First time builder question - is a three week build possible?

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MichaelG92
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First time builder question - is a three week build possible?

Post by MichaelG92 » Sun Apr 22, 2018 7:40 pm

Hi everyone, now that the TV show has sadly been cancelled I've decided to bite the bullet and build an antweight for AWS55 at the end of June, conveniently scheduled for after my final exams! My idea is a four wheel flipper robot, in a similar shape to Atomic but with sloped sides. The parts that I had in mind are as follows:

1.5mm polycarbonate armour
4 x 30:1 gear motors, wheels & brackets
NanoTwo V3
3.7V 200mAh LiPO Battery from HobbyKing
Turnigy TGY-306G-HV servo for the flipper

The catch is that because my exams don't finish until the first week of June and I'm unable to start building until they're finished, this gives me just 3 weeks to order parts and build a working antweight from scratch, although the robot has been designed and all the parts chosen and sourced. On top of that I have a full time 9-5 job, leaving me with just weekends and evenings to work on it. With that in mind is a three week build possible?

On top of that the things that I'm most worried about are:

- getting all the parts in time
- being able to screw the armour together and be within the weight limit (I have no CAD experience and don't have the time to learn right now sadly, but definitely plan to for the future)
- the flipper. My first thought was to bend one solid piece of polycarbonate, but because of my limited lack of tools and experience I'll probably have to screw the two bits together. But I'm worried this will compromise on strength against spinners

I don't have an engineering background so any help and advice would be greatly appreciated, although I do have a little knowledge of electronics and am fairly handy with tools. I hope to join you at AWS55 in two months time!

Michael
Michael - Team MG Robotics

Fledgling Surrey based roboteering team

James Bennett
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Re: First time builder question - is a three week build possible?

Post by James Bennett » Sun Apr 22, 2018 9:35 pm

It is possible to build something in less than three weeks. I built the first version of Plan B in a little over a week with no design other than 'it looks about right'. Just keep the design simple and leave plenty of space for wiring because wires are sneaky buggers and always seem to take up more space than they deserve.

You should definitely try to get the parts and tools you need in advance. It takes about a month to get something from China and you can end up paying a lot in shipping if you need it in a hurry. You might also want to check with Alex or Rory when the next set of NanoTwos will be available because they tend to sell out very quickly. You might find your robot is very slow with only a 3.7V battery. Most robots seem to use the 7.4V 180 mAh version, with this you will also need a balance charger, power supply, lipo bag, etc. Also, don't forget the little things like the right kind of connectors for the battery, acetate and a transmitter.

I have generally found that it is easier to make things out of multiple pieces of polycarb rather than a single complex piece. This is largely because I am really good at folding things and drilling holes in not quite the right place and it is easier to redo one part than have to start from scratch. The trick to not getting your face ripped off by spinners seems to be not to let them hit the edges of the flipper.

Anyway, good luck, hopefully I will see you at AWS55.
Team Risky Biscuit:
Plan B
Vanguard Mk 2

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GeorgeR
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Re: First time builder question - is a three week build possible?

Post by GeorgeR » Sun Apr 22, 2018 11:02 pm

You can definitely build and antweight in 3 weeks, but I would say there are a couple of things too look at.

Firstly I wouldn't recommend a 4wd flipper as a first robot, as they can be hard to get in under 150g, even more so if you don't have much time to adjust the design to save weight. Either a 2wd flipper or 4wd pusher is probably a better bet.
Secondly you really want a 7.4V "2S" LiPo battery, i'm not sure if a NanoTwo or that servo will even run on 1S, and if it does it won't be very powerful. Other than that your parts list looks good.

For holding the polycarb together I like to use nuts and bolts (M2 size are good), and others have had success with small wood screws or epoxy (Araldite).
As James has said, try and get the design as finalized as possible and figure out what you need to order asap, no point being held up by slow postage.

Good luck!
Team Zero
Zero - rambot - - Axiom - axebot - - Valkyrie - drum spinner
Vampire - horizontal spinner - - Orion - horizontal spinner walker

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DieGracefullyRobotics
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Re: First time builder question - is a three week build possible?

