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Jul 13, 2019, 06:02 PM
Quadaholic
--Oz--'s Avatar
Quote:
Originally Posted by joelucid
Yet another one of these - tube failure at the motor with Kevlar mount. I suspect the problem is not so much the Kevlar mount but what's not there: the traditional wrap mounts do add strength there. With center plates with longer fingers the center isn't much of a problem. It's then the motors unless the little motor mount "arms" provide strength.
If you think about it, 90%+ arms (flat and tubes I am guessing) mostly break near the motor. My reasoning is, the motor bolted to the arm acts as a stiffener (in addition to the arm), so right next to it receives the most stress. If its not breaking there, the arm is breaking close to the center plate, I am guessing witch ever one is weaker.
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Jul 13, 2019, 06:06 PM
Registered User
Quote:
Originally Posted by SirDomsen
I like your design pretty much, I just see one big problem; Most tubes don't slide easily into each other, most have bad tolerances and need trimming/drilling before they fit.

How do you avoid this problem?
I once found some that provided "fittings" that fit inside the tubes. Nice for reinforcement at stressed sections. Not so sure if the's do for replaceable arms also?
These for example, but as most of their tubes these are pultruded ones unfortunately. In fact, these are tubes for sports kites
This involves basic gauging of IDs and ODs. Some of this involves direct measurement, and some using plug gauging. CF tubes are not precisely toleranced and a tube even changes dimensions over its length. Tubes also are not very round.

A basic ID/OD fit needs to be established and reference tube materials kept to assist gauging. My target ID is on size, and the OD would be 1-2 thousandth less. But the bottom line is the hand fit feel. Some tubes will be rejected if too far out. Some ODs can be brought down several thousandth by spinning. And the ID size is a function of the wrap tension and I can adjust this while I wrap on a metric mandrel and feel the clearance close down. I find that I can make make most of my tubing work. I now low strength bond the joint so I no longer have to sweat a crazy preciseness of the fit.

A level of experience and resources are used here.
Last edited by gc_ober; Jul 13, 2019 at 08:19 PM.
Jul 13, 2019, 06:07 PM
Registered User
Quote:
Originally Posted by --Oz--
If you think about it, 90%+ arms (flat and tubes I am guessing) mostly break near the motor. My reasoning is, the motor bolted to the arm acts as a stiffener (in addition to the arm), so right next to it receives the most stress. If its not breaking there, the arm is breaking close to the center plate, I am guessing witch ever one is weaker.
If you just have tubes connecting to a center section typically the breakage will be where the tubes connect to the center. But weíve managed that problem by using center plates that extend to the arms - like provide a bit of reinforcement. Only that makes the motors the weak section. And only with the Kevlar mounts.
Jul 13, 2019, 06:11 PM
Registered User
Quote:
Originally Posted by --Oz--
If you think about it, 90%+ arms (flat and tubes I am guessing) mostly break near the motor. My reasoning is, the motor bolted to the arm acts as a stiffener (in addition to the arm), so right next to it receives the most stress. If its not breaking there, the arm is breaking close to the center plate, I am guessing witch ever one is weaker.
Most of my tubes break at the root of the arm to the center plate. This would be expected of a load applied at the free end of a cantilever beam. But crashes forces are anything but predictable.
Last edited by gc_ober; Jul 13, 2019 at 07:06 PM.
Jul 13, 2019, 06:11 PM
Registered User
If you look at this yet unwrapped frame you can see where center plates and motor mounts will protect the tubes.
Jul 13, 2019, 07:52 PM
Quadaholic
--Oz--'s Avatar
I knew I was asking for it with that last post, lol. We all know it breaks where its weak, that is a given. Majority of kit arms have slots for the 16mm and 19mm motor mounting holes (I hate slots), this is the weak spot on the majority of frames that I have seen. The motor bolted to the arm strengthens the arm under it, and the "weak" spot is just inboard of that from my flying experience and visual experience from other arms failing, +90% have this flaw that I have seen. FYI, This has nothing to do with tubular frames.

The raptor arm has a few;
Pros:
Excellent motor protection,
No stupid motor screw slots like "most arms" break at,
rarely break, I am averaging at a minimum 10K flights before I break one into two (and I crash a lot, that would be one arm in roughly 10K flights, I have 3 broken arms in 3.5 years flying the raptor).

Cons:
$16.50 price + s/h,
no longer available,
weight,
the 3d milling is the weak spot, after a hard crash, the arm starts to splits down the middle of the 5mm cf (imo, because of the 3d milling weak spot), once it reaches half way out the arm (more crashing), only then have i broke it into two.
Jul 13, 2019, 08:01 PM
Quadaholic
--Oz--'s Avatar
Quote:
Originally Posted by joelucid
If you look at this yet unwrapped frame you can see where center plates and motor mounts will protect the tubes.
The protection need to be on the bottom of the tube, not the top where the motor mounts, I have never chipped/broke them there. After a few hard hits, the tubes will not survive. But hey, thats the price to play the lightweight high preformance game. The raptor has 16mm past the edge of the motor for protection and its 5mm solid cf, I have chipped them down to 2.5mm after many hard hits on asphalt w/o motor are or arm damage(EG, cant fly). There is nothing wrong with your design (or anybody's here), as there is tradeoffs in everything (thread name has "ultralight"!).
Last edited by --Oz--; Jul 13, 2019 at 10:19 PM.
Jul 13, 2019, 10:48 PM
FPV Addict
Yamaford's Avatar
Seriously, this thing wont die.
Jul 15, 2019, 02:02 AM
FPV Addict
Yamaford's Avatar
So I was all setup with this dumb gopro contraption on my head to show off how much I've improved sense building these los only quads. Apparently I can't fly for squat under the pressure of a gopro . I thought maybe it was because it was on my head so I set it down beside me. Nope! Still sucked. Turned off the gopro and like magic I'm the world's greatest pilot again. Oh well. I guess the world will never know. #stagefright
Jul 15, 2019, 04:27 AM
Wut wut wut
I mean you feel dumb with headmount, but I just film like 10 packs so that no flight is the one where I need to do well. I just tell myself 'oh this is my warmup pack' and don't feel pressured to do well. And by the 10th I'll just tell myself 'meh one of those earlier packs was probably good enough'.

