Looking for a good machinist!

deadlydayne · March 25th, 2011, 07:02

alright so time for my update again, sorry no pics. but as for main design of the part, i havent really found any room to thicken any tabs except for the top tab that sits under the rail, mine snapped the top tab off as soon as i shot the gun the first time. so stock the upper tab sits at a total thickness of .190" and i found enough room to make it .260" with a little room for various gun differences. Im still looking for other areas to improve, drawings are almost done tho, so next week should start programming for toolpaths and hopefully round wednesday or so ill be making prototypes.

Ross · March 25th, 2011, 09:28

Awesome. Keep pluggin away!

Dire_Wolf · March 25th, 2011, 10:40

Quote:

Originally Posted by deadlydayne

Dire you dirty bastard, tryin to scam free parts already :-) hahahaha that was another of my thoughts. I have the CO2 Gen 3 Scar so it was always open bolt. i dont think i myself will be getting the steel bolt that may be another one of my fun projects is make a cnc versions

^_^ of course!!

seriously though, best way to test something is to put in the hands of users that are known to break bits... i know of a guy here in calgary who's got a broken part 27, and he didn't even break a hinge plate first...

and not to be contrary or anything.... but are you sure you have an open bolt scar? the CO2 version changed the valve design from 3 post to 4 post, but the system stayed the same... still had a brass tube... if there's a brass tube inside the ejection port when you lock the bolt carrier back, it's closed bolt...

Quote:

Originally Posted by deadlydayne

alright so time for my update again, sorry no pics. but as for main design of the part, i havent really found any room to thicken any tabs except for the top tab that sits under the rail, mine snapped the top tab off as soon as i shot the gun the first time. so stock the upper tab sits at a total thickness of .190" and i found enough room to make it .260" with a little room for various gun differences. Im still looking for other areas to improve, drawings are almost done tho, so next week should start programming for toolpaths and hopefully round wednesday or so ill be making prototypes.

I don't really think you need to reinforce any dimensions on the part, just the material is really all that's needed.

deadlydayne · March 25th, 2011, 10:47

true, may be closed ill have to look again when im in the shop, either way i run Co2 i hate green gas, i havent busted up my hinge plate either just 27, and the top ear that goes under the rail inside the gun it snapped off half the threaded ear.

speakin of open bolt kits you guys know where i could pick one up?

Ross · March 25th, 2011, 12:16

Quote:

Originally Posted by Dire_Wolf

^_^ of course!!

i know of a guy here in calgary who's got a broken part 27, and he didn't even break a hinge plate first...

well now you know 3 people. Because that's what happened to me too. I still haven't broken a hinge plate.

Eeyore · March 25th, 2011, 12:26

Deadpools part 27 broke twice and he has never ha a problem with the hindge plate either.

Dire_Wolf · March 25th, 2011, 13:17

weird... I've broken one hinge plate... when i used this friend of mine's lower receiver instead of mine to fix a trigger pack issue, but it didn't have the pvc mod, so hinge plate bit it... and my current plate is cracked due to some sideways force on the stock, but hasn't broken...

I have a gen2 though, according to the serial number... maybe they got cheaper materials for later gen? or maybe there's a run of serial numbers that has a bad batch of part 27?

ThunderCactus · March 25th, 2011, 14:55

So does the bolt carrier itself strike this plate when it blows back or what? Why is it breaking in the first place?

Dire_Wolf · March 25th, 2011, 15:04

no, the bolt carrier hits the hinge plate, and it translates all of the force to part 27 when it moves backwards. with the pvc block that i have, it still transfers some force there, but since it goes to the lower receiver, it also transfers some force to the hopup body and from there, the main frame...

it's breaking because it's die cast, and a different piece. If they'd included the hinge and loops on the main body assembly, made with the same material, we wouldn't have this issue...

