RC helicopter rotor blades.
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tahustvedt
- Vectric Craftsman
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RC helicopter rotor blades.
I made these for a friend today. They were cut from oak using a 6 mm ball mill. They have a thin semi-symmetrical airfoil for high efficiency. I have made a few blades like these for friends lately and they fly great. Milling them was challenging and it took a few tries before I figured out how to keep the thin, long parts in place while cutting and now I have figured out a method that lets the machine do all the work without using tabs that need to be cleaned up afterwards.
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DavidCousins
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- Location: Huntsville, Alabama
Wow, that's outstanding! You've got to provide more pictures. And I want to know the following stuff:
1. roughing Strategy, X or Y or 3D (X or Y)
1a. Profile first or last or none?
2. bits for roughing and finishing and cutout
3. finishing machine direction. Along the blade or across.
4. How DID you hold it without tabs?
Those blades look great. Thanks for sharing.
1. roughing Strategy, X or Y or 3D (X or Y)
1a. Profile first or last or none?
2. bits for roughing and finishing and cutout
3. finishing machine direction. Along the blade or across.
4. How DID you hold it without tabs?
Those blades look great. Thanks for sharing.
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studysession
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I too 2nd the above. Fantastic work. Also intrested in who you balance the blades?DavidCousins wrote:Wow, that's outstanding! You've got to provide more pictures. And I want to know the following stuff:
1. roughing Strategy, X or Y or 3D (X or Y)
1a. Profile first or last or none?
2. bits for roughing and finishing and cutout
3. finishing machine direction. Along the blade or across.
4. How DID you hold it without tabs?
Those blades look great. Thanks for sharing.
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tahustvedt
- Vectric Craftsman
- Posts: 107
- Joined: Mon Sep 03, 2007 9:08 pm
I use Discreet Plasma for the modelling. It works about the same as 3D Studio Max but without the rendering and some other stuff. It can export VRML (.WRL) files. I think I'll get Max some time in the future but I gtta save up first. 
To draw the blades I first lofted a profile, then I booleaned away some bits at the root and tip, and made a root mounting surface shape.
In the drawing above you see some 2D shapes around the blades. These ar for vutting out the alignment holes and bolt holes in VCarve 4.5. The two 6 mm holes, one on each end of the parts, are used for precise alignment when I turn the piece around. The four smaller holes are used for securing to the table with screws. To keep the 3D and 2D drawings alogned I always center the center of the part to the "world" zero because that keeps them aligned in both Cut 3D and VCarve.
In Cut3D I create separate profiles for the top and the bottom surfaces because that gives me more control of the process and placement in the material. I don't like to use tabs on the blades because they are so thin and it's difficult to get the tip shape right when I sand the tabs away later. The process is as follows:
1 - Drill the alignment holes and bolt holes using the Vcarve code.
2 - I make the bottom of the blade first. Since these blades are flat on the bottom I cut the bottom of the blade into the surface of the wood, as shallow as possible. That way it lies flat on the table after I turn it around so that it has better support. I don't create a roughing pass, I just finish right away with 0.2 mm stepover and raster along X, which is along the blade.
3 - Then I turn the blade around and do a Z level X raster roughing pass to get through the 14 mm thick piece of wood. I use a 9 mm silhouette and 5 mm machining allowance here because that leaves enough material left on top of the blades to hold them flat on to the table as they are milled, and the silhouette makes sure the finishing tool doesn't have to dig through the full thickness of the wood later on.
4 - After that I do a finishing pass like I did on the bottom surface. Raster along X with 0.2 mm stepover. Since the bottom surface of the blade was milled flush with the surface of the wood that's now lying against the table, and since the roughing pass left 5 mm of wood on top the blade is supported all the way and won't flex up or down while it's being cut. I have to cut a few mm into the table to cut out the shape completely because I use a 6 mm ball end mill.
5 - To make sure the blades stay put without tabs as they are cut out I use clamps. When the machine has almost finished a blade I put three clamps on the table to hold the trailing edge of the blade down along the blade as the last few mm of the leading edge are milled out. I just pause in Mach 3 when the raster it at one end and continue after the clamps are on.
The whole process takes between 60 and 90 minutes for two blades in one go.
I havent' balanced the blades. I leave that to my friends since they seal and finish them. They usually end up with a less than 1 g difference in weight straight off the router. We tried flying with a set of unbalanced blades straight from the machine and they flew perfect. No vibes and perfect tracking.
I will make some large blades for a project of my own soon. They need to be 750 mm long so I have to mill one half end first and then turn the wood around to mill the other end.
To draw the blades I first lofted a profile, then I booleaned away some bits at the root and tip, and made a root mounting surface shape.
In the drawing above you see some 2D shapes around the blades. These ar for vutting out the alignment holes and bolt holes in VCarve 4.5. The two 6 mm holes, one on each end of the parts, are used for precise alignment when I turn the piece around. The four smaller holes are used for securing to the table with screws. To keep the 3D and 2D drawings alogned I always center the center of the part to the "world" zero because that keeps them aligned in both Cut 3D and VCarve.
