New to the hobby- Where to get parts on the cheap?

Hello all,

I'm brand new to the hobby and I'm looking to build a robot and find some competitions to shoot for. I'm a mechanical engineering student at Embry-Riddle Aeronautical University in Daytona Beach, FL, and if I can build something for a reasonable amount of money to demonstrate I am going to attempt to start a combat robot club here and maybe, if all goes well, get an east coast intercollegiate series going.

Big plans aside, I have about two weeks before I'm on winter break. I have years of experience building and flying RC airplanes, I can weld, I've worked with carbon fiber and fiberglass before, etc. I don't have a ton of time or a ton of money to work with, but I'd like to build myself a robot.

I'd like to be able to compete, so basically the active competitions will dictate what class robot I attempt to build. I think I could do anything from featherweight to middleweight, depending on how much equipment repurposing I am able to do and what components cost. I already have a nice 1500W 24v power supply and an FMA powerlab 6 charger that can do all chemistries, a JR x9303 2.4g 9ch airplane radio as well as a 7ch 72mhz radio, all kinds of large 3s-6s lipo and SLA batteries, and other misc RC gear.

Basically, I just need a rundown on what is active where, where to source cheap or repurpose-able parts (motors, ESCs, wheels, chain, stuff like that), and I guess any other advice, tips, and resources you have.

In the future if I can build a demo bot or two I may come back seeking advice on starting a club or team, but that's down the road.
Also, I know this is a UK forum but I'm sure you guys can help at least partially, and if you know of an active US forum that would also be fantastic.

Thanks in advance,

Nick

Hey Nick.

http://forums.delphiforums.com/n/mai...gid=2008950046

Just a point, you'll almost certainly have to upgrade your Tx to a 2.4ghz set.

Cheers.

When looking at the rules, our rules are different to those in the states. Robot marketplace is a good start point to buy components over there. Could suggest loads of sources for parts but probably not much good to you over there. Best advice would be pick a category and then ask some specifics. Get a drive system going the think about a weapon for it after. There are some events going on in the us, best check on their forums for details though.

Harry,
I have one of each- The X9303 is a 2.4ghz DSMX radio, and the other is a futaba 7ch 72mhz. I didn't know if one was preferable to the other due to the large quantities of RF-blocking metal involved and the fact that 2.4 doesn't like that too much.

For that matter, I am a licensed ham radio operator and I can also use UHF frequencies in the 433mhz band for RC control as well if I wanted.

Thanks for the link to the RFL forum, I'll start there. Are there any other good forums out there?

It seems like a lot of the US activity ended years ago and there are only a few isolated events.

Mostly 2.4GHz is used purely on a safety basis. With robots like these safety is a big issue so radios that won't be interfered with and are fairly standard are high on the list. I know you have concerns over putting a 2.4GHz system in a metal armoured robot but it never really comes up as an issue even in robots that are just pure metal boxes! :D No idea how a UHF system would play in the setting but going with tried and tested is a good idea.

Got it, makes sense.

So I want to build something on the larger side, I'm thinking lightweight ~60lb class. That way I have power and mass to use it for other experiments than battles. I'm trying to get a feel for what size motors, batteries, and ESCs are needed for something of that size. Are drill motors or wheelchair motors better suited for this size? Some of the drill motors have massive stall currents, but what size ESC is suitable for regular operation?

I'm very familiar with electric power systems, but usually in aircraft, so I'm not sure where to start sizing things on the ground. Once I have a baseline example of a working setup I should be able to feel it all out myself from there.

If you want cheap, a featherweight class drill-box would be a start*. Using drill motors/gearboxes for drive is very cheap, and there's loads of robots out there that use them, or a modified version of. Plenty of those in the build diaries section, check those out if you want inspiration!

As for electronics, a 3/4s Lipo and a set of Botbitz TZ85A speed controllers, along with an Orange R620 receiver (or equivalent 2.4ghz one, if you have one) will get a machine up and driving about, paired with drill motors. Gives a nice base then to add weaponry, if indeed you want to even add any!

