Advice needed for repairing Schwintek Kitchen Slide

[Oscarvan]

He showed me a picture of where to cut out the floor below the fridge to get at the roller.

How's that for serviceability!

[uralman]

On my 2015 34qs the rollers would run over the seat belt bolts damaging the rollers. Had to remove the bolts.

[NMWildcat]

We have used Lazy Days Tucson for hydraulic slide service that local independent service only shops couldn't handle. They did an excellent job, but like every dealer, it took way too long. But the advantage is the KOA right next to it and they will move your unit between the park and their service bay when needed. They do seem to work on a lot of motor homes in their 70 bays (I think it's 70 anyway).

Good luck with the schwintek slides. Every one of our friends that have these type of slides have had (and continue to have) problems. Fivers and MHs.

We are looking at new RVs and it is hard to find any that don't use at least one of this type of problematic slide. I don't understand.

[gordonsick]

I’m finally in a position to explain what I did to repair the 16 foot Kitchen Slide on my 2015 34QS. I started this thread on December 10, 2018 and now, August 15, 2019, I have my solution. That took over 8 months, and even longer if I count the time since October or November of 2018 when the slide became non-functional.

In subsequent posts, I’ll explain how my brother Doug (a retired mechanical engineer) and I installed a new H-track assembly and fiddled with it to get it to work properly. My cost for a pair of Schwintek Slide Room H-assemblies (right and left, including motors, but not electronics or wiring) from Forest River was US$1426.27. Thanks to Randy Alwine (Warranty) and Andy Thompson (Parts) for getting me 6 aluminum plates (gratis) and the Complete Slide Room System for this amount. I also spent C$231 for a Calgary-based mobile RV technician who helped me find the control electronics in the Main Storage Bay with the sliding tray, but who took forever to get parts and then threw a fit when I secured them myself. He said that what I did to get parts would make the repair extremely difficult and that he wouldn’t be able to deal with it until September, by which time I needed to leave town.

I spent some time reading the Lippert Schwintek manuals, which are large in number and very redundant. I wrote up a repair procedure to make sure I understood what needed to be done. Taking our time, my brother and I had the old assembly out and the new one installed in about 4 hours. But, we encountered some problems and had to repeat the removal and assembly, as discussed below, before getting everything to work properly.

This is a job that is within the skill set of many members of this Discussion Forum. It is a two person job, but does not require any unusual degree of strength, so it could be done by a husband and wife team. The key to the installation is to read manuals and plan ahead.

[gordonsick]

The first step was to contact Randy Alwine in the Forest River Diesel Division (FR) to discuss the problem by email. He asked for some photos of the problem that I discuss in the first post of this thread, so I was delayed until I got back to Tucson where I had left the Coach for the winter. He sent me 6 aluminum plates at no cost. I had to cut some and drill them all. I jacked up the slide to install the plates. Others, including Oscarvan, have described the process and I’m grateful for the work they did to get Forest River to realize that there was a problem that FR needed to address.

Randy and Oscar indicated that there was a possibility that the damage extended to the large roller(s) under the fridge end of the slide. Randy sent a photo of how to cut a hole in the woodwork below the fridge to access this roller. Fortunately those rollers were not damaged. I must note that, if they were damaged, it would probably be simpler to replace them by jacking up the slide and undoing the bolt that formed the axle for the roller. That would allow it to be replaced without cutting holes in the floor. It looked like a deep socket and box-end wrench would do that job.

As it turns out that there was damage to other rollers: the V-rollers in the H-column were damaged by the weight of the slide on them. They are not built to hold the slide up. These V-rollers hold the pinion spur gears in the H-column at a proper operating distance from the upper and lower rack gears. With the damage to the V-rollers, the spur gears backed away from the rack gears and started to slip, damaging the whole assembly. Moreover, the bearing blocks that held the V-rollers and spur gears came loose because the Gib rivets broke.

If this sounds like Gibberish, please forgive me. You have to read the manuals to completely understand the issue. But, the bottom line is that the collapsing floor of the slide assembly allowed undue weight to be placed on the V-rollers. They became damaged and they stopped holding the spur gears, which started to slip on the rack gears. And I was without a functioning slide.

