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Old 01-03-2017, 12:40 PM   #1 (permalink)
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Default New 550sx Vibration Problem

So I pickup a new 550sx V2, Mod 1 gearing (16t pinion), new Scorpion 4025, 25mm boom. I've put about 25 flight on it.

Now I have a vibration problem, I can see it in the skids and tail fin. Its very noticeable around the 2100/2150 rpm mark, as I increase rpm its goes away.

I completely tore the heli apart and checked everything. No smoking guns, I noticed when spooled up the tail slider requires some effort to move. But the tail holds good with the MKS tail servo. When moved by hand the slider is silky smooth. I checked the blades and the main blades were .42g off. I balanced them and then tried a set of Edge main blades but still no luck. I've tried to square the tail box as much as i can, I've with in .5mm square.

I've read every vibration thread and it seams a lot of problems stem from the tail. Either not being square or changing the grips to quick uk tail grips might help.

Do you think changing to the spedix tail would cure the issue or the quick uk tail grips or should I be looking elsewhere?
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Old 01-03-2017, 02:34 PM   #2 (permalink)
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I had a slight tail wag when I built mine new. I ended up trying the speedix tail case and the quick uk tail grips. The quick uk tail grips seemed to fix my slow tail wag problem. The flanged bearing in the tail went right away so I put the speedix tail case on.
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Old 01-03-2017, 02:35 PM   #3 (permalink)
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Quote:
I noticed when spooled up the tail slider requires some effort to move.
I could be wrong but is the effort because they are trying to self centre? I am assuming you have the rod disconnected from the servo?

It can be frustrating with the Logo despite its cost and pedigree. The tail grips and hub usually need some work. There can be flashing in the grip stopping the bearings from seating properly. The hub can be a little over size and so the bearing don't go on as easy as they should. When Mikado brought out a hardened tail output shaft it was a fraction over-sized and either you polish it down or file out the slider. I don't know if that has been fixed. I found the details on the vstabi website.

With the split tail case it can be quite difficult to get it squared up properly.

I found the edge tail blades are not very good. Although they appear balanced I dynamically balanced them using trial and error and the v-bar vibration analyser until I got the lowest reading. Once I switched them out to rotortechs I didn't have to faff around.

If you have a vibration analyser as part of your fbl controller I would strip the model and spool it up on the bench adding parts until you find which causes the vibration.
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Old 01-03-2017, 02:38 PM   #4 (permalink)
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Could the vibration be comming from the head ?

I just switched from the old style head to the new style and now I am getting a wobble or vibration. I have only just tried to hover to test it.

I tore the head apart and I am going to try a cobo of 7 x 4.5 med damper, 7 X 5 med damper, 7 x 5 hard damper to see if it fixes my problem.
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Old 01-03-2017, 02:41 PM   #5 (permalink)
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A wobble is not the same as a vibration. With a 2100 head speed I would not be expecting to see a wobble.

What head speed are you running?
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Old 01-03-2017, 03:22 PM   #6 (permalink)
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Yes I had the tail rod disconnected when i spooled it up to check the tail, I'm pretty sure what I felt was it trying to 'self center'

Unfortunately i don't have vibration logging on my fbl unit (iKon)

I 'thought' it was a head problem actually, just judging by the shake in the skids. But I've been through the head twice and everything seams perfect. Again the I only see the shake in the skids and tail fin.

Thanks in advance for the help
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Old 01-03-2017, 03:27 PM   #7 (permalink)
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start with the basics. vbar log/ vib analyzer freq?

I will always remove mains and tail control rod- spool up carefully - even on the garage floor and see how much vibe there is. Then feel the boom and dynamically balance the tail blades. VBAR analyzer can help but you can feel it when its right and wrong. try all rpms you use.

also be sure you are not too tight and have EVEN main blade tension.
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Old 01-03-2017, 03:43 PM   #8 (permalink)
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Quote:
Originally Posted by Jasons9 View Post
I 'thought' it was a head problem actually, just judging by the shake in the skids. But I've been through the head twice and everything seams perfect. Again the I only see the shake in the skids and tail fin.
Have you tried to remove the whole head from the main shaft and spin the heli on the table? Please also remove tail blades for safety. My guess would be slightly bent main shaft. You will be able to see if it's bent when looking from the top. Vibrations will be also possible to notice when touching the tail boom. Mikado's main shafts are very soft and can bend very easily from the slightest impact. I had my heli fall down from the shelf once (not powered, no battery inside) and shaft got bent pretty much.
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Old 01-03-2017, 07:10 PM   #9 (permalink)
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it sounds like you washer at the pulley not even.
the pulley shud be sit down touching the belt.
i did once. by add washer at the main shaft so the tail belt is center at the pulley.. thats creating the vibration becos it supose to sit on the pulley not center.

also it might be you tigthen too much on the tail. do look at manual. all the tail hv to be 27mm.. 26mm wil make the tail pinch too much .

i been using stock tail all the way.. i been in your situation trying to get the speedix for a quick escape to solve this.. but i slowly study the issue and all is good for me with stock setup more than 1000 flights.

