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Epiphany today after testing prop 3, a nice little 3 blade with no starting torque.
Prop #2 and 3 are plastic. I own a heat gun.

2 minutes later I had re-pitched prop #2 to a more drastic angle, per my welding bench and appropriate heat and pressure.
As originally thought, and as Pete reminded me, a greater pitch was needed to create more startup torque.

10 minutes later we got a spinner. No loads or output, but it cranks up, so second hurtle is overcome. We know it's possible with a small prop.

Video doesn't give a good visual due to frame rates, but the little bugger spins pretty good. Once output is tested further prop enhancements can be tested.

No load we have a 72 mph spin-up speed, and a <20 drop out speed. Didn't bother moving up into high speed testing now that it rotates.

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If anyone would like to contribute or has an interest in benefiting from from this adventure, I believe the prop style to try next would be those used on bow thrusters.

The tunnel sizes are right, they are multi-bladed and appear to be good pitch. If they spin up to the proper rpm then it becomes an easy off-the-shelf replacement part, and could be sized up or down depending on load or aircraft.

Starting point would be the 185 mm size, with the 12.2mm shaft diameter.
http://www.ebay.com/itm/Vetus-bow-thruster-prop-6-blade-185mm-for-Bow-50-80-Set0089-/132184915427

95296_Vetus_Vetus_Bow_Thruster_Propeller_6_blade___1.png

But could go up to the 246mm (9.6") diameter if needed.
http://www.vetusmarine.com/store/c/309-Thruster-Propellers.aspx

pb.
 

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Progress :p Now make a nice spinner to streamline the air in the hub area. Start with a length to diameter ratio of 2/1 or thereabouts. This will improve the efficiency. As it is now the flat hub is generating turbulence which is partially blocking the inboard portion of the blades. Test with the spinner to see if you can get a lower spin up speed. After that you may want to increase the pitch some more. Do only one change at a time so that you can be certain of what does what.
 
Progress :p Now make a nice spinner to streamline the air in the hub area. Start with a length to diameter ratio of 2/1 or thereabouts. This will improve the efficiency. As it is now the flat hub is generating turbulence which is partially blocking the inboard portion of the blades. Test with the spinner to see if you can get a lower spin up speed. After that you may want to increase the pitch some more. Do only one change at a time so that you can be certain of what does what.

hahahahaha!

Pete, I'm happy it spins. Until we start getting output from it in readable fashion, there will be no further prop or airflow enhancements. I'm supposed to be working.

pb.
 
Epiphany today after testing prop 3, a nice little 3 blade with no starting torque.
Prop #2 and 3 are plastic. I own a heat gun.

Nobody mentioned the heat gun last week because we thought you were smart enough to have already tried that :roll:

Glenn
 
Truck mounted quick run with hand bent prop -

3 amps D.C. Output at 75 mph
5 amps D.C. Output at 85 mph


With some prop tweaking and good airflow orientation I see no reason why you can't get 12+ amps at 100 mph.

Gen output failure light is a nice regulator feature too if you're a trip taker.


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What's your setup to load the gen and read the out put?

Those numbers are better than I expected. No reason for them not to improve with balancing and smoothing the air flow.

Web
 
Web,

Connected the regulator as spec'd, using a trailer marker light as the INOP, and basically a fully charged 12v 24xhmd starting battery, since it was available. I connected an LED floodlight as a small load, again because it was available, but it draws less than 4 amps. I turned that on and ran the light constant, and measured amps output between regulator and battery.

No idea the true rpm of the generator, as I have no way to measure that. Also was some airflow disruptions due to truck cab, passing vehicles etc, so amps output were a little jumpy. Obviously no where near the output capacity as the regulator appeared to output everything it could based on rpm.

I'd like to create a larger load on the battery, but not sure what good it will do without being able to push it all through the air faster. Not sure how to explain 100 mph test runs to the local troopers.

pb

Couple photos I attempted to take during the process -

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Use lamps from truck tail lights. 1156 or 1157. Easy to find and fairly cheap. If you hook one up to a 12 volt battery you can measure the current draw for that one lamp. Then make an arraignment that will let you switch in or out any number of these lamps that you might need to load the gen.

If you can drive around with this test setup hanging out of a truck and nobody gives you grief, your in a good spot!

Web
 
How much load do you want? Most of my lights these days are LEDs and my budget has pretty much been depleted on this project


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Walmart has plenty of the old lamps.

You'll want enough to slightly overload the gen. Keep adding to the load, at a steady speed, until the voltage starts to drop. That's the point at which the reg can no longer force enough power from the generator. That current draw and speed are two important points to find.

Web
 
I can just add loads to the battery, with switches - right?

And what will this tell us? I'm okay with 5 amps... lol
 
I'd just add some sockets for the lamps. Plug them in to increase the load, remove to decrease. Just make sure that the ammeter is in the charging system output or you'll be measuring some battery power, too.

I just thought about the battery that you are using. It's so large that when you hit max output on the gen, the battery will start powering the load. Instead of looking for a drop off on the voltage, at max load, look for a point at which no increase in current shows on the ammeter.

I'd want to know A) What is the MAX current I can get and what speed is that. B) What is the max current I can get at my usual speeds. I think that is critical to planning out loads under different conditions. Elmer Keith did say that 'to much gun beats the alternative'.

Web
 
I'll see what I can do.
Driving out of the airport on a 50 mile an hour road, semi truck drove by and had enough gusts to spin up the generator. Oops. Lol.


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Saw this setup at the local airfield today. Not a dynamo, but thought you might like to see it.


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So I'll confess- thought it might be intentional but didn't want to put all of my ignorance on display all at once.. I'm going to take a closer look next time I'm at the airport.....
 
Well Pete, we have a solution. There's a reason some props are expensive, and that's because they work.
I've got a cut in speed now at 45, which means in the prop blast this thing will spin before you even begin you take off roll.
80 miles an hour is pumping out 12 1/2 A. At your cruise speed you can drag a line and provide power to three other airplanes.


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Wow Pb, That is good news. Is this with the same two blade plastic prop? What blade angle did you settle on? What is the approximate area of the blades in square inches?
 
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No alternative to a good prop. Unless your a machinist with a big hunk of Delrin, you're not going make this one.


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Is that about 12" in diameter? Did you notice any more drag with this one when compared with the other prop? I'm trying to get my head around the amount of drag which is generated by the spinning prop. My thinking is that with more blades the drag will be higher. When the air is pushing the prop the drag will be there unlike when the prop fan is driving the air.

I used to fly a Fairchild FH-227 which had a long four bladed prop. Upon landing the blade pitch was placed in zero pitch angle (ground fine) to reduce the load and temperatures on the turbine engine. Then when the rpm was increased the drag also increased. This was very noticeable.
 
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