How do I get this to work ?

[Stormbird]

Hi all

Someone is selling this on UK Ebay :-

So wanting one I built it from my parts ? however I cannot get it to work !

http://www.ebay.co.uk/itm/Lego-RACK-and-PINEON-technic-steering-gear-car-truck-robot-mindstorms-ev3-nxt-/251955388898?pt=LH_DefaultDomain_0&hash=item3aa9b621e2

If the rack is part no 64781 , the only one that is 13 long with axle and pin holes ? it is far to tight to turn the axle/gear ?

Although I only have the 'old' type 16 tooth and not the ' new ' type surely they are interchangeable ?

regards Paul

[PKW]

teorically it sohuldn't work because The 16t gear il not compatible with the new racks, But... If you move The 2m axes until their small gaps make the racks sliding on it it could work, i think the new gears are little bit smaller but I have To try when I get home

[Lego Otaku]

I tried this in LDD and according to LDD, both works. I used both older and newer style gear. I don't have the rack to actually test this though

LDD file: http://www.brickshelf.com/gallery/Lego-0taku/ldd/rack_pinion.lxf

[Jurss]

Have to try at home in the evening

[Erik Leppen]

It's an interesting setup, really. What if you'd used the old 14t gears? That might work.

[zux]

I've just build this. It works.

[bithuizev]

I used both older and newer style gear.

[PKW]

It's an interesting setup, really. What if you'd used the old 14t gears? That might work.

with the 14t gear it works perfect, as it does with the 12t one ;)

I've just build this. It works.

I used both older and newer style gear.

+1 just a little bit better with the new gear, because the diameter of an axle is obviously smaller than the height of a liftarm:

[bj51]

What 14t gear are you guys talking about ? The only 14t gear I know of is this one:

[zux]

+1 just a little bit better with the new gear, because the diameter of an axle is obviously smaller than the height of a liftarm:

That's because you assembled it a bit wrong ;) Gear rack shouldn't be raised by whole one stud, but rather slide on axles as shown on original example. This gives it more space.

[Paul Boratko]

From what I cans see, the holes don't line up exactly perfect creating a bit of friction... This is a technique that you would probably never see used by TLC..

Edited May 15, 2015 by Paul Boratko

[PKW]

From what I cans see, the holes don't line up exactly perfect creating a bit of friction... This is a technique that you would probably never see used by TLC..

yes I built it in that way To show The problem it create, it also has an enough frictioned movement

Edited May 15, 2015 by PKW

[Stormbird]

Hi all

Well I have the old style 16t and it is very tight , I think as someone earlier said the teeth profile is wrong for the rack ?

You can see here there is some light above the rack tooth , however 2 gear wheel teeth are squeezing 1 rack tooth and so it is to stiff to turn the axle.

I don't have the new style 16t to try.

I do have the new 12t double bevel gear and that only works if I add a full size bush to each lower axle and the rack then rides on the raised lips at the end of the bush as the 14t is smaller diameter than the 16t , so for me that is a possible solution with the parts I have.

thanks for helping Paul

Edited May 15, 2015 by Stormbird

[dhc6twinotter]

I think a beam should be added on the bottom and the proper 12t gear used. That's the only way LEGO would configure this.

[DrJB]

i see all these ideas/ discussions about gear tooth profile and I wonder. Most gear do have a 20 degrees angle and they all havethe same pitch/ module. Thus, I am not sure I understand/agree with those saying that the profile has changed.

If you leave all conical/ tapered gears aside, all gears made by TLG should mesh with one another, provided the distance is correct.

Anyone cares to shed more light?

[PKW]

ti problem with The combination of the 16t gear and The new racks in not The module But The height of the rack, old version has a 1/2M base height so in a 2M space (from the gear axle To the rack support) they can fit with the 16t gear. using the new ore you teorically need 2,5M space, support the rack with naked axle don't guarantee full 2,5M space so the 16t gear Point force the rack but beeing them shorter than the rack points the gear "lock" himself in the position displayed in your photo, the new 16t gear has smaller points (some decimillimeter less) enough to ran smoothly but not in a fluid way

[Stormbird]

Hi all

So trying different combinations:-

Top does not work no clearance between rack and gear - rack to high.

Bottom left does work as 12t is smaller in diameter than 16t above - however it needs bush's on the red axles to take up the slack between the gear and rack

Bottom right does work old 16t and old rack - however the old racks I have are very short and do not have the axle holes in them like the newer thicker rack.

So how is he selling the one shown on Ebay as it does not work for me.

Sariels book says there are 2 versions of the 16t page 50 fig 5-15 parts #4019 & #94925 , do they have different tooth profiles so letting the top combination work ? I don't have one so cannot try.

Where you say LDD allows this , yes it can be constructed as can be seen above however it is very tight and does not function as a rack and gear should i.e no motor can drive it easily.

regards Paul

Edited May 16, 2015 by Stormbird

[Stormbird]

Hi all

Well closure on this thread !

I have tried the new 16t and the item works as in the first picture , the teeth must be a different profile to the old 16t and so do not bind.

It was interesting that the rack was a little tighter in the middle than both ends , the rack had a slight bend in it ?

regards Paul

[DrJB]

Hi all

Well closure on this thread !

I have tried the new 16t and the item works as in the first picture , the teeth must be a different profile to the old 16t and so do not bind.

It was interesting that the rack was a little tighter in the middle than both ends , the rack had a slight bend in it ?

regards Paul

Here we go again. There is no such thing as different profile.

Edited May 19, 2015 by DrJB

[Lipko]

Here we go again. There is no such thing as different profile.

Not everyone here is an educated mechanical engineering with fresh knowledge of gears. Of course if the term is used as in engineering, the profile is not different. But if we use the everyday term, then the profile (as "shape") is different, because the height of the teeth is different.

[RohanBeckett]

interesting.. I just tried the same with both old, and new 16t gear... and they both feel exactly the same - movable.. but firm.. and not something I'd want to use anywhere...

the best one seems to be with the 12t gear, supported by the bushes.. that seemed to be spaced perfectly, and would be something that TLG might use in a set.

[Blakbird]

Not everyone here is an educated mechanical engineering with fresh knowledge of gears. Of course if the term is used as in engineering, the profile is not different. But if we use the everyday term, then the profile (as "shape") is different, because the height of the teeth is different.

As far as I know, there is no difference in the teeth of old and new 16 tooth gear.

[Lipko]

As far as I know, there is no difference in the teeth of old and new 16 tooth gear.

Oh, my bad, I didn't pay attention and the height of the gear rack teeth are not the same. Or at least that's what PKW wrote.