TheBackShed.com

Forum Index : Windmills : PVC Extruded blades feedback?

Page 2 of 2

Author

Message

Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5119

Posted: 02:31am 23 Jul 2009

Copy link to clipboard

Print this post

Clever thinking Anthony. Not only would it keep the blades on if the rivets fail, but it would stop the whole blade leaving the scene if the hub failed. The picture in Anthony's post is of the OEM windmill that's under development, and I've heard they have now redesigned the hub to make it stronger.

As Phill has shown through his own tests, 6 rivets will hold up in a extreme condition. 700RPM on a 3.1m diameter is pretty extreme.

So, in the name of safety, I would recommend a minimum of 8 rivets per blade ( 4 each side ) for a turbine over 3m diameter, 6 rivets for a turbine under 3m diameter. The rivets should have a 5mm shank, and preferably stainless.

Adding more rivets will have little effect on weight or performance, so you might as well as add a couple extra to be sure.

The only known cases of a blade sliding off the tube were the OEM prototype windmills. Their blades only had 4 3.5mm rivets per blades. OEM have since addressed this issue.

Also worth noting these PVC blades can quickly overpower a F&P Smartdrive based windmill. When a F&P over speeds it goes into saturation and hits a bit of a wall, maxing out at about 300 to 400 watts per stator. Electric braking alone is not enough to pull up a over speeding F&P windmill, you should have some sort of furling system in place, or a mechanical brake.

With the correct number and type of rivets, and a furling system, I dont think there is any reason why a blade should come off.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

dwyer
Guru

Joined: 19/09/2005
Location: Australia
Posts: 574

Posted: 03:36am 24 Jul 2009

Copy link to clipboard

Print this post

Glenn
In my last message that why not use aircraft gasket glue or use Dyna Copper RTV silcon casket maker glue on tha tube easily can be done by lay the glue along one side or both side and inert the tube into the blades and turn the tube around until glue cover inside blade's hollow and pop rivet and this will help by extra crip less slipping out at higher rpm ???
and Anthony"s wire ideas drilling hole and wire around is great however my ideas is why not place cable at the tip of the blades with spring or small turn buckle same as you use now

Dwyer the bushman

Page 2 of 2

Print this page

To reply to this topic, you need to log in.