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First and foremost this is not my MOC.  As promised in his thread, I finally found the time to build @PTNYC’s Rocket Crawler.  Now, I don’t call it the Rocket Crawler, and made some modifications (discussed below), but other than these this  is his build.  

Also, I am creating a new thread for this and other builds as I am also building his Chili Crawler.  I did this years ago, and I loved it.  One of the more fun Lego models to drive out there.  HOwever, I took it apart; so I had to rebuild it with minimal changes.  Original video can be seen on my YT video.  

I plan on doing more videos with these two beasts and some comparisons.  At this point, I do not know which, the Rocket or the Chili crawler will be superior.  The Rocket has 2x the power, but also tons more weight as well (need to get an official weight).  It will be interesting to pit them against eachother.  My money is on the Rocket, with a longer wheelbase and likely (unconfirmed) better power-to-weight ratio.  

But as for now, here is my version of PunkNYC’s Rocket Crawler.  I call it the Bully Crawler.  This thing really is a beast.  

Really the only differences I made were to the body/appearance, the tires and hubs, and added planetary gear system inside the tire hubs.   Final gear ratio is 3:1 x 4:1 = .0833.  If we take information from philohome then the final RPM output for each axle would be approximately 31 (unloaded).  

ANother reason for this new post is that I wanted to share a few principles of rock crawling for Lego.  I know these principles from personal experience with the sport.   Not with Lego or RC Crawlers, but with rock crawling in side-by-side vehicles.  

One is the advantage of having good, strong steering.  In crawling, it is often necessary to begin at one angle, only to turn against that angle while locking your brakes so that your tires bend into the rock as you turn.  This can cause immense pressure and an exceptional power steering system is needed. In the video I am posting this can be demonstrating when at the top of the “hill” (minute 2:26) I am steering one direction that is about to steer me off the hill, but then I stop, (vehicle is locked so it doesn’t roll backwards) and then turn the other direction.  Because the vehicle is locked in place and I am bending the tire against the obstacle I am creating something like a “pinch” technique.  Not only am I increasing traction as I increase the tire’s surface area over the rock but I actually am pinching the obstacle against the front and back tires (because they are staying in place).  I tried to climb the obstacle in question multiple times without this method and I could not make it. Using this method however the crawler was able to overcome it handily.   

Another principle, at least in Lego crawlers with no brakes, is to have the drivetrain so heavily down-geared that it is near impossible to turn motors from the tires.  This serves as brakes for going down hairy slopes.  If one is not cautious about going down, with a good crawler the greater impediment may very well be going down a mountain rather than going up!  In minute 3:58 of this video one can see how well this is demonstrated.  If the gearing did not stop the vehicle, even though I was giving no power, it would have easily tumbled down my little “hill”.  In another video I did years ago with my modified Chili Crawler I had an incident where this was even better represented.  My Crawler was going down a slope (minute 2:36), and one tire even became airborne, but because of the intense resistance in the drivetrain when power was cut off it stopped dead in its tracks, stopping what would have easily been a failed attempt at de-escalating that obstacle.  Here are the two videos.  Enjoy!

 

 

 

 

Edited by Milan
Removed Bold font.

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Posted (edited)

The bold type is making my eyes water, almost as much as the crawler! Kudos to PTNYC for making this! The use of LAs for steering is very innovative and great for steering with power! 

Are there building instructions?

Edited by Scoar Sonander

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48 minutes ago, Scoar Sonander said:

The bold type is making my eyes water, almost as much as the crawler! Kudos to PTNYC for making this! The use of LAs for steering is very innovative and great for steering with power! 

Are there building instructions?

Perhaps this would help you a little bit 

 

 

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1 hour ago, Scoar Sonander said:

The bold type is making my eyes water, almost as much as the crawler! Kudos to PTNYC for making this! The use of LAs for steering is very innovative and great for steering with power! 

Are there building instructions?

Sorry for the bold type.  I typed all this up in a Google Docs document and it would not transition when I copied and pasted to the forum.....

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2 hours ago, nerdsforprez said:

Sorry for the bold type.

Changed to normal text.

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Admittedly this post did not get much traffic.  Except for complaints on the original font :laugh:  But I suppose this is what one does after leg surgery and cannot get access to his/her total parts collection for a real build.... and to keep one from going crazy from sitting/lying down.  But I can still crawl lol....

