First bot advice

Hey everyone,

been poking my nose around the forum for a few weeks now and figured it was about time i decided to try and build my own bot.

my names danny and i have no experience whatsoever except for a live of all things remote controlled and a huge love for the hit tv show we all know.

i have a bunch of old petrol rc cars that are spares and repairs and was looking to use the chassis and wheels to build a combat bot. Preferably a spinner but ill start off with a rammer featherweight.

could anyone give me a list of items i need to build a bot and any basics that i should know before starting?

im excited to start, seeing everyones build threads has got me so intrigued but my excitement far outweighs and electrical or engineering knowledge!

thanks in advance

Hey there, welcome to the forum!

In a basic 2WD rammer, you'll need something in the order of:

• 2x motors (something with gearboxes, I can highly recommend Gimson motors for this)
• 2x Electronic Speed Controllers capable of handling the current and voltage you want to supply, such as a hacked set of TZ85As
• A set of batteries that complies with the rules and can deliver the power you need. For what it is worth, The Honey Badger 2.1 runs off of 2x 2S LiFePO4 batteries wired in series to get to 13.2v.

You'll also want a transmitter capable of mixing (so the robot can be driven on the one directional control stick). You may also wish to invest in a set of electrical connectors such as the XT60 to make strong connections and your removable link and a LED with a resistor to make the power light with.

As for armour, the world is your oyster but I would recommend going with HDPE as a starting point. It is reasonably cheap and, when thick enough, can easily stand up to a fair bit of punishment in the arena. It can also be worked on with low speed woodworking tools. The Honey Badger 2.1 (my Featherweight) can attest to how much punishment HDPE can take.

As you note, do read through the build diaries to see what works and, more importantly, doesn't work. IC Feathers are very rare (I don't think I've ever seen one) and you'll need to know that if you do progress on to a spinner, some live events won't allow them due to safety concerns and others may place restrictions on how fast they can spin.

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Originally Posted by Ocracoke

Hey there, welcome to the forum!

In a basic 2WD rammer, you'll need something in the order of:

• 2x motors (something with gearboxes, I can highly recommend Gimson motors for this)
• 2x Electronic Speed Controllers capable of handling the current and voltage you want to supply, such as a hacked set of TZ85As
• A set of batteries that complies with the rules and can deliver the power you need. For what it is worth, The Honey Badger 2.1 runs off of 2x 2S LiFePO4 batteries wired in series to get to 13.2v.

You'll also want a transmitter capable of mixing (so the robot can be driven on the one directional control stick). You may also wish to invest in a set of electrical connectors such as the XT60 to make strong connections and your removable link and a LED with a resistor to make the power light with.

As for armour, the world is your oyster but I would recommend going with HDPE as a starting point. It is reasonably cheap and, when thick enough, can easily stand up to a fair bit of punishment in the arena. It can also be worked on with low speed woodworking tools. The Honey Badger 2.1 (my Featherweight) can attest to how much punishment HDPE can take.

As you note, do read through the build diaries to see what works and, more importantly, doesn't work. IC Feathers are very rare (I don't think I've ever seen one) and you'll need to know that if you do progress on to a spinner, some live events won't allow them due to safety concerns and others may place restrictions on how fast they can spin.

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Thanks Ocra, i've been checking your build threads so i'm glad you've responded as my first bots may be a little similar to yours!

I watched a few videos and I think I may have grasped the basics. I think i'm going to go for a HDPE shell in a wedge like fashion. I had intended to build a spinner but it seems as though they're not eligible for all competitions which is a shame as you mentioned

I have controllers etc from the nitro car kits i have, do you think i could reuse these to what i need or would it be best buying newer gear as they are several years old now so the reliability is in question.

I am hoping to use the wheels and the chassis from these. I'm going to go and get the box out later today and see what I have to play around with but being completely honest I dont even know what parts are what at the moment

What would you advise i aim for in regards to power? What amps, battery voltage etc

The controllers from bog standard RC cars, in my experience, are not up to the job. I wouldn't know if the controllers for nitros are up to the job (I have no experience with IC RC vehicles) but I can't imagine them being up to the job either given the pounding a combative robot takes.

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I had intended to build a spinner but it seems as though they're not eligible for all competitions which is a shame as you mentioned

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Nothing to say that you couldn't make it interchangeable... that is the plan for The Honey Badger 3.0 when I eventually get around to building it.

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I am hoping to use the wheels and the chassis from these. I'm going to go and get the box out later today and see what I have to play around with but being completely honest I dont even know what parts are what at the moment

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RC wheels work OK in my experience. The 110mm diameter off roader wheels I use on The Honey Badger 2.1 are reasonably meaty enough to give some, if not total, grip. However, keep them inboard as the softer plastic/rubber is prone to being ripped. You may find that the chassis won't stand up to the punishment though as is so you'll probably want to strengthen/adapt it to take heavy hits.

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What would you advise i aim for in regards to power? What amps, battery voltage etc

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As I say, mine runs at 13.2v but I am sure there are much higher voltages out there. I would have said 12v as a minimum was a good base point for a Featherweight. Amperage... depends on the motor and speed controllers being used. My previous featherweight ran sealed lead acid batteries with 2x 1.2aH batteries being "enough" to drive the robot but it was terribly weak.

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Originally Posted by Ocracoke

The controllers from bog standard RC cars, in my experience, are not up to the job. I wouldn't know if the controllers for nitros are up to the job (I have no experience with IC RC vehicles) but I can't imagine them being up to the job either given the pounding a combative robot takes.



