Mounting linear actuators inside camper to raise/lower roof

[philos65]

I'm back working on my camper project and have four linear actuators I'm going to install to raise and lower the roof. I'll put them in the back two corners and up against the front wall in the corners. The actuators extend up to 30". I sewed the new sideliner of this old Keystone so the ceiling is 29.5" when fully extended - almost 80" of headroom. Here's the link to the actuators. I actually paid less than half on Ebay what Windynation asks for their actuators.

https://www.windynation.com/Linear-Actuators/Windy-Nation/Linear-Actuators-various-stroke-lengths/-/244?p=YzE9Mjg=

These things can be mounted in two different ways. The most common is with brackets at either end that attach to roof and floor or block raising the end from the floor. The actuator then is free to move a bit sideways or back/forth when raising and lowering the roof. I'm not sure this is a good thing as the shaft may bind. Worst case - the roof collapses while raising or lowering.

The other mounting method is to get brackets that anchor the shaft of the actuator to the wall. This insures that the roof goes straight up and down. The mounting brackets on the roof have enough play that a couple degrees off plumb shouldn't make a difference.

Each actuator will have its own momentary dpdt switch in a bank easily reached when you first open the door. Because I'll have two 40 lb., 245 watt solar panels on the roof, as well as two fantastic fans, the actuators are not likely to all go up and down at the same rate. Hence four switches. I can rewire if it turns out they all go up at the same rate.

MY QUESTION: Does anyone have experience installing and using these things? If so, what did you learn?

Thanks...

Jeff

 

[BFH4N]

How much current do they draw?

 

[Taku]

This is what I was thinking of doing to help lifting when we have our boats on top. I am looking forward to seeing how you work it out!

 

[Vic Harder]

I was thinking of doing this as well when I get around to rebuilding the roof on my Puma build out. Placement of the actuators may be problematic, as we have to leave room for the folding rooftop cloth. I assumed the lifters would have to intrude a foot or so into the camper?

 

[philos65]

Thanks Vic

Man - I hadn't even gotten to how the sideliner needs to fold in. Thanks!!! Luckily I put in oak cross pieces on the roof at appropriate spots to do this. Gives me something to do while drinking coffee this morning - sit in the build and continue to look at it, and imagine...

 

[rando]

I use a linear actuator to lift the roof of my FWC. However, I use it like the speaker lift that many here use, not hard mounted. You put it under the lift board on the ceiling, push the up button and it pushes the roof up. It works well for this application.

A couple of things to consider with electric linear actuators - they are not self balancing like hydraulic cylinders (such as the Alaskans use), so as the load increases the actuator slows down. Most of the higher end systems that use 4 corner actuators also use hall effect sensor to synchronize the position of all 4 corners to make sure the roof goes up straight. Otherwise there is a positive feedback loop, one corner falls behind, therefore the load goes up on that corner and that actuator slows down more, falling further behind. It may be a bit of an art manually controlling these to raise the roof equally.

Also make sure the thread pitch on the lead screw inside your actuator is sufficiently high that the actuator is truly one way. On mine, if the roof isn't all the way up (and the lift panels locked) once you kill the power to the actuator it will actually retract under the load of the roof. I assume you have some other mechanism to take the load and shear once the roof is up?

 

[philos65]

How much current do they draw?

They each need to be fused for 5 amps. Apparently they draw between 2.2 and 5 amps

 

[rando]

I was thinking of doing this as well when I get around to rebuilding the roof on my Puma build out. Placement of the actuators may be problematic, as we have to leave room for the folding rooftop cloth. I assumed the lifters would have to intrude a foot or so into the camper?

This is a good question. I also thought about hard mounting actuators to put the lid up more automagically, but couldn't figure this part out. The conclusion was that the actuators need to be in the middle of the camper (therefore in the way) or on the outside.

One possible solution was to mount an actuator to each of the lift boards on the ceiling using pivots, and install a socket on the floor. Use the actuator to push each end of the roof up, then pivot the actuator up and clip it to the ceiling to be out of the way. This didn't seem that much better than just manually positioning a single actuator thus I didn't do it.

