How to build a combat robot guide.

Hello all

I'm currently building a H/W robot with a group of kids at the school I teach at. As part of a sponsorship arrangement I have produced a guide to help teachers and individuals build a combat robot. I've attached the guide below, if you have time to scan through I would really appreciate any input via the thread or in a PM. I'm trying to make it accessible to a first time builder, so have missed a few areas out, if there's anything you think really needs to be in there please let me know.

Here's a link to the PDF version. If you would like a word copy please E-mail me at dgrant@Bradfield.Sheffield.sch.uk.

https://drive.google.com/open?id=0B1...Elta3V3VS1fTGs

The guide will be freely available when finished, so don't worry that I'll be getting rich from your input!


Thank in advance!

Can i forward this on to Greenwich University to potentially use for school projects btw?

Otherwise looks really professional. Theres a few tiny things ive seen after a quick read through, however those are more pedantic than anything (for example, i think its better if the link is on the positive side - or recommending drills for use in cheap robots due to providing alot of components for a good price).

Thanks for the feedback and absolutely feel free to pass it on, it still is in draft version though, the finished one should be complete in a month or two (there's some pictures missing towards the end). I'll put a link on here when it's done.

I'll make sure the link is on the positive. I have suggested drill motors, but some schools will have money to spend on clubs like this and VEX, Ranglebots, Banebots etc are easy options for a newbie.

If someone could double check the relay wiring diagram that would be great, think I got it right but still have to Google every time I come to wire one up!

Thanks.

Had a quick read through, and it seems pretty ace. Considering its for use in schools (or at least to teachers), a few notes;

Perhaps add M.R. Speed Squared as the demo bot for the full body spinner on page 5, this will be a more known robot to kids than Ringmaster, I don't believe that bot ever competed to any notable degree here in the UK. If you're wanting teachers to grab the attention of children with demos for possible designs they can do (if the teacher is going to give a choice) then I think M.R. Speed Squared will probably work better, as they'll have seen this one more likely. You could even add Nuts as one of the demo bots for that page, as it was quite colorful and memorable, again if the teacher is expected to give people in the RW club a choice of what the club aims for, might be one to use there.
May also be worth noting there that rambots are not permitted on Robot Wars, if that is the goal of the school to at least attempt getting on there as a few have done, you need an active weapon to get on Robot Wars, ram bots do not have these, Tornado added some little piddly weapon purely to get on the newer series. You can do the same, but then not actually really use it and stick to ramming to get around it.
LiFePo4 might be worth adding to the alternative batteries, they have good density, longer lifetime (in a fighting robot, they'll probably get damaged well beyond a lifetime for one), they're also inherently magnitudes safer than the LiPos you focus on. I'm not entirely sure if focusing on LiPos is a good idea for school built robots to start with, mind.
Might also be worth noting the expected amount of £££ required to build each type of robot. Bare in mind that everything on the TV show that proudly annouces how cheap it was made, quickly ends up shredded. So with robots, cheaper is often not better if you want it to hold any weight in a battle.

That is a good guide though, and in the future you could easily adapt as a quick guide for all, rather than school club focussing.

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If someone could double check the relay wiring diagram that would be great

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the relay diagram appears to be fine :)

I think you've made a really good start with the guide.

One thing to remember when you write technical documentation is that people have a diverse amount of knowledge so you have to assume they know nothing and every time you introduce a new concept, term or acronym then consider adding it to a glossary. An example of this would be the different types of connectors discussed.

Also if I was starting a club from scratch I would find it really useful to have a bill of materials to accomplish a specific task and example components to use e.g. removable link, fuse and power light

Hope this helps
S.

As an FYI I'm fairly sure it's actually in the rules that the link has to be on the positive side, other than that though nice work!

Just one pedantic thing. On page 5 the robot that you've used for your example of a rear hinged flipper is Eruption not Explosion.

well Team Invade does also have a featherweight which is rear hinged flipper call Explosion so.

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Originally Posted by Maxamuslead

well Team Invade does also have a featherweight which is rear hinged flipper call Explosion so.

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Well that isn't the robot that is pictured as the example so...

In general a good guide, but I noticed a few things:
-Electric lifters are missing in the weapon designs. Stinger (from bb) or Panic Attack could be used as examples.
-There are brushless escs that can change directions. But if you want to use bl-motors for anything else than a spinner, you got to know what you are doing (=not for beginners).
-You should mention that banebots gearboxes are not metric, so you need imperial tools for them
-The REC gearbox would be another (metric) alternative
-hdpe is a very good material for armour. I´d pick it over polycarbonate any day.

