Mounting linear actuators inside camper to raise/lower roof

[philos65]

Are you not using the lift panels at the ends of the camper?

If not, then I think shear on the top relative to the camper could be a pretty major issue. Without the 'shear wall' formed by the lift panels, then there could be a tendency for the roof to parallelogram under high winds (aka Wyoming) broadside to the camper. I don't see what resists the roof being displaced sideways relative to the camper? When putting the roof up and down there may also be issue as there is nothing to align the roof with the camper once the fabric is loose. Maybe I am missing something here?

No lift panels. Once the roof is up the sideliner creates a tensioned box. As stated, four actuators and six struts will maintain hundreds of pounds of lift that will create the tension in the sideliner. I've had the roof up now for five days using only the six struts and one cargo bar and the wind has blown 40 mph+ a couple times. The whole camper rocks, but there is NO tendency for the roof to shift.

 

[philos65]

Still wondering about how the sideliner material will fold around the actuators. BUT, if you get this working, I can already feel my wallet getting lighter!

As I've envisioned it, the sideliner folds down inside the actuators. The oak strip running fore and aft between two or three of the roof cross members will hold the brackets attached to the roof far enough away from the sides that the sideliner will naturally fold down. There should be no pinching or bunching.

Note I said, "should." I think this will work. Once I put the oak strips on the roof it won't take long to test. I'll take pictures and report of course.

For those that have noticed and measured, how much distance do you think needs to be between the bracket on the roof and the sidewall? I have yet to have lowered the roof since I attached it to the body of the camper. I actually have no idea how many inches would be necessary so the sideliner isn't pinched. I'm thinking two inches will be enough. Any thoughts???

Jeff

 

[rando]

I stand corrected - maybe there is no issue with shear.

 

[ckent323]

Jeff,

It seems that you will have enough weight on the roof to have the potential to cause serious injury to someone standing in the camper in the event of roof lift failure. Perhaps you are a mechanical engineer and have this all well in hand but in the event you are not I offer the following thoughts.

If I were doing this I would seek out a structural analyst to calculate the live loads and dead loads and determine if the design is sufficiently robust in worst case conditions wind, snow, etc.

I just hired an analyst to do the appropriate calculations for 5 second level floor joists in my house that a "handyman" I hired got a little too aggressive on during some plumbing work and cut a lot of wood away from the 5 joists. I designed some reinforcement brackets and the analysis of those brackets plus the structural engineer's stamp on a formal report (the report and stamp added cost extra on the analysis package) cost <$600. Without the formal report and stamp it would have cost <$400.

I can sleep easy at night and not worry about the consequences of a floor failure.

 

[philos65]

Jeff,

It seems that you will have enough weight on the roof to have the potential to cause serious injury to someone standing in the camper in the event of roof lift failure. Perhaps you are a mechanical engineer and have this all well in hand but in the event you are not I offer the following thoughts.

If I were doing this I would seek out a structural analyst to calculate the live loads and dead loads and determine if the design is sufficiently robust in worst case conditions wind, snow, etc.

I just hired an analyst to do the appropriate calculations for 5 second level floor joists in my house that a "handyman" I hired got a little too aggressive on during some plumbing work and cut a lot of wood away from the 5 joists. I designed some reinforcement brackets and the analysis of those brackets plus the structural engineer's stamp on a formal report (the report and stamp added cost extra on the analysis package) cost <$600. Without the formal report and stamp it would have cost <$400.

I can sleep easy at night and not worry about the consequences of a floor failure.

I'm kind of chuckling here. I've torn my 140 year old balloon framed house down to the studs and joists and am slowly redoing everything - heating, electrical, plumbing, repointing the sandstone foundation - real stones - and getting rid of bearing walls to open up the space.

I get your concern, and appreciate you probably wouldn't go this route - actuators and struts. I thank you for your perspective. I just don't happen to agree with it.

As I stated above, the roof has been raised using six struts and one cargo bar for almost a week, and has twice gone through windstorms of more than 40 mph. The 80 lbs of solar panels I'll put on is not "likely" to change how sturdy the whole thing is, especially once the four actuators are installed. 10 points of support. Well over a 1000 pounds of static load capacity.

I will test the whole thing of course, and I'm pretty sure it'll all work... If it doesn't, and the roof comes crashing down while I'm sleeping, I'll come back here and share, and shake my head and say, "You were right."

