Canadian Disco 2 Build
- Thread starter R_Lefebvre
- Start date
R_Lefebvre
Expedition Leader
You are right about one thing, people who come along this post will have to figure out for themselves who to listen to.
So, are you working with the SCCA to have all those dangerous welded roll cages banned, and everybody switch over to bolt in cages? Oh wait... those have welds too. How about the NHTSA, have you got a bug in their ear about all those welded seat frames? How about the B-pillars to which the seatbelts are bolted, which are welded to the rest of the chassis? What about your consultations with the FAA with all those welded landing gears?
Just because YOU don't know how to properly weld something, or determine how somebody else might properly weld something, does not mean that nobody else can.
xwerx
Observer
I would inspect the recovery point on their vehicle, and if I did not like the looks of it in any way I would find an alternate point to attach to. I don't trust just anyone in their welding ability. I would check both welded and bolted recovery points, someone could have cut corners and used grade 2 bolts..
If its welded properly it should be a non issue. The company I work for chooses to weld all of our components instead of bolting them together (like our competition does), which has to count for something since we are the largest supplier of 5th wheels to the OEM heavy truck market.
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Alaska Mike
ExPo Moderator/Eye Candy
Sombody better tell Ike:
And Tomken Machine:
And Warn:
...and just about every manufacturer of bumpers that offer some sort of extraction point.
We're just going to have to agree to disagree on this one. Let's move on...
Root Moose
Expedition Leader
Regarding the aftermarket bumpers above...
Do they use the shackle points as the long slides that get bolted to the frame rail? Are they the main longitudinal structure of the bumper?
I made a bumper along these lines. The piece that holds the D ring slides into or along side the frame rail and is bolted. It holds the bumper structure and there are no recovery loads being resisted by my non-certified, amateur welds.
$0.02
Do they use the shackle points as the long slides that get bolted to the frame rail? Are they the main longitudinal structure of the bumper?
I made a bumper along these lines. The piece that holds the D ring slides into or along side the frame rail and is bolted. It holds the bumper structure and there are no recovery loads being resisted by my non-certified, amateur welds.
$0.02
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Alaska Mike
ExPo Moderator/Eye Candy
Some do, some don't. Most aftermarket recovery points I've seen don't, and are an option to a standard bumper. I like your design, but it may be impractical for a manufacturer that ships their products. Those solid blocks of steel will nearly double the weight of their finished product and drive up the price.
For rear bumpers (so we're talking apples to apples), most manufacturers use centered 2" receiver hitches as the recovery point. Warn, among others, advertises them as such- but won't rate them for towing.
In Pangolin's case, here is the recovery point pictured as an option:
Here is essentially the same bumper as I pictured before without the shackle brackets:
The mounting system to the frame is independent of the shackle bracket. I'd trust their bumpers, and plan on getting a front one (with shackle brackets and 8274 mounts) with some rock sliders as soon as I can. They also have bolt-on recovery point options, if you're so inclined.
Up here we do a lot of recoveries using winches, straps, and all sorts of methods. Due to the very severe nature of the recoveries, some of them can be a tad "assertive". I've seen bumpers ripped off the fronts of Cherokees (welds held, bolts and unibody didn't) and tow hooks/shackle brackets almost come loose because of over- or under-torqued hardware. I have yet to see a properly welded recovery point fail. Maybe I've been lucky, but my winch has seen more use in a month than most people here see in a lifetime.
My Jeep has bolted on recovery points from a military 1-ton vehicle. That was more of a point of convenience than anything else when I was building my bumpers.
For rear bumpers (so we're talking apples to apples), most manufacturers use centered 2" receiver hitches as the recovery point. Warn, among others, advertises them as such- but won't rate them for towing.
In Pangolin's case, here is the recovery point pictured as an option:
Here is essentially the same bumper as I pictured before without the shackle brackets:
The mounting system to the frame is independent of the shackle bracket. I'd trust their bumpers, and plan on getting a front one (with shackle brackets and 8274 mounts) with some rock sliders as soon as I can. They also have bolt-on recovery point options, if you're so inclined.
Up here we do a lot of recoveries using winches, straps, and all sorts of methods. Due to the very severe nature of the recoveries, some of them can be a tad "assertive". I've seen bumpers ripped off the fronts of Cherokees (welds held, bolts and unibody didn't) and tow hooks/shackle brackets almost come loose because of over- or under-torqued hardware. I have yet to see a properly welded recovery point fail. Maybe I've been lucky, but my winch has seen more use in a month than most people here see in a lifetime.
My Jeep has bolted on recovery points from a military 1-ton vehicle. That was more of a point of convenience than anything else when I was building my bumpers.
M
Murphey
Guest
I think you summed it up nicely. There is no way in the world you can look at a weld and determine it safe. I've been welding for 15+ years; I've seen some crappy welds that looked pretty. I've also seen some mild steel bumpers paper thin only to be boxed so you could not directly see the bumper thickness. Point being you cannot accurately inspect a weld on the trail.
But you can tell the difference between grade-2, grade-5, grade-8, and L9 bolts with just a quick glance. You can see if the bolts are tight or stretched. You can see if there is a backing plate.
Antichrist
Expedition Leader
LOL Yeah, like the Baltimore club form shown. By that wording someone could show up with their recovery point bolted on with 1/4" grade 8 bolts and be admitted, while someone with 8" of 1/4" fillet welded all around with E11018 and stress relieved would be turned away.
And someone showing up with an RTE bumper would be turned away.
My guess at their intent, given that so many aftermarket bumper mfg use welded recovery points, is that they meant to say, "If a recovery point is bolted on, it must be with at least grade 8 hardware.
