Raising the roof...
I recently acquired a "pop-up" camper and, due to my age and infirmity, all of the popping is pooping me out!
I need to elevate the ceiling two or three feet -- from a starting height a bit under 4' to an extended height a bit above 6'
I'm wondering whether a hinged pole would provide some degree of leverage and make the job easier.
Roughly speaking, I envision two 3-foot lengths connected with a strong hinge. By placing one end at a strategic point on the ceiling and the other centered on the floor, I wonder whether tugging at the fulcrum to "lever" the roof up would be easier on my poor body than trying to push that heavy roof straight up from a crouched position.
I'm a real amateur at geometry, trigonmetry, physics and (most definitely, engineering), so I have no clue regarding angles and force, etc.
I have estimated that the fulcrum would be at about 80 degrees at the start, and 180 (of course) when fully upright. It seems pretty certain that the lower that initial angle, the less leverage benefit obtained (assuming there is a benefit in the first place).
I hope this inquiry catches someone's fancy. I suspect that it's a pretty simple (maybe even dumb) question; but it could make a big difference in my life as a wanderer.
Thanks in advance.
Last edited by WanderingDave; 09-03-2011 at 03:47 AM. Reason: typos
Welcome to Engineers Edge!
I'm having a visualization challenge today... If you don't mind, could you post a picture of your pop-up camper mechanism?
The following is the instructions for posting a picture..
http://www.engineersedge.com/enginee...e-Instructions
Hi Dave and welcome to the forum. Nice First name by the way.
OK, what you are describing is known as a toggle. A toggle can be a fantastic leverage advantage mechanism, but only through part of it's travel. The rest of it it can be a large disadvantage and that's where you are starting from. At the start, it would probably be harder to lift than the roof itself. As a toggle approaches the 180-deg (straight) alignment, the mechanical advantage rises dramatically and in fact at 179.9999-deg it is approaching infinity.
Sooo, we need to think of something that will work for your situation and at my age, I know why you are looking for something easier.
Do you have a pic or two of the metal levers that support the roof on it's journey skywards? Since the levers already exist in somewhat of a toggle arrangement (I assume), we may be able to make something to assist their travel.
Can one end go all the way up before the other end has to start moving? Or, must it be raised somewhat level?
What sort of budget do you have in mind? Electrics and hydraulics can go a long way in assisting the lift. An acceptable budget range will help us define the motive power.
Do you always open it up campgrounds? Why? Well, campgrounds have hoses with water pressure (hydraulics and free supply, well kinda).
I love the way your minds work. We need some engineers in politics!
I can describe the roof-raise mechanism, but a (moving) picture is worth a million of my non-tech-writer words, so I invite you to view the first minute or so of an online (YouTube™ video): http://www.youtube.com/watch?v=qAvHUM1voUM.
The camper in the video has an overhang (cab-over) element that requires an extender; I do not have that disadvantage. I am disadvantaged by a much lower ceiling (while the room is down) which makes it very hard to "get under" the lift weight.
There are mechanisms (gas spring lift assists) that handle the problem quite elegantly. These struts can even be attached to the exterior of the shell so they don't invade the living space. As a very consistent bungler, however, I'd need to have them installed by someone with skills -- and there would be the cost.
My vision was for two pieces of lumber or light metal connected with a strong hinge (caps on the ends to protect ceiling and floor) that would "toggle" (thanks, dPink) the roof in place (or at least get it up where I could shift position and lift without an asymmetrical strain on my back).
Avoiding complicated and powered solutions with many moving parts is a very high priority for me (not as high as avoiding back injury, of course). I bought a "shell" camper -- no stove, refrigerator, furnace, sink, water tanks, etc. I'll use the traditional camp stove, ice chest, etc.
So, I guess my main question relates to the amount of force required as the angle of my toggle decreases from 180º to 80º or 90º. (Note: I might end up staging the lift, using the toggle to gain enough clearance for me to get in position to complete the job unassisted.
