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Blitz Helicopters Avro 90 > Avro belt drive

synodontis
Veteran
Location: United Kingdom

Lolly is actually correct.

Even better think about energy and linear speed. Since energy is 1/2mv^2 and we can all agree that the energy from our engines is the same, this implies that if we reduce the weight we can get to a higher velocity quicker (i.e. more acceleration!). If I reduce the weight by one half, a car can reach 41.4% more speed than with the normal weight ((sqrt(2) - 1) x 100) using the same engine. The equation for rotating body is similar except you replace m with I (the moment of inertia) and v with w (omega, the angular velocity). We can decrease I with having the engine nearer point of rotation and/or taking off weight.

05-01-2008 06:41 PM

ErichF
Key Veteran
Location: Odessa, FL 33556 (Tampa Area)

Actually, I was inclined to agree with Lolly about that. That part made sense. It was the comment at the end that caused an instant download of his credibility.

What I disagree with, is his assetion that the belt drive on the Futura, Blitz, or the like is a noticeable detriment to available power.

05-01-2008 06:56 PM

synodontis
Veteran
Location: United Kingdom

in the avant forums they've been telling me that they just don't like the weight of the Avro, they say it's too heavy and that's why they would prefer the Aurora to 3D since it's about a pound lighter. Not an issue with me since I don't fly 3D.

05-01-2008 07:01 PM

Lolly
Heliman
Location: San Diego

"It was the comment at the end that caused an instant download of his credibility.

What I disagree with, is his assetion that the belt drive on the Futura, Blitz, or the like is a noticeable detriment to available power."

________________________________________________________________

Well, suffice to say that my 16 year old in the 10th grade loved kinematics and dynammics that was part of her physics course. She was kind enough to remind me that not everyone does 10th grade physics. So, maybe I should desist from assumptions, even though this is a technical forum. So in that respect, I apologise for any offence. That being said, I did add a smiley to indicate it's all in the fun...

I do not recall neither can I find where I "asserted" that a belt drive has a "noticable detriments to available power". If you read carefully at my previous posts, I said that having a two stage transmission (or belt drive) is LESS EFFICIENT than a single stage. ie. more bearings, masses to spin, friction on a belt etc is less efficient. Unless there is some new kind of physics and entropy going on that I am unaware of. Also, I do not recall any qualification thereof like significantly, or noticabley less efficient. Furthermore, my "assertions" may be inferred by the tone of my posts in which I state that adding any unecessary weight, or spinning gears and bearings will rob a 3D machine of power that it needs for it's power hungry style of flight. Aside from the added moments of inertia the overal heli is subjected to. I don't see anything overly dogmaticaly assertive about that.

Let's put it one more way:

3D style of flying is power intensive. That means, whatever energy is available at the engine needs to transferred to the main and tail blades as efficiently and quickly as possible. Anything in the way that syphons off energy will reduce performance. That's it..

Also, even best heli in the best hands with engine tuned to peak power and torque delivery needs management to avoid bogging down. It's always at the edge

05-01-2008 07:30 PM

Lolly
Heliman
Location: San Diego

You wanna read a bunch of assertions, claims, inuendo and hyped opinion, read the the Aurora California press release.

No doubt the Aurora is most likley a top 3D machine along with the other great machines. Time will tell how much better it is, if at all.

05-01-2008 07:46 PM

kirk
Veteran
Location: Thornton, Colorado

I fly moderate to hard 3D at 5280 feet with an Avro and the weight and belt drive does not seem to be an issue at all. I am no AJ, CY or JK but I can fly okay and would diffinatly notice if the machine lacked power. The Avro is faster cyclic wise and has more pop than the 4 standard stratus's that I have owned (not to mention it is much smoother).

BTW my Avro is 10 3/4 pounds with a VERY heavy canopy, big pipe (SB-19), and a big lipo for power. Per some of the Aurora posts I have read they are about 1/2 pound to 3/4 pound less if that. Of course these are factory pilot weights which could be off - But I do not want to argue about that.

I truly belive that any of the 90's out right now can outfly anyone, so buy what you like. I Personally like having something different than everyone else, and I also enjoy having really nice stuff...

