fan blades as thruster propellers?
fan blades as thruster propellers?
I'm using 6" fan blades as propellers on my bilge pump thrusters on my current design. Haven't tried this out yet, nor have I seen anyone try it. Any ideas or opinions? Could this work, or am I about to create the world's first Formula One ROV?
Re: fan blades as thruster propellers?
What size pump motors? 1000gph?
6" is a lot of water contact to push (and pull). Worth trying, but monitor how many amps that pulls once you try it in water.
On a smaller 500gph motor, we ditched small 3" fan blades in favor of traditional RC boat props. Mainly due to how many amps being drawn, for just a little extra amount of thrust. Not to say size and shape of any given fan blade may make a big difference.
6" is a lot of water contact to push (and pull). Worth trying, but monitor how many amps that pulls once you try it in water.
On a smaller 500gph motor, we ditched small 3" fan blades in favor of traditional RC boat props. Mainly due to how many amps being drawn, for just a little extra amount of thrust. Not to say size and shape of any given fan blade may make a big difference.
Re: fan blades as thruster propellers?
The pumps are 500gph. Amazingly, the center of the 6" fan blades that I bought were exactly the same size of the impeller that the motor cartridges came with, so fitting the props was extremely easy. But if I were to buy "traditional RC boat props", I wouldn't have the faintest idea how to do so. How would I know that whatever prop I buy will fit? I don't know the size of the pump motor shaft. How have you (or others out there) known what to get? (NOTE: I live in NYC, and hobby shops for this kind of thing are rare, even non-existent. I'd have to buy online, and that means I wouldn't have a sales person at my disposal to learn from.)
Re: fan blades as thruster propellers?
Good point, and very true - mating props to shafts is a common headache.
A caliper will help you measure what you have. Or use a millimeter ruler and magnifying glass may yield close result. Post the brand of your pump motors, and I am sure others have that size handy. My 500GPH motors have 3mm shafts.
From there is usually takes a prop adapter or shaft adapter, two good search terms. Most often these are found in online hobby shops that carry parts for electric airplanes. The way RC boats connect motors to props is usually a flexible shaft which is not that useful on ROV.
But yes there is a rub. The majority of RC boat props are 4mm. And the majority of plane props are 5mm. So finding adapters can take time and searching. I say 'majority' but certainly a lot.
I ended up with adapters that went from 3mm to 5mm. Good for my motor, but not the prop. I cut off the plastic 'tip' of the hub and hammered out the brass 4mm insert. What was left was a nice 5mm hole to put the adapter thru and screen down tight with a nut. Not as pretty as the smooth tip that was there, but very functional.
But as before, you got motors and you got props (blades) to fit....so do a test. Get a bucket of water and a battery, and hopefully a multimeter or hobby RC watt-meter, something that will tell you how much current is being drawn. Mount the motor firmly to a stick or rod or pipe or something...they do have some power and a 6" blade can whack a finger something fierce. Test in air first. Is anything getting warm? Wire, motor, battery? Are the amps under 3 or so?
Then turn it off and place it in water. Turn on again and watch for overheating, and amps ramping up, past 5 I would start to be concerned. How much "thrust" does the unit have, just feeling by hand? To move a fair size ROV, it needs to be enough where you really have to hold the stick well. If it turns the prop, but barely forces your hand...the motor is swamped trying to swing that blade thru the water.
A caliper will help you measure what you have. Or use a millimeter ruler and magnifying glass may yield close result. Post the brand of your pump motors, and I am sure others have that size handy. My 500GPH motors have 3mm shafts.
From there is usually takes a prop adapter or shaft adapter, two good search terms. Most often these are found in online hobby shops that carry parts for electric airplanes. The way RC boats connect motors to props is usually a flexible shaft which is not that useful on ROV.
But yes there is a rub. The majority of RC boat props are 4mm. And the majority of plane props are 5mm. So finding adapters can take time and searching. I say 'majority' but certainly a lot.
I ended up with adapters that went from 3mm to 5mm. Good for my motor, but not the prop. I cut off the plastic 'tip' of the hub and hammered out the brass 4mm insert. What was left was a nice 5mm hole to put the adapter thru and screen down tight with a nut. Not as pretty as the smooth tip that was there, but very functional.
But as before, you got motors and you got props (blades) to fit....so do a test. Get a bucket of water and a battery, and hopefully a multimeter or hobby RC watt-meter, something that will tell you how much current is being drawn. Mount the motor firmly to a stick or rod or pipe or something...they do have some power and a 6" blade can whack a finger something fierce. Test in air first. Is anything getting warm? Wire, motor, battery? Are the amps under 3 or so?
Then turn it off and place it in water. Turn on again and watch for overheating, and amps ramping up, past 5 I would start to be concerned. How much "thrust" does the unit have, just feeling by hand? To move a fair size ROV, it needs to be enough where you really have to hold the stick well. If it turns the prop, but barely forces your hand...the motor is swamped trying to swing that blade thru the water.
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greenkarson
- Posts: 36
- Joined: Jun 5th, 2011, 9:21 pm
Re: fan blades as thruster propellers?
Forget it! I tried what sounds like the same idea here is a link describing what happened
viewtopic.php?f=3&t=490#p2036 i eventuality went with 2" rc props that work great
viewtopic.php?f=3&t=490#p2036 i eventuality went with 2" rc props that work great