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Ondray
Joined: 06 Jul 2015
Posts: 142
Location: Newcastle
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This weekend saw the arm mounts go on! I wound up making and trying two different mounting options, one high and center on the frame with a 1:1 ratio and the other lower and towards the front with the 2:1 reduction.
The arms are made out of some scrap steel from the good old council cleanup I got to do some angle grinding and heating up steel to red hot with a blowtorch so I can bend it - lots of heat and sparks - I actually felt like I was doing some metal work!
Attempt one looked like this:
The shaft the arm sits on is some M8 rod, which goes through some flange bearings in the small steel section which houses the sprocket. The sprocket is held by a grubscrew, which will need a good recess to be made to reduce slipping. For the moment the arms are pinned between two nuts, this will be upgraded to being welded to the shaft when I get a chance to visit dear old Dad.
The discovery from this test is that the 'low speed - high torque' window motors are much faster than I expected. I couldn't get a feel for the torque without the arms being welded because the nuts just unscrewed, but based off how quick they were swinging I don't think it'd be enough torque for lift. But this wasn't a problem I hadn't anticipated - which is why I ordered some bigger sprockets as well. I can put the shafts lower and closer to the front to run shorter arms with a 2:1 reduction which will hopefully give me the lift-grab I want. Failing that however I can go to an axe style bot, which part of me deep down would prefer as it is more destructive in intent So at some point this week there will be a trip to the hardware store to get some cold chisels to use as the axe head...
The low front brackets look like this:
And the chain setup looks pretty (will be prettier once I put the washers in to align the sprocket better and cut a bigger hole in the Al) :
The two arms options side by side:
The arms are not their final length yet - I kept them as the full length of steel so I can cut them to the desired length once I've settled on a design. I think I'll take both options to fully made, then choose moments before each fight. I've got the parts and they're real easy to swap out. I'm currently planning on making the top mounts into a dedicated axe weapon and making the bottom ones the lift/grab. I will stick with the lifters as the primary at the moment as that mount is more sturdy. Though I do like that this design allows the axe to reach in front of and behind the bot, and work while inverted!
I also made a stand for the bot, and starting putting the skids on, it's getting close to the polycarb covers going on and being ready:
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Mon May 16, 2016 10:13 pm |
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Ondray
Joined: 06 Jul 2015
Posts: 142
Location: Newcastle
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The modular weapons is more because I don't know what will work until I'm able to weld it - which will be next weekend. So I'm doing what I can for all the options so I'm ready for welding and testing.
This weekend I got the polycarb on and worked on the weapons some more. With the skids on I was able to do a good test drive, and after fidding with the settings to get it turning the right way it drove really well! The nice scratch free polycarb is hard to see, but it protects the electronics nicely:
And the weapons, I've got a chain to attach a flail head (dont know what to use yet - I do have the towball from the old volvo, but it may be too heavy). Then there's the cold chisels which bolt in between the two arms where the chain goes in, then I've got two lifting arms and a grabbing arm...Maximum modular!
The to do list is getting short, but it's still significant, the most important (and proving to be more difficult than I thought) is the master switch/power light. I'm up to my 3rd iteration, the plan is to use an M5 screw tapped into some chopping board to join two pieces of copper. The latest one seems to work, but it's not as sturdy as I would like so I might remake again if I get time. Otherwise I've got a switch from jaycar that *should* handle the current. Also have to shorten the cords to make it neater and put the weapon locking bar on - hopefully I've still got time to polish it!
Here's the dodgy switches:
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Sun May 22, 2016 10:35 pm |
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Ondray
Joined: 06 Jul 2015
Posts: 142
Location: Newcastle
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Thanks Ash, but turns out they didn't need to dominate me but just wait for my wheels to fall off
Seriously though despite 1:3 win:loss I was super happy with the performance of this bot.
Won my first fight against a fellow newbie - charged straight at his flailing chains thinking they would only do superficial damage but they took both of Hellamax's eyes out! Fighting blind, still managed to get some good hits into the wooden armor. At the start I said I was aiming for the battery, but in the heat of battle I was just going for center body mass. After a good bit of biff the other guys drive motors failed - I think those big tires were too much for the little motors. As he was getting counted out I went to do a victory spin and watched both of Hellamax's wheels fall off lol. So it went to judges decision and I done more damage. I did lose an eye permanently though so it was replaced with an eyepatch...YARR!