After some searching, I was put in touch with a mobile RV technician in Calgary who has worked on Schwintek slides. He came over and showed me how to find the electronics Controller and press an over-ride button to get the slide to move in and out under duress. He realized that I needed a new rack gear, so he took measurements and sent an order to Schwintek to get a replacement for the whole H Assembly, which is the upper and lower racks (attached to the side of the slide room wall) and the H Column (attached to the coach body, that holds the pinion spur gears, motor and a driveshaft). But, Schwintek refused to work from measurements, insisting that they needed to know the serial number or model number that was printed on the whole assembly. My technician (and I myself) couldn’t find this model number. (Subsequently, in doing my repair, I found that the model number was covered by an optional black backing plate that was installed inside the coach parallel to the H Column.)

So, we needed to contact Forest River to find the part number. I contacted Randy Alwine again and he told me to phone the Diesel Division Parts department. FR does not provide an email address, and no email address appears on any of my invoices. So, I had to keep leaving telephone messages. Eventually, I was fortunate to get Andy Thompson on the phone. It did not take him long to find the build information on my 34QS coach. Moreover, he had a full pair of H Assemblies in stock. The price was comparable to what my mobile RV tech suggested I would pay, although I think that the RV tech was only going to supply the assembly for one end of the slide, not both. BTW, when I got the assemblies they were marked: “Formerly V000295423, now F100107339”. I suspect that Lippert understands one number and Forest River the other.

Andy said that Lippert/Schwintek ships the H Assembly to them mounted on a board, which is pretty expensive to ship. He said that he had taken the H-assemblies off the boards to ship them in a much smaller package, and that his customers had not incurred problems when they got them this way. I had read enough Lippert documentation to be confident that he was right. So, I asked them to break things down and he sent it all off. I got it very quickly, despite the border crossing.

My RV tech was on vacation at this point and I sent him an email with the good news that I had secured the parts and that I elected to have FR remove the parts from the board. He responded with an aggressive email to say that this would make the installation much more difficult and that he couldn’t find the time to work on it until the Fall. This left me quite concerned about his competence. Moreover, he had said earlier that he might have to discard the aluminum plates to do the installation. Those two things were enough to send me off looking for another installation solution.

I read the manuals carefully and decided that I could do it myself, but to “wear a belt AND suspenders”, it was a good idea to enlist the assistance my brother Doug who is very good with mechanical things and retired, as well. Doug did help with the stuff that I had figured out and helped me solve the surprise problem that we encountered after the installation.

Read on, if you are interested in the details.

–Gordon

[gordonsick]

Lippert posts a bunch of manuals on the Schwintek slide at https://support.lci1.com/in-wall-slide-out. They repeat each other, with slight variations that add a little tidbit of information here and there. There are two documents that seem to be sufficient. One is a very helpful diagram at https://lci-support-doc.s3.amazonaws..._assembly_.pdf I recommend that you print this out or open it up in another browser window while you read this post. The other is a manual for the repair kit at https://lci-support-doc.s3.amazonaws...cd_0001768.pdf

The first picture below shows the new H-assembly before I installed it. The gear racks are on the ends and they are attached to the sidewalls of the slide. The H-column between them contains the motors and spur gears. It is attached to the Coach wall.

The second photo below shows the motor installed in the H-column with the spur gear and V-roller exposed. They are held in a steel bearing block. When assembled, they are covered by the gear racks. Above the spur gear is the black plastic shoe that slides in the gear rack and maintains the vertical relationship between the V-roller and the V-groove in the slide rack. On either side of the V-roller is the plastic Gib, which allows the bearing block to slide in and out relative to the H-column. Not shown are the rivets that limit this motion to +/- 1/8”. Finally, note the motor that is dropped in from above. At the bottom of the motor you will see one of 4 screws that drop into holes in the bearing block to keep the motor case from turning when it applies torque to the hexagonal drive shaft (called a torque shaft by Lippert) that goes through the spur gear and descends below to the lower bearing block. The motor is connected to the drive shaft by a steel coupler above the spur gear, which is internally hexagonal on the lower end and having a D cross-section on the upper end to fit onto the motor shaft.

The third photo shows the lower bearing block that came out of the damaged unit. The V-roller came apart. The plastic shoe on the lower left fell out of the bearing block. And, the whole bearing block came out of the H-column because the rivets failed the Gibs in place.