Nothing to say that you couldn't make it interchangeable... that is the plan for The Honey Badger 3.0 when I eventually get around to building it.



RC wheels work OK in my experience. The 110mm diameter off roader wheels I use on The Honey Badger 2.1 are reasonably meaty enough to give some, if not total, grip. However, keep them inboard as the softer plastic/rubber is prone to being ripped. You may find that the chassis won't stand up to the punishment though as is so you'll probably want to strengthen/adapt it to take heavy hits.



As I say, mine runs at 13.2v but I am sure there are much higher voltages out there. I would have said 12v as a minimum was a good base point for a Featherweight. Amperage... depends on the motor and speed controllers being used. My previous featherweight ran sealed lead acid batteries with 2x 1.2aH batteries being "enough" to drive the robot but it was terribly weak.

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Is there any recommended minimum on the controller and receiver that I can tell if my nitro car controllers will be no good?

Interchangable may be slightly above where im at at the moment! Although i love the idea. Or maybe 2 bots is better *rolls eyes*

so ideally i’m looking for 15v+ to be comfortable and as for the batteries thats something ive got to learn for definite

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Is there any recommended minimum on the controller and receiver that I can tell if my nitro car controllers will be no good?

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The rules state what sort of frequencies are allowed for specific weight classes and they have to be UK FCC complaint off the top of my head. 2.4GHz is the norm though.

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so ideally i’m looking for 15v+ to be comfortable and as for the batteries thats something ive got to learn for definite

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Though a factor, I'd not worry too much at this stage about voltages and so on though the more you know, the better prepared you are. It definitely go through the rules for fighting robots (http://www.fightingrobots.co.uk/docu...uild-Rules.pdf) and it'll start to make sense as to what is allowed and what isn't.

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Originally Posted by Ocracoke

The rules state what sort of frequencies are allowed for specific weight classes and they have to be UK FCC complaint off the top of my head. 2.4GHz is the norm though.



Though a factor, I'd not worry too much at this stage about voltages and so on though the more you know, the better prepared you are. It definitely go through the rules for fighting robots (http://www.fightingrobots.co.uk/docu...uild-Rules.pdf) and it'll start to make sense as to what is allowed and what isn't.

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I'm almost certain that the controllers are 2.4ghz, hopefully they'll work.

Thanks for your help Ocra, i'll take a look.

My biggest concern isn't seeing what the rules are but more of what the robot needs within those rules, as it seems like it could be quite costly to keep upgrading parts, i'd like to buy a reasonabley good parts from the beginning.

If i purchased 2 different drills with the same voltage and battery size would the bot stil work the same? Got a friend selling a few second hand drills but one is dewalt and the other makita?

Slight change of plan.

im looking at buying items seerately so i can better understand the way things work than usig drills which have it all done for me.

i’m looking to purchase 2 brushless 18v drill motors with gearboxes. What batteries would i need to run these? Can anyone advise?

And also an esc that will work with these would be great!

I am new to this too but I think a 5s LiPo a 6s would be overdriving them.

The go to seems to be TZ85A often flashed for brushed but you need it as is. People use it with big bots so I assume it would be over powered for your application. There are plenty of options for programming them. Plus you could keep for larger bots. Plenty of Turnigy ESC to pick from if want smaller.

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I am new to this too but I think a 5s LiPo a 6s would be overdriving them.

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Not really, a 5S LiPo is 18.5v (3.7v x 5).

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Originally Posted by Ocracoke

Not really, a 5S LiPo is 18.5v (3.7v x 5).

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when i calc batteries i do it from when they are fully charged which 4.2 per cell

this could be help as well https://pp3d.weebly.com/getting-started

Ah, good point. I do wonder why then on my LiFePO4 batteries does the charger reach about 3.7v per cell and reads that when done but if you check it about 10 minutes later, it reports back as being the nominal voltage? (I'll probably make a separate topic on this later on to keep this one on track).

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Originally Posted by Deathly Hallows

I am new to this too but I think a 5s LiPo a 6s would be overdriving them.

The go to seems to be TZ85A often flashed for brushed but you need it as is. People use it with big bots so I assume it would be over powered for your application. There are plenty of options for programming them. Plus you could keep for larger bots. Plenty of Turnigy ESC to pick from if want smaller.

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Thanks Simon.

do you know if its easy ti program an ESC with no experience?

The drill motors usually have 1300mah batteries with them in drills, do you think that battery size would be fine to use i my bots?

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Originally Posted by Maxamuslead

when i calc batteries i do it from when they are fully charged which 4.2 per cell

this could be help as well https://pp3d.weebly.com/getting-started

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Ill take a look, thanks!

what is the main thing i’m trying to match up between batteries and motors, is it the voltage to be matched?

Quote:

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Originally Posted by Ocracoke

Ah, good point. I do wonder why then on my LiFePO4 batteries does the charger reach about 3.7v per cell and reads that when done but if you check it about 10 minutes later, it reports back as being the nominal voltage? (I'll probably make a separate topic on this later on to keep this one on track).

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Feel free to discuss in here, i’ll learn whatever i can!

LiFePo4 cells are 3.3V nominal and 3.6V fully charged. LiPo is 3.7V nominal and 4.2V fully charged.

Make sure your charger is "knowing" it's reading LiFePo4 and not LiPo.

Definitely says LiFe on the charger, I have to set the charger every time from LiPo to LiFe when I turn it on which annoys me oh-so-immensely but yes, good point, always check the charger first.