What the newest cheap servo hotness?

[fyrstormer]

i have heard there is no such thing as a full titanium gear in a servo, just titanium coated....have i misunderstood or been told wrong?

Sent from my SM-G955U using Tapatalk

I've never heard of titanium-coated gears. I've heard of titanium-nitride coated gears (dull gold color), or titanium-carbonitride coated gears (flat gray color), which are definitely an improvement over bare aluminum, but those are both ceramic coatings that just happen to have titanium as a chemical component, the same way white porcelain has aluminum as a chemical component.

I use the Hitec HS-7955TG servo to steer everything except my touring cars. The official spec sheet says they have titanium gears. I admit I've never cut one of the gears in half to see if it's titanium all the way through, but it would honestly be more trouble than it's worth to make aluminum gears and then vapor-deposit a thin layer of titanium onto them. Titanium has a VERY high melting point.

EDIT: ...and titanium vapor is stupendously reactive. It would bond to everything in the vacuum chamber and present a significant fire hazard if it somehow leaked out. Titanium is so reactive it will actually burn in an all-nitrogen atmosphere (producing the aforementioned titanium-nitride coating), which is even more remarkable because a nitrogen atom usually hates to be chemically bonded to anything except another nitrogen atom. Fortunately, that spontaneously-forming oxide or nitride layer is stupendously inert, so that chemicals strong enough to set concrete on fire can be safely stored in titanium bottles.

HS-7955TG High Torque, Titanium Gear, Coreless Ultra Premium Servo | HITEC RCD USA

 

[fyrstormer]

Out of curiosity, which servo are you referring to?

Your post states "the gears shown above" - but this thread is many pages long... ;-)

Scrolling back, I was replying to your post about the DS3218, but I could've just as easily been replying to any other comment about aluminum gears.

The "El Cheapo but great for the money" DS3218 is mostly brass with what appear to be the two aluminum gears only touching brass gears, shouldn't be a worry there.

They are even labelled as such, and contact with brass is likely to reduce any potential galling.

That will prevent galling, yes. It introduces the possibility of galvanic corrosion instead, but pretty much any grease or oil would keep that to a minimum.

BTW - not all anodizing is "matte" in finish - and the product literature for the DS3218 does state:

Features:
- High-precision metal gears with hard anodizing
- CNC aluminium middle Shell
- waterproof rubber seals screws

So, stating "obviously" not anodized is untrue - they quite likely may be.

Not all anodizing is matte finish, but hard anodizing is. All anodizing is ultimately the same thing -- a microscopic honeycomb structure of metal-oxide ceramic grown from the surface of the metal object that was anodized. Hard anodizing on aluminum just means it is thicker than normal, produced using a process that involves stronger acid and higher voltage (usually sulfuric acid rather than chromic acid), but chemically the end product is the same. Cosmetic anodizing, like what you might find on a Maglite, is very thin and doesn't have any appreciable color of its own, which is why it can be dyed lots of different bright colors; that's also why it's so easy to scratch. Hard anodizing is thick enough to have a brownish-grey color of its own, and that limits the number of colors it can be dyed, because most colors will end up looking "muddy" from the color of the anodizing itself. But for engineering purposes like the gears in a servo, there would be no dye used at all, so the hard-anodizing would be left bare, and would appear as a matte brownish-grey color.

Even if they are not, (I don't believe all mfg claims - see my comments elsewhere on titanium servo gears!) somehow mine is still very tight and precise in use after 7 months of abuse... "thumbsup"

Glad to hear it. I'm not saying you made a bad purchase, I'm just saying if I were designing a servo I wouldn't use aluminum gears. For cheap servos, I'd rather use brass, and for expensive servos I'd rather use steel or titanium.

 

[durok]

Thanks, fyrstormer - for the detailed explanation and clarification.

I agree, the optimal materials are not used in the DS3218 - just as in the majority of inexpensive servos.

However, it's a great little budget servo that works incredibly well for it's price.

