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HomeAircraftHelicopterMain Discussion › Aluminium Blades - Why not?
11-03-2004 09:49 PM  13 years agoPost 21
Pliczner

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Szczecin - Poland (middle europe)

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look here
http://www.mhm-modellmotoren.de/m-blade.php

Two ultimate life rules: 1. Never say all you know.

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11-03-2004 09:57 PM  13 years agoPost 22
jerrythercpilot

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I think some people have touched upon a variety of correct assumptions here.

1) Aluminum does not have a fatigue limit. That is, ANY stress state can induce a fatigue fracture over time. Most other metals have a limit where if the stress does not exceed a specified value, the metal will never fatigue.

2) CF is a composite. The load is actually carried by the fibers and the matrix just serves to transmit the load to the fibers. A small defect in the matrix (from fabrication errors) will be "arrested" by the fiberes and prevented from growing.

3) I have not sat down to do the calculations but on the surface I assume the loads induced by an Aluminum blade on the rotor head would be much greater, do to its greater density (even if you ran hollow blades). This of course would require beaf-ier rotor head hardware.

4) Then you have stiffness. The modulus of "Good" CF structures can be 4-5 times that of Aluminum. By good, I mean structures that are laid up properly and the weaves are oriented properly for the load/application.

Jerry

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11-03-2004 10:39 PM  13 years agoPost 23
jerrythercpilot

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Newer full scle fly CF blades!!!!

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11-03-2004 10:49 PM  13 years agoPost 24
Fullagas

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Michigan

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.
Pliczner,
I don't trust repaired blades.
Nor do I. Please re-read my post. They are rarely repairable.
What kind of blades do you think the Bell 206 and Bell 212 full scale helicopters use?
And they are life-limited.

.

Flying helis since gyros had springs.

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11-03-2004 10:53 PM  13 years agoPost 25
Pliczner

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Szczecin - Poland (middle europe)

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they must know what they do producing m-blades
http://www.mhm-modellmotoren.de/m-blade/datenbl.htm

if they could write all this information. Just look. You dont have to know german to undertand.

Two ultimate life rules: 1. Never say all you know.

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11-03-2004 11:02 PM  13 years agoPost 26
Fullagas

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Michigan

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.
Just look. You dont have to know german to undertand.
Gibberish to me, dude.

Thanks, I'll plod along with blades I'm familiar with. Ones that haven't been banned (from insurance, I got it!).

Flying helis since gyros had springs.

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11-03-2004 11:05 PM  13 years agoPost 27
Peter65

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Roxby Downs, South Australia.

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Surely the company manufacturing these blades has done all the tests to determine failure/fatigue rates compaired to CF.

I wish I could read German. Are these hollow blades ? I cant imagine them being solid but hollow I see no problem.

Another method maybe aluminium honeycomb with light sheeting.

Laughing at yourself will lengthen your life. Laughing at me will shorten it...

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11-03-2004 11:34 PM  13 years agoPost 28
zoom boy

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N.E. Lincolnshire UK

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I would possibly use (at least for a test) aluminium blades, but thats my choice, its true that the strength of materials goes up relativly when the scale goes down, but they undergo more load (higher RPMs) so whether they are a better choice is really up for debate.

But the BMFA are definatly ignorant of the physical nature of aluminium, so its easier for them to just copy CAP658 and leave it at that, and they know that the majority of ppl will not say they are wrong, because the majority of ppl havent had formal training in this field, and they have scared the modeling community into doing as the BMFA tells them so they have started getting a bit big for their boots, hence why I will be changing over to another organisation at the end of the year

I just had to post this, if you think alu heads are funny, just think about the old metal paddles on the Concept 30 DX, thats just so f**ked up

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11-03-2004 11:49 PM  13 years agoPost 29
Fullagas

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Michigan

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.
if you think alu heads are funny, just think about the old metal paddles on the Concept 30 DX
LOL

Maybe it's time for the olde foamie blades to make a comeback!

.

Flying helis since gyros had springs.

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11-04-2004 02:20 AM  13 years agoPost 30
Peter65

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Roxby Downs, South Australia.

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These are extruded aluminium. ie they are hollow. I can't see why they should be band when CF over wood would be much stronger

Can I buy these blades? I would like to see what they are like.

Laughing at yourself will lengthen your life. Laughing at me will shorten it...

