0
pchapman

Sentinel 2000 pin-puller AAD with Micro Puller

Recommended Posts

Since there's some interest lately in the idea that pulling the pin might be an option for AADs, I thought I'd mention the old SSE Sentinel.

In particular, the "Micro Puller" they had in the last years.

(The current thread on the pulling issue is titled "Cutting the loop or pulling the pin?" in Rigging)

Traditionally the Sentinel was a cigarette package sized box (containing an aneroid capsule & electronics & adjustment controls) mounted outside the rig, and had had a very large puller assembly. Initially they were attached to a belly mount reserve.

The first ones I saw had the puller mounted on the top reserve flap of 2 pin piggyback reserves, where they could interface with the ripcord. The electronics box was typically mounted near the hip on the rig.

I can't quite recall how the pullers worked, but I think an electrically actuated pyrotechnic charge forced a piston to move inside a cylinder, with a metal arm sticking out. That arm caught on a cylindrical piece that went over the ripcord, between the two pins was it? Thus it could push on the "V" between one pin and the cable to the next pin? One must have had about 4" of tubes and brackets involved - quite bulky.

Later on they had a pin puller assembly with two closed tubes that would fit in the reserve tray, and had a pulling cable much like that on an FXC -- a metal loop on the end would grab the ripcord pin, with a cable going into an armored flexible housing leading inside the pack.

Finally in SSE's last years they had the Micro Puller:
It didn't appear in the '90 Para-Gear manual, but did in the '93, for example.

The Micro Puller was actually pretty neat and nothing like the unwieldy and clunky earlier pullers. No rig modifications were now needed for the puller, although the electronics box still had to be put somewhere.

What disadvantages might the Micro Puller have? One PIA publication noted that the Micro Puller wasn't compatible with certain RSL systems, in particular the Vector II style "eye on ripcord & figure 9 RSL pin". Somewhere else there was some bulletin about making sure the pull distance would be sufficient with some ripcord. But it would work with normal ripcords. One might look into any possible friction issues between the puller's moving parts and the lip of the reserve top flap grommet, if it were poorly positioned.

But overall I heard no complaints about the system, which was rare overall. Yet a DZ where I jumped, Sentinels with Micro Pullers were somewhat popular in the mid 1990s.

The puller was advertised as having a 100 lb pull force, which was achieved with just a very slim firing cylinder in the puller, one much slimmer than the cutters for Cypres' etc.

The problem with pullers in general is that if the ripcord is being pulled, they have to push off of something with the same high force, and that has often meant some metal hardware that's bolted to the reserve top flap for rigidity. The Micro Puller instead pushed off of the closing loop itself, so no rig mods were needed for the puller.

While I'm happy with loop cutters (when well designed), the Micro Puller was a pretty neat little gadget.

Anyone have a better photo of the Micro Puller? I just can't find anything out there.

Share this post


Link to post
Share on other sites
I have a few of these. What an ingeniuosly simple design. Not one line of code, no digital electronics, just a couple of AA cells, an altitude and rate sensor switch in series and a resistor capacitor delay to prevent contact bounce on landing from firing the pin puller. For belly flyers I think it worked pretty well.

I am personally responsible for the SSE Sentinel 2000 mod to prevent landing misfires. I jumped an old 28 foot C9 canopy that was porous and my landings were damned hard. Twice I had my Sentinel 2000 fire on landing. I landed with such high force that the aneroid switch contacts momentarily closed from G forces and fired the puller. I talked to Steve Snyder who at first didnt believe me, but after the second event did and put out a mod to prevent it.

I had a long talk with the Airtec and SSK guys at WFFC one year during a mini storm. I am an EE had long and interesting technical discussions with them. I asked them why they didnt go for a dirt simple design like the SSE Sentinel 2000. They told me that false trigger events would occur with that design on tumbling high speed exits, and on some of the more radical freefall and canopy maneuvers. According to these experts there are pressure spikes and dips caused by falling body aerodynamics and only software can sort them out.

377
2018 marks half a century as a skydiver. Trained by the late Perry Stevens D-51 in 1968.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account. It's free!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
0