The fourth photo shows the damaged upper bearing block. The V-roller remained in place, and the shoe remained in the gear rack. But the rivet holding the assembly from falling out is sheared off. On the left end of the drive shaft is the adaptor that connects the motor to the drive shaft. Notice a groove in the drive shaft beside the adaptor. The groove is supposed to hold a snap ring (or circlip) that sits on the upper face of the upper spur gear. It holds the drive shaft from sliding out the bottom when vertical. That snap ring is missing. Page 6 of the repair manual cited above shows some “Stakes” in Figure 10. It seems likely that the Stakes are the missing snap ring.

[gordonsick]

• Make a simple workbench out of sawhorses and a piece of plywood laid on top. This gives you a clean work surface off the ground on which you can work with the H assemblies.
• We started with the slide closed and removed as many screws on the gear rack as we could access on the slide side-wall, leaving the very end screws in place to hold the gear racks in place on the slide wall. We only worked on one end of the slide, leaving the other untouched.
• We placed an 8” (approx) stop board on top of the slide to restrict the slide from tipping out, if we made a mistake in the repair process.
• We opened the slide to rest against the stop board. Since the slide was stalling on us, we needed to enact the over-ride feature of the “Dual Motor Synchronous Velocity Slide Controller” that is shown on Page 4 of the Repair Kit Manual. Other manuals discuss this item in greater detail, and we have version C2 of this Controller. The Controller on our Coach is located in the roof of the Main Storage Bay (the one with the sliding tray). Other locations are possible, and there is one for each Schwintek slide. There is an opening and on the right side is a microswitch that you press 6 times and then hold the 7th time until a bunch of lights start flashing. This puts the Controller in override mode for the next 60 seconds. That means that it will ignore any feedback from the motor that says the slide is jammed. This allowed us to open the slide with the standard switch inside the Coach.
• Outside the Coach, we jacked up the end of the slide to remove the weight from the roller nearest to the slide end that is being repaired. Just raise it enough to take the weight off the roller. You want to leave no vertical load, up or down, on the H-column.
• Remove all the remaining screws holding the gear racks to the sidewall of the slide, including the screws that you left attached inside the coach.
• Slide off the rubber bulb seal on the H-column to expose the screws that hold the H-column to the Coach body. These bulb seals prevent drafts when the slide is closed and they slide down on a track for removal.
• Remove all the exposed screws from the H-column. There is one in a slightly different position at the top, under a rubber bulb seal. This holds the motor in place.
• Place some duct tape alongside the Gear Rack and the H-column in such a way that you avoid scratching the paint when you insert a scraper under those parts to separate them from the walls. Loosen the Gear Rack and H-column from the walls.
• Inside the Coach, remove any optional black plate that may have been installed on the Coach wall parallel to the H-column. You should also remove the vertical rubber bulb molding that is attached to the H-column–these moldings seal the slide from drafts when it is open and they are on a track, so they slide up or down.. You can optionally remove the sweep moldings that are attached to the H-column – these are inside the coach and sweep against the slide wall as it moves.
• Inside the Coach, disconnect the motor wires from the motor on the good end of the slide. The motor is at the top of the H-column inside and you might have to strip back some molding to see it. This motor has 300:1 or 500:1 gearing, so leaving the motor in place but disconnected will prevent that end of the slide from moving or tipping when you work on the end that you are repairing.
• Briefly run the slide control switch in the direction to move the slide In. This should release the H-column from the Coach wall. Note that Schwintek provides some kludgy instructions to run a jumper wire to that motor and power it from a cordless drill battery. Our procedure uses the motor controller and Coach batteries to the same effect, but in a more professional manner. Recall that we disconnected the motor from the good end of the slide, so this process only runs the motor on the end of the slide being repaired.
• Disconnect the wires to the motor on the end of the slide to be repaired.
• Remove the motor (perhaps not necessary at this point) from the inside of the H-column. To do this, remove the short screw on the outside of the coach from the H-column that goes into the motor. It may still be covered by a seal, but, at the very least, it was covered by the bulb seal that you removed. The motor comes out by lifting it up and pulling it inside the Coach through the notch in the H-column. You may need a screwdriver to push it up.
• At this point, you can remove the H-assembly from the outside of the Coach. There is enough space between the Coach wall and the Slide wall to angle the assembly out and clear any flanges on the outside face of the Slide wall.
• Put the old H-assembly on your makeshift workbench and examine it for damage, and to see how the parts are assembled. In the previous post, I’ve attached pictures of the damaged V-rollers and bearing blocks from my slide.
• Insert the new upper and lower gear racks into their respective bearing blocks. You need to make sure that they each contact their spur gears at the same time, so that they extend from the H-column by the same amount. Lippert calls this synchronization a timing procedure. When done properly, moving one rack in and out moves the other synchronously, without jamming or binding. When doing this, note that the gear racks have a machined notch on one end and this is the correct reference point for synchronization. The other end may have been cut to length with a hacksaw and is not a reliable reference point.
• Trim away any rubber gaskets that may get caught in the assembly and jam the gears or shoe from moving.
• In some of its documentation, Lippert suggests that the mechanism shouldn’t be lubricated. But, in other places, such as on Page 9 the Repair Manual linked above, it recommends using CRC Power Lube with PTFE (misspelt PFTE by Lippert). Elsewhere it says this is the only acceptable lubricant, so I made sure I got it. The PTFE is generic Teflon and will leave a dry lubricant. But, it is in a petroleum based aerosol. Using substitutes may have an aerosol that damages the plastics or rubber in the assembly, so I protected my $1400 investment with their recommended lubricant.
• I used this CRC Power Lube on the V-rollers, gears, Gibs and the shoes, as well as the gear rack grooves in which the shoes slide.
• Lippert had some foam rubber ends for the shoes, which I was worried could jam in the grooves as the shoes slid back and forth. Moreover, the Powerlube dissolved the glue holding them on, so I discarded them. It might be that this foam rubber is intended to sweep the rack groove clean. A better solution would be to periodically inspect the groove and clean it with a Q-tip.
• Next, we installed the new H-assembly into its place between the Slide and the Coach. At this point, the motor is not installed so that the racks can move back and forth.
• Screw the upper and lower gear racks to the Slide wall, using the holes from the original gear racks. They have identical spacing and we had checked to make sure that the original gear racks were parallel.
• Push the H-column into place against the coach wall. We had to file off the bottom end to get a fit.
• Lower the jack that was holding the slide so that the weight is borne by the roller on the aluminum plate under the slide.
• Since the aluminum plates raise the H-column by 1/8”, you want to consider drilling new holes to hold the H-column to the coach. You can’t just enlarge the existing holes. Fortunately, the holes provided in the new H-column are about 1/2” above or below the holes on the original H-column. So, you need to drill new holes to start the self-tapping screws. In my original installation, the installers broke several self-tapping screws on this assembly, and I decided to be more careful than them.
• With the H-assembly installed, we found that the slide moved out easily by hand, so we knew that there was noting binding elsewhere in the slide system.
• We dropped the motor into place from the inside of the Coach on the repair end.
• We hooked up both motors and removed the 8” block at the inside top of the slide.
• We hit the switch to move the Slide in and out, synchronizing the position of both ends.
• If the above works, install the bulb seals and inner flanges and you are done.

