Opened Turnbuckles

[buckland]

I have changed trucks requiring me to put a few inch platform in the bed. When I emailed FWC I was sent new turnbuckles (1 month ago) and eyebolt/plates. Well the distance is obviously increased between the eyebolts camper to bed. Terry told me to just buy "Quick Links" (which are screw type carbiners) to take up the added difference. Has anyone done this or does one suggest returning the tie downs and buying longer throw? Any suggestions where if so?

 

[billharr]

When I picked up my 2013 Hawk the front tie down points were farther back that the eye bolts on my 2002 Hawk. Had a 500 mile drive to home. I made a quick visit to HD and had to put two of the quick links on each side to make the turn buckles work. I did move my eye bolts in the truck bed as it was just easier to hook the turn buckles. The quick links are probably stronger that the turn buckles.

 

[kmacafee]

Has anyone thought about webbing like Black Diamond Dynex, single loop its 22kN, thats like 5000 lbs. I don't know exactly how to rig it but I bet there is a way. Adding knots and twists reduces its strength, but maybe a little slack would be OK. Even at 1/4 its strength 1250 lbs its 4 times stronger than the stock turnbuckles.

Carld -- I was thinking about webbing as well. They make Dynex in these Dogbone configurations (http://www.backcountry.com/black-diamond-dynex-dogbone?CMP_SKU=BLD00HO&MER=0406&skid=BLD00HO-WHIA-S18CMXS12MM&CMP_ID=PLA_GOc001&mv_pc=r101&utm_source=Google&utm_medium=PLA&mr:trackingCode=254C1C94-01D0-E511-80F3-005056944E17&mr:referralID=NA&mr:device=c&mr:adType=plaonline&mr:ad=92885922157&mr:keyword=&mr:match=&mr:tid=pla-150981978277&mrloc=9019549&mr:iloc=&mr:store=&mr:filter=150981978277&gclid=CjwKEAjwxce4BRDE2dG4ueLArHMSJADStCqMKTMO03kWJVhmJdXJhmAWbKuzOUizoYmu19DJobBR1hoC08Pw_wcB&gclsrc=aw.ds) and the 12 cm size is equivalent to the 4.5 inch forged turnbuckle I'm using now -- and significantly cheaper. Some carabiners or flex links on each end and this might be a great option. Certainly strong enough.

 

[WyoIDI]

The Dynex slings and dog bones for climbing applications are indeed very strong, but they are designed to used with a shock absorbing dynamic climbing rope. The do not respond well to what climbers call "static shock loading" which would probably happen in a camper to truck application, and any sort of knot or hitch will weaken them considerably too. Using a piece of actual dynamic climbing rope would be much stronger, but it derives it's strength from stretching and would not secure the camper tight to the truck due to this stretch, but it would work as a back-up to a failed turnbuckle well if it was tied to the anchor points correctly. I think this set-up (with an appropriate turnbuckle) would be a good backed up set-up granted the rope doesn't get pinched by the turnbuckle and the steel twist link. Might not be a complete PITA to install on the camper either...

 

[Wallowa]

DonC I'd be interested in link to what you buy? My camper is off my truck right now but putting back on soon... I'd like a warm fuzzy of not worrying about turnbuckles. I actually was not worried until this thread

Internet will do that to you. Mixed blessing; information and misconceptions all co-mingled. I guess for me I take what squares with my common sense and experience and try not to get swept up in the tide of "the sky is falling".

Turnbuckles are essential to the well being of you and your camper. But it is not rocket science or advanced engineering.

Just my take and of course I could be wrong..

Phil

Ps...My climbing was decades ago and I do not remember "Dog Bones" but the idea as a back-up redundant retention system is very cool. I only have a single link on each turnbuckle and will devise an other attachment for the rope/webbing directly to the eye-bolts. Thanks for concept! Simple and easy to put in place.

 

[ntsqd]

Standard Engineering practice is yield strength is at least 2 times the expected max load. This is called the "Factor of Safety".

A decent Rule of Thumb for inertia-induced loads is 3 times the max static load.

So as an example a 1500 lbs loaded camper divided by 4 turn-buckles = 375 lbs per corner (assumes uniform weight distribution)

375 lbs times 2 (Factor of Safety) = 750 lbs.

750 lbs. times 3 (Inertial Load Factor) = 2250 lbs

For this example the minimum strength rating for each of it's turn-buckles needs to be at least 2250 lbs.

Higher quality rigging hardware will have "WLL" ratings. That is the "Working Load Limit". This means that the manufacturer has calculated and tested the actual breaking strength of their product and then applied a rating that keeps it (& you) safe. Effectively they have included a Factor of Safety in their rating. It does you no good to try to figure out what that factor is, use their rating as the yield strength in your calcs.

