Bent gimbal...

RichWest · Oct 10, 2017

USMC86 said:
I’m sure an half dozen gimbals will last you Rich- There will come a time when we will have to cross load to keep all of our drones in the air - swapping parts and services to keep everyone flying. Just the fact that you’ve already started attempting to repair gimbals- when you perfect it, you will be in crazy demand. I continue to guard my gimbals like gold-

Nah, I'm just piddling. There's no money in this, besides who wants to work when this is just for fun... Honestly I'll be surprised if it works, but then nothing ventured nothing gained.

I spent the last 2-1/2 hours stripping the arm off and then "trying" to straighten the arm the best I could. Just now got the arm back on. No question, the gimbal is well made and you need an arsenal of tools to make this effort. Was able to use a flat surface as a reference and then had a rod placed through the hole for the yaw motor shaft as another. I likely made it worse from my original effort with just the tool. Having the arm separated from the gimbal is the only way to approach this effort.

Removing the ribbon cables was a time sucker, had no clue how they released from the connectors. The one's with gray front pulls straight like a wedge and on the wider connector's black gate flips up front to center. Cutting away the adhesive was slow, carpenter's blade worked well.

And no pictures, sorry. One thing lead to another and I wasn't looking back. Hopefully will get this in the air by the weekend. Worst case, this will be a gimbal of last resort...

USMC86 · Oct 11, 2017

Hey Rich-
Well clearly, you have more experience with the 3dr gimbal, it’s assembly and how it functions than most of us. Can you give us some suggestions on issues you have discovered, ways to prevent those issues and any kind of maintenance procedures we should be performing?
I already am aware that placing my drone in the bed of the truck with cases of ammo or any other heavy items are not beneficial to either your Solo or the gimbal!
Thanks Rich!!
I have seen threads where folks talk about screws “ backing out “ and rubbing against the interior components.? Thanks again.

RichWest · Oct 11, 2017

USMC86 said:
Hey Rich-
Well clearly, you have more experience with the 3dr gimbal, it’s assembly and how it functions than most of us. Can you give us some suggestions on issues you have discovered, ways to prevent those issues and any kind of maintenance procedures we should be performing?
I already am aware that placing my drone in the bed of the truck with cases of ammo or any other heavy items are not beneficial to either your Solo or the gimbal!
Thanks Rich!!
I have seen threads where folks talk about screws “ backing out “ and rubbing against the interior components.? Thanks again.

I got nothing, other than replacing the dampeners/isolator balls after a good crash.... Again the Solo gimbal is a fairly stout and a well designed contraption.

Technically speaking I'm just a mechanic, if it's broke I'll attempt to fix....sometimes I get lucky. I am by no means a know-it-all, I'm just willing to share my experiences with the community of users. If you are reading of my adventures to repair or to improve on a component, it is simply my means of keeping notes and as some form of entertainment to like minded people. I share those notes to offer some guidance for others to attempt the same. A pay it forward type of thing for me...

So try something, If you get stuck, myself or others are happy to share our thoughts. Just make sure you pay it forward....

USMC86 · Oct 11, 2017

A lot of guys pay it forward on this forum- That tool you made- looks top notch. Was hoping you were going to solve the gimbal crisis. You still may.

RichWest · Oct 11, 2017

Just installed the circuit board assy and re-applied the ribbon cables. Need a better set of eyes and a third hand.... Using e6000 adhesive to lock it all down.

USMC86 said:
A lot of guys pay it forward on this forum- That tool you made- looks top notch. Was hoping you were going to solve the gimbal crisis. You still may.

Couldn't agree more, plenty of smart people have left a lot of valuable info for others to glean.

The 'tool' on the other hand was a hack job, would NOT use it now knowing what I've learned in this round of efforts. I'll know by this weekend if the effort was a success or just a pipe dream.... In either case I learned a lot. I'm glad I have a day job.

RichWest · Oct 11, 2017

USMC86 said:
A lot of guys pay it forward on this forum- That tool you made- looks top notch. Was hoping you were going to solve the gimbal crisis. You still may.

