Team Death - New Heavyweight

[shakesc]

Just be careful with Chinese Amps, they are more powerful than the metric version

[Rapidrory]

Yeah, the single channel FeatherTwos can actually handle more juice than a TZ, as 85 China amps translates to about 40 metric amps over 3 minutes.

[team death]

Thanks for all the information Guys-We are actually running 24 volt CIM wheelchair
motors, the power is via 2 lipo 4s which gives us 32 volts.
I dont really want to change that set up because we are really happy with the
performance so far.
The motor for the jaws I think is also a CIM but a slightly longer one than the
ones used for the drive-it's rated at 30 amp also.
The idea is that one member of the team will have a two button box coming
off the main radio controller for open and close of jaws, I'm thinking the buttons will
be on springs so a quick press on either closes the jaws ( in tests the jaws closed
in less than a second on 16 volts) Im not sure how much amps will be drawn when
the jaws meet thier stop point.-theres no provision to cut the power supply at present.
Also is there a preffered method to get 32 volts down to 24 as most ESC I have
seen have a top voltage of 24 volts.

[Redirect Left]

Another Sunday, another batch of snow and ice!
For the first time in a few week, we both managed to make it to the days work.

Today was spent setting up the link, and mocking up the all the intended layouts for wiring locations and routes.

It took us longer than anticipated to do this, as we struggled to fit things into varying sockets and othersuch. However, we managed to complete it, and after we traced out the intended location of the batteries, ESC, and motors, to work out how much cable we needed for it all.

There's a few things we established from today - the motor that runs the weapon doesn't run on its own fuse, unlike the the traction motors, so this might be modified in later on. We also need to actually build the area where the ESC will sit, and we'll need to finalise a solution for controlling the weapon motor, and whether to stick with the homemade solution, or one off the wonderful internet. We're aware of another upcoming purchase, the hydraulic jack trolley for getting it around will be quite a bit of money. So we may see how the homemade solution performs in a few real world scenarios before we make a final push on that front.

Over the week, Colin is going to try to make a start on building up the area needed to mount the ESC firmly in place, and I'll be paying another visit to Maplin, if its still open, as we need a bit of extra cable and sockets.

[Theo]

Sounds like good progress!
I can't believe we live in an age where the future of Maplin is in doubt. Such terrible times

[Redirect Left]

I can't believe we live in an age where the future of Maplin is in doubt. Such terrible times

Realistically speaking. I am 100% part of their problem. I know full well everything they sell can be bought from Chinese resellers for about £0.25 to £5. I only ever walk into their shop if I need it in a time I can't guarantee delivery from China

[Theo]

I just go in because I can't be bothered with online shopping half the time. 3 days delivery vs A trip to Maplin. Plus they sell Stylophones, bought 6 from them over the years

[Redirect Left]

Another Sunday, this time with 1 hour less sleep than usual. But not to worry, we both still put in a good days work despite that.

Today was another focus on the electrics. However, let's go back in time slightly - over the course of the week. Colin has removed the original container for the much smaller ESC we first planned to use, and has built a much larger one in a different position to contain the rather large Cytron ESC. During the week, I had also sourced some cables which would come in use today...

Dragging back to the slightly less back in time of today, we had a few issues getting some plugs onto some cables.
Unfortunately for some reason, we didn't manage to get the soldering iron (two of them), to solder in any meaningful manner. After a while of faffing around and achieving not much, Colin ended up finding his blowtorch and using that. Over the top, but certainly got the job done in record time. Next week, I'll take the soldering iron I have at home and see if that does any better - as using a blowtorch. Colin had also acquired some junction boxes, this allows us to split the battery power between the main Cytron ESC and the two traction motors, to another as yet to be decided ESC and the weapon motor. We found a nice little spot to put the junction out of harms way, but still relatively easy to access without having to remove it from its new home for maintenance. We also found a spot for the main fuse, which is now lovingly zip tied in place. The circuit starts at the batteries, then immediately into the link, after it goes into the fuse, and then as evidenced on image 1, straight into the junction box between the ESCs and motors - each motor still has its own fuse.