We have two of the links like what Bill H posted in our rear turn-buckle system. I would not want the type that don't lock closed. Not from a "might accidentally pop open" concern, but from a strength consideration. I know that the better of the snap links have an interlocking feature between the gate and the loop, but there has to be clearance between those parts for it to open which means that the opposite side already has been yielded a little before that clearance goes to zero and starts to take up some of the load.

Climbing gear should be left to climbers. It typically does not do well when exposed to sunlight, even incidentally, for any length of time. There are slings used by riggers etc. but to my knowledge they are too big for this use. They also have a finite life-span.

 

[kmacafee]

The Dynex slings and dog bones for climbing applications are indeed very strong, but they are designed to used with a shock absorbing dynamic climbing rope. The do not respond well to what climbers call "static shock loading" which would probably happen in a camper to truck application, and any sort of knot or hitch will weaken them considerably too. Using a piece of actual dynamic climbing rope would be much stronger, but it derives it's strength from stretching and would not secure the camper tight to the truck due to this stretch, but it would work as a back-up to a failed turnbuckle well if it was tied to the anchor points correctly. I think this set-up (with an appropriate turnbuckle) would be a good backed up set-up granted the rope doesn't get pinched by the turnbuckle and the steel twist link. Might not be a complete PITA to install on the camper either...

This is helpful. But when I look at the numbers, each one of those slings is rated at 25 kilonewtons or about 5000 pounds. If there is one at each corner, I would think that even with static shock loading, an 850 pound camper would fall well within any limits for failure, wouldnt it? They have to be stronger than the lightweight turnbuckles supplied by FWC and shown in your photo.

I am not an engineer but did a little research on some climbing and caving sites. In one example, they calculated a 220 pound weight dropped 6 feet would generate about 1000 pounds of force. In another test, a 550 pound weight dropped 4 feet generated about 2000 pds of force. The camper would not drop but bounce up which might be equivalent stress. Given that the sling would be much less than 2 feet long at each corner and the camper would probably only bounce a few inches, my non-engineer brain tells me that the sling would still be more than strong enough compared with the turnbuckles.

Does that make sense? Am I missing something? I am totally open to being proven wrong but the climbing sling seems to offer a strong and simple solution to the turnbuckle conundrum.

 

[Wallowa]

Thom,

Interesting engineering info...BUT what is the "yield strength' of the turnbuckles supplied by FWC?

Are they all one strength regardless of the size/mass of the camper?

Without knowing the strength of the tie down components we purchased from FWC and trying to determine if we need to change our rigging is useless and a total WAG. Plus the loading on the four tie downs will not be uniform either with a static or dynamic load.

I agree with having a tie down system that exceeds the strength required to keep the camper firmly in place and like most of us, we can only guess at what is needed to accomplish that with the stock FWC turnbuckles. Beyond engineering calculations the "proof of the pudding is in the eating" and we can empirically determine what is needed from our own experiences and those of others with the same existing tie down systems.

While climbing gear is for climbing the carabiners/snap links are used in climbing as well as the ropes and webbing mentioned. I agree about UV degrading synthetic materials like ropes or webbing. But my turnbuckles and attachment points inside the bed are 100% shaded from UV.

Phil

 

[WyoIDI]

I agree, most climbing hardware should be left to climbing, but items such as steel twist links are used in climbing anchors everywhere as well as some of our campers. Heck, I even use steel bolt hangers designed for climbing applications for anchor points on my camper and my truck bed because I feel they greatly reduce the leverage that seems to rip out eye bolts on some campers but thats a different can o' worms. I'm not an engineer, I'm a climbing guide who has trusted my life to these items in the field many many times and that's where my opinions stem from. I know dynex is an incredibly strong, useful material that I use all the time, but it is also very prone to abrasion and it's big no-no to use them in situations where they can be subjected to a sudden dynamic force with out a shock absorbing element in the system(dynamic climbing rope). I'm also not sure if you could get a sling tight enough to hold the camper down without twisting it or using a hitch which also reduces in strength. Some of the stronger steel turnbuckles that have been mentioned are a superior alternative in, once again, my opinion.

That's why I think a high strength turnbuckle, backed up with a dynamic (shock absorbing) rope as a back-up would be a good set-up. In situations where the camper was subjected to a sudden jolt that broke the turnbuckles and the camper came loose, this would work well as a back up. Or just having a separate tether that can't rattle loose for a back up would be useful too. Dynamic climbing ropes are very strong and have a protective sheath that protects in from some abrasion and some UV(which it would never see under a camper). In a truly redundant system, the rope back-up would be on a separate anchor system in case the tie-down points failed but that would get a little excessive in a camper application.

