Barróg - Featherweight Lifter Build Diary

[Shooty]

Alright, so at the moment, I'm currently trying to find a way to control the Linac, and finding a controller for the job is proving to be tricky. I was hoping to simply use another of the BotBitz 30A controllers to control the Linac, a little excessive for something that should be drawing no more than 7A, but at the moment my current (heh) concern is having a controller that can handle the 18.8V from the battery, as well as the fact that it would be a spare controller for the drive system should anything go wrong.

My problem now though is that there doesn't seem to be any way to get the BotBitz ESC's before January, and I'm trying to find alternate controllers for the actuator. So far, I've found a few controllers on Hobbyking that should be able to handle the Amps, but I'm a little concerned about the size of the battery they'll be accommodating.

TURNIGY 30A BRUSHED ESC: https://hobbyking.com/en_us/turnigy-...ushed-esc.html

HobbyKing X-Car 45A Brushed Car ESC: https://hobbyking.com/en_us/hobbykin...d-car-esc.html

20A Brushed ESC - Turnigy TZ4 AWD/Drift Spec: https://hobbyking.com/en_us/20a-brus...rift-spec.html

I still have the option to use the micro switches and the servo should I run out of time, and it continues to seem like a good option, but I'm mostly posting to ask if A: Are the controllers above actually suitable to use given my current setup (18.8V battery)? And B: In the likely event that they aren't, are there any brushed ESC's that are available right now that could be used with this machine?

[Maxamuslead]

One option if your up for it is to by a TZ 85a and flashing it to turn it into a Brushed motor.

Best thing about this method is that if you get comfortable doing it you can have a cheaper supply of bitbotz 85a ESC

[joey_picus]

A: Unfortunately not - I've had this problem too, there just doesn't seem to be a market for small brushed single-channel controllers that do more than 12v The first one mentioned also doesn't have reversing capability, which is slightly essential if you're going to power the weapon down as well as up!

B: I've been looking for something similar too, to be honest - one option would be one of the Mtroniks controllers (http://www.mtroniks.net/prod/Boat-Sp...rine_15_HV.htm) although these are somewhat expensive. The traditional way of doing this was with a double-ended relay board like a Team Delta or Electronize model, but the former are only available on Servocity ($$$) and the latter seem quite hard to find at present. It's frustrating since you'll generally find the actuator will draw about 5 amps at absolute most so it's not even a lot of current if you find something small and good that does reversing and 24v, let me know...

[shakesc]

The best investment I made was an Atmel programming socket and USB adapter
https://hobbyking.com/en_us/atmel-at...___store=en_us

I have used this lots of times - ESC's will die and being able to reprogram yourself is a big saving

[Andy1979]

I got a brand new brushed 30amp botbitz controller. Never been opened. Whats it worth lol

[Shooty]

So I've read through each post here, and it's made me realize that I should really learn how to program an ESC myself, another bit of electrical knowledge needed there but I suppose it was going to be necessary to learn at some point. The Mtroniks ESC looks like it'd do the job however, so I definitely will need to keep a note of them.

Andy, the Botbitz 30A's cost £30 on the Ranglebox store, and I'd be happy do do a deal with you over messaging if you're interested in selling whatever price you're offering!

EDIT: unable to get the Botbitz 30A, have ordered the Mtroniks ESC instead.

[Shooty]

There's only a week to go until Mechatrons 2018, and Barróg is nearly completed. Since the last post all of the construction work bar the front claws and side wings has been finished, an ESC has been acquired for the actuator, and the machine is a fully operational 4WD lifter. Here is a video demonstrating it driving, lifting, driving while lifting (NOTE: the machine can go faster with a load, but I kept it slow in the video so as not to tip it off balance), and self righting:

https://www.youtube.com/watch?v=UB5VrbtXgLU

One of the front claws has been cut, and only needs to be inserted into the machine. For a while now I was considering having only one front claw in the center of the machine to save on weight, but looking at what I have now, I think I can fit the two in. I'm calling this final part of the build

OPERATION TRANSFORMATION

on account of the fact that I'm trying to lose as much weight as possible in a short amount of time. Should the machine be entered in the state it's in along with a single claw, it will weigh around 14.0kg. However, I've already been able to shave around 160g by halving the vertical thickness of the underside of the lifter supports (I'm pretty terrible at naming things, so the white extensions attached to the green lifter, reduced from 30mm to 15mm), and other spots capable of losing weight include the rear mounted supports for the lifter (can be hollowed out), and the lifting spines (holes can be drilled through).

The other priority for me is mounting the electronics internally. For the tests, the battery was mounted in a corrugated cardboard insert shown here:



I'm hoping to zip tie the transmitter and actuator ESC to the base, the drive ESC's to the rear lifter supports, and the safety link to the back plate, but I'm still unsure what to do with the battery. I can't use the cardboard insert when the front claws are in, and besides they don't work once the machine tips over (as is unfortunately demonstrated in the video above despite my best taping efforts). My current plan is to keep the battery in a smaller corrugated container shown below, and to attach it to the base with a velcro strap that will wrap around two slits in the bottom. If anyone has some other suggestions for the battery that won't take up too much weight though, then I'd love to hear them.



Electronically all that's needed is for the safety link and fuse to be incorporated into the main circuit, and for some XT60's to be fitted where need be. Hopefully the machine will be finished as per what I originally intended and will be in Dublin for the 10th of January.

