500 Agile 5.5 another disaster

T

treff

Active Member
Thanks stoke and Slobberdog, pvolcko for the mails. Firstly the washer that goes between the bevel drive and the main drive is correct. It is the only one of that size in the kit.
Before fitting the bevel gear turns freely on top of the main gear. The problem arises when the M5 bolt is fitted through the main shaft to secure the bevel and main gear assembly.
The bolt slides through very freely but with the slightest of pressure on the nylon nut to pinch it tight then the bevel gear will not move freely so something is not right there.
The other point is when securing the bevel gear to the gear hub. I did not over tighten the screws, they are snug with loctite applied to the threads.
If I leave out the washer from between the drives everything works fine and the bevel gear spins as it should but still the bevel gear shatters so I really am at a loss.
The next point is the gain set to high. No it is set to be enough to stop tail wag.
What I have noticed and do not know what this points to is that this helicopter does not like low head speeds. I have to run at 90 percent to stop the
tail going up and down but I think this is a poor bearing in the swash. At very low speed the swash moves from side to side but I think
this is another problem again
Quick update after watching big pops build. Yes it is exactly the same problem. So I need a new shim but I think there is more going on than that. The
kit is plagued with problems and flaws which need sorting out.
Thanks to all for the interest. I have now sent pictures to Roberto the designer and also to KDS in the states and await an out come but
I am not holding my breath.
 
Last edited:
P

pvolcko

Well-Known Member
Yeah, if it is binding outside the heli then this is a problem with that shim. Either it is too thick or the diameter is such that it is getting pressed into the OWB carrier and binding against the inside wall of that carrier/hub.

Does that washer ride on top of the OWB and spin free of the hub inside diameter? Is it binding? If it doesn't bind when you try simply fitting against each other, then I'd suspect the thickness is too much. Find a thinner one if you can.

Can you run without it? Is there too much up and down play in the main gear without it?
 
T

treff

Active Member
Hi pvolcko I ran without the shim in and the bevel gear runs freely with no problem. I have already done this because I though it did not need this shim but
even then the bevel gear shattered. I have used wet and dry on it and taken it down to almost nothing and there is still some resistance. I think the belt
from the motor drive is somehow distorting the bevel gear when it turns but i'm not sure. Some thing it out of true on this helicopter. The swash is moving from
side to side at low revs so there is also something wrong there also. I may as well brought something from Hobby King. I'm bitterly disappointed.
 
T

treff

Active Member
Hi stokke. Well that is an offer to think about, thanks. I will give it a couple of days, I am waiting for the designer Roberto to get back to
me. I have sent him a few photos so we will see what happens. The Agile 5.5 flies very well when it works but there is many flaws in the
components I think that make lots of problems. I have sent for a new bearing for the swash because this one is oval and the swash rocks from
side to side. Not very good at all. Thanks for the offer I will get back to you on that soon.
 
murankar

murankar

Staff member
I am reading through this post to keep up to date so to speak. I do know if the gains are not right you will shatter those gears. That is a problem that plaques the blade 700X, its due to a mechanical gain in the tail control system. Maybe start out at the low end of the gain window and work up instead of the normal start high and work down.

As for tail bobbles. In some cases gov gain can cause this to happen. Not saying this is the case here, but has been know to be an issue. Other areas of gain to consider is the main rotor gains. A tail bob can come from head gains being to low, correct me if I am wrong on that.

Low head speeds are not for every air frame. The goblin 770 has a range around 1700 to 1950 where things go a miss. Not sure what the range is on the agile. Sometimes detailed tuning can fix some of the bobble, but not all the bobble. Other things that can help are disk loading and/or blade size. These are not sure fixes but might help.

So if the gears run smooth and gear mesh is good then don't add the spacer. The symptom here is the gear exploding and I am thinking its not mechanical. If it is mechanical then I think its in the gear ratios. The kit maybe designed with a higher torque tail drive and couple that with improper gains; exploding gears.


