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RC tank for the maker faire

Fluburtur

Cardboard Boy
#1
I will most likely be participating at the Maker Faire Paris in november to show off my rc planes but since you cant really fly a plane in there I thought about building a tank that peoples can drive.

I looked at sever designs and decided on doing something close to the AMX-13


The oscillating turret system is interesting and it is a french tank so peoples will probably like that.
I will be building it mostly from thin plywood, cardboard and foam with 3d printed parts for the mechanical stuff.
The scale is 1/5 so that gives a 1m long hull, maybe a bit much for a first tank but I should manage. I will be powered by a pair of large 400kv motors geared down a lot to give smooth low speed driving, I alreadu ordered the parts so I will try to start building the hull soon.

I did a bit of the 3d model already.
4.jpg

I modified it to have the drive at the back instead of the front, this way it is more efficient when driving forward.
It wont be a 100% scale model, just close enough that peoples can figure out what it is but I will try to get it fairly close.

As usual I will post progress when it comes.
 

sprzout

Knower of useless information
Mentor
#3
Nice!!! Make sure you post up completed pictures; I'd love to see it.

And while you can't fly any FT planes indoors, what about making some chuck gliders, or flying a TinyWhoop/Inductrix? That's what I did last year for our big Maker Faire here in San Diego, and it was a huge success. At the very least, if you have some static displays of foamboard planes that people can learn to make, that goes a LONG way at the Maker Faires...
 

Fluburtur

Cardboard Boy
#4
I guess I could do that since it is in the main hall of the Cité des Sciences
DSC_5860.JPG
Since RC peoples are usually on the second level I will try to be there (also more space) however I dont know if peoples will like us throwing planes down the hall.
On the bottom there is often a battlebots arena or a zone for small quads however quads do not like me so I doubt I will have one, also I will go there for the RC company im creating so idk if I will have much other stuff, of course one of my goals is getting peoples in the hobby.
Anyways I dont have a laser cutter yet so I wont be able to cut a whole bunch of gliders (there will probably be peoples with lasers however so I could try to do a thing)
 

Fluburtur

Cardboard Boy
#5
Im done printing the first 20 track links.
DSC_1565.JPG
It took almost 7 hours and I estimate I will need around 90 of those for the whole tank
At least I got the tolerances right
 

Fluburtur

Cardboard Boy
#7
I put together the skeletton of the hull.
DSC_1572.JPG
DSC_1573.JPG
The surface finish is a bit rought but it will get covered by a cardboard skin so it will be fine then, but before I have to finish the tracks.
 

Fluburtur

Cardboard Boy
#8
I finished putting together one road wheel assembly
The suspension is only temporary, I need to fit the drive mechanism and tensionner and put a mockup weight in to tweak the placement.
The wheels use a airsoft gun BBs bearing, really easy to do and it works quite decently.
 

Fluburtur

Cardboard Boy
#9
I did some work and basically modelled the whole gearbox
21.jpg
6:1 reduction using a 2:1 gear then a 3:1, actually the lower one is just 1,9:1 to have an uneven amount of teeths to reduce wear.
Herringbone design to have smooth power transmission and the gears are 2cm wide so plenty of are to transmit power.

I have started printing it

Last gear is still printing, also I dont have the proper motors yet.
 

Fluburtur

Cardboard Boy
#10
I finished assembling most of the gearbox, it still lacks the bearings and it has a temporary motor which is 900kv instead of 400 but I was able to test it.

It sounds terrible because of the mostly hollow plastic gears but it actually runs quite smooth
 

Fluburtur

Cardboard Boy
#14
I got the proper motors for the tank, also some sub-optimal reversible ESCs but it works well enough so I did a test in grass.

I say sub optimal because they are the cheapest car ESCs on banggood and while they have proportionnal throttle on forward, they only have two speeds on reverse. I guess it will make things interesting.
 

Fluburtur

Cardboard Boy
#15
With one side of the drive train complete and working I started making the other, I already completed one gearbox.
DSC_1641.JPG
It is relatively quick and easy to make one, I could release the STLs if anyone wants them but you need some specific hardware for it:
-8mm carbon rod
-4114 brushless motor
-bunch of M3 screws
-airsoft BBs
-7x22mm bearings

It should work quite well for most tanks of that category
 

Fluburtur

Cardboard Boy
#16
Since I have both gearboxes complete I did all the wiring and made a custom mixer in inav.
I could just use the elevon mixer on my radio because it works exactly like that but with inav I can have stabilized yaw which means smooth driving at high speed and precise drifing hopefuly, also it will be able to stabilize the turret.
 

Fluburtur

Cardboard Boy
#17
I just finished printing the other track so I taped on the FC and other hardwaer and went for a test drive at 3am.
DSC_1660.JPG

I will do more testing tomorrow, it is a bit late.
 

Fluburtur

Cardboard Boy
#18
I did some more driving and drove about 2.5km in one go without major issues.
It threw the tracks a few times so I need to re-design the drive wheels but otherwise it is fine.
 

Fluburtur

Cardboard Boy
#19
I made new drive gears with a better mesh and got some video since my brother is currently here (we are going to Canada tomorrow)

It still tries to throw the tracks a bit but less than before, also my brother broke a road wheel axle while doing a hard turn that put a lot of sideways force on the tracks. I need to program it so it cant do hard sideways forces to ensure it is idiot proof.
Also it is kinda bad as off-road but its primary mission is driving indoor on a smooth surface so that isnt much of an issue.