Servos don't fit

[BarryReid]

Hi Guys

I bought TowerPro MG946R's for the steering as stated in the readme but after printing the wheel rotors they don't seem to fit at all. Just wondering if I am missing something.

[jakkra]

The margins might be a bit tight, and differences between printers could cause servos to not fit maybe. Is it way off, or could you sand the print a bit to get it to fit? If you only printed one wheel rotator, then you can in Fusion increase the margin a bit.

@fabriziofiorucci how did they fit for you?

[BarryReid]

Ye its quite a bit off and my printer is pretty accurate. I see in the cad model the server you have a model for is the MG996R not the MG946R like you have recommended in the docs. Could there be a difference there?

[fabriziofiorucci]

Hello,

margins are a bit tight indeed, but the overall assembly has to be sturdy, so it makes sense. I use a Creality Ender 3 and in some cases my servos (TowerPro MG996R) fit perfectly, in some other cases I needed to use a dremel with a sandpaper tip to allow for a bit more space. I didn't print/use the wheel rotator, I decided to use the stock aluminium rotator that comes with the servo.

[fabriziofiorucci]

[BarryReid]

Ye those MG996R's must be a different size, you may want to update your doc on the front page as the MG946R's are quite a long way off (not just a snug fit) their mounting holes also don't line up.

[jakkra]

I pretty much asumed that MG996R's and MG946R's are same, as I on the arm used both interchangeable. You can just bend those "pins/mounting holes" off from the print. I did that now I remember. Will work anyway.

Will update readme.

[BarryReid]

No servers are still too big to fit even with a bit of force :) I will try shaving off some plastic from the part and see how its goes.

[jakkra]

Like @fabriziofiorucci says, most parts in the rover work better if they are a tight fit. Some part might need some sanding and force to fit. If you are very far off, then come back and I'll update the model to give a litte more room for the servos.

[fabriziofiorucci]

If I can add a bit/if this can be useful: I printed the rocker bogie assembly and wheels using ASA-X and my homebuilt heated printer enclosure (without it I can't simply print ASA-X due to cracking/warping) and after printing there is some shrinkage anyway, so steering servos were a bit tight (some sanding solved that). When printing the body and arm I went for PLA and here warping/shrinking is virtually non-existing: when fitting the servos I needed to sand it even more if compared to the rocker bogie.

[jakkra]

I will increase the margins around some servos next time I'm working on the Rover model (unless @BarryReid can't sand around it)

By the way a little teaser:

[fabriziofiorucci]

This is super cool! When are you going to post the f3d files? ;-) At the end of the day did you go for LoRa+WiFi?

[BarryReid]

Hey, ye if we could get a bit more space in the model that would be great, I need to sand so much that the walls of the print are almost non existent. I think this version of the servo is just a bit wider than the MG996R

[BarryReid]

When I get home I will send you the measurements of the MG946R

[jakkra]

Ok, that's a bit to much to sand, I will update the model tomorrow! I'll compare it with my servos and see how off it is.

For the controller, yes I went with both wifi and lora. Code, CAD and website for the phone is all about 80% done. Have not finished final design of the back of the controllers yet. I'll probably finish it up the next 2 weeks and make the repository public.

[jakkra]

Hi @BarryReid, I realised the servo model I have used for reference is a about 1mm smaller than the real one. I measured my MG946R and MG99R and they have the exact same size. I made some more room in the "original_wheel_rotor" parts. Will those dimentions work for you? Should give about 0.25mm clearance.

[BarryReid]

Mate that's should be perfect! Did you make the change on the back and front rotors? I tried to download to check but cant see the updated CAD model in the GIT.

[jakkra]

No, I didn't upload, wanted to get ok from you first. Will update asap.

[BarryReid]

Thanks mate, did you make the change on the back and the front rotors?

[jakkra]

Yes all 4, exporting now.

[BarryReid]

Hey @jakkra thanks so much for making those changes. I printed this part again overnight and have just completed a test fit.

It now however seems to be a bit loose. Just wondering if you expanded it by a total of 1mm or if you did 1mm on each side?

I think if we made it half way between what it is now and what it was, it would be prefect.

Hope the feedback helps.

[jakkra]

No, I did 0.5 on each side, so in total 1mm. If it can move inside then it's a problem, but otherwise I don't think your print is wasted, it should be hold in place when servo head I screwed in place. But anyway I'll update the model tonight with 0.25mm on each side instead of 0.5.

[BarryReid]

Yip it moved ever so slightly. I think 0.25 on each side will be the perfect amount. The print should not be wasted as I will just glue in some single layer shims on each side of the servo. I will print the final rotor once you have updated the CAD and let you know the outcome.

Thanks

[jakkra]

Feel free to print the final rotor now, I have now updated the dimentions.

[k4m454k]

Same problem with TowerPro MG996R

I redid original_wheel_rotor element, changing the distance between the mounting pins

[BarryReid]

Ye, I just snapped them off, drilled some tiny pilot holes and screwed them in with a few self tappers.

[k4m454k]

Ye, I just snapped them off, drilled some tiny pilot holes and screwed them in with a few self tappers.

Barbarian =)

[jakkra]

Yeah just snap them off, seems as the distance between the holes are a bit different between some brands of MG966R. They don't really do anything.

[k4m454k]

Yeah just snap them off, seems as the distance between the holes are a bit different between some brands of MG966R. They don't really do anything.

I just redid this element and re-printed it. the perfectionist inside me rejoices

[jakkra]

@k4m454k hehe great! There are some things that are not perfect yet in the build, so you might need to compromise with your inner perfectionist some time later :wink: