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Old 05-31-2015, 05:36 PM   #1 (permalink)
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Default The Oblivion 300+ - a microheli project

Heyho guys!
just want to tell you something about the Oblivion 300+ and show you the first flight videos. This heli is a non commercial (!) project of my friend Chris and myself. He builds it, then I try to break it. Great combo, even though I didn't succeed yet (luckily)

The goal of this project was to design a 300 size heli capable of delivering a great performance with less than 5000+ rpm.

The whole helicopter is designed be extremely light, just around 400g. It can swing blades of a length around 250mm over the operating rpm range from about 1600 up to a maximum of 3300 (rpm ratings not finalized yet). This allows you to reach 4 minutes flight time flying full 3D at high rpm with ~20% battery charge left or just cruise around forever at low rpm.

The project is still in development, some aspects may change over time. If you want more info, head over to http://www.oblivion-heli.com/

And of course, as promised, VIDEOS!





Best Regards,
Jonas
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Last edited by Johnny31297; 06-05-2015 at 09:42 AM..
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Old 05-31-2015, 06:20 PM   #2 (permalink)
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The greatest annoyance that I've had with small helis was a weak tail.

How did you guys go about coming up with an appropriate tail gear ratio to keep it from blowing out during taxing maneouvers? Obviously it works GREAT in the video. Very cool!
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Old 05-31-2015, 06:29 PM   #3 (permalink)
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Quote:
Originally Posted by Fauropitotto View Post
The greatest annoyance that I've had with small helis was a weak tail.

How did you guys go about coming up with an appropriate tail gear ratio to keep it from blowing out during taxing maneouvers? Obviously it works GREAT in the video. Very cool!
That's a good question! Our tail ratio actually isn't that good. 1:3,83. The secret to it working so well are, honestly, huge tail blades. I'm currently using mCPX KBDD rotor blades cut down to 56mm.
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Old 05-31-2015, 06:57 PM   #4 (permalink)
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Amazing... 4 minutes of hard flying... And the simple design is open source to boot.

The folks over at rcg will love this. This is truly a back to basics helicopter.



EDIT: Added vidcap image
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Old 05-31-2015, 08:08 PM   #5 (permalink)
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Hey, we have nothing to hide, no need to go through the expense of taking screenshots, just could have asked for pictures
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Old 05-31-2015, 09:25 PM   #6 (permalink)
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Very nice! How did you manufacture your parts? Did you 3D print them or get them made from a prototyping house or something?
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Old 05-31-2015, 09:30 PM   #7 (permalink)
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The are 3D printed.

I am surprised this works for the main grips, especially.
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Old 05-31-2015, 10:17 PM   #8 (permalink)
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3d capable 2200rpm 300 size? I'll take one please. Should go nicely with my other 'low headspeed' ultralight helis.

What does it cost roughly to get all the bearings and bits and have it printed?
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Old 06-01-2015, 02:40 AM   #9 (permalink)
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Quote:
Originally Posted by Code3Medic View Post
The are 3D printed.

I am surprised this works for the main grips, especially.
Holy...

What plastic?

Amazing stuff!

What about the swash? Plastic as well? Or painted alloy?
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Old 06-01-2015, 03:14 AM   #10 (permalink)
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Hi folks,

thanks for the warm words

To clarify a few aspects here: It is not 3D printed, but manufactured via selective laser sintering. Since Shapeways (anyone knows any other services here?) this has become accessible to the public. Plus it is pretty light. The entire chassis weights 34 gramm.

@ prototype3a: 3d capable, yes i think that is a flexible term. the bird becomes flyable with very good control over tail and cyclic at 1900 RPM already. 2200 enables you to do a few loops, slow tic tocs etc. 2400 is pretty much enough for everything I can fly - of course the youth (a.k.a. Jonas) requires more "music in the box", as we Germans say - ha ha. 3.000-3.300 RPM is everything you should need i guess. But figure out yourself.

@ Fauropitotto: 100% agree to that. That was one of the main reasons for me to do it, the tail is very, very controllable and accurate even at 1900 RPM. Plus we can change ratio, blades etc. whatever is required. I did not want any compromise here, by the end of the day the helis is just as good as it's tail performance. It is not comparable to Hornet, Piccolo etc., more to the T-rex 450. We are running a full t-rex 450 sport tail on it (except tail box). I am working on thrust bearing support and SLS grips atm, but have limited time I can spend on this project...

Note that it is 300+, which translates into around 60cm main rotor diameter. The Maxir inspired me in that regard.

Hope to help.

@Jonas: Thanks for posting the vids!
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Old 06-01-2015, 06:18 AM   #11 (permalink)
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Quote:
Originally Posted by spykez View Post
Holy...

What plastic?

Amazing stuff!

What about the swash? Plastic as well? Or painted alloy?
Appears to be plastic... From the Oblivion Getting Started page:
  • 1x Swashplate inner (STL | Shapeways)
  • 1x Swashplate outer (STL | Shapeways)
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Old 06-01-2015, 06:40 AM   #12 (permalink)
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Any idea how the frame holds up in a crash yet?
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Old 06-01-2015, 06:56 AM   #13 (permalink)
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Very cool
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Old 06-01-2015, 06:59 AM   #14 (permalink)
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all the white colored stuff is the pliable-plastic 3d printed.