Wow, out of site out of mind... @cyberblitze did a great post on breaking down a gimbal. I had forgotten about it... Thanks @tinker bot for bringing it back...!

https://3drpilots.com/threads/gimbal-teardown-sort-of-and-now-with-some-rebuild.7157/

RichWest · Oct 12, 2017

Test flew the gimbal just now, wow it worked...brief video uploading now...will post link in about an hour or so.

Horizon is level, no legs in shot, full FPV....wow I can't believe it, it actually worked.

USMC86 · Oct 12, 2017

See Rich- you are the subject matter expert of the 3DR gimbal!! You have twice as many successful repairs than all of us! Congrats! Your diligence paid off.

RichWest · Oct 12, 2017

LOL...err...no. Kind thoughts, thank you..

Just a two minute flight to check everything out, little maneuvering to verify compensation and then check the horizon for level. Better than expected, results based on aggressive flying, the camera tilt thing.

Reflecting back I think the guide rod was the key in bringing everything back into alignment. Also having a couple pair of Knipex Plier Wrenches to use made the task of reforming much more controllable, just an amazing tool for this kind of work.

Added insight: To remove the yaw arm screw, you need to loosen a grub screw in the yaw arm shaft. It can be accessed through an opening at the base of the arm that mates to the yaw shaft. It requires a ~~0.050"~~ 1.3mm allen wrench...

Straight from the camera, so audio warning...

edit: I can't spell...

sirminder · Apr 16, 2019

Old post, but never the less good info! Thanks Rich!

I have a bent yaw arm on a Gimbal that resulted from an 8ft crash. The Solo landed on its back, so the Gimbal was not totally wrecked. The Gimbal turns on fine, video is ok, paddle control is also ok and is able to keep its balance. However, the only problem is that it is pointing to the right quite a bit...I am guesing ~10° (picture to follow).

Now, I am considering the idea of taking it apart, and trying to bend the yaw arm back. But before I get myself in too deep, I'd like to know if anyone was able to save the picutes Cyberblitz put in his Gimbal Teardown post. It appears they are no longer available and he/she is no longer active in these forums.

Also Rich, could you please explain a bit more on your "guide rod" trick and what other tools besides the Knipex Plier Wrenches you used?

Honestly, before I read this thread, I was thinking of approaching the job similar to how you did....coming up with a makeshift vise and bend the arm back. Now, I realize that its better to take it all apart...?

Thanks in advance

RichWest · Apr 16, 2019

I did post up a set of photos of the disassembly, check in the GP/GP Gimbal section of the forum.

This thread is still valid, but yeah it's old.... I have improved the process, but that is because I've processed about 10 gimbals now. Disconnecting the ribbons is the most difficult process, take it slow.

The guide rod is a reference for skew and straightness. By placing into the yaw mounting hole you can measure the front to back difference, so you are insuring the yaw arm is a perpendicular "L". The skew is to check for twist, most common, as I have found bent gimbals are typically a compounding bend. You should expect a centerline alignment if the skew is correct.

No doubt disassembling the arm is the best method to straighten. My approach is intuitive if you are familiar with mechanical fixin's, but meant as a guide to what worked for me and the tools i have handy. The arm's material appear to be stiff rather than springie, so little need to over bend to set. A flat surface is an integral tool, again as a reference to what is straight/flat or not.

Without jigs and such, straightening the arm is hit or miss. I usually have to repeat the assembling to correct minor offsets as I straighten, I had no exact reference to what is factory correct... If the electronics are sound a slight bent arm will show in flight. However I do most processing in my shop and then a final confirmation under flight conditions.

Also don't overlook the Roll Arm. It should also appear perpendicular to the yaw arm and basically be level to the ground when installed on Solo.

