Propeller Gaurd

[pyronaught]

This is part of an RC blimp project I'm working on which carries two engines with 10x5.5 propellers. I used to have to make these blade guards out of sheet aluminum using a sheet metal roller, which is a big pain, doesn't look as nice and weighs more. A 1cm square ABS beam with a 1.8mm wall thickness and 10% infill has an effective density of .37g/cc relative to it's volume, which is still twice as much as balsa wood but a lot stronger. The M2's build platform being long in the Y direction really helps out with building ring segments like this, making it possible to build a 12" diameter ring in four quadrants instead of five or six. Each quadrant is printed in halves in order to eliminate the excessive amount of support material that would be required for building it as one piece. This also cuts the print time in half, which is 2.3 hours per quadrant. Coast has to be turned off for these parts, otherwise the struts come out looking like they got eaten by termites.

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[jimc]

cool! that is the one downfall of coasting. on detailed prints it needs to be turned down or off. wipe feature still works well as a middle ground. on another note, i see rhino is open. what is the bar all the way on the right with the penguin?

[pyronaught]

That's the command help panel. My screen is big enough that I don't bother closing it, even though I don't look at it too often. It loads a list of steps for whatever command mode you are in, and the picture usually changes to something that goes along with the description. The penguin is the picture that shows up when you are in Pan mode in perspective view. I guess they could not think of a good picture for that one so the penguin got the role. When learning the software that command help panel really does help a lot though.

[pyronaught]

Next printed object for this project is a ring bearing, also called slew ring. There's a guy on thingiverse who successfully made one so I know a functional ring bearing can be made on a 3D printer. I was concerned that the tiny trough that the ball bearings roll in would not be smooth enough to work, but I guess it is sticky at first but then smooths out once you run it in. Kind of like printed threads.

[jimc]

ahhh! yes i knew it looked familiar but just didnt know from where. on any software i for some reason never use the help panel. i have had that open before though and remember it being about the best help window i have ever seen with little embeded videos showing you what to do and it follows along with you and what command you are in.

i have printed a bearing before. while its cool for display and making people go wow, its very sloppy and the balls arent perfectly round

[pyronaught]

i have printed a bearing before. while its cool for display and making people go wow, its very sloppy and the balls arent perfectly round

I'm not printing the balls, I'm using standard steel ball bearings. Only the ring parts are printed. I'm going to start out with 1/8" balls and see if I can get away with that on a 4" diameter bearing. I need it to be as light weight as possible, which is the problem I run into when trying to just buy a commercial ring bearing.

The ABS parts with low infill have a pretty decent strength to weight ratio. The ring above weighs 95g, whereas if I rolled one out of .025" thick sheet aluminum to the exact same size it would be 124g not including seam overlap and rivets to hold the two halves together. The aluminum vibrates from the motor and makes a loud annoying sound too. Carbon fiber would beat it, and maybe even regular fiberglass, but at considerably more labor and cost. There's no reasonable way to make a ring bearing out of carbon fiber or fiberglass though.

[jimc]

i see, so just the races will be plastic. the balls will roll on them. i assume this is nothing that is actually spinning where heat will be generated. this will just be for rotational support or something like that. your prop assembly for instance pivoting left or right. top white section on the screen.

[pyronaught]

i see, so just the races will be plastic. the balls will roll on them. i assume this is nothing that is actually spinning where heat will be generated. this will just be for rotational support or something like that. your prop assembly for instance pivoting left or right. top white section on the screen.

Exactly, that's where it's going. No rapid rotation at all.

[sthone]

Very Cool, I hope you plan on showing off the finished blimp when it's complete.

-Steve

[pyronaught]

Very Cool, I hope you plan on showing off the finished blimp when it's complete.

-Steve

It will probably take the better part of a year to finish it, there's still lots of work to be done. Last year I built a 6ft x 16ft CNC fabric cutter for cutting film and fabric then developed a temperature controlled heat roller for it and a process for sealing film. Now I have an automated way of producing precise blimp envelopes with precision seams.

http://youtu.be/zYXIaeAq4X0

That's an older version of it, the clacking sound has been resolved and the heat wheel has been redesigned to produce narrower seams. The noise is mostly from the vacuum table holding down the film. That's a small test blimp there, the one I'm working on will probably take up the entire length of the table. Here's a picture of the test envelope. Note how smooth the seams are compared to the wrinkled ones you typically see made from aluminized film like this. Aluminized films do not stretch, so any flaws in the seams results in noticeable wrinkles. Even as much as 1/8" deviation from the curve will cause either a wrinkle or a lump, so achieving this level of precision by hand is pretty much impossible.

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