Slide Out and Tool Box Repairs

  Addressing a "Dumb-damental" Design Flaw in Our Lance Slide Out

Event Report 20230720

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Background

We purchased our Lance pull-trailer back in late 2018 and performed our build-out in 2019.  Since then, we have logged well over 20K miles on and off the road with this setup.  During this time, we have been reasonably careful about treating the slide out with respect.  To be honest, it provides a ton of additional room within the living quarters and is relatively easy to deploy and retract.  Of course, all benefits of the mechanism are nullified when a failure happens.  Our worst-case scenario was that the mechanism failed with the slide out extended thus preventing us from driving.  A failure when retracted, while annoying, would only be that - annoying.  Most of the interal systems can operate with the slide out retracted.  Indeed, we have slept in the living quarters for weeks on end during the build-out with the slide retracted.  It was annoying, but functional.

During our last outing at the end of COVID, we noticed a separation occurring between the mounting flange and the outside skin of the Lance.  Several of the flange mounting screws were broken due to stresses.  Since we had been off-roading, I simply assumed it was stresses associated with torsion on the Lance.  Future travels and extra information would prove that was not the case.

Turns out that this problem has been reported by a large number of Lance owners, at least those that actually use their campers.  And, this problem has been known by the vendor for some years.  In fact, the vendor has an approved "repair" for the issue, but the repair does not address the root problem.  The root problem is simply too much unsupported mass on an extended moment arm.  That mass and the lever action ("moment" in engineering terms) resulting from dynamic loading from bumps in the highway causes the mounting flange to tear away from the outside skin.  Given enough road forces, the separation would continue and would render the slide out useless.

The Solution

Basic engineering is a wonderful thing.  Certain laws apply, and when you attempt to violate those laws, you get  "corrected" in short order.  In this case, having a substantial mass on the end of a long moment arm (the slide out enclosure) and subjecting it to dynamic loading (a heaving bump in the interstate) results in huge forces.  The "correction" in this case was separation of the mounting flange from the outside skin of the camper.  Reattaching the flange to the skin, while simple, does not result in a true fix as the root problem (the unsupported, cantilevered mass of the slide out) remains unaddressed.  So, providing support for the cantilevered mass while in motion IS the actual fix.  Although in this case, other actions were required for either completeness or ease of use.

In addition to the factory-specified repair actions, we utilized two approaches to address this issue.  The first approach sought to minimize further damage and the second approach sought to minimize the setup and teardown hassle.

The photos below are what we saw.



This photo was taken while the Lance 1685 was still a pull-trailer.  Note the room available due to the slideout.  When the slide out is retracted, the padded facia is about where the black vent is under the bed.


When viewed from the outside, you can see the upper and lower gear racks that are used as part of the activation process.  Inside the wall is a motor and 2 gears on a common shaft.  The top gear engages the top rack and the bottom gear the bottom rack.  They are on a common shaft to prevent sagging of the slide out when extended.


A closer view of the bottom gear rack.  Note the white flange on the wall of the camper.  This flange is being torn from the wall by the unsupported weight of the slide out when retracted.

  A drawing makes better sense of the forces applied to the various components.  The slide out is only supported by the gears, racks and common shafts of the actuator assembly.  There is a front and rear motor and they are synchronized (somehow) to keep the slide out from jamming.  When a dynamic load is applied, say with a heaving bump in the freeway, the load is turned into a tearing torque that manifests on the lower-outer mounting flange.


On our extended road trip, we met a couple at the Montrose KOA that also had a Lance 1685 but in the factory pull-trailer configuration.  They, too, had the flange separation problem and discovered that there was a factory approved repair for the problem.  He described the repair in detail and I realized that the fix was only a partial fix.  The real fix was to prevent the problem from happening in the first place by eliminating the unsupported, cantilevered weight of the slide out using some kind of adjustable support.  In Colorado Springs, we purchased 2 4-ton hydraulic bottle jacks from Harbor Freight.  We used them to get us across the Rocky Mountains and to Durango, CO.  But, we had noted that the jacks would sometimes slip into a location other than the starting position due to the dynamic forces encountered during a big bounce.  So, when we reached Durango my friend Brad assisted us in fabricating a mechanism to "trap" the jack in a known location.  For each jack (one fore and one aft) we cut 2 wooden blocks.  One of the blocks had a hole drilled to accommodate the load end of the jack to provide the trap.  This block was then screwed into the other block to assist in spreading the load of the jack so it would not punch through the underside of the slide out.  In the photo above, you can see the pair of blocks on the aft side of the slide out.  Since Brad did not have a full set of wood working tools (in this case a router), the block was not flush with the surface due to the thickness of the aluminum angle.  It looks ugly, but works well.  The bad news is that you must position and raise both jacks to the correct height upon retracting the slide out.  And, more importantly, you must lower and remove the jacks before attempting to extend the slide out.  A workable solution, but at the cost of added inconvenience with each cycle of the slide out assembly.  A different solution is needed to make the fix both convenient and robust.