Another thing to consider is that any synthetic material is very susceptible to failure if it's exposed to oil or gas or anything corrosive that might lurk in a truck bed. I'm certainly not trying to prove anyone wrong or say someones system is dangerous, I'm just sharing my experience with climbing hardware to hopefully help someone out or throw some ideas out there. My system is definitely much different from the FWC factory system and It's worked very well for me and I took the risk going that route. I definitely don't think it's the perfect solution, just an improvement over the stock system. Good discussion, thanks

Jon

 

[kmacafee]

Thanks. Very Helpful.

 

[Wallowa]

Jon,

Spot on. Thanks to all on this thread; some good ideas and systems to ponder..

Last time I will ask: "Does anyone know the strength rating of the turnbuckles currently supplied by FWC"?

Thanks!

Phil

 

[iowahiker]

Good discussion... Just back yesterday from our initial tour with our new Hawk and F-150. Thirteen days and 1,600 miles from Sac to Death Valley, other Mojave locations and the Carrizo Plain. I'd guess we did about 200 miles of dirt roads, some of them quite washboarded (I've never seen the Harry Wade so rough.) We also had a couple of sharp maneuvers to avoid the inevitable I-5 idjits plus a fairly good whoop-de-doo behind Red Mountain.

I spent a fair amount of time with turnbuckle maintenance which I suppose is to be expected on an initial trip. I tightened a couple of times on the I-5 drive south and then each night or morning in camp. Until the last couple of days, each turnbuckle yielded an eighth to a quarter turn daily. It got to the point where I thought it might be useful to have a permanent "wrench" installed in the slot of each turnbuckle rather than moving one from port to port while trying not to drop it in the bed of the truck. I used a steel, flat, 6" bottle opener.

Now I am concerned a bit about overtightening after reading this discussion but the access is so awkward that it is pretty difficult to put a real hard turn on the hardware with one hand while lying on the floor. Strangely my turnbuckles are installed in a left-tighty configuration which confused me at first. At least they were all the same. I hope to figure out more at the upcoming NorCal campout and whether an upgrade is appropriate.

Our turnbuckles needed repeated tightening too. We shimmed the camper at the wheel wells and slid the camper forward to get positive front wall contact and do not tighten anymore. My opinion is turnbuckles that do not stay tight is a sign the camper is moving around. The mostly vertical orientation makes for poor turnbuckle control of lateral motion. Bed mats and other friction surfaces are another option to control camper movement. Also, some of the force analysis shown in this thread is way off of DOT cargo tie down requirements. We have 350 pound FWC OEM turnbuckles plus a 800 pound safety chain at each corner.

Also, I feel the open hook type turnbuckle is a poor choice for holding a camper unless the turnbuckle has a automatic (spring) tightener.

 

[daverave]

Our turnbuckles needed repeated tightening too. We shimmed the camper at the wheel wells and slid the camper forward to get positive front wall contact and do not tighten anymore. My opinion is turnbuckles that do not stay tight is a sign the camper is moving around. The mostly vertical orientation makes for poor turnbuckle control of lateral motion. Bed mats and other friction surfaces are another option to control camper movement. Also, some of the force analysis shown in this thread is way off of DOT cargo tie down requirements. We have 350 pound FWC OEM turnbuckles plus a 800 pound safety chain at each corner.

Also, I feel the open hook type turnbuckle is a poor choice for holding a camper unless the turnbuckle has a automatic (spring) tightener.

Interesting to me that such a basic and essential camper attachment thread can lie dormant for 14 months and then have a noob like myself ask a simple question which generates a couple of more pages of responses. There is obviously a lot of latitude in how to best attach the thing!

I like your idea, iowahiker, about trying to reduce lateral movement by pushing forward to the front wall and eliminate one direction of lateral movement. I was actually surprised that the space was there after FWC installation. We do have a rubber bed mat but others here seem to think that it may lead to loosening! I also think that some redundancy, aka belts and suspenders, would be a smart approach.

 

[ntsqd]

What the rating of the supplied turn-buckles might be is not worth worrying about since they're not being used. I realize that they might offer some idea of what their replacements should be rated for if that info were readily available, but as it is not I don't think it worth the trouble of tracking it down.

Weigh your truck without the camper & weigh it again with the the camper loaded for a trip. The difference is the weight that matters to the selection of the turn-buckles. Part of the reason for Factors of Safety is to allow for errors in assumptions like just how well distributed is the weight? If you really want to know what each corner weighs you can make up a tool like this:

For getting the corner weights of a vehicle it is used with a beam torque wrench like this:

For camper corner weights some mods may be required. The leverage ratio is 10:1, so 100 ft-lbs on the wrench would be 1000 lbs lifted.

Use forged eye-bolts or eye-nuts (I get hardware like that from McMaster-Carr) with Grade 8 nuts, bolts and washers for any added-on attachment points. I pull the turn-buckles up snug, not tight. After a couple trips they've quit loosening, though I do check them periodically.