I sincerely hope to see more mfg release well-designed all-steel geared servos optimized for crawling - and I look at the ProModeler 470, the Holmes SHV500, and the Savox 2290 as the current ideals depending on your needs.

I personally think titanium gears (whatever their true composition may be) are best reserved for use for applications that require fast transit speeds but perhaps somewhat less ultimate torque output.

 

[holycaveman]

Thanks, fyrstormer - for the detailed explanation and clarification.

I agree, the optimal materials are not used in the DS3218 - just as in the majority of inexpensive servos.

However, it's a great little budget servo that works incredibly well for it's price.

I sincerely hope to see more mfg release well-designed all-steel geared servos optimized for crawling - and I look at the ProModeler 470, the Holmes SHV500, and the Savox 2290 as the current ideals depending on your needs.

I personally think titanium gears (whatever their true composition may be) are best reserved for use for applications that require fast transit speeds but perhaps somewhat less ultimate torque output.

The coated aluminum will outlast the steel. Mainly because of the contact area and treatment. The lower gear can not be TI or steel. Usially composite or aluminum. Aluminium being much more durable.

 

[Jim85IROC]

The coated aluminum will outlast the steel. Mainly because of the contact area and treatment. The lower gear can not be TI or steel. Usially composite or aluminum. Aluminium being much more durable.

I'm curious as to why with regards to both of your statements. I don't doubt that a properly coated aluminum gear has a higher Rockwell hardness on the surface than non-hardened steel, but I have a very hard time believing that the sheer strength of each tooth is anywhere near as high as the steel gear teeth.

Why can't the lower gear be steel?

 

[durok]

The coated aluminum will outlast the steel. Mainly because of the contact area and treatment. The lower gear can not be TI or steel. Usially composite or aluminum. Aluminium being much more durable.

That's neither a logical statement or a fact.

There are countless varieties of steel, just as there are of aluminum.

The various alloys of steel can then be hardened in a multitude of ways.

Discussions of large scale RC aircraft servos have often discussed the preference of steel over aluminum for servo gears.

Generally speaking, titanium is a harder metal than aluminum and is nearly as hard as heat-treated alloy steels.

That's the logical progression.

All of it can go out of the window if you are using lower-grade variations of any of those metals...

Also, it can be argued that long-term gear life may be less desirable than ultimate gear tooth shear strength for use in a crawler.

Servo gears do not endlessly spin full revolutions while meshed, but instead make small corrections while being subjected to resistance and impacts.

(As far as the need for one non-metallic gear, back some 10 years ago it was stated by Hitec somewhere that metal gear servos must have at least one plastic gear to avoid RF feedback from the gears to the pot that would cause glitching - not sure if that has been avoided with any other modern advancements? The 3BrothersRC G13 states "* All metal gears" in it's specs, for example...)

Here's a pic of a ProModeler steel-geared servo - not sure where the non-metallic or composite gear is hiding:

 

[fyrstormer]

I think he's saying that the larger of two meshing gears must be made of a softer material, to avoid inflicting premature wear on the smaller of the two gears. That is often done for gears that are continuously rotating, as in a transmission, but it isn't a requirement by any means. Furthermore, servo gears don't experience even wear across all of the gear teeth anyway, because they experience reciprocating rotation instead of continuous rotation. The gear teeth that are meshing when the output hub is in the "center" position will always get more wear than the rest of the teeth, especially on the gears closer to the output hub. So the concern about the smaller gear wearing faster than the larger gear is less important, because the wear on the larger gear is going to be more uneven, which ensures the larger gear will wear-out at a rate comparable to the smaller gear even if they are both made of the same material.

Anyway, from a design perspective, the gears only need to last as long as the rest of the servo; as long as they do that, it doesn't really matter whether the wear is distributed evenly between the larger and smaller gears.

 

[holycaveman]

That's neither a logical statement or a fact.

There are countless varieties of steel, just as there are of aluminum.

The various alloys of steel can then be hardened in a multitude of ways.

Discussions of large scale RC aircraft servos have often discussed the preference of steel over aluminum for servo gears.

