Hello, Can anyone tell me how to measure the shaft length please. For example it says 2500-124 how should I understand which one I need? (Small, big ext.) Im using Vex EDR btw.
Since nothing on Vex Robotics is listed with that part number, it is probably from one of the V5 kits. This means the shaft is either 2 inches, 3 inches, 3.5 inches, 4 inches, or 12 inches. You could simply measure the length with a tape measure to figure out which, and if none of the sizes are long enough, you can cut one of the 12" shafts down. As for which size you should use, just use whatever size fits (whether or not it’s custom).
124 is a 4" I believe.
This is the product ID I believe
2500-124 is an IQ kit shaft. It is the 8x pitch shaft which is 99.8mm in length.
Here are some links to the EDR shafts.
IQ metal shafts and EDR normal shafts (i.e., not high-strength) are the same parts. What IQ documentation would call an “8x pitch shaft” is a “4 inch shaft” in EDR parlance - each “pitch” unit is half an inch. As such, your measurement of 99.8mm (= 3.93in) seems about right.
Ya, I just pulled the measurement from the documentation on the Vex product page.
Wait: can you buy 4 inch normal axles from the IQ section and use them on the edr robot?
Yes, you can do that. 4" axels do not appear to be listed for separate purchase under EDR but they are included in the V5 competition super kit (and maybe other V5 kits, I haven’t checked), so they’re OK to use per <R5a> (emphasis mine):