Armattan Oomph motor issue

[Revs]

I';m posting this up partly to find out if anyone else has the same issue and partly to warn anyone who hasn';t checked for it. I can';t be arsed typing it all out again so I';ll just post the email I sent to my supplier..

Hi, I I'm having an issue with the Oomph motors I got from you recently. I've only been out with them once, consisting of 5 <4min flights.

While checking my quad over when I got home, I noticed that one of the motors had a bad bearing. It was fine after installation, they were all smooth as silk, so this happened during the 15mins it was in the air. Ok these things happen, so I took the motor off, planning to swap the bearings. I went to unscrew the screw in the bottom of the shaft to remove the bell, when I found it was already loose. I turned it CW to see how far out it was and it seated after just over 1 turn. But then I noticed the motor had gone a little tight to turn. It had clamped up on to the bearings and the screw wasn't even fully tightened. I should say that I didn't touch these screws during install.

So I thought I ought to check the others, the bearings in these other 3 motors where still good. On two of them the screw was also loose by a turn or two and one was ok. The ok one was perfect, no end play and the screw was tight, nice and smooth. The other two started getting stiff to turn when I seated the screw like the first on did. So the screw couldn't be adequately tightened without damaging the bearings.

Obviously there's an issue here. Only one of the four motors could be, and was, actually tightened after the flights. The other 3 go stiff if the screws are even remotely tight, nothing like tight enough for safe flight. I'd like to return them for exchange/refund and so you can inspect them and confirm what I'm saying.

Please let me know how you want to proceed.

Kind regards,

Paul

Please check yours and report back.

[Elmattbo]

Oh wow that';s a big issue. Why not get in touch with quadmcfly on rcg (he does mini quad test bench) and see if he';s heard of anything? He tends to have his ear to the ground about this stuff.


Sent from my iPhone using Tapatalk

[Cheredanine]

Hi mate,
So erm, don';t know how to tell you this, but you don';t have an issue :) (or hopefully you don';t)

Let me explain...
Old school motors use a clip to hold the shaft, and thereby the bell in place, the clip fits into a recess on the shaft, that means with the clip in place the shaft and bell will only fit in one possition.
There are two issues with this
As the bearing wears it becomes loose and because the clip only fits at one point - the recess on the shaft, you can not tighten things, the bearing and motor will have vertical play and fly worse and worse without any way to fix
Secondly if the clip moves out of its grove or the bell moves a little on the shaft you will again get vertical play, you can reseat the clip but otherwise you have the same problem

Additionally the whole removing and putting back thin weak metal clips is notoriously perilous with lost or broken clips being common (we have had Saleem I think trying to find a clip for an 1806 on the forum this week


The solution to this which is increasingly popular, is to use a screw instead of the clip. The screw holds the bell and shaft in place and provides tension against the bearing.

Now here is the important bit:
The screw should not be completely tight or this will hold the shaft too tightly against the bearing, making the motor stiff
Nor should it be too lose as that will produce vertical play, it should be at the point where the motor spins correctly, issues with vertical play can be then resolved by tightening the screw until the bell and shaft spin correctly.

That is what you are describing.

The bit you are missing is that of course the screw will then of course come undone, however this is resolved by using blue threadlock on the screw. That holds it in the correct possition.  When you want to adjust the screw, you should broadly heat it with a soldering iron as this will loosen the threadlock, you can then remove the screw, apply fresh threadlock, replace it in its new, correct possition and let it dry

So what you are describing is entirely the correct behaviour, assuming you have not damaged the ithreads or motor by over tightening, take the screw out, add a little fresh threadlock, out the screw back, until the tension is correct - I would do this by tightening the screw until I can feel it is stiffening the motor, then loostening it slightly.  If I am reading right, you have one motor still functioning correctly I would compare the motors spin by hand to that when I think it is in the correct place

The other thing is obviously don';t let the motors get too hot in flight as that will weaken the threadlock

This is how all the newer motors with screws instead of clips work

[Revs]

Hiya bud, cheers for the reply Before I reply I just wanna mention I';m an engineer by trade so I';ve got plenty (21yrs) of experience with this sort of thing.  Anyway..

Regarding the threadlock, I understand that if it is designed as you say then threadlock is imperative. But if that';s the case, why wasn';t this all done in manufacture? There is no sign of threadlock on these bolts, in fact they';re quite oily. As I said, 3 were on their way out. IMO if that is the intended design it';s a poor way of doing it.

