Quote:
Originally Posted by brushlessboy16
Could be very low, but im using the spacer plate that came with it to space the spur from the chassis. do you know the tensile strength of an m3 screw. it will surprise you..  |
According to McMaster, tensile strength of a 12mm long M3 screw is 174,000psi, however, that is pretty much a straight back pullin force, and it is rare to get a straight back pulling force on the motor in an RC. I've twisted the heads off plenty of M3 cap head screws before, and I've also bent and sheared off quite a few of them too. For instance, I bent 4 M3 cap head screws holding the DiemakerDave wing mount to my UE knucklehead shock tower on my Maxx when it landed hard straight down on the wing mount from only about 4 feet in the air. Now or course, that was 12 pounds of truck landing on that wing mount, and it did bend it pretty badly for being high grade aluminum, but the point is, that bent 4 M3 cap head screws at once and ripped the nut off the lower two. A heavy motor puts alot of force on a motor mount when landing flat on the ground, and if the car lands upside down, its going to want to pull that lower screw and washer out and bend the upper screw. IMO, there needs to be a machined lip of some kind at the back of that lower hole so the motor actually has 2 screws holding it on. It may be convenient to just have to remove 1 screw to pull the motor, but I'd rather be sure my motor is very strongly secured to the motor mount.