Post by DieGracefullyRobotics » Mon Apr 23, 2018 5:37 am

I tend to spend no more than a few hours on an ant so your timing is fine. Hell, if you turned up with the right parts early enough on the morning of an AWS someone could probably have something arena-ready before tech check closes, though I don't recommend that option, ha.
The trick is to be aware of your constraints. Simplify your design, don't expect too much in terms of how well you might do and you may end up pleasantly surprised. Most people end up doing better than they think first time out. Everyone worries about spinners but they are relatively few and far between and you'd be surprised what can stand up to them (and what can't!).
The things people always forget on a parts list are the more pricey bits. Transmitter and charging equipment, for example. But once you have those, they can be used for every robot you ever build.
I echo what's already been said about batteries and ordering ASAP. I would also say sign up to the event, do as much as you can to get ready, but if you're still a not quite there the night before, come along anyway. Show up early and someone should be able to help out. Or even if you just end up watching, being around the robots and asking questions gives you all the knowledge you need to carry on.
Best of luck! Newcomers are always very welcome.
Dave
Die Gracefully Robotics - Barely Even a Proper Team.

MichaelG92
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Re: First time builder question - is a three week build possible?

Post by MichaelG92 » Mon Apr 23, 2018 5:37 pm

Thanks for the advice all, it has been reassuring! I had the chance over lunch to look at shipping times for the places I want to buy from and I'll certainly look to order towards the end of May, maybe sooner. Some I can get away with putting off until after exams.

With regards to the battery I've managed to find a 7.4V 200mAh 20C/40C LiPO Battery from Component Shop, will that do the job? It has a JST connector which is what the NanoTwo has. It's also twice the weight of the previous one, so I've decided to follow George's suggestion of making it a two wheeler which will save me 30g of weight! I can make the upgraded version a 4 wheeled one once I become more experienced.

I had thought about the controller, I'm getting a Devo 7E. Mixing is another thing I'll need advice on, but we'll cross that bridge when we come to it. Need to remember to buy a charger with the battery and admittedly I keep forgetting about the acetate, can anyone recommend a good place to buy that from?

With regards to the M2 nuts and bolts, what do you screw them into? Do people use brackets? Or even pieces of HDPE as I've seen? And how do I go about hinging the flipper onto the rest of the robot?

I have no expectations Dave, just entering a working robot is enough for the first time! And if I don't manage to build it in time I'll definitely come and watch.
Michael - Team MG Robotics

Fledgling Surrey based roboteering team

Dazmund
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Re: First time builder question - is a three week build possible?

Post by Dazmund » Mon Apr 23, 2018 8:40 pm

I was thinking of using HDPE to screw pieces of armour together, but then I used small pieces 1mm polycarbonate. It is much easier to bend than 1.5mm, and hell of a lot easier to cut than HDPE. As for the flipper hinging, that varies between many a builder here. I made a hinge by cutting a strip of polycarbonate, bent it at both ends so it can be hinged, and screwed the flipper on top of it. I'll share a picture when I get the chance to do so.

As for three weeks, it's fine if you can commit a lot of time with that time, but going through the design process (internal and external) will take the longest, which made me stop and start to re-evaluated everything.

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GeorgeR
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Re: First time builder question - is a three week build possible?

Post by GeorgeR » Mon Apr 23, 2018 11:40 pm

That battery sounds just right, but if you're looking for alternatives the Turnigy Nano-Tech range are very popular, particularly the 180mAh version (although annoyingly hobbyking only sell them in a 5 pack now). You can't go wrong with the devo 7e, you'll see many at any AWS. Mixing is built in if you get a NanoTwo, but is simple to do with the devo if you use another esc.

For chargers the Turnigy basic balance charger is ubiquitous (but don't forget to get a 12v psu as well), or alternatively the Skyrc E3 looks nice and cheap, and doesn't require an external power supply. Also, don't forget a fireproof Lipo bag.

For sourcing parts i find ebay is great for small nuts/bolts, as well as polycarb and acetate sheet.

