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Author Topic: ISO a Spinner for a project  (Read 962 times)

Offline Paul Taylor

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ISO a Spinner for a project
« on: September 24, 2022, 04:10:59 PM »
Anyone have a source for electric slotted spinners.
I need a 1-3/4 plastic Air Flow.
I can find 2in but no 1-3/4. 🥴
Post a link please.
Paul
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Online William DeMauro

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Re: ISO a Spinner for a project
« Reply #1 on: September 24, 2022, 07:29:20 PM »
For 2 blade tractor spinners try rc dude.com otherwise maybe zhobby from eBay. I’m on my phone or I would post better links. But they should be easy to find. I just realized that the 1 3/4 might not be available or made with th slots. That may have been a custom order from tru turn which is no longer available. You might have to make your own slots if you really need them
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Offline Paul Taylor

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Re: ISO a Spinner for a project
« Reply #2 on: September 24, 2022, 08:09:37 PM »
For 2 blade tractor spinners try rc dude.com otherwise maybe zhobby from eBay. I’m on my phone or I would post better links. But they should be easy to find. I just realized that the 1 3/4 might not be available or made with th slots. That may have been a custom order from tru turn which is no longer available. You might have to make your own slots if you really need them

Thanks William.
I will give it a look see. I’ll take plastic 1-3/4 anything at this point.
Paul
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Online Ken Culbertson

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Re: ISO a Spinner for a project
« Reply #3 on: September 25, 2022, 12:19:47 AM »
I thought Turnigy made a 44mm.  I thought I used them on my Twister.  All I could find now was a 51mm.  As a side note, they did not do much for cooling.

Ken
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Offline Carl Cisneros

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Offline Dan McEntee

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Re: ISO a Spinner for a project
« Reply #5 on: September 25, 2022, 11:49:50 AM »
I thought Turnigy made a 44mm.  I thought I used them on my Twister.  All I could find now was a 51mm.  As a side note, they did not do much for cooling.

Ken

   I don't fly electric, but try to read as much as possible about their operation. I often wondered about the effectiveness of slotted spinners for cooling. Some models have other slots and scoops for cooling air. I wonder if you were to take some smoke, and at any RPM, introduce smoke the the air flow near the point of the slotted spinner. The watch the area of the exhaust slots where the cooling air is intended to exit and see if there is any smoke coming out there. If air is getting through the slots, and you don't have any place for the air pressure to exit, it won't cool anything. I would tend to think that a slotted spinner that is turning at operating RPM, would just tend to make a bubble with no flow.
     This brings up another question about cooling. Do any of you guys have a filter on the cooling air inlets?  This became a question when a local flying buddy had his motor seize on him in flight one day early this summer. The immediate thought was a bearing took a dump, as he had been flying this model for quite a while with no motor issues. Then when we examined it, it looked like some of the wires on the armature were burned. He changed out the motor, and I asked him for the old one to do a post mortem exam on it. Got the motor apart, and found that two magnets had come loose (they are just glued in place) and jammed the armature. What knocked the magnets loose was all the junk, grit and gravel I found in the motor in between the other magnets! What we thought was burned wire on the armature was some kind of large debris which I'm not sure what it was. May have been the remains of a bug! The bearings seemed fine and I was tempted to just glue the magnets back in place and give him the motor back to test run, but thought better of it,  after thinking that I didn't know if any of the other magnets were near separating from the case, as the motor was pretty old ( it was an airplane from Walt Brownell's collection and built quite a while ago. He flew the model quite a bit.)
  So, it made me wonder if any of you guys thought about the junk and debris that can get inside a motor and stay there! I should have done the exam on a piece of white paper and photographed the junk that came out but didn't think of it at the time, not expecting to find what I found.
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  Dan McEntee
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Online Ken Culbertson

