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STEEL CRAWLER
About this creation


Okay, so I’m gonna do this one a little different then past posts. I know people like the meat and potatoes first (in this case, videos and pics). I will say, however, that this is NOT simply a redo of this crawler I formerly posted. Read on for the details (dessert; if you want to stay true to the analogy), I really think it will be worth your while. Hopefully there is some good educational tips for folks if they are choosing to build strong with Lego Technic.

















Okay…. So where do I start? First, many comment that Lego PF motors are too weak. I kinda disagree. Too slow perhaps, but not too weak. I think there are other, larger problems at play. Like the connections in Lego Technic (if not the elements themselves). In my experience, the connections Lego Technic creates are much weaker than the motors. Consider the following short video:



In this short video, where my original crawler, without the changes seen below, is in action. The limits of its climbing skills were not imposed because of lack of power, but because the Technic connections kept busting apart. The XL PF motors were literally ripping the model apart.













So…. To make this thing a better crawler the connections had to be stronger. Here was a little inspiration for me. Although revamping the whole Lego system was obviously not my goal, the idea in the Minds-I system is pretty clever:



There are many ways to make Technic connections stronger. First, the legal. In doing this project I realized that there are actually different molds of the same pins (BL part number 2780). To be clear, this really is the same part. Technic pins have evolved over the years and essentially there are three different kinds of black, 2L friction pins. The “no slot” version from the 80’s and early 90’s (BL part number 4459), and then the first (mid-to-late 90’s) and second generation (2000’s) slotted pins (BL part number 2780). To prove the same pins are actually different in thickness here are some pictures:










As you can see, these pins are quite different in terms of their thickness, with the first generation being lots stronger. As a side note; many complain that Lego is using less and less plastic in their molds as a means to cut costs. Although there is much less plastic used in the molds for the second generation, there are alternative explanations as to why. A brief discussion on this topic can be found here , but quickly the first generation pins were so darn hard that separating bricks was near impossible, and TLG received many complaints. This could be a possible other reason why TLG changed the molds, not necessarily as a means to save cost.

Now, if one could build with nothing but these pins…. then obviously their build would be stronger. I tried to amass as many as I could, and I rebuilt the entire original version of this crawler with the stronger pins, except in places where I use other methods to strengthen connections (discussed below). This was no small task; as BL does not differentiate between the two. I had to pour over all my collection to find enough of the thicker pins. I even posted on BL if anyone wanted to sell me a bulk lot of these pins….. but I found no takers. I don’t think it is worth anyone’s while to pour through their inventory to find such pins. To do so I would have to make it worth their while, thus likely making them very expensive.

Another legal way to strengthen Technic connections is fairly well-known. Simply drive bar elements through liftarms and pins (although with the first generation slotted pins you can’t do this; they are roughly the same thickness as blue 3L pins). There are several different options of bar elements to use; just use what best fits your purpose. The first pic involved cutting a ½ pin with bar extension and then spreading the ends apart before it is inserted into the pin (getting a 2L pin is actually tricky, and involves an illegal method). For other lengths, there are several bars to choose from.





Now, for a few illegal methods. First, and probably my favorite, is to use #6 machine or regular screws (3/8 or about 9.5 mm) and screw them right into the pin that holds a certain connection. Like this:







This is really the same concept as the Minds-i system, without the 600 dollar price tag.




Another method is one that I found at a local hobby store. The second generation black pins have a certain thickness that rods of a certain diameter can fit through. That’s the whole idea behind the legal method explained above with placing Lego bar elements through the center. Well, I found aluminum rods that can be cut and fit through black pins just as well. As with the legal method using the Lego bar elements, this does two things: (1) it makes it so the black pin will not bend while inside of a liftarm (which, I know it seems that it can’t because it is such a tight fit, but believe me, under enough stress, it will, that is why they pop out. If you are up for a test, test it yourself. Connect two liftarms with a black pin, give it a little twist and it will come right apart, just as easy as if you were to pull the liftarms in opposite directions) and (2) it spreads the Lego pin just a little further out, making the fit inside the liftarm a little tighter.





Armed with these methods, the connections in Lego Technic can be made so much stronger, which is the differences you see in the videos above (main video and blooper video). I didn’t do anything to the Lego motors. They are stock, as is the IR receiver (although I did use the V2 version) and battery pack. It is the stronger connections, not more power or more RPMs, that enhanced the climbing power of the model because the power from the motors could be more directly applied to wheels and not into disintegrating the model. I added the blooper reel not just because it is funny, but it is educational too. In all the falls the crawler took, not once did things break. The roll cage around the vehicle (which is nothing but standard axles and connectors) did separate a little, but the roll cage did not employ any of the techniques described above. The chassis and rest of the main body took no casualties. I did have one problem with the driveline, at minute 2:35 in the first video, where I busted a U-joint, which is pretty cool because it still made the climb (no, no….I did NOT add a differential in my crawler).

