Effects of Temperature on HPR Materials

It's commonly known that Quantum tubing shrinks when it's cold. But how much? How much do other materials shrink when it gets cold? Does it get brittle? Well, here's what I did to find out.

Coefficient of Thermal Expansion

This test was conducted to determine the amount that a material expanded and contracted at various temperatures. As parts become heated in the desert sun, or contract in the cold, there is a possibility of jamming of pistons or cracking of glued joints if these dimensions change at different rates. 

For this test I used the parts from a PML "Bull Puppy 2.1" kit. I measured the component dimensions and plotted them starting a -40 degrees Fahrenheit. Below is a table of the parts tested and their tested dimension. 

All measurements were taken using the NIST traceable digital calipers shown below. 

0-6" Mitutoyo Absolute DIGimatic OD caliper, used for all OD stuff

0-8" Mitutoyo Absolute DIGimatic ID caliper, used for tube ID checks

0-20" Mitutoyo Absolute DIGimatic OD caliper, used for tube length checks

The test was started at –40F and proceeded up to 150F, in 10F increments. The environmental chamber used is an MTS Model 610.06E-03 chamber. It has a 5,236 ci capacity. It chills via regulated LN2 and heats with a series of electrical resistance coils. The atmosphere is vigorously circulated. All temperature measurements are NIST traceable. 

Notes: The starting temperature was -40F. Ovality was removed from the test because all dimensions were measured at the same datum. the centering ring, the ends of the Quantum tube and the fins were lightly sanded with 400 grit sandpaper to remove any burs before the start of the test. The nose cone has two ridges to better fit into the body tube. These ridges were not measured.

The interesting point noted was the sudden expansion of the centering ring as I approached 60F. This was most likely due to the wood picking up moisture during warming. There was condensation in the test chamber. You’ll then note that the centering began to shrink again. This was due to the heat of the chamber drying out the wood. I do have a wood moister content analyzer but the centering was too small to test. It was most likely in the 10% to 15% range when the test was started, as typical for plywood’s of this nature. The piston did not go through this transformation because the phenolic tube held it to size.  

This shows how the tube can expand or contract in relationship to a G-10 fin. I did not measure the force of the movement of the G-10 (yet) but it may be enough to break the fillets at the tube/fin joint. The Quantum tube shrunk as expected but the G-10 changed very little.