Are you located in the USA?

sirminder · Apr 17, 2019

Thanks for explaining the use of the Guide Rod. It should definitely make it easier to see where the arm is bent, how much it is bent and how well it was able to get re-aligned (hopefully). Looks like a Rod with about 5mm should do the trick. However, it is the ribbon cables I am mostly dreading dealing with. I have a few dental picks and other small tool kits I picked up along the way. Hopefully, those along with some hefty pliers similar to your Knipex, can help me with the process.

Here are some pictures as promised:

Gimbal-A

This is the one I have been talking about. It is a bit hard to see how far out the Yaw arm is bent when looking at the Gimbal from the back. Looking at the Gimbal from the front, one can see the degree of the damage to the Yaw arm. I haven't measured exactly how far it is out.

Gimbal-B

This next Gimbal seems OK visually apart from a small dent on the Roll arm. However, maybe its just me, but the Yaw arm on this one looks a bit off the side. The previous owner had a crash and could not get it to stop dancing. Like Gimbal-A, this one powers up fine, Video is Ok, Paddle control also works, but it just will not stop going berzerk. Perhaps the IMU is toast on this one. I tried resetting the parameters on Mission Planner, but that did not help.

I am starting to think that maybe I can change out the Yaw arm from Gimbal-B to Gimbal-A. The yaw arm on B does not "seem" that bad. I will only find out when I take it apart.

Or, swap out the board from Gimbal-A to Gimbal-B. [need to verify]

Either way, I gotta have at least one them working again.

I will go throw my tools and hopefully start the process this weekend.

Any other advice, please keep it coming.

Thanks!

sirminder · Apr 17, 2019

Just found the thread you mentioned....wow! You made my day/week!

RichWest · Apr 17, 2019

I agree swapping arms is a good idea. I'd start with the spastic gimbal for the first dissection. It won't hurt as much if you muck it up.

As to the dental pick tool I use, I beveled the leading edge to allow for cutting on the push stroke. As well I rounded out the tip to make it less pointed. It's all more like scraping than cutting. The dark gray adhesive securing the ribbons holds well, but will release as it is worked into.

The tool works well considering you are working in a confined space. Releasing the isolator balls will allow more exposure to the connectors. Your goal at this point is to release the ribbons without destroying, detailing can be done after everything is separated.

Keep in mind the adhesive was applied without concern for removal. So it can be slopped ON or IN the connector preventing the latches from releasing. You just need to work slow and not force the efforts.

Once you release the ribbons you can now start the gimbal disassembly. Do not forget about the grub screw on the end of the Yaw shaft. And be sure to mark the Yaw motor's alignment.

Releasing the Yaw arm from the Roll motor assembly is a chore. Remove the plastic cover and then release the ribbon from the Roll circuit board first. The bent philips screw driver is what I use for these screws. Also you have two different screws securing the assembly, so keep track what goes where. Also-also, mark the roll motor's orientation. Also-also-also, good time to spin the Roll bearing, as the grease tends to pool at the bottom of that bearing where it has little value.

That was a lot of written info, hope you got it... I did consider doing a disassembly video back when, but realized it would be two hands and a gimbal with very little close in shots.

Your questions indicate you comprehend well, so I'm fairly certain you'll succeed. If you get into a bind, just pause as it is fairly intuitive once thought through. Ask if you have further questions, everyone learns from the conversation.

Saving one gimbal at a time, long live Solo...

sirminder · Jun 8, 2019

Success...sort of.

Rich, thanks for the tips and advice. I must have read your comments here and on other threads about 10 times before I went ahead and started. I had been putting off taking apart the two Gimbals and finally got around to it. Partly because I kept on thinking of a way to bend the arms back once I got them out, but just looking at the Gimbals wasn't going to get me anywhere. So at last, I did it and it wasn't that hard actually. I made some notes of my findings and made some steps for anyone else interested.

