Double capstan grip

The specimen grip for materials such as rubber thread and elastic fiber

The double capstan grips can be used to grip filamentary, high-extension tensile specimens.

Advantages & features

Function description

The double capstan grips can be used to grip filamentary, high-extension tensile specimens.

With this deflection principle a force differential occurs over two stages, allowing specimen failure within the gauge length with no jaw breaks.

After the deflection of the double thread, a prestress weight (not included in scope of delivery) is attached. During this phase all three rollers can be moved to compensate for the change in length caused by the attachment of the pre-tension weight. The three lengths are adjusted to the material being tested.

Finally, the double thread is also gripped in height adjustable specimen grips.

After closing the specimen grips, the deflection rollers are locked into place. This results in frictional forces between the rollers and the specimen, which gently reduce the tensile force prior to end clamping (specimen grip), ensuring that the specimen is gripped securely and prevents the jaws from breaking.

A specimen grip with constant gripping force is used to clamp the double thread because the specimen to be tested can frequently slip out from between the gripping areas.

Advantages

Wrapping the specimen around the load reduction rollers ensures gentle gripping without jaw breaks.
These specimen grips ensure exact strain measurement on high-extension threads.
Preventing jaw breaks allows for efficient testing.

Technical overview

Item No.	317800
Type	8170
Test load F_max	0.5	kN
Usable load cells, type 1	0.1 ... 1	kN
Minimum gauge length	50	mm
Specimen diameter, max.	5	mm
Deflection rollers radius	10	mm
Upper specimen grip
Height	159	mm
Width	119	mm
Depth	72	mm
Width with clamping lever	153	mm
Connection	Ø 8	mm
Weight	0.7	kg
Lower specimen grip
Height	180	mm
Width	93	mm
Depth	62	mm
Depth with clamping lever	94	mm
Connection diameter	20	mm
Weight (with wedge screw grip), approx.	1.3	kg
Connection, stud	Ø 8 / Ø 20¹	mm
Ambient temperature	-20 ... +60	°C
Scope of delivery	Set²

The upper specimen grip has a connecting diameter of 8 mm and the lower one of 20 mm
Upper and lower specimen grip, one wedge screw grip type 8106, Fmax 500 N