Tuesday, March 5, 2019

Heat tape on the water tank outflow line

We went camping last November in the Eastern Sierra, not far from Tioga Pass.  The temps at night were around ten degrees, and (sure enough) the water system froze up during the first night.  As far as we could tell, the most vulnerable component was the thin vinyl tube leading from the fresh water tank into the trailer.  (The water tank itself is much less likely to freeze due to its "thermal mass" or "thermal inertia.") . All of our other water lines are inside the trailer.

Fortunately, the tube thawed during the next day.  That evening and all that night, I ran hot water into the tank every two hours, using my crude but effective recirculator:


Hot water recirculation technique


That method works, but it is not fun to get up out of a nice warm bed every two hours and stand there in the freezing dark for five minutes, while the hot water system warmed up the tank.  The temp INSIDE the trailer was hovering in the low 30s.  And this went on all week long.  A fun, exciting, adventurous trip, but not exactly relaxing.


So, what to do?  When we got home, a little googling uncovered this product:


Ultra Heat Self-Regulating Heat Cable


After discussing my project with the Ultra Heat tech staff, I decided to go ahead with this.  (The tech I spoke with was Eric -- really helpful!!) . I was particularly worried about how much juice this would draw, since we usually boondock, and I don't want to kill the batteries.  Eric told me that this thing is rated at 4 amps but usually draws much less (around 2 to 3).  It also turns itself off when the ambient temperature is in the mid to high 30s.


They shipped the cable to our house -- quick delivery.  As the product directions indicated, I cut it to length at a 45 degree angle and then put on a waterproof cap (included), which shrinks down when blasted with a heat gun.


Using cable ties, I then fastened the cable to the outflow tube.  It was a lot harder than it sounds, because (of course) all of the work has to be done under the trailer, upside down.  Worse yet, a good part of the tubing on my trailer is sandwiched between the top of the tank and the underside of the flooring in no man's land, so there is no way to see what you are doing.  My hands were jammed up into that tiny gap.


So for that part of the project, I bought this little video camera at Home Depot:


Mini video camera


It worked!   The lens snaked into the hidden area, and I could see the tubing and the cable ties on the video display.  (I have since used the camera on other projects around the house.)


Here is what the tube and cable looked like, after using the cable ties but before installing the insulation:




On the left side of that shot, note that I used several cable ties at the point where the tube attaches to the water tank, in an effort to get the cable to conform to the contours of the elbow joint.


And this is what it looks like after I covered it all up with pipe insulation, per the instructions from Ultra Heat -- in this shot, my finger is on the part of tube where it connects to the tank:





This cable runs on 12 volt power.  There are thin red and blue (positive and negative) wires running out of the end of the cable.  The folks at Ultra Heat told me that this device is ordinarily run out of the converter.  But when I checked, I could see that there were no extra fuse slots open on my converter.  (It's a very small trailer, and I am sure that the manufacturer used the smallest possible converter.)


Also, I wanted the ability to control the flow of current to the cable, rather than relying on its ability to self-regulate.  So, instead of running it to the converter, I powered it right from the battery.  I ran ten gauge wire to the two leads on the heat cable, using waterproof wire nuts (and some extra duct tape -- why not?).  I put ring terminals on the other end of the wires.  Those ring terminals fit onto the posts of the battery.  


The whole wire run is carefully secured under the trailer.  In the evening, when I want to hook up the heat cable, I put the rings over the posts.  In the morning, I remove the rings and tuck the wiring out of the way, inside the battery box.  


Since I have two 110 amp/hour batteries, I think I have plenty of power to handle this load.  (I try never to draw the batteries down below 12.1 volts. or 50 percent of capacity, or about 55 amp/hours.) . We recharge the batteries every day, either with our 120 watt portable solar panel or with the generator (seldom used).  (Note that I am assuming that the temps during the day will rise above freezing.  If not, the heat cable would have to run all day, and that would eventually deplete the battery, unless we have hookups.)


I checked with the Ultra Heat folks about my non-standard "no converter" arrangement.  They said it would work but that I was at risk of running my battery down.  But I figure that power has to come from somewhere, whether I power the cable through the converter or directly from the battery.  So the net draw should not change, either way.  

I thought that I would have to wait till our next cold weather high country camping trip to try this out, since the cable does not turn on until the temps drop into the low 30s.  But surprise!  We had a couple of nights in February where the temperature got down to 31 degrees in coastal Orange County, California, which almost never happens.  I ran outside in the early morning, hooked up to the battery, and used the ammeter function on my multimeter to see if the cable was on.  It was, and it was drawing just under two amps.


We've been hoping to go camping again to see if this device really does the job in real-world conditions.  Unfortunately, there has been so much snow this season that none of our usual high-altitude boondocking spots can be reached yet.  It will be May or June before the forest roads open up, and by then it will be too warm.  My guess is that we will not really need this thing until next autumn.


