The Aliens Legacy
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Recoil mod
http://forum.alienslegacy.com/viewtopic.php?f=4&t=14924		 Page 1 of 1
Author:  Rob [ Fri Oct 31, 2014 7:23 pm ]
Post subject:  Recoil mod
I have a Matrix PR and while pondering about how to add haptic feedback to it I came up with the idea to hack the airsoft internals to add some recoil kick to it.

I'm not using it for airsoft and have already removed the inner barrel and hop-up, so I'm not concerned with keeping the airsoft functionality intact.

There are mods and other weapons that do have recoil systems, but those are all in addition to the main airsoft functionality. What I want to do is basically convert the airsoft gearbox to a recoil machine.

Before I start hacking away I figured I should ask more experienced airsofters if you have any suggestions?

My basic idea is to add weight to the piston, remove the cylinder head and simply have the (now heavy) piston smack into something to create kick instead of pushing air.

Any thoughts on refining this? Should I upgrade any gearbox parts? Would a high torque motor be better than a high speed one?
Author:  Sidewinder [ Sun Nov 02, 2014 6:14 pm ]
Post subject: 
Adding enough weight to get a significant (felt) recoil effect to a normal piston is hard as there is little space other than the piston face to do so. Ideally you'd want to make an entirely new piston out of a much heavier material (eg. steel) this would probably be expensive though.

You could replace the piston head with a shaped block of lead. Also it's possible to drill out the spring guide and the back of the gearbox and then have a rod fixed to the front of the piston running all the way out the back of the GB with a second weight secured to that. Need to be aware of it interfering with upper/lower rec'er assembly etc though.

This all will probably stress the gears etc more so unless you want to spend a lot on high quality gears etc (not worth it IMO) i'd just get a less powerful main spring or shorten the one you have (so it's still under V slight compression at rest). Also put some sort of cushioning on the 'piston' face and cylinder head face to soften the impact, otherwise you might crack the gearbox.

Avoid a high speed setup as the weighted piston will prob be too slow on return and get caught by the sector gear. Use the standard GB/motor initially.

SAS
Author:  robedavies [ Sun Nov 02, 2014 8:00 pm ]
Post subject: 
Hi

Have you seen this?

https://www.youtube.com/watch?v=ihk3BHXu4S4

But I only recommend it if you are sure you are not going to Airsoft with the PR?
Author:  demoncase [ Sun Nov 02, 2014 10:45 pm ]
Post subject:  Re:
Sidewinder wrote:
Adding enough weight to get a significant (felt) recoil effect to a normal piston is hard as there is little space other than the piston face to do so. Ideally you'd want to make an entirely new piston out of a much heavier material (eg. steel) this would probably be expensive though.

You could replace the piston head with a shaped block of lead. Also it's possible to drill out the spring guide and the back of the gearbox and then have a rod fixed to the front of the piston running all the way out the back of the GB with a second weight secured to that. Need to be aware of it interfering with upper/lower rec'er assembly etc though.

This all will probably stress the gears etc more so unless you want to spend a lot on high quality gears etc (not worth it IMO) i'd just get a less powerful main spring or shorten the one you have (so it's still under V slight compression at rest). Also put some sort of cushioning on the 'piston' face and cylinder head face to soften the impact, otherwise you might crack the gearbox.

Avoid a high speed setup as the weighted piston will prob be too slow on return and get caught by the sector gear. Use the standard GB/motor initially.

SAS


Pretty much hit the nail on the head there, I reckon.

You could (in theory and at your own risk)- cut the spring down until only 3-4mm protrudes into the piston, then fill the space left with air rifle pellets (lead). Mix up a big batch of epoxy resin and 'pot' the pellets in place to fill up the spaces and fix them.....Remove the piston O-ring to reduce the friction.

