RunRyder - A design flaw in the IonX

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e-Miniature Aircraft Furion - Razor - Ion-X > A design flaw in the IonX

ABoyNamedSue
Heliman
Location: Gainesville, FL

Has anyone else noticed that the main shaft of the IonX is supported on only one side of the main gear? Does anyone else see the problem in this design, or am I missing something?
By shortening the main shaft and eliminating the bearing support beneath the main gear, the weight of the heli will apply more torque and stress to the last bearing, i.e. the one right above the main gear. For a heli that weighs similar to a .91 and is intended for yanking, banking, and flipping like a .91, that's a lot of stress.
It seems to me that it would have been much wiser for MA to extend the main shaft a half inch and put another bearing to support it underneath the main gear, as they've been doing with their other Furys. The weight increase would have been minimal.
Anyone else agree, or have a good explanation as to why MA felt it was OK to design it the way they did?

05-22-2004 Over year old.

scott s.
Veteran
Location: Orange, Ca.

Jason doesn`t seem to have a problem with it and he flys it pretty hard.

05-22-2004 Over year old.

chriss
Senior Heliman
Location: Sunny Florida

Putting the bearing under the main gear is a relatively new thing. Currently only two of our models have this feature. There is more to it than just torque. With the big nitro engines, you have to design for a lot of vibrational stress, LOTS of vibrational stress. We also have to beef up everything else to use those engines.

Now with electric, things are different. There is a lot of torque, but almost zero vibration, so things don't have a tendency to rattle loose. We are able to remove a lot of the "stress members" that you see on the liquid powered machines. In fact, you kinda have to in order to reduce weight and get the all important horsepower to weight ratio up.

Chris

05-22-2004 Over year old.

ABoyNamedSue
Heliman
Location: Gainesville, FL

What I'm talking about is.......

The torque and stresses against the lower-most bearing (i.e. right above the main gear) are not so much a function of vibration or motor torque as they are a function of the weight of the helicopter being pulled in different directions by the main shaft as the heli yanks and banks.

I realize this is an oversimplication, but it will describe my point a little better:

Imagine grabbing a Tempest by the rotor head with your left hand, and an Ion-X by the rotor head in your right hand. Then imagine violently jerking helis back and forth and back and forth, for a few thousand cycles. I'm guessing that the bearing of the Ion-X close to the main gear will show more signs of wear/damage. Why? Because a greater amount of the 10-lbs of the Ion-X is being supported by that last bearing that the analagous bearing in the Tempest. The bearing below the main gear supports the heli closer to its center of gravity (from top to bottom).....if that makes any sense.

05-23-2004 Over year old.

ABoyNamedSue
Heliman
Location: Gainesville, FL

There's another thing to consider...

In addition to the torque on the shaft and bearing, you must also consider the fact that the majority of the IonX's weight is going to be supported by the top 1/3 of the carbon fiber frame. Everything below that is completely unattached and thus unsupported by the main shaft.

Maybe what I'm talking about here is purely academic, and in reality, maybe the bearing is strong enough, maybe the housing for the bearing is strong enough to not deform over time and allow the bearing to move rather than be seated firmly, and maybe the top 1/3 of the carbon fiber frame is sufficiently stiff to not allow any flex beyond the last bearing. Maybe. I'm sure MA tested the heli thoroughly, but then again, design errors are made even by the most capable engineers!

My point is that an extra half inch on the main shaft plus one extra bearing to support the frame at the end of shaft (the way you find it on the Tempest models) would have been highly appropriate for a heli that weighs AND performs just like a 90-sized glow. The weight penalty would have been minimal, especially when one considers that batteries are getting lighter and able to hold more juice.

05-23-2004 Over year old.

scott s.
Veteran
Location: Orange, Ca.

Hey Sue

Your job isn`t being an Engineer by chance would it?

05-24-2004 Over year old.

ABoyNamedSue
Heliman
Location: Gainesville, FL

No. I'm just using common sense.

no message.

05-24-2004 Over year old.

Greg McFadden
Key Veteran
Location: Spokane Valley, WA

unfortunatly your common sence analysis is horriffically flawed. you approaced the analysis from a "fix the load at the top bearing lets throw all the extra load on the bottom bearing". This is incorrect. What will happen is that there will be more load on both the top and the bottom bearings than a perfectly set up 3 bearing block system (an imperfectly set up system will either unload one of the bearing blocks or load them all incorrectly by trying to bend the main mast). How the load is distributed will be a function of how the frames, main mast, everything else deforms under load and where the CG's are of various components and assemblies (along with mass of course). This is NOT something that can be easily figured out (you can NOT figure this out at all without a program such as ANSYS and a person who knows how to use it properly) or even "common senced" out. That field is incredebly difficult to do well in (every bit as difficult as fluids and heat transfer in my opinion) .

but back to the "no third bearing block"
the older X-cell SE with an 80 flies fine without a third bearing block. It would be nice to have one but it is not necessary. As others have said too, what the bearing blocks and everything else sees is a VERY high vibration environment as well as a pulsing power from the engine. the engine output torque is NOT a constant smooth curve, it is pulse (detonation and expansion) and then coast (ejection of exhaust and re-entry of fuel and air) that repeats. you don't get ANY power out of the engine durring the coast phase, it all comes from the pulse phase. this is where our heavyest big block vibrations come from, and all these things are transmitted to the bearings, forcing amongst other things beefier sideframes, bearings, bearing blocks, etc.

an electric motor on the other hand is buttery smooth, with a fairly constant torque applied (no real pulsing on a well designed motor) which means that we don't have to overdesign the heli as much. Without the high vibration environment one can design for flight loads much easier.

