A strong, simple workshop crane

Here's my implementation of a 'Corner Crane', the design of which may interest others who need some heavy lifting performed in a workshop (build at your own risk though - these things can be dangerous if not done right).

Its corner fixing works on the same principle as the keystone in an arch, but it uses the idea horizontally rather than vertically. It took about a week to prototype and make from 'free' scrap that I had around the place. I tried aluminium scaffold poles first but they were too flexible and appeared to take a 'set' after a few heavy lifts, whereas steel ones just spring a little and then hold firm. The crane was installed originally to help move the body casting and innards of my rebuilt Astra mill from the bench onto its stand (est. 150 kgs), but has since come in useful for all kinds of weighty objects. I guess it would be ideal for lifting heavy models too, but I don't have any to try it on as I'm still 'making stuff to make stuff', like the half-finished Worden tool grinder you can see on the bench.

Crane ready to take a load
Here the winch is swung out ready, for instance, to un-ship the Astra's vertical head. The wide angle lens makes the ceiling look rather tall but it's only 7' high in reality. Even doubled for extra lifting capacity, the winch cable will drop to well below floor level.

Crane in action
An example of the sort of thing I used to break my back lifting onto the bench. Now it's all over with the press of a button - the remote hand control has quite a long cable (coiled around the winch in this pic), so I can stand well clear when necessary. The crane is also useful for just swinging things round on the bench, or flipping them over to work on another face.

Crane parked
Here's where it's normally 'parked' - completely out of the way in otherwise 'dead' space. As you can see, it's constructed from a couple of lengths of steel scaffold pole, locked together with chopped up and modified scaffold clamps. The vertical pole rests on the bench top just out of sight in the corner (see later pic). The ceiling junction box shows where I moved the lamp onto the wall so I could get maximum height for the jib pole.

Top clamp
This top clamp is the sawn-off half of a pole-extending clamp. There are a number of 'patterns' of these clamps - I chose the type with flats on one side so I could use them to clamp the brace as well as the scaffold pole. The brace is from an old garage up-and-over door (I knew it would come in handy one day!).

Right-angle clamp
This in-line right-angle clamp was made by halving and reversing a full clamp and then welding the pieces together on one side only, so that both halves could still spring when tightened up. I'm surprised there isn't an 'official' form of this type of clamp - the only right-angle ones I could find were all offset which would have meant moving the upright about 6" further out from the corner to allow a full 90 degree swing. This in turn would have needed a much more complex wall bracket (see below). Obviously, all the clamps have to be wound up real tight for safety.

Wall bracket
This is the all-important wall bracket, made from a couple of pieces of 3/8" x 2" plate welded to the tips of a reversed half clamp (here I used a pattern of clamp with symmetrical curved sides - see below). The little messy brace pieces were an afterthought to prevent flex when the arm is swinging a heavy weight - they may be unnecessary but better safe than sorry. They are just two lengths of scrap angle jammed into the space and welded. The opposed, expanding wall-bolts effectively jam the bracket in place in the corner. The only way it can pull off is by hauling three or four bricks through the corner, which is as difficult as pulling a keystone out of an arch. The original plate holes were changed to a staggered pattern to avoid any danger of the bolts expanding in the same line of mortar. They also align roughly with the line of force that the crane applies. The bearing area was pre-greased, so the nipple is probably superfluous. A certain amount of clearance is needed in this bearing (about 1mm) as the bar flexes naturally (and safely) under load and the bearing needs to be able to accommodate it. I found the clamp showed just the right amount of clearance when in its relaxed state so I just welded it 'as is'. The brace clamp underneath is the other half of the one on the top pole.

Base bearing
This is the plain base bearing which is really just any piece of plate with a small slice of clamp welded in place to hold the pole away from the wall. I slipped the bottom half of an old BSA steering head cone bearing under the end of the pole, but I think I could just have left the squared end to swivel on the greased plate. The crane swivels smoothly under finger pressure, even when fully loaded. There's an upright of 2" x 4" timber in the corner under the bench which transmits the load straight down to the concrete floor.

Expanding bolts
The expanding bolts I used were 10x100mm from the local diy multiple. The right-hand one shows the correct size but it's a stud that I bought before I realised I couldn't get the bracket on with studs in place (duh!). On the left is an example of the style of bolt (but too short). I assembled two bolts on one side of the bracket, inserted them in the wall, expanded the sleeves and then withdrew the bolts before performing the same operation on the other side. This left the jammed, expanded sleeves in place so that I could repeatedly offer up and 'adjust' the bracket to suit the out-of-square corner. Note that the plate holes need to be the size of the inner bolt, not the outer sleeve. The plate's thickness replaces the plastic sleeve you can see under the bolt head.

250kg winch
This is the single-phase winch that I bought new from a trader on eBay.uk for 99 pounds. He often has them on at this price, but with occasional breaks in supply. Machine Mart do an identical one for rather more. I use the pulley doubled up to get the half-speed 250 kg capacity. The straight 125 speed is a bit too fierce for delicate lifting and placing of heavy loads. The original hook on the 250 kg pulley doesn't swivel (unlike the 125 kg hook which can twist on its cable). I needed the hook to swivel so I swapped it for a similarly rated swivelling version from a cheap lever winch that I happened to have (came from a car accessory shop).The square mounting brackets on top of the winch wouldn't quite fit round a scaffold pole but I was able to dish them slightly to achieve a good loose fit. The winch can slide in or out a foot either side of the stop screw you can see threaded into the jib bar.

Even without an electric winch, the jib could be used with a plain pulley system, a simple chain winch or the lever winch that donated its swivel hook. Overall measurements of the crane are: top bar 52", vertical bar 53", wall bracket fitted 12" down from top corner (to ensure it has a sound course of bricks to bite into), bottom bearing 31" above floor level, brace is 3/8" x 1 1/2" x 32" and shows no sign of flexing, underside of jib bar to raised portion of bench is 44".

If anyone decides to knock up something similar, remember every setup is different so you'll need to do due diligence in judging your own safety parameters and calculations and welding abilities etc. I definitely can't take responsibility for anyone else's setup or workmanship. Having said that, this crane has performed faultlessly from day one and I now use it regularly without giving it a second thought. The key features are the 'jammed' corner bracket set in a sound brick wall, load transmitted to concrete floor, strong triangulating brace for upper arm, steel scaffold poles of limited length and use of a proven commercial winch.

neil f, 2003-2018.
web dot master at riscy dot uk

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