Reserve PC size question

[AggieDave 6]

Alright, here's some questions I really should know the answer to, but I don't know:

Are all reserve PCs the same size on sport rigs? If not, is the spring used the same kind of spring/same sized spring (not between brands, which I understand vary, but within the same brand).

If the PC is the same size, what is was the standard to determine the size to be used? A 200sq ft reserve or what? Also, if the spring is the same size, how was that standard determined?

Last one: Is the spring used in pop-top style reserves under the same guidelines for "springy-ness" as a non-pop-top reserve and how does the weight of the pop-top effect it?

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[Samurai136 0]

The force of the spring only has to be strong enough to pull the bag out of the container and 'anchor' the system until full line stretch. So all Javelin pc's are the same size, etc etc. Usually there are no banded line stows and the locking stows are usually about 1" or so. Reserve deployment is designed to be very fast. After that the PC does nothing but slow the free-bags decent.

An variance in the strength of the spring is determined by the Manufacturer. Some PC's have to push past 4-6 flaps to get air, others are immediately exposed.


edit: to answer your question. any one manufacturer only has to determine a sufficient spring strength to facilitate a rapid line deployment.


Ken

"Buttons aren't toys." - Trillian
Ken

[Hooknswoop 19]

Quote

The force of the spring only has to be strong enough to pull the bag out of the container and 'anchor' the system until full line stretch.

The pilot chute pulls the free-bagged reserve out of the container, not the spring inside the reserve pilot chute.

Withing a particular model, the reserve PC is the same size. The reserve pilot chute in my old Javelin XRS is the same size as the reserve PC in my J4. The XRS had a 109 reserve and the J4 has a 220 reserve, with dacron lines. There is a noticable difference in time to line stretch between the two rigs.

I've always wondered if the small rig's reserve PC was too big or the large rig's reserve PC was too small.

Hook

[Rdutch 0]

I know the Vector sport reserve pilot chute and the tandem reserve pc, are the same. Oh yeah they also use it as a main pc for spring loaded student rig's. Mirage and Relative both use the same spring, its somewhere around 44 lbs of force. This much is needed, as their is a few flaps they have to open.
Pop top rig's such as the racer have a much weaker pc and some riggers prefer this, but it works just as well, as there isnt any extra force needed to launch it.
Spring is only a small part of the effectiveness of a pilot chute. A lot more goes into it. Most pilot chutes have around 100 lbs of pull force, some less some more. But they are all tso'd so they all work.

Ray
Small and fast what every girl dreams of!

[faulknerwn 38]

I know Jumpshack has 2 different size pc's (at least). There are the normal sized ones and then ones which are a much smaller diameter - mainly used on the small rigs like the power racers.
W

[riggerrob 643]

Reserve pilotchute size is determined early in the design/TSO process. For example, all Vectors - whether they be huge-ass military tandems or the tiniest Micron - all use the same size reserve pilotchute.

We are really discussing two separate variables: spring strength and fabric area.
Spring strength was codified a long time ago in a military specification. 18 pounds of force is the minimum, but most new pilotchutes are in the 20 to 30 pound range.
The spring has two functions. First, the spring has to push flaps out of the way and secondly, it has to launch the pilotchute beyond reach of a tumbling jumper. Once the pilotchute is beyond arms length, it has done its job.
The only reason Racer reserve pilotchutes come in two different sizes is that the smaller diameter looks prettier tiny Power Racers. A Power Racer pilotchute spring pushes as hard and has as much fabric as a standard Racer pilotchute.
There are two basic configurations for pilotchute springs: conical and cylindrical.
The majority of reserve pilotchute springs are just slightly updated versions of the ancient military MA-1 conical spring. Even Vectors use an inverted version of the MA-1 spring.
Cylindrical springs are found in Talons, Wings, etc.

The second variable is fabric area, which is determined by the weight of the reserve canopy. Since most reserve pilotchutes were designed back in the days of 200 square foot reserve, they are way over strength. Since the freebag and safety stow allow you to use an over-sized pilotchute, this is not an issue.