I will update this post after we do some more cold weather camping!



Wednesday, January 2, 2019

Gas can mount on top of spare tire

Transporting the gas can for the generator is a real pain.  It's only a gallon of gas, but it smells bad and it gets in the way.  We have been carrying it in a small crate in the cargo area of the truck, for lack of a better alternative.  There is no room on the tongue of the trailer, and there was no other place to put it.

So I figured that the spare tire is on the back of the trailer, quite securely -- maybe there is a way to piggyback off the spare somehow?

My first job was to check the bolts mounting the spare, which is on the back wall of the trailer.  I discovered the bolts were loose (!), and the mount was supported by little tee nuts inside the trailer, which were all stripped.  I think that the original design of this trailer was for light duty, which is not the way we treat this trailer -- we take it off-road (slowly) and on long trips at highway speeds on California's roughest freeways.  (I'm lookin' right at you, I-5.)

So I upgraded the bolts mounting the spare -- instead of quarter inch ordinary steel bolts into tee nuts with no washers, they are now three-eighths stainless steel with wide fender washers inside and out, into massive lock nuts, all anchored with quarter inch steel plates on the inside of the trailer, in order to spread the load over as many square inches as possible.  Now, instead of having the spare fall off, the whole back wall will give way at once.  (Joke.) 

This is what the upgraded beefy steel plates look like, on the inside of the back wall:




OK.  The spare is secure.  Next, how to mount the gas can on top of the spare?  The goals are safety, lack of vibration, and ease of use, in that order.  Even with the reinforced bolts, the spare still vibrates in response to an impact:




Over time, vibration can lead to materials fatigue and failure.  So the gas can mount, ideally, should dampen that vibration.

Here is what I came up with, in summary (with details to follow below): using the bolts from the spare tire mount as an anchor, I extended two half inch threaded rods up to the level of the rim of the tire.  I then mounted a horizontal platform on those two vertical rods.  A heavy milk crate is bolted to that platform.  The gas can goes in the milk crate.

Here is what the finished product looks like:




And now, the component steps.  This is the cross-bar anchored to the bolts supporting the spare tire mount -- I drilled holes in the angle bracket with my drill press to fit the bolts, and you can see the holes in the ends that will accept the vertical rods:



Here are the vertical rods rising from the cross-bar:



The platform will slide over those rods.  Note that there are pairs of nuts, tightly jammed together with lock washers, that will support one side of the platform.

Here is the spare tire on its mounting bracket, with the rods extending upward:



Here is the platform, mounted on the rods and resting on the top of the spare tire -- notice that on top of the platform there are nuts and washers holding the platform rigidly in place:



Here is a closer shot of the platform:



In that shot, at the very back of the platform, you can see the edge of an angle bracket extending across the back side.  The angle bracket is bolted to the platform -- the heads of the bolts are recessed:



This is a shot from underneath the platform, showing the angle bracket:



(By the way, if the components look distinctly un-glamorous, that's because this was all made from spare parts and pieces stashed in the corners of my workshop.)

Once I had the platform assembled, I put a piece of thin plywood inside the crate to sandwich the bottom of the crate, using countersunk wood screws -- the screws go through the crate and into the platform:



This milk crate is very sturdy -- no chance of materials failure.  Inside the crate, I built a foam "nest" to hold the gas can securely on all sides, using (of course) scraps of foam, including old purple "pool noodles:"



I knew from past painful experience that if a plastic gas can is subject to chafing for a long time, it will wear through.  So no hard surfaces are in contact with the gas can.  This is a shot of the gas can in its little nest:


Note, by the way, that the nozzle of the gas can is pointed inward.  Obviously, in order to add fuel, I loosen the collar and rotate the nozzle 180 degrees.

This is a side view of the crate and the gas can on top of the tire:



Notice the straps coming down from the crate and around the tire -- that is a ratchet strap.  By strapping the crate to the tire and anchoring the crate (on the platform) to the upright rods, the whole assembly vibrates much less than it did with just the tire on the mount.  Although it is hard to see in this shot, the straps are twisted to cut down on vibration due to the wind at freeway speeds.

This is a closer shot of the gas can in the crate:



You can see a piece of thick vinyl tubing extending across the crate and through the handle of the gas can, preventing it from bumping up and down while on the road.  Also, notice the bungee cord around the perimeter -- it is also designed to reduce the vibration of the ratchet straps.


The whole thing is very easy to install and remove.  To install, the platform drops down onto the rods, and I tighten the nuts.  Then the ratchet strap goes around the tire and the crate.  To remove, just loosen the ratchet strap, loosen the nuts on top of the platform, spin them up and off the rods, and then lift the platform off of the rods.

If we feel the need to lock the gas can in place, that will be easy to do with a combination bike cable lock.

That's it -- a lot of detail for a fairly small project.  But the design issues were more interesting than the fabrication process, which was pretty straightforward.