Richie: The £50, 3 week Featherweight

[Rapidrory]

Hi, this thread is to document my recent Featherweight build. It's gonna be a retrospective build diary, as it's already been completed; I didn't have an FRA Forum account until this evening!

So first here's the story behind Richie: I found out that a featherweight event was happening at the Fleet Air Arm Museum, which is fairly close to where I live. Having not been to a featherweight event before, I decided to go and watch. I then heard it was free entry for roboteers (it wasn't, but never mind ), so I decided to see if I could build a featherweight for less than the entry cost of the museum (which is something excessive like £14) in the 3 weeks I had remaining once I got back from uni.
My dad had got halfway through building a heavyweight back in 1999, so I planned to use the ESC from that, and there were 'many' old drills lying around at home. Unfortunately when I got back from uni, I found that all the old drills had recently been chucked, and that the old ESCs were terrible and missing several parts... So the budget went out the window immediately as I had to buy some Argos drills, and the parts to build a new ESC, which all came up to £50.

First thing to be built then was the ESC. It was basically a clone of a Scorpion XL, reverse engineered through looking at photos of one on Google. The circuit took about 2 days to solder up the basics once the parts had arrived, and another two evenings to write the assembler for the PIC for controlling the device. The code was largely taken from my antweight ESCs, but had to be heavily re-written for greater precision needed for the higher currents.

p2P45K1.jpgfH2t3M7.jpg

It had big issues with noise, but that was solved with a few very large capacitors (not fitted in the picture).

Next step was to build the chassis. I live on a farm, so have plenty of heavy duty steel and other junk lying around, but I hadn't got any designs at all other than a vague plan to build a lifter of some kind, as that's relatively easy. So I had a look around for parts, and ended up welding stuff together, seeing if it worked, cutting it up and re-welding it... through this process of trial and error I ended up with the following construction:

rw1pD8D.jpg

One minor setback in all this was that I have no accurate scales; All I have is a set of bathroom scales, which are accurate to about +-1 kg, so all I knew at this point was that it was somewhere around 13kg... Seeing as I was yet to fit armour, I decided to lose some weight. I swapped the heavy lawn mower starