Mounting Propellers
Posted: Dec 2nd, 2010, 5:05 pm
Bigbellydude commented in the Bilge Blower Thrusters thread that the discussion had wandered off-topic a bit, discussing how to mount propellers on the shafts of bilge pump motors. So, if you are interested in how to mount propellers on these motors you should first check out Steve's detailed discussion to be found near the bottom of the first page of Bilge Blower Thrusters.
I've had good luck with a simpler, but possibly riskier, approach shown in the attached photo. First, I bought a 1" long machine screw whose threads matched the propeller. I don't recall exactly the size and thread count, except I recall it was metric. (The nice thing about hunting for such things at Ace Hardware stores, compared to say, Home Depot, is they have "open stock" trays, allowing you try this one and that one, until you find what you need.)
I screwed this into the propeller very tightly, then I cut off the head of the screw. I used a flat file to file down the treads into a cone shape at the cut end, so that at the very tip there were almost no threads left, sloping gently up 1/4" or so to where the threads remained untouched. This made it into a "self-tapping" screw, which I screwed into the end of a 1-1/4" length of 1/8" ID brass tube (also from Ace).
Next, I used a wooden match stick to pack epoxy clay into the open end of the tube. I then SLOWLY pushed the tube onto the shaft of the motor. This shaft has a chamfer (flat spot) along one side, which provided a path for the excess clay to be squeezed out. I scraped away the excess clay as it emerged, so as to not allow it into the motor housing. I then left it for the epoxy clay to set.
Maybe I was just lucky. I've done it only this once. But the prop spins nice and true, and I'm sure it's not coming off anytime soon.
--Pilikia
I've had good luck with a simpler, but possibly riskier, approach shown in the attached photo. First, I bought a 1" long machine screw whose threads matched the propeller. I don't recall exactly the size and thread count, except I recall it was metric. (The nice thing about hunting for such things at Ace Hardware stores, compared to say, Home Depot, is they have "open stock" trays, allowing you try this one and that one, until you find what you need.)
I screwed this into the propeller very tightly, then I cut off the head of the screw. I used a flat file to file down the treads into a cone shape at the cut end, so that at the very tip there were almost no threads left, sloping gently up 1/4" or so to where the threads remained untouched. This made it into a "self-tapping" screw, which I screwed into the end of a 1-1/4" length of 1/8" ID brass tube (also from Ace).
Next, I used a wooden match stick to pack epoxy clay into the open end of the tube. I then SLOWLY pushed the tube onto the shaft of the motor. This shaft has a chamfer (flat spot) along one side, which provided a path for the excess clay to be squeezed out. I scraped away the excess clay as it emerged, so as to not allow it into the motor housing. I then left it for the epoxy clay to set.
Maybe I was just lucky. I've done it only this once. But the prop spins nice and true, and I'm sure it's not coming off anytime soon.
--Pilikia
that if you just screw the prop onto a threaded shaft (no matter how tight) it will eventually spin off when the motor goes in reverse. The easy fix though is to just thread a nut onto the shaft first, next screw on the prop and then just back the nut off back against the prop. I haven't had one spin of using this method yet.