Draw Lower Chute

Right-click the Layers table on the Chute Faces tabsheet and choose Draw Lower Chute... to build the run of plate from the bottom of the discharge head box down to the loading point on the receiving belt.

Dimensions

The small letters beside the input boxes match the dimensions on this drawing. The plan shows a turning transfer; the elevation shows an inline one, where the surge bar and an intermediate ring are easiest to see. The receiving belt width and trough angle only suggest the bottom width, and have no letter.

Draw Lower Chute dimension drawing: a plan of a turning transfer showing both openings and belt directions, and an elevation of an inline chute showing the surge bar and an intermediate ring — Draw Lower Chute dimensions

Letter	Input	What it measures
T	Top opening Centre X, Y, Z	The centre of the top opening (the bottom of the head box).
a	Top opening Length along belt	Along the feed belt.
b	Top opening Width across belt	Across the feed belt.
c	Feed belt direction	The feed belt's direction of travel in plan, clockwise from +X.
B	Bottom opening Centre X, Y, Z	The centre of the bottom opening – the loading point.
d	Bottom opening Length along belt	Along the receiving belt.
e	Bottom opening Width across belt	Across the receiving belt, inside the skirts.
f	Receiving belt direction	The receiving belt's direction of travel in plan, clockwise from +X.
g	Surge Bar Height (Offset)	How far the bottom opening's downstream edge is raised above its rear edge.
h	Intermediate rings	The number of rings between the top and bottom openings.

What it draws

A loft between rectangular rings – the top opening, the bottom opening, and any intermediate rings between them. Each stage contributes four panels named Front, Right, Back and Left, and each panel is drawn as two triangles.

Why triangles and not rectangles. Where the top and bottom openings face different ways in plan, a four-cornered panel spanning them is warped – its four corners do not lie in one plane. A warped face has no meaningful plane equation, so the collision code has nothing sensible to test particles against. The bundled Demo 10 and Demo 12 chutes were both drawn by hand as triangles for exactly this reason.

The chute has no floor and no roof – it is open at both ends by definition. The rectangle it is open at the bottom is where the loading box picks it up.

The top opening

This is the head box's bottom opening, and the two have to agree exactly. Rather than ask you to retype the box's dimensions, the dialog lists every head box already in the drawing in the Top opening from box. Pick one and the six numbers below are filled in and locked.

The opening is recovered from the box's own Front Wall and Back Wall faces, so it keeps working after the box has been moved or rotated as a layer. Choose <enter manually> to unlock the fields for a chute that starts somewhere else.

Draw the head box first. The chute reads its top end from the box, so the box has to exist before the chute is drawn. If you change the box afterwards, redraw the chute rather than nudging its vertices.

The bottom opening

This sits over the receiving belt at the point the discharge is aimed at.

Centre X, Y, Z – the loading point. Work this out from the discharge trajectory and the transfer height; see Chute Design Guidelines.
Length along belt – how far the opening reaches along the receiving belt.
Receiving belt width and trough angle – used only to suggest the width below. They are not part of the geometry.
Width across belt – defaults to two thirds of the belt's projected width. Published guidance is explicit that this goes off the projected width and not the actual belt width, "as was common practice" – a troughed belt is narrower in plan than it is in the flat. Material has to land inside the skirts rather than on them, so the chute's opening follows the skirt spacing.
Receiving belt direction – the direction of travel of the belt being loaded, in plan. Together with the feed belt direction above, this is the turn the chute makes.

Positive turns clockwise. Both belt direction fields follow a site bearing rather than ordinary maths: 0° runs along +X, but 90° runs along −Y, not +Y – the opposite sense to Rotate Layer and to the head box's own Belt direction in plan field. Getting this backwards shows up as the surge bar raised on the wrong edge.

Surge Bar Height (Offset) – raises the front edge of the bottom opening above its rear edge by this much. A surge bar dams the stream at the bottom of the chute so material builds up and flows evenly out over it, rather than sliding straight out the front. BHP drawing 087-M-12386 shows this raised about 400 mm above the rear edge. Leave it at zero for a flat opening.

Intermediate rings

An inline, square or straight-reversing transfer lofts from top to bottom in one stage. Only an odd angle – anything that is not a multiple of 90° – gets an intermediate ring by default, so that the twist is taken in two gentler steps rather than one long one. The field is a suggestion – set it yourself and it stops following the turn.

A turn is not a twist. Turning the stream through a right angle does not mean twisting the chute's section through a right angle. A rectangle turned a quarter is the same rectangle with its length and width swapped, so a square transfer keeps every plate edge square to the head box and simply narrows one way while it stretches the other – which is exactly how Demo 12's own 90° chute is drawn. The generator squares the two openings up before lofting for this reason; only what is left over after whole quarter turns is a real twist, and only that needs a ring.

Each ring is a real rectangle at an interpolated size, position and plan angle, so the plate edges between rings stay straight and the chute can be fabricated as it is drawn.

Valley angles

The dialog shows the valley angle at every corner of every stage as you change the numbers, and warns when the shallowest one falls below 45°.

Where two sloping plates meet, the line they meet along – the valley – is always shallower than either plate. Two plates at 55° meeting square in plan give a valley of about 45°. Material runs in the valley, not down the middle of a plate, so it is the valley angle that has to clear the material's friction angle. A chute whose plates look steep enough can still hang up in its corners.

If a valley comes out too flat, either steepen the chute (drop the bottom opening, or raise the transfer) or bring the two openings closer together in plan. Both show up in the readout immediately.

How the demo projects are built

Project	Transfer	Shape
Demo 10 Inline Coal Transfer 6600tph	Inline	One loft. The main sloping panel runs from the head box frame under the pulley, near the scraper plate, down to the boot.
Demo 12 Iron Ore 90 deg transfer Segregation	Square	Two stages, with a ring where the section turns from running along the feed belt to running along the receiving one.

Once drawn, the chute is an ordinary layer: use Adjust X,Y,Z coordinates, Rotate Layer or direct vertex editing to adjust it, and Move Face to New Layer... to split a panel off on its own.