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Re: ISO a Spinner for a project
« Reply #6 on: September 25, 2022, 12:50:22 PM »
   I don't fly electric, but try to read as much as possible about their operation. I often wondered about the effectiveness of slotted spinners for cooling. Some models have other slots and scoops for cooling air. I wonder if you were to take some smoke, and at any RPM, introduce smoke the the air flow near the point of the slotted spinner. The watch the area of the exhaust slots where the cooling air is intended to exit and see if there is any smoke coming out there. If air is getting through the slots, and you don't have any place for the air pressure to exit, it won't cool anything. I would tend to think that a slotted spinner that is turning at operating RPM, would just tend to make a bubble with no flow.
     This brings up another question about cooling. Do any of you guys have a filter on the cooling air inlets?  This became a question when a local flying buddy had his motor seize on him in flight one day early this summer. The immediate thought was a bearing took a dump, as he had been flying this model for quite a while with no motor issues. Then when we examined it, it looked like some of the wires on the armature were burned. He changed out the motor, and I asked him for the old one to do a post mortem exam on it. Got the motor apart, and found that two magnets had come loose (they are just glued in place) and jammed the armature. What knocked the magnets loose was all the junk, grit and gravel I found in the motor in between the other magnets! What we thought was burned wire on the armature was some kind of large debris which I'm not sure what it was. May have been the remains of a bug! The bearings seemed fine and I was tempted to just glue the magnets back in place and give him the motor back to test run, but thought better of it,  after thinking that I didn't know if any of the other magnets were near separating from the case, as the motor was pretty old ( it was an airplane from Walt Brownell's collection and built quite a while ago. He flew the model quite a bit.)
  So, it made me wonder if any of you guys thought about the junk and debris that can get inside a motor and stay there! I should have done the exam on a piece of white paper and photographed the junk that came out but didn't think of it at the time, not expecting to find what I found.
  Type at you later,
  Dan McEntee
I think you are right about the bubble.  I didn't notice any better cooling and, it does introduce a path for stuff to get into the motor.  Depending on the motor and orientation, you may be messing with it's internal cooling as well.  I have also yet to see one for reverse rotation props.  Bottom line - waste of time.  Have to think about the electric "bug in the venturi" equivalent.

Ken

Ken
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Offline Lauri Malila

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Re: ISO a Spinner for a project
« Reply #7 on: September 25, 2022, 01:06:30 PM »
I'd guess that a slotted spinner acts as a centrifugal turbine; air goes out from the slots. I'd also guess that in a typical fuselage, the lowest pressure point is near the gap between fuselage and spinner backplate, so airflow would be from inside towards outside in the gap. Maybe Igor has written about it, I'm not sure if I remember correct..
If the airflow is as I guessed, kind of against common sense, what does it do for the propeller efficiency? A normal, well-proportioned spinner usually increases propeller efficiency as it cleans out the chaotic airflow near the center of propeller, what does a slotted spinner do? L

Offline Dan McEntee

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Re: ISO a Spinner for a project
« Reply #8 on: September 25, 2022, 02:06:43 PM »
I'd guess that a slotted spinner acts as a centrifugal turbine; air goes out from the slots. I'd also guess that in a typical fuselage, the lowest pressure point is near the gap between fuselage and spinner backplate, so airflow would be from inside towards outside in the gap. Maybe Igor has written about it, I'm not sure if I remember correct..
If the airflow is as I guessed, kind of against common sense, what does it do for the propeller efficiency? A normal, well-proportioned spinner usually increases propeller efficiency as it cleans out the chaotic airflow near the center of propeller, what does a slotted spinner do? L

   If I were to design an electric model, I would do as I have seen on some full scale air cooled radial engine racers. That is a solid spinner with a nose shaped that will allow a gap all the way around the spinner for an air inlet, and then the nose shape flows back from that edge. Make sure there is a a large enough exhaust opening beyond the motor and speed controller.. That all would take some thought to lay out with enough structure for a strong nose to handle the torque the motor and prop generate. If it works for Rare Bear, it should work elsewhere.
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   Dan McEntee
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Offline Igor Burger

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Re: ISO a Spinner for a project
« Reply #9 on: September 27, 2022, 01:25:18 AM »
I'd guess that a slotted spinner acts as a centrifugal turbine; air goes out from the slots. I'd also guess that in a typical fuselage, the lowest pressure point is near the gap between fuselage and spinner backplate, so airflow would be from inside towards outside in the gap. Maybe Igor has written about it, I'm not sure if I remember correct..
If the airflow is as I guessed, kind of against common sense, what does it do for the propeller efficiency? A normal, well-proportioned spinner usually increases propeller efficiency as it cleans out the chaotic airflow near the center of propeller, what does a slotted spinner do? L

It all depends on slippage. At stall speed (or after tight corner), prop has reversed airflow at the center. It is exactly the same effect as tip worticles at tips of prop, but from opposite side of the "prop wing" which is effective somehere at 3/4 of the blade. So outside of it and inside of it it creates worticles.

However when prop moves forward at low slippage, incomming air will push that airflow back and air speed at center will be just little lower than that at 3/4 of blade.

But I do not think it has any effect on our models with relatively large props.


Offline Steve Dwyer

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Re: ISO a Spinner for a project
« Reply #10 on: September 27, 2022, 06:07:48 AM »
I would think while traveling through the air at 60 plus mph the impact air and velocity pressure would force a decent flow through the slots. On the ground, however, the reverse may come into play while a venturi effect and static pressure inside the spinner allows air to be drawn out of the slots but this is all very theoretical.

If the amp draw could be measured in the air as on the ground you might see a variation due to motor temperature differences to prove out this thinking.

Steve


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