This is a cut price option- it will need cushioning at the end of the piston and you can bet that steel gears will be needed sooner rather than later.
Author:  Rob [ Sun Nov 02, 2014 11:04 pm ]
Post subject: 
Thanks for the feedback. :idea:

@robedavies: I have seen the video and I might add a moving bolt. But did we ever see it move in the movie? By itself the mod wouldn't add any big recoil, but perhaps it can be combined with a weight to create more kick.

@Sidewinder: Wouldn't it be possible to use the entire piston for adding weight? My idea is to mount something heavy (lead stick or similar) inside it and then adjust the spring length accordingly. Edit: demoncase pretty much summed up my idea in the post above. :)

My main concern is what should absorb the impact of the weight. I've heard about cracked gearboxes so it might be a good idea to try and divert the energy somewhere else, I'm thinking upper receiver. How that would be accomplished is another matter, perhaps something like the mentioned rod out the back.
Author:  demoncase [ Mon Nov 03, 2014 8:29 am ]
Post subject: 
Something like a wedge of felt or sorbothane at the front of the piston is probably the best bet.
Author:  Sidewinder [ Mon Nov 03, 2014 3:40 pm ]
Post subject: 
The Thompson is open bolt so on the functioning prop the charging handle reciprocates during firing. However (in the imaginary world of Aliens) as the PR uses caseless ammo I would think the charging handle would remain still.

The piston fully retracted goes just about all the way to the back of the gearbox, so if you filled the piston with ballast there would be no space for the spring itself. In normal operation most of the spring (and the spring guide) end up inside the piston body when it's fully pulled back - so while you might get away with putting a bit of stuff inside the front of the piston you can't fill it up and still have it operate.

I doubt DC's suggestion will work as there won't be enough space for the fully compressed spring due to my points above, also you would have to cut the spring guide right down which could lead the spring to deflecting in to the GB walls and jamming the piston.

As for impact absorption some soft material on the piston face and cylinder head should be sufficient to prevent GB damage.
Author:  Xhiwar [ Mon Nov 03, 2014 3:52 pm ]
Post subject:  Re: Recoil mod
Sidewinder, I thought so as well (i.e. Bolt would stay closed), but then Ttaskmaster once told me this, and I quote:

Ttaskmaster wrote:
Even though no case is ejected, the weapon is still magazine-fed, which means a bolt has to move back and forth to strip rounds off the magazine, before loading and sealing it into the chamber. Otherwise the round firing from an open chamber would set off all the others in the magazine.

Makes sense to me...
There certainly wouldn't be any ejecting cases like in the movie though. 8)

Cheers!
Roman
Author:  Sidewinder [ Mon Nov 03, 2014 4:03 pm ]
Post subject: 
Yes obviously there has to be a moving bolt to do as Tt says. However, in my mind the (fantasy) PR's bolt handle and cover plate(yes I know that's the actual bolt in real life you can see and not a cover) aren't fixed to the bolt itself so don't move with it during firing. So unless you are actually charging the weapon for the 1st round (or ejecting an unfired round) it stays still, operating in a similar way to the M16 family.

SAS
Author:  Rob [ Sun Nov 16, 2014 6:51 pm ]
Post subject: 
I have started hacking my gearbox now and this is the current state:

Attachment:
RifleModL.jpg
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I removed the piston head and replaced it with a solid weight where I can screw in a long 8mm threaded rod that extends towards the front all the way through the outer barrel.

I will use the existing hole in the barrel (where the bullet counter sensor used to be) and insert a stop there which the rod will impact and this will hopefully generate the recoil force.

This is all theoretical at the moment since I haven't fired the gun yet because I need to order a new motor. I'll spend some more time tweaking this mod so any suggestions are welcome!

I might for example add a second (spring loaded) rod that extends out the back which would add some more weight to the system. As well as being able to move the bolt plate, if I want to do that.

Attachment:
RifleModCU.jpg
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Author:  skapunkninja [ Thu Dec 04, 2014 9:44 am ]
Post subject: 
You'll probably want to order a high torque motor, torque up gearset and a hefty lipo battery to be able to handle all that extra weight
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