Team Kaizen - The Honey Badger

[Ocracoke]

Heh, a coincidence I am sure!

Motor mounts are now done and they spin freely in the frame now. The next thing to do is mount it all into the chassis board. I get the horrible feeling, looking at the height off the ground, that the wheels I have got are not big enough but we'll see. I would have had the drive system wired in except I found that I was missing the sheathed terminal connectors for the motors and batteries so a quick trip to Maplin is in order methinks. I also need to order some connectors to fashion a removable link out of.

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[Ocracoke]

Today was a big one - the motors are now mounted on the chassis board and the first go at wiring it to run, which was successful. OK, so it isn't neat but it doesn't need to be at this stage, the fact that it runs (backwards to the controls it would seem) is a milestone in itself.

The new wheels have been ordered and should be with me by tomorrow. I've created a cardboard template to try and get the wheel hubs mounted centrally on the wheels. Hopefully I've got it measured and cut right (doing this sort of thing in the small hours of the morning is draining).

The weapon motor has been ordered so that'll be with me by Friday but the big one is the side panels that need to be cut. I feel yet another cardboard template coming...

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The SLA batteries are there purely for testing the thing, I still want to change them but I must confess to a complete lack of knowledge in this area. I think LiFePO4 batteries is something I'll go for, perhaps a six pack of this battery - https://hobbyking.com/en_us/zippy-fl...epo4-pack.html - but would this charger be OK? - https://hobbyking.com/en_us/turnigy-...v-capable.html. I think it is but I'd want to be sure before committing.

[Maxamuslead]

I'll go for, perhaps a six pack of this battery - https://hobbyking.com/en_us/zippy-fl...epo4-pack.html - but would this charger be OK? - https://hobbyking.com/en_us/turnigy-...v-capable.html. I think it is but I'd want to be sure before committing.

That charger is fine, I have one it works fine. You just need a power pack for it. You could mod an old computer PSU (not sure how but there be a guide somewhere) or if you lucky you could have a old laptop charger that will do, if you don't fancy any off them grab this https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1 it is what I use and it is fine.

On the battery, any reason why you are using LiFePO4? As Lipos look like they are the standard now and they are not that expensive to be honest.

Just make sure you get one with a high enough discharge rating (C) PP3D website will help there http://pp3d.weebly.com/getting-started

[Ocracoke]

On the battery, any reason why you are using LiFePO4? As Lipos look like they are the standard now and they are not that expensive to be honest.

True but LiFePO4s seem to strike a nice balance between safety if damaged, weight and power output.

Just make sure you get one with a high enough discharge rating (C) PP3D website will help there http://pp3d.weebly.com/getting-started

Many thanks, it looks like the battery I've mooted using will fry the speed controllers (30C x (4.2ah x 2) = 252 constant, speed controllers are 85), so I'll find some lower output batteries and go from there.

[Maxamuslead]

Many thanks, it looks like the battery I've mooted using will fry the speed controllers (30C x (4.2ah x 2) = 252 constant, speed controllers are 85), so I'll find some lower output batteries and go from there.

It is not as simple as at the 252 amps is the Max constant draw that battery could take (probably lower to be safe) hence why you can see 2 C ratings e.g. 30c constant 45c constant.

[Bodge Job]

Hey nice to see the new build going along well, was such a shame to see badger get flattened at Grantham! (I was the guy with the glitchy robot and Lipo that caught fire :P ). New build looks good, cant wait to see it in action! How ever with the electronics I think you're slightly misinterpreting how the maximum current ratings work.

The motor is what dictates the current, with the current depending on the voltage, and how fast the motor is spinning (stall being maximum current, and the fastest rpm being the lowest current).

The esc has no control over the current, it kinda acts as a very fast switch, so outputs what ever current the motor requires. The maximum current rating of the esc is the max current going through the esc before it gets damaged. Each company has a different way of deciding this rating so different escs cope differently. Some escs can cope with peak currents higher than their max rating (they just get very hot) and some will get damaged lower than their max current rating (particularly cheap escs, that can have exaggerated specs). This annoying nonuniform current rating system is where people's experience come into play. For example a ragebridge is rated at 40A but could cope with a higher current than a botbitz ecs rated at 85A, and both could cope with more current than a cheap ebay esc rated at 200A (irritating i know :L)

The battery also has no control over the current (unless you're working near its limits) , The maximum current rating of the battery varies meaning slightly depending on the battery type. With Lipos (and I believe LiFePo4) the max current is what the battery can safely discharge without damaging the battery. Lithium batteries will output a higher current than that, it will just damage them and can make them unsafe to recharge (hence the fuse rule for lipos).
Lead acid, and NiMd and NiCd batterys are slightly different as they won't output much more than their maximum rated current like lipos do. it can still damage them but not in the same way as lipos, as they don't become unsafe it just shortens their life.

This means you can have a battery with a max rating of 500 amps and a Esc rated to 200 Amps, but if you have a motor that stalls at 20 amps you won't damage the esc or battery. Its the max current of the motor that's important.
Its good to note that a motor will burn out if stalled for any length of time, and a burnt out motor will develop internal shorts so it may draw a much higher current than its stall current, so its good to have safety margins to help account for this or other faults. and many motors won't give a stall current, so again you'd have to use other peoples experience to find out what works.