The silence often, of pure innocence persuades, when speaking fails

05-24-2004 Over year old.

ABoyNamedSue
Heliman
Location: Gainesville, FL

You are assuming that the main shaft remains rigid.

By saying that all three bearings will experience increased forces, you are assuming that the main shaft remains absolutely rigid throughout flight, and doesn't flex even one micron. That would be a virtual impossibility, and an impossibility I simply assumed to be the case when I voiced my critique of the Ion's design. On the other hand, I also stated that my critique might be purely academic. I guess I had the wrong idea when I thought I could strike-up an interesting and friendly discussion over a remarkable toy.

Glenn

P.S. I have my IonX on order.

05-24-2004 Over year old.

Greg McFadden
Key Veteran
Location: Spokane Valley, WA

my bad, I apologise, from my end it appeared (since you have no profile and only posted here) that you were simply a slightly more sophisticated troll than the average, so I decided to play.

What I would really be interested in would be someone putting bearings with load sensors in to see what these things actualy see in flight (not a cheap proposition). The hard thing about not assuming rigid body is that I don't have access and the training to use a numeric sim (much less the part files to make the model) to model this. Add to that that the complexity of even a simple thing such as the ION would take a lot of computer time to completely analize. I do agree that I generally would like to see a third bearing block but I still think that it is probably not needed in this case (but if you have to replace bearings more often that will prove me wrong)

The silence often, of pure innocence persuades, when speaking fails

05-24-2004 Over year old.

ABoyNamedSue
Heliman
Location: Gainesville, FL

It would be interesting to see!

Don't give it another thought! I should have pointed out that I am somewhat of a worry-wart, and believe that things should be over-built. In the case of the Ion, it just seems that it was unnecessarily slightly under-built in that one area. I can see how an electric helicopter needs to be as light as possible, especially when maximum performance is the goal. I just think that the weight penalty of a third bearing block beneath the main gear would have been minimal and such an easy thing to include in the design. But then again, I don't have access to the knowledge and details MA's engineers do, so I could definitely be way off base here!! You are quite right, however, time will tell! It'd be interesting, however, to see the results of load-sensing bearings. I'm guessing that the lower-most bearing would end up taking a bit more beating than the top two. Rest assured, I'll be too busy flying my Ion to waste time testing its frame! LOL

05-24-2004 Over year old.

Qrrambero
Veteran
Location: San Francisco / Bay Area

Just one word. "Money". Or like I tell friends. Miniature is the Harley Davidson in Helicopters. You buy it and options and upgrades come later.
I do not have anything agains that. It is a great marketing and we are the fools that pay. And I am one of them.
I remember when I had my X-Cell custom and the SE came out. I got every gold part available for for my custon
Ae.
PS. Waiting for My Ion.

05-24-2004 Over year old.

RotorX
Key Veteran
Location: London

Why dont you just send MA the question, instead of all this speculation, and get the answers

05-26-2004 Over year old.

chriss
Senior Heliman
Location: Sunny Florida

"Why dont you just send MA the question, instead of all this speculation, and get the answers"

He did...we listened and answered.

Chris

05-26-2004 Over year old.

ABoyNamedSue
Heliman
Location: Gainesville, FL

MA gave a very logically sound response. And one other thing:

Chris, it occurred to me that I didn't read your post carefully enough to see that you were actually an MA employee. Sorry about that!
Anyhoo, the response I got from Tim was excellent. I did have one other question though: if there was enough room to add a third bearing block, would you have added it? Or do you think it would have been nothing more than a redundant support?

05-27-2004 Over year old.

chriss
Senior Heliman
Location: Sunny Florida

On this model, I do not think the third bearing block would add a lot of benefit. It would of course make the system more rigid, to the point of overkill. And, no doubt, the addition would have cost at least an ounce or two. Believe it or not, we scraped weight from everywhere. In the end it was down to grams...

Chris

05-27-2004 Over year old.

sbalder
Senior Heliman
Location: Westland, Michigan

I borrowed a vibration analyzer from work last month and hooked it up to one of my helicopters. This device measures the force of the top 4 vibrations on a machine and is used in the automotive industry to diagnose vehicle vibration. I had visions of fine-tuning rotor balance and shaft alignment with a precision that is lacking today. What I found instead was that the engine vibration overpowers everything else in the machine and puts an incredible fatigue on every part of the machine. With the intensities of the vibrations I am amazed that our electronics dont simply tear themselves apart.

A smooth electric motor will put out so much less stress and vibration that our machines should be able to have lighter construction. I welcome the Ion and look forward to the day when you can buy an electric 30-size machine with same cost, durability, and performance of a glow ship.

-Steven Balder

05-27-2004 Over year old.

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e-Miniature Aircraft Furion - Razor - Ion-X > A design flaw in the IonX

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