We finished off today by drilling some holes into the new ESC container for all the cables to go through. Because the Cytron ESC doesn't use plugs, and you simply screw the bare wires into it, this was an easy task as we didn't need to account for cable plugs in the hole size. Colin has fashioned a lid for this new ESC container, as well as extra side armor to protect the fairly thin box of the container, which we'll hopefully have done by next week along with the rest of the wiring (image 2)

We are thinking of using a FeatherTwo ESC for the weapon motor. However we're unsure of the best way to reduce the LiPo batteries of 24V (the 'flat' voltage') to 33.6V (fully charged) (2 x 14.8v nominal) to the near 24V required by a FeatherTwo, and carrying an extra battery exclusive for that ESC is not the ideal situation for us. So we may need to scratch that and find a different ESC for the task.


the images
19hxzPiOLD.jpg2V881LRnUa.jpg

[Theo]

One of the highlights of my week is reading this.
Do you think it'll be ready by Manchester? You may be able to have it on static display if not, I'm sure the audience will love it (beats another boring wedge flipper in the looks department any day). I've not seen Niall mentioned recently, is he still working on it?

[Redirect Left]

One of the highlights of my week is reading this.

Happy to read, thanks.

Do you think it'll be ready by Manchester?

I'm not sure when that is. However I think we're still a few Sundays away from having something that properly functions. Especially in the weapon side of things. I think we're at a point where the driving will work reliably as soon as it is wired up now. I'm also unsure of Colins availability for such events at the current point in time. I'd be available without issue though, that much I can say. I'm not sure RE static displays, if that's beneficial overall for all involved or not?

I've not seen Niall mentioned recently, is he still working on it?

Niall is unfortunately no longer part of the project. It's back to Colin & Myself, who are certainly in it for the long haul!

[Redirect Left]

It's sunday!

Myself & Colin got together this Easter Sunday, and focused on electrics again.

During the week, Colin had worked on the lid for the ESC box, it's now got quite a strong lid to it that should easily do nothing more than be a little dented from something like an axe attack.

We started off by creating the cable that'll link the two LiPos together in serial, seeing as that needed two connectors on both sides, and last week we had a few issues getting the soldering going accurately. This week was greatly improved in that regard, using a soldering iron I brought up that's a little more powerful, only by 10W, but it made all the difference. Again, we used a gas torch to help melt the solder deep into the bullet connectors base instead of just around the edges to get a much better and hard wearing connection. We then moved on to all of the other places that'll later need wiring together, adding connectors so we don't have to do these as we come along to them.

We also setup the status LED to wrap up with, it's currently being fed through a seperate set of 3 AA batteries, which will be reduced to two with a small modification to the battery holder next week, as 3 slightly overly stresses the LED. The LED circuit is looped through the main link, to ensure despite its seperate circuit, it'll always accurately reflect the status of the bot being armed or disarmed.
The LED is shone through a hole in the lid of the ESC box, which gives a very vibrant and immediately obvious effect.

Next week, we're hopeful we'll be able to wire it up and have a proper test run. We've still to determine which of us will later go on to drive it, so we may setup a quick assault course and see who can drive it more accurately. We also need to work out the best way of firing the weapon, using a simple extra remote that is standalone with its own receiver, or an extra panel wired into the main transmitter on a long cable.

Todays not many images, next week, we'll make sure we get a proper shot of the lid of the ESC cover. It's shown here in the second image, with the new armed status light brightly shining through it.

gytCoJHQ=b.jpg0AXbldmPUq.jpg

[team death]

A day and half session on the Robot build this week....
Yesterday I decided to change the springs on the castor suspension hinges-
during testing they were too weak and were allowing the Robot to drop too
low to the ground, thier main purpose is to reduce the shock to the bodywork
when 110kg Robot is flipped 4 to 6 ft in the air.
Earlier in the year I changed the clutch on a 4x4 pickup truck and after looking
at the old clutch on Friday, I decided the springs inside were a perfect substitute
for the castor hinge springs.