In Cut3D I create separate profiles for the top and the bottom surfaces because that gives me more control of the process and placement in the material. I don't like to use tabs on the blades because they are so thin and it's difficult to get the tip shape right when I sand the tabs away later. The process is as follows:
1 - Drill the alignment holes and bolt holes using the Vcarve code.
2 - I make the bottom of the blade first. Since these blades are flat on the bottom I cut the bottom of the blade into the surface of the wood, as shallow as possible. That way it lies flat on the table after I turn it around so that it has better support. I don't create a roughing pass, I just finish right away with 0.2 mm stepover and raster along X, which is along the blade.
3 - Then I turn the blade around and do a Z level X raster roughing pass to get through the 14 mm thick piece of wood. I use a 9 mm silhouette and 5 mm machining allowance here because that leaves enough material left on top of the blades to hold them flat on to the table as they are milled, and the silhouette makes sure the finishing tool doesn't have to dig through the full thickness of the wood later on.
4 - After that I do a finishing pass like I did on the bottom surface. Raster along X with 0.2 mm stepover. Since the bottom surface of the blade was milled flush with the surface of the wood that's now lying against the table, and since the roughing pass left 5 mm of wood on top the blade is supported all the way and won't flex up or down while it's being cut. I have to cut a few mm into the table to cut out the shape completely because I use a 6 mm ball end mill.
5 - To make sure the blades stay put without tabs as they are cut out I use clamps. When the machine has almost finished a blade I put three clamps on the table to hold the trailing edge of the blade down along the blade as the last few mm of the leading edge are milled out. I just pause in Mach 3 when the raster it at one end and continue after the clamps are on.
The whole process takes between 60 and 90 minutes for two blades in one go.
I havent' balanced the blades. I leave that to my friends since they seal and finish them. They usually end up with a less than 1 g difference in weight straight off the router. We tried flying with a set of unbalanced blades straight from the machine and they flew perfect. No vibes and perfect tracking.
I will make some large blades for a project of my own soon. They need to be 750 mm long so I have to mill one half end first and then turn the wood around to mill the other end.
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tahustvedt
- Vectric Craftsman
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- Joined: Mon Sep 03, 2007 9:08 pm
I decided to finish this set off this morning. The root doublers were cut from 0.5 mm fibreglass using VCarve and epoxied on. A brass sleeve strengthens the mounting hole. The blades are sealed with two layers of thin epoxy resin and sanded smooth for a nice finish. They ended up at the same weight.
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tahustvedt
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- Joined: Mon Sep 03, 2007 9:08 pm
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DavidCousins
- Vectric Wizard
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- Location: Huntsville, Alabama
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blownaway-ig
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- Joined: Thu Nov 22, 2007 3:39 am
RC heli blades
WOW,,,I do have to give you big time credit for doing up a set of blades. Looks like great work,,,,And I can only imagine the time and skill that you put into them.
Are you going to fly them? From the multi blade head, do you fly scale?
I've been flying for sometime, and one of the things that I have always hated it building blades.
I just recently purchased a Shopbot Buddy and am looking forward to seeing what i can create in the future when i get proficient with it and the software. Have you considered cutting scale fuse plugs?
Anyways, I give you alot of credit for your skill and patience.
David Sanchez, EagleGrafix@msn.com
Are you going to fly them? From the multi blade head, do you fly scale?
I've been flying for sometime, and one of the things that I have always hated it building blades.
I just recently purchased a Shopbot Buddy and am looking forward to seeing what i can create in the future when i get proficient with it and the software. Have you considered cutting scale fuse plugs?
Anyways, I give you alot of credit for your skill and patience.
David Sanchez, EagleGrafix@msn.com
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tahustvedt
- Vectric Craftsman
- Posts: 107
- Joined: Mon Sep 03, 2007 9:08 pm
I fly scale, aerobatic and photo helis (and planes). Here are some of my videos: http://www.youtube.com/profile?user=tahustvedt
The six blade tail rotor will fly in a few months. I haven't started building the fuselage yet. It will be a built up wood construction. The blades will be 750 mm long and a real challenge to mill.
The six blade tail rotor will fly in a few months. I haven't started building the fuselage yet. It will be a built up wood construction. The blades will be 750 mm long and a real challenge to mill.
..maybe I'll just buy some heli blades instead.-
tahustvedt
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- Posts: 107
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Today I tried a new approach to milling blades. These blades are very complicated. They are semi-symmetrical and have 3° of twist along the length. They are also a lot longer than my CNC could mill in one run, so I had to do it in four steps. Top and bottom for each end of the long wood. The rotor diameter is ~1437 mm.
I have to mill two more for my new helicopter. CNC is so useful I can't believe I how primitive I was before.
I have to mill two more for my new helicopter.
CNC is so useful I can't believe I how primitive I was before.- Attachments
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tahustvedt
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- Posts: 107
- Joined: Mon Sep 03, 2007 9:08 pm