Trouble over the weekend (and servo splines)

[Wayne]

OK - Why does this site always have to have a melt down when I'm away from the computer for a few days?

Sorry all, Will be deleting all of the off topic stuff shortly as it had little real content and many request to clean up the thread, sorry you all had to deal with it. Thanks to our normal members for keeping their heads straight and trying to post factual stuff, and generally trying to cool off the hot member. My hat is off to you all.

To be clear I have nothing but respect for Tomas and his products. Top Quality all the way. What possible benefit would I have to attack his products? You all know me, and the only rumors I like to spread are about my bad piloting skills and poor building habits. If I have an issue with a manufacturer, guess what, I stop buying from them.

The history behind all of this started when we started getting complaints via email that LDS arms were not fitting some KST servos. First customer had a set of 4 LDS trays, and one of the 4 servo horns would not fit. We pulled one from inventory for him, and when he got that, it also did not fit. To complicate all of this TLS had updated their packaging. TLS originally adopted some SKU#s from us as he never had any. This was GREAT for sorting out his wide range of products, but then he adapted the numbers and replaced them slightly. This caused a lot of confusion for us and our customers. We have all learned from this and Tomas will not repeat this.

I'm still not sure what is going on as many customers are perfectly happy, and some are running into this issue. This has been shared with Tomas. By the way, the comments on his site are not from us, those predated us running into issues. I adopted his warning onto our site to help guide our customers, same reason Tomas out it up on his site.

So is it burs? Is it a change at KST? Or are they just really tight?

At Aloft we generally do not like trying to answer servo spline questions as it is a real pitfall. We have seen servo brands change output splines with no warning. We have had tolerance issues with servo arms. And most importantly, a servo can have a given number of splines, but different diameter or different geometry that will result in a very poor fit. I have thousands of unsellable alloy servo arms collecting dust from this little learning curve. So while we will do our best to answer customers, we always try to explain the above.

 

[Tahoed]

Here we go. Straight from the man himself...
Dear Ed
Thank you for your support. KST A08 with a short output shaft seems to be designed for F3K, but the new version has a longer output shaft, so it has two versions.
The size of KST Sh08 spline is a bit larger. In the early stage, I designed the accessories according to x08 specifications.
It's understandable that most people don't understand the difference.
Thank you
Best regards
Tomas LIu

In other words, they will work on all the newer X08's and the 06. With the older HS 08's A's or whatever, due to the slightly different spline difference, they will fit, but hey are a lot tighter. I'll post some pics later with the different servos if there is a request for them. In other word's, depending on the versions (either Tomas' or KST) you might see some difference in the space between the case and the control arm, but if you are using the LDS components with the external bearing support, it shouldn't make much of a difference. Of course, you will need the correct servo frame. and the current 08 frames fit the older fully cased HS08a.

 

[2MUCH2DO]

Ok so....

I used servoRhamen X08 frames for A08 Servos, ironically on my magnus. I remember the fit being tight, and the first fit-up having to press them on. I thought that was by design, but was that actually the thing that all of this was about?

 

[Tahoed]

Ok so....

I used servoRhamen X08 frames for A08 Servos, ironically on my magnus. I remember the fit being tight, and the first fit-up having to press them on. I thought that was by design, but was that actually the thing that all of this was about?

Still not quite sure what went on there, but yes, the fit of either the ServoRhamen or Tomas' will be tighter, but both will work on the A08 HS08a or the X08 and there maybe a slight difference between the distance from the case and the control arm depending of which servo version with which version control arm you are using.

 

[Wayne]

I may occasionally post some info from Konrad- I WILL filter out the bits I do not love. This is what Konrad would like to add to this subject:

You asked me once if I had noticed any issues differences between the X-08 and HSO8 servo splines. I said yes I had. I noticed that when swapping between the HSO8 and X-08 servos the Servorahmen arms showed spline slop. I’ve also noticed that the splines strip in the plastic arms. After our talk I did a quick measurement of the spline using the 3 wire method to find the pitch diameter (all three servos the AO8 the HSO8 and X-08 use 15 count splines). I only did an N of one, as I only had one loose X-08 and HSO8. But I did measure a difference of close to 0.05mm in the pitch diameter. I don’t know if this is a tolerance issue, a production run issue or an undocumented change. Here I don’t have any secondary supporting documentation, as the KST web site is showing that the splines on all three servos (X-08, HSO8 and AO8) are the same. Of note the output shaft locations are not the same! From the same datum the center line of the output shaft for the X-08 and HSO8 is 6.11mm, The output shaft for the AO8 is placed at 5.85mm. This will cause issue with the alignment of the external bearing when using bearing supported servo trays.

Hope this helps to shed some details on the subject, and why we see Tomas listing things the way he has on his website.

I think it is fair to say that KST has invested in different gears for some of the servos for whatever reason and there are some differences. This is also one of the things that really sets KST apart from many other servos brands is his willingness to invest heavily into his products. To this day KST is the only company that I know of that was willing to invest into having their own IC developed for their servos. That is a monumental level of investment for a RC servo company. Some of this may have been driven by the industrial side of the business.

 

[Tahoed]

 

[2MUCH2DO]

I remember when the A08s came out there was talk that they were supposed to develop less slop over time than the x08, I wonder if this is all related to that Improvement.

 

[Doc J]

Here we go. Straight from the man himself...
Dear Ed
Thank you for your support. KST A08 with a short output shaft seems to be designed for F3K, but the new version has a longer output shaft, so it has two versions.
The size of KST Sh08 spline is a bit larger. In the early stage, I designed the accessories according to x08 specifications.
It's understandable that most people don't understand the difference.
Thank you
Best regards
Tomas LIu

In other words, they will work on all the newer X08's and the 06. With the older HS 08's A's or whatever, due to the slightly different spline difference, they will fit, but hey are a lot tighter. I'll post some pics later with the different servos if there is a request for them. In other word's, depending on the versions (either Tomas' or KST) you might see some difference in the space between the case and the control arm, but if you are using the LDS components with the external bearing support, it shouldn't make much of a difference. Of course, you will need the correct servo frame. and the current 08 frames fit the older fully cased HS08a.

Tomas told me yesterday that he's got his tolerances down to +/-0.005mm - thats about +/-0.0013"

Woo...at those tiny dimensions we are talking watchmaking. If you see the teeny 6mm IDS V-tail servo setup I'm working on with him its a bloody work of art.

The biggest problem the poor guy has (untill he started making his own servos that is) is that he's dealing with KST, and some types of the KST servos are made subcontract offshore, and some self made By KST here in Taiwan. Where its relatively easy to control tolerances yourself and with close partners, making the stuff elswhere is a whole different ball game - as I know very well.

But as Wayne said - Mr Tsou - the owner of KST cares about his products as much as Tomas does, so they are on it!

It gets complicated but I know Tomas and KST now have it sorted.

Cheers,

Doc.

 

[JustinMader]

So is it burs? Is it a change at KST? Or are they just really tight?

I tried pushing one on an X08 until my fingers hurt. Def different size/spline count. Aside from that, the build quality is really nice. Fingers crossed I can get an arm that fits.