Jeff

 

[klahanie]

Seems like you know what you're doing and have things well in hand.

I figured early on you were pretty committed so resisted posting any critiques or potential problems, despite the solicitation.

It's an Interesting idea and good to see someone taking it on. Will continue to follow.

 

[philos65]

My problem is I have always worked best in teams when it comes to "problem solving" and "doing stuff." This is very much a solo effort. Brainstorming is what keeps me going.

For example, right now I'm trying to decide which direction to have the actuators extend - forward for the front pair and back for the rear pair, or sideways for all four.

In the first instance, it seems it would be best to raise the front two actuators - raising the front of the roof til it snaps into place. This seems better because raising the rear first would mean you'd have to tweak/jiggle the front actuators because they're four feet back from the front of the camper. When the rear was fully raised, the front actuators would be extended six or eight inches or so. Lots of jiggling here.

The rear actuators will be only nine inches or so from the back wall of the camper. They'll actually hold the rear part of the roof in place while the front gets lifted.

Raising one side first, and then the other seems doable. Same principle as above.

I'm making a box to hold the four momentary dpdt switches - probably a metal electrical box used for switches or duplex receptacles. This box will have a handle (6" of 1/2" EMT?) with wires going through it and a split plastic casing to the four actuators and battery bank. That way I can stand outside the camper and raise the roof. It'll take 75 seconds at the fastest to raise half the roof. 750 mm at 10 mm a second.

As long as the sideliner is "snapped into place" (albeit really slowly) like the lift panels do on a factory rig, the lifting process should be the same.

Any thoughts on which approach might be better?

As I sat in the camper this afternoon, I also wondered about the "speed" at which the sideliner "snaps into place." A weakness in this approach seems to be that if a 60 mph gust hits the sideliner while it's taking 75 seconds to raise, then Rando's comment about wind shear might be a factor.

I sat there imagining a gust catching the sideliner when the roof was half raised and ripping out the lag bolts holding the bottom bracket of the actuator to the bench, or the screws holding the actuator bracket to the roof. The sideliner would keep the roof from flying away, but it would be a mess. Maybe this is a reason to lift it one "side" at a time rather than the front first, then the rear.

Thoughts?

Jeff

 

[rando]

Another thought, related to raising/lowering in the wind - what aligns the roof with the camper? It seems that even in a moderate breeze the roof will drift down wind when lowering?

 

[Vic Harder]

why not actuate all 4 lifters at once?

 

[philos65]

Another thought, related to raising/lowering in the wind - what aligns the roof with the camper? It seems that even in a moderate breeze the roof will drift down wind when lowering?

Good question... As I think about it, isn't it just like raising it? One end is taut while one end lowers. When the lower end is down on the camper body, anchored if you will be the lowered actuator, the other end can be lowered. Thanks for helping me t hink this through...

 

[philos65]

why not actuate all 4 lifters at once?

I'm sure I'll try it. But what I imagine is that the roof has no anchor when the whole thing is lifting - nothing to keep it from sliding left or right, fore or aft. All four lower brackets are bolted to the bench over the wheel wells. There is no rigidity at all to hold the roof in place.

I can imagine making slots on the jack mounts outside the camper, and carrying a 4' length of 3/4" EMT to keep it from shifting sideways. But nothing occurs to me that would keep it from shifting fore or aft when trying to lift the whole thing at once. Good question...

 

[rando]

Good question... As I think about it, isn't it just like raising it? One end is taut while one end lowers. When the lower end is down on the camper body, anchored if you will be the lowered actuator, the other end can be lowered. Thanks for helping me t hink this through...

With the normal camper, the lift panels set and maintain the alignment. Even with one end at a time, as soon as you drop one end, the side walls become loose and there is nothing to keep the roof from moving forwards and backwards or twisting. With raising it - the final position is determined by the fabric being equally taught all around, with lowering it I don't see anything to constrain the position of the roof relative to the camper.

 

[PaulT]

Search for “linear actuator with position encoder”. There are Arduino applications that could allow one to implement position & velocity control.
This is required to coordinate and synchronize the four position actuators to smoothly lift & lower the roof.

One could use one Arduino per actuator to control position and speed of each actuator and another Arduino or Raspberry Pi to close the loop to coordinate speed and position among the four together.

I used to program motion control systems in another lifetime. There would be significant work involved to make it work but it is doable.