Gimbal B
- Used. Previous owner had crashed and had tampered with it.
- Yaw arm looks slightly bent. Roll arm has a small dent and scratches and slightly bent too.
- Boards could have been damaged...not sure
- Does not keep balance when powered on and like to dance. Can keep balance for a few seconds, but only if guided first by hand. [Need to test in High Torque Mode]
- Video and Tilt/Paddle control work.
- Silicone Glue had been removed from the ribbon cable connector on the Roll motor board. The grey Fastener on the Ribbon cable connector is a bit damaged, but still working.
- Yaw motor shaft had a bit of play when holding the Yaw arm and wiggling Yaw motor back n forth. Tried to tighten the yaw arm shaft screw (perpendicular screw on Yaw arm), but would not go any further. Removed screw to inspect and noticed it was broken slightly above where the loctite is ~1.5mm. Yaw motor shaft did become loose, but ribbon cables impeded any further movement. Grub Screw was missing. Placed screw back in and was able to tighten a little. Perhaps this is where previous owner stopped, because in order to proceed, ribbon cables on Yaw board need to be removed and the glue on both Yaw ribbon cable connectors is still attached.

STEPS FOR REMOVING YAW ARM ONLY
- Remove back cover for Roll Motor (2 screws)
- Peel off Silicone glue to expose Ribbon Cable and connector (Xacto Knife and Tweezers)
- Mark Position of Roll Motor with relation to Roll Arm
- Remove Roll Motor Assembly (3 screws fine thread) and loosen Roll Motor Shaft (1.3 Hex Grub Screw)
- Remove Roll Motor Board by peeling off Ribbon Cable (Blow-drier Med Heat Low Fan ~45 sec.) **Optional but makes it easier**
- Place Roll Motor Assembly back to prevent damage to Ribbon Cables going to Roll Arm (1 screw OK) **Optional but makes it easier**
- Carefully pull off Ribbon Cables from Yaw Arm (Blowdrier again and don't use anything sharp)
- Mark Position of Yaw Motor with relation to Yaw Arm **Not really necessary??**
- Remove Roll Motor Assembly and Separate Yaw Arm from Roll Arm
- Inspect, Clean and Re-Oil bearing on Roll Arm if necessary
- Loosen Yaw Motor Shaft (1.3 Hex Grub Screw) and Shaft Screw

The whole process took about 10min with the careful removal of the Ribbon Cables taking about half that. As Rich said, take it slow and don't rush.

Here are pictures of the Yaw Arm from Gimbal B

And here is the Yaw Arm from Gimbal A

Ouch! Is what I said when I compared the two. One can clearly see how far off the Arms can be when using Rich's Rod Trick.

I'm not sure if its even worth measuring how far the second one is.

I swapped the Arms (B to A) on the Gimbals and gave it a go.

RESULTS - Yaw Arm Swap
- Gimbal A boots up with amber and then breathing green light
- Then, pans to the Right and Tilts/Rolls Left (CCW)
- Finally, it levels out and is able to maintain Level, but is still pointing to the right side almost as much as before...weird/odd.
- Gimbal control, Video, GoPro Control, everything seems OK. No errors reported

NEXT STEPS/THOUGHTS
Before I attempt to bend any of the Yaw Arms back:
A. Would it be possible to make any adjustments in MP in order to calibrate/fine tune where the Gimbal is pointing to?
-- Maybe, but does not look too promising...[unconfirmed]
B. Is it possible to "off-set" the Yaw Arm from the Yaw Motor Shaft? i.e. Loosen Yaw Arm and turn it to the LEFT so that it does not point too much to the RIGHT when the Gimbal is activated?
-- Need to look into this as there are other threads concerning the "Drummer Syndrome". If it works on the Roll Arm/Motor, could it work for the Yaw Arm/Motor?
C. Forgot what was C, but it will come to me

Rich and anyone else, feel free to correct if I left out anything in the steps above. And if you can share any more advice, you are more than welcome.

RichWest · Jun 8, 2019

Really accurate posting and details. More conversations on the subject, mo'better.

A. I've never used MP to adjust the gimbal, so you are on your own.
B. I find you can catch the shaft adapter not perfectly to the shaft's keyed flat. Maybe 1-2 degrees offset. Same when tightening the Yaw board, you have a little play in how the board aligns. It can add up...

