Servos T-Rex 500 DS510 Servo rebuild

[Doum066]

Greetings guys,

A few months ago i've lost my 500 in a corn field... the farmer found it a few weeks ago, or should i say passed over it and it went in his harvest machine. I've started the rebuild process and first started to see how the electronics was.. and amazingly, after 2 months in a firld, all electronics are find, i'Ve opened all of them mostly (BeastX, Servos, Motor..) I do have a question though, i'Ve changed my 3 swashplate servos (DS510 with plastic Gear) but somethings gets me wondering. 2 servos out of 3 are now stiff, a bit hard to move by hands, but when all connexted, they all move correctly, all 2 moves at same speed and so on.... anyone has an idea what can cause this?

Thanks,

Doum

 

[murankar]

Gaba Jr.

Glad to here you got your bird back. Most other people would have kept it. Good luck on the rebuild.

 

[pvolcko]

Hard to move after servo gear replacement: Could be you need some grease in the gears or on the face surfaces that contact each other. I'd also seen issues with the smallest gear at the bottom that's driven by the motor being tight on the shaft it mounts to, causing the whole drive train to be sluggish even when under power. If you replaced the gears because they stripped, there could be a piece of plastic floating in there that is causing binding. Make sure to clean out the grease already in there or at least inspect it closely for plastic pieces/shavings from stripped gears.

And, of course, servos aren't designed to be driven from the output. They have a relatively high amount of resistance when driven from the output. With metal gears you can press it and not really risk stripping anything out, but with plastic gears it is entirely possible to strip a gear. So it may just be the tolerances of the replacement gears and completely normal. I've certainly had replacement sets that behaved like this and I've had them where they were easily driven from the output side. When they were hard to drive from the output, after using them for a while I found the "loosened up" a bit and became easier to move from the output.

 

[Tony]

pieces of broke gears, or your pins not in the holes is what comes to mind to cause a tight servo. Either way, you need to take it back apart to verify.

 

[Doum066]

pieces of broke gears, or your pins not in the holes is what comes to mind to cause a tight servo. Either way, you need to take it back apart to verify.

Replaced all gears, tok them out and put it back in place a few times, didn't do anything, i then tried to replace the pins, still nothing, tried to take out the bottom part to take a look on the top of the PCB, but can't take it more appart than the bottum platic part... i was out of idea, so i came here to see... i even compared the soft one, with the 2 stiff one, and all looked alike.. odd, but thanks for the reply Tony

- - - Updated - - -

Hard to move after servo gear replacement: Could be you need some grease in the gears or on the face surfaces that contact each other. I'd also seen issues with the smallest gear at the bottom that's driven by the motor being tight on the shaft it mounts to, causing the whole drive train to be sluggish even when under power. If you replaced the gears because they stripped, there could be a piece of plastic floating in there that is causing binding. Make sure to clean out the grease already in there or at least inspect it closely for plastic pieces/shavings from stripped gears.

And, of course, servos aren't designed to be driven from the output. They have a relatively high amount of resistance when driven from the output. With metal gears you can press it and not really risk stripping anything out, but with plastic gears it is entirely possible to strip a gear. So it may just be the tolerances of the replacement gears and completely normal. I've certainly had replacement sets that behaved like this and I've had them where they were easily driven from the output side. When they were hard to drive from the output, after using them for a while I found the "loosened up" a bit and became easier to move from the output.

Thanks for the reply.

I've added grease and cleaned all up already, ill take them apart and look more closely... First time i replaced the gear, i never had any problems.. this time they are stiff... When i take all gears off, and i only have the smallest brass gear that is driven from the motor, i get no problem, it seems to be spinning no problem, but when i add all gears it's when they get stiff, i even took the gear from my Servo that is moving softly by hand and put them on the stiff servo, and vice versa, and nothing changed, the stiff one was still stiff with the other's gear and the smooth one, was still smooth with the other one.... but as i am typing i just realise something, i've trade all gears to one another, besides the little brass one.. guess i'll try this out tonight.... if it does change something, than the little one is the problem...

Thanks

 

[pvolcko]

I don't know if it is really a problem at all. I've had replacement gears that do this same thing, hard or impossible to move via the output shaft, and work perfectly fine driven the normal way by the servo motor. If it works via the servo motor and no sluggishness in the response between the three servos (fast collective jitters on the bench will show it) then run with it and don't sweat it.

 

[Doum066]

I don't know if it is really a problem at all. I've had replacement gears that do this same thing, hard or impossible to move via the output shaft, and work perfectly fine driven the normal way by the servo motor. If it works via the servo motor and no sluggishness in the response between the three servos (fast collective jitters on the bench will show it) then run with it and don't sweat it.

Yep that's what i thought.. the only concern i had was, they are plastic gears, so i was kinda affraid it could broke them if they were too stiff... but if you also had those kind of issue with replaced gears, guess i'll follow your words and leave them as is.

 

[pvolcko]

Just test things out before flying. Like I said, with throttle hold on, outside, do some quick full positive to negative to positive swipes with the collective stick and watch servo response. MAke sure none of the reactions lag the others. The other test I do is to hold the heli by each of the three swash points in sequence, doing a full up/down with the collective while holding it with each. Make sure the torque is enough to pull the heli up and no skips indicating a striped gear.