Where can I buy a compression spring?
July 18, 2004 3:46 AM   Subscribe

Where the heck do you buy a spring? Surprisingly interesting details inside.

I built a zipline for a kids playground, and because of the terrain, it's so steep that the kids slam into the end. Yeah, this is funny and all, but I'm thinking if I put a big spring at the end, or series of springs, it will soften the landing and enable kids to maintain their grip on the bar after "landing" so they can drop safely to the ground. So I need a spring at least 1' long, at least .5" inside diameter, and as few coils per inch as possible, for maximum boingboing-iness. Technically this is called a compression spring, as opposed to an extension spring.) All searches take me to manufacturers, where price for a run of one is prohibitive. Can you help me think of retail uses for a such a spring (car parts, etc.) so I can search retailers?
posted by stupidsexyFlanders to Shopping (16 answers total)
I assume car-suspension springs are too oomphy, neh? Unless the relevant kids all have the last name "the Hutt," anyway.

Are there springs in the suspension of go-karts and 3- or 4-wheel ATV's that might be more appropriately sized?

Does it need to be a springy-spring? Would not some manner of pneumatic thing that compresses and then rebounds do the same thing?

Or just go get approximately 6.02E+23 of those Granny-style hair rollers, take out the springs, and mush them together into MEGASPRING, sproinger of worlds.
posted by ROU_Xenophobe at 4:41 AM on July 18, 2004

A friend of mine bought a hundred springs not so long ago... I asked them the same question and can't for the life of me remember the answer. If I see them soon I'll ask though.
posted by ed\26h at 5:18 AM on July 18, 2004

Go here, and type "compression spring" in the search box. ("1187 items match your search"). They sell them in all sizes, in small packs, at very reasonable prices.

If these guys don't work out for some reason, just go to Google, and search on "industrial supplies" or "MRO". You'll find a ton of places like McMaster-Carr, Grainger, etc., and they all sell stuff like this.
posted by LairBob at 5:49 AM on July 18, 2004

have you tried a scrap yard?
posted by andrew cooke at 5:52 AM on July 18, 2004

would mattress springs do the job? if so, go with andrew cooke's idea of a scrapyard or a municipal dump.
posted by triv at 6:05 AM on July 18, 2004

Also consider doing something to the last section of cable that just creates friction to slow them down. That might create a more gradual effect as you could treat a long section of the cable.
posted by scarabic at 9:46 AM on July 18, 2004

Try American Science and Surplus, and be careful.
posted by funkbrain at 9:58 AM on July 18, 2004

A motorcycle spring should do the trick.
posted by five fresh fish at 10:00 AM on July 18, 2004

I was thinking bungee cords, if you can rig them correctly. See also "snubbers" at West Marine.
posted by baylink at 11:02 AM on July 18, 2004

the site linked to showed an old tyre being used.
posted by andrew cooke at 11:16 AM on July 18, 2004

I would think hard about the old tire. Some child, somehow, will figure out a way to get wedged in a spring.
posted by i_am_joe's_spleen at 12:42 PM on July 18, 2004

I've had good results using a mix of busted up and solid hay bales for this purpose, as has my roommate.
posted by jeb at 2:29 PM on July 18, 2004

Oooh. Mr. Spleen is dead on accurate about that. Some nosepicker will be wiping his boogers on the cable when, slam!, down comes the zipline and whack!, off comes his finger from 'tween the spring coils. Bad liability case there.
posted by five fresh fish at 2:51 PM on July 18, 2004

One other idea. Make the low end higher, and the cable slacker, so the the natural low point is a few feet before the end post. That's how the flying foxes I used as a kid were generally set up. (That's what they're called here, I never heard the term zipline before. I like zipline - it sounds kewl).
posted by i_am_joe's_spleen at 3:15 PM on July 18, 2004

You could always build a stop into the cable about 8 feet from the end and put a pile of mattresses under the tree at the end. Then again, it would probably only exacerbate the problem.

Trampoline anyone?
posted by blasdelf at 5:04 PM on July 18, 2004

I've spent time on a decent number of ziplines, and come across a series of methods of slowing riders down. My favorite is this.

Find a tree 3/4 of the way down the course. Run a cable from this tree to intersect with your zipline. Affix the cable to a heavy-duty bungee cord, and, in turn, affix that to a pulley, which is then attached to the zipline. The length of the cable and the bungee cord should be such that they are at their maximum length at the terminus of the zipline.

As you can imagine, this slows gradually and quite successfully, and is pretty simple to set up.
posted by waldo at 6:27 PM on July 18, 2004

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