Our camper danced around in the bare bed so I added a ~3/8" thick rubber bed mat. The camper doesn't move around much at all. I wonder if those saying the mat causes loosening are speaking from conjecture or experience because our experience has been exactly to the contrary.

 

[Wallowa]

Coefficient of friction is critical on anything in or on the bed of the truck when you insert the camper. I removed a great "BedRug" and went with the existing Line-X bed surface. Line-X is a good friction surface that the Hawk will not easily slide on. The BedRug was a wonderful product but it will retain some water even though non-absorbent, had a lower coefficient of friction than the Line-X and though trivial it added a midget more height to the camper thereby raising the CG.

If your rubber mat is "sticky" and will inhibit movement of the camper inside the truck bed then that is a good thing. If it presents a slick surface [think also about when it is wet] then not so good.

The 2 rubber bumpers on the front bottom of our Hawk rest against the front of the truck bed and the clearance between the wheel wells is at most 1/2" on either side which does not provide a lot of "wiggle room" for the Hawk in our '05 Tundra.

In passing, the angle of our turnbuckles [fore and aft] between the truck bed and camper eye-bolts is approx 45 degrees; definitely not vertical.


Phil

 

[Wallowa]

ntsqd,

Wow! A lot of work to determine the corner weights! Impressive though.

Question. I think I understand your first paragraph and that you don't the FWC supplied turnbuckles. But after going to all this effort to determine the needed strength for turnbuckles on your rig, how did you determine that the OEM FWC turnbuckles were not strong enough without knowing how strong they were?

Also not sure what the difference between snug and tight is. In tightening mine it was always a question of "gosh is that enough or too much"?

Phil

 

[kmacafee]

Jon,

Spot on. Thanks to all on this thread; some good ideas and systems to ponder..

Last time I will ask: "Does anyone know the strength rating of the turnbuckles currently supplied by FWC"?

Thanks!

Phil

The ones I got with the camper and supplied from FWC (2012) have aluminum bodies with steel threaded hooks. There are no markings anywhere on them at all and look like the ones in the photo in post #124.

Anything similar I can find at places like McMaster Carr, Grainger, Home Depot advertise a load limit of 100 pounds or less (usually 45-60). Unless FWC is sourcing something custom (and they may be), what they supply is wholly inadequate from the start.

I have since replaced them with forged turnbuckles with clevis ends rated to 800 pounds each and use a snap link to connect them to the truck and camper. They do still come loose but the camper won't come off the back of the truck.

 

[Bombsight]

So which of these would be the minimum required? .... http://www.westechrigging.com/rigging-hardware-turnbuckles.html

... and what type is best?

 

[carld]

Ok, now I'm not a mechanical, but I am a climber and an engineer. First of all climbing slings are tested for blunt holding force, 22 kN is 5000 lbs, remember F=ma. Climbing ropes are meant to stretch, but only when there is sufficient length of rope extended to absorb the force, small parts or a rope have very little absorption capability. So, what is the problem? The system is only as good as the weakest link. If you make the turnbuckles rock solid then the camper connection or the truck bed is the next thing to blow, and that can be expensive. So, what is needed is something to absorb the instantaneous force and dissipate some of the peak energy (force x time maybe as little as milli-seconds). Currently the hook or un-welded eye connections on the turnbuckles are weak. So on a continuous bumpy road that instantaneous maximum is exceeded again and again until the woop-ti-do where everything fails. Torklift solves this problem by adding a spring to dissipate some of the energy, but with a 6" space it makes it difficult. A spring by itself reduces the peaks but also friction is needed to dissipate the energy. So, by connecting the camper to the truck with strong webbing with over 5000 lbs of strength is sufficient to prevent the turnbuckle failure, but then what's next. I did some experiments using some 16" climbing slings. With two raps of the double sling, that's like 20000 lbs of holding power and connecting the loop with a stainless steel quick link they loosely connect the camper to the truck, maybe and inch or two of slack. What is needed is a way to tighten the connection. I'm thinking that the eye bolt connection to the truck bed should be free turning. Then a self, locking nut is used to tighten the eye bolt, imagine using a drill driver set to a fixed torque tightening the nut from the bottom of the bed. First off the sling twits until there is sufficient torque to tighten the nut and the drill to maximum torque. Now the sling has twisted 2 or three times and the system is supplying a fixed holding force. When more force is encountered, the slings tend to untwist evening out and dissipating the energy.

Just a though, I think it could solve the problem.

 

[SunMan]

Last time I will ask: "Does anyone know the strength rating of the turnbuckles currently supplied by FWC"?


Phil

My scientific rating is "strong as hell"... At least strong enough to pull my chintzy Toyota bed corner up sardine can style vice breaking.