 

[ntsqd]

I frequently use air cylinders for the various production tooling that I design for my employer. Operationally different, but functionally these aren't all that different from linear actuators. Fully constrained cylinders is usually not a good idea, much better if they can float at both ends and find their own alignment. Accommodating a spherical rod end at each end the actuator is usually a pretty simple design exercise, but sometimes the surrounding parts require gimbaling the cylinder at the end of the body where the rod exits from.

If the end not fully constrained, be it the body or the shaft, has the ability to float in all directions except for the operational direction then that can work too, but this can be a significant design challenge that frequently has unexpected nuances that frustrate the effort.

Once lifted I would rely on some other means to keep the roof up, be it the original lifting panels or some other fixed latch or lock. Alaskans use a spring clip through a hole in the shaft to lock their roof up and do not rely on the hydraulics being able to maintain the pressure.

 

[philos65]

I frequently use air cylinders for the various production tooling that I design for my employer. Operationally different, but functionally these aren't all that different from linear actuators. Fully constrained cylinders is usually not a good idea, much better if they can float at both ends and find their own alignment. Accommodating a spherical rod end at each end the actuator is usually a pretty simple design exercise, but sometimes the surrounding parts require gimbaling the cylinder at the end of the body where the rod exits from.

If the end not fully constrained, be it the body or the shaft, has the ability to float in all directions except for the operational direction then that can work too, but this can be a significant design challenge that frequently has unexpected nuances that frustrate the effort.

Once lifted I would rely on some other means to keep the roof up, be it the original lifting panels or some other fixed latch or lock. Alaskans use a spring clip through a hole in the shaft to lock their roof up and do not rely on the hydraulics being able to maintain the pressure.

What's nice about linear actuators (my beginner's understanding) is that the 225 lb. dynamic load for each actuator means I can theoretically lift an 800 lb roof. It will lift really slowly, but lift. The static load on the other hand, is almost twice as much as the dynamic load. Once the sidewalls are tight, the actuators should maintain pressure. That 800 lbs of lifting power is 1600 lbs of holding power.

However, because I've got 150 to 180 pounds to lift and lower, and it's not evenly distributed, I can use supra struts on the inside between the camper body frame and roof frame.

The idea is once the actuators have lifted the roof into place, I can then tension the sidewall with the struts where it might need tensioning I have a bunch of 36" struts that seem to do an excellent job holding up the roof, keeping the 30" sidewalls stiff, with no other help. I just compress the strut on the camper frame and place the upper end on the roof frame. I figure this is a two minute exercise I won't mind doing.

I think the racks on the roof I built will distribute the weight of the solar panels pretty well, but once lifted, it would be nice not to have any bow (weight) or flex (wind) at all in the roof frame.

 

[ntsqd]

Maybe you've seen the red bracket/beam on hydraulically lifted beds etc? Those are the mechanical safety prop for when someone has to get into where the bed coming back down would be very bad. Some back-hoes have a similar safety beam.

Linear actuators are not hydraulic, but I still would not rely on them to hold the roof up while you're under it. Our Hallmark's lift design uses what is essentially a linear actuator to lift the roof, but the mechanism it drives goes into a position where it is mechanically locked in the up position.

Do as you wish, but I would not rely on the actuators to hold the load up. Just because they can lift far more than what the roof weighs does not mean that they can support that load over a period of time.

 

[Vic Harder]

This is a good question. I also thought about hard mounting actuators to put the lid up more automagically, but couldn't figure this part out. The conclusion was that the actuators need to be in the middle of the camper (therefore in the way) or on the outside.

One possible solution was to mount an actuator to each of the lift boards on the ceiling using pivots, and install a socket on the floor. Use the actuator to push each end of the roof up, then pivot the actuator up and clip it to the ceiling to be out of the way. This didn't seem that much better than just manually positioning a single actuator thus I didn't do it.

Wait a minute... some FWC have their roof lift assist air shocks mounted on the inside on a diagonal, right? Could you not mount linear actuators the same way?

 

[billharr]

Wait a minute... some FWC have their roof lift assist air shocks mounted on the inside on a diagonal, right? Could you not mount linear actuators the same way?

