Wednesday, June 21, 2017

MaxTrax Camper Mount - March 2017

Click on a photo to view a larger version.


Introduction


I thought MaxTrax would be a potentially useful recovery device for my camper. They are very versatile and easy for one person to deploy. Storing them on the roof would not necessarily be convenient when I needed them, and mounting might be problematic. Hanging them above the cab might work if I didn't already use that space for spare gasoline storage and a portable solar panel. I didn't want to mount them on the side of the camper lest they catch on a branch or someting. Consequently, mounting on the rear seemed the logical place. But how?

I initially thought I'd attach a mount on the rear wall, but I got zero help from the camper manufacturer as to where the frame members could be located. I didn't want to try to use a sheet metal screw on the siding as that didn't seem secure. I could run a bolt all the way through to the inside and use a plate, but that would require removing my compressor refrigerator - too much work. I thought about some sort of bracket attached to the jack brackets, but that had problems, too.

I finally got the idea to mount a board to the siding using strong double-sided tape. I'd then use a strap to hold the MaxTrax against the board. OK, but how would I hold the bottom? I thought some sort of "stirrup" might work, but how to make one? I did what I often do when trying to come up with a design - I wandered around the home improvement store looking at brackets, handles, metal shapes, fasteners, etc. hoping for inspiration. When I spotted the flat shelf support brackets, it all came together.

When mounted, the MaxTrax completely block the access door to the propane bottles. This is not a major problem as I'm too lazy to shut the propane bottle valve each morning while traveling and open it each night as I set up. If you are more safety conscious, it is not difficult to undo the strap and lift the ramps out to access the door (even with the security cable attached.)

MaxTrax on the back of my FWC Fleet. Details of top and bottom, inset.

The mount was designed and constructed in March 2017. This post was written June 2017

Design and Construction


The backboard holds the strap and keeps the ramps from rubbing on the siding. It is 13.25" in length, just wider than the width of the MaxTrax, which are 33cm wide (12.9"). Initially, I cut the board a bit longer, but when I tested before mounting, there was too much leeway with the strap. The shorter board keeps the strap taut. I chose 4" for the height of the board because the aluminum siding on my camper has 1" wide raised plateaus separated by 2" valleys. I could affix 1" wide tape at the top and bottom and there would be a 2" space between the plateaus to run a strap behind.

Backboard with strap in "city" configuration.

Backboard with strap open and ready for the MaxTrax.

I added a radius in the middle of each end where the strap would wrap around from the back to minimize the chance an edge would abrade the strap. I sanded and painted with an exterior latex primer. I then painted all sides with a semi-gloss white latex exterior house paint, with the exception of where I would be affixing the tape. I gave it a second coat and let it dry well.

The left end of the backboard. You can see the area where I added a radius to protect the strap.

The right end of the backboard.

I used 3M Extreme Mounting™ tape as I wasn’t really aware of the VHB alternative at the time. The EM tape bonds almost as well, and since it’s sold as a consumer product it is more readily available and much less expensive. I cut strips of tape to be slightly less than the length the board, one along the top, one along the bottom, on the back. This length is plenty strong. (On a later project, I used strips of VHB tape to bond my custom made solar panel brackets to the camper roof as those brackets were much smaller and needed a stronger bond.)

I actually did a test of the bonding first. I used a 1" length of the EM tape to attach a 1x2" pine board to a piece of bare aluminum. The next day I tried to pull them appart and was unable to do so, even pulling as hard as I could (I did not twist, as there would be no twisting force in my application.) Excellent!

I lightly sanded the area where I would apply the tape on the board and cleaned it with rubbing alcohol. I also used alcohol to clean the camper siding. I attached the tape to the board, pressing hard. Then pulled off the backing and pressed it onto the siding in a position I'd already measured. I left room between the board and lip of the door jam to provide room for the strap. I pressed hard. The tape bonds quickly, but did not put any strain on it until it fully cured.

These are the velcro straps I used: AIRNIX 4 Pack (40" x 1.5") $9.99 on Amazon as of this date. I'd used this style of strap before. The buckle allows it to be drawn taut and the strength of the hooks and loops is significant when the pull is longitudinal.

In case you’re curious, the little multi-colored cord you can see in some of the photos was added as a safety strap. When I first mounted the backboard with the 3M Extreme Mounting tape I was concerned it might not hold on rough roads, so added the cord, which is attached to the door stop/latch, to catch the ramps if the tape came loose. After the White Rim Trail and my last trip, I don’t think that board will ever come loose.

Assembled bottom bracket.

The bottom bracket is comprised of two 8” zinc-plated steel corner braces that I got at the home improvement store. I put them together to make a square ‘C’ shape with a 10.25” opening where the ramp goes. I had intended to spot weld them together, but my neighbor with the welder was out of town when I needed him (and the holes didn’t line up, so I couldn't bolt them together), so I just bound them with gaffer tape, which seems to work great. I then used lag screws to mount the bracket to the board that runs along the back bottom of the camper. Only one set of holes lined up with the camper board, so added a second screw on each side, outside the brace, with a washer. Seems strong enough, and I don't think there is any flex; I may weld it later... or not.

Oblique view of the underside of the bracket and lag screws holding it to wood camper frame.

Here is a quick and dirty composite showing two corner braces before being slid together to shape the bracket. The perspective is off as I just mirrored one product image downloaded off the web:

The ends slide together, one over the other, in the direction of the arrows, to form the '[' shape

The bottom spacer board has two functions. It’s about as thick as the backboard so holds the ramp off the siding. The back of the MaxTrax has spikes (similar to those on top) that you don’t want rubbing on the siding. I insert one end of the MaxTrax ramp with the top tilted out, then slide the spacer in place, then tilt the ramp upright, and strap the top to the backboard. That locks the ramp into the bottom bracket as the last row of spikes on the end of the MaxTrax would catch the bracket before it could jump out even if the velcro strap was loose. Difficult to describe, but if you look at the inset image at the top of this post showing the bottom of the ramp in the bracket, you can see the row of spikes above the bracket, sort of see the row of spikes below the bracket, and you can see the spacer holding the ramp against the bracket between those rows.

Bottom spacer with grooves that fit the lip of the MaxTrax.

The bottom spacer was initially a little too think, and consequently put too much stress on the bracket when I strapped the top in place. Rather than use a thiner board I used a Dremel tool to carve grooves in the spacer. The lip of the ramp fits into these grooves. This provides the proper spacing between the ramp and camper siding and the grooves also keep the spacer board from working its way out due to vibration. I primed and painted the board, as I did the backboard.

When on the road with the MaxTrax, I use a bicycle security cable to lock them to the truck frame. I take them off when I'm not traveling rather than risk someone cutting the cable and liberating them.

I hope my mount will help you figure out a way to mount yours. If you have questions, either leave a comment, or email me at the address at the top of the page.

4 comments:

  1. I hadn't been in on the discussion of getting the MaxTrax.. Or I forgot. Anyhow, even though I will never need this information in my real life, I truly enjoyed reading your description of how you solved each problem/step of the installation. Fascinating.... truly! (And the MaxTrax is a wonderful invention. I'm glad you have one, just in case you ever need it!)

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  2. Great post, Bill! Clever "build" and I hadn't heard of EM or VHB tapes or the Airnix straps. Thanks!

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    1. MFH, thanks for reading and commenting. I appreciate it. The straps are pretty generic - plenty similar - but the 3M tapes are the real deal.

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Thanks for taking the time to comment. I really appreciate it!