Here's one solution to ULT reset - MAULT mag

[Spider-TW]

I have run into schedule problems with play testing this thing any time soon, so I will just throw it out here.

What if you went to the same trouble to reset the trigger on a ULT that you would on a cranky pneumag? Throw in a magnet and a spring? The automag sear is magnetic steel. If you put a magnet in the bottom of a ULT pin, it will stay attached to the sear. Then, you need to give the sear a small push to return. I presently do that with a small spring stuffed between the back of the intelliframe and the bottom tip of the sear, opposite the clevis. It's a magnet assisted ULT.

The magnet is a rare earth (40 something, not the newer 50 something) .1" diameter by .1" long. I disassembled the ULT, drilled the bottom, and used red loctite to hold the magnet in place. The pin bottom is slightly magnetic, and it sucks the magnet into the pocket. Residual loctite can keep the pin from setting all the way down in the bottom, so that assembly could use a tweak to make sure the overall pin length doesn't get any longer (and maybe try to make it shorter).

On a classic, the spring return is a little squishy still. My ULT isn't tuned very tight. I hear shootdown over about 6 bps, which might get better with some ULT washers. However, the idea is to match this up with a light solenoid and an x-valve, and make that sort of setup more reliable.

Given the o-ring openings between the RT on/off and the ULT, I expect that if I can get ~16 bps out of a classic with an RT on/off (electronic controlled), I should be able to get about ~8 bps out of ULT with electronics. I kind of expect that my fingers are going to limit me to 4 to 6 bps on a regular frame, even if the pull is relatively light. So far, I have had no trouble with sear resetting or the ULT not opening up, even though I have not tuned the ULT to the edge.

Here's the pin bottom drilled.


and magnet mounted.


Here is another version I made, with a .125" dia x .125" long magnet, loctited on the face. The final assembly wasn't as easy as the drilled magnet mount. Since the drilled magnet mount is working (with the smaller magnet), I haven't gone back to this one.

[BigEvil]

Wont the magnet wear rather quickly? How about a magnet inside the on/off top hole, and another on top of the ULT pin to 'push' the ult pin down?

[captian pinky]

interesting.

[Spider-TW]

Wont the magnet wear rather quickly? How about a magnet inside the on/off top hole, and another on top of the ULT pin to 'push' the ult pin down?

If it gets gritty, it will wear. I already had polished the sear surface. The magnet is nickel plated. With a little lube on it, light testing hasn't shown any marks. The magnet isn't too strong, just enough to break the o-ring friction. I had considered coating it with something, but I am also curious about the wear. This first part is just to see if the magnet would be enough to hang onto the sear against the friction. Wear is also why I went with the magnet insert; it was easier to replace and after it wears it will get down to the stainless pin sleeve (which probably could have been made the contact surface).

That pin top is awful skinny to work with, but opposing magnets might work also. What might be nice for a classic is an RT size pin-top with a magnet assisted ULT shaft. Rather than mounting something in the on/off cavity, we could probably design a laser print on/off body (or just top) that would hold ring and/or flat magnets.

I bought these magnets from K&J magnetics, they have some tiny ring magnets that might work in an on/off body or top.

http://www.kjmagnetics.com/products.asp?cat=16

This is the one I'm running,

http://www.kjmagnetics.com/proddetail.asp?prod=DH1H1

I can dangle the sear from the ULT pin, which is neat.

[Spider-TW]

I did try to mount opposing magnets on the sear, ala pneumag, MSV-return. It needed an arm to get the sear magnet away from the sear. If the sear magnet was just sitting on the sear, the opposing magnet would get attracted to the sear at the same time it was opposing the sear magnet. That was more than I wanted to fight for testing, hence the light spring.

Those were thin, flat magnets. A long one on (and away from) the sear might fix that.

[Spider-TW]

Actually, after fiddling around with these, I think I can get a tiny spring in there to compensate for the o-ring drag.

[nak81783]

Doesn't the spring increase trigger pull, which defeats the purpose of having the ULT?

[Spider-TW]

Doesn't the spring increase trigger pull, which defeats the purpose of having the ULT?

Yes, slightly (depending on the spring). As long as the pull is still about 1/3 of an RT on/off, it would still leave the ULT in the range of a small pancake solenoid.

Putting a spring behind the sear does the same thing with the magnet assist.

[nak81783]

The goal being a walkable trigger or just a lighter pull with more reliable reset?

If interested, I played around with some concept on/offs a while back. If memory serves, there are still a few combinations of standard orings and respective pin diameters (shaft and head) that could give favorable (or at least temporarily fun) results. Could use modified versions of existing parts to test.

[Spider-TW]

The goal being a walkable trigger or just a lighter pull with more reliable reset?

If interested, I played around with some concept on/offs a while back. If memory serves, there are still a few combinations of standard orings and respective pin diameters (shaft and head) that could give favorable (or at least temporarily fun) results. Could use modified versions of existing parts to test.

Reliable reset mainly. It is ... about half the weight of the RT on/off. If you can't walk a tuned ULT in an x-valve, this won't help. I can't really walk a ULT, but I know a couple of guys that used to walk cocker hinge frames, so it's a little relative.

It does make the classic pull pretty light. I should try tuning/shimming the ULT; the pull is pretty long atm.

I have some on/off parts myself. All of my weekends are booked for a while though. I can tinker at night, but actual play testing is "too future."

***

You know, real play testing requires having at least 5 people standing around waiting to shoot at you. That seems to draw out the gremlins real well.

[nak81783]

I understand life gets busy. Thanks for sharing this. Cool little project. Hope you get it to work to your liking.

[GoatBoy]

Kind of reminds me of the magnetic effectors on delta printers.

I think the magnetic hinge (if I'm reading all this correctly) is a good idea... putting a spring on the trigger -- not so much.

It would be better to get the trigger to reset reactively with energy that wasn't a part of pulling it in the first place.

Nearest source is... the bolt itself. The bolt pushes forward with lot of excess energy, and returns with a lot of excess energy. So much so that it has to be slowed down.

If that energy could be recaptured and directed at resetting the sear (which would then be linked to the on/off)...

[Spider-TW]

Kind of reminds me of the magnetic effectors on delta printers.

I think the magnetic hinge (if I'm reading all this correctly) is a good idea... putting a spring on the trigger -- not so much.

It would be better to get the trigger to reset reactively with energy that wasn't a part of pulling it in the first place.

Nearest source is... the bolt itself. The bolt pushes forward with lot of excess energy, and returns with a lot of excess energy. So much so that it has to be slowed down.

If that energy could be recaptured and directed at resetting the sear (which would then be linked to the on/off)...

Yes, the spring makes it a bit mushy feeling. A full magnet setup on the trigger could probably fix that, but it would still be too stiff to walk for me. At least now that I have a grip on the on/off pin, I can tinker with that return force anywhere along the way.

I got my tiny springs in for direct mounting in the ULT; I think I could make those return from 1 to 4 ounces, depending on how deep I mount them. I may just pick something and try it.

What I'm wandering around is an EM classic build and untuned (or less critical tuning) ULT operation. Once you get it to return, you can design around an on/off that has half the force of an RT on/off (I hope). I think I may trim a little on the next ULT to see if I can get a little better flow and tinker space.