Generally speaking, titanium is a harder metal than aluminum and is nearly as hard as heat-treated alloy steels.

That's the logical progression.

All of it can go out of the window if you are using lower-grade variations of any of those metals...

Also, it can be argued that long-term gear life may be less desirable than ultimate gear tooth shear strength for use in a crawler.

Servo gears do not endlessly spin full revolutions while meshed, but instead make small corrections while being subjected to resistance and impacts.

(As far as the need for one non-metallic gear, back some 10 years ago it was stated by Hitec somewhere that metal gear servos must have at least one plastic gear to avoid RF feedback from the gears to the pot that would cause glitching - not sure if that has been avoided with any other modern advancements? The 3BrothersRC G13 states "* All metal gears" in it's specs, for example...)

Here's a pic of a ProModeler steel-geared servo - not sure where the non-metallic or composite gear is hiding:

I think you miss understood me, or I was too hasty in my reply and did not explain it enough. The picture you posted is most all aluminum gears with inner gears made of most likely a hardened steel. Not certain about the lower gear. You can tell by the thickness of the gearing for one, as well as the machining in the center attached gear piece. Its a different metal and has to be fixed to the aluminum gear. As for the lower gear it is usually aluminum or composite. These are general statements. I have seen brass gears, composite, etc... This also depends on what the pinion gear of the motor is made of. A lot of servos use brass, among other metals for the pinion. Brass typically is the standard but not always. Point being. From my experience the aluminum gears generally outlast the hardened steel gears at the point of failure. Not always, but much of the time.

 

[holycaveman]

I'm curious as to why with regards to both of your statements. I don't doubt that a properly coated aluminum gear has a higher Rockwell hardness on the surface than non-hardened steel, but I have a very hard time believing that the sheer strength of each tooth is anywhere near as high as the steel gear teeth.

Why can't the lower gear be steel?

Because of the fact that the surface area is always a lot larger than that of a hardened steel gear. Again this is my experience with steel vs aluminum gears. Both can fail. But generally I see more steel gears failing. And this is all dependent on the area that is steel vs aluminum, as in what part of the gear. Keep in mind a hard impact can destroy any gear at any time. I hear people all the time afraid or mislead to believe aluminum gears are bad. When actually they can be very strong and in many cases better than steel. So in other words I advise going on actual feedback on A particular servo rather than trying to determine for oneself what gears are more durable. You may be very surprised.
.

 

[Frank211]

Review/test vid on the 3 amigos servo https://youtu.be/RVXoYHj4bx0

 

[Rekreant]

Review/test vid on the 3 amigos servo https://youtu.be/RVXoYHj4bx0

I was disappointed that it didnt perform up to specs.

 

[holycaveman]

I was disappointed that it didnt perform up to specs.

Actually we thought it overpreformed. And are very happy with the review.

 

[mikemcE]

I was disappointed that it didnt perform up to specs.

Explain as the fanboys don’t or can’t


Hang up and Drive

 

[mikemcE]

Actually we thought it overpreformed. And are very happy with the review.

Well there yours, I would be shocked if you panned your own product


Hang up and Drive

 

[holycaveman]

Well there yours, I would be shocked if you panned your own product


Hang up and Drive

Well if the video showed our servos underperforming we would not be sharing it everywhere! LOL

 

[Rekreant]

It was ~20oz/in under at every rating though....

 

[Rekreant]

Also, how has a 110$ servo become the topic of discussion in a cheap servo thread?

 

[holycaveman]

It was ~20oz/in under at every rating though....

Our servos are advertised "dynamic" torque. Not static torque from a fish scale. As was pointed out in the video. I am very surprised they were that high on pure static. Definitely something to be excited about.

 

[TheLetterJ]

...because it's the same as one of the cheap servos in this thread?





:lmao:

 

[Rekreant]

Yeah just like with C ratings I wish servo manufacturers would use realistic stats so we can actually understand what the heck they are actually selling instead of being mislead to believe something is better than it actually is. First world problems I guess.