It maybe the camera's parallax, but it appears you may have a slight twist on the Y axis of the yaw arm. If this is true, then you'll get an off alignment of the camera.

The 6mm rod I use tends to line up (bisect) over the bearing hole. I also use a right-triangle to check for twist as mentioned above. As well you can use the rod as reference point to measure the parallel between for the shaft-adapter hole's alignment to the back plate (as pictured). It's all right angles and parallels when correct.

To add, I've seen a couple yaw motors with bent shafts. I don't think they can be straightened reliable or at least not worth the trouble having many spare parts... Still this is something to check when tearing down a bent gimbal.

sirminder · Jun 11, 2019

Thanks Rich. I was hoping to follow your footsteps and document things half as good as you at least.

But, I have taken one step forward and two steps back....

I managed to bend the worst of the two Yaw Arms to about 95% back. It did not look that bad, but I wasn't completely satisfied. Nonetheless, I wanted to see how Gimbal A would behave it its original Yaw Arm almost back in shape:

- Everything was put back in place and powered up the Solo
- Amber Light followed by breathing Green light
- Camera was almost pointing the direction it should be. Perhaps 5° or so off, but could be usable.
- Strange noise coming from the Roll Motor and Roll Arm was not leveled

At this point I turned off the Solo and started to take the Gimbal apart. That is when I realized that I forgot to make sure the Roll Motor was aligned with the Roll Arm according the the markings I made AND tighten the Shaft screw on the Roll Motor.....DOH!!! ?‍

The marking on the Roll Motor was almost 180° off from where it should have been! I was so eager to find out the results, that I overlooked this step when putting it back together. I checked everything once again, assembled Gimbal and place it on the Solo for another test.

Drum roll...... IT LEARNED TO DANCE!!

Great, I now have two dancing Gimbals!

Not only that, but I somehow managed to ruin/damage the Roll Motor on what was the better Gimbal (A). There is some friction and nasty grinding noise when I turn it by hand. Either a) something got lodged in the bell housing, somehow b) bearings are bad c) windings got damaged due to me not making sure the Motor Shaft was secured.

I have no idea.

However, at least I could use the Roll Motor from the other Gimbal and continue where I left off....making sure to align the Roll Motor to the Arm this time. And once again...the dancing queen is back.

I am completely perplexed and don't have a clue on what to troubleshoot next. Although this Gimbal had a badly bent Yaw Arm, it was able to keep balance without any dancing whatsoever. That at least tells me that the IMU was not damaged. The only issue was it was't pointing where it should. Now, after bending back *almost* the same arm, it joined the other Gimbal in the cancing club.

Perhaps:
- The the Pot on the Roll Motor board is off by a couple of turns. If so, in which direction. Better yet, I should measure it!
- The ribbon cable got damaged...need to check continuity. If so, use spare or game over.
- A component got damaged...how to check? If so, game over.

Sorry no pictures this time.

RichWest · Jun 11, 2019

sirminder said:
Perhaps:
- The the Pot on the Roll Motor board is off by a couple of turns. If so, in which direction. Better yet, I should measure it!
- The ribbon cable got damaged...need to check continuity. If so, use spare or game over.
- A component got damaged...how to check? If so, game over.

You have a really good point...and maybe the cause. I took a pot apart back when, it's a thin film type, capacitive maybe. I was never able to ID a replacement. For whatever reason I never bothered to meter, never assumed it could be the cause. Will try to meter the parts I have this evening and report back...

The HDMI ribbon cable is a home run through the gimbal, so it's a all or nothing type of thing in my book. The data ribbon does have a connector at the camera holder, so with some effort could be swapped. Separating the two ribbons maybe the challenge...

The three motors appear to be identical in all respects. So you should be able to move them around from axis to axis. Shaft adapters are the variable to what axis.

Just a fine tuning thought, related to the yaw assembly...maybe roll motor as well. I've found you can set the shaft adapter in too tight, causing a motor to bind. Mainly sandwiched between the pot and bearing. I secure the adapter once the sandwich is assembled.