If that doesn’t work, read my next post!

[gordonsick]

Even though we found it easy to move the slide by hand after the installation above, the motors ran very heavily and sometimes stopped, just as they did before the repair. Things were much better, but still not reliable.

It became clear that the Dual Motor Synchronous Velocity Slide Controller (Model C2 in our case) was sensing a problem and stopping the motor on one end or the other. I was able to get the slides to move fully by doing the over-ride procedure described above. This is to press the microswitch Mode Button on the Controller 6 times and then holding it for a few seconds on the 7th push.

At this point, I was tempted to call Lippert for advice. I wasn’t getting any consistent fault codes from the Controller as listed on the front panel of the Controller.

Then my brother Doug noticed that the steel spur gears were making marks on the aluminum rack gears already and they were contacting the racks on the high side. We noticed that the spur gears were not symmetric, but had a bearing lobe on one side. So, we decided to pull the assembly out and examine the orientation of the spur gears. At that point, Doug noticed that the snap ring (stakes) on the hex drive shaft was out of place and not sitting in the groove machined for it, so we slid the snap ring back into place. We also did a careful comparison with the other new rack assembly and finally concluded that the gear orientation was correct, with the bearing lobe on the bottom.

So, we put this all back together. We weren’t sure we had done enough to solve the problems we had incurred earlier, but the slide still moved easily in and out by hand.