Based on your input, I'm GUESSING (I know you folks don't approve of such things) that the force requirement increases exponentially as the start angle decreases. A formula or table indicating that range would be just great.
By the way, a solution others have employed is the use of a crank-operated "speaker stand" -- a jack designed to lift 100 pounds of electronic into the air at rock concerts. I'm avoiding that solution because of cost (around $75) and because I think I can make other uses of my hinged pole – either inside my rig or outside when I'm parked, particularly if the hingepin can be removed and i have two, sturdy 3' long sticks.
OK, more info than you need... ☆
Hi Dave,
Something like this might work for you using 2" x 4" and a gate hinge. Make the vertical post about 4" shorter then the lowered floor to ceiling height.
The colored lengths are just to indicate rotation movement, you would only need one vertical (blue) and one horizontal (red).
The formula for mechanical advantage for your toggle setup is
MA=0.5H/sqrt(9-(H/2)^2)
H=instantaneous height
For H=4, your starting point,
MA=.89
For H= 5
MA=1.5
At H= 5.5
MA=2.25
As H goes from 4 to 6, the MA increases as Dave mentioned and reaches infinity at the end of the rise.
So, if you are strong enough to start the motion with 10% more than the vertical force you used before , you will eventually be rewarded with a modestly larger MA for most of the stroke.
Just noticed a better representation
MA=tan(.5*@)
where
@ = the angle between the links.
I think I may get it; but let me try to put it in my (less precise) language and see if I'm close...
First, I've attempted to create a new graphic that represents the fact that the toggle has to be rotated a bit so the start and finish positions of the two ends remain fixed on the ceiling and floor (and so the toggle is perpendicular at the end of the motion).
toggle.jpg
Finally, if I understand the math (and chances are that I do not), the mechanical advantage at the start (.89) is actually a bit of a disadvantage (assuming 1.0 would be equal force required horizontally to achieve vertical force), but that once I've lifted the roof 18 inches, I get 2.2 units of lifting force (vertical) for each horizontal unit I apply to the toggle.
I put Zeke's formula (the first one) into my spreadsheet and got pretty close to the same results (even including Dave's infinity at vertical):
MA=0.5H/sqrt(9-(H/2)^2)
(H=instantaneous height)
Hgt --- MA
4.0 --- 0.89
4.5 --- 1.13
5.0 --- 1.51
5.5 --- 2.29
6.0 --- #DIV/0! ☆
I'm encouraged.
Thanks so much. If anyone can advise on the second point (above), I'd be grateful. I'm not sure that being able to push down on that tail will generate a significant benefit over pushing horizontally at the hinge.
Last edited by WanderingDave; 09-03-2011 at 06:57 PM.
By George, I think you have it.
The idea with my sketch is that the top end could have a wad of towel or something and slide on the ceiling as it is coming up. In fact when I was drawing that I thought about a caster with rubber wheel at the top. Also, the handle end of my sketch can be longer than the part past the hinge and give you more advantage at the start where you will need it.
I like the rubber wheel idea. I'm not sure it's best to begin the lift very far off-center, but I can easily test that idea. And I need to make sure there's a good path for the roller to traverse.
On the other hand, I was considering affixing the kind of "feet" you see on ladders -- with a pivoting rubber end piece. One on each end of the toggle would give some grip to the surface while protecting it at the same time. Check out my current version (I'm growing attached to it). It seems to be simple and to really exploit the leveraging factor while moving my point of contact right up where it should be: where my hand would be if I were lifting manually.
I'm enough in to this whole idea that I think I may be ready to invest in a couple of 2x4s, a gate hinge and (if they're not too dear) a pair of pivoting feet. Add a half-dozen or so wood screws and that should be the entire parts list. If works according to plan, I'll share the credit with you and Archimedes.
And if others choose to adopt the notion, I'll ask them to refer to the invention as "Dave's Toggle." How does that work for you?