[Ocracoke]

My current plan is to keep the battery in a smaller corrugated container shown below, and to attach it to the base with a velcro strap that will wrap around two slits in the bottom. If anyone has some other suggestions for the battery that won't take up too much weight though, then I'd love to hear them.

I keep my batteries in a Fire Retardant Bag, which is then held in a Tupperware box with the lid and padded out with shopping bags. Hasn't let me down in the many, many, many flips The Honey Badger has endured. Originally, I had also used a over metal strap to hold the batteries down on the chassis along with some Velcro along the bottom as well. Perhaps that might help?

Looks good mind, well done You may want to think about investing in a set of Omni wheels for the rear at some point to aid turning though they are a bit pricey - https://www.robotshop.com/uk/4-duraomni-wheel.html

[Shooty]

Your build diary was actually the first I looked up for suggestions on the battery given the similar shapes of the machine! I was a little skeptical of the tupperware container at first, but seeing how long you've been using it and seeing some of your fights has given me a lot more confidence in it, I'll definitely be looking at that as an option. Grip in the back does seem to be noticeably less when something is raised, but given the weight distribution that will be caused by the front claws I'm more concerned that the back wheels won't be on the ground at all! Hopefully, I'll have an update as soon as the front claws are in place.

[Ocracoke]

I was a little skeptical of the tupperware container at first, but seeing how long you've been using it and seeing some of your fights has given me a lot more confidence in it, I'll definitely be looking at that as an option.

I should warn you, if you do decide to put them in a box (doesn't have to be Tupperware :P), it has to be anchored down evenly otherwise the base is liable to crack.

[RogueTwoRobots]

There's only a week to go until Mechatrons 2018

Jeez, so there is. Better get my finger out!

[Shooty]

Just a few quick questions to ask concerning the machine and live events in general:

1. I'm looking at using a 1-2mm 50mm long piece of stainless steel as a relatively lightweight wedge along the front for the event, chamfered at the sides and below at 45 degrees. Hopefully this drawing can explain better my idea. Would a wedge like this survive a 3 day non-spinner event relatively intact, or at least be repairable to the point of usefulness between bouts? Could I go lower than 2mm stainless steel, or should I go higher? Bear in mind weight and time is an issue for me, I'd ideally like to have a more long term setup for the future, but what can you do, right?



2. I notice the tech check rules state that a machine needs to have some sort of cradle setup for holding. Until now I've been using large HDPE offcuts to keep Barróg's wheels off the ground. Would this fly at an event, and if not, would it be possible to simply build a frame out of wood to hold it off the ground? Would I need straps to hold it in place?

3. Would the lifter require a locking bar? I know most pneumatic and kinetic weapons require them, but would an actuator require one as well?

4. When I turn off the transmitter, everything in the machine comes to a halt. I know of the removable link rule, and the machine has it, but would the halting of everything in the machine via turning off the transmitter satisfy the failsafe rule?

One last extra pic of the new revised lifter spines:

[Ocracoke]

To try and answer your queries:

1. The Honey Badger ran a 1mm thick Aluminium door finger plate along the front of the HDPE wedge and that did OK when the plate was wholly on the wedge as it was supported. At the Maidstone 2017, I moved it forwards and put it on hinges much to the same effect as you plan and it buckled horribly. I could straighten it out with a hammer but really, I'd advise against it. Steel might be better but I don't think it'll stand up at 2mm.

2. I use a wooden cradle with no straps and that has always been OK. It needs only to keep the robot off the ground and be stable enough so that if the drive wheels do spin, it doesn't come apart. Mine is very wide to allow for this.

3. Ask the event organiser on that one. I recall Luna-Tic asking this for the FW championships in 2017 and RoboChallenge said they didn't but this is one of those times where the event organiser needs to determine this. However, if in doubt, assume it does.

4. Yes. One of the tech checks is to check for exactly that (i.e loss of signal = no movement).

[Shooty]

The Honey Badger ran a 1mm thick Aluminium door finger plate along the front of the HDPE wedge and that did OK when the plate was wholly on the wedge as it was supported. At the Maidstone 2017, I moved it forwards and put it on hinges much to the same effect as you plan and it buckled horribly. I could straighten it out with a hammer but really, I'd advise against it. Steel might be better but I don't think it'll stand up at 2mm.

Interesting. I feel I should clarify though that with the steel piece, the top half of it is bolted on to the HDPE front as opposed to being hinged, sorry if the drawing didn't express that clearly. If you were able to use a 1mm piece of Aluminium scraping along the floor, then I assume that a 1mm piece of steel should hold up as well?

I'll also get onto the event organizers concerning whether a locking bar is necessary or not; I can probably have it go through the front claws where they meet the front of the lifter, though I don't know if something will break or not should I operate it (front claws could be ripped up, gears in linac could break, etc.) It seems from what I've been reading on other build threads that FW lifters seem to get away with having no locking bar, but the "clamper" part of the robot's design may pose more of a health and safety concern.

[Maxamuslead]

3. Would the lifter require a locking bar? I know most pneumatic and kinetic weapons require them, but would an actuator require one as well?

Ask th EO but i would design it so you can in anycase, plus you could use the holes you need to drill as weight saveing.