Got very different PTFE tubes today. Going to do some comparisons. First impression picture (please take a closer look):
Any wishes on what and how to compare them?
Can you measure drag friction? Zip tie 1 meter (or whatever) into a double loop (720 degrees total curvature) and then measure the force to get filament through.
Tube stretch - hang 2 meters from something tall and then hang 10kg (or whatever) and see how much the length changes.
The two on the right appear to have suspiciously poor manufacturing, as shown in the off-center bore.
@Fred_U you are right.
@Ryan_Carlyle I’ll do the stretchtest. Friction was already on the list.
The blue one also is slightly thicker or also off center. Or it’s oval.
@Daniel_Stauffer grey, green and blue are all 4mm more or less. The white one is 4.2mm on spot.
Did you measure the inner bore?
@Daniel_Stauffer As far as I can at this size. Grey and white are spot on 2mm. Green is a little bit bigger (dont know how much, yet). Blue is CLEARLY >2mm.
@Ryan_Carlyle Grey, white and green have equal friction. Blue has way higher friction. (all 1m long, same filament piece pulled through, 10 times each).
Are the tubes straight enough to eliminate sidewall friction from the test sequence?
How would one test the diameter of the bore throughout the entire length of a test piece?
tubes are looped all the same during pull-tests, 30cm diameter. Straighten the tube defeats the purpose of a bowden-tube imho.
@Rene_Jurack Yes, there is that aspect. If a particular tube had internal defects, a straight tube would display that, but it’s obvious that a curved tube would show it as well. Sometimes the brain just shuts down when confronted with a keyboard.
Yes, straight tube friction will be near zero.
Who is the manufacturer of these tubes?
@MidnightVisions I won’t tell until I did the testing.
if the bore is not centered, won’t the tube want to twist when bent, so the larger wall thickness is in extension and the narrower area in compression? I think thats how its supposed to work.
I would like to see some friction coefficients and maybe if they have slightly different strain to them.
Someone never quite gets what everyone else is doing, when they dont say something, to keep things on the low down… we were trying to avoid claims and hype and get some quiet data is what I think was going on.
Yep. I am not mentioning a brand or name until data is collected.