Well things seemed to be a bit better, but the Controller was still shutting off at erratic times. I went back to look at the motor to see what fault codes it was showing and I noticed that the wire to the new motor was really tight, and it had been tight all along. FR had installed the wire and plugs, and then put a zip tie on the whole assembly that tightened things up. So, I loosened that connection. Then I switched the controllers between motors to see if there was a wiring problem. Things started to work, but in became out and vice-versa, because the motors must move in counter directions. So, I switched the plugs back and things seemed to work properly.

So, things are working. We’ve successfully opened and closed the slide several times.

The two ends often close at different times, so we need to hold the control down until they both stop. I might replace the old motor on the good end of the slide with the spare new motor that I have, on the chance that the motors are built slightly differently and providing different speeds. They are all 500:1 gearing, so the differences must be subtle.

–Gordon

[hvstorck]

Gordon,
Glad to read you're repair is complete. Great write up as usual!
Harvey

[gordonsick]

Harvey,
Thanks for the compliment.

BTW, I'm not completely comfortable with the C2 Schwintek controller for my slides. They have a tendency to stall and stop if they think the slide motors are overloaded. That is why you need the over-ride setting to close the slide when this happens. And, I found it very easy to push the slide in and out by hand, so the stall for an overload is a bit premature.

If I find that I regularly have to over-ride the controller, I think I'll replace it. Lippert now has a D0 controller and I think it has the same connections as the C2, so I would go with that if I continue to have problems.

–Gordon

[Super55]

Gordon, Thank You so much for the very detailed information on repairing your schwintek slide!! I'm (a DIY'ER) and planning on repairing mine as soon as the weather warms up. Once again Thank You!!

[gordonsick]

You're welcome.
If your rack is getting chewed up, make sure you have aluminum plates to make it roll more smoothly. FR is handing these out for free for the coaches that are having problems.

My slide still works smoothly.

–Gordon

[hvstorck]

Gordon,
Do the roller plates require Schwintek system to be adjusted or are they able to be raised 1/8 inch without a problem? Thanks as always!
Harvey

[gordonsick]

Harvey,
Theoretically they need an adjustment because they are 1/8” thick. But, FR didn’t suggest doing anything about it. I believe that Oscar has written that it doesn’t cause a problem.

Having said that, I replaced the Schwintek rack on the heavy (refrigerator end) and the new H-column didn’t have any holes drilled into the vertical H column flange, but it used the same holes for the horizontal racks as were on the original rack. That’s OK, because the only con concern would be with the vertical location of the holes on the H-column flange. I got to install new holes and everything went together nicely. The horizontal racks can be at the same height, because the compensating adjustment is made on the H-column.

They did ship me an H-column set for the light end of the slide, but I didn’t install them. Theoretically, there could be a problem with the extra 1/8” on the bottom, but I haven’t seen any problem occurring. If I was concerned, I could either install the new assembly on that end, or remove the screws on the vertical H-column on that end, and see if the holes had moved between the H-column and the coach. If they moved, I could drill a whole new set of holes for the H-column and everything would be back up to spec.

—cheers, Gordon

[hvstorck]

Thanks Gordon!

[gordonsick]

Looking over my last post, it occurs to me that I haven’t discussed the other important component of the Schwintek system, which is the V-Roller.

If you look at the bottom of a Schwintek rack, you will see a V-groove. The V-roller runs in that groove and is attached to the H-column flange by a bearing block. To examine the V-Rollers, pull the rubber flap to one side where the V-groove goes into the wall. You will see a white nylon roller that runs in the groove. It it is damaged by crushing or pulling the nylon off the bearing, you are about to have serious problems, if they haven’t already started. Schwintek sells the V-rollers separately, but replacing them requires the same procedure of removing and replacing the H-column and the racks that I discussed earlier.

The principle of V-roller operation is to hold the pinion “spur” gear in the H-column a proper distance from the rack. If it fails, the spur gear pulls away from the rack, and starts to slip. Gears get mangled and the slide stops working properly. So, it is a good idea to examine your V-rollers to preempt any damage to the rack.

The bearing block holding the V-roller and pinion gears has a fixed location vertically within the H-column, but is allowed to slide laterally on a “shoe” bearing. This sliding action is used by the V-roller to adjust the proximity of the pinion spur gear to the rack gear.