This is a crude description, but I hope this makes things slightly clearer, it means it's fine to have a battery rated higher than your escs max current. If anything its better to do so. Just try to have the battery and esc rated to a much higher current than the motors are likely to use.

[Ocracoke]

(I was the guy with the glitchy robot and Lipo that caught fire :P ).

I remember! It was a bit dramatic when we saw that LiPo swelling. :S Hope you've managed to get some time in sorting Bruiser out.

Thank you both for the explanation. I've checked the motor specifications and the upper limit of constant draw it can take is 69 amps before it stalls. So if I aim for a battery setup that has a similar constant amperage to the motor, I reckon I'll be OK I think.

Today was a big one, the new 110mm wheels arrived and they just (and I mean just) reach the floor. Talking 1 or 2mm ground clearance. Drilled and bolted the hubs onto them and then the hubs onto the motors. After finding that the robot finally has traction, I took it to a community centre to run it and see how well it moves.

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Even without any castors at the front on rough tarmac and running with tiny 1.2ah SLAs, the thing shifts, properly shifts.

The weapon is, I've decided, going to be a fast reciprocating spear powered by a Smart Car windscreen wiper motor along with a array of spikey type things around it. In later revisions I may go for a spinner blade but the spear is a bit more friendly to events that can't have spinners in.

Apart from the side panels and weaponry, the checklist of snagging things are:

• Grind down the swarfe on the chassis board underside and wheels to allow countersunk screws to seat properly.
• Round off the floor facing edges on the top panels.
• Add in a castor ball on the front.
• Add in a support for each motor on the underside to prevent it bending the mounts.

Just measured the robot as well. At the moment, it is 56cm long, 37cm wide and 23cm high and weighs 5.8kg.

[Ocracoke]

So I've installed a castor ball to the front of the robot and ground off some of the swarf from the panels to get the screws to bed in a little neater. I then took the robot to a friend's place over the weekend just to see how controllable it is in a confined area, which seemed to go OK but the batteries were drained afterwards.

One thing I did notice was that the Badger had a tendency to jack itself into the grouting. The cause seemed to be the shell's rear panel which was lower than the bottom panel so I've been busy grinding off the edges to make the underside as flat as possible. The rear is done (much HDPE snow was made with the Dremel) and I need to do the front.

The wheel hub from the original Badger is knackered however, the grub screw is completely seized in the hub, which I suspect is bent slightly as that was the hub on the weapon bar which, as we all know, got hit very hard. So a new wheel hub is in order.

Other than that, the next one is the big one, the side panels which personally I am dreading as I've got no access to a vertical saw to cut with (unless my father in law has one...). However, once done, the rest of it will come together quite rapidly and then I can finally get on with implementing the weapon.

I can only assume that I wasn't selected for Insomnia as I've still not heard back from them so unless there is an event between now and October (such as a social/car park event), the début of The Honey Badger will be at Stevenage.

Pictures to come tonight.

[daveimi]

I'm in Blackpool if u wanna meet half way for the first "underground" fight...

[Ocracoke]

I'll PM you on that front.

I must rescind my comment on not having heard back from Insomnia - looks as if The Honey Badger has been accepted but I may have a conflicting event on during the weekend so I remain tentative. Either way, not lost the motivation to get the thing rebuilt.

[Ocracoke]

And here are some pictures.

First one is of the rear panel being shaved. Still needs a bit more work to make it not grind down on the floor but it is getting there. Second one is of the castor ball, complete with rudimentary height adjustment with the use of a couple of nuts acting as spacers to lift the ball up and down. Last one is of the snow... because it looks pretty. :P

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Side panels... going to have to invest in a jigsaw methinks.

[Maxamuslead]

what are you planning to do with the rest of weight budget ?

EDIT: i know make 2. Cluster bot baby

[Ocracoke]

The robot, with the weapon motor in but nothing else for the weapon, weighs 8.5kg. Assuming the side panels round that up to 9kg or so and the rest of the weaponry gubbins take it to 10, the rest is likely to go towards static weaponry and chassis reinforcement (oh, and a groovy paint/Sharpie job as well :P)

i know make 2. Cluster bot baby

Hehe. If I do another FW, I might consider that

[Maxamuslead]

The robot, with the weapon motor in but nothing else for the weapon, weighs 8.5kg. Assuming the side panels round that up to 9kg or so and the rest of the weaponry gubbins take it to 10, the rest is likely to go towards static weaponry and chassis reinforcement (oh, and a groovy paint/Sharpie job as well :P)





Hehe. If I do another FW, I might consider that

You going to add a steel strip on the end of the wedge ?

also minibots

[Ocracoke]

Yeah, I'll be adding a metal edge to lower front and rear edges. I'll also be covering up the other edges with something similar just to make it look a little tidier. Metal guards around the drive wheels as well.

I've never really been sold on the value of minibots to be honest.