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11-04-2004 02:32 AM  13 years agoPost 31
Inspector Fuzz

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NLA

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Metal blades??
What will the Polish think of next???
JEFF

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11-04-2004 05:15 AM  13 years agoPost 32
Alistair

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no where land

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a big reason is because the allow blades don't explode on contact with objects... the carbon ones do, which kills their energy... allow ones could eject themselvs from the heli in the event of a CFIT bounce of something (or go through you) and destroy when they are going to hit (the person behind you)...

they make some neat noises though...

squigle

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11-04-2004 05:22 AM  13 years agoPost 33
Peter65

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Roxby Downs, South Australia.

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Question.. Has anyone seen this, has anyone on here got any info to back up their ideas on how these blades behave?

I have been hit in the shin by my CF blades while at low speed when running down. It still hurt like hell and I think would have felt no different to aluminium ones.

All comments on here are pure speculation unless you have seen/used these blades. Does no one think that M Blades would not test these qualities before putting something dangerous on the market?

A lot of ignorance here I think

I'd like to give then a whirl

Laughing at yourself will lengthen your life. Laughing at me will shorten it...

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11-04-2004 07:00 AM  13 years agoPost 34
Alistair

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no where land

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i believe some people are using them in germany... ask 'bout them there if you want comments with no "ignorance"

squigle

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11-04-2004 07:31 AM  13 years agoPost 35
Adam Landefeld

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Lehi, UT, USA

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Alloy blades are kind of cool, and they serve a very real purpose in full scale aviation. In a model though I have my doubts and the mostly stem from one main observation. Remember that full scales are not expected to run the head speeds we run and are not expecting to "encounter" terra firma with their blade type thingees.

Imagine, if you will, a model helicopter flying some nice 3D with a decent set of CF blades. Pilot, who shall remain nameless plows the machine into the ground whereupon the throttle linkage pops off and the machine flops around on the ground as the blades are reduced to nubs and so are a lot of parts. Dangerous to get to too close to, yes?

Now think of the same exact wreck with a set of alloy blades. They will not be reduced to nubs any time soon, and they will destroy the helicopter and everything around it until the motor gives up or the main shaft shears.

I like a blade that, like a crumple zone on a well designed car, gives when it should. I have seen many machines doing the funky chicken all over the ground that would have been terrifying had these been equipped with a set of alloy blades.

That is just my two cents worth, although it's probably worth much less

-ADam

Futaba Factory Team
Team FlightPower
Thunder Tiger

https://www.facebook.com/UtahHeli

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11-04-2004 07:45 AM  13 years agoPost 36
Alistair

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no where land

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lol.... that is essentially exactly what i said... just reiterated....

so really, it's not EXACTLY what i said, but it's the same thing...

i want a blade that knows when to die as well. i'd rather not be killed by my machine when making a silly mistake.

squigle

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11-04-2004 07:57 AM  13 years agoPost 37
IYKIST

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London united kingdom

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If you have had 3 crashes and the blades are still fine then it says it all, it would be like flying a chainsaw or should the rotorhead come off God
help the people around ( lethal weapon)

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11-04-2004 08:54 AM  13 years agoPost 38
brian chan

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Hong Kong

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People's safety should be the prime concern.
Real Heli's rotor runs at about 300 rpm. For model, it runs at 1,800 rpm. Real heli pilot will fly in a normal way but not 3D. Assuming the AL blades can withstand the stress and bending from 3D flying, I believe the stress will transmit to the blades grips, especially to the two blots locking the AL blades , and its bearings. With a suddenly broken blot, the AL blades will become an AL missile.

Can rotating AL blades at a high speed work like a circular disc to collect radio interference or to block radio signal ?

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11-04-2004 08:56 AM  13 years agoPost 39
Pliczner

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Szczecin - Poland (middle europe)

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3 craches - but nothing really bad, always on the skids... frame and servos are ok

Two ultimate life rules: 1. Never say all you know.

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11-04-2004 11:44 AM  13 years agoPost 40
Peter65

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Roxby Downs, South Australia.

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Head comes off at speed it's not going to matter whether they are aluminium blades, CF or wood. I am outa there. A blade moving at 200mph is going to kill/mame regardless of what it's made of.

Why is no one complaining about the 40% A/C these things run huge CF propellors which devastate bone and flesh as demonstrated recently.

Laughing at yourself will lengthen your life. Laughing at me will shorten it...

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