To address the subject line of this post, the introduction of the aluminum plates will lift the slide room by 1/8”, which takes a load off of the V-roller. That’s the good news. The potential problem is that this puts some slack into the V-roller’s job of holding the pinion gear a proper distance from the rack. It probably allows the rack gear to disengage the rack gear by about 1/16”, so the gears still have a lot to work with.

The disaster happens when the slide room lowers, which is our problem with the Berkshire. This overloads the tiny V-rollers, crushes them and things continue downhill from there.

[gordonsick]

Many of the previous posts in this thread have been about technical procedures that many Berkshire owners have no intention to deal with themselves. But, I suspect that many are worried that they may have a problem and they need to hire a repair shop. Moreover, some would like to get an early diagnosis of the problem so that the repair can be conducted simply by installing aluminum plates underneath the slide room.

This post is for you folks.

There are lots of other Schwintek slide issues that are discussed elsewhere, including motor failure and motor controller problems. I won’t discuss them here.

I will define the “Berkshire Schwintek Problem” as one that arises when a heavy slide is operated by a Schwintek mechanism, using support rollers for the slide room that run on a wooden subfloor. The problem may occur with other RV manufacturers, but I haven’ seen any posts about it. Moreover, the problem does not occur on all Berkshire Schwintek slides. My motorhome has 3 Schwintek slides and only one of them has the problem: my 16 foot slide that holds the fridge, microwave, stove, kitchen sink, kitchen countertops and dinette. That’s a lot of weight. My living room slide only holds a couch and has no problem.

Here are the the diagnostic steps to follow. It is best to do these before the problem appears, because it can save you a lot of money.

1. When you open a Schwintek slide room, look underneath to find some white nylon rollers on the coach wall. These hold up the slide room and allow it to move in and out. On a Berkshire that could have a problem, the bottom of the slide room is plywood covered by black fabric. Examine the path of the rollers on the fabric to see if they are digging into the fabric and wood. Pay particular attention to the end of the travel where the rollers hold the room up while driving. The road bumps exacerbate the tendency for the roller to dig in.

2. If the rollers are digging in, take a bunch of pictures to illustrate the problem and send them to the Berkshire warranty people along with details about your coach, VIN and stuff like that. If they agree there is a problem, they have been generally good about sending free aluminum plates for you to install. The installation is not too difficult, in contrast to the other repairs you might do on the slide, but you can hire an RV technician to do it for you. The installation consists of opening the slide and lifting one end with a jack to gain enough clearance to slide the plate in. Drill holes and screw them in place. Make sure that the screws aren’t on the path of the rollers.

3. This might not be the full solution to the problem, however. Your V-rollers could be damaged. The Schwintek mechanism has 4 aluminum racks with gear teeth at the ends of the slide: an upper and a lower one on each end. The bottom of each rack has a V-groove and a V-roller runs in that groove. The V-roller is a white nylon roller with a V-shaped cross section. It sits just behind the rubber gasket on the coach wall. Pull the gasket to one side and check whether the V-roller seems to be damaged. It could be crushed or pulled sideways off its center bearing. If it is damaged, you must immediately stop using the slide until you or somebody else can conduct the repair procedures I describe in earlier posts. You are likely to see a bill on the order of $1500 to $2000. To be clear, the purpose of installing the aluminum plates is to protect the V-rollers.

4. Whether or not the V-rollers are damaged, examine the racks to see if they have been damaged: teeth worn or burred. This will help you decide how many parts will have to be ordered to conduct the repairs. The labour procedure for replacing the whole H-column and rack assembly is the same as for just replacing the V-rollers. But, it requires more parts. Schwintek wants to know the exact serial number on your mechanism before they send parts. On my Berk, the serial number was hidden by other items, so I called FR service to get the details. They offered me a good price on a full set of parts ($1500 for both ends of the slides, including motors), so I didn’t bother going back to Schwintek.

5. If you don’t have a problem, relax and enjoy your day.
—Gordon

[Super55]

Gordon; Once again, Thank You for all of your very detailed information on Schwintek in-wall slides. You have given me the courage and knowledge to repair mine.

[gordonsick]

Let us know how the repair goes.
—Gordon

[CZNEDY]

Gordon, I am bringing mine back in for another slide repair. Everyone talks about the slide plates. I just can't get my head around how these help keep the slide out on plane.