Sunday-Unfortunatley Adam was unavailable this week due to a Tummy upset
and generally feeling bad so I set too on my own.
Fortunatley Adam had left some items with me last week so I could finish the wiring
off.
I started by re wiring the LED to the removable link, adding a suitable resistor to
the circuit and a new LED, I also reduced the battery to 3 volts and cut down the
battery cradle to 2 cells ( it fits much better into a reserved space ) .
After this I lengthend the motor wires from the fuses and tidied up the layout
with the aid of bolts and zip clips.
I sent a message to Adam saying I might take the Robot for a test run if there
was time but finishing the wiring took while 4 pm so I didn't.

I will try to find time to test the drive through the link for the first time-
next mid week (wheels off the ground) and if this is all good we can take it
to our cicuit first thing next Sunday.
Here's some pics due to internet busy more pics later
DSCN2104 (2).jpgDSCN2102 (2).jpgDSCN2112.jpgDSCN2110.jpgDSCN2109 (2).jpg

[Redirect Left]

Another Sunday has past us by, which means another update!

It's been a day of ups and downs, however we learnt from the experience - and that is what counts!

Before I arrived, Colin had setup the wiring ready for a test. So before we went anywhere specific to test, we plugged everything up, at this point only the batteries were needed, and ran an off-ground test just to ensure nothing silly would happen. It wouldn't try running away when the link was plugged in, unfortunately this did lead to one problem being spotted immediately. The motors had been wired in correctly, leaving one going forward whilst the other reversed. This is due to a simple forgetful mistake, in that in the past the motors were mislabelled red/black, however that was accounted for at some point in the past and fixed - but had forgot we did that so the motor was purposefully wired wrong under the assumption that was to do still.
Not to worry, the Cytron ESC is very quick to do a rewire and it was fixed within a few minutes.
Another issue shot up when we got it on the floor, now we were happy it'd maneouvre as anticipated motor wise.
The castors springs needed a little adjustment, as it ran one side of the bot tended to be on the ground a little firmer than the other, causing some one sided wheelspin. So a little tinkering was made there, to balance out the weight distribution a bit more.

After this, it was time to do a proper test for the first time, we packed up the bot and some tools, and headed for a secluded section of tarmaced area near the workshop. After noting the batteries at this point where about 60-70% charged, and we managed to get a good few minutes of usage out of it. Certainly more than the typical battle would last. We found out quite quickly that control was a little sketchy - unless you had perfectly positioned the controllers stick, there was a noticeable difference in output in the two motors, and driving was a little harder than we'd like. There was also a few further issues with the weight distribution, we'll try to see if we can correct this with more tweaking to the springs as we were still wheel spinning a bit on one side more than the other, although this may be related to the control issue. After a while, unfortunately but obviously, the batteries became a little drained to keep things moving along at a pace of value. We went to check up the bot - the batteries were both very warm, overly so. thinking nothing of it, we tried to have one last run straight line run to gather some speed up, however it just sat and didn't move. So we packed up and headed back to the shop.
Upon arrival, we decided to try to get around some control issues, by setting up a 'tank' style driving. Lifting the bots wheels off the floor, the batteries still had enough power to run the wheels, so we could test this new control method, and it seems to work. However, that is indeed all she wrote. With the batteries at this point being unable to spin the wheels, even off the ground.

We got out the charger, and set to work charging the now drained batteries for a later date. However, it's at this point we unfortunately found out that one of the batteries had been killed, my best guess is by the heat. It was so broken that the charger wasn't even able to detect it was a four cell battery, and only gave a total voltage (of 5 volts, on a 14.8v nominal LiPo!) and was unable to display individual cell data. We double checked and connected up to the other battery, and sure enough this one was seemingly in working order, with the charger correctly giving data for all four of the individual cells, and happily charging upwards. Whereas on the other, the charger just flat out refused to charge it due to a voltage discrepency.