deadlydayne · March 25th, 2011, 18:58

nono, bolt carrier isnt even allowed to roll back that far, its your recoil spring thats what is hitting your hinge plate. Part 27 is bolted to the gun but in areas of which your bolt carrier cant reach, not vertically or horizontally the path it travels and the allowable limit make it impossible. the recoil spring is what keeps your bolt from going that far. what i see happening is this, the recoil spring is the only thing other than stock hinge making contact with part 27. when assembling the rifle, you put in your bolt assembly and slide in the recoil spring. now the recoil spring has a rectangular block bolted on the end, this also doesnt allow the recoil spring to fit all the way into the main recievers, so it sits inside part 27 and agains stock hinge. the reason stock hinges break is that well thats where recoil comes from, bolt flies back reaches end of travel and smacks the recoil spring, which in turn slams into stock hinge, like everything theres play (room for things to move) so my assumption is that the recoil spring while being violently slammed against hinge is also moving vertically and horizontally every shot also hitting part 27, not to mention the stress put on that shitty pot metal by holding both receivers and stock together. all in all id say that part takes more stress and abuse than almost any other in the scar

also i think i read somewhere that gen 3's and half of the gen 2's stock hinges where made with better material to fix the stock hinge break. and as im staring at it i see no signs of damage, wear, or any kind of abuse

Dire_Wolf · March 25th, 2011, 22:40

I don't think the spring moves at all, I think the force just gets transmitted to it by the hinge plate... If the hinge plate got reinforced from late gen 2, then it may be stronger than the metal, resulting in part 27 breakage...

Same kinda issue that caused my triggerpack issues... Reinforced hammer wore down trigger... If everything was same material, no issues...

Ross · March 25th, 2011, 23:17

Well to be overly specific; the spring itself compresses and expands. The rod inside the spring doesn't move that much. The recoil power isn't really slammed into the hinge plate, more like transferred. After a lot of use, the spring can become weak. When this happens the grey bolt actually does manage to slam the bottom of the T section of the recoil rod. When this starts happening, the hinge plate is much more likely to break. My spring was getting a little weak so I did a little mod involving washers to increase the spring's resistance.

MadMax · March 25th, 2011, 23:31

After looking at those pictures, I'd say that there is a stress concentration at the sharp corner on the tabs which isn't helping. One tab shows a curved fracture ending at opposite corners of the tabs while the other tab shows a clean break across the cross section of the tab. I'd say that the first tab failed due to fatigue which put all the load on the opposing tab which failed in a fairly fast fracture mode (straight clean break).

Tankdude is right on the money recommending a change to mild steel over 7xxx series aluminum. High grade forged aluminum billet has good strength in comparison to mild steels (roughly similar) but it does not have the fatigue resistance. Steels generally have much better fatigue performance to aluminum alloys and weight doesn't appear to be a factor with this part.

I'm seeing a lot of operations in making this part. A lot of thin sections that are difficult to fixture to for later operations. I get the feeling that this would be a good application for sand cast steel. Fill in the cross drilled holes and get the part sand cast. Finish drill the holes and tap them.

deadlydayne · March 25th, 2011, 23:35

ok what i mean was on the recoil spring, the spring obviously sits on a rod, then at the end of the spring towards the back of the gun is a larger dia. piece of alum., so the spring doesnt have "play". at the end of the larger dia. there is a rectangular block of aluminum, that block is what cant go into the receivers but is in between part 27 and is what sits on the hinge. now the larger dia. rod that sits at the end of the spring is where your recoil comes from, your bolt slams back and hits this larger dia. transferring the force to the rectangular block which in turn hits your hinge plate. if i had pics of it, itd be alot easier to describe :-)

@MadMax,
I will not cast anything. wether it be steel aluminum, carbide, tool steel anything. i wont touch it. Cast is worthless, just a quick and cheap way of building something, that inevitably will fail much faster than billet. it looks shitty, and well quite honestly is shitty. i absolutely hate it. It may work for some applications but not for what this. theres going to be about 5 ops required to make it. but making a fixture is easy, if it goes to mass production, i may not be able to fixture a bunch of parts for the last 3 ops but nobody said i couldnt run it on 8 vices :-) and again, as i said many posts ago, im not going to do it in steel unless this aluminum fails. I have seen this 6061 stand up to many things and still walk away. Im fairly confident it will be enough. You have to remember this is for airsoft. It does take abuse and quite a bit, but its not a real steel nor will it ever be. Its not like you are actually "Firing" a bullet off in chamber causing massive recoil such as the SCAR H (.308) if that were the case then without a doubt id make it steel, but alas we are in airsoft using gas much less power much less kick, much less force. Steel is unnecessary as of right now

Lord Jebus · March 26th, 2011, 00:37

Quote:

Originally Posted by deadlydayne

I will not cast anything. wether it be steel aluminum, carbide, tool steel anything. i wont touch it. Cast is worthless, just a quick and cheap way of building something, that inevitably will fail much faster than billet.