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Originally Posted by ralf.96

-The REC gearbox would be another (metric) alternative.

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Ish it more of gibson/drill gearbox hybrid. Gimson GR02 style construction with a standard drill motor shaft but still very much worth a mention.

FYI from a wiring diagram perspective the link should be arranged like the fuse is along the wire. Right now if built as it reads the robot can never be turned off.

"Having a robot that can either run inverted or has a self-righting mechanism (SRMech) it strongly advised." Or ability to self right via the weapon.


"Brushless – Brushless motors require brushless ESC’s. These cannot change direction when in use, but can be set to run in either direction when being wired. As with brushed ESCs find the maximum current draw for the brushless motor you plan on using, at the voltage you will use, and buy an ESC that exceeds that amperage draw.
a. To reverse the direction of a brushed ESC unplug any 2 of the 3 wires and swap them around."

This section is incorrect, brushless ESC's can be made bi-directional relatively easily (SimonK flashing). Also you CANNOT just swap any two wires for a brushless motor to reverse. [SNIP:I went crazy]

You should probably mention the common route of flashing a brushless ESC with SimonK for drive.

Fail safes are controlled by the receiver not the transmitter, the transmitter is used in setting them on bind but ultimately failsafing is the actions the receiver takes when the transmitter is removed from the system.

You should mention LiFePo4 as one of the alternate batteries (A123's are an example). Get most the fun of LiPo with far less of the fire.

If you're mentioning brushless motors for drive you should mention that it is generally advised to aim for a much larger wattage than you expect to need as this greatly improves low end control.


"Hardox - Thicker sections are often used in bar spinner's weapons" Just drop the 'bar' part of that, most spinners these days regardless of type (At least not the drum varieties) are hardox. Should probably mention that this is far more suited to those with access to a CNC water or plasma cutter or willing to outsource, manually working hardox is difficult and time consuming requiring higher quality tools than normal steel. Also a pretty much no for tapping in hardox.

EDIT: A GR02 is still a drill gearbox inside. I used to repair mine with innards from argos drills.

EDIT 2: Could probably just mention the regular good old 'check the wiring for loose/intermittent connections' in troubleshooting.

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Originally Posted by Shakey

This section is incorrect, brushless ESC's can be made bi-directional relatively easily (SimonK flashing). Also you CANNOT just swap any two wires for a brushless motor to reverse. The middle wire of the ESC and the motor must always be connected, then you can swap the outer wires to change direction. Wiring a middle to outer can easily lead to an incorrect arrangement leading to cogging (With no potential to move past it) and potentially ESC death.

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You can indeed just sap any two wires in a sensorless brushless setup.

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Originally Posted by ralf.96

You can indeed just sap any two wires in a sensorless brushless setup.

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Yeah just made me go double check, I now have absolutely no idea where that came from in my head. On the plus side I've had a self enforced brushless wiring convention in place for a while now that has been super helpful. :P

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Originally Posted by Shakey

A GR02 is still a drill gearbox inside. I used to repair mine with innards from argos drills.

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fair enough so in there any reason why people are willing to spend silly money on them.

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Originally Posted by Maxamuslead

fair enough so in there any reason why people are willing to spend silly money on them.

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I don't remember them being crazy expensive, the mounting points were very nice to work with.

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Originally Posted by Shakey

I don't remember them being crazy expensive, the mounting points were very nice to work with.

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I looking to buy some before i got a pair of REC and they reach £90 for two IIRC before I completely bailed on them.

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Originally Posted by Maxamuslead

I looking to buy some before i got a pair of REC and they reach £90 for two IIRC before I completely bailed on them.

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Yeah they would be expensive buying them used now they're out of production. They were only ~£30 each when they were being made, fairly reasonable price.

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Originally Posted by Shakey

Yeah they would be expensive buying them used now they're out of production. They were only ~£30 each when they were being made, fairly reasonable price.

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Yeah just find it strange when you can get similar new gearboxes for same or less money

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Originally Posted by Maxamuslead

Yeah just find it strange when you can get similar new gearboxes for same or less money

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People build around a specific motor and once that motor is out of production they rely on buying them used off of people for spares when they break. As time goes on supply dwindles but people still need ones to replace as they break, so the power in negotiating a price goes to the people who have the few available spares and they can charge a higher price. Simple supply and demand.

Same thing happened with Speed900's. It's why i have a rule to never build a robot around parts I can't buy new.

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Originally Posted by Shakey

It's why i have a rule to never build a robot around parts I can't buy new.

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Good motto to build by

How is this coming along?