Here is another video with the Bully Crawler.  Increased the size of the "mountain" considerably.  VIdeo shows several features...... the outstanding ground clearance of this crawler, i.e. I was able to mount a GroPro underneath and keep it there for an entire climb! (3:47) and also its ability to climb a roughly 50 degree slope (2:22)... which is noteworthy when the slope is all LEGO (ABS not really ideal for climbing.  Smooth, plastic surface).  

I love this crawler.  Will be keeping it.  Can't wait for the leg to heal and to try this thing outside.  One note, and surprise actually... is how robust this thing is.  I was going to add a blooper video and show how many times I accidentally drove this off my "mountain" all with no damage.  Also, one can see that once it makes it up the climb, going down is nearly  more treacherous.  The vehicle stretches out, bending the trailing arms to their max, and they persist and remain intact every time.  Because of the extreme slope angles going down, often there is some sliding and hitting the bottom hard.  Axles never broke or failed.  Fun, great build.  

Next I will be comparing the Bully Crawler to Punk Taco NYC's Chili crawler.  Stay Tuned!!

 

 

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The agility of this crawler is insane! Also, gotta love how at one point there's so much torque that a "rock" breaks off the "mountain" :wub:

Did you notice any wear on the U-joint driving the steering actuator?

Get well soon - surgery sucks. Hope it wasn't anything serious.

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This crawler has fantastic performance. Most of @PunkTacoNYC's crawlers remind me of crawler/hill climbers like Bubba Bacon's. Those use solid axles with a linear actuator for steering. 

Good idea for making this thread, I'll be following it. Hope your surgery goes/went well. 

 

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14 hours ago, suffocation said:

The agility of this crawler is insane! Also, gotta love how at one point there's so much torque that a "rock" breaks off the "mountain" :wub:

Did you notice any wear on the U-joint driving the steering actuator?

Get well soon - surgery sucks. Hope it wasn't anything serious.

Thank you and yes! Torque is crazy on this machine.  Perhaps even more daunting was nearly at the exact same moment (2:34 - right before the rock breaks off) the back right wheel is stalled.  That wheel is powered by its own L PF motor, geared at 12:1.  THAT is a crazy amount of torque for ABS to handle and obviously it handled it just fine.  

Actually, I had no problems with the U-joint.  They did not crack, etc.  In fact, the original model used a L motor, I think a M motor works just fine.  Five L motors on one BuWizz is pretty demanding, so I thought if I could decrease that demand just a hair it might be a good thing.  Steering worked just fine - and as I mentioned before, I was fairly abusive to the steering.  Used steering into the "rocks" every time to press tires into obstacle.  

8 hours ago, BusterHaus said:

This crawler has fantastic performance. Most of @PunkTacoNYC's crawlers remind me of crawler/hill climbers like Bubba Bacon's. Those use solid axles with a linear actuator for steering. 

Good idea for making this thread, I'll be following it. Hope your surgery goes/went well. 

 

Yes! That is right! Bubba Bacon and Tim Cameron! Thanks for the comments.   

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Change is great, I haven't built this type of the crawler. Take care, get well soon.;)

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Here is the last video of the series.  The Chili vs. The Bully

Not overly scientific; the upshot here is that gearing that does not allow the vehicle to roll backwards makes all the difference. Gearing this so low that the motor would not turn while on a steep surface allows for better driving and handling. The Chili handled everything the Bully could despite much less power and a shorter wheelbase.  I did test the Chili with smaller, 1.9 RC tires and it was not even close to making it up "the obstacle" - I am not sure if this was due to the tires per se or the fact that the gearing was not sufficient to stop it from rolling backwards.  An interesting test would be to change the gearing of the whole Chili so that it was geared down sufficiently to not roll backwards but not need the planetary gears inside the hub and use the smaller tires.  But, I am afraid I won't get to that.  I am afraid this project, aside from driving outside, has exhausted itself.  

Here is an old picture of the Chili when it was actually taken outside: 

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Here is an updated photo of the Chili:

 

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The results were actually surprising to me.  I knew the Chili was lighter, and had a smaller wheelbase, and thought that would make the Chili unable to make some of the climbs the Bully did.  However, despite these shortcomings once the planetary gears were added the Chili kept up just fine.  

This will be the last video inside.  In a few months when I am healed perhaps I will try this comparison for more rigorous testing.  

 

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