Servo choice

[Optic]

Hi all,

I'm looking to also make my own SpotMicro and am currently putting together a BoM.

The cost difference between the MG996R and the CLS6336HV is large (~£5 Vs £25 each). I'm happy to commit to the more powerful CLS's if it's already known the MG996R's just aren't powerful enough, but I was wondering if anyone has found anything in the middle ground pricing between these that could work? 

Cheers

[MattthiasM]

I use Wishiot DS3218. They are 20kg and cost 15 Euros. I have not tried them in the robot yet, so I can't tell you if they have enough power. They do have an aluminium body, which should help greatly with heat dissipation.

[Optic]

I use Wishiot DS3218. They are 20kg and cost 15 Euros. I have not tried them in the robot yet, so I can't tell you if they have enough power. They do have an aluminium body, which should help greatly with heat dissipation.

They sound like a decent alternative. I've seen others around the £10-15 point which are also 20-25kg however having not actually built a spot yet I don't know what the limiting factor with the MG996R is; does it just not work at-all, or is it more that the servos struggle.

Given that the servos are quite possibly one of the biggest outlays initially in making this, I'd rather not spend £70 on MG996R and regret it, equally I'd rather not spend £300+ on 12 of the CLS6336HV if realistically it's going to be fine on the others, at-least to start with. Really I just would like to understand if the MG996R's work at-all.

[epin]

Hi all,

I builded my spotmicro with RDS3135 Servos (35kg-cm@7.4v) for around 17€. I hope test this soon

[brad]

I've been able to have some success with the MG996R from hobbyking. You have to make sure your power supply can put out enough power as it draws lots of amps. In this video I've overvolted to 10-12 volts, though with motion it drops as my power supply can only supply about 55 watts at that voltage. Curious to hear what others experience has been:

https://youtu.be/yPimZT-VNII

[Optic]

I've been able to have some success with the MG996R from hobbyking. You have to make sure your power supply can put out enough power as it draws lots of amps. In this video I've overvolted to 10-12 volts, though with motion it drops as my power supply can only supply about 55 watts at that voltage. Curious to hear what others experience has been:

https://youtu.be/yPimZT-VNII

 I ended up buying 12 of the Hobbyking TowerPro MG996R's, in-fact they are arriving today so I'll see soon what luck I have.

[Optic]

My servos just arrived and initially playing around with my bits that are printed, It looks like you need to modify the TowerPro MG996R horns (trim them down mostly) to make them fit your bits here Brad (https://www.thingiverse.com/thing:3761340/files).

Is that correct? I don't fancy chopping everything unnecessarily 

[brad]

My servos just arrived and initially playing around with my bits that are printed, It looks like you need to modify the TowerPro MG996R horns (trim them down mostly) to make them fit your bits here Brad (https://www.thingiverse.com/thing:3761340/files).

Is that correct? I don't fancy chopping everything unnecessarily 

That is correct. I put some leg assembly instructions here: 
http://spotmicroai.readthedocs.io

You end up cutting the servo heads down at the second hole. You also have to flip two of each piece of the leg along the X axis when printing, which I'm not sure is super clear on my thingiverse repo.

[brad]

[quote pid='42' dateline='1566445631']
That is correct. I put some leg assembly instructions here: 
http://spotmicroai.readthedocs.io
[/quote]
Lots of pictures...hopefully they make some sense.

[Optic]

So annoyingly it seems the mounting screws that come with the TowerPro MG996R's are too small for the holes in the 3d printed parts (I've printed yours Brad), they are too narrow and get no purchase on the sides at-all. Looking at the models in Fusion 360, the holes look to be 3.2mm diameter and the screws included with the servo are 1.9ish.

I'll have to rummage around and try and find something bigger.

I'm also having issues getting the nuts in to attach the two shoulder pieces, the holes here seem too small to fit an M3 nut, so I may need to modify and re-print these.

On that note, has anyone thought of modifying the mounting of the servos so they don't use self-tapping screws into the plastic which is kind of short sighted. Having captive nuts and machine screws if possible would be much better imho.