Has anyone ever seen Plastic grommets?

[Viking 0]

i don't mean like normal plastic. I mean that super hard stuff. Maybe coat it with teflon or somthing. I was talking with one of my buddies at the dropzone. He flies a Volocity 84 and he showed me his lines. They were all grey and slightly worn. He said thats from the slider coming down the lines. So the first thing that poped into my head was to put somthing with less friction on the grommets so it can't geat up the lines. So has anyone ever seen anything like this? Chuck?

I swear you must have footprints on the back of your helmet - chicagoskydiver
My God has a bigger dick than your god -George Carlin

[fasterfaller 0]

I dont think that they would last very long . I also think they would tear the lines up faster and would be more likely to snag . He could wax the lines .

[petur 0]

A good idea is a good idea, but this just popped into my head:

I guess plastic grommets, made even from "super hard stuff", will probably have some burn marks in them after sliding down the lines. One sharp edge on one grommet could cause severe damage to the lines after a very short while.

The shock from severe hard openings could also deform the plastic grommet over time, making it sort of oval shaped instead of round which will make the lines tend to lean towards the narrower ends of the oval and excert more strain on these areas... thus increasing the chances of excessive wear and... you know what

Teflon may be too soft, you can easily make a mark in a teflon coating with your fingernail. Try it yourself on the red teflon cutaway cables (if you can get hold of one that's not in use) and think of what will happen once the lines have made it through the coating...

Effects of rapid temperature changes should also be considered.

---
P.
"It Hurts to Admit When You Make Mistakes -
But When They're Big Enough, the Pain Only Lasts a Second."

[ernokaikkonen 0]

> He flies a Volocity 84 and he showed me his lines. They were
>all grey and slightly worn. He said thats from the slider coming
> down the lines. So the first thing that poped into my head was
> to put somthing with less friction

I suppose Velocities come with stainless-steel grommets? I don't think there are any practically usable materials slicker than that... Vectran lines do wear out quite quickly on HP-canopies, and should be changed around every 300-500 jumps. How many jumps are there on the canopy in question?

Erno

[ernokaikkonen 0]

>He could wax the lines .

??

There was something wrong with the "full profile" link, so I couldn't check your rigging qualifications, but judging from your other posts, you are a rigger.

I have never heard of people waxing their lines, and would be careful about applying any chemicals on mine. What kind of wax could be used? Would it really make a difference?

Erno

[weid14 0]

brass and stainless have a very low coefficient of friction. these have proven reliable -- there are manufacturing concerns, too, that would have to be addressed in trying to use any type of plastic. In my experience brass will discolor things, but it doesn't change the integrity of the material in question.

That said, I thought Dave Brownell (of slider rebound fame) was playing with a slider that had some sort of engineered material in it where the lines went through, but can't remember exactly what he was doing (he could have also been using metal, but not as much -- if I remember correctly he was trying to make the slider lighter in weight to help with hard openings)

[SkymonkeyONE 4]

A search would give the answer to what Dave is up to, but I am far too lazy right now. Anyway, he found a source for some very lightweight grommets. I don't know that they would discolor the lines any less, but personally, I don't care that lines get discolored. It's when they start shrinking, stretching, or getting frayed that you consider replacing them.

Chuck

[riggerrob 643]

Dave Brownell was using aluminum for slider grommets.
He even asked me to take a few measurements of the aluminum grommets on an old Para-Flite Swift 5-cell reserve. Back in the 1980s, both Para-Flite and National tried using #5 aluminum grommets. #5 grommets worked well on reserves, but not on mains. It seems that fat Dacron lines and sloppy packing resulted in too many slider hang-ups on mains.
Dave used anodised aluminum tubing to build his experimental sliders. They worked well, but things ground to a halt when he encountered geometric and health problems. I tried to offer him a solution, but I guess he is too busy with health problems.
One other factor to consider with aluminum or plastic grommets is denting when they hit metal connector links. I doubt if aluminum or plastic grommets would last very long with metal connector links. The obvious solution to preventing denting is to use soft links like PD Slinks.
Finally, the black discolouration on Vectran lines is just iron oxide rubbing off the stainless steel grommets. When stainless steel corrodes, it produces a gray or black oxide that is ugly, but harmless. When aluminum corrodes, it produces gray aluminum oxide.
This largely a cosmetic problem.

[cobaltdan 0]

the vx has aramid lines. the burn marks were not burn marks as rob pointed out.

on a slider first you do not necessarily want to reduce friction. assuming you did, a spectra/vectran to bearing plastic given the operating pressures and speeds would not provide any lower friction than ss.

on our guided parachute systems there was a situation where i wanted to lower friction of a guide and a line. the solution was not plastic but to impregnate the line with moly. disulfide a high pressure dry film lubricant. if you want to play arround with it make sure you impregnate the lines with an alcohol based suspension not petroleum.

btw its black and messy...

sincerely,

dan

Daniel Preston <><>
atairaerodynamics.com (sport)
atairaerospace.com (military)

[fasterfaller 0]

You can wax lines with beeswax . It does attract dust and dirt to lines which can also do damage . There is a reference to it in the parachute manual . I do not know of anyone still waxing lines but it is an option .To answer your question about rigger qualifications , I am a rigger and have been for many years .