Windmill Pt250-Blade-Plan10A-Savonius.pdf

PicoTurbine 250 Plans

Part 1: Blade Design

Instructions and Technical Notes

An easy to build and inexpensive Savonius blade

design for use with the PicoTurbine 250 alternator.

BETA

This is an unproven design meant for

experimentation only. This plan is intended for

adults.

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THESE PLANS ARE PRESENTED IN “AS IS” CONDITION. BY USING THESE

PLANS YOU HOLD PICOTURBINE.COM, XIBOKK RESEARCH, AND ALL

MEMBERS, INVESTORS, EMPLOYEES, AND OWNERS OF THOSE

ORGANIZATIONS HARMLESS FROM ANY DAMAGES ARISING FROM THE USE

OF THESE PLANS OR THE RESULTING MACHINES. IN NO CASE SHALL

PICOTURBINE.COM OR XIBOKK RESEARCH BE LIABLE FOR ANY INCIDENTAL

DAMAGES. THESE PLANS ARE NOT WARRENTEED FOR FITNESS FOR ANY

PARTICULAR PURPOSE.

Revision 1.0A, October 1999

www.picoturbine.com

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CONTENTS

INTRODUCTION.............................................................................................................................................. 4

Design Patent Information.............................................................................................................................. 4

Modular Design.............................................................................................................................................. 4

CONSTRUCTION TIME................................................................................................................................... 4

BEFORE YOU BUILD THE BLADES .............................................................................................................. 4

Step 1: Check Your Materials ......................................................................................................................... 4

Step 2: IMPORTANT: Review Safety Rules ..................................................................................................... 5

BUILDING THE BLADES.................................................................................................................................. 6

BUILDING A BLADE SEGMENT.................................................................................................................... 6

Step 1: Building the Blade Supports ................................................................................................................ 6

Step 2: Attaching Blade Supports to PVC Pipe ................................................................................................ 6

Step 3: Attaching the Plastic “Skin” ............................................................................................................... 6

MOUNTING SEGMENTS................................................................................................................................. 7

MOUNTING THE BLADES OUTDOORS ........................................................................................................ 7

Tree Mount..................................................................................................................................................... 7

Pole Mount..................................................................................................................................................... 8

PART 2: T E CHNICAL NOTES ........................................................................................................................ 10

INTRODUCTION............................................................................................................................................ 10

SAVONIUS BLADE THEORY ....................................................................................................................... 10

Barrel Savonius Efficiency............................................................................................................................ 10

Benesh Profile Savonius Blade...................................................................................................................... 11

Aspect Ratio and Alternator Considerations.................................................................................................. 11

ALTERNATIVE CONSTRUCTION IDEAS.................................................................................................... 11

Corrugated Plastic Characteristics ............................................................................................................... 11

Other Possible Blade Coverings.................................................................................................................... 12

HIGH WIND AREA MODIFICATIONS ......................................................................................................... 12

Reinforced Plastic Edge................................................................................................................................ 13

TEMPLATES..................................................................................................................................................... 14

Page 3.

PART 1: Building Instructions

INTRODUCTION

The PicoTurbine-250 project is an ambitious research effort, with the goal of creating a set of plans for a 250 watt

wind turbine that can be built for $1 per watt or less by a person of average mechanical skills in one to two days.

These plans are for the blade design of the PicoTurbine-250 project. Two other documents will be a part of this set:

Part 2 will give the alternator design, and Part 3 will present the design for a load controller that maintains optimal

rotor loading.

The reason for this separation of plan documentation is that one could theoretically use a different blade design with

the same alternator, or vice versa one could use a different alternator or generator with this blade design. For

example, one could potentially use a surplus DC motor (used as a generator in this case) with this blade design, or

one could design a Darrius style blade for the PicoTurbine-250 alternator. Please note, however, that precise

matching must normally be ensured between blade specifications and alternator specifications.

Design Patent Information

This blade profile is loosely based on a profile documented in US Patent 5494407 by the inventor Alvin H. Benesh.

There are differences between this profile and the one documented by Benesh. It is unclear whether this blade design

infringes on Mr. Benesh’s design. US patent law allows you to build a patented design for your own testing

purposes, but you may not sell the resulting machine for commercial profit. For this reason, PicoTurbine.com only

furnishes plans for the blade design, we do not furnish any finished parts, you must make them yourself and you

must not sell them to others. If you wish to produce a commercial product based on this design, you must contact

Mr. Benesh and negotiate appropriate license fees with him to do so. For his address, go to

http://www.patents.ibm.com and search for the patent number above. Alternatively, you could modify the blade

profile so that it implements a design that is not covered by any active patent. There are several expired patents for

Savonius blade designs which are quite serviceable.