Kirk

05-01-2008 07:54 PM

John Benario
Senior Heliman
Location: Atlanta

This has all been enjoyable reading. The physics comments are accurate, but there are some underlying assumptions that may be missed. Is a belt drive less efficient than a single stage gear? Yes, unless there is misalignment or bad parts in the gear drive and then maybe a good belt is better than a bad gear.

Is a belt tail drive less efficient than a tube drive? Yes, unless the multiple parts in the tube drive train are out of alignment and you lose power due to the increased vibration, so maybe the answer is really the belt is better. I belive this latter case applied to the Synergy with all the tail parts that did not run true.

Is the two stage reduction heavier? Absolutely. My Avro is 11.3 pounds and my Synergy was 11.0 pounds. The intermediate shaft and bearings are probably about 0.3 pounds.

Is the Avro more enjoyable to fly than the Synergy? Absolutely, because in spite of all the parts I remachined on the Synergy the Avro is the smoothest helicopter I have ever had, and it took very little effort on my part to produce that.

Yes, the Avro is heavier than other 3D machines; however, I finally realized at 44 years of age that in spite of my two lathes, mill and 30 years of experience in "fixing" kits, what I really wanted for enjoyment was a high quality kit that did not require 2 lathes, a mill and 30 years experience to build, that stayed together in flight, and was maintenance free. My Avro has been that so far.

The Stratus and Synergy are great 3D flying helicopters. I'll stick with the heavier helicopter for the reason above. Relative to price, one could speculate that the Avro is cheaper than the other kits because no additional parts are needed, and the helicopter is so smooth that future crashes from equipment failure will be avoided.

John Benario

05-01-2008 07:56 PM

Lolly
Heliman
Location: San Diego

I prefer flying my Futura SE to my EVO 90. I love the smoothness of the belt drive and the overal tracking of the Futura. That's not to say there is anything wrong with the EVO 90 but for smooth fast aerobatics, my Futura shines the way I ike it. When throwing the heli around in a smaller window, the EVO 90 outshines my Futura SE like a MAck compared with a Ferrari. However, the Futura has a very worn 60 that is additionally responsible for it's lackluster performance. In fact sometimes I prefer flying my very old Ergogas which is a heavy pig. But it's inertia gives it a more "realsitic" or larger scale style of flight. Very smooth, and relatively slow. Can see all the maneuvers vivdly and it's a pleasure to fly.

R/C heli flight enjoyment isen't ALL about 3D. Heck, being an engineer, I rebuild some of my own bearings on my 4-axis CNC Sherline mill and lathe at home.

05-01-2008 08:09 PM

RyanW
Veteran
Location: Stillwater, Oklahoma

What the heck, I will chime in here.

It is my belief that Robbe changed from the belt drive (Futura) to the single stage (Mille) transmission because the single stage was more efficient.

We MUST keep in mind that we were all flying with 60 size engines at that time. (the original Mille was a 50. It had a 60 size airframe with a 50 engine and it needed all of the help it could get).

If you recall, you really had to work on collective management back then. I recall doing funnels with my Futura and Mille. If you did things just right, you could keep it in a funnel. The first time I flew my Mille with a 90 engine, I was doing rapidly climbing funnels with no effort!

With modern power plants, the difference in efficiency is probably a moot point. We have plenty of power, but now we have a new set of problems. The vibrations that are created from some of the 90 size engines can literally break pieces of your helicopter. In my eyes, the dampening effect is a very welcome feature of the belt drive.

To address the weight issue:
It isn't the lightest helicopter out there. I can say that it is much more agile than the other 90 that I have been flying for about two years. It is maybe 6-8oz heavier than that machine, but I can't tell that at all in the air. I am still breaking in the engine, so I will have a final verdict on that later.

Weight reduction is good to a point. If I took this machine down to 8 lbs, it would flip and flop rapidly, but I am guessing that it would actually fly like crap. I think this is a good mix between being very agile and exhibit wonderful tracking tendencies.

My fingers are tired now...

-Ryan

05-01-2008 08:19 PM

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Blitz Helicopters Avro 90 > Avro belt drive

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