Paul

 

[philos65]

With the normal camper, the lift panels set and maintain the alignment. Even with one end at a time, as soon as you drop one end, the side walls become loose and there is nothing to keep the roof from moving forwards and backwards or twisting. With raising it - the final position is determined by the fabric being equally taught all around, with lowering it I don't see anything to constrain the position of the roof relative to the camper.

I see what you're saying. When you lower one end, the tension in the sideliner lessens and the roof can wander.

I guess I'm going to have to test this. If one end of the sideliner remains taut, will this be enough to keep the roof fromwandering.

I wonder if by lowering one end, and having the two actuators lock it into place, snugging it to the camper body in two places, that wouldn't perform the same function as a lowered (or raised for that matter) lift panel?

 

[philos65]

Search for “linear actuator with position encoder”. There are Arduino applications that could allow one to implement position & velocity control.
This is required to coordinate and synchronize the four position actuators to smoothly lift & lower the roof.
One could use one Arduino per actuator to control position and speed of each actuator and another Arduino or Raspberry Pi to close the loop to coordinate speed and position among the four together.
I used to program motion control systems in another lifetime. There would be significant work involved to make it work but it is doable.

Paul

I found this in an earlier web search after someone mentioned hall effect sensors.

https://www.progressiveautomations.com/products/hall-effect-sensor-actuator?variant=18283068588099

I think this would work if you mounted the actuators on the outside of the camper. Wouldn't the fact that the actuator bottom brackets are free floating preclude use of something like this inside the camper? They may all rise at the same rate, but what would keep the roof from shifting in one direction or another during raising/lowering?

I thought about using the sidewall mounting brackets at the bottom of the page linked above. Because the roof goes up 29.5 inches, I'd've had to cut holes in the bench over the siderails in front and hang the actuator motors outside the camper. There's a space at the rear that would support use of these kind of mounts. Use of the rubber boots on the page above would make this doable I guess.

Honestly, it was the $1000 price tag for four of these that throw 30" that had me move on and search for less elegant and cheaper solutions.

Jeff

 

[rando]

You will have to lower the front end first as if you try and lower the rear end, the roof will pivot around the front actuators near the bed, and you will bend the roof (this could also be an issue if you tried all 4 at once and they get out of sync).

Having the rear end taught while you lower the front will provide some side to side stability from the liner, but nothing in the front to back direction - and once you start to drop the front end I feel like there will be a tendency for the whole roof to slide forward. Once this happens, I am not sure how you would recover.

Is there a reason you don't want the lift panels, or some approximation of the lift panels? It seems to me that this would solve most of the identified issues - shear, roof alignment and safety when the roof is up and is obviously a proven system.

I see what you're saying. When you lower one end, the tension in the sideliner lessens and the roof can wander.

I guess I'm going to have to test this. If one end of the sideliner remains taut, will this be enough to keep the roof fromwandering.

I wonder if by lowering one end, and having the two actuators lock it into place, snugging it to the camper body in two places, that wouldn't perform the same function as a lowered (or raised for that matter) lift panel?

 

[philos65]

You will have to lower the front end first as if you try and lower the rear end, the roof will pivot around the front actuators near the bed, and you will bend the roof (this could also be an issue if you tried all 4 at once and they get out of sync).

Having the rear end taught while you lower the front will provide some side to side stability from the liner, but nothing in the front to back direction - and once you start to drop the front end I feel like there will be a tendency for the whole roof to slide forward. Once this happens, I am not sure how you would recover.

Is there a reason you don't want the lift panels, or some approximation of the lift panels? It seems to me that this would solve most of the identified issues - shear, roof alignment and safety when the roof is up and is obviously a proven system.

No rational reason. The EMT solution is the easiest and most tried and true non-lift panel system. Maybe I can make it work. Hope rules!!!

 

[Taku]

Couple of thoughts. If you think it might be an issue without lift panels, or EMT, use just 1/2" EMT on one end, it may stabilize it enough for raising and lowering. One other thought (at least for lowering) is the inside air pressure could help stabilize and is pretty easy to control with the fantastic fan - I have done that to control the lowering when we have a heavy rocket box and canoe on top of our ATC.

 

[philos65]

Thanks for all the suggestions and brainstorming. I think I'm ready to install the actuators - once I finish wiring the downstairs of my house... I'll come back with results...

 

[m.r.h.]

Any luck with these actuators ?