Damn this could cost me money. I still have the two inside struts, they work so I have not changed to outside. I use the speaker jack in the front as I added 250w of solar. Going to wait and see how they work out. Two may work to lift the top. I have always lifted the back first and then the front. I ASSUME the linear actuators will not move unless powered. If that is the case I see a problem with only two. Might bind up if you need to do a push up on the back.

 

[Vic Harder]

Damn this could cost me money. I still have the two inside struts, they work so I have not changed to outside. I use the speaker jack in the front as I added 250w of solar. Going to wait and see how they work out. Two may work to lift the top. I have always lifted the back first and then the front. I ASSUME the linear actuators will not move unless powered. If that is the case I see a problem with only two. Might bind up if you need to do a push up on the back.

I am motivated as well. We have a huge 395W panel in the front and my maxtrax in the back. 80# lifts make this almost a none issue at this point, but we are adding a canoe this year.

I know they only had two inside, and moved to the outside version later. I reread the threads on lifters, including the Sticky one, and notice that some folks thought the inside ones got in the way of moving around on the bed.

I also wonder if that would be an issue with 4 of them mounted inside, two more to the front and two more to the rear.

And, can you get waterproof linear actuators? If so, mount them to the outside on the sides?

 

[rando]

I think using actuators like the inside mounted struts is probably not ideal - the struts are pretty close to the middle of the roof, so I think there would be a tendency to bow the roof if it had a heavy load. The horizontal load on the roof would also be pretty high when you first started lifting the roof as the struts are only a few degrees from horizontal.

There are IP65 struts (the windy nation ones Philos is looking at) but I am not convinced they would last all that long with full exposure to the weather and 70mph rain and snow.

 

[bajablanca]

I had a topper ezlift before my current fwc. While I wasn't a fan of the price/design of topper ezlift, the actuators had no problem lifting a very heavy fiberglass high top she'll with a beefy roof rack and surfboards. The windy nation actuators are not that beefy, I'm sure they can handle the lift but are a bit flimsy. I've been thinking about mounting actuators from progressive automations on the jack mounts???

 

[philos65]

So I sat a lot and looked at the inside of the camper and put the actuators in different places, in different configurations. It looks like the best way is to do it at all four corners of the benchs. Here's a picture of what I'm thinking.

http://jjolson.org/dir/index.php/Camper-Build/IMG_2871

There are two actuators in the picture. One is fully extended and one is fully retracted. There is just enough extra that the upper limit switch won't be triggered. Here's another picture

http://jjolson.org/dir/index.php/Camper-Build/IMG_2875

I'll put some oak 1/2" thick strips running fore and aft just inside the roof rail. I'll put the mounting bracket on that strip. The bottom of the actuator will be anchored by the same kind of bracket, but screwed into the bench.

Here's another picture of the two actuators.

http://jjolson.org/dir/index.php/Camper-Build/IMG_2876

I also got a bunch of struts and found they are great for holding up the roof and maintaining tension all the way around. This addresses the problem ntsqd in #11 above presents. The actuators will not need to hold up the roof. What seems advantageous about this idea is that with six struts and four actuators, there are 10 points holding up the roof and tensioning the sideliner.

http://jjolson.org/dir/index.php/Camper-Build/IMG_2877

http://jjolson.org/dir/index.php/Camper-Build/IMG_2873

http://jjolson.org/dir/index.php/Camper-Build/IMG_2878

I also got a cargo holder made to put horizontally across the bed of a pickup to hold things in place. This sucker works really well as part of a system to hold the roof in place. I don't think it'll be necessary, but its another way to tension that sideliner so high winds will rock the pickup and camper before affecting the sideliner/roof assembly.

http://jjolson.org/dir/index.php/Camper-Build/IMG_2874

As always, feel free to look at this and offer critiques, potential problems, etc.

Jeff...

 

[rando]

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?

 

[Vic Harder]

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!

 

[ntsqd]

FWC is the only pop-top that I've seen use shear panels. Do the ATC's? Our former Phoenix and our current Hallmark both use roof support systems with no real shear strength. Does not appear to be a problem. We had the Phoenix in a couple pretty serious wind/rain storms and shifting of the top was not an issue.