I'm sure many of you have already observed the slippery effect of LEGO motorized vehicles with plastic treads while driving over smooth surfaces. If we think about official sets, this could be particularly observed with the 8275 Motorized Bulldozer and other models alike, but not limited to these.
This is a phenomenon mainly observed with the 57518 plastic treads (also released with the Bulldozer, back in 2007), but also present with older tread elements like 3873 (which however seem to use a slightly different type of plastic).
In what regards the modern tread elements, they have a two hole snap interface that seems to have been designed to allow the attachment of some kind of rubber grips or rubber pitons, to improve traction conditions on certain surfaces.
And this of course has been the idea from many, since the day we saw the new tread elements. LEGO seems to have finally heard the call (not that they have not though about this much earlier, I guess) and will be releasing these as a new element with some supplemental pack of the new LEGO MINSTORMS EV3 Education Kit (see the red pitons in the Tankbot below).
It still remains unknown whether these are made of rubber, plastic (ABS) or some other compound which could be softer than plastic, but harder than rubber.
Although I'm wondering about these and very expectant to see how they perform...
Back in 2008 I've conducted an experiment with my friend Mauricio in US (who runs the eBay store iLe9os). At the time he had found some interesting rubber grips that could be attached fairly easily to the new LEGO treads, and we ran a few tests from which I produced some videos, which were kept as private under my YouTube account until today.
Mauricio managed to find two types of grips, perfectly adequate to fit with the new 57518 treads and the older ones (3873). They were looking very promising.
We knew the larger ones had a long tip, that needed to be reduced a bit somehow (cutting them with a X-Acto was the method applied), otherwise they would gonna cause problems (as you will see in a video ahead). However the overall results with different configurations and different types of surfaces were not very exciting at the time. In general the the friction produced was too much and driving treaded vehicles on certain surfaces became quite problematic, even with fresh batteries.
Below you have the videos where you can see the results obtained. I'm sorry for them being quite long (I tend to produce them always quite longer than necessary...) but these were among the first ones produce for TBs , long ago. Hence they didn't benefit from all the lessons I've learned later on. Feel free to jump ahead if you get bored at certain parts...
In this video we see the grips with the original long tip. They obstruct the sprockets quite easily and you can see the result...
With them cut it works better, but still it seems not good enough.
These grips seem to be made of a kind of soft rubber which sticks too much on the table (almost like if they were suction cups, as friend mentioned to me...). Hence I hope LEGO to come with an harder or more effective compound.
In this video we have also seen another solution in action, using rubber bands attached to the treads (based on the anti-slip link treads idea from Mortymore [1, 2, 3], also proposed around the same time). It seems to perform a lot better.
While the results were quite bad on glass and floor with ceramic tiles, the were quite good over parket or wooden floors.
We always notice a much worse performance when trying skid steering or simple turning maneuvers. If one drives just straight, won't have that much problems with the rubber grips, rather an overall improved traction...
I can't find it documented in the videos above, but think to have tested the large grips also with an alternated or evenly configuration, without producing much better results (the alternate configuration can be seen at one of the videos below, with the smaller treads and grips).
Although I believe that some of the problems could be solved by playing with the way the grips are used. You can design many patterns: zig-zag, alternated or one tread with grips, the next without (like the LEGO ones in the picture) and so on...
And of course, the type of floor and the vehicle itself (weight, distance between tread links, etc) will play an enormous roll in the performance. I see the grips as I see LEGO itself: Experiment until you find the solution that works best for you.
Now the smaller grips. They seem to be made of a less soft rubber, but think they are not and still not the best deal.
See below how to insert them on the tread links.
And the final result with a very fast PF motorization of the old 856 Bulldozer...
As wrote above, I'm really looking forward to see how the new LEGO tread attachments will work under several conditions and use cases.