Tuesday, January 12, 2010

New(er) style for Wide Link Treads

The last two posts here at TBs have been about tracked excavators, therefore this is somehow still in the subject.

Months ago, someone noticed a design change in the small Technic Link Chain element most likely as a measure to reinforce this part and prevent break in service events.

A few days ago my friend Martyn, told me about a new finding from John Brost [1, 2, 3] concerned with a small redesign also to the modern Wide Link Treads (57518).
The original version have a slightly different design from the newest parts and thus LEGO should have changed the mold. This was found by John while playing with ideas to build some large wheels, using circles made of these tread links turned inside-out.
By mixing some old and new parts from different sets, suddenly some wheels became very un-wheel like. Looking to find where the problem was, John found to have two types of different tread links. The newest ones had little protrusions in the contact to the next link, that make impossible to create such circles as small as with the old style. Digging further he found also that alternating new & old style links would prevent this issue, despite not very convenient having to sort them all...
Although both types will work fine with each other, if mixed in the same track.

Because an image is worth a thousand words, below a couple of pictures with annotations from John, which better show the difference between old & new parts design.

Click to enlarge the images and better read the embedded notes.

The change should have occurred in 2009, since all my DGB and Black links stock from 2007-2008 sets (8272, 8275, 8294 and 7645) have the old style links. Just got the ones with new design, at sets 8263 and 7632 already from 2009.
Despite the mold modification, both parts exhibit a "© 2006 LEGO" mark and the same mold reference (57518).

Both John and Brian Davis at The NXT STEP, have advanced some increased side-to-side stability (lower flex) as a probable motivation for the change. However I wasn't able to observe such difference even at long track spans. Hence, apart the larger backwards radius, any other eventual reason for the change is still a mysterious.
Still the benefits at not so large spans, are not yet evident to me! And even for those (large spans) we can hardly take advantage of, once the admissible radius is still relative low.
Maybe it could help to prevent tracks to slip-off from bogie wheels, or even from breaking at extreme conditions. Don't know!


Anonymous said...

Maybe they did this to reduce the slack in some mysterious new model :)

Anonymous said...

For completeness: new editions of older sets also have the new links. I bought my 8275 in November 2009, and it has the new ones.

TechnicBRICKs said...

Yes, it makes all the sense.


Parax said...

The Lego City Bulldozer(7685) and crane(7632) from H1 2009 had the new tracks, so they have been around a while.
There was speculation that the side to side rigidity was better, but when I tested I got the same bend radius from each type, it seems it is only the back bend that has changed, perhaps its an attempt to prevent backbent wheel's as these can overstress the tread links, or an attempt to reduce sag on the top of tracks?
I have a nice MOC using the backbend technique though.

Anonymous said...

odd. when I look closely at the 8043 pic those trends look like the old style to me.

TechnicBRICKs said...


once this is CGI, it is normal that it happens. If you look carefully to the tracks, you will notice how unnatural they are layed over the bogies.

Don't think it has any relevance towards what we'll get into the final model.

Parax said...

8043 in the promo pics probably does have the old type but it'll be 'model builders stock' tracks and not the new stuff from the production store...

Anonymous said...

When I see these parts, I dream about the TLC making rubber plates to attach to the two half pin holes.

sunsky said...

I guess it is an atempt to reduce side-slip of the tread and track.
Reinforcement can be additional effect.

LuisQSM said...
This comment has been removed by the author.
TechnicBRICKs said...

Luís, sent you e-mail!

eMHa said...

After reading this today I came accross this: http://emhasblog.blogspot.com/2010/01/technic-pin-with-friction-and-slots.html
Is this an old change or a new one?

TechnicBRICKs said...

Well this is a very old modification!

Old friction pins, should have been used the last time into an official set, about 1989.

eMHa said...

No, not the old ones without slots! This is about the new ones with slot!

TechnicBRICKs said...


Older sets having the friction pin with slots, had this version with thinner hole.
This variation is not documented into BrickLink catalog.

Just taking an older set without any specific criteria, I've seen it now for instance at set 8443, from 1996.

eMHa said...

Very strange these old and new threads. My bulldozer 8275 ordered on 2009-05-02 has both, the old AND new ones! One of my sons got 7685 to christmas and this one has only new ones.

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