Why do Power Functions motors need internal gearing

[DrJB]

I'll add my 0.02 ... Fast motors (non-geared) would cause premature wear of the technic parts. The plastics used for regular technic vs. those used for internal gears are very different. Internal gears (those in PF motors) are made of a plastic that's more resistant to heat and wear. If you look at your lego sets that use the old 9V motors, I'm sure you'd see some whitish powder, resulting from the friction between axles and brick holes.

[allanp]

Not really noticed it in an official set to use ungeared motors, the one time I do remember seeing some white dust in an official set was on the the two 24t gears on the unimog which uses a geared motor. To be fair tho I never kept my models built for that long.

Edited September 23, 2013 by allanp

[Junpei]

Ah yes, the two 24t gears powering the pump. I don't own a mog myself but I have heard many complaints about their teeth being ground up. Nothing to do with ungeared motors tho. I will probably be ordering one or two of them to do some tests.

[LiamM32]

Why couldn't lego do a modular planitary gear set...

somethin like this could work. right? Have a way to connect 0 to 6 or more. Also have it so it could be stand alone as well. Like the motor has 1 set on it and 1 at the wheel.

Just 2 days ago at my school in a Technology class, I got the very kit in this image and built it with another student. The orange lairs of planetary gears had a 4:1 ratio, and the nougat lairs were 5:1, multiplying to 400:1 when the 4 lairs in the kit were stacked. The gears appeared to be nylon. I suppose that an idea similar to this could work with Lego.

I don't think the 3-pin arrangement will work very well, I was thinking the old gear block, but with pinholes arranged like on the front of the l-motor on both sides. That also means that you can keep the studs and anti-studs for system and train builds.

Similar to my suggestion. I think that any pinholes on the front/rear should be 0.5L to save interior space, or even have male pin connections on one side. The studs also helpful for multi-use.

I'll add my 0.02 ... Fast motors (non-geared) would cause premature wear of the technic parts. The plastics used for regular technic vs. those used for internal gears are very different. Internal gears (those in PF motors) are made of a plastic that's more resistant to heat and wear. If you look at your lego sets that use the old 9V motors, I'm sure you'd see some whitish powder, resulting from the friction between axles and brick holes.

In the first page of this topic, Blakbird identified the plastic used for the internal gearing as nylon. Then we came up with the idea of new nylon gear pieces to replace the ABS gears currently in production. I also suggested that if nylon has issues with fragility, then they could make gears with an alloy of nylon and a bit of ABS. Nylon has low friction in most circumstances (being helpful for gear-teeth), but it gets much-higher with high-pressure (letting it grip the axle), as I observed myself with element 46217c01. This would partially solve the problem.

However, the problem that you mentioned with ungeared motors has changed my stance on internal gearing in motors; If the PF motors get successors, then I would like them to have one lair of planetary gears instead of two. It should be down-geared enough to be easy on the parts, but not too much more than that. It should also have a Transparent PC window at the front to see the gear action inside.

A little thing to add to the idea of nylon gear pieces: One very good one would be the internal gear on the turntable, like the successor piece of element 48452. This would be good because when I used it to make a planetary gear set with 3x 8-tooth gears, it had so-much friction that it could-not even spin when I input through the 8-tooth sun gear. Switching it to nylon or nylon/ABS would also reduce the friction in the turntables own bearing. The should also take the mold opportunity to make the teeth shorter on that piece (further reducing friction), and make it clip-into 48168 rather than being in a preassembly.

[DrJB]

Then we came up with the idea of new nylon gear pieces to replace the ABS gears currently in production.