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R_Lefebvre
Expedition Leader
If, as is often the case, the installer uses an impact gun to install the bolt, it's very easy to stretch the bolt past it's yield point. At this point, it starts to neck down, and the strength is reduced drastically. Yet, this partially failed bolt cannot be detected unless you dissassemble the joint. Installers can and do stretch bolts even using a wrench. The proper install torque for a Grade 5 1/2" UNC bolt is only 82 ft/lbs. But that's assuming perfectly dry. If there is any lube or anti-seize on the bolt, the install torque is reduced to 41 ft/lbs. This is well below what most people assume.
After the bolt has been stretched during install, it's undetectable, and it's a ticking bomb just waiting to go off. Much the same way as a bad weld.
After the bolt has been stretched during install, it's undetectable, and it's a ticking bomb just waiting to go off. Much the same way as a bad weld.
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Antichrist
Expedition Leader
I wonder if the people who look at a bolted on recovery point and see a grade 8 head, also check the back side to make sure the nut wasn't welded on to the base material. If it is, you effectively have a grade 2 or, at best, Grade 5 nut on a grade 8 bolt and rather than the bolt stretching before failure, you're more likely to just have the threads strip out.
There are just too many variables in an installation to categorically say one is always better than the other.
There are just too many variables in an installation to categorically say one is always better than the other.
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This debate will never end.
For people to just say all welded recovery points are wrong is just really short sighted. There are plenty of welded recovery points that far exceed the loads they will ever see in even the hardest recovery.
This debate has happened all over the web in the past and will continue in the future. Just looking at something and making a declaration of its fitness for a purpose is also not the best way to do things. So the people saying they can look at bolts and decide if they are up to the task are also making a statement based in something other then fact.
One such debate took place over this recovery point welded onto a very light, very strong aftermarket bumper.
People made claims that this recovery point would fail when used as a recovery point on a disco because it was welded and because of the direction of the forces during the recovery. Having access to some great testing and design recources I thought it was only fair to put it to the test....figuratively speaking. the results showed that the welded on or actually through in this case recovery point would not be torn off and that the metal it was welded to would deform and fail prior to the recovery point tearing off the plate.
http://www.expeditionportal.com/forum/attachment.php?attachmentid=36053&stc=1&d=1262233636
by looking at this image you see where the stress is focused.
http://www.expeditionportal.com/forum/attachment.php?attachmentid=36054&stc=1&d=1262233889
This image shows how the actual plate deforms from the forces. Keep in mind the amount of deformation is exagerated in the software to make reading the results easier. From the numbers the engineer that ran these for me said that the part would not have had any visual result from even 20000 lbs of force as I recall.
People that want to attack any welded recovery point in most cases are commenting based on information that is more based in policy then structural engineering and this should be kept in mind when looking at equipment you intend to use or purchase.
For people to just say all welded recovery points are wrong is just really short sighted. There are plenty of welded recovery points that far exceed the loads they will ever see in even the hardest recovery.
This debate has happened all over the web in the past and will continue in the future. Just looking at something and making a declaration of its fitness for a purpose is also not the best way to do things. So the people saying they can look at bolts and decide if they are up to the task are also making a statement based in something other then fact.
One such debate took place over this recovery point welded onto a very light, very strong aftermarket bumper.
People made claims that this recovery point would fail when used as a recovery point on a disco because it was welded and because of the direction of the forces during the recovery. Having access to some great testing and design recources I thought it was only fair to put it to the test....figuratively speaking. the results showed that the welded on or actually through in this case recovery point would not be torn off and that the metal it was welded to would deform and fail prior to the recovery point tearing off the plate.
http://www.expeditionportal.com/forum/attachment.php?attachmentid=36053&stc=1&d=1262233636
by looking at this image you see where the stress is focused.
http://www.expeditionportal.com/forum/attachment.php?attachmentid=36054&stc=1&d=1262233889
This image shows how the actual plate deforms from the forces. Keep in mind the amount of deformation is exagerated in the software to make reading the results easier. From the numbers the engineer that ran these for me said that the part would not have had any visual result from even 20000 lbs of force as I recall.
People that want to attack any welded recovery point in most cases are commenting based on information that is more based in policy then structural engineering and this should be kept in mind when looking at equipment you intend to use or purchase.
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Antichrist
Expedition Leader
You can't even easily look at a bolted connection and see that it is ok. One reason, as pointed out, is that even a grade 8 bolt can be over torqued during installation. Another is that I bet very few people, like the Baltimore club as an example, check the back side of the connection. If the nut was welded to the base metal (as someone might do if clearances are close and you can't access the nut easily with the bumper installed) then you're effectively using a grade 2 or 5 nut on a grade 8 bolt and the threads are likely to strip.
That would certainly be an even better attachment. The tab inserted in a hole in the bumper with a full circumference cap weld on the back side, and a fillet all around on the outside.
There are just too many variables to say all welded, or all bolted, attachments are bad. Or good even.
It was nice to see the pdf show the stresses expected to be exactly where I thought they would be on a forward pull.
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R_Lefebvre
Expedition Leader
Ok, so back to work. Had to replace the head gasket on my compressor for some reason.
It's actually sorta funny... have a little "studio" set up in the garage trying to do this. 1000W of lighting. I was having trouble with shallow depth of field, so I have to close the aperture to f13, but boost it up to 1600 ISO so I can still shoot at 1/60. I suppose I could use a tripod...
Welded the brackets on:
It's actually sorta funny... have a little "studio" set up in the garage trying to do this. 1000W of lighting. I was having trouble with shallow depth of field, so I have to close the aperture to f13, but boost it up to 1600 ISO so I can still shoot at 1/60. I suppose I could use a tripod...
Welded the brackets on:
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