Okay, other changes to the model were the tires. I have used these babies before with much success:



And wanted to apply them to my crawler. However, they are extremely heavy to use for tires on a Lego model. 175 grams to be exact. Each tire. 700 grams for all four. In fact, the tires and rest of the model, chassis, motors, even battery pack are nearly the same weight, 700 grams to 800…… so, these tires really are beasts. Still, they offer monster ground clearance, are super soft, and practically mold themselves to the rocks they are up against.

Lastly, due to the extreme weight of the tires, and the tremendous backlash from Lego axles, I decided to go with stainless steel axles instead for the crawler’s axles, but not drivetrain.




It added a bit of weight, but got rid of the backlash. In addition, for crawlers, it is incredibly important for them to stand still when needed; they can’t roll down hill when you are stopped on an incline. In real crawlers, brakes provide this function. However, in my build I don’t have brakes because they are not needed. The PF XL motors provide plenty of resistance to disallow the vehicle from moving when not wanted. But, plastic axles don’t stop the vehicle nearly as well as stainless steel ones. The stopping power is highlighted in the videos.

Thanks for looking..... hope you enjoyed the pics, vids, and the read. Please remember to rate and comment!



Comments

 I like it 
  December 14, 2015
Well, you say Function over form, but this has both - it looks like a traditional off roader, and works like one too! Awesome work!
 I made it 
  December 1, 2015
Quoting White Shapes Fully agree with all the remarks above (I've just finished a similar crawler with the same chassis issues). From a slightly different standpoint, we must remember that we are using stuff originally designed for kids, for the best and the worst. The magic of these parts is that they can be used by kids just like older guys like us. Should these parts be more accurate, stronger, etc..., they would sure match our adults requirements, but would it still be Lego??? Maybe TLG should create AFOL-dedicated parts: we could call it Meccano :)
Very good points and I agree 100%. I have put forth this very point several times in discussions on eurobricks. I have not thought about more adult-type bricks however. This is an interesting idea. That would be great if TLG would adopt it.
 I like it 
  December 1, 2015
This performs really well; while PF motors were designed to perform in Technic sets, they can do so much more!
 I like it 
  November 30, 2015
Very impressive technique
 I like it 
  November 29, 2015
Fully agree with all the remarks above (I've just finished a similar crawler with the same chassis issues). From a slightly different standpoint, we must remember that we are using stuff originally designed for kids, for the best and the worst. The magic of these parts is that they can be used by kids just like older guys like us. Should these parts be more accurate, stronger, etc..., they would sure match our adults requirements, but would it still be Lego??? Maybe TLG should create AFOL-dedicated parts: we could call it Meccano :)
 I made it 
  November 28, 2015
Quoting jds 7777 Awesome! I don't mind the use of illegal mods for Lego in cases like this. Where did you get the stainless steel axle?
Thanks for the feedback..... the stainless steel axles are available from a little store on Bricklink called "brick machine shop" -- in California. I have used them with several of other projects I have been involved in with great results.
 I made it 
  November 28, 2015
Quoting Gabor Pauler You corrected basic structural weakness of Technic, hehe... Cool!
Yea... thanks. I really am torn between old and new technic. Old technic is so much stronger..... but less versatile, but newer has the versatility minus the strength. Its a trade off between the two.
 I made it 
  November 28, 2015
Quoting Jeremy McCreary Impressive performance from the crawler and excellent discussion of strengthening methods, NFP! Glad you pointed out the connection between power losses and unwanted motions of various kinds, because I see a lot of Technic MOCs with little to no attention paid to it. Every vibration or deformation of a chassis, axle support, or axle represents a loss of power that could have gone into whatever the MOC was intended to do.
Thanks Jeremy. Yea.... I agree, its an easy and commonly over-looked item when building with Technic. But so important!
 I like it 
  November 28, 2015
Good model & nice breakdown of techniques!
 I like it 
  November 28, 2015
Impressive performance from the crawler and excellent discussion of strengthening methods, NFP! Glad you pointed out the connection between power losses and unwanted motions of various kinds, because I see a lot of Technic MOCs with little to no attention paid to it. Every vibration or deformation of a chassis, axle support, or axle represents a loss of power that could have gone into whatever the MOC was intended to do.
Nirds forprez
 I like it 
Kain .
  November 27, 2015
Very nice
 I like it 
  November 27, 2015
Awesome! I don't mind the use of illegal mods for Lego in cases like this. Where did you get the stainless steel axle?
  November 27, 2015
You corrected basic structural weakness of Technic, hehe... Cool!
 
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