Gear problems

[Andro]

Hi there

I started building my 42070 6x6 Tow Truck A Model. This time I wanted to try to lubricate all the moving parts and pay more attention to the friction. It's a slower process but axles and gears move apparently better. My concern is with DOUBLE CONICAL WHEEL Z20 1M (https://brickset.com/parts/design-32269). Its teeth are touching the beam to which it is mounted and there is a lot of friction there and noise. So I decided to add a flat washer and it makes a big difference. First I made a washer out of thin plastic to test the idea and then I just bought thin (0.1 mm) washers to work with.

The other problem with those gears is that in this part of the gear box they are too close to each other and they are teeth are touching each other. The gear is added on page 38 in the instruction. I tried it without the washers or with more washers on different sides and the problem stays. If I don't put washers and press the gears to the beams firmly they don't touch each other but they touch the beams. At the end after a lot of thoughts I sacrificed one of them and cut the teeth a little bit. You can see it in the second picture. I have never done such things before and it was a very tough decision. So now its working without awful noises.

So what do you think of all that?

[Jurss]

If You put on both gears washers on beam sides, then those gears get closer together, and then they start to grind. 

Never built this set, so I don't know, how it is without all this. Need to check parts availabilit in collection and build.

[allanp]

I have noticed that the 20t double bevel gear sometimes seems to be troublesome in this regard, like maybe there are mould imperfections on one face causing some grinding. 

[Andman]

Might be the like explained here in this thread. I contacted TLG and got replacement for alle affected gears.

[suffocation]

I've run into the same issue, too. Like Allanp said, some of those gears seem to have come out wrong. No biggie if you've got a decent stock of them but still a pain in the backside.

[Andro]

Thanks guys for the idea. I will try to get replacements too. Though it's kind of fun to use washers in LEGO. Makes it more real. :)

[sirslayer]

Instead of grinding your Legos, have you tried the black colored 20t gears??  they are a bit thinner and can be used in the placed of the tans color gear !!!!

sirslayer lego technic by Victor Mendoza Jr, on Flickr

 

[Andro]

I'm not going to disassemble the model right now to  reach those gears but I experimented a little bit with other 20t gears. All tans grind the same way, black ones are so-so and the grey ones are almost perfect. I contacted Lego and am waiting for a response on this one. I'll keep you posted.

[Maaboo the Witch]

Black 20ts seem to be softer and smoother than the tan versions. I'm guessing they come off a different production line; maybe TLG should check on it.

Not that they will. 

[Jundis]

Overall I don't like these 20t bevel gears as they always seem to grind... the problem I think are the flanks of the teeth, as they are sticking out the same height as the outermost ring. While normally when you work with a little space to allow friction-free rotation of the axles, the axle/gears bend slightly to one side under load. Therefore the gears grind on the liftarm/frame/technic brick. In contrast, that never happened on the straight toothed 16t or 24t. 

Edited December 9, 2019 by Jundis

[Maaboo the Witch]

31 minutes ago, Jundis said:

Overall I don't like these 20t bevel gears as they always seem to grind... the problem I think are the flanks of the teeth, as they are sticking out the same height as the outermost ring. While normally when you work with a little space to allow friction-free rotation of the axles, the axle/gears bend slightly to one side under load. Therefore the gears grind on the liftarm/frame/technic brick. In contrast, that newer happened on the straight toothed 16t or 24t. 

Preach it. It's very noticeable in 42049 and 42054.

[Gray Gear]

I had the same problem with two of these gears locking like this in a prototype Gearbox for one of my MOCs. In my case there was a little space, and the one Gear could scoot over a little in the territory of the other. I ended up abandoning the prototype.

[Maaboo the Witch]

Also 42070.

[Andro]

25 minutes ago, Gray Gear said:

I had the same problem with two of these gears locking like this in a prototype Gearbox for one of my MOCs. In my case there was a little space, and the one Gear could scoot over a little in the territory of the other. I ended up abandoning the prototype.

Sorry to hear that. It wasn't an easy decision for me to cut it but now it works like charm (with a washer on the side of the beam). Now that I definitely know that these gears are problematic maybe I won't think twice to cut another one if needed. Another idea is to reshape one a little bit on the lathe. :)

[Jundis]

Just now, Andro said:

Another idea is to reshape one a little bit on the lathe. :)

Or maybe just use sandpaper/grinding wheel on the edges of the teeth?

[Gray Gear]

Just now, Andro said:

Another idea is to reshape one a little bit on the lathe. :)

I wish I had awesome tools like that at my disposal...At least I will have a 3D Printer at home soon. Hopefully this B*tch can print some rims in 1:8 scale.I am Tired of the Porsche rims, I want some sick 5spokes 

But probably not, I Imagine tolerances must be pretty accurate...

[Maaboo the Witch]

Parts shouldn't require modification with outside materials. They should work as intended.

[Gray Gear]

6 minutes ago, Maaboo35 said:

Parts shouldn't require modification with outside materials. They should work as intended.

Agreed. I dont modify bricks, I did it once and now I cringe everytime I see that cut piece 

[Andro]

Lego replied to my mail today. They didn't said anything specific on the topic. They said "sorry" and "we are sending you new gears". Right now the model is working great with some washers here ant there, some black gears in specific places and lubricated.