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Forum Index : Windmills : Windmill kit on website

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imsmooth

Senior Member

Joined: 07/02/2008
Location: United States
Posts: 214
Posted: 01:05am 11 Apr 2008
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I was looking at the DMX files at
http://www.thebackshed.com/Windmill/Kits.asp

Are the spline pieces really 8mm thick? That's pretty thick steel. Is this right? I'm asking because I am designing the piece for laser cutting and I want to use the correct thickness. The blades will be 8-9' so there will be alot of torque.
 
brucedownunder2
Guru

Joined: 14/09/2005
Location: Australia
Posts: 1548
Posted: 01:32am 11 Apr 2008
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IM,,,
Trev from foundry and fibreglass on this site makes a nice cast Aluminium hub for your blades that is bored and splined for the F&P shaft--being Aluminium ,,it would not be too expensive to freight to you ,,,ask Trev..

Glenn made the steel plates with laser cut ribs in them to accept the F&P shaft ,,long time back.

Bruce
Bushboy
 
Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5116
Posted: 02:34am 11 Apr 2008
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Hi IM

Yeah it was 8mm plate, but the end result was not that good, not pretty at all. I later made them from 3mm plate, and would stack several to get the thickness. Using 3mm plate is the way to go, give 8mm a miss.

If you want a good laser cut spline, ask the laser operator to cut them using high pressure nitrogen. HP N2 gives a fine cut compared to normal laser O2 cutting, but its much more expensive. So ask to have the splines cut in HP N2 and the rest normal oxy cut. It would help if you can supply them with the spline so they can get the offset correct for a nice fit.

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

Senior Member

Joined: 07/02/2008
Location: United States
Posts: 214
Posted: 03:22am 11 Apr 2008
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This whole process must be expensive for a few piece. Prohibitively expensive?

Besides the precut pieces is there any other way to go to fix the hub?

Meanwhile, I'm going to reach out to Trev.
 
Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5116
Posted: 10:55am 14 Apr 2008
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Lasercutting isn't that expensive if you do your homework before visiting the local laser ( or waterjet ) cutting business. Actually cutting out the parts from a sheet of steel is only a small part of the process ( a 2500 watt laser can cut 6mm steel at over 2 meter per minute!), its getting the job ready to cut that usually takes the time, and this adds to the cost.

If you show up at the laser cutter with a scrap of paper with some lines and a couple of dimensions, or worst still, a paper cut out of the shape you want, then he will need to interpret your drawing, ask a bunch of questions like "Whats that hole diameter?", "Whats the radius on this corner?", "Is that meant to be a straight line?", etc. Remember, your paying for his time.

You see, he needs to draw this shape in CAD on his computer, so he needs to know EVERYTHING! Every little corner and circle and radius and length. If he has to manually measure your bit of paper, then its going to cost ya. And he wont make a guess on any measurement, if its not know he will call you up to find out what it is.

But if you can present him with a fully dimensioned drawing, you will save his time and your money. A even better option is to give him a DXF or DGW file on disk. No not a JPG or BMP or GIF, these are raster files and worthless, he wants a vector file, like DXF or DWG. Then all ne needs to do is import the file, add a few details like offset , sequence and leadin's, and the files ready to send to the laser cutter.

Typically, this is how a job is broken up. There's a base charge, like $30, and then a CAD charge, charged at something like $80 per hour. So if it takes 30 minutes to turn your paper cutout into a laser ready file, then thats $40. You pay for the cost of the material, but steel is cheap and will only be a small part of the cost. Then there is the laser cutting, charged at something line $5 per minute. Those spline plates would take about a minute each, or if you go for nitrogen cutting, slight longer charged at $6 per minute, maybe $8 per unit.

Remember the DXF file for those spline plates is
here, so you could take this file in to a laser or waterjet cutter and ask them for a price on cutting the spline plates. It should cost less than $100 for a set of 4 3mm plates, in fact it should be closer to $60 give or take.

Dont forget to mention the DXG file and measurements are in metric, or you could end up with a spline 3 feet in diameter!

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ
 
carl1
Regular Member

Joined: 16/04/2007
Location: Australia
Posts: 79
Posted: 01:29pm 16 Apr 2008
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Hi Glenn
Last sentence gives me a good laugh: spline 3 feet in diameter.. just imagine the size of the blades for it!! Harald
 
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