So what do you guys think? Is 15 foot pounds (180 inch pounds) excessive? Or do you think that they should be holding the same torque as the bulkhead joints even though there is only one wall of thinner frame tubing between them and stripping.
There are of course plenty of posts on the forum on the torque setting for the bulkhead Rolok bolts, but as far as I can tell, there doesn't seem to be any reference to the vertical Roloks which hold the basement to the compartment dividers and walls. The bolts themselves are the same ones used for the bulkhead joint, with a few exceptions. However, the material that are providing the female threads have only one wall and is thinner than the bulkhead framing. I can tell you from experience, that the vertical roloks will likely strip before they reach the torque of the bulkhead joint which is about 20.8 foot pounds or 250 inch pounds of torque. I have settled on 15 foot pounds of torque for these as I believe that should be sufficient. That said, I would like some opinions on what the smart people on this forum think about this issue. I would bet my house that the bolts are not torqued when the coach is originally assembled at the factory, but rather driven in with an impact driver and then perhaps tested to see if they're holding a certain torque.... But I could be wrong ::)
Related to this issue, I have developed a technique for inserting square nuts into the compartment divider tubing that are in utility compartment, and in the fuel/ battery/propane compartments for the fasteners which are not making it to 15 foot-pounds before stripping. I will include a few pictures, because possibly some time in the future somebody will be able to utilize this method to help themselves. Basically, it involves tack welding a rod to a 5/16"-18 square nut and then inserting the nut down the tube until you get to the offending rolok. After the fastener is torqued, simply give a quick twist of the rod to break the weld and then you can extract the rod. I bend about an inch at the end of the rod away from the nut to a 90° to give so I can keep the flat of the nuts parallel to the flat of the tube once inserted. The 90° bend at the end of the rod also makes it easier to snap the tack weld off the nut when you're done. I did grind a little bit off of two opposing sides of the nut just to make them go down the tube a little easier. The picture shows the end fastener, which really doesn't require this technique because you can reach in there with a magnet or screwdriver and position the nut, but still serves to illustrate the principal. I was able to place a nut nearly to the center of the compartment with a 4 foot rod and get the rolok started successfully. Once done, these fasteners will torque practically to your hearts content. Of course once done, if you ever have to remove the bolt, it is possible that the nuts may not align properly when you go to put them back in and you may have to repeat this technique. There is a bit more to it and I would be happy to explain if anybody wants to know...
For the storage compartment walls, unfortunately this is not possible because the tubing isn't open on the end. For these, I have to do something similar to the standard bulkhead repair which is to drill a hole in fiberglass and putting a nut on the back side of the tubing, use a longer through bolt and then use a 2" plastic cap of some sort cover the hole. Fortunately, since these caps are inside the basement compartments, at least these caps do not have to be weather tight...
Thanks, Don
Thanks Don. Karma to you, I think you encouraged me to take some molding off and look more at an area that I treated with Por15. There is on my utility bay a short wall between the sewer drains and the hose reels. The base of that wall has rust that I ascribed to water in the past coming out of the water hose after use and it reeled back up. I may be wrong but seems reasonable assumption.
Is this an area similar to what you describe?
Thanks,
Mike. (Hope typing on this phone got close to what I wanted to say and I can get that karma thing done!)
Yes Michael, that is exactly the area that I'm talking about. These short walls, or as I've been calling them compartment dividers, are made out of three-quarter inch rectangular stock whereas the other walls that run the full-width of the basement are inch and a half square tubing. The bottom and top rectangular tubing on the short walls are open on the end under the trim. One issue with my basement fasteners is that they have been in and out many times in my bulkhead repair project. Though I was careful to never over tighten them while working on the project, just the fact of them going in and out couldn't have been good for the condition of the threads. Even so, on the end ones at least, it is fairly simple to insert a square nut from the end and have that added security. One point I should make is that if you tighten bolt down so that the nut is torqued, the original threads will be stripped. Since these outside fasteners are easy to get at, I am not concerned about that I just went ahead and stripped them to ensure that the ends of the short wall are well secured and supporting the basement floor, but that is just me. Through bolting is always a possibility here, and would be easy for me to do while the tanks are out but much more difficult while they are in place. My particular technique would work anytime regardless if the tanks are in or out. One other thing I should mention is that the tanks should probably be emptied before messing with these fasteners for obvious reasons! In your case, I'm not sure I would mess with it unless those fasteners were not doing their job. In my case, I feel better knowing that there are quite a few of these fasteners with nuts providing the holding power, rather than the thin gauge tubing whose wall thickness may be compromised by rust.
Don
Don,
I will not voice an opinion on torque-- I have never "dissected" that area.
But, when I do a mechanical inspection, I absolutely do look for evidence of rust jacking on those vertical bulkhead attachments. Normally rust jacking is an indication of weakened box beams. This is easily identified by the bulge in the fg floor to the coach along the lines of the compromised beams.
And, here, we "round up the usual suspects"-- wet bay leaks, water heater leaks (on some models where it is in passenger's side of the wet bay, leaking batteries (some models), etc. Many of these issues are evident by lowering the sewer hose door and observing rust jacking and even complete rust-through.
If no rust jacking, I have never heard of issues with the vertical bulkheads.
Brett
That's all well and good Brett and I do appreciate the response to my post. I'm not really looking for somebody to go out on a limb and give me a recommendation that I can follow and if something bad happens, put the blame on them... Just looking for some comments from the smart folks on this forum about my line of reasoning regarding the torque specs of the vertical bulkhead roloks. Conventional torque charts say that for a 5/16"–18 grade 5 steel screws, installation torque should generally be around 17 foot-pounds, or 204 inch-pounds. As it is, using my arbitrary 15 foot-pound standard for installation, I ended up stripping the holes and putting nuts on 13 of the 15 fasteners on the front short bulkhead between the fuel tank and the battery/Propane and I think about 8 in the rear Utility compartment short bulkhead divider/partition/wall/ or whatever you would want to call it. Once I put nuts on them, I'm torquing them to 220 inch-pounds (18.3 foot pounds) and marking the ones that are backed by nuts so that I don't strip the other ones in the future. I will also make notes in the documentation that will stay in the coach. Since I am using an 1/8" inch stainless steel flat stock underneath the bolt heads, I feel pretty safe in terms of not crushing the tubing.
In short, no one has to take responsibility for any actions that I would take based upon the opinions rendered in this forum. I am just saying... :D
I will say that there really wasn't any evidence of rust jacking underneath the compartments bulkhead walls visible from underneath the coach, I believe the holes are mainly stripping as result of the fact that once installed at the factory, the connection between fastener and the female threads will never be as strong with this thin material during subsequent reinstallation's. Unfortunately, given the scope of this project, there really wasn't any alternative to removing and reinstalling the basement roloks. Since I bought 40 new roloks originally and used 18 of them on the front bulkhead, I kept only the best of the ones I had removed and used the new ones wherever possible.
Don
When we welded a handle on a nut we called it a lollipop. The strip out torque for a 5/16" thread rolling screw in structural steel with a wall thickness of .125" is 175-190 inch LBS in .250" wall it's 350-400 inch LBS.So I think for .125" wall torque should be 80 inch LBs and for .250" wall 200 inch Lbs.Gam
Good show, Don. This forum is simply sharing information and should never be construed as a guarentee. On the use of nuts, remember that the stripping force on the threads is dependent on the quality of the nuts as well as the material they're made from. A cheap 1018 nut will stripo much easier than a grade 5 or grade 8. A cheap nut will have 50-60% thread contact while a good grade (don't read "good" as grade5 or grade 8) will have 65-75% thread contact. I don't think you can buy a higher contact percentage over the counter. Probably could have someone make some at a price but also probably not necessary. Industry simply adds more fasteners rather than upgrade the nuts and bolts. Not always easily done
Thanks Gam,
Edit: I just reread your post Gam, and I guess I would have to amend the torque settings from 87 to 95 inch pounds down to about 48 to 56 inch pounds for the thinner gauge stock. Hmm... Based upon my feel, that just doesn't seem like enough clamping force to help support the weight of that basement structure which includes the fuel tank, house batteries, and propane tank on one end (potentially close to 2,000 pounds), and waste and freshwater tanks on the other (I would guess around 1,000 pounds with full fresh but possibly even more if you were to take on more fresh before dumping the waste tanks for some reason). I think that as originally assembled, they must have had the basement clamped in place and been using the back side of the tubing being fastened and cutting threads in both tubing walls on the two sides of the joint simultaneously... hard to describe, but it fits with what I observed when I had the vertical fasteners out. Anyway, as it turned out, I'm going to be quite sure that my basement will stay attached to the rest of the coach even when I fill it with all my gold bullion! ;D
I believe most of the tubing, other than the transverse bulkhead square tubing that bolts to the angle iron of the bulkhead joints, is 16 gauge or thereabouts. Therefore using the figures that you give, the proper torque for installation of the vertical basement roloks for the short compartment divider walls should have been around 87 to 95 inch-pounds. It is possible that the transverse tubing of the full compartment walls is .125" as only a total of three of those stripped at 17 foot pounds so I settled for 16 foot pounds for those (the stripped ones being replaced by the through bolt method), but the rectangular 3/4"X1.5" tubing of short walls where I can see the open ends is definitely not. The exception is the part you can see in the photo which is a piece that I welded in replacing a rusted out corner that was all but gone. I am including a picture of three gauges of tubing for reference. Top to bottom they are 16 Gauge (about 1/16") 14 Gauge (about 5/64"), and 11 gauge (1/8" or .125"). The quarter inch thick nuts have so much more contact area because of the thickness easily hold at 220 inch pounds with no exceptions. So I am glad to have nuts on the vast majority of the connections for that thinner tubing.
Don