Caterpillator v1.1
Description
youtu.be/p8LfDx4Fps4
youtu.be/W3qBWAuP4Aw
youtu.be/Cck-VeZ_XTA
youtu.be/sWD4rVweHvo
This is the new version of the caterpillator. This version tries to overcome the problems found in version 1.0 and also it has become completely parametrizable.
More documentation of this robot can be found at mrgroup.dyndns.org/mrgroup/doku.php?id=robots:orugator:orugator_v1.1
It is especially recommended to have a look at that page in order to understand better the notation of the parameters used in the different files of openscad since it includes the drafts of the different parts.
Update
I have added the stl files that we are actually printing :) For the moment we have one wheel and some links surrounding it
thingiverse.com/derivative:9532
Update 21/5
We've started to print the robot. Here it goes a video of the links and the wheels
youtu.be/NoXAF5WsLn0
Instructions
-Open the one called Parametric_bot.1.1.scad with OpenScad
In that file you can choose which part of the robot you want to generate according to the dimensions of the wheel. Read the comments in the file to know which parameters you must introduce.
- The pack for the batteries can be found here thingiverse.com/thing:5079
-The U piece and the holder for the batteries are taken from the miniskybot chassis by Obijuan:
thingiverse.com/thing:7989
All the stl files that are uploaded correspond to the pieces that we have printed for the caterpillator that we are making.
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Hey Olalla
Have you actually printed and used the outer wheels as produced by your
parametrized bot.1.1.scad file?
It would be interesting to see a photo if you have done so. It must have taken me 8 hours last night to print 2 outer wheels which I heavily modified to have large voids in them to save plast
ic, but with 1mm solid on the outside to prevent dirt getting in. I have also added a recess for a 628ZZ bearing (for the front wheels) and a recess for a nut. Still not sure exactly how I will secure them.
They seem a little wide though. The link is a bit small in the wheel so I guess the flat par
t of each wheel should be decreased by about 1 - 1.5mm.
Once this is up and running this will be a big platform (I am planning on a chassis of 160x100mm where the drive components are inside the chassis). Getting rather excited now... but need to order some M3 studding as it is a bit hard to source
60mm M3 machine screws to hold the wheels together. Hmm.. come to think of it, it might be worth while adding recesses for the head and cap of the machine crew as well...
I don't know if you are interested in the code to add the voids to include it in your script. If not then I may post it as a de
rivative of yours...? But really you have done the heavy lifting...
Nice work though. :-D
Cheers
Hi!
(I will be only answering the parts that Avalero hasn't covered yet)
I added a little extra width in the flat part exprofesso. If you want to reduce it, go to the file parametric_wheels, and in the modules gear_wheel (line 83) and tracked_wheel (line 109) you'll find the parameter h2. In the defi
nition of that parameter you'll find that it is added tl, which is the extra width that is being added.
Also, I'm not sure why you've put the recess for the nut in the inside part of th e wheel. For me, in order to fix well the back axis, I would put that recess in the external part.
I'd love to s
ee the code, and I could include it here with the option of using the "conventional covers" or the modified ones" by you :)
Olalla is on holidays, so I'll take the freedom to answer :P she may add what she wants when she will be online
We have not yet printed them because the chain worked very good even without them. In any case, regarding the filling, in the MakerBot ThingOMatic you can put the fill parameter to 0.1, which means in only fills 10% of the volume. In that way you save plastic and time.
With regards to the code of
course we are interested.
We are currently evolving the robot. We want to reach the "minimum" size that we can print without loosing precision in the chains. And some other changes. If you want to see more updated videos visit http://www.youtube.com/user/mo... . And if you have any suggestio
ns or make any evolution of the robot let us know. You may also want to check this other robot we are designing http://www.thingiverse.com/thi... it is also a work in progress
Now: this is REALLY awesome! It turned up better than I expected! And seems quite rugged: the moment in which the robot falls in the video is great: It shows that it can survive a little drop, and opens a new idea: a robot that can drive upside down!
Congratulations for the success! 8-)
Each link of the track has a drop of hard silicone plastic, without it, it did not track well, but after adding it (it took 5 minutes with a silicon gun) as you can see on he video it works perfectly. It can even turnover when colliding with a wall. We still have to check how it works under differential driving, as sliding is required.
Like you design and project. Say, not to cause trouble but, I saw a use for something and I see a change on your design because of a Problem? You are designing sides to your tracks. Were you throwing tracks? I've seen a use for a part on thingiverse that I'm printing and trying to alter to better fit its intended use but, it would be very good as tracks. The benefit of the design is that it is deep - less likely to be thrown. And by its inherent design/nature will grip the turning wheel's gear teeth while driving and then relax as it traverses to the next gear wheel. See the picture of my printed example of Saminvents' links. See: http://www.thingiverse.com/thi...
Note that I play with the track in the picture - A LOT! It is printed and click assembled with no pins and it does not fall apart with my heavy handed playing. It could be adapted easily to your use. You may need to make the nubs a little bigger. You would not need to alter your gear wheel - I do
n't think. And you would not need to make additional parts. You may likely use less parts?
wow!! I cannot wait too see it printed and see it moving. Really awesome. Great jog!!
License
Hey Olalla
How is your caterpillar progressing?
I am progressing slowly, and have run into a problem with turning and was wondering if you encountered these issues and perhaps a solution to overcome them.
I see you used modified servo motors for drive, and perhaps the torque delivered is sufficient. In my
case I have model motors with a gearbox which then needed to transmit the drive to external axles which had the drive chain wheels attached. When instructing the robot to turn (by stopping one motor and the other in foreward) I found the friction of the catirpilar on carpet was way too high and the
gears slipped on their shafts... resulting in my vehicle not turning. You will of course not have the slipping gears issue, but I wonder if you also have the friction preventing turning on a carpet, or whether your servos deliver enough torque and are robust enough to turn your vehicle on a carpet.
Of course it is always possible I am expecting too much of my vehicle and should run it on a wooden floor or some other surface with much less friction... or alternatively drive the vehicle with servo motors such as you are.
Regards
All the team is currently on holidays, so the project is on hold till September, when all of us will be together again...
Nevermind
I purchased some TowerPro MG995 servos rated at 10kg/cm and converted them to continuous rotation. And what do you know/// my platform turns easily enough on a carpet = Wehey!! :) That made me rather happy lol. I did find the lack of traction when trying to climb a slight hill of stones so will pr
obably rubberise my tracks as mentioned by alavero, but wohoo... making progress slowly :) Sill post some photos when I can be bothered. Way too busy trying to get it all together. Now trying to get simple navigations going with a sharp distance sensor... Olalla - are you managing to give your bot s
ome intelligence?