Luap wrote:
The spring allows quick release of the clamp. If more tightening pressure is desired, the spring can be replaced with a suitable length of 1/4" ID tubing. On some tubing sizes, the knob can be tightened such that the spring can be fully compressed, coil to coil to simulate a rigid tube.
The design intent is to hang the VML on a lightstand section with the bottom of the VML resting on a stand knuckle.
Some users have applied a piece of adhesive backed friction material . . . such as rubber, and found the clamp will support the VLM on the stand without it needing to rest on a stand knuckle.
Your points on glass filled Nylon may or may not be valid. There is no question that glass filled injection molded parts have near-zero elongation before break and and poor notched IZOD impact strength than virgin materials. I have seen plenty of glass filled Nylon lightstand parts crack and break when tightened.
We have recently hired a highly experienced plastic molding engineer with an MS degree and 40 years experience and I have posed the question to him.
I can say that I have tested virgin Polycarbonate AB and Einstein housings by tossing them approximately 50' in the air and letting them land on concrete, with no breaks or cracks. On the other hand, we have received similar parts that were not dried properly or molded at the right temperatures and experienced failures. Failures are eliminated after we demand closer attention to molding machine parameters.
Here is the response from our recently hired Technical Director, who is an MSE with 30+ years experience in injection molding designs and materials:
Paul,
ABS is a good choice. The notched Izod impact values are in the same range
as nylon, depending on the grades being compared. The rubber, butadiene, in
the ABS provides the impact performance. Depending on grade chosen Abs can
have good impact properties to minus 40F. Glass filled nylon is good,
depending on the glass loading levels. Nylons can be very flexible at room
temperature and may need the glass for adequate stiffness. One advantage of
glass, depending on loading level, is that it can improve tensile properties
without adversely other properties like impact. However, since that glass
can orient in the direction of flow during molding, it can lead to
anisotropic properties. At high loading, loadings properties such as impact
is sacrificed for strength and stiffness. The stiffness of ABS appears to
be adequate.
In this case, the grade selected is more important than the base resin.
Based on the way the battery case flexes, assuming the same grade is used
throughout, the ABS is a good choice.
Steve
So it doesn't appear to be a right or wrong issue and either material appears correct for the part.
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