R7

Post any technical advice and/or bot building related topics on here.
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StarlessSoldier
Posts: 1057
Joined: Wed Dec 31, 1969 7:00 pm
Location: Fort Bragg, NC

R7

Post by StarlessSoldier » Sun Jun 28, 2009 3:02 pm

This is my new ant, R7. Knee Breaker style bar spinner.

Drive: 2x Hitec MGBB servos, modified for continuous rotation. Lite Flite wheels mounted to servo horns.

Power/Control: Hitec 8 channel reciever (couldn't get a micro to work), Pheonix 25 Brushless controller with BEC for the reciever. 2 cell LiPoly Thunderpower pack.

Structural/Armor: .060 Lexan baseplate and top braces. 3/8" OD square fiberglass tubing for rigidity with M3 hardware.

Weapon: Outrunner brushless motor direct driving a 7" stainless steel bar, angled slightly downward.

Currently works fine, but I have one extreme bitch of a problem. The blade loses balance at just over 1/4 throttle and causes a Mauler/Ziggo/SoW effect. I'm working on balancing it, but I might try to make a new blade if I can't fix it.

Image

Image

StarlessSoldier
Posts: 1057
Joined: Wed Dec 31, 1969 7:00 pm
Location: Fort Bragg, NC

R7

Post by StarlessSoldier » Sun Jun 28, 2009 3:07 pm

Does anyone have any advice or useful experience for balancing an antweight weapon?

Area51Escapee
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Joined: Wed Dec 31, 1969 7:00 pm

R7

Post by Area51Escapee » Sun Jun 28, 2009 3:21 pm

Wow, that bot looks great. Nice job, John!

Yeah, that really sucks from about the balance issue. I'm guessing horizontal bars like that are much more a bitch to balance properly as opposed to Paul's Hit or Miss. Maybe the bar just needs to be repositioned? Then again, I have almost no bot building knowledge, so it's probably not that.

Siphai
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R7

Post by Siphai » Sun Jun 28, 2009 5:33 pm

thats awesome. obviously i have no clue how to fix anything but that bot owns.

StarlessSoldier
Posts: 1057
Joined: Wed Dec 31, 1969 7:00 pm
Location: Fort Bragg, NC

R7

Post by StarlessSoldier » Sun Jun 28, 2009 5:37 pm

Tommorow I'm going to try to make a new blade, this one has a slight offset to the mounting hole that might be causing my problem. I might also do some shopping around for small saw blades. When I control the motor with a pair of visegrips I can actually saw through wood with the bar haha.

StarlessSoldier
Posts: 1057
Joined: Wed Dec 31, 1969 7:00 pm
Location: Fort Bragg, NC

R7

Post by StarlessSoldier » Tue Jun 30, 2009 2:17 pm

My bad luck continues. I made 2 new blades and tried them out, all with the same imbalance issues. Then one of them made it past 1/2 throttle and completely destabilized. The force twisted the chassis, allowing the blade to hit the body. It cut through the main hot wire, pulling the battery up into the blade and tearing it up pretty bad. It also somehow hit the right side drive servo and broke its mounting flange. I leave for the airport tommorow morning, so I don't have time to fix it. I'm still coming to ARCCON but R7 will be sitting this one out. I think I might just stick to saw blades from now on... :P

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That Kode Guy
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R7

Post by That Kode Guy » Wed Feb 17, 2010 3:28 pm

Thought I'd bump this so you don't have to make a new thread (it doesn't appear to show up in the The Junkyard board itself :S)

That, and I still think that spinner looks fucking awesome. Has it been fixed since the blade went batshit unstable last time?
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StarlessSoldier
Posts: 1057
Joined: Wed Dec 31, 1969 7:00 pm
Location: Fort Bragg, NC

R7

Post by StarlessSoldier » Sun Feb 21, 2010 6:50 am

I had to put things on hold for a 12 month deployment, all my parts are in storage. I have plans when I get back however, to rebuild it as a vert spinner.

Also, after talking to a few people, I believe I know the source of my problem. When using the case output shaft on an outrunner, the load has to either be very light or very small diameter to keep balance. So while my blade may have actually been balanced, the motor itself was unstable. Lesson learned.

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