You may have noticed that the OLD gears 3647, 4019, 3648, 3649 are made of ABS whereas the NEW gears 32270, 32269, 32498 are made of nylon. While Nylon has lower friction, it does have lower grip as well (new gears slide easily on axles). The friction wear I was referring to in my post is not that between gears, but that between axles (on which gears are attached) and whatever parts (beam, liftarms, connectors) the axles go through. Lastly, I think I know why the new gears have low grip on axles: axle holes on ABS gears are 'tighter' than on nylon. This is done for a very simple reason: ABS is harder than nylon, and thus less prone to plastic/permanent deformation. If nylon gears were made with tight axleholes, they may/will take a permanent deformation and lose such tightness/grip quickly.

Just 2 days ago at my school in a Technology class, I got the very kit in this image and built it with another student. The orange lairs of planetary gears had a 4:1 ratio, and the nougat lairs were 5:1, multiplying to 400:1 when the 4 lairs in the kit were stacked. The gears appeared to be nylon. I suppose that an idea similar to this could work with Lego.

That school set looks promising. Do you have any info on where I can order one? Edited September 26, 2013 by DrJB

[Boxerlego]

I just got a Motor that does not need to be geared down to handle the load of Lego. :D

[Blakbird]

You may have noticed that the OLD gears 3647, 4019, 3648, 3649 are made of ABS whereas the NEW gears 32270, 32269, 32498 are made of nylon.

???? Where did you get that idea? I don't think there are any LEGO parts made of nylon other than the planetary sets internal to the PF motors.

[DrJB]

???? Where did you get that idea? I don't think there are any LEGO parts made of nylon other than the planetary sets internal to the PF motors.

I'll rephrase: The NEW gears are made of a DIFFERENT plastic than the OLD gears. I have not done a chemical analysis but it does 'feel' like colored nylon!

I'm using 'pointers' such as plastic friction, noise, and local 'hardness'. Would you at least agree to that ?

Edited September 26, 2013 by DrJB

[Junpei]

Geez, calm down DrJB... I don't think the fact that the DB gears have less friction has to do with the plastic. I have built a gearbox that had sliding 20t gears because of decreased friction on the axles, I think it is so it is easier for kids to pull off the axles. I know it's different than what you're talking about, but I have one of the older 24t gears (with the 3 axle holders) permanently stuck to an axle, and I'm pretty sure it just has to do with the mold. I will note that the DB gears feel different, though, but not like nylon.

[DrJB]

Oh I'm calm ... .. and enjoying a mint tea. I worked for a very long time for a German company, and tend to use exclamation points 'easily'. But seriously though. if you take a bunch of old gears, put them in a plastic bag and shake them, you hear the 'classical/distinctive' lego sound. If however you do the same with the DB gears, the sound is way different. Another indication the DB gears plastic is NOT ABS, but something close to Nylon.

Edited September 27, 2013 by DrJB

[Blakbird]

Many Technic parts use different plastic formulations than System parts. For example, thin liftarms are obviously stiffer and more brittle material than thick liftarms. I've heard Technic bricks are also stronger material than regular bricks to make up for the lost material due to the holes. As for the gears you referenced, I can't say for certain from which of the many plastics those are made, but the changes in friction and operating sound could as easily be from differences in tooth profile (double bevel) as material. Likewise the sound when piled in a bin is related to the overall stiffness of the part as well as the material. The double bevel gears tend to have more open space than the older gears and would therefore be expected to sound different. Due to its relative softness, Nylon gears tend to be totally solid with no open areas since that would result in unacceptable strain. This leads me to believe that the double bevel gears are not Nylon. All this conjecture is hardly definitive though. Anyone have a mass spectrometer?

[DrJB]

Many Technic parts use different plastic formulations than System parts. For example, thin liftarms are obviously stiffer and more brittle material than thick liftarms. I've heard Technic bricks are also stronger material than regular bricks to make up for the lost material due to the holes. As for the gears you referenced, I can't say for certain from which of the many plastics those are made, but the changes in friction and operating sound could as easily be from differences in tooth profile (double bevel) as material. Likewise the sound when piled in a bin is related to the overall stiffness of the part as well as the material. The double bevel gears tend to have more open space than the older gears and would therefore be expected to sound different. Due to its relative softness, Nylon gears tend to be totally solid with no open areas since that would result in unacceptable strain. This leads me to believe that the double bevel gears are not Nylon. All this conjecture is hardly definitive though. Anyone have a mass spectrometer?