I am thinking that the current battery holders are simply not getting any airflow, allowing the heat generated during discharge of the batteries to build up to damaging levels. I've included a picture of our battery holders below, so if anyone has an idea about this, and can confirm my suspicions, i'd be grateful. As if it wasn't damaged due to the heat, it may be a more severe problem than originally thought with the wiring or some other electrical part of the bot. We have a few ideas for alternative battery holders with much more airflow potential up our sleeves, if the heat and no airflow is the problem.

So all in all, today was certainly interesting. But we learnt from the experience, made some fixes already, the rest we will tackle on further sundays, here we don't hide the stumbling blocks. We share the entire experience for sure!

Some images, and some video taken during the test run. We managed to get up some good speed in parts, and we also know it spins well, so that's something.

I've cut down the video so the first minute is the most relevant to capabilities, and after that its mostly farcical stuff and spinning. Whether out of control, or intended - i don't know! It does however look like it spins with enough force to be somewhat damaging just from that!

All wired up and ready to go
IMG_20180415_121304.jpg
All packed up for its first time leaving the workshop - note that we decided to put the lid on top of the ESC box for this drive out, incase things got a little bumpy as the ESC is loose in the box currently although the sides and bottom of the case inside have been isolated with non conductive tape, just incase. We took a brush and a shovel so we could clear debris from the area, to help traction and make sure we didn't run into anything too nasty.
IMG_20180415_132235.jpg
These are the battery compartments. I suspect these are the cause of the overheating and battery failures, as there's very little airflow, especially to cool down the cells in the centre of the pack. Especially as the battery is 45C at 4500mAh so should be capable of over 200A sustained flow, and we shouldn't be touching even 100 of that.
IMG_20180415_152824.jpg
The first battle damage! - It was also running on the bar on top, based upon the scratch marks. So we're not sure if it was just bouncing upon it occasionally, or actually dragging it across the floor all the time.
IMG_20180415_154034.jpg

[team death]

A few problems here to iron out
What looks like bad driving was due to the transmitter not been calibrated
on the trim for one-when I pressed forward it was wanting to go left or right.
secondly-there is still a lack of traction for the wheels, resulting in wheel spin
and wasted energy-the castors may need to be just under the shovel or jaws
when fitted.
The batteries were not fully charged and so combined with the other problems
was not showing the true potential of the Robot.
We need to buy a new lipo battery due to it overheating-any heavyweight
Roboteers with advice on this is welcome ie what run time you should get
and what is the lowest you would let your cell voltage/overhal voltage go to
and what methods you might use to prevent the voltage from going to
dangerously low levels when robot is in use.

[Ocracoke]

Roboteers with advice on this is welcome ie what run time you should get and what is the lowest you would let your cell voltage/overhal voltage go toand what methods you might use to prevent the voltage from going to dangerously low levels when robot is in use.

Most ESCs these days have a LiPo function that automatically cut power when the voltage level is too low. The Cytron definitely has the facility to detect undervoltage (< 3.0v per cell) (https://www.robotshop.com/media/file...sersManual.pdf - Section 7b) but it doesn't cut it out, only on overvoltage apparently.

This had me panicked a little as section 7.8.2 of the rules (specifically pertaining to LiPo batteries) state the following:

7.8.2
Voltage Cut-out (Advisory)
The robot maybe fitted with an under voltage cut-out or alarm set at or higher than the battery
manufacturer’s recommendation to prevent the batteries from becoming damaged by over-discharge

You'll note that it is an advisory at the moment (as of the 2017 ruleset) so with this ESC and battery chemistry, you'd be OK but the only option then is to fit a secondary meter/alarm into the balance plug (https://hobbyking.com/en_us/hobbykin...arm-2s-6s.html) for each battery pack.