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USnavy
Mar 6, 2012, 10:23 AM
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I have a pull back ram which works great to pull test metal gear. However the 6" stroke lacks the distance to pull test any soft goods. Does anyone have an idea of a pull back ram or similar device with a much longer stroke? I have seen people use winches and the sort, but I would rather stick with something a bit safer and more static.
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JimTitt
Mar 6, 2012, 7:07 PM
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A ram long enough is a gigantic thing and the pump needs a huge oil capacity to fill it. I built a portable soft-goods tester for the BMC for demo´s which works o.k. But they end up long, for 120cm nylon slings mine ended up 2,4m (about 7´6" or so), I made it in two parts to fit in a car boot.
Basically you leapfrog the ram up a steel backbone by attatching it on a sliding mounting and the hook end on a similar sliding mount. You put a pin through the cylinder end, pull up, pin in the hook end, remove the ram pin and release the ram. Keep repeating. Bit slow but works o.k.
Otherwise a really powerful chain hoist or cable puller is the only way to go. For the nasty stuff I use a 5 ton logging winch but you need a tractor to go with it!
I´ve some photo´s somewhere I can mail you if you want.
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bill413
Mar 6, 2012, 9:09 PM
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Would a lever to amplify the distance moved by the ram work, or would the proportional loss of force require an impractical ram?
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majid_sabet
Mar 7, 2012, 12:19 AM
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USnavy wrote: I have a pull back ram which works great to pull test metal gear. However the 6" stroke lacks the distance to pull test any soft goods. Does anyone have an idea of a pull back ram or similar device with a much longer stroke? I have seen people use winches and the sort, but I would rather stick with something a bit safer and more static.
its called PULLEY system but you probably do not know how to use it to get twice as much distance with 6"
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USnavy
Mar 7, 2012, 5:27 AM
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majid_sabet wrote: USnavy wrote: I have a pull back ram which works great to pull test metal gear. However the 6" stroke lacks the distance to pull test any soft goods. Does anyone have an idea of a pull back ram or similar device with a much longer stroke? I have seen people use winches and the sort, but I would rather stick with something a bit safer and more static. its called PULLEY system but you probably do not know how to use it to get twice as much distance with 6"
(This post was edited by USnavy on Mar 7, 2012, 5:32 AM)
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majid_sabet
Mar 7, 2012, 6:42 AM
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USnavy wrote: majid_sabet wrote: USnavy wrote: I have a pull back ram which works great to pull test metal gear. However the 6" stroke lacks the distance to pull test any soft goods. Does anyone have an idea of a pull back ram or similar device with a much longer stroke? I have seen people use winches and the sort, but I would rather stick with something a bit safer and more static. its called PULLEY system but you probably do not know how to use it to get twice as much distance with 6" Homeboy Majid Idoit, I cannot test soft goods like a rope or a piece of webbing with ONLY a 12" stroke, I need MORE travel distance than that. Beyond a 1:2, a 10T pull back ram is USELESS. It does not have the power or stroke to drive a pulley system any more COMPLEX than that. Once you get to a 1:3 and above, you have TOO much crap in the system, its going to stretch and eat up your travel distance, even if you are using steel cable. Also, with all the FRICTION from the turns, a 1:3 might give me at MOST 2000 lbs. on the load piece which wont cut it. Those 10T rams are NOT actually 10T, not with a hand pump anyway. The most I can get out of a hand pump and pull back ram is about 8000 lbs, and thats by STANDING on the handle.
Here, use my land cruiser and tie the back bumper to royal arches behind it and tie the winch and whatever you got to elcap and push the switch to activate the 10.000 lbs 135 feet cable and see where your project ends up.
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binrat
Mar 7, 2012, 12:53 PM
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Attach the pulley to the ram and you'll have about 24" of pull and 1/2 the capacity (5 tons??). Or buy a longer ram to do it.
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USnavy
Mar 7, 2012, 1:37 PM
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majid_sabet wrote: USnavy wrote: majid_sabet wrote: USnavy wrote: I have a pull back ram which works great to pull test metal gear. However the 6" stroke lacks the distance to pull test any soft goods. Does anyone have an idea of a pull back ram or similar device with a much longer stroke? I have seen people use winches and the sort, but I would rather stick with something a bit safer and more static. its called PULLEY system but you probably do not know how to use it to get twice as much distance with 6" Homeboy Majid Idoit, I cannot test soft goods like a rope or a piece of webbing with ONLY a 12" stroke, I need MORE travel distance than that. Beyond a 1:2, a 10T pull back ram is USELESS. It does not have the power or stroke to drive a pulley system any more COMPLEX than that. Once you get to a 1:3 and above, you have TOO much crap in the system, its going to stretch and eat up your travel distance, even if you are using steel cable. Also, with all the FRICTION from the turns, a 1:3 might give me at MOST 2000 lbs. on the load piece which wont cut it. Those 10T rams are NOT actually 10T, not with a hand pump anyway. The most I can get out of a hand pump and pull back ram is about 8000 lbs, and thats by STANDING on the handle. activate the 10.000 lbs 135 feet cable and see where your project ends up. [IMG]http://img193.imageshack.us/img193/7268/yosfeb1.jpg[/IMG]
p.s, that POS push bar of yours is never going to hold 10,000 lbs, that thing would twist off the frame like a noodle, get yourself a real push bar that is actually designed for the winch you have. My bar warped out a bit when I [nearly] stalled my winch out that one night and I made it. Its made out of 3/8" AR200 structural I-beams welded with CoreX high strength .045 wire using 95/5 argon shielding gas on a 480 VAC Miller MIG welder. Not that you would know what any of that means.