What do you think they do when they make engine blocks for you car or truck?
Cast! Cast is not worthless... the materials you use to cast may be... but the process is tried and true!

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March 25th, 2011, 09:28	#62
Ross Trader rating Join Date: Nov 2009 Location: Winnipeg	Awesome. Keep pluggin away! __________________

March 25th, 2011, 10:47	#64
deadlydayne Trader rating Join Date: Mar 2011 Location: Michigan, USA	true, may be closed ill have to look again when im in the shop, either way i run Co2 i hate green gas, i havent busted up my hinge plate either just 27, and the top ear that goes under the rail inside the gun it snapped off half the threaded ear. speakin of open bolt kits you guys know where i could pick one up? Last edited by deadlydayne; March 25th, 2011 at 11:18..

March 25th, 2011, 13:17	#67
Dire_Wolf Trader rating Join Date: Nov 2003 Location: Calgary, Alberta	weird... I've broken one hinge plate... when i used this friend of mine's lower receiver instead of mine to fix a trigger pack issue, but it didn't have the pvc mod, so hinge plate bit it... and my current plate is cracked due to some sideways force on the stock, but hasn't broken... I have a gen2 though, according to the serial number... maybe they got cheaper materials for later gen? or maybe there's a run of serial numbers that has a bad batch of part 27? __________________ Current Gear: TM G36C/SL-9, WE M14, WE PDW, KWA USP, KJW USP Tactical Future Gear: TM PSG1, M700, ARES DSR-1 v2

March 25th, 2011, 07:02	#61
deadlydayne Trader rating Join Date: Mar 2011 Location: Michigan, USA	alright so time for my update again, sorry no pics. but as for main design of the part, i havent really found any room to thicken any tabs except for the top tab that sits under the rail, mine snapped the top tab off as soon as i shot the gun the first time. so stock the upper tab sits at a total thickness of .190" and i found enough room to make it .260" with a little room for various gun differences. Im still looking for other areas to improve, drawings are almost done tho, so next week should start programming for toolpaths and hopefully round wednesday or so ill be making prototypes.

March 25th, 2011, 14:55	#68
ThunderCactus Not Eye Safe, Pretty Boy Maximus on the field take his picture! Trader rating Join Date: Feb 2007	So does the bolt carrier itself strike this plate when it blows back or what? Why is it breaking in the first place?

March 25th, 2011, 15:04	#69
Dire_Wolf Trader rating Join Date: Nov 2003 Location: Calgary, Alberta	no, the bolt carrier hits the hinge plate, and it translates all of the force to part 27 when it moves backwards. with the pvc block that i have, it still transfers some force there, but since it goes to the lower receiver, it also transfers some force to the hopup body and from there, the main frame... it's breaking because it's die cast, and a different piece. If they'd included the hinge and loops on the main body assembly, made with the same material, we wouldn't have this issue... __________________ Current Gear: TM G36C/SL-9, WE M14, WE PDW, KWA USP, KJW USP Tactical Future Gear: TM PSG1, M700, ARES DSR-1 v2

March 25th, 2011, 18:58	#70
deadlydayne Trader rating Join Date: Mar 2011 Location: Michigan, USA	nono, bolt carrier isnt even allowed to roll back that far, its your recoil spring thats what is hitting your hinge plate. Part 27 is bolted to the gun but in areas of which your bolt carrier cant reach, not vertically or horizontally the path it travels and the allowable limit make it impossible. the recoil spring is what keeps your bolt from going that far. what i see happening is this, the recoil spring is the only thing other than stock hinge making contact with part 27. when assembling the rifle, you put in your bolt assembly and slide in the recoil spring. now the recoil spring has a rectangular block bolted on the end, this also doesnt allow the recoil spring to fit all the way into the main recievers, so it sits inside part 27 and agains stock hinge. the reason stock hinges break is that well thats where recoil comes from, bolt flies back reaches end of travel and smacks the recoil spring, which in turn slams into stock hinge, like everything theres play (room for things to move) so my assumption is that the recoil spring while being violently slammed against hinge is also moving vertically and horizontally every shot also hitting part 27, not to mention the stress put on that shitty pot metal by holding both receivers and stock together. all in all id say that part takes more stress and abuse than almost any other in the scar also i think i read somewhere that gen 3's and half of the gen 2's stock hinges where made with better material to fix the stock hinge break. and as im staring at it i see no signs of damage, wear, or any kind of abuse

