Anyone having problems with tan bevel gear in recent sets?

[amorti]

On 10/9/2019 at 6:54 AM, weavil said:

I took a few pics of a couple12 tooth bevel gears I had. The old one is on the left and the newer is on the right.

 

The left is darker ...

For me this first picture shows not that the older gear is a lighter colour, but that there's more material in there and the light couldn't penetrate. Which matches the second image because you can see the centre of the gear is recessed just a little.

This explains why I have two pairs of these gears in the rear axles of Didumos's Greyhound, which have become loose on their 5.5 axles.

Worth noting the gears are pretty much at the edge of their capability in this application, being driven 1:1 by a buwizz powered L motor each.

I haven't taken it apart yet to check if the axle is wearing/compressing or the gear is wearing/stretching, but a reduced contact area between the two pieces would be a cause either way.

Has anyone got busy with a cleaver, and cut a 12 tooth double bevel gear in half? If so was it stronger?

[syclone]

Well, not a cleaver, but new new 12T half-width gear seems to be made from a softer material, as I could score it quite deep with a fingernail. (the older one also gets scored, but much less, new one is veeery soft). The "antique"? grey gears I wasn't able to create visible scratches with nails, as they are made from much harder and therefore brittle material. 

So we went from brittle gears to very soft gears. This would explain why I started getting "chewed up" gears instead of broken ones. 

[Zerobricks]

I noticed the same behaviour. I think it's safer for gears to be chewed up than to fragment and fly away.

[Gray Gear]

13 minutes ago, Zerobricks said:

I noticed the same behaviour. I think it's safer for gears to be chewed up than to fragment and fly away.

In a motorized model that might be good thing, but In a manual model with almost no friction i would rather have hard gears, because I can be sure they won't wear over time. There is no chance of them breaking anyways. I recently bought used old lbg gears on purpose, they feel much more solid and run way smoother than my also used tan ones. And without color vomit everything looks way better anyways 

Edited April 23, 2020 by Gray Gear

[Polarlicht]

Looks like i ran into the same issue with the 42115 Sian :(

[howitzer]

(Copied from the Sian topic.)

If the 20t gears are too thick, wouldn't it be quite easy to thin them a little bit by sanding couple of tenths of mm off on both sides? Not that I have personally noticed problems but this is something I might do such a problem with them ever comes up...

I took a measurement of random 10 random 20t gears with a vernier caliper, and all were between 7,92 and 7,95mm. All have been also bought with fairly recent sets, most from 2016 and 2018 and maybe few from 2013 so at least for me the thickness isn't a problem. Maybe there are different batches made with different moulds, and some moulds for some reason produce slightly too thick gears? But I don't think it concerns all recent gears of this type.

[pleegwat]

I do think they're having mould problems, or moulds are wearing over time and they're using them too long. I've had trouble with the 90° rotated pin-and-axle-holes piece as well for some sets from this year, where axles won't go through the axle hole all the way the first time without some effort.

[Maaboo the Witch]

12 hours ago, pleegwat said:

I do think they're having mould problems, or moulds are wearing over time and they're using them too long. I've had trouble with the 90° rotated pin-and-axle-holes piece as well for some sets from this year, where axles won't go through the axle hole all the way the first time without some effort.

What part is that?

[pleegwat]

TLG numbers it 6261375

[Polarlicht]

20 hours ago, howitzer said:

(Copied from the Sian topic.)

If the 20t gears are too thick, wouldn't it be quite easy to thin them a little bit by sanding couple of tenths of mm off on both sides? Not that I have personally noticed problems but this is something I might do such a problem with them ever comes up...

I took a measurement of random 10 random 20t gears with a vernier caliper, and all were between 7,92 and 7,95mm. All have been also bought with fairly recent sets, most from 2016 and 2018 and maybe few from 2013 so at least for me the thickness isn't a problem. Maybe there are different batches made with different moulds, and some moulds for some reason produce slightly too thick gears? But I don't think it concerns all recent gears of this type.

Same with Panel #21 in the 42115, some are lime and some are a little darker, so they come from different machines, same could be with that gear!