While I agree with most points above, I stand by my noise-based explanation. While I agree noise is the result of a multitude of factors, the dominant one in this case is not shape, but hardness of the plastic material. One more 'clue' is that DB gears can be easily cut with an X-Acto knife. Such is not the case for the old gears. Anyone willing to sacrifice a DB gear? DB=Double-Bevel Edited September 26, 2013 by DrJB

[Junpei]

Yeah, I've got tons of them. What experiment do you propose to do with the DB gears?

[DrJB]

Yeah, I've got tons of them. What experiment do you propose to do with the DB gears?

Was not a serious request. Just trying to 'prove' that DB gears are made of a softer plastic than old gears ... I think if you'd take an X-acto knife, you could easily cut a DB gear but not the 'old' gears ... This 'debate' has gone on for too long, might be a good idea to stop it here. One thing for sure, most engineers tend to believe 'passionately' in their own ideas ... it's how we're wired. No need to harm an innocent lego gear though, Cheers!

Edited September 27, 2013 by DrJB

[LiamM32]

You may have noticed that the OLD gears 3647, 4019, 3648, 3649 are made of ABS whereas the NEW gears 32270, 32269, 32498 are made of nylon. While Nylon has lower friction, it does have lower grip as well (new gears slide easily on axles). The friction wear I was referring to in my post is not that between gears, but that between axles (on which gears are attached) and whatever parts (beam, liftarms, connectors) the axles go through. Lastly, I think I know why the new gears have low grip on axles: axle holes on ABS gears are 'tighter' than on nylon. This is done for a very simple reason: ABS is harder than nylon, and thus less prone to plastic/permanent deformation. If nylon gears were made with tight axleholes, they may/will take a permanent deformation and lose such tightness/grip quickly.

That's an interesting suggestion, even if I don't (fully) agree with it. To test that hypothesis, I lined up elements 3647 (8-tooth spur), 3648 (24-tooth spur), 32270 (12-tooth dbevel), and 46217c01 (preassembled gearbox). I then pulled an axle in and out of each one, and the most distinct feeling was the bevel gearbox 46217c01 which is the only one that is almost-certainly made of nylon, while the rest felt quite similar.

It looks like a debate has broken about regarding the plastic used in double-bevel gears. Of those 2 options, I would say ABS. But there is a possibility that both are partially correct. Let's look back at one of my previous posts on this topic:

Hmm. The ease to puncture nylon could be a problem blocking it from Lego's quality standards. That is unfortunate, because just about every other property of nylon is about perfect.

Could it be mixed with a small amount of ABS to be made stronger (without raising costs too-much)? Are there higher grades of nylon that are more durable?

I have some more reading to do.

Edit: I found something about mixing nylon with ABS. The article is a decade old. http://www.ptonline....obile-interiors

So there is a possibility that these gears use an alloy of ABS and Nylon. However, that news article about the discovery of Nylon/ABS alloy was 2003, while Lego double-bevel gears arrived in 1999; making it unlikely. It is a slight possibility that they are mixed, but I personally believe that they are just a slightly-tweaked ABS recipe.

I suggested earlier that new Technic gears could be a Nylon/ABS alloy, if pure nylon is too fragile. I suggested that the first wave should be the spur gears. If the double-bevel gears are already nylon/ABS, then they could easily just change the balance without needing to change the ID.

[allanp]

Non of the gears are nylon, I don't even think the gears inside the motors are nylon, to me it all seems like many different grades or types of ABS. The older gears were harder but more brittle ABS which is what gives you that classic sound. They held their shapes more rigidly which helped to make them harder to slide on axles but also more prone to cracking. The newer gears are softer ABS so you should hear a duller and quieter sound to them.