Originally when I was designing my first antweight I wanted jaws at the front and a lifter at the back but for 150g this was out of the question so I designed Odyssey instead. After a bit of research and fighting with ants I found out about the Hitec HS55 servos at 9g each which are a big reduction on the 16.6g Protechs. Also by this stage I had a spare 110mAh 4.8V NiMh battery pack from Overlander which weighs about 20g. This weight reduction allowed me to use an old Acoms remote control car servo for the weapon......
Anteater in it's 'primal' form will fit in a 4" cube and at the moment weighs 153g with weight reduction but still needs 3g of improvement.
At the front of Anteater is an Acoms 50g servo which must be about 3-4kg/cm which is linked via 2 metal struts to the arms, the inner bits being 2mm plasticard and the outer pincers being brass soldered into shape. 2*HS55's provide drive but are very fragile (might upgrade to HP Naro's), the wheels are tops of Lynx deordorant with elastic bands.
When the front servo is activated the front jaws spring open and the tail flips back via an elastic band, below you can see the catch which holds the tail in place.
I've mentioned above when it starts it's a 4" cube, well deployed it's a 6*8.5" ant well within the rules (once I lose 3g). Being the size it is if a flip is attempted the jaws expand to make it nice and wide. The tip force is about 280g measured by pincing my scales, this is with about 3.5kg/cm of main servo, JR do a nice servo with 15Kg/cm @6V (1.2kg of tip pressure).
At the moment it's enough to hold an ant and hurt your hand, the only catch is the deadly embrace rule so every x seconds I have to release the enemy and the driving servos aren't very powerfull to push other ants about.
Anteater did quite well against other ants and it's jaws tended to squash other robots wheels rather than do ant damage but it has never been flipped which is good.
A number of improvements were made for Anteater and it looks the same but is almost completely rebuilt, the changes were:
|Version 1||Version 2|
|Front jaws made from sheet brass||Made from sheet brass with steel nail as pincer tips|
|Rear part of jaws made from plasticard||Now formed from glass fibre|
|Wheels had elastic bands for grip||Dycem now used providing huge amounts of grip|
|Acoms 40g servo weapons servo, approx 3kg/cm||Supertec 136L 35g 8kg/cm @ 4.8v, portions cut for weight saving|
|4*110mAh NiMh=4.8V||5*300mAh NiMh=6V|
|Plasticard chassis||Formed fibreglass|
|Jeti Tx||Hitex Feather Rx|
|Mixer added for easier control|
At AWS9 it showed it was good by getting to the semi-final and getting past Odyssey, now there isn't a lot I can do to make Anteater better, the chassis, jaws and back part could be made lighter from carbon fibre but the only benefit I would get is the ability to upgrade it to 7.2V instead of 6 but this would involve almost another complete rebuild.
AWS9 was a long time ago, we have had AWS19 a while ago and Reading Robots 9 a few weeks ago. RR9 was the final outing for the S136L servo when it stripped a few teeth, It had a long run and didn't give me any problems until then.
Between AWS9 and AWS19 the only changes made were a few repairs due to damage
|Version 2||Version 2.1|
|Front jaws made from sheet brass with steel nail as pincer tips||Same|
|Back jaws formed from glass fibre||Same but several replacements later|
|wheels use Dycem||Same and same Supertec Naro HP BB for drive motors|
|Weapon servo Supertec 136L 35g 8kg/cm @ 4.8v, portions cut for weight saving||Same weapons servo but at 7.2V|
|Batteries 5*300mAh NiMh=6V||Li-Poly 7.4V 640mAh|
|Formed fibreglass body||Same|
|Hitex Feather Rx||Same|
|Mixer added for easier control||Removed, now use Tx mixing|
The main difference is the replacement of the NiMh batteries with Li-Poly ones. The weight is roughly the same but the capactity and voltage are higher giving longer running and more power. This is seen on the jaws which give about 660g of crush. This still gives me a problem as when they crush an opponent the body tends to lift off the grouond so the wheels are useless and the crusher isn't powerfull enough to do any damage on it's own.
One thing to mention is that the Naro HP BB drive servos still work off 6V. I used a 6V regulator to the Rx leaving the weapon servo on 7.4V The drive motors looked a bit fragile for 7.4V and I didn't want to risk it.
Another issue is the front supports for the arms. On the above picture you can roughly see a bent paperclip on the off-white back jaw arm. With spinners they tend to hit this bending it which causes issues. I have tried multiple approaches but nothing seems to be perfect.
Whats next? Possibly a replacement for Anteater. I have a Blue Bird 705MG servo on order which is the same weight and power of the Supertec but it uses metal gears to prevent stripping. I will have a look and see if Anteater has another 10 AWS in it.