Thanks: 
Likes: Because it's winter and some guys may need some. This is a good price!
https://www.backcountry.com/black-di...SABEgLI6_D_BwE
Because it's winter and some guys may need some. This is a good price!
https://www.backcountry.com/black-di...SABEgLI6_D_BwE
dont be cheap
buy the style of screws with the little hand crank on em. So much quicker to set!!
Snap a carabiner on it and it makes a great handle. Not ideal for an ice climber but it works great for my use.
The reason I found those is because I want to buy some screws to test lateral and diagonal pull strength. I want to know how much pull it takes to have the tie arm fail. Those Black Diamond screws are what I've carried in my winter gear for 20 years. I'd like to know what they can take. One plus for those screws over the more expensive ones is they're carbon steel, not aluminum.
Last edited by stewartb; 11-23-2020 at 09:33 AM.
BC12D-4-85 liked this post
Almost twenty years ago the Russians were dumping a lot of titanium on the market. I bought three titanium ice screws with carbide tips - very light and (I think) quite strong.
I just wish that I had bought a set of titanium cooking pots when they were available at a reasonable price!
Originally Posted by NunavutPA-12
Lots of both on ebay
Glenn
"Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"NunavutPA-12 thanked for this post
So these strong enough for a 180?
To tie one down? Depends on ice composition and how much wind. My 180 probably never sees higher than 40mph when tied to screws but I've never had one loosen.
Think about it. A Cessna wing will lift GW at not very high speed. If it is windy, you will need a pretty hefty tie down if pointed upwind and the wing is clean. A friend of mine tied his 180 to two snow machines on a windy night and later noticed it was lifting both machines off the ice. Luckily they changed the setup before any damage.
Ice screws are handy but tricky. They will melt out under the right conditions and will pull out under enough vertical tension.
Ropes to the ice screws need to be angled towards the wind. That creates an initial shear force on them vs vertical load on their threads. And gusts can create pressure on the screws which melts adjacent ice. They will walk away from the gust direction so put them in top angled slightly towards the wind to begin with. I also like one on the tail and one to the landing gear to prevent aircraft creep back. Plus spoiler wing covers and a martini for sleep.
Gary
And that's why I'm motivated to test them. Ice screws are designed for sheer loads but we use them primarily in tension. I suspect the clip arm will fail and separate before a screw pulls out of good ice. In my use I'm trying to keep my plane from sliding in the wind. If I'm hoping to overcome lift I'm using the wrong tool. I have tied snowmachines and heavy sleds to my plane to supplement the screws overnight but that's rarely necessary.
My 180 sits nicely in winds that would blow my Cub away. Paul asked if ice screws are enough for a 180. My question is are they enough for my Cub. If I parked the Cub in a 30mph wind with scope in the lines to the upwind? The plane would increase AOA and try to fly. I need this plane pinned firmly to the ground with no scope that will allow AOA in increase. The screws will be in tension and I'd like to know what the fail load is. I have screws, a lake, and a tractor to test with. I just need to figure out a shield to protect me when the screw fails and the line backlashes.
Last edited by stewartb; 11-24-2020 at 10:22 AM.
Here is a pretty comprehensive summary of drop tests on ice screws:
https://mra.org/wp-content/uploads/2...rews_Final.pdf
Essentially the angle should be ~20 degrees towards the force, and in good ice should expect to hold up to 10kN (~2,250 lbs).
Stewartb, might I suggest draping something cloth (blanket for example) over the line about half way towards the screw in your pull test. Actually anything you can tie to the rope will help absorb the energy when the ‘release’ occurs. I’ve seen a winch line ‘release’ while winching a vehicle, and this really helps dissipate the energy and slow the projectile.
I always drape a canvas tarp on ling winch lines. This will be a short line with a chunk of steel on the end. The line won't be what fails. New territory for me.
Do you think the attachment loop will fail? Just another chunk of line also attached to the loop would work. Just thinking out loud. Anything to slow that thing down.
I "think" the attach arm will fail before the screw releases but I may be wrong. If the screw comes out the projectile is much more dangerous. Right now we have clear, hard ice so I should get a good bite. I want to know how these things will fail in an application they're not designed for. Maybe this weekend.
Last edited by stewartb; 11-24-2020 at 11:17 PM.
stewart are you doing this with a tractor that has a front end loader? if so weld a lug to the inside of the bucket and while pulling keep the bucket in a position that when the fail happens the line and whatever comes with it recoils back into the bucket. most people have a lug on the top edge for pulling (I'm guilty of this, haven't gotten around to adding the internal lugs yet on my equipment) and when stuff breaks the line wips back and up towards the cab as you most likely already know. if your hauling from the back using a 3 point hitch to pull up, I'd stick a piece of plywood between me and the back of the seat and hope for best. a heavy steel cable rated for much more then the force you plan that wont stretch and store energy should make things less climatic to.
Good suggestions. Thank you! I have a loader and a hoe. I'll see if I can finesse the levers well enough for the scale to read accurately.
What about attaching another line loosely on the screw and anchored to arrest the screw when it fails?
Sent from my iPhone using SuperCub.Org
Stewartb, did you get a chance to do some testing?
No, the weather changed to mid-40s for a couple of days so I'm waiting for colder weather and better ice.
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