90:1 vs 180:1 gear ratio

[mbridge87]

Hey everyone,

I bought some geared rotational stages from a company on AliExpress and I'm 99% sure they sent the wrong ones but there are no markings to be able to tell. Two should have a gear ratio of 90:1 and one should have a gear ratio of 180:1. The company is refusing to take responsibility and I just want to check I'm not going mad and completely wrong here.

Correct me if I'm wrong but a 90:1 gear ratio should move at double the speed of a 180:1, correct? Meaning after one full turn the 90:1 would move double as much. I recorded a couple videos to prove this but they're saying otherwise. These are the videos:

https://squaremountain.co.uk/wp-content/uploads/2021/01/Drive-Explanation-Part-1.mp4?spm=a2g0s.imconversation.0.0.631d3e5fEyGkch&file=Drive-Explanation-Part-1.mp4

https://squaremountain.co.uk/wp-content/uploads/2021/01/Drive-Explanation-Part-2.mp4?spm=a2g0s.imconversation.0.0.631d3e5fEyGkch&file=Drive-Explanation-Part-2.mp4

Thanks

[Clive S]

Hey everyone,

I bought some geared rotational stages from a company on AliExpress and I'm 99% sure they sent the wrong ones but there are no markings to be able to tell. Two should have a gear ratio of 90:1 and one should have a gear ratio of 180:1. The company is refusing to take responsibility and I just want to check I'm not going mad and completely wrong here.

Correct me if I'm wrong but a 90:1 gear ratio should move at double the speed of a 180:1, correct? Meaning after one full turn the 90:1 would move double as much. I recorded a couple videos to prove this but they're saying otherwise. These are the videos:

https://squaremountain.co.uk/wp-content/uploads/2021/01/Drive-Explanation-Part-1.mp4?spm=a2g0s.imconversation.0.0.631d3e5fEyGkch&file=Drive-Explanation-Part-1.mp4

https://squaremountain.co.uk/wp-content/uploads/2021/01/Drive-Explanation-Part-2.mp4?spm=a2g0s.imconversation.0.0.631d3e5fEyGkch&file=Drive-Explanation-Part-2.mp4

Thanks

That looks correct to me. Can you alter the software to suite?

[mbridge87]

Not really I'm afraid. The 180:1 and 90:1 are on the pan tilt head, which means they stall at different speeds and have different payload capacities. It would be much better if the two axis were the same. I could put both 180:1 drives on the pan tilt head but since the 180:1 are a little stronger they're supposed to be used for another purpose, plus I wanted the additional speed of the 90:1 for the pan tilt.

I wish I could switch them around, would make things a lot easier.

[Clive S]

Not really I'm afraid. The 180:1 and 90:1 are on the pan tilt head, which means they stall at different speeds and have different payload capacities. It would be much better if the two axis were the same. I could put both 180:1 drives on the pan tilt head but since the 180:1 are a little stronger they're supposed to be used for another purpose, plus I wanted the additional speed of the 90:1 for the pan tilt.

I wish I could switch them around, would make things a lot easier.

I am not understanding this. Are you saying that the motors stall ? So 180 turns of the motor should be 1 turn on the output.

[mbridge87]

I'm talking about the speed at which the motors stall. So, as you'd expect, the 180:1 is a lot slower than the 90:1 and hence cannot reach the same speed before stalling.

I'd prefer that the faster motors be on the pan tilt head hence wanting the 90:1 versions there. Does that makes sense?

[Clive S]

I'm talking about the speed at which the motors stall. So, as you'd expect, the 180:1 is a lot slower than the 90:1 and hence cannot reach the same speed before stalling.

I'd prefer that the faster motors be on the pan tilt head hence wanting the 90:1 versions there. Does that makes sense?
Yes of course I should have known better.

I wasn't thinking about the motor speed 😡

[m_c]

I'm possibly wrong due to lack of sleep, but shouldn't a 90:1 turn 4 degrees for every input revolution?
Which would mean you've got one 180:1, and two 360:1 reducers.

[mbridge87]

You're totally right. Someone else pointed this out to me elsewhere and I hadn't even thought about it. I was so focused on how the company wouldn't acknowledge this obvious difference.