Proper use of ball bearing for a vertical rotation (azimuth rotation for a ground station)

Submitted by Fun-Palpitation81 t3_101p8dh in DIY

Hello all,

Sorry for title gore, see this picture for what I am trying to do.

My understanding is that I can support the outer side of the bearing with the base, but then that leaves a thin shaft (inside of the bearing) between the stepper and the satellite dish, which has weight, and won't be completely balanced. I doesn't make sense to me that all of the movement and weight would be concentrated on a single shaft.

Is there a better way to achieve this rotation, I tried to google, but I don't even know what to google for this.

Any direction or input would be greatly appreciated.

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Comments

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bwhitso t1_j2otr2q wrote

Look up “thrust bearing”

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derphurr t1_j2oz1r0 wrote

You want a turret / slewring bearing, and many have teeth on one ring, which is better way to drive with it.

Or turntable bearing, but probably not a good idea if you consider wind loads.

You'll have to list diameters and weight for any useful recommendations

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Fun-Palpitation81 OP t1_j2pemzd wrote

thanks!

I'm a little confused about which side i would attach the dish too.

Here is a picture.

Does the dish attach to the inside, and if such, wouldnt all of the weight be on the bearings (as there is nothing to support it underneath).

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derphurr t1_j2pfymp wrote

Correct, they should have ratings, usually hundreds lbs to 30,000 lbs.

If there are teeth on outside, you can drive it with a belt or teeth. But the stationary side didn't have teeth.

You haven't indicated any idea what kind of weight you need to rotate.

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Fun-Palpitation81 OP t1_j2phrbb wrote

the dish is actually a model, thus the weight is not that important. However, I wanted to design it realistically to what would be done.

Thus, I should put teeth on the inside ring, and drive it using teeth on my stepper motor. To increase the "torque" on my stepper, I believe I can also use teeth ratio

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derphurr t1_j2plh38 wrote

Omg... Whatever

HOW MANY FUCKING LBS DO YOU WANT TO DESIGN THIS FOR? 20,100, 5000?

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Fun-Palpitation81 OP t1_j2pmvbd wrote

~ 500 grams

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derphurr t1_j2q1z2m wrote

Lolol. (Unless you meant kg)... You could mount it directly to stepper shaft. But technically risk eventually wearing out motor.

Maybe a small right angle gear box. https://www.ondrivesus.com/miniature-gearboxes

You certainly don't need any significant bearings.

I would personally hose clamp tubing between the two shafts as a coupler and put little wheels/dollies/ upside down ball bearing wheels for antenna assembly.

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discretion t1_j2soz24 wrote

Per the last comment he made that you replied to, this is for modeling purposes. So "just whatever" might work for a 500g dish, but it won't scale.

Just throwing that out there.

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nixiebunny t1_j2pjrn6 wrote

I work on radio telescopes. They typically have a large diameter roller bearing to support the yoke. The azimuth drive is completely independent of this bearing. Some use a friction roller, others a ring gear with two motors with pinions, one has a direct drive motor built into the housing (not recommended).

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Fun-Palpitation81 OP t1_j2pnfam wrote

Thank you, for my elevation stepper, I am using two rolling bearings, directly driven by a stepper - I'm using direct drive to save on space, but if I haven't tested that I'll have enough torque.

For the azimuth drive, I will try using these slew bearings, with the benefit that I can feed my elevation stepper motor wires through the center.

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Fun-Palpitation81 OP t1_j69174h wrote

I ended up going with a design like this AWS ground station, which has two 180 degree range motors.

I'm curious as I ran into the issue when I was instead using one 360 degree azmiuth stepper, and a 180 degree elevation stepper - how do you control that the wiring doesn't get twisted with azimuth rotation, as the elevation stepper has to rotate with the azimuth?

I'm just curious how this is done with real radio telescopes/ground stations.

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