> ...But, when found, both the cap and the iron are always in good shape.
That's really interesting. I'm sure it is a testament to the diverse sub-soil conditions that we have across the continent.
There is an area we call the "Great Salt Plains" up in NW Oklahoma that is an approximately 50 sq. mile salt flat marsh with a shallow and seasonal lake. The original (1870-1900) GLO surveys merely terminated their surveys as soon as they hit the marsh. Fast forward to WWII and the area was used as aerial bombing training and the gov't. finally completed the rectangular survey.
Their monuments were aluminum (they needed the brass for ordnance) caps with the stems pressed into 1" steel pipes. Although their chain and transit surveys were of the highest order (amazingly accurate), the only thing left of the monuments is usually some white gooey paste for the aluminum with a shaft of ferrous rust. Determining the corner's location usually requires digging preciously slow with a small mason's trowel. Near the borders where the soil is actually fairly dry most of the time, the aluminum caps are still almost non-existent, with possibly only a stub of a pipe remaining. I've always thought this was due to the salinity. In hindsight, they probably should have continued their use of native stone. 😉
> There was one outfit here in the PDX area that used aluminum caps as far back as the late 60's. There was no plastic liner on these caps, they simply hammered them on to the top of the iron rod. When you find them today the cap is usually pretty loose on the rod and the act of digging them up often separates the cap from the rod. But, when found, both the cap and the iron are always in good shape.
The weak link in the aluminum-capped rebar monument in the parts of Texas where I've surveyed most, i.e. Central and West Texas, is the shape of the end of the rebar that the cap got pounded onto. Typically, they weren't tapered at all and the ends of the bar were unprotected when driven, so burrs and mushrooming were common. Both tended to work against getting the cap firmly fixed to the rod.
My guess is they were probably loose a year after having been set. I'm still wondering how kneadable epoxy would work to rehab a loose aluminum cap.
> ...I'm still wondering how kneadable epoxy would work to rehab a loose aluminum cap.
I'm sure it would probably work well, Kent. The stuff I'm most familiar with is JB Weld in a putty form, sold at the automotive stores. I have a motorcycle with a stripped exhaust pipe mounting stud that was epoxied in place into a cast iron head many years ago. It is still in place and I expect it will outlive me. There are a number of putty epoxies on the market for apps other than automotive.
You should give it a try and give us a report. At least a controlled attempt to sit on your workbench so you could mess with it over the years to see if there are any drawbacks.
> My guess is they were probably loose a year after having been set. I'm still wondering how kneadable epoxy would work to rehab a loose aluminum cap.
I'm thinking that using a pair of vice grips to deform the cap flange onto the burred iron rod would hold the cap on, although perhaps not snug. A plier like device built for the purpose of crimping the cap onto the rod probably could do it.
> You should give it a try and give us a report. At least a controlled attempt to sit on your workbench so you could mess with it over the years to see if there are any drawbacks.
That's for more patient folks. I think that the nature of the thing is that if you stick one on and its still stuck on after going through a year of Texas weather, it should be good for the long haul.
> > My guess is they were probably loose a year after having been set. I'm still wondering how kneadable epoxy would work to rehab a loose aluminum cap.
> I'm thinking that using a pair of vice grips to deform the cap flange onto the burred iron rod would hold the cap on, although perhaps not snuggly.
At one time, I was thinking about a crimping tool to fix the cap onto the rod.
> At one time, I was thinking about a swedging tool that would crimp the cap onto the rod.
I was editing as you posted that.
we use a rasp, it will take off the burrs pretty quick, but if it's mushroomed then it's sometimes best to use a saw and file, many caps are loose because of mushroomed or burred rebars, we have ours beveled on the cap end and pointed on the bottom when we order them.
> we use a rasp, it will take off the burrs pretty quick, but if it's mushroomed then it's sometimes best to use a saw and file, many caps are loose because of mushroomed or burred rebars, we have ours beveled on the cap end and pointed on the bottom when we order them.
I've found that the rebar drive caps that Surv-Kap sells completely solve both the problem of burrs and mushrooming. The only thing I worry about are bars that have longitudinal ribs that stick out too far. Those have to be either ground down or (my method) just beaten down with a framing hammer, laying the bar on a small sledge as an anvil.
http://www.surv-kap.com/Survey-Tools/Rebar-Drivers
I have my assistant grind bevels on all of my rebars when he has some time to fill
> I have my assistant grind bevels on all of my rebars when he has some time to fill
I did that once upon a time and found that just hammering the longitudinal ribs before setting and using a rebar driver worked pretty much just as well. It's much more convenient when you're field-cutting bars to length, too.
I have gone to using the same aluminum ONLY caps you use with the similar 5/8" rebar (State Requirement although not many actually use it). They have worked well as long as we use the re-bar protector while driving the re-bar.
I use the aluminum caps with plastic insert. One thing I don't like is the ease that you can pull them off. With pliers or a vise grip you can jerk them right off. You could probably pull them off with your hand. In my climate/soil conditions I haven't seen them degrade. Time will tell. I have seen a lot of plastic caps chewed up by animals. So the aluminum with insert is an upgrade from plastic but way below brass/bronze which few clients will pay for.
Somebody should make a plastic cap like the Morsse but insert a brass washer that can be stamped in the top.
I haven't seen them degrade, but last year I ran across one that had been set circa 1991, so it had been in for about 23 years.
The plastic and aluminum were in good shape, but it had been set with the cap flush with the ground, and over the years frost had ratcheted the cap right off the rebar.
The rebar looked undisturbed, so I just tapped the cap back on and everything was good again.