Paternoster storage system

The solution

Design Notes on paternoster storage system.

Keith Everett      4^th October 2020

• Trays

The trays are made from 800 mm long planter saucers obtained from garden suppliers. The saucer is suspended from the aluminium rods by two lengths of 25mm angle aluminium shaped to fit the side of the saucer and bent to form a hook to hang on the rod. The angle aluminium is attached to the saucer using a 4mm screw with a 4mm nyloc nut.

The cage around the saucer is formed from plastic coated steel mesh (50mm x100mm mesh) used in gardens. The mesh is attached to the  saucer using 4mm screws and captive nuts used on sheet metalwork. Photo available. The back of the cage of curved in to provide clearance with other trays.

• Suspension rods

The trays are suspended on horizontal rods made from 10mm dia aluminium. Each rod has two collars which slide on the rod and are fixed with 4mm grub screws. The collars are positioned each side of the tray suspension hooks to limit the movement of the tray so that it doesn’t collide with the chain mechanism. The collars are 25mm dia and 13mm thick.

The suspension rods are attached to the two chains on either side of the cupboard.

• Chains

The chains are standard ½” pitch chain from RS components (6125105) which comes in a 5 metre length. The chain is broken into 30 link segments and then joined with connection links (RS 6124641). The free side plate of each connection link is replaced with a plate made from 0.6mm thick mild steel. The new plate mimics the replaced plate but has an extension which is bent at 90 degrees to connect to the suspension rods (photo available). A M4 stud is silver soldered to the plate which mates with a hole towards each end of the suspension rod. The rod is fastened in place with an M4 Nylock but is not tightened down to allow some movement as the chain goes round the system.

• Sprockets

These are 58T cycle sprockets, however sprockets of this size normally tend to be fitted to stacks of sprockets so there is no material in the centre, hence the sprocket has been fitted to a 1.5mm mild steel disc. The upper sprockets are fitted with a solid bearing part no IGUS FJUM-01-10 held in place by a nut plate with 4 M4 holes.

The lower sprockets are fitted to a aluminium flanged collar made to the same dimensions as the Igus bearing above and held in place on a 10mm dia aluminium rod  by a 3mm split dowel. The 10mm rod is cut to half the width of the cupboard.

• Synchronising shaft

The two rods the lower sprockets are mounted on are joined using a 100mm long 12.5mm od x 10mm id tube fixed on one side with a 3mm split dowel and on the other with a split dowel having 3 pre drilled holes allowing 3 attempts to ensure the suspension rods hang horizontally.

• Self aligning bearing

Each end of the synchronising shaft  rotates in a dry self aligning bearing (igus EFOM-10). The bearing itself in mounted on a dry linear bearing in a 150mm section of aluminium slideway (igus NW-02-27 and NS-01-27-300)

• Chain tensioner

Because both lower sprockets are mounted on vertical slides the chain can be tensioned by applying a spring between the linear bearing and an anchor point mounted vertically below the bearing (photograph available). The spring used is 10mm dia approx. 35mm long and made from 1mm piano wire.

• Chain guide

The system will be rotated by grasping a suspension rod and pulling downwards. This may produce a sideways force which may cause the chain to ride up on the sprocket and become detached. To prevent this, the chain on the left hand side moves through a plastic channel . The channel is 14mm wide x 10mm deep with 1mm wall thickness. It is mounted in the interior corner of a 25mm angle aluminium with one wall cut down to 8mm. It is held in place with impact adhesive. The exposed part of the other side of the angle has two mounting holes which have been elongated slightly to provide some adjustment. The whole is mounted on a 35mm x 25mm softwood block. (photograph available).

• Chain lock

Because the trays are unlikely to be perfectly equally weighted, especially when being loaded initially, the system is likely to rotate on its own to balance the trays. This is likely to be inconvenient so a lock is included. The lock is an arm one end of which rotates about a pivot. The other end is available to be moved and moves between two magnets which hold the arm in the locked or open position.

At the centre of the arm a section of chain 7 links long is screwed to the arm with 3mm machine screws so that as the arm is lowered the chain engages with the sprocket and prevents it turning. The pivot is made from 10mm dia silver steel with a 10mm thread at one end screwing into a 5mm thick aluminium plate which is fixed to the wall of the cabinet. The arm is retained on the pivot with a brass bush and grub screw. Because the arm rubs up against the cabinet wall, there is a 0.5mm thick PTFE self adhesive pad to prevent marking.

• Chain guides

On first testing the system, it was found that the trays at the back were fouling on the synchronisation bar. So to provide clearance, the chains at the back run against two blocks which pushes the path of the chain backwards approx. 30-40 mm which allows the trays to clear the rod. The loading on the block is light so they have been made by planing a curve onto a softwood block and fitting 0.5mm thick PTFE to the bearing surface.

The benefit

Client can access and accomplish more art and craft tasks more quickly than they could be beforehand.

They no longer need to wait for visitors/helpers to move materials around for them