1. make sure belt sits on pulley ( at the main gear there) dont try center it
2. make sure tail box is 27mm according to manual. i did over tigthen abit last time.. it was pressed in.. so i added small washer 4pcs at the screw area get back 27mm tail
3. its sensitive esspecially at the bearing thats hold the belt there.. must be 27mm
4. do check your tail hub make sure thrust bearing is greased and no plays .

i guess it shud be fine after all these checks..the logos heli with me for 5 years.. using stock setup..so far its been serving me do well..happy with it.
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Old 01-03-2017, 08:54 PM   #10 (permalink)
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As a matter of interest you do have some options to you on the ikon with vibration analysis. Update to latest firmware with rescue and you will see diagnostics tab. On the bench you can spool up with blades removed and at least look at the graphs in real time.
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Old 01-03-2017, 09:59 PM   #11 (permalink)
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Default Vibration Solution Suggestions

I have had issues with the belt not meshing properly with the teeth in the tail drive and causing vibrations If the belt gets stretched a bit, the teeth are too far apart for the tail gear. The belt design is very poor, the teeth are too far apart, creating an easy mismatch when the belt stretches too much.

What I did was buy a new tail gear and a new belt, then I used a liquid lubricant from AMainHobbies.com especially designed for plastic gears and belts. I put enough of the lubricant to coat the gears and the teeth on the belt. The belt teeth now mesh perfectly with the tail gear.

If you still have problems, what I would do is to buy the Speedix tail gear and the Speedix main belt drive gear. They are all aluminum and many Logo owners use them to tame down to belt mismatch issues (which also causes the vibrations). You can order them from BuddyRC.com

Also, you have to be very carefully in torquing down the tail belt tensioner as well as all the rear tail bolts. You need to maintain a 27mm distance.

If you need additional help you can get it from the engineers at the MikadoUSA.com website. They are very helpful.

All the best,

Ken
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Old 01-04-2017, 06:35 AM   #12 (permalink)
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Quote:
start with the basics. vbar log/ vib analyzer freq?
Not helpful when the OP is running ikon.

Quote:
I will always remove mains and tail control rod- spool up carefully - even on the garage floor and see how much vibe there is. Then feel the boom and dynamically balance the tail blades.
That was my suggestion but to go further and remove all of the rotating parts and rebuild the model testing at each stage. We are spoilt with v-bar analyser. The OP has ikon so I don't know what he has to do but he does have options.

The standard tail end of a Logo is difficult to get right and requires special consideration. As above, once done it will go for years of trouble free flying. My Logo 500 with its plastic tail box is 7 years old albeit with new bearings.
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Old 01-04-2017, 09:22 AM   #13 (permalink)
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Thanks for the help everyone, its seams this model can be a bit finicky.

I have spooled it up with no head and the main shaft is straight, I also checked the main shaft on my stone counter and its for sure true. I felt basically zero vibration with no head and tail blades on.

I'll post a pic of how the belt is sitting on the pulley, it sits very low but does not touch the bottom lip of the pulley. I hope the belt is not stretched it only has about 25 flights on it. Though they were colder flights, I'm running a loosish belt tension with the 25mm boom, it does not slap the inside of the boom.

When I was building my kit I noticed that the right side of the tail (orange fiberglass piece) was not flat. I attempted to straighten it a bit but in the end I just used the bolts to get it to 27mm. I'll post some pics tonight it will make this clear.
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Old 01-04-2017, 09:42 AM   #14 (permalink)
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One thing I noticed about getting the tail box square was rotating one direction slowly moves the belt to one side of the tail pulley and when you spin it the opposite way it will go to the other side of the tail pulley. At least that's what I guess is right.
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Old 01-04-2017, 08:28 PM   #15 (permalink)
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Have you checked to make sure the belt does not have an extra twist in it? I had a set of tail blades once that were so far out of balance they nearly caused a crash. It might be worth checking
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Old 01-05-2017, 02:21 PM   #16 (permalink)
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Pics, let me know if you see anything off.

The belt is definitely not twisted, its super smooth when turned by hand.
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Old 01-05-2017, 04:15 PM   #17 (permalink)
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Quote: Now I have a vibration problem, I can see it in the skids and tail fin. Its very noticeable around the 2100/2150 rpm mark, as I increase rpm its goes away.

If you lower the rpm what happens ? Does the vibration go away ?

Quote: I have spooled it up with no head and the main shaft is straight, I also checked the main shaft on my stone counter and its for sure true. I felt basically zero vibration with no head and tail blades on.

Sounds like it is head related.

What dampers do tyou have in the head ?
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Old 01-06-2017, 12:20 AM   #18 (permalink)
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Dampers are the factory ones, larger damper (7x5) on the outside and two smaller ones 7x4.5 on the inside. Maybe ill pull the head appart one more time and check it out.

I've maybe lowered it to about 2050 and it kept getting worse.. at 2250/2300 its pertty much gone..
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Old 01-06-2017, 02:31 AM   #19 (permalink)
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i nv know there are diff size of damper on the head.. for me i stuff all in make sure its fully goes in..tail fin vibs ( are you sure both tail screws are same lenght?)

maybe redo the whole tail hub and check there
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Old 01-06-2017, 04:28 AM   #20 (permalink)
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How have you set the mesh of the pinion to main gear? Did you find the high spot?
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