For attaching it all together I like to fold the polycarbonate so the parts overlap and bolt them together that way. For example, below is my axebot, which is primarily made of three bits of polycarb, a 1.5mm bit for the base/main chassis, and two 1mm bits for the armour either side. At the front and front/sides the base plate is folded up and each side panel is bolted on with 5 bolts, if you look in the red circle you can see the bent up base plate inside the outer armour panel. Towards the rear the side panel is bent under the base plate (along the green line) and bolted through the base (bolt not visible from this angle, but its roughly where i've added the blue dot).

Image

Hope that's helpful.
Team Zero
Zero - rambot - - Axiom - axebot - - Valkyrie - drum spinner
Vampire - horizontal spinner - - Orion - horizontal spinner walker

MichaelG92
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Re: First time builder question - is a three week build possible?

Post by MichaelG92 » Tue Apr 24, 2018 6:56 am

Making my own brackets out of 1mm polycarbonate looks like the better option for me, for a first build I’d rather have separate panels stuck together rather than trying to bend it all from one piece. Might do the same for the flipper.

How easy is 1mm polycarbonate to bend? What tools do I need?
Michael - Team MG Robotics

Fledgling Surrey based roboteering team

Derek Dudge
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Re: First time builder question - is a three week build possible?

Post by Derek Dudge » Tue Apr 24, 2018 7:39 am

1mm thick is really easy to bend and cut. 1.5mm is surprisingly tough to bend in comparison IMO but even 1.5 can be done without heating just with a clamp and a board edge or similar.

Ooh and maybe you would have done this anyway but just in case, perhaps learn from my dumb mistakes - if you have any small tab like bends to make, do it with a longer tab than necessary and cut it down after as getting a nice fold when you haven't got much to press against can be difficult.
My robots:

Third Law (antweight) - push/ram bot
Manticore (antweight) - hammer bot

MichaelG92
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Re: First time builder question - is a three week build possible?

Post by MichaelG92 » Tue Apr 24, 2018 12:04 pm

Ok, I’ll do that Derek!

Thanks for the advice everyone! I’ll post pictures and updates once I start building in June!
Michael - Team MG Robotics

Fledgling Surrey based roboteering team

MichaelG92
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Re: First time builder question - is a three week build possible?

Post by MichaelG92 » Tue May 22, 2018 6:54 pm

Had time over the weekend to put together a scale model in cardboard. Because of the size restrictions I had to make it wider and shorter than planned, and it ended up looking less like Atomic as intended and more like Rapid. But I'm still pretty pleased as everything fits inside, all the parts have arrived and once my exams are done I can start building!
IMG_3861.jpg
IMG_3861.jpg (36.3 KiB) Viewed 310 times
And I may even have enough parts and time to build a second robot for AWS55...
Michael - Team MG Robotics

Fledgling Surrey based roboteering team

MichaelG92
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Re: First time builder question - is a three week build possible?

Post by MichaelG92 » Tue May 22, 2018 6:55 pm

IMG_3862.jpg
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Michael - Team MG Robotics

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GeorgeR
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Re: First time builder question - is a three week build possible?

Post by GeorgeR » Tue May 22, 2018 11:20 pm

FYI, regarding the size restrictions, the robot doesn't have to sit flat on the bottom of the cube, diagonally is fine if you wanted to make it longer.
Not that there's anything wrong with your current shape (looks like rather like Anticide), but i know some people in the past didn't realise that was an option.
Team Zero
Zero - rambot - - Axiom - axebot - - Valkyrie - drum spinner
Vampire - horizontal spinner - - Orion - horizontal spinner walker

MichaelG92
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Re: First time builder question - is a three week build possible?

Post by MichaelG92 » Wed May 23, 2018 6:12 am

It’s good thing that it doesn’t have to be flat, as it’s 11cm wide otherwise the wheels and motors wouldn’t fit in. I’ve made a 4 inch cube at home and if I put it on it’s side it just about fits in.

It does doesn’t it? I didn’t intend for that to be the case, but I haven’t got time to change it now. Once I learn how to CAD the second version will look different.
Michael - Team MG Robotics

Fledgling Surrey based roboteering team

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