Dynatup 8250, Operating Instructions Manual

Page: 45 / 64

Adjusting the Stop Blocks and Shock Absorbers
5-5
Preparation for
Use
Setting the Stop Block Height
Caution Caution
Make sure that the position of the stop blocks is such that the tup cannot Make sure that the position of the stop blocks is such that the tup cannot
touch any part of the specimen support fixture.
touch any part of the specimen support fixture.
Stop blocks are used only in gravity mode operation. To set the stop block height:
1. Using the 1 1/8 inch flat wrench provided with the machine, build stop blocks to the
appropriate height by screwing the various sections together. The two stop block
stacks must be the same height and have the same type of elastomeric stop block top.
Two hardnesses of stop block tops are provided.
2. To find the correct stop block height, lower the crosshead and tup onto a specimen
placed in the specimen support fixture (anvil). The top of the stop blocks must be
positioned so that the crosshead will not contact the stop blocks until after the
specimen is completely broken or penetrated.
3. The crosshead/tup must not be allowed to touch any part of the specimen support
fixture. Check this by removing the specimen and gently lowering the crosshead
onto the stop blocks. Be sure there is ample clearance between the tup and the fixture
to allow for deflection of the stop blocks on impact.
4. When the crosshead and tup are resting on a specimen, the optimum distance
between the top of the stop blocks and the bottom of the crosshead is generally about
1 inch (2.5cm). Specimens with large deflections to failure may require the stop
blocks to be set to a lower position.
Setting the Shock Absorber Height
Caution Caution
Always use the shock absorbers and Always use the shock absorbers and snubbers when operating in the snubbers when operating in the
pneumatically assisted mode. pneumatically assisted mode.
The shock absorber can be used to arrest the crosshead under all circumstances.
However, due to the long piston stroke, which reduces the available deflection, the shock
absorbers are generally used only with high velocity testing.
To install the shock absorber assemblies:
1. Screw the hydraulic shock absorber into place and tighten.
2. Set the shock absorber to the correct height. To find the correct height: lower the
crosshead and tup onto a specimen placed in the specimen support fixture (anvil).
The top of the shock absorber rod must be positioned so that the crosshead will not
contact the shock absorber until after the specimen is completely broken or
penetrated. Shock absorber height is adjusted by adding and/or subtracting stop block
segments as necessary.