Grinder, a set of files, a Tabletop Sander, a vice, some Calipers and a Buffing Wheel. I get shafts off of CNC machines which I then can improve with those same tools. How long would it take to make a square notch by hand? Realistically to get it perfect. It would take one hour.

The long part of this, is the 100+ shots..

popgun pete 04-06-2017 08:27 PM

Re: Ermessub Double Roller Trigger Test
 
I have made my own shafts at the workbench with a hacksaw and a bunch of files, but it was much easier to buy them when shafts became available in spring stainless steel. The 316 3/8" shafts in my photos were made by me, but I was a lot more enthusiastic in those days, plus 316 bent too easily and even after careful straightening never shot as true as before.

spearq8 04-07-2017 03:08 AM

Re: Ermessub Double Roller Trigger Test
 
Of course I can make a shaft with simple hand files ... as mentioned earlier, I have done it a couple of times successfully. I think you missed the part where I mentioned the fit for the american cut was actually better than for the euro cut with this trigger ... so I have no doubt it would work well. We designed with a 7mm roller in mind and totally didn't expect the roller to lose about .2mm in the polishing process. This still shot really well with a euro cut so I doubt this change in tolerance is a problem as it is easily within the built in tolerances. It just is not a priority for me to test with american cut as I don't use american cut shafts anymore, but maybe in time I can try this out. The problem never was whether it would work or not, it is more to do with being able to get a totally smooth shaft release that ensures absolute shaft stability on exit and thus pin point accuracy. The tighter the roller to cradle fit, the more stable the exit of the shaft ... so I expect it to be at least as accurate with an american cut if not more so.

popgun pete 04-07-2017 03:32 AM

Re: Ermessub Double Roller Trigger Test
 
1 Attachment(s)
What I want to know is will a US shaft release with it only placing a straight pull on the roller tooth through the roller's "equator/diameter" as there is a probability the shaft will hang up.

Here is a diagram that I created for another thread to show what I am talking about.

spearq8 04-07-2017 04:03 AM

Re: Ermessub Double Roller Trigger Test
 
I think for a roller that is connected to the shaft sear (similar to the picture shown in the Red Tide post), you might have a possibility of a hangup which will not prevent the shaft from firing but might destabilize it enough to hurt accuracy as the shaft notch has to ride over the shaft sear. But here you have a roller that just free falls and gets out of the way and would have zero affect on the shaft exiting.

Behslayer 04-07-2017 08:05 AM

Re: Ermessub Double Roller Trigger Test
 
Yes, my concern is more about Smooth Release and it's effect on accuracy as well as degradation over time. From a development point of view this is an important test. A true super mech if it can shoot all shafts.

I was thinking about the issue of losing .2mm in polishing. I think 9/32" is 7.2mm? That could work as a starting point. But what I was really thinking was that there is a few different 'grits' used in polishing and softening, etc. Perhaps the rollers don't need the same amount of smoothing as would other parts which have been cut. The Outer surface of the Roller is drawn and is smooth to begin with. Maybe skip the more aggressive processes in the tumbler and put those in only during the latter steps. For example if I was going to soften and police a cut part, I might put it into a tumbler using an aggressive grit for a certain amount of time and then move into a tumbler with a less aggressive grit and then finally into a tumbler for polishing. I've dealt with similar issues with Slip Tips which are a very precise fit. For smoothing Shark fins etc, buffing out non critical fit parts I'll use an aggressive grit (removes scratches) to begin with and then polish. But if I were to use this same grit with a Slip Tip Base I might remove too much and alter the fit, so in this case I'll use a much less aggressive grit to start i.e. (removes very fine scratches) and then go straight to polish buffing.

Nix 04-07-2017 08:43 AM

Re: Ermessub Double Roller Trigger Test
 
Great!!! Now I want to buy more stuff to play with.

popgun pete 04-07-2017 05:18 PM

Re: Ermessub Double Roller Trigger Test
 
1 Attachment(s)
Quote:

Originally Posted by spearq8 (Post 2137662)
I think for a roller that is connected to the shaft sear (similar to the picture shown in the Red Tide post), you might have a possibility of a hangup which will not prevent the shaft from firing but might destabilize it enough to hurt accuracy as the shaft notch has to ride over the shaft sear. But here you have a roller that just free falls and gets out of the way and would have zero affect on the shaft exiting.

The roller tooth will not drop down if the axle end is driven into the top of this slot as it would then have to back-up over the bump created by the contra-curving of the side slot. With a eurogun shaft tail there is a downward force component that can push the roller down as it pushes higher up on the roller tooth. For a US shaft tail to work the lower trailing edge of the spear tail notch would have to push down on the roller which would be a very narrow point of contact.

popgun pete 04-07-2017 08:06 PM

Re: Ermessub Double Roller Trigger Test
 
It would be good see a lateral close-up of the roller tooth moving, as in observing its axle ends moving downwards in the side slots, as the gun actually shoots. Then we could see the extent of the vertical displacement in the side slots and whether when loaded and cocked the axle end is sitting right up at the top of the slot. Over time the floating roller tooth's axle ends should leave some wear marks on the side slot edges as the roller tooth is wiped downwards by the departing shaft tail.

This trigger mechanism's ability to have low pull at high loads is due to the spear pull force being transferred by two axles, one the sear pivot pin axle and the other being the roller tooth axle. That means the side walls are loaded up at four positions, not counting the two positions that support the trigger pivot pin axle.

Dr.P 04-08-2017 09:41 AM

Re: Ermessub Double Roller Trigger Test
 
So... how do we buy some??

kavachi 04-11-2017 09:54 PM

Re: Ermessub Double Roller Trigger Test
 
GREAT work Majd!!! hope you get to try that smoooth crisp trigger pull with some big pelagic action soon!
Harry, PMd you but not sure if went thru. PLEASE put one aside for me to send with handle :up:
Kavachi


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