(This post was edited by USnavy on Mar 7, 2012, 1:54 PM)
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USnavy
Mar 7, 2012, 1:57 PM
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binrat wrote: Attach the pulley to the ram and you'll have about 24" of pull and 1/2 the capacity (5 tons??). Or buy a longer ram to do it.
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majid_sabet
Mar 7, 2012, 4:59 PM
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USnavy wrote: binrat wrote: Attach the pulley to the ram and you'll have about 24" of pull and 1/2 the capacity (5 tons??). Or buy a longer ram to do it. I would have 12" because its a 6" ram. I have been looking for longer rams but have turned up short (unless I want to spend four figures on just the ram itself). Something with say a 12" stroke and a pulley would work.
go back to MC burger flipping job and leave the testing and building testing rigs to pros. Ebay has long range hydraulic actuators used on construction equipment cheap and do not lecture me on how to build cars.
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JimTitt
Mar 7, 2012, 6:25 PM
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As you are working out there is no easy cheap way unless you have some heavy plant lying around, over the years I´ve used 50 ton cranes, a Komatsu excavator and nowadys a 220hp McCormick, with or without a forestry winch. 10 ton pull cylinders are rated for the load they can withstand, not what they pull. Like most of this kind of gear (cable haulers etc), they have to have a safety margin for the mechanics or hydraulics. I could pull 3600kg on mine with both arms but I´m reasonably well built, like 215 lbs so about the same as you can get.
The pull distance is a problem, similar to the distance between Majid´s ears also being a matter of concern, for nylon you need at least 60% extension and Dyneema/Spectra 30+%.
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jowybyo
Aug 6, 2012, 5:11 PM
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When I worked in a materials lab, we would sometimes run into this issue. Instrons only have a finite stroke length. It helped that we had hydraulic jaws to clamp the material so we could test a very small section.
You might be able to do something similar to a drum grip. It's like a frictionless hitch around a cylinder. This reduces the amount of material in the test section (by removing knots, etc). Then you just need to make sure that the length of webbing, rope, etc in the test section in <3".
This is probably the best way to "grip" your material so you don't get failures at knots or clamps.
But I understand that sometimes it's just not feasible to get the material length short enough (i.e. is seams, stitching, loops or knots are involved)
Hope this was helpful.
-Joe B.
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knudenoggin
Aug 21, 2012, 12:48 AM
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JimTitt wrote: for nylon you need at least 60% extension and Dyneema/Spectra 30+%.
!! That seems quite a lot for HMPE, which in ropes
is usually given an elasticity at rupture of around 4%!
*kN*
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JimTitt
Aug 21, 2012, 7:02 AM
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knudenoggin wrote: JimTitt wrote: for nylon you need at least 60% extension and Dyneema/Spectra 30+%. !! That seems quite a lot for HMPE, which in ropes is usually given an elasticity at rupture of around 4%! *kN*
However in the common Dyneema hybrid tapes the Dyneema doesn´t run in a straight line but zigzags around the nylon, it must straighten first before breaking and thus the tape stretches. 30% is the value given by the manufacturers spec sheet of some samples I have.
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IrishBrewer
Feb 20, 2013, 5:50 PM
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I know it ha been quite a while since the original post in this thread was put up but I thought I would comment as I have been doing some testing of some slings on my own.
I tried to come up with a way to test slings using things I had on hand. My testing apparatus uses a 48 inch farm jack that has a capacity of 7000 lb (3.5 tons). I would rather have something that goes up to 5 tons but I figured that if a sling can hold 3.5 tons without breaking or being damaged, it should be suitable for climbing. The good thing about the farm jack is that it has plenty of travel for what I was testing.
I started off by making some end and mid links that would connect the slings to the jack and one sling to another sling in the middle. The thought here was that I do not have a load cell so I could put the test sling in series with another sling and jack them until one of them fails. This way each sling carries the exact same amount of tension and the weaker link will fail. I thought I could use a piece of climbspec (4000 lb) webbing tied with a water knot as one type of "fuse" and a single strand of webbing secured with line lockers as another fuse.
The end and mid links are made from steel bar stock with holes drilled to accept a 7/16" grade 8 bolt passing through a 3/8 inch piece of iron pipe. I figured that this would result in less stress at the bend than just about any carabiner because my intent is to test the webbing rather than the caribiner/webbing connection.
The slings I wanted to test were ones that I had made myself out of climbspec webbing sewn using a "proven" stitch pattern using heavy bonded nylon thread.
So far, the DIY sling has held up very well - I have not been able to break it. However, I haven't been able to break the water knotted sling in series with the test sling either. I was able to break the fuse made up of the line locked webbing in series with the test sling in two separate tests. There is no evidence of stitch breakage in the sewn loop after all of my best efforts to break it in the test apparatus.
I would appreciate any thoughts on what other types of tests would be suitable to run with this setup. Perhaps I could try a single strand of webbing with sewn loops at the ends. This might be a bit stronger than the line locked ends. While line lockers are supposed to result in minimal degredation in the strength of the webbing, in my tests the breaks did occur at one of the lockers so there does appear to be some loss in strength. If I can get the fuse to break away from the sewn loop, I'll know that I've got somewhere on the order of 4000 lb or better.
I can post some pics of the test apparatus if anyone is interested.
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