How heavy ?

I was thinking the other day about how much weight I am lifting when I move something heavy around.

I have a Viceroy Denford wood lathe with a long bed which I could never lift off the ground and so to move it I took it apart lifted the bed at one end, the other end being on the floor and shuffled and dragged it.

So if the bed is X lbs what am I lifting if one end is on the ground and I lift the other end ?

0.5 X lbs (Assuming that the bed is the same at both ends. If vertical with one end on ground, nothing)

Edited By Paul Janes on 18/01/2023 10:48:54

You would be lifting half the weight initially but the weight/effort would diminish at your end if you kept lifting until you had the lathe bed standing on its end on the floor when the weight/effort would be zero for you. I'm not sure if the change in weight/effort is linear across the arc from horizontal to vertical, maybe someone else can answer that.

Fred Dibnah deduced that dragging was used to build a lot of our big castles and cathedrals (walls etc) because it was so much easier and faster than a medieval crane

So most of those big stone lumps were dragged up slopes made of dodgy wooden scaffolding

+1 on half, assuming the bed is roughly the same all along and not a great heavy lump at one end like a headstock.

Standard way to weigh a motorbike is put one wheel on the bathroom scales and note the reading. Then do the same with the other wheel. Add them together and you have the total weight of the bike.

The tailstock end is way lighter than the headstock, even for a wood lathe. One should also be careful if as implied in some text above ( though not in the OP's move I think) if you are upending something while it is on its legs. The cast legs will not like the sideways stress and the often single bolt from bed to cast legs (as in eg Drummond) will break.

Remember the lever.
Say a 2x4 vertical with top just under bed height of a lathe on its legs and 6 inches away. Then a handy 3 ft 2x4 resting on the vertical and under the bed gives you about 5 to 1 advantage. Once lifted half an inch you can also swivel the job with a sideways movement of the lever. This is how stoneage man built his Henge to avoid having to hire a JCB.

I used a similar method to Hopper's to weigh our rather large black Labrador. Needless to say, he wasn't very happy at being asked to sit on a wobbly plank. I placed one end of the plank on the bathroom scales and the other was suspended from a spring balance. Add the two readings together, and the dog weighed 105lbs.

Peter G. Shaw

If at all possible I prefer to use rollers and crowbars than mere tea-and-cake fuelled me.

I think Fred Dibnah did the Mediaeval masons a disservice there. There are plenty of contemporary wood-cuts showing their techniques, and those included lifting-gear of various types. The ashlar and decorative stones, and the massive roof trusses, were worked at ground-level; and the builders would not have wanted to damage them by dragging on rough surfaces. (The trusses were built to templates on a flat floor, then with the joints annotated by scriber marks, dismantled, lifted in parts and assembled in place.)

Though it is Tudor, not Mediaeval, I have seen displayed a lovely painting in a psaltery that Henry VIII gave to one of his wives. I wish I could give a reference to it.

It shows the building of the fabled Tower of Babylon, and despite the rather wonky sky scene and the OT Middle Easterners wearing "modern" NW European clothes, it illustrates building tools the artist would have seen used. Some of them still familiar.

The scene includes a two-drum, two-rope winch being used to raise a block of stone to masons on the scaffolding above. Why dual I do not know. It might be for weight capacity and safety, but could also be the artist misunderstanding some form of differential windlass.

Mediaeval sea-farers would have known blocks-and-tackle, and it's very likely so did their contemporary Master Masons. Dibnah organised from examining a single painting, a successful reconstruction of how the original "Iron Bridge" was put together in the 18C; but the basic principles were probably centuries old. Even as late as the 19C ex-seamen were often employed to erect the enormous beam-engines such as those we see at Kew Pumping Station. They knew how to raise very heavy lumps to considerable heights with very simple equipment, for the engine manufacturers' fitters to bolt together.

The builders of those magnificent cathedrals and massive castles must have been a lot more technically able than we tend to give them credit for, at least as far as assembling them went.

The designs sometimes failed though, usually from inadequate foundations and excessive weight; and Wells Cathedral displays a startling way to hold the building together against huge spreading-loads.

Fred was mostly wrong. Ramps, which take an enormous amount of time and material to build, were the only way to lift multi-ton weights, but cranes, winches and pulleys were used whenever possible. For moderate weights, cranes are much faster than ramps and far easier to move around a building.

If Fred had looked at medieval manuscripts or building accounts, he would have found many references and drawings of cranes, some impressively large.

A few are still in place:

The sledge is interesting. Looks like stone blocks were pulled along the floor on the runners, but sat on rollers, presumably making them easier to get off the sledge at the other end.

And if Fred had looked closely at medieval structures he would have found most of the stone blocks to be relatively light. Further, larger blocks usually have a an expensively cut lewis hole, which is only needed if a crane or winch is used. The inner core of most medieval walls is made of mixed stones, roughly shaped, and almost all smaller than a one or two-man lift. Another clue is the presence in most walls of the holes used to take scaffolding, again not needed if a ramp is used. Scaffolding holes aren't obvious in well-finished buildings because they've been hidden.

Fred is one of my all-time engineering heroes, but he didn't know all the answers!

Dave

Edited By SillyOldDuffer on 18/01/2023 11:44:04

Thanks all, that explains things. The bed is roughly even all along when unbolted at the head and tailstock end so about 1/2 X and diminishing to zero when fully vertical.

The hardest bolt to get at, where the bed fixes to the headstock and is a bit tricky to get to - up through the motor/headstock housing is 5.5mm and needs a short allen key in case any one needs to take one apart.

Dave -

That's an impressive machine. Where is it?

I wonder if they used sledges, that would be dragged along planks pinned to the ground, from the cutting area to the crane. Or indeed it was not a sledge but a trolley, running on the rollers, if they surface above the side-members. We'd really need a contemporary account or illustration to know.

A former CEGB (Souther) electrician I once knew was one of the few in his team able to service the lamps high in Salisbury Cathedral, and indeed outside it - the aircraft warning lights atop the spire. He told me those are reached by an internal ladder to a hatch opening onto steel staples on the outside; and the internal ladder goes up through the builders' temporary(!) timber form-work.

This was one such church whose roof-trusses were prefabricated to templates on the floor. I gather many of the scriber-marks to denote which bit goes where, are still visible. The main beams of these are probably heavier and certainly a lot more ungainly to move than the ashlar blocks - no "dragging up ramps" to get these some 80 or 90 feet up.

I forget if this applies to Salisbury or Newcastle Cathedral (I'd visited each respectively for a building-stones tour and an ordination service), but it's possible to look up through the transept into some very complicated work indeed.

To work out, accurately how much you are lifting, you need to know the weights at each end, and how far apart they are.

If the Headstock is the heavy end, you will be lifting more than half. By the same token if the tailstock end is light; less than half the weight of the whole machine.

Somewhere between the two extremes there will be a point where the machine would balance and hang level. This can be called the centre of gravity. It is about this point that you take moments to calculate the weights at a particular point.

This is why, when moving a lathe, the Saddle and Tailstock mar moved to positions where the machine balances fairly level when lifted by a crane.

On the subject of ancient cranes, windlasses, the original, crude wooden windlass is still in the tower of Peterborough Cathedral. It is more or less a tree trunk, with handles, supported on two cruciform bearers.

Presumably the mechanical advantage provided by the length of the four handles, compared to the diameter of the trunk (which acted as the winch drum ).enabled the masons to lift /drag the ashlars into place.

Howard.

There is a man powered crane as per SOD's picture in the tower of Canterbury Cathedral. My headmaster who had been headboy at the attached school had the run of the building pre-WW2 and had operated it.