If you look at how much room is between the root end of the blade and the furthest section of cutaway of the grip/clamp the bolt holes should can be much closer to the hub, pull them in to 2or3mm close to the inner grip cutaway.

It's funny how everyone complains about getting more tail authority when it's as easy as not shadowing the tail rotor with huge long mains, the tails need clean air to get a good bite and because the main blades are so high above the boom the tails suffer from a lot of downwash by the time they have a chance to perform properly. It isn't easy going shorter on the mains, it's just the right thing to do.

140* swash plate is equal pitch travel and maybe half aileron, it looks like it helps with servo placement.

The esc can be a 35amp (CC Talon is half the size and weight) no problems.

My 300x had adapted a strutless 12mm boom more than a year ago, I found cf to be a little sensitive so I used shortened align aluminum boom(s) and haven't looked back. Frames are beat even with support plates the boom clamp area has had it, fini, so that becomes an area of contention that the boom has less support than with struts in a crash = broken frame at the boom.

I uploaded a chassis file and will see what it costs to get one made, if it was $2 a square cm of material it should be competitive with all other offerings. Because your open source this means anyone should be able to alter the design as they see fit, ya?

Now go tits to the wall and put 4s and fly the snott out of it why don't you? The design makes me think if LOGO made a 300, this is what it would look like, good job and nice flights, I want to see high hs on 4s now. On the other end at low hs it should be able to lift at 800rpm.

I see Microheli referenced on your website, are there any affiliations to them?
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Old 06-01-2015, 07:00 AM   #15 (permalink)
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Quote:
Originally Posted by Johnny31297 View Post
That's a good question! Our tail ratio actually isn't that good. 1:3,83. The secret to it working so well are, honestly, huge tail blades. I'm currently using mCPX KBDD rotor blades cut down to 56mm.
That is a good ratio. Similar as the one in the Warp. Oversized tail grips will also help to build a nice disk, with the bonus of being able to hold nicely sized bearings, that will allow long life and precise movement. Tiny bearings suck
Miles better than so many helis in the market with badly designed setups, that force pilots to run at high headspeeds or to use some specific tail blades to perform.

Liked the flight performance a lot, it moves like a feather
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Old 06-01-2015, 08:17 AM   #16 (permalink)
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Quote:
Originally Posted by Icanfly View Post
...

I see Microheli referenced on your website, are there any affiliations to them?
I'm wondering if it's just all the bits they could not fab, like fasteners, bearings, main gear etc.. maybe the cf boom and metal tail.

Well done, guys.

I never would have thought the plastic you could print would do main grips! Nor a swash!
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Old 06-01-2015, 08:21 AM   #17 (permalink)
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I feel like it should be mentioned that SLS is not the cheap 'everyone has one' 3d printer using PLA filament. SLS is Selective Laser Sintering...
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Old 06-01-2015, 08:39 AM   #18 (permalink)
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Wow, what a seriously cool project!

In the last year Ive built 2 lightweight machines myself (although no 3D printing was involved), a 250 size heli with 200g AUW and my lightweight Mini Protos (750g AUW) and can attest to the advantages of lower weight/HS.

The model bloat the heli hobby has seen for the past years (more power, more HS, high disc load, then stretch, add more power etc) is somewhat stupid IMO. Im really happy to see someone else has had enough and bucks the current trend, even if that means you have to build your own machines.

Besides the nice model the project also highlights how this hobby can evolve in the coming years. Open source design and local printing will give traditional manufacturers a run for their money, but will also create new possibilities for them if theyre smart enough. Imagine you do not have to order replacement parts, just print them out!

Just a word on servos: Ive noticed you used the usual micro metal case servos (KST 300, MKS 95...). Nice performance, but heavy. For cyclics I recently stumbled upon the newest wing servo for DLGs from KST, the X08. Judging from the specs they should even work on 450 size helis and weigh only 8g. Over on the 250s forum one user has similar ones in use on his TRex. Hobbyking also has a new metal cased servo for 250 size helis, they weigh 16g instead of the 20g for the normal micro size. Anyway, Im sure you did servo research yourself, but just wanted to share the info just in case.

Thanks for sharing this great project!
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Old 06-01-2015, 08:42 AM   #19 (permalink)
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I was thinking the same thing but why not use Futaba s3156mg? I ran those on my 450 years ago and they were great. They're also only ~10g.
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Old 06-01-2015, 09:00 AM   #20 (permalink)
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But... but... they are metal cased, so they must be betterer

In all seriousness, Ive the Hitec 5065 on my MiniProtos right now, which are around the same 10g. The KST X08 cost around the same over here and if youre after the last few grams they may be an alternative. Totally untested on a heli of course, just judging from the specs (which are much better than the HiTecs, at least with a HV BEC) . I have no idea how manufacturers classify their servos for different purposes.
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