Modular Design

The design allows you to build blades in 4 foot [1.2m] tall segments. Multiple segments may be attached together to

attain a larger swept area. The PicoTurbine-250 alternator will require 2 segments, resulting in a blade 8 feet [2.4

meters] tall and 2 feet [600mm] wide, with a corresponding swept area of 16 square feet (1.47 square meters).

You could decide to build more or fewer segments to suit the needs of generators other than the PicoTurbine-250

alternator, however there are practical considerations as the number of segments increase. See Part 2: Technical

Notes for details.

CONSTRUCTION TIME

You should allow approximately 1 hour to build each segment, with some additional time to assemble all the

segments into a single rotor. For assembly of four segments, allow approximately 1 hour. Thus, to build the entire

blade set for a PicoTurbine-250, allow approximately 5 hours. Your actual building time may be more or less than

this depending on how good your tools and skills are. For example, having built many test models, we can now build

one segment in approximately 30 minutes. There is also some savings when building multiple segments in one

sitting. For example, once you cut out one blade support you can use it to easily mark the wood for all the supports

you need and cut them out at one time, the same goes for drilling holes and other tasks that must be repeated for

each segment. This saves you time switching between tools, changing drill bits, etc.

BEFORE YOU BUILD THE BLADES

Step 1: Check Your Materials

The following materials are needed to build the PicoTurbine 250 blade set:

Page 4.

¤ An 8-foot by 4-foot piece of corrugated plastic cut into 8 sections two feet square. Corrugated plastic

can be obtained from plastics supply houses or sometimes from sign supply or sign making companies.

We use 2mm thick plastic, but that is usually hard to find. The most common is 4mm which will also

work.

¤ An 8-foot long piece of pressure treated 4x1 wood, cut into 2 foot lengths.

¤ 24 angle brackets approximately 2 inches long (each side is 2 inches) and ¾ inch wide.

¤ A 10-foot section of 1.5 inch diameter PVC pipe. This must be cut into two sections each four feet

long (there will be a couple of feet left over).

¤ A 10-foot piece of 1 inch diameter galvanized water pipe. This is available at any large hardware store

or plumbing supply store.

¤ A 4-foot section of 1 inch black pipe and a floor stand (sometimes called a flange) for 1 inch pipe, and

a “T” connector for a 1 inch pipe.

¤ Eight pipe clamps, 2 inches in diameter. These are metal strips with a screw that allows them to be

tightened around a pipe.

¤ Approximately 100 screws. They should be about ¾ inch long and should have a rather large pan head.

Number 8 screws are ideal.

¤ Approximately 100 washers of a size that fits the screws above.

¤ Four ¼ inch diameter bolts, 2 inches long.

¤ Approximately 10 inches of teflon tape, ½ inch in width or more. This item is optional if you have

trouble finding it. We bought ours from Grainger (www.grainger.com).

¤ Approximately 25 feet of 3/8 inch plastic coated steel cable.

¤ A pulley rated at 100 pounds for a 3/8 inch cable.

¤ Four wire rope clamps.

The following tools are needed:

¤ An electric hand drill with a 2 inch wood cutting bore. Also, a ¼ inch metal cutting bit (such as a

cobalt bit), and a 1/8 inch bit for drilling pilot holes in wood.

¤ A jigsaw, saber saw, coping saw, or some other saw capable of cutting curves in wood.

¤ A screw driver or screw driver attachment for the drill.

Step 2: IMPORTANT: Review Safety Rules

The PicoTurbine-250 blade set is not a dangerous project to build, but as with any construction project certain safety

rules must be followed. Most of these rules are just plain common sense.

¤ This project is experimental in nature. There may be unknown risks associated with building this

project, this list of risks does not purport to be complete. This project is intended only for adults who

are willing to experiment.

¤ The tree-mount described in this project is undesirable from a number of standpoints. The tree may

suffer damage or be killed, so do not mount this project on any tree you are not willing to put at risk.

Be certain to have a good footing and use a stable ladder when attaching parts. Pole mounting is

preferred.

¤ The pole mount described in this document is experimental in nature and has not undergone

extensive testing. Construct it according to the rule: “build it so it can never fall down, and place it

expecting that it absolutely will fall down.” Place this structure in an area where it will not damage

property if it falls, and away from areas frequented by people or animals. If you are unsure of

whether you are building the structure securely enough, consult a local engineer.

Page 5.

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