So frantic upgrade to the mounting system for the wheels during the break for the next fight against Angus's Repent - the OTHER flailing chain bot of the night So with the confidence in Hellamax's armor cemented I just went straight at him and was going ok, despite the eyes and endcaps being completely ripped off. At first the problem was the height of his bot meant at point blank the arm of my axe was hitting instead of the head. Next problem was a drive wheel slipping. Next the power failed - turned out the solder came off the master switch - doh! At least that was the only time Hellamax was counted out that evening.
So the bigger break meant a busy overhaul of the drive system and fixing some soldering. I was using a lazy method of locking the drill motor clutch and just holding the locking pins on the ozito drills by screwing the clutch spring holder on without the spring. One of these came loose so I ripped it out and put some grub screws in. I also had to pin the wheels onto the axle properly - I was just using the shaft threading into the plastic of the wheel to transfer power - it stripped. So I had to drill and hacksaw some space for a pair of washers to pin them in place - only got it done a few mins before the fight with Brutus.
And what a great fight I was! With the drive sorted it meant I had a full round of glorious axe vs axe biff Hellamax took quite a beating (see the damage pic - mostly from that big black axe). This fight was where I learned an unforeseen benefit of this design - when in a bad position I could use the weapon to 'roll' away and re-position myself. Handy when I was stuck copping a pounding and the wheels weren't contacting the ground. But still wasn't enough to gain the judges favor - Brutus clearly done more damage, though the 6mm polycarb held up impressively. There was one point we all thought it was penetrated, but it was still intact so to all the polycarb naysayers.
Quick tightening of the drive system, charge of batteries and googly eye glued back on Hellamax was ready for the last fight against Voli...so fast, so much under bot. I knew exactly how this fight was going to pan out before I went into the arena. Hellamax was not built to be close to the ground, maybe if I had time to put my lifting arms on I could have put up a bit more of a fight, but only a bit. The disadvantage of a big bot is being an easy target for a small fast bot like Voli. But still I got some hits in and left a couple of marks so there's that. Also the ability to roll off using the axe proved useful. Lasted the 3mins, one wheel was a bit slippy toward the end but I could still move. Biggest problem in this fight that was only a smaller problem in the previous slower paced fights was that when the axe was 'cocked' if it was cocked too far it dragged on the ground or even pushed the wheels off the ground making driving hard to impossible - and while I was fiddling with the axe Hellamax was getting smashed from every angle. The axe also seemed to be jamming a bit, I think with thing bending over the course of the night the chain was becoming loose enough to bunch up an jam in the chassis. Either that or the locking mechanism on the window motors was playing up - will need some testing.
Then the rumble With once drive wheel on only half working I couldn't do much controlled movement - but I didn't need to! Hellamax just bashed everything that came withing reach Got into a good little scrap with First Pick early on, got flipped by citizen flips - incidentally my biggest 'worst case scenario' for Hellamax getting massive damage was getting thrown into the air by a CO2 flipper and landing in its weapon ripping the dogey mount system of the chassis and taking half the electronics with it. Well Hellamax was thrown into the air and landed on the weapon, but held up perfectly Only to get tangled on Twitch and spend a couple of mins spinning around in the middle of the arena lol. Got off, got some more hits in only for it to end all too soon
So - the damage:
The two left pics are the brutalizing from Brutus and the top right shows the cracked weld on the chisel, Dad's welds survived the night!
So, positives:
- The weapon done a nice amount of damage.
- The invertibility was a boon.
- The weapon attacking front/back and upside down was great
- Being able to get out of bad situations using the weapon was super handy.
- It looked great (if I do say so myself).
- The chains stayed on almost all night, and even with one down the axe still worked (though noticeably weaker).
Negatives (or to be improved):
- Wheels. Not. Wheeling.
- The weapon dragging and pushing the wheels off the ground.
- The slack in the weapon chain made fine control impossible.
- Center of gravity being too far back when the axe was cocked to get good traction. (I figured out toward the end of the rumble it actually drove better backwards - when the center of gravity was where I intended with the lifting arms)
So first thing I'm going to improve is making the axe head not drag in the 'cocked' position. It's still about 2kg underweight so I'm thinking of adding another pair of wheels to the back to go 4WD and to have some support for when the axe is cocked. But before I go smacking more wheels on I'm going to make the current ones reliable. I've already got plans in my head for better wheel locking system and a feather for nationals - which really isn't far away...
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Wed Jun 08, 2016 11:35 pm |
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