Page BottomI couldn't resist it any more, after a bout of serious back pain and nerve pain in a leg again, i decided it's wasn't that i want a overhead lift, but i need one. I figure it will hold 500lbs (a 4x8ft sheet of 1/4 plate steel) just fine, and with bracing struts over the rails to stabilise it from twisting and add some strength, it should do 1000 lbs ok. I am putting a one ton 12vdc winch in the center of it.
Technically, a gantry has moveing legs to the floor supporting the overhead stuff, so this is really an overhead bridge crane.
A car that has the wheels the rails ride on. I'll replace the regular nuts with nylocks once the welding is cooled. It's laying there at the ends of one foot pieces merely for the purposes of picture taking. The two rollers have two ball bearings in each, and they lift the rails running left-right off the rails running up-down by a tenth inch. If the bearings fail, the rails drop down a tenth and not nine feet down to the ground. The two bolts sticking up have a bearing on each side of the bottom rail, to keep the car centered on it. There will also be a bearing to hold the thing down. In case you are wondering, i am calling it a car mostly because i first designed it as a separate entity, with the bridge floating on it, on swivels, for freedom in movement, accommodating irregularities in the track steel. Then it dawned on me that the steel alone was going to flex more than i wanted anyways, so now i am welding it onto the bridge steel.
Even with the rail mounted with the web vertical, the top of the flange isn't flat horizontal, so the bridge wheels don't sit flat. The solution was the tilt the bottom the rail in some, thereby tilting the edge up. Good example of why shims were invented! Had i not checked the thing over, maybe next week i'd be wondering why i was having bearing failures here.
Looking up at the end of the bridge while it's been run cattywompus. While this should never happen in practice, if it does you do not want the bolts holding those bearings to be sheared off. Leave some gap between those bearings and the rails, it won't hurt anything. Since i know the bridge can take this degree of misalignment and not fall down, i know i'll notice this amount of umm, cattywompusness(?) before anything breaks or it falls on me.
Click either pic to see a larger view.
A look up at the winch car undersides. It's positioned so the takeup on the drum is centered tween the bridge rails.
The space to the left of the winch is alloted for the shaft that runs the length of the bridge rails, to sprockets on each end of the bridge, to engage a chain there, and keep both ends of the bridge in sync as they move the length of the main rails on the "walls".
Well, i wanted that shaft to go in that space, but as things turned out, it was a lot faster in this situation to tack the shaft onto the outside of the bridge, as seen further down the page. I wanted more torque than the chosen motor could provide, and the space there wasn't enough to put a larger sprocket for it to drive and yet clear the winch car as it went by. I was not going to compromise on height above floor to hang it under the bridge either.
Click on the image to open a new tab with a bigger pic.
Here you see the three wheels or bearings at each of the imaginary corner centered on the winch takeup. On the left end of the very top bolt, you see a bearing wrapped in a 3/16 wall tubing to hold the car up, riding on top of the bridge rails. The next bolt down you can see a bearing on it's left up under the channel flange, to hold it down. In the event of bounce or tilt, i don't want the car to fall off. The bottom bolt, tucked up in there, holds a bearing on top of the steel it's thru, positioned to ride against the inside of the channel, to prevent the car twisting around a vertical axis.
You may be asking why only one bearing of the three is wrapped in a seat/housing, and the answer(s) is(are) simple: The top bearing is in contact full time and under load, the holddown bearing should never be in contact, and the side push bearing is in contact at most 50% of time and with very little load. Not putting the bottom two bearings in a housing saved time, money, and space.
Click on the image to open a new tab with a much bigger pic.
Here's the look out my front door so far. The bridge rails are 1/2 way down the side rails, and the winch car is centered on the bridge rails.
Yeas, the rails are on the thin side. I didn't buy them to use for this, i bought them to use as boat ribs, Then screwed up my back again, and not only needed steel i had already paid for, but already have, and was light enough to use. And i figure, what the heck, i can probably use the crane on the boat for moving stuff about too, so it's not wasted. I figure lots of heavy things will be in storage in the amas of the trimaran, or in the bow of the main hull, pulled out to do things as needed, then put back.
I pulled it with the rope. It will be motorised so i can be concentrating on whatever i am moving with the crane, not thinking about falling over something as i pull on a rope.
Yes, the rail in the back slopes up a lot, it's still hung by a chain from the roof at this time, the crane is still under construction.
Click on the image to open a new tab with a bigger pic.
Fit-up of an end plate for the sync chain and long-wall drive chain thing. I have no clue what it's special trade name is. The shaft isn't on the sprocket as it will be.
The little jig to make chain support brackets the 34ft length of the wall rails. The less slack in the chain caused by gravity, the less slop there will be in placement of the bridge.
Click either pic to see a larger view.
Length of rail without chain in it. The little clips are a foot apart. I had to play with the brightness on this pic to even see the clips.
A 34ft length of rail with chain. It's a lil squashed to fit the space, click on it to get a fullscreen view in a new window.
Click either pic to see a larger view.
Test fit of shaft to one side of the bridge. The pic is a lil squashed, but this is one of those pics where it doesn't matter how you take it, it doesn't look right in 2D.
Closeup of shaft in end plate with chain on it. The chain is picked up, run over the sprocket, and put down almost where it was picked up from. It's used like a rack and gear system, not like a garage door opener system.
Both of these pics emphasise the red to make the chain stand out more. Click either pic to see a larger view.
This is the entire drill, with leads to connect to a small 12v riding mower battery. I can drill all day long on one mower battery, instead of 10 minutes on one oem battery pack. I'll put just the motor and gearbox, replacing the chuck with a pinned tube, and a 3/8 drive wobble adaptor. It concerns me that the gearbox end is plastic. And window screen to keep the mud dauber wasps from filling the motor with dead insects, larvae, and mud.
This gives the drill 2.5:1 torque increase and rpm decrease, both features i needed. Torque is always in short supply on low priced projects, and when moving heavy steel swinging on the end of a cable, you won't want fast speeds. Naturally i will have a variable speed on it, since the drill came with that. The pink is bondo to fill the bike sprocket slots and holes, which i just didn't like the look of. I'll paint it all in rust preventive later.
I later winched the heavy growlbox arc welder up on the crane, to measure deflection with a load on it (tho the number is meaningless given i don't know the arc welder's weight). The lil drill had no strain moving the bridge crane with the weight of the arc welder pulling down and ~60lbs of side force of me on the ladder against it. Click either pic to see a larger view.
This is the relay controller for the winch. It's 12v riding mower starter relays, wired as an H-bridge, or double pole double throw. Basically, it can apply the 12v from the battery to operate the winch in either direction. The wire is 10awg solid, it's between two flat washers on each terminal, and there's a lock washer under each nut. The chassis bolts have nylocks. Red and black go to the battery, white goes to the winch leads. The relays allow me to run any length control wire, or a wireless controller.
I am not suggesting this is the best way to build anything, but it's working this time for me here. Clicking on the picture gets you a bigger picture.
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