There is a far better way of doing it and it';s the way Sunnysky do/did it on theirs; make the shaft a fraction too long and use shims to eliminate the end play. You can tighten the bolt up fully and no threadlock required.

[Cheredanine]

Lol well, I can';t answer why it';s designed that way, dys, brother, I think zmx and a few others are adopting this approach, I would assume the oily stuff is what they put on to lock it, I wouldn';t swear threadlock is what is used, that is an assumption on my part but definatley over tightening will produce too much friction against the bearing resulting in what you are describing, in the case of dys they seem to have made their screws out of polystyrene which is immensely helpful to prevent overt tightening but a bit of a bu88er in how it is achieved

What props were you using (I am assuming 4s), perhaps the motors got hot, reducing any locking compound to, well the afore mentioned oily substance? There should certainly not be any lubricant on the screws

Edit thinking about it, it is possible I am wrong about the threadlock, there have been issues with over tightening on the screws but the problem may be the lubricant and the screws if they are on the way out

[Revs]

Nah I';ve just unscrewed one and wiped said oily substance on a clean rag. It';s oil. Even if I was to apply threadlock, it wouldn';t stick without degreasing both threads.

First two flights were with HQ6045. It seems I';ve got used to tri';s and I no longer like the thrust delivery with the 6045s. Last 3 flights were with DAL T5045v2';s and they were perfect. They sound so smooth, they have the punch without hammering the hardware and felt right in the corners. The Oomph motors had no problems coping with their extra weight either. I have got a set of Q5040';s to try though, which should be interesting. And yes, 4s.

[Cheredanine]

No way there should be oil on them
Picture of screw out of my oomph below, there seems to be some gunk of some sort in the thread but it doesn';t come off or leave a residue

[Revs]

Looks like they';ve altered the design. Here';s one of mine..

[attachimg=1]

You can clearly see the thread-lock on yours. Mine only has oil and hair.

[Cheredanine]

I took off washers, don';t think the design has changed mate, oil is an obvious nono, hair might help :)

[Revs]

I just popped the screw in on it';s own and there was about 1mm of float in the bell. Have you shimmed yours differently?

EDIT: Oh I see, you took the washers off for the pic.. durr. I need to go to bed..

[trebor]

They sound suspect to me "oomph" maybe they should be called woomph as they go up in flames 😜😀

[Revs]

Having looked around for a different option and not seeing anything that grabs me, I';ve decided to keep the Oomph motors. Gonna change the bad bearings and sort the shimming myself. Got some EZO bearings coming this aft. There are other motors that I like but they all seem to have the same clipless design as the Oomph';s.

I';ve asked EWM to mention this to Chris at Armattan though. If I haven';t noticed the loose screws I could have had motors flying appart in-flight.

EDIT: BTW Paul at EWM responded within an hour of sending the email, even though it was late evening. I replied just before going to bed and he replied again before I got to work this morning. Superb service I suggested he speak to Chris at Armattan about this and he said he';d already emailed him! The man is on the ball!

[Revs]

OK, Paul at EWM has had a response from Chris at Armattan. You were right Cheredanine, they';re supposed to be only tightened enough to get rid of the float in the shaft and thread-lock is used to hold the bolt in place. I don';t like this, so as I said before I';m gonna source shims so I can tighten these bolts up while still eliminating the shaft float.

Also the EZO bearing landed so i';m gonna swap them all out. The stock ones are NMB, which are fine, but EZO last longer.

[Cheredanine]

:) cool mate, let us know how it goes. All my oomohs are in a binary state - either A-ok or they got hit by a dry stone wall that shook up on me at increadible speed and destroyed them, waiting for restock :)

[Fletch]

It probably easier if you speak to Chris direct on the armattan thread ....

https://www.rcgroups.com/forums/showthread.php?t=1843444
Username is bobepine he posts very frequently and there are many other armattan designers and helpers (for want of a better description) on there

[Revs]

I';ve found a 4mm shim set on eBay for about £5 delievered! 0.1mm/0.2mm/0.3mm x10 of each..

http://www.ebay.co.uk/itm/380694995331

[iRobot]

Sounds like you';re not the only one having issues with them motors.
Not sure if you';ve seen it....
https://www.youtube.com/shared?ci=xxMnEkG20vA

[Revs]

Nah I wouldn';t say that was an issue. First, he said he hadn';t got them very tight and second it looks like he was tightening all 4 bolts CW, so motors 1 and 4 would unscrew themselves it they were at all loose.

