Best design for 2' radius (4' diameter) PVC blades?

[(unknown)]

First post here,

I've finally got my hands on the exact same motor as they used here (http://www.velacreations.com/makechispito.html).

I also have 4 feet of 8" pastel-green PVC pipe and I'm about to cut it to make my blades.

My question:  I was about to use the plans from the site linked to above, but I was wondering if a better design was out there..

Thanks!

Simon

[wooferhound]

Here is an interesting design of a 2 bladed PVC prop made from a single piece of pipe

http://www.fieldlines.com/story/2003/11/11/172721/53

but you have a treadmill motor for a generator, so PVC pipe will probably not give you enough speed to make power.

[morglum]

Thanks Woof,

I did see that one and although it is very popular, the double blade design kinda put me off, but I've re-read the thread and it seems many persons are making it into a single-blade prop.

I got impatient and cut my blades according to velacreations's plan, will keep posted if it does spin fast enough for the threadmill motor.  I do have some leftovers, about 44 inches of 8" pipe, so i,ll get able to try your Zub-Woofer blades eventually

S.

[tanner0441]

Hi

One thing that bothers me is the brake switch is after the diode, if the diode fails when the switch is operated there will be no braking on the turbine.  Also why have the losses from a bridge with a DC generator when a single diode would be better.

Just a thought....

Brian.

[morglum]

Hi Tanner,

I'm not sure I really understand what you are saying (my bad, not yours).  

Would you mind elaborating a bit?

Cheers

[ghurd]

I doubt a treadmill motor using 2 parallel diodes in a 35A bridge will ruin the diodes from emergency braking, as long as the braking is done sensibly.

The velacreations wiring of the bridge is not exactly the best way to do it.

It adds an additional 0.7V diode loss.  Treadmill motors don't usually have much voltage to spare.

Sends all the power through a single diode.  Twice!

Makes twice as much heat in the bridge.

Stick with the bridge wiring sketch I sent you.

G-

[morglum]

Will do!