To conclude we have a problem statement of "Front bevel gear explodes."

The first of the 5 why's is:
Why is it exploding?
Possible answers:
Gear mesh not right
Gains not right
Gear ratio not right


Something I just thought of and can't remember if it was brought up at this moment, does this happen during tail use, during a simple hover or during hard collective changes?

With tail use are you doing hard moves on it like fast right piro to a hard left piro? This can blow a gear set if things are not right.

Something that I just caught after starting over with post one. You mentioned the bearing in the torque tube being loose. What did you use to secure it? I use green thread locker to secure mine and no issues. Anyhow if that bearing came loose in flight it could have shifted on the tube. If that happens then you will get a tail vibe at first the if thing get to far out of whack then you could get unwanted flex in the torque tube. This can cause gear meshes to become out of tolerance at the torque tube ends. Next thing you know stripped gears or worse.

Something else on page to of this thread caught my eye. When you reinstalled the torque tube bearing you said it was making a noise, correct? If so is it notchy? I am thinking now you may have got some glue in the bearing. If that happened then its possible the bearing is getting jammed during flight. It really easy to get glue in the bearing. I oil the heck out of it before securing in place. My hope is that the adhesive does not bind to metal. Then I can clean it out easier.

Now I am running out of ideas of my own.

Sent from my LG-E980 using Forum Runner
 
Last edited:
T

treff

Active Member
Thanks murankar for your detailed post. After talking to the designer of the helicopter I am still no more forwards than before.
The torque tube noise is not from the bearings I make double sure everything is smooth and free before installation and before
fitting. I do believe the problem is something to do with the setting up of the tail like you mention. It is strange that this only
happens on the Agile 5.5 and not the Agile 7.2. In scaling down I think something as gone awry. The designers suggestion was to remove
the spacer between the drives the shim the the oneway bearing block with a paper gasket. To be fair I think his English is not to good.
All in all bitterly disappointing with the outcome and the response from KDS. I am not the only owner of this helicopter who is having
problems reading on the internet and the input from KDS is to put out some wishy washy video on Youtube. That is poor beyond belief
considering the price of this kit. I will try for one more time to get this to fly with out the gear disintegrating armed with a lot more
information than I was before and we will see how it goes. Thanks again for the ideas, incidentally the gear always explode on spool
up just before lift off and when the tail is working hard to hold the hell straight. I think that is a major clue. Cheers
 
Lee

Lee

Well-Known Member
Are you running in Gov mode Treff? Sometimes this can cause too much stress on gears if the gain is too high.
 
T

treff

Active Member
No Lee, just on the throttle.n I run 90% across the board, it does not like slow head speeds. I think I have found the problem. The metal drive gear that is meshed with the plastic bevel gear is not true, it is not round
but slightly oval and also a couple of the teeth are longer than the others and I think this is what's causing the failure of the plastic bevel gear coupled with
a very aggressive setting on the tail gyro. I have ordered another. If I go on like this I will have enough spares to build a second heli lol
 
T

treff

Active Member
Last update on the Agile 5.5. I have been in touch with the designer of this helicopter and to be honest I am none the wiser.
He suggested putting a paper washer under the oneway bearing box. KDS, not a word really, very, very disappointing considering
the cost of this kit. I might just as well brought something from Hobby King. I am angry this was my first delve into what was supposed to
be top of the range RC helicopters and in my opinion after be an engineering photographer in the past this is junk dressed up in a pretty box.
I think the Agile advertising tosh says "do it differently" what they mean throw your money away in a different way. This will be my last word
I will move on in the knowledge that I will never spend my money on a KDS product again. Cheers
 
Last edited:
murankar

murankar

Staff member
Surprised to say the least. But it does make sense. I hope things improve and maybe some resolution to the problem.

Sent from my LG-E980 using Forum Runner
 
You must log in or register to reply here.
Top Bottom