Antweight Kit

[Merkabah_PT]

I am thinking about making an ant, more like a prototype for a POSSIBLE kit to be developed here in Portugal.

I really want to try to get this hobby started here and i found two things that might be holding it back:
-Cost;
-Almost no parts avaliable;
-Getting your robot into pieces.

I am trying to make the cheapest but reliable robot and the battery also have to last more than 3minutes.
Servo drive, servo weapon, cheap 4ch 2.4ghz radio and possible 3d printed body.

The main targets of this kit will be kids and teens, but they will also be good for adults.

I will only order parts from a portuguese site, it's expensive but they ship the order in 24h. If the project gets green light i will order from HobbyKing.

I will use my CT6B radio for the prototype and this are the parts i am thinking about:
Driver Servos: 2x Tower Pro SG92
Weapon Servo: 1x Tower Pro MG90s
Battery: 4.8v 600mha AAA nicd

What do you think about this parts list? I know i could go for a smaller battery but i want to robot to run for how long as i can, so people can have a long play time without having to change the battery.

I will have a 3d printing workshop next week, and only then i will know the prices.

[Mega Masher]

Sounds great, good luck with the project.

[Phil]

Good on you for working to get others interested. An antweight kit got me started into ants. We also started with servo drives.

I do wonder if the weapon servo is strong enough. How long to you imagine your lifting arm will be? What will be the ratio between the servo horn and the lifting arm?

Hope it all works out well for you.

[Merkabah_PT]

I am just in the beginning of the project so no CAD's or any kind of drawings.
I will make it as small as possible, just enough room inside to fit all the parts and wiring.

Tomorrow or monday i will start to make some drawings and CAD's.

1.8KG/CM will not be enough? The only other micro metal geared servos the portuguese site as are these:

Tower Pro MG16R
MG16R: WEIGHT-18.8G, DIGITAL
DIMENSION:29*11.2*29MM
OUTPUT TORGUE: 2.7KG/CM(4.8V),2.9KG/CM(6.0)
OPERATION SPEED:0.10SEC/60DEGREE(4.8V);0.08SEC/60DEGREE(6V)
OPERATION VOLTAGE: 4.8V-6V
TEMPERAYURE RANG: 0DEG - 55DEG
DEAD BAND WIDTH: 5US
CONNECTOR WIRE LENGTH:160MM
GEAR TYPE: ALL METAL

Tower Pro MG90
MG90 SERVO
METAL GEAR WITH BEARING
WEIGHT: 14G
DIMENSION: 23*12.2*29MM
STALL TORQUE: 2.2KG/CM(4.8V )2.5KG/CM(6V)
OPERATING SPEED: 0.11SEC/60DEGREE(4.8V), 0.10SEC/60DEGREE(6V)
OPERATING VOLTAGE: 4.8-6.0V
DEAD BAND WIDTH: 10US

They are both 2.2kg/cm @ 4.8v but they cost 13€(11GPB), while the Tower Pro MG90s cost only 8€(7GPB). In hobbyking servo are MUCH cheaper, but i would pay more for the shipping than the 3 servos...

1.8kg/cm will not do the job?

I really need to get some cad's done to see +/- the lenght of the arm.

Thanks for the help guys.

[Shakey]

Heya, I suggest heading over to the robotwars101 forum, most the antweight builders hang out there and have a lot of good advice they can give you.

[joey_picus]

I second the suggestion to make use of the RW101 forum, there's quite a few discussions there about kit antweights (it's approaching half past 3am here so I can't really find any, but this page comes to mind too).

The MG90 servos are surprisingly easy to modify for continuous rotation and good speed though - Josh Valman does some 3D printed spacers which are brilliant for that - and I know a few ants have used them for drive, including a finalist at the last AWS I was at (3!

[Merkabah_PT]

Thanks for the info, i also found this site explaning how to mod the mg90s: http://robocraft.ru/blog/mechanics/595.html

I was thinking about using metal geared servos just for the weapon, and plastic geared for the drive.
Do you think the plastic ones will not last long enough?

The idea with this possible kit is to kids, and adults too, to have fun assembling them, learn a bit and the fight other kit bots. They will not be subjected to high impacts or spinners, the worse that can happen is get flipped (or some one dropping the robot to the floor...).

I will go to the RW101 forum and search around and maybe start this thread there.

Thanks guys :wink:

[joey_picus]

I'm not certain they would (I've not used the SG90s for drive but they don't look too strong) and the MG90s would simplify things by having them all around...also, if you did make the kit with all MG90s, you could probably get quite a good discount for volume!

For actual combat you would probably need quite a hefty weapon (as Spyro, the MG90 driven robot at AWS38, did) to be competitive with using them, but for fighting each other and getting experience they would probably be more than fine.

[Merkabah_PT]

Hum, ok. Better spend a bit more on the drive servos and make the robot last much longer. They are only expensive here in Portugal (8€ or 7GBP), on HobbyKing they only cost $7/3GBP/4€.

By all around you mean for both drive and weapon?
For the weapon poeple said that 1.8kg/cm would not be enough, what do you think?

The MG16R is the most powerful micro servo i can get here, but at 13€ is very expensive.

I would like to avoid HK because ordering just 3 servos, the shipping would be more expensive than the parts. Maybe i can wait until May (my birthday) and order 6 servos and a TX/RX.

For now i will do some cad's and some possible designs.

[Phil]

Just looked at the HK postage page. International (Registered) Air Mail 101-200g US$5.99

I like to go for 300 grams of lift at the tip of my lifting arm for an analogue servo or 200 grams for a digital.