This has been good fun. I've learned a lot. Thanks so much for your help and teaching.
TOGGLE2.jpg
Yup, that should work, providing the arc of the long beam does not contact the ceiling before sufficient raising. I still see the possibility of the "feet" sliding, but hopefully some grippy-rubber will prevent that.
Happy to help, a rose by any other name would still be a toggle!
I'm sort of thinking the sketch you have might tend to want to bind because it will tend to want to push it sideways... or as shown in your sketch... it would try to push the roof to the right or toward the cab of the truck?
Be nice if you could be pushing down on your lever instead of lifting up on it. Easier to hang on it and use your weight instead of lifting. Maybe just flip your gadget upside down...?
If the roof "catches" when all the way up as it appeard to in the little flick... You might be able to put your fulcrum in the middle of the floor or just a bit toward the door, and raise it all at once from outside the door. Lever starting out poking out door up high and on the floor inside with a hinged arm pointing up and long enough to just fit under the roof. (Like a framing square)... that is hinged at the square joint and the longer leg of the square is long enough to poke out the door and the shorter leg is short enough that when flipped up it just fits under the lowered roof. Your pivot point is through your fulcrum and near the end of the long leg of the hinged square. You stand out side pull down on your lever and the roof raises. Pieces of rubber stapled to your push points should keep your push points stuck in place.
The angle of the lever that's shaped like a sqaure will become greater as it rises and allow the short end of the lever to stay put and lift straight? The weight of the board hanging out the door ought to keep it in place until you get out of the thing to pull down on it. Or you do one side at a time and when you have it pushed down and the roof is up just stand on the end of the board to finish the stroke or latch it?
I haven't tried to get a CAD sketch loaded into a thread yet...
Follow me? Stand on the board while you push up?
I think that's why the big guy tends to give us all bigger guts when we get older. This way we have the few extra pounds to lossen bolts and such by laying down on our cheater bars, where when we were younger we'd use our ******s.
Good Luck!!
Bob
Just got a chance to look at your new setup and find that if your force on the link remains perpendicular to the long link, you get simply
MA=L/a*sin@
@ angle of upper link to the vertical
L length of long link
a length of the upper link
So, if , say L =1.5*a,
I get an initial MA=1.5/sin(48)=2.02
which of course increases with decreasing @
Curiously, it says that if you kept the original configuration where L=a
you initially get
MA=1.34
Last edited by zeke; 09-08-2011 at 01:22 AM.
OOOH, my brain hurts
I wonder if I EVER had the capacity for this kind of stuff.
Being hopelessly left-brained, I have a very difficult time visualizing things. This darned device only has two parts, they have two dimensions in common and are connected, for crying out loud. But I still can't get my mind straight (where is the hinge oriented? which end is up? which way is up?).
The bottom line, though seems to be that I'll gain an advantage from leverage -- an advantage that will increase toward infinity as I approach full extension; and I'll be able to reduce the strain on my back (and that's the whole idea).
I now have the lumber (went with 2 X 3 stock cut to 4.5 and 3.5 foot lengths. I'm going to cut a notch in the top member so it will seat against the push panel and, hopefully, not slip; and I'm going to bevel the other end to allow the hinge to rotate beyond 90º.
By the way, I've already thought of another possible application of the toggle. If I set the extended length to a couple of inches above the resting height of my camper and apply a toggle to each rear corner, I may be able to eliminate the rocking I now experience when I move around inside my rig. This kind of "toggle jack" could attach to existing brackets, held in place with two bolts (the first would allow swiveling as the toggle is straigtened and then the second would move into place and could lock the device down.
I'm not sure I really need these, but if the final roof-lifter could double as one of two jack stands... Gotta love multiple use devices!
As one might guess based on my left-brain nature (described above) I'm not a bit handy with tools. So this little adventure is great fun for me and if it actually makes my life better, I'll feel very proud of myself.
Thanks for the help. If I survive the experiment, I'll post a photo of the outcome(s).
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