Also, reiterating what else has been said, rules are different in the US but it really won't harm to look at the UK rules as well - they're not THAT different but there's a couple of notable changes, like I don't think fuses for LiPo batteries are a requirement in the US, and the removable link can be tool-assisted over there, whereas it can't in the UK. Little things like that I guess.

Good luck with the build!

(*the only drawback is that I believe Robogames in the US don't do featherweights, the lightest they go for the non-insect classes are lightweights, but there's always Motorama and a few other events which do take featherweights...)

Great, thanks for the advice. I'll do some digging as far as rules and regs go, but yeah worst case I'll build a 30 pounder this winter for fun then do a 60 pounder or larger once I have additional funding to do it right. Except for the motors and ESCs, I should have everything already laying around the shop at home.

You can often get cordless drills for free or dead cheap when their battery fails. Try swap meets. Ask friends. The motor/gearbox combination is ideal for a 30 lb machine and works for a 60 lb one. There are lots of tutorials on how to lock the clutch and convert a drill gearmotor for drive. The output shaft is 3/8 UNF so you will either have to make an adapter for your wheels or buy wheels that take that shaft. For a first machine a relay based H bridge will get you going but a proportional speed controller is much better.

That's actually what I did today! I picked up two cordless drills on sale from harbor freight for $15 each today. They're good enough to get started and if I find some higher quality ones for cheap or free later I can always upgrade.

I can run them off of one of my lipos between 3-6s and I'm thinking of grabbing a pair of the bot bits 85a controllers to run them.

Outstanding! There are folks over here in the UK who sell wheels that wind right on to the output shaft in case you can't find any over there and don't feel like making your own. The screw that holds on the chucks is a left hand thread. Hold on to it once you get it out - they are hard to find.

RoboChallange no longer make their wheels. For a few robots they are gold dust as its the only wheel type they can take. You are better off going with something new or making your own rather than relying on something that is a: hard to get, and b: becoming outdated. (Yes it is possible to out date wheel technology)

It's not that difficult to make your own wheels. 3/8" nuts, old drill shaft, blowtorch, drill press, jobs a good'un.

https://www.youtube.com/watch?v=AcII...wY9c3yq40d6cAw

Thanks! I have a drill press back home that I can use, I can definitely make those. Thinking about just ordering some colson wheels as well with the kitbots adapters, and trying out both. For now I think it's going to be a 2 drive wheel, 2 freewheel bot but I may get another pair of drills or stronger motors and a chain drive later on.

Attachment 5055
Weighing in at a whopping 44.2 pounds, here is my initial design for my battle bot! Still needs a spinning drum on the other side for an active weapon, but the chassis, powertrain, and wedge are all done and ready to be built.
The chassis plate is 1/2" HDPE, the frame is 3/4in steel tubing, the wedge is 1/4in steel plate, the top armor is 1/4in polycarbonate, and the side armor is 1/8in steel plate.
Powered by two harbor freight drill motors on 10,000mAh of 22.2v lithium batteries, it should be powerful enough to hold it's own. Plans are to attach a spinning drum with nuts welded onto the outside onto the front with an angle grinder motor. This will (hopefully) fling the enemy robot across the arena, flip them, or tear into their armor.

The 30lb class is not very popular in the US, so I'm building for a 60lb class bot. If I need to add another two wheels and motors I will, but we'll see how this does.

Do you think the botbitz 85a ESCs will be enough?

The BotBitz TZ85's will hold. The drills is another matter. I suspect a lot of magic smoke in your future;

But the material choise is what I dare to call, old school.
We learned that polycarb isn't as good as HDPE as armor. Polycarb cracks , even shatters.
But HDPE isn't really the best for rigid structures.
Normal steel doesn't have a lot of use anymore in the arena. 1/8" normal steel is a dustcover, not armor. The equivalent in weight in HDPE is 1", and that is an entire other kettle of fish.
And I'm talking 30lbs, not 60.