We started measuring sag on the walls and determined that we were seeing 2.5" of drooping before installing the factory-approved repair action.  After the repair, the droop was down to about 0.5 inch, but the weight of the slide out and the contents of the clothing drawers was still unsupported and cantilevered.  This meant that the repair, too, would fail if subjected to sufficient dynamic loading.  We devised an improved plan that called for leaving the current jack cups in place in case we needed them again and augmenting them with a set of caster wheels that would support the cantilevered weight over the entire range of motion of the slide out actuation.  We had noticed that the sound of the slide out extending and retracting greatly degraded with the amount of droop (the motor had to work much harder with the odd torsional forces on the slide out).  Implementing the factory fix made the motor sound better and the rate of motion became substantially faster.

The caster wheels would need to be on a column and the column would need to be securely fasted to the slide out.  So, the first task was to get a flush-mounted support fabricated.  Measuring the thickness of the aluminum angle told us how much material needed to be removed to provide the flush mount.  In the photo above, the first routing pass has been made on the left side of the board clamped to the work bench.


I used my Bosch hand router with a square bit to remove the 0.1" of material needed.

Once the mounting plates were routed, they were cut to length.


Next, some 1x1" angle needed to be cut to fabricate the column.  My cold cut saw did the job nicely.

The caster wheel assembly would be welded to a 7" length of 1x1" thick wall square tubing.  The trick was to get it "jigged" correctly so that the wheel was correctly aligned with the axis of the tubing.  The plan was to drill a hole in the center of the wheel mount to allow insertion of a threaded rod.  Above, the wheel is test-fit onto a strip prior to drilling.

Once the hole was drilled in the center of the mount, the rod and a nut was added, then the tubing, then a fender washer and another nut.

The whole assembly was positioned, aligned and the nut was tightened on the rod to hold the assembly securely.

My MIG welder was used to run a bead between the wheel mount and the tubing.  A bead was run on the opposite side as well, then the threaded rod, washers and nuts were removed.

A cutoff wheel was then used to remove the unneeded overhanging portions of the wheel mount to provide better clearance from the toe kick plate when installed.
 


The pieces of the 1x1 angle legs were jigged and clamped in anticipation of welding.


The legs were assembled as mirror images (one left, one right) so the open portion of the angle was toward the center of the slide out to provide better access for final assembly.  Once welded, holes were drilled in the mounting flange (short leg) to allow attachment to the bottom of the slide out.  The legs were attached to the mounting plates using 1/4 x 1" lag bolts.

Recall that under the center of the cargo drawer is the wooden pocket for the hydraulic jack.  The mounts for the legs will be installed to the outboard side of the pocket.

Locations of the through-holes were marked on blue tape and were drilled for insertion of 1/4-20 x 2.5" stainless steel bolts.


Bolts with large fender washers were inserted through the holes and the mounting plates with legs were attached and secured with Nylock nuts.  Once the legs were attached, the tube/caster assemblies were added and clamped in place as a height test.  This method was used to address two critical issues: 1) ability to assemble in-situ; 2) to allow last minute adjustments in height based on the observed sag of the slide out.

The other side was installed, wheel height set and the slide was actuated to test its behavior.  Setting the height using the fully retracted position of the slide out as the baseline produced an excessively tight fit.  So tight, in fact, that when the slide out was retracted, the point loading of the caster wheels depressed a groove into the flooring material.  Sadly, the U.S. RV industry uses the cheapest possible components.  In this case, the floor is a sandwich of 1.5" Styrofoam panel glued to 2-1/8" thin plywood cover panels.  This configuration, while lightweight and cheap, is not robust to extreme point loads produced by the caster wheel when supporting several hundred pounds of cantilevered slide out.  The Styrofoam directly under the center of the wheel track was crushed by the load.  After an extensive conversation, we concluded several things.  First, the load on the wheel will be determined by what slide out location is used to set the baseline wheel height.  Second, application of a stiff strip of metal would spread the load and prevent damage to the flooring material, albeit at a "visual cost" to the result.


A trip to the "steel store" (also known as Industrial Metal Supply) got me a 12x48" strip of 16ga (0.05") galvanized sheet metal.  The sheet metal was cut with my worm-drive saw with carbide steel blade and the resulting strips were de-burred and dressed.

