RIDSDALE-DIETERT HAND OPERATED UNIVERSAL SAND STRENGTH MACHINE (METRIC)

I GENERAL PRINCIPLES

The Universal Sand Strength Machine, together with the appropriate accessories, will determine the compression, shear, tensile, transverse and splitting strengths of moulding and core making materials by means of dead weight loading.

II DESCRIPTION

This machine consists of three major parts: frame, pendulum weight and pusher arm. The pusher arm is motivated by means of a small handwheel which, through a gear box, rotates a pinion engaged in a rack on the quadrant. The pendulum weight swings on ball bearings and can be moved by the pusher arm, via a test specimen, from a vertical position, through 90°, to a horizontal position, with a consequent increase of load on the test specimen. A magnetic rider is moved up a calibrated scale by the pendulum weight and indicates the point at which specimen collapse occurs. The machine is calibrated in kN/m2 for 50 mm diameter x 50 mm height standard sand specimens. The accessories required for the determination of shear, dry, tensile, transverse and splitting strengths are described separately.

III INSTALLATION

(a) Set the machine on a rigid bench and level by means of the two adjusting screws until the bubble of the spirit level is centred. The front edge of the pusher plate should now coincide with the ‘O’ line on the scale and the pendulum weight should swing freely in the frame, with the pusher plate just clearing the scale.

(b) Place the coil spring in the hole in the gear box cover plate with the small brass wear pad on the protruding end of the spring. Ensure that the felt washer is in position in the recess of the hand-wheel boss and place the hand-wheel on the pinion shaft. Adjust until the felt washer is nipped lightly between the hand-wheel and the gear box cover plate and secure with the set screw in the hand-wheel boss, ensuring that this locates on the flat on the pinion shaft.

IV TEST PROCEDURE

(A) Green Compression Strength

• (a) Place the compression heads in the position shown on the illustration.
• (b) Raise the weight arm slightly and insert a metric standard 50 mm diameter x 50 mm height test specimen between the compression heads so that the face that was uppermost in the ramming operation is facing the right-hand compression head. Care should be taken not to damage the specimen.

• (c) See that the magnetic rider is resting against the pusher plate and that there is at least 6 mm clearance between the rubber bumper and the lug on the weight arm. If this clearance is not sufficient, it means that the specimen is smaller than the permitted tolerance and should be discarded.

• (d) Apply a load to the specimen by turning the hand-wheel at a uniform rate (approximately 25 kN/m2 green compression in 10 seconds)* until the specimen collapses.

• (e) Record the reading shown on the lower edge of the magnetic rider, reading the scale designated “Green Compression Strength”.

• (f) Return the weight to zero by reversing the rotation of the hand-wheel.Remove the sand from the compression heads.

* This loading rate applies to all tests on the machine.

IV TEST PROCEDURE (cont’d)

(B) Green Shear Strength

• (a) Place the shear test heads in the lower position in the machine, with the head having the half round holder attached to it in the pusher arm.
• (b) Raise the weight arm slightly and insert a metric standard 50 mm diameter x 50 mm height specimen between the heads.

• (c) Ensure that the magnetic rider is resting against the pusher arm and that there is 6 mm clearance between the rubber bumper and the lug on theweight arm.
• (d) Apply the load uniformly until the specimen shears.

• (e) Read the lower edge of the magnetic rider on the scale designated “Green Shear”.
• (f) Remove the sheared specimen as under (A) “Green Compression Strength”, section (f).

(C) Dry Compression and Dry Shear Strengths

• (a) Place either the compression heads or the shear heads in the top position of the machine. This position increases the load applied by a factor of 5.
• (b) Prepare metric standard 50 mm diameter x 50 mm height test specimens in the usual way and dry in an oven at 110 °C for 2 hours.

• (c) When cool, place in position between test heads and adjust clearance between rubber bumper and lug on weight arm to approximately 13 mm using the adjusting screw in the pusher arm.
• (d) Apply the load as for “Green Compression” and “Green Shear” until the specimen collapses.

• (e) Read the scale designated “Dry Compression” or “Dry Shear” according to the test heads being used.
• (f) Remove the broken specimen as under (A) “Green Compression Strength”, Section (f).
  

V MAINTENANCE

Keep the machine clean, removing surplus sand and pieces of broken specimens with a soft brush after each test. Oil the hand-wheel shaft once a month by means of the spring loaded oiler located at the top of the gear box behind the hand-wheel. Lightly grease the path of the hand-wheel brake pad from time to time to ensure smooth operation whilst loading the specimen.
The mainshaft ball journals and the gear box of the pusher arm are pre-packed with grease and require no attention.
The gear rack should be free from grease to prevent sand sticking to it. It is important that the rubber bumper is in good condition to absorb the shock when the specimen breaks and thus prevent damage to the gears. Replace when it has worn down to 3 mm thickness.

VI RECOMMENDED SPARES

Part No Description

403 Adjusting screw – pusher arm
404 Ball journal – mainshaft - weight
406 Levelling screw – main frame
409 Gear rack – main frame
410 Scale – main frame
411 Magnetic rider – scale – main frame
412 Pusher plate - weight
413 Rubber bumper – pusher arm
414 Handwheel
415 Felt washer - handwheel
417 Drive pinion – gear box – pusher arm
421 Brake spring - handwheel
422 Compression heads – pusher arm - weight
424 Rack pinion – gear box – pusher arm
425 Reduction gear – gear box – pusher arm
426 Pad – brake spring – handwheel.