[iLego]

On 10/7/2019 at 12:15 AM, Rudivdk said:

I had this issue VERY noticeably in the 42075 Fist Responder set where I just could not get the engine running smoothly. It made a hell of a rattling noise and the vehicle wasn't able to roll on after being pushed, just too much friction. Tracked it down to the tan bevel gears (more precise, the straight mesh between a 20t and a 12t bevel gear) in the driveline.

Interestingly, I hit the same problem with 42075 when I built it the second time. First time it ran fine ! So it looks like the three 20 tooth double bevel included in the set are also not identical.

This problem is very severe in my case to the point that the rear wheels will sometimes slip when the vehicle is pushed forward. It looks like the the teeth of the 12t and 20t are clawing into each other and getting stuck. The effect is the same when I take out the problematic combo and put them in a well braced drivetrain.

Some of the earlier posts recommend contacting Lego support. Are they willingly sending replacements ? Are the replacements better ?

Also, I have a few other unopened sets from the same time period. Will it be ok if I contact Lego as and when I open them, or should I contact once with all problematic parts I find ?

[Andman]

15 hours ago, iLego said:

Some of the earlier posts recommend contacting Lego support. Are they willingly sending replacements ? Are the replacements better ? 

They are likely willing to replace them. But there is no guarantee that the new gears will be better. In my case they were slightly better.

15 hours ago, iLego said:

Also, I have a few other unopened sets from the same time period. Will it be ok if I contact Lego as and when I open them, or should I contact once with all problematic parts I find ?

It's perfectly fine to contact them. They may ask you to send them some kind of batch number or quality code (don't remember name), which is located on the box. I assume to trace where the parts in question were produced.

Edited July 2, 2020 by Andman
typo

[iLego]

@Andman thank you for the reply.

[Zerobricks]

Might be a bump, but I was just watching Behind the scenes of how TLG motorized the 1:1 scale Chiron:

The way the mated the gears are 24 to 20, on a 3x3 L layout is not a really a very "legal" gearing, since the gears are in a looser mesh than the usual (you can see the updated 20 tooth gear around 3:30 in video).

Also in the original set, there is an exact situation with the gear shifter, but in that case there is a beam right next to it. I think at that time the 24 tooth gears have been updated so they don't rub agaisnt it.

So now we have a situation where we have a slightly smaller 24 tooth gear and we are trying to mate it to a 20 tooth gear for both the set and the 1:1 project. Do you see where this is going?

I'm thinking these two projects might have contributed to the decision to modify the 20 tooth gears but in the process they broke the main meshing fit.

What do you think about my theory?

 

 

[Andman]

Hi,

I bought the 42100 recently and discovered an issue, which is new to me. Not sure if that was already discussed. Step 525 lets you connect a 20t with a 12t bevel gear. It runs far from smooth. So I took couple of older 20t gear (not sure how to differentiate newer ones from older ones). With the older gears the new 12t gear runs perfectly smooth, even if I use some more force to push them together. The opposite case happens when I press the new 12t and new 20t gear from the 42100 against each other. The same happens when I push the older 20t gears against the new 20t gear. Very "bumpy". When I pushed to older 20t gears against each other, they turned also very smoothly.

So my conclusion is, that the teeth of the new 20t gear are too thick. My 42099 also makes still rattling sounds. Will test if the gears show the same behaviour like they do in the 42100.

Edited November 5, 2020 by Andman
typo

[Wasdalegofan]

Hi All, I am a new member here and have joined purely because you have managed to solve an issue that has been bugging me for a few hours now. I know this is an old thread but it has helped me immensely. I have just started building the Bugatti Chiron and had got as far as the rear section and gearbox when I decided to connect a motor up to the drive train and test the gearbox. I had real problems with gears grinding in particular selections. I traced it quite easily to the 20 tooth tan gears and the 16 tooth black gears and swapped them around for others out of the same set. I rebuilt the gearbox and tried again with similar results. So i did a bit of googleing and came across this thread. It seemed to be a known problem and so I did as suggested and swapped the tan gears out from an older set. What a fantastic difference it made. I feel happy to move on with the Bugatti build now.

Again I would like to thank all involved in this solution and I will hope to make some sort of valid contribution in the future in way of repayment.

[Andman]

Welcome to the forum. Glad it worked out for you.