Also FWIW at least videos only about 33% of people make it 1 minute into video, 19% 2 minutes in. So really of those 10 flights you don't even need 1 in 10 to be good, you need just like 1-2 minutes in 1 of the 10 videos to be good.

And another benefit of filming 10 flights... after spending all that time filming if you get home and can't find 1-2 minute clip that looks good, you'll be so sick of the process you'll stop caring and just say 'f-it' and post what you've got to be done with it.
Jul 15, 2019, 09:44 AM
Registered User
This seems to be a good paper on aging of lipos. Have only scanned it. Posting partially to read in more detail later: http://m.jes.ecsdl.org/content/163/9/A1872.full
Jul 15, 2019, 10:22 AM
Quadaholic
--Oz--'s Avatar
Quote:
Originally Posted by joelucid
This seems to be a good paper on aging of lipos. Have only scanned it. Posting partially to read in more detail later: http://m.jes.ecsdl.org/content/163/9/A1872.full
I have not read it yet other. The first thing it says "Impact of the Graphite Anode on Capacity Fade"

I dont think any of our batteries use graphite or graphene (yet), yep, lying marketing scam, lol. I wonder if this even applies to us?

EDIT: Scanning though the document, these are for Li-Ion 18650 cells and not Li-Po cells.
Last edited by --Oz--; Jul 15, 2019 at 12:15 PM.
Jul 15, 2019, 12:52 PM
FPV Addict
Yamaford's Avatar
Quote:
Originally Posted by bexamous
I mean you feel dumb with headmount, but I just film like 10 packs so that no flight is the one where I need to do well. I just tell myself 'oh this is my warmup pack' and don't feel pressured to do well. And by the 10th I'll just tell myself 'meh one of those earlier packs was probably good enough'.

Also FWIW at least videos only about 33% of people make it 1 minute into video, 19% 2 minutes in. So really of those 10 flights you don't even need 1 in 10 to be good, you need just like 1-2 minutes in 1 of the 10 videos to be good.

And another benefit of filming 10 flights... after spending all that time filming if you get home and can't find 1-2 minute clip that looks good, you'll be so sick of the process you'll stop caring and just say 'f-it' and post what you've got to be done with it.
Hahaha maybe it's just because I'm tired of watching fpv videos and los is the rare breed, I watch every one of the los videos from you , rcaddict, quadmovr, tim, and any other one that is posted here.
I remember early in fpv I had the same problem where I couldn't fly well with the camera rolling. Now it seems like pressing the record button is just part of the pre flight and 80 % of it never makes it to a video anyway.
Jul 15, 2019, 02:39 PM
Registered User
Quote:
Originally Posted by --Oz--
I have not read it yet other. The first thing it says "Impact of the Graphite Anode on Capacity Fade"

I dont think any of our batteries use graphite or graphene (yet), yep, lying marketing scam, lol. I wonder if this even applies to us?

EDIT: Scanning though the document, these are for Li-Ion 18650 cells and not Li-Po cells.
Iím not so sure about the differences in chemistry. A lipo is a lithium ion polymer battery. So essentially a li-ion cell with modified electrolyte.

Iím guessing the results will translate to some extent. The overriding message from the graphs in this article is to store your batteries between around 3.7 and 3.9v. Doesnít matter much exactly what voltage. But it should never be really high (>3.9v) m since storage will then rapidly impair the lipo.

Itís essentially what you reported from your own experience and what Iím seeing with lipos I had stored for a long time now that Iím looking more closely too.

What IR do your packs have?
Jul 15, 2019, 02:53 PM
Registered User
Quote:
Originally Posted by bexamous
I mean you feel dumb with headmount, but I just film like 10 packs so that no flight is the one where I need to do well. I just tell myself 'oh this is my warmup pack' and don't feel pressured to do well. And by the 10th I'll just tell myself 'meh one of those earlier packs was probably good enough'.

Also FWIW at least videos only about 33% of people make it 1 minute into video, 19% 2 minutes in. So really of those 10 flights you don't even need 1 in 10 to be good, you need just like 1-2 minutes in 1 of the 10 videos to be good.

And another benefit of filming 10 flights... after spending all that time filming if you get home and can't find 1-2 minute clip that looks good, you'll be so sick of the process you'll stop caring and just say 'f-it' and post what you've got to be done with it.
Yeah - I only have a shot at getting a good video if I film several packs. Usually then I think well none of this was any good but when looking at them they seem better than they felt when flying.

Of course when you think now you really have a good one you’ll invariably find that the cam has switched to time lapse mode or rotated to selfie mode and you have 3 minutes of your forehead.

How viewers drop off is really interesting to see. Major differences video to video. That small 3” 1306 one I posted recently has an average viewing time of 85% which is pretty rare. At least for me.


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