[Cheredanine]

Nah I wouldn';t say that was an issue. First, he said he hadn';t got them very tight and second it looks like he was tightening all 4 bolts CW, so motors 1 and 4 would unscrew themselves it they were at all loose.

Agree he tightens two adjacent motors in the same direction, the threads are directional, he ain';t doing it right

[Digit]

Sorry to do a bit of hijacking, but where does one find left handed replacement bolts?
the only ones I';ve found are in China.

[iRobot]

So the oomphs are 2cw and 2ccw I didn';t realise. They look nice and seem to have stacks of power !

[Cheredanine]

Sorry to do a bit of hijacking, but where does one find left handed replacement bolts?
the only ones I';ve found are in China.

Armattan would be where I look, you get spares with the motors and they sell spare washers, assuming they sell spare bolts

[Cheredanine]

So the oomphs are 2cw and 2ccw I didn';t realise. They look nice and seem to have stacks of power !

They are essentially the same motor as t2 tornado and returner r4, alight differences in the bell, different prop mounts, slight difference in the screws revs has been having such fun with, but otherwise same oem and fairly identical performance, can not think of a motor with the same power, smoothness and efficiency, for such a low weight (which may explain why I am running them on 4 quads and planning the fifth)

[Saleem]

They are essentially the same motor as t2 tornado and returner r4, alight differences in the bell, different prop mounts, slight difference in the screws revs has been having such fun with, but otherwise same oem and fairly identical performance, can not think of a motor with the same power, smoothness and efficiency, for such a low weight (which may explain why I am running them on 4 quads and planning the fifth)

What about all the new 2305 motors thats coming out,emax white editions?

[Cheredanine]

They have been out for a few weeks, can';t comment really, haven';t been through miniquad test bench which is really the litmus test for thrust, efficiency and speed of change, although kind of assume they are good.
But my main issue with emax has always been the vibrations, wait and see

I would add the origional t-motor f series that started 2305 were not good, they were too easy to overheat, but the new pro series seem to have fixed that so question is have emax fallen into the same trap or sidestepped it?

I would also add...
We have already surpassed the max thrust that is really practical, if a prop motor combo can get about 1200g (probably lower) on the bench it is capable of providing sufficient thrust to run the quad at an angle that is beyond practical. (It';s a mechanics thing)

So the factors for motors now are:
How light are they - the lighter the bettter due to the moment of inertial

How quickly can they transition between speeds? - this is largely about having a lot of torque and (bizarrely) a limited top end, it is why, after flying zmx v3 2206 2600kv and xnova 2206 2500kv I went back to 2300kv
The same torque in a smaller range of rpm gives you faster transition between speeds, provided the top end is sufficient,

How efficient are they (grams per watt, the higher this is the longer the flight time, the less damage to the battery but more importantly the less voltage sag you will get

How smooth they run (for onvious reasons

[Revs]

One thing I will say about the Oomph motors; they';re the only motor I';ve had that are as well balanced as Sunnysky. SS aren';t always the most powerful, but they are always smooth. The Oomph';s are powerful, smooth, torquey and efficient, while also being very light. Worth putting up with a design niggle for me.

[PalmliX]

One thing I will say about the Oomph motors; they';re the only motor I';ve had that are as well balanced as Sunnysky. SS aren';t always the most powerful, but they are always smooth. The Oomph';s are powerful, smooth, torquey and efficient, while also being very light. Worth putting up with a design niggle for me.

How did the shimming and new bearings go? I';m about to make the leap myself but I';m curious to hear about your results. The bearings in a couple of my oomph';s turned to ****** after a few hard crashes, can you link to the exact bearings you got?

[Revs]

Hi mate. I haven';t shimmed the motors yet. I';m just on with installing a new FC to the Alien 6" and I was gonna do the motors after, but I';m having issues with the FC install. So far I';ve only changed the bearings on one motor and used threadlock to hold the screws in and to be fair it';s held up fine.

The bearings are EZO 684zz 4x9x4. Got them from my local bearing shop.

[Cheredanine]

The thing that really surprised me there is you have a local bearing shop?

[Revs]

The thing that really surprised me there is you have a local bearing shop?

Yeah there are 2 maybe 3 in Hudds. I support local business whenever I can.