Homebuilt DPVs?

[diverryan]

One thing I never understood was why variable pitch props are used. What about increasing power going to moter from battery? Advantages/disadvantages?

 

[Nemrod]

A battery can only deliever so many amps over a given length of time. High capacity lithiums for example have more storage capacity for a given weight, NiCds generally have lower internal reistance and can produce very high amp flows, lead acid gell cells are cheaper and heavier but perform well--there is much more to this than I have time to write.

When using a variable pitch propeller the motor continues to turn approximately the same RPM at all prop settings. Higher pitch settings draw more amperage and lower pitch settings draw less amperage.

Voltage is like pressure
Amperage is the rate

And to complicate for example then a 12volt battery with an 18 amp/hour capacity could theoratically deleiver 18 amps at an average of 12 volts for one hour.

My Tekna at high pitch draws well over 18 amps and I am using 18 amp batreries in series for 24 volts at 18 amps/hour. At full pitch it is pulling about 24 amps and therefore my run time is about 40 minutes and at low pitch it pulls about 10 amps so I get about an hour and thrity minutes. Approximate just for sake of discussion. You can do the math if you like for exact numbers and then throw in a bit for loss due to friction, heat etc.

N

 

[JES]

.... If you notice, the shroud, prop and motor on the Tekna is the same as on many of the high dollar super scooters. The motor sits in an aluminum machined cone that can be easily adapted to a PVC type scooter construction.... The Tekna shroud screws off so it can be adapted to another scooter design and the prop is the same adjustable pitch prop which is very efficient.

N

The design of the Kort nozzle and adjustable pitch hydrofoil prop is the key to DPV design. Nemrod's advice combined with the kit by Dagodiver is excellent advice to follow!

 

[AMendez]

Thanks! That's a lot like what I'm looking for... maybe I'll just buy one of those if I can find a junked scooter to gut the motor and prop from.

I think I'd need to put a coat of paint on the housing though... that PVC gray just doesn't do it for me.

here you go

http://www.scubaboard.com/showthread.php?t=187180http://thedecostop.com/forums/showthread.php?t=24305