A drum with nuts welded on. I forsee a lot of mangled nuts, and scratched paint on titanium armor panels.

Hahaha, I figured I'd get something like that. So how to I either shave weight to get to the 30lb class, or beef it all up without throwing thousands of dollars at it?
This only took me an evening, I can cook up another design revision fairly quickly.

I know what my ideal robot is like, but I am a little limited in funding, materials and tools available. I can draw anything I want, but keeping it affordable and buildable is another matter entirely. It feels like cost skyrockets if you aren't careful, but I don't want to build something that's going to fall apart if I drop it. Would it be better to make it smaller?

Unfortunately I have to force myself to push this to the side a little, as much as I want to get started ASAP, finals week begins in 3 days- I have to hit the books for a while.

Time*creativity*resources=robot.

If one of those is 0, you get the normal outcome. 0 robot.

Limited in funds, materials and tools. No easy solution to that, but a team can solve it at least for a part.

What class to participate?
The one you feel best with. I myself tried all except superheavyweights or the new beetles. over here, 220lbs heavies stay the cream of the crop, but feathers are very popular, and on the mainland Europe the 14 lbs Raptors are not unpopular. Ants ain't my thing. Neither does the team go on with those.

Drives. The TZ85's can do a lightweight. Driving a lightweight will need at least 4 normal batterydrills, or you'll have a turtle if you want to keep going. The TZ's can drive up to 3 normal drills each.(parallel)

Armor. What is the purpose of armor? Staying in 1 piece, or make sure the machine stays functional.

TIme is about a 6.5/10, creativity...I am great at making do with what I can get a hold of, and resources..I can dig and make stuff happen. I just got off the phone with a friend who has access to a machine shop with a CNC milling machine, 3d printers, welders, lathes, and I may be able to use another friend's CNC plasma table if I ask nicely.

Are there any go-to designs out there for lightweights or featherweights that I can build for my first one and then modify/upgrade as I go til I'm ready for something completely different?

Also, thanks everyone for your help so far!

So I just realized how cheap I can build a beetleweight, especially if I buy hobbyking ESCs and flash them myself with an ISP programmer. I think I may attempt that first, it's going to be much cheaper and there are a lot more competitions I can compete in. I can basically build a beetle for $40 of electronics..orange rx, 20a ESCs for $8 each, and some $10 motors. Where is the cheapest source of these "1000rpm" gearmotors everyone talks about?

Also, I ordered two botbitz 85A controllers for a larger bot- I'll play with those as well. I think if I get my ASP programmer I will be able to convert my own turnigy ESCs to robot use for $40 instead of $80...so power will become a non-issue.

Ebay is best for the motors. Although I think Kitbots sells them and mounts too.

You said 'Where is the cheapest source of these "1000rpm" gearmotors everyone talks about?'. Others can advise you better than I but you can get free motors, or very cheap ones, by picking up a couple of old electric screwdrivers at a swap meet or garage sale. As with electric drills, these go for little or nothing once the batteries go bad. They are slower than ones made for robots but they are rugged. First robots are often a learning curve; if I were you I'd build something in time for the next event near you, fight it, and then build a new one based on what you learned and using the electronics from the first one.

'Kitbots sells them and mounts too. ' Gearmotors from Kitbots are $12 each, plus $20 for a set of two mounting plates, total of $44.

John-The motors aren't horrible, but those mounting plates are pricey. I can make my own mounts no problem. I have a drill press, tap/die set, and countersink bits.

Harry- good point, I thought about that too- I'm just trying to see what the relative cost vs performance is for various parts and sources. I'll probably track down a few electric screwdriver motors also. It's funny, all of a sudden anything with a motor has potential to be a robot part. I have some brushless motors left over from airplanes that may turn into weapon motors eventually as well.

Only two exams stand between myself and going home to build something awesome!