Build Diary and some questions that may appear - BW/MW

[Eventorizon]

Just buy a BEC, the are only £15 or so and will be much more reliable than a custom one.

Great machine though. Very, very tight!

[Merkabah_PT]

Thank you for the compliment, that really means alot to me! This is my first real robot following rules. I have built others when i was younger but they were mostly abominations made out of scraps.

I will not be competing, so this robot will be more like a expensive home made toy. But when i have the money, i will have to order a batttery to power the weapon i intend to add, so i might follow your advise and add a UBEC to the order, just 7.5‚ (£6.5).

Atleast if the chance to compete some day appears, i will already have most of the gear.

[Merkabah_PT]

After 1 hour of searching for the drivers of the programming cable for Win7 x64 and tinkering with T6Config, i finnaly got my mixing working right.

I was so happy that i started to chase my dog through the house to get used to drive with one stick. The robot was really really nippy, but the speed started to drop fast, and after 2 or so minutes the robot barely moved.

I have to wait until 6 in the afternoon to get my multimeter back and check power consumption, but my motors stall at around 10A, so worst case the two sould draw 20A. By my calculations i got this:

Battery outputs 1.8A for 60minutes
Motors draw 20A (worst case scenario)
20A is greatter than 1.8 12 times
Battery duration will be 12 times less
60/12=5
Even with the two motors stalled, the baterry should last 5 minutes.

So, i thought that the problem should be that the battery wasn't fully charged.

My baterry is a 7.2v 1800mah ni-cd pack and my charger outputs 1000mah, so i use this formula e saw on many RC forums to calculate charging time:

1.4 x (baterry mah's) / (charger ma's) = charging time in hours

1.4x1800/1000=2.51

2h30minutes of charging time.

Is this correct or should i leave it charging more time?

[Bodge Job]

i would charge it a lower current for longer, the higher the current the less the battery absorbs, and depending on the quality of the battery it may require event longer, i would sugests trying it at half that current if you can, but if your charge cant do this, then you may have to try and get a better charger. cycle charging may also help (discharge it completely at a low current, and then charge it up again at a low current.

NiCds also have a memory issue, so before most charges (when you can) try and discharge them first.

[Merkabah_PT]

Thanks for the reply Alexander.

I have read, as you say, that charging at lower current is better. I only have this chager, and can't afford a good/proper one.
This one was bought along with the baterry pack, and the guy from the webstore told me it was completely compatible. But to me, it looks like a regular AC to DC converter, not a real charger.

It has a led on top, if i connect the charger to a outlet the led lights green, but when i connect the baterry it turns red. I have sent an e-mail to the store to ask if the led turns green when the charging is done, but they haven't answered yet.

The battery is charging right now (started at 15:00), i will wait 3 hours (18:00) to see if the turns green. If it doesn't i will wait one more hour and then disconnect no matter the result.

Then i will do some test:
-start a chronometer and run the robot until it dies;
-use the multimeter to see how many amps the motors draw while driving around.

Just for reference, what battery amperage people usualy use on feathers with two drill motors?

[Bodge Job]

My first RC car charger was like that, it should turn green when its done Normally those chargers will discharge battery's when unplugged from the walls. And if it doesn't go green after a few hours, you can try to keep it charging, but keep an eye on it, make sure it doesn't get too hot. and if it doesnt go green after like 5-6 hours i don't think its ever gonna go green. If its advertised as a charger though it should go green, and float charge when its done (which means it doesn't over charge them).
hopes this helps!

[Merkabah_PT]

Yap, you are completely right.
During the charge, i noticed that the led might be changing color and around 3h in the charge it was almost green. I waited a total of 3 and a half hours so it was solid green.

Tested the robot for about 6 minutes and the speed stayed about the same, just a small drop.
Also tested the mixing and it's great, the PC utility is very simple and intuitive.

Small video of the test (my dog gets really confused and excited with RC things ):

[Merkabah_PT]

After almost one hour, 50 screws and an hell of a pain on my hand/wirst, Primogenito is finnaly fully disassembled so i can paint the steel parts.







Electronics:


All body parts:


Cleaned the rust with lemon juice (i don't have tools to unscrew the nuts at home):





Tomorrow at the workshop i will sand every thing and paint it. I am undecided between black or dark green, what do you think would go better along with the white HDPE?

The gears on the first stage of my planetary gearboxes is plastic, so i will see if the metal gears from an old drill are the same size so i can replace them.

[Max]

It all looks very good- I would go for black paint

[Merkabah_PT]

Metal parts all painted, phase one completed. And i also discovered that using relays and servo electronics Primogenito actually as some speed control.

Phase two will be building the weapon, a vertical spinning bar. Already have a generic 550 motor and steel for the bar but need to find or buy two pulleys and a belt.
I also have an old electric screwdriver that i could used to power a lifter, but since this is a showbot, the spinning bar will be better.




I found some old motor on my garage: 2 drill motors, 2 wiper motors, a wiper motor without the gearbox, a really big 24v wiper motor from a truck and a 24v 250w scooter motor. I am thinking about building a Backlash/Nightmare FW replica. The scooter motor to power the disk and for the drive the drill motors or the wiper motors, but i will leave that for after i finnish Primogenito.

Backlash v5


Nightmare v4