I am finishing a remodel of an older home. Per the architects direction we installed hardwood flooring over a trap door that accesses the basement. The door had carpet over it previously. It was essentially a sheet of 3/4″ plywood with a 2×4 frame, now we added a layer of maple 3/4″ T&G hardwood flooring. The problem is the door is too heavy to lift without rupturing a nut. Any ideas on some sort of hardware to assist. I was thinking that a cylinder like the ones used to hold up the heavy rear doors on minivans would work, but no luck looking in Northern or Grainger. Hmmm, wonder why the architect didn’t think about that? For what it’s worth I did suggest to the homeowners that we build a better access prior to starting. The boiler, water, and electric all are in the basement.
Thanks
Bill
Replies
Where's the hinge? If you can attach behind the hinge, you can hang weights to counter ballance some or all of the weight.
I'm guessing that the door is hinged right at the edge. What you need to do is get the door out and get an approximate weight. This will tell you how big a hydraulic lift cylinder(s) to get. If the door weighs 80# and you put a pair of 18# lifts in, they wont last very long, like as not. For a source, you might want to check roofing suppliers, as they often stock replacement cylinders for roof hatches. Check bulkhead suppliers, too.
I bet you could fab something pretty slick with a pair of the gas pistons they use for trunk lids on cars. Most auto parts stores have a variety to choose from. Just off the top of my head I'm thinking that the models suited for hatchbacks would be strong enough.
a auto parts store has carries the gas lift trunk and hood cylinders.
You could also use a shaft and a coil compression spring mounted between the trap door and the frame. One on each side of the door. the frame side use a piece of heavy angle iron the shaft would slid through a hole in the angle iron bolted in the frame . the one on the trap would just pivot on another piece of angle iron. you will have to play around to get the angle worked out.
The only thing is the shaft will protrude in to the crawl space when closed .
Edited 10/6/2003 11:24:25 PM ET by fredsmart
Interesting problem.
Boat stores sell gas cylinder lifts as well. The advantage over auto stores is that they also sell any number of brackets to attach them with.
I used to rent a house with a trap door. The door also served as the floor of a pantry. It was probably 3x6, and really heavy (hinged on the side). The lift assist consisted of a rope running over a pulley with a heavy cast iron weight attached. Think the architect would go for a 'rustic' look? The weight could be some sort of cast iron antique from the salvage store. Or maybe a decorative container filled with sand or cement... perhaps a nice copper chain instead of the rope, and a funky antique pulley block... Spin it into a rustic feature!
One other idea- the fellow who asked where the hinges were was onto something.
If you were to install a long lever arm to the underside extending away from the hinge side, pushing the arm down would open the door. The arm could be 'pushed' down with a compression spring, or pulled down with a weight, or a tension spring (like a garage door spring, perhaps). The hinges would need to be beefy to handle this sort of 'double' stress.
McMaster-Carr has them. http://www.mcmaster.com Search for "gas springs" from their home page. They take credit cards and ship same day at no extra charge. They stock over 100 different sizes.
http://www.mcmaster.com/
go to page 1052
Strong words indicate a weak argument
I'll concur with the mcmaster recomendation.
The major advantage to mcmaster is that you know what load rating the cylinders are. When I had to find some for a mechanical design for work we found that while autoparts stores sold a wide variety of gas springs, they had no load info on them. Nor would the manufacturers of the brands they carried give you any load info (due to lawsuit fear if you used them incorrectly). All they'd tell you is what ones were apropriate for different trunks, hatches, ect.. Oh, also much cheaper then at the auto parts store.
They even sell variable force ones. These allow you to drain off some of the pressure to reduce the force (of course, they're expensive, and you only get one chance to set them right).
Another option might be to replace the 2x4 frame w/ plywood over it with a lightweight frame made of alum channel or tubing. Attatch the wood flooring to this and weight will be greatly reduced. But, you didn't say how big the hatch was, this'd work good for a 2'x2' hatch, but not so well for a 3'x6' hatch. If it doesn't need insullation, then the trapdoor could be much thinner w/ the door sitting on a frame on all 4 sides when closed.
Wow, McMaster has a great guide on how to select a cylinder, and an extensive selection. All I need to do now is go to the job and measure the mounting and pivot points and plug them into the formula. I'll probably get the adjustable force spring as I don't know how to weigh the door. I tried to open it today and man is it heavy. It is about 4'x8' for whomever was asking.
Thanks for the help
Bill
Well, if you can't take the door off to weigh it, you can weigh it in place. Open the door, put a board across the open end with a bathroom scale on it. Close the door on the scale and note the weight. If the door is symmetrical in construction, the weight of the door would be about double what the scale reads.
When mounting the spring(s), make sure the mountings are solid. The force will be considerable.
Wow, that's a big trap door.
I just drew a quick 2x4 frame 4'x8' in a solid modeling program w/ a 1.5" thick top plate. If made out of fir it'd weigh about 210 lbs. if of oak about 280 lbs. That's with no insullation, bottom skin, fasteners ect, but I'd guess your panel weighs 250 lbs. or more.
Really reinforce your gas spring mounting points. Huge bending forces will result if someone drops or throws the door shut, and then stands on it or worse kicks it to get it to close even faster. Also, you'd best have some solid hinges on this door or they'll pull out. And, the hinges best be attatched to something solid also. Also, when you put two springs on the door you'll be adding 2 large point loads. If you don't reinforce the joints good, by adding some L-plates on the bottom side with some good screws to tie the corners together, then a layer of plywood on the bottom, or something similar, they'll pull the frame apart over time. I'd really want to beef up the structure and the attatching points of the springs which of course will add more weight, so plan for it.
It might be simpler to get a new steel frame welded up and attatch the wood flooring to that instead.
Ideally you'll want it so you actually have to push the door a bit to close it. Just before the point that the springs have enough force to crack it open by themselves.
trapdoor
What happened? Have you given up? How did you solve your problem?
We are involved in the same circumstance, automotive air cylinders seem inappropriate since there travel length is too short. Employing instead a scissor leverage system with counter-weights.
trapdoor
What happened? Have you given up? How did you solve your problem?
We are involved in the same circumstance, automotive air cylinders seem inappropriate since there travel length is too short. Employing instead a scissor leverage system with counter-weights.