The clamps were released and the wheel removed.  The 16ga strip was positioned on the floor and the location was marked with blue tape.  Both the floor vinyl and the sheet metal strip were thoroughly cleaned with a damp cloth followed by acetone to remove dirt and grease to insure good adhesion with the glue.

Small amounts of 3M 5200 adhesive/sealant was used to attach the load spreading strips to the vinyl floor.  Blue masking tape and weights were used to hold the strip in place while the adhesive cured.


  The strips were installed, weights applied, excess glue was removed and we waited for a 48 hour curing period before additional testing.  In the photo above the strips have been installed, glue cured and blue tape removed.


We used the height of the slide out at the 1/2 extended position as the baseline  for setting the wheel heights.  With this baseline, the wheel is not in contact with the plate for over half the travel distance, demonstrating the variance of the height due to sagging.  Note that the wheel is elevated above the support strip while the slide out is fully extended.  Note that the position of the tube in the leg frame must be evened out over the extremities of slide out motion.  In the photo above, the vertical position of the tube has been selected, and 2-3/16" holes were drilled through the leg and tube and an aluminum pop rivets were installed setting the height of the wheel.  Note the height of the wheel above the rolling surface when extended.

The forward leg showed similar height properties to the aft leg, showing that the variance in height was common to both sides.  In the photo above, the slide out is in the fully extended position.

We selected the center of the slide out in-out motion (half retracted) as the baseline for wheel heights.  The assumption was that the mass would be effectively balanced at this position and therefore the height would be "neutral".  In this photo, the wheel assembly is in full contact with the aft metal strip and the slide out is in the fully retracted position.



The forward wheel of the slide out in the fully retracted position.  It is true that the legs are a kicking/tripping hazard, but forewarned is forearmed.  We felt that the severity of the hazard was worth the added convenience of easy extension/retraction.



On to the next task: repairing the rear tool box hinge.  Thor has 3 large (24x24x36") steel tool boxes that are used to carry "stuff".  One carries large tools and pry bars, one carries the folding stair assembly and lawn chairs and the last one carries our electric unicycles (EUC).  The aft driver side box is the one that takes most of the hits because it is in the least visible position.  That box has been repeatedly tagged over the years on large boulders and similar off-road obstacles.  The impacts have taken their toll on the hinges and mating surfaces of the box to the point that a repair is needed.  To gain the necessary access for the repair, the door must be removed.  This required drilling out the pop rivets used to attach the hinge to the box.  Above, the door is free, note the bend in piano hinge due to the impact damage.



Once the door was removed, the main box was adjusted using a Harbor Freight hydraulic "power pack" and some wooden blocks.  The blocks were placed between the ram of the power pack and the sides of the box.  The ram deformed the box walls and straightened the mountain surface.  Pry bars (AKA a screwdriver) and vice grips were used to straighten the mounting edge that had been crushed by the impacts.  Note the edge deformation on the lower left corner of the box.



The leading edge of the box had taken some good impacts as well.



Once the mounting edge was straightened, the door was re-attached using 3/16" pop rivets and rivet gun.



The aft corner of the door mount had suffered sufficient damage to require an additional pop rivet to insure mechanical integrity.  Above, it can be seen that the rear-most rivet did not set fully due to the deformation in the mounting surface.

It remains to be seen whether our wheel-based repair will stand up over the long run.  While it is easy to complain about poor designs or cheap material choices, the fact is the basic Lance design would work fine for most folks who use it in a "nominal situation".  Our usage scenario is far from nominal, so they get a pass in this case.  That said, it would have been nice to have been told that this was an item of concern and had we known that, we would have installed the wheels from the get-go and the whole issue would have been prevented.  For those folks who are not lucky enough to have access to metal working tools and a welder, the simple jack and pocket solution is a full solution to the problem except for the wear-and-tear on the motor and gear racks associated with the sagging.

I am still a Lance fan, but now I have some reservations.  And I am sure that the have reservations about me.  And they would surely have reservations about me slaughtering their product and mounting it on Thor and subjecting it to a good thrashing off-road.  But the truth is than the biggest hits we suffered were on-road.  The reason is simple - when off-road I alone control the motion of the truck and can therefore choose how to navigate obstacles.  But, when on the highway, the flow of traffic controls where you drive (lane) and the speed.  Sometimes, discontinuities in the road bed are unavoidable due to inability to change lanes in time or inability to avoid the obstacle safely.  So, in my mind, Lance should come up with a conclusive solution for this issue and fold it into the manufacturing process so all buyers benefit from the change.


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