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gkatz

50$ range servo category

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I've got a few SPT4412s. I do notice either a centreing issue or something else about steering/signal on my hot motored TT-02SR (and binned one SPT for a sort of asymmetrical action) but my XV-01, truggified B64 and Falcon seem OK with theirs. Maybe a bit hit and miss? Or maybe on these cars I've only really run on either low grip or short postal circuits I just haven't noticed. 

Anyway, I'm quite looking forward to the Power HD R12 I've got coming too. 

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On 1/14/2024 at 2:46 PM, BuggyDad said:

I've got a few SPT4412s. I do notice either a centreing issue or something else about steering/signal on my hot motored TT-02SR (and binned one SPT for a sort of asymmetrical action) but my XV-01, truggified B64 and Falcon seem OK with theirs. Maybe a bit hit and miss? Or maybe on these cars I've only really run on either low grip or short postal circuits I just haven't noticed. 

Anyway, I'm quite looking forward to the Power HD R12 I've got coming too. 

I went out testing the SPT again, after cleaning everything on the car to make everything as smooth as possible in the already pretty clean steering... Just because I am stubborn. Well nope... It's just not drivable. Keeps turning, and a lot, after every corner, left or right. So I figured I wouldn't donate this... thing... and opened a return on eBay. The shop  offered generously a 4$ rebate 🤣

QqTiU3f.png

I guess I'm just not a hit-and-miss 'bargain' electronics kind of guy...

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1 hour ago, Pylon80 said:

I went out testing the SPT again, after cleaning everything on the car to make everything as smooth as possible in the already pretty clean steering... Just because I am stubborn. Well nope... It's just not drivable. Keeps turning, and a lot, after every corner, left or right. So I figured I wouldn't donate this... thing... and opened a return on eBay. The shop  offered generously a 4$ rebate 🤣

QqTiU3f.png

I guess I'm just not a hit-and-miss 'bargain' electronics kind of guy...

If you have one that isn't right, they should refund you in full IMO. When I say "hit and miss" I just mean I suspect there's more of a chance you get one that isn't right. I don't think they have any less of a responsibility to replace/refund a bad one. In my case, I just didn't ask, because I either didn't know what the problem was or didn't have the knowledge to explain it, either of which is on me I suppose. That said, asking is not necessarily getting, and it's going to be harder to get a refund out of AliExpress than LHS, which for me is an obvious part of why AE is cheaper, so in a sense SPT servos are cheap because of their source/distribution route, but only by comparison with a locally available servo at say up to 2x their price, they probably shouldn't be considered against a servo costing much more than thst. 

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1 hour ago, BuggyDad said:

If you have one that isn't right, they should refund you in full IMO. When I say "hit and miss" I just mean I suspect there's more of a chance you get one that isn't right. I don't think they have any less of a responsibility to replace/refund a bad one. In my case, I just didn't ask, because I either didn't know what the problem was or didn't have the knowledge to explain it, either of which is on me I suppose. That said, asking is not necessarily getting, and it's going to be harder to get a refund out of AliExpress than LHS, which for me is an obvious part of why AE is cheaper, so in a sense SPT servos are cheap because of their source/distribution route, but only by comparison with a locally available servo at say up to 2x their price, they probably shouldn't be considered against a servo costing much more than thst. 

The refund shouldn't be a problem as it was on eBay. For all their greed and horrible fee policy, you have to give it to them, they really do protect the buyers 👍

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I'm currently in the market for a new servo. I want one that works with a Tamiya esc, without an external BEC. That severely limits my possibilities I think, since the internal BEC is only 1.5A. I've read about this rule of thumb that a servo draws 1A for every 3kg/cm, but then there might be exceptions.

The picture is from a Savox SC0253MG. I've heard about the power hunger of Savox servo's, but I've also heard about good experiences. Besides, this is one brand that lists current with their servo specs, something PowerHD doesn't for each servo.

Now, where do I have to look to decide if I can run it without an external BEC? Is that stall current? In that case, would I be safe with this one? Does anybody has experiences with that servo?

Screenshot_20240207_055943_Samsung Internet.jpg

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44 minutes ago, Rijkvv said:

I've read about this rule of thumb that a servo draws 1A for every 3kg/cm, but then there might be exceptions.

Now, where do I have to look to decide if I can run it without an external BEC? Is that stall current? 

It was me that said that, it was off some robotics forum I believe, and it was quite an old post. I believe things had became more efficient these days so 1A per 3 - 4kg may not always be true. However, it still applies for some servos; for example JX's LP 9kg tested at nearly 3A.

I test each servo I get to make sure they don't exceed the BEC, at least not by too much. I don't trust manufacturers' numbers as each one I tested differs from the claimed numbers, always higher. Your best bet is to test it to see how many A it draws.

Stall current is the one to look at as even when driving straight, it is not really at idle. It actually has to draw current to work to keep it at neutral, fighting against the forces of the car moving.

In my experience, the TBLE is extremely sensitive, I had used 1.7A servo on it and it tripped. Most other ESCs, like say the 1060, has a 3A BEC but 4 or 5A surge so one can go over a little. The TBLE seems to trip at exactly 1.5A. YMMY.

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Futaba or Hitec.

Keep in mind that there is every incentive to "fudge" servo specs, especially for "no-name" manufacturers.

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just a small note.
i have a new JX 4409MG and Injora injs014 low profile budget servos which I put to a speed test. both pretty similar speed wise but the jx is super jittery and seems super unstable as oposed to the injora which is super smooth and does exactly what is expected...
just my small test and experience... 

and so, no JX for me in the future.

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It looks like the SPT4412LV is a lot lower in supply than it used to be on eBay, and also the few that are for sale have different designs - a new rounded sticker not the squarer type of the older units plus the car design on the side is no longer there on all images.  Do we think this might explain the issues in centering, in that the supplier has changed and the quality has dropped?  Or that knock-offs are now appearing?

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On 2/27/2024 at 9:11 AM, Twinfan said:

It looks like the SPT4412LV is a lot lower in supply than it used to be on eBay, and also the few that are for sale have different designs - a new rounded sticker not the squarer type of the older units plus the car design on the side is no longer there on all images.  Do we think this might explain the issues in centering, in that the supplier has changed and the quality has dropped?  Or that knock-offs are now appearing?

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The one I bought that did not center (I got a full refund on eBay) was the one in the top picture.

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