March 25th, 2011, 22:40	#71
Dire_Wolf Trader rating Join Date: Nov 2003 Location: Calgary, Alberta	I don't think the spring moves at all, I think the force just gets transmitted to it by the hinge plate... If the hinge plate got reinforced from late gen 2, then it may be stronger than the metal, resulting in part 27 breakage... Same kinda issue that caused my triggerpack issues... Reinforced hammer wore down trigger... If everything was same material, no issues... __________________ Current Gear: TM G36C/SL-9, WE M14, WE PDW, KWA USP, KJW USP Tactical Future Gear: TM PSG1, M700, ARES DSR-1 v2

March 25th, 2011, 23:17	#72
Ross Trader rating Join Date: Nov 2009 Location: Winnipeg	Well to be overly specific; the spring itself compresses and expands. The rod inside the spring doesn't move that much. The recoil power isn't really slammed into the hinge plate, more like transferred. After a lot of use, the spring can become weak. When this happens the grey bolt actually does manage to slam the bottom of the T section of the recoil rod. When this starts happening, the hinge plate is much more likely to break. My spring was getting a little weak so I did a little mod involving washers to increase the spring's resistance. __________________

March 25th, 2011, 23:31	#73
MadMax Delierious Designer of Dastardly Detonations Trader rating Join Date: Dec 2001 Location: in the dark recesses of some metal chip filled machine shop	After looking at those pictures, I'd say that there is a stress concentration at the sharp corner on the tabs which isn't helping. One tab shows a curved fracture ending at opposite corners of the tabs while the other tab shows a clean break across the cross section of the tab. I'd say that the first tab failed due to fatigue which put all the load on the opposing tab which failed in a fairly fast fracture mode (straight clean break). Tankdude is right on the money recommending a change to mild steel over 7xxx series aluminum. High grade forged aluminum billet has good strength in comparison to mild steels (roughly similar) but it does not have the fatigue resistance. Steels generally have much better fatigue performance to aluminum alloys and weight doesn't appear to be a factor with this part. I'm seeing a lot of operations in making this part. A lot of thin sections that are difficult to fixture to for later operations. I get the feeling that this would be a good application for sand cast steel. Fill in the cross drilled holes and get the part sand cast. Finish drill the holes and tap them. __________________ Want nearly free GBB gas?

March 25th, 2011, 23:35	#74
deadlydayne Trader rating Join Date: Mar 2011 Location: Michigan, USA	ok what i mean was on the recoil spring, the spring obviously sits on a rod, then at the end of the spring towards the back of the gun is a larger dia. piece of alum., so the spring doesnt have "play". at the end of the larger dia. there is a rectangular block of aluminum, that block is what cant go into the receivers but is in between part 27 and is what sits on the hinge. now the larger dia. rod that sits at the end of the spring is where your recoil comes from, your bolt slams back and hits this larger dia. transferring the force to the rectangular block which in turn hits your hinge plate. if i had pics of it, itd be alot easier to describe :-) @MadMax, I will not cast anything. wether it be steel aluminum, carbide, tool steel anything. i wont touch it. Cast is worthless, just a quick and cheap way of building something, that inevitably will fail much faster than billet. it looks shitty, and well quite honestly is shitty. i absolutely hate it. It may work for some applications but not for what this. theres going to be about 5 ops required to make it. but making a fixture is easy, if it goes to mass production, i may not be able to fixture a bunch of parts for the last 3 ops but nobody said i couldnt run it on 8 vices :-) and again, as i said many posts ago, im not going to do it in steel unless this aluminum fails. I have seen this 6061 stand up to many things and still walk away. Im fairly confident it will be enough. You have to remember this is for airsoft. It does take abuse and quite a bit, but its not a real steel nor will it ever be. Its not like you are actually "Firing" a bullet off in chamber causing massive recoil such as the SCAR H (.308) if that were the case then without a doubt id make it steel, but alas we are in airsoft using gas much less power much less kick, much less force. Steel is unnecessary as of right now Last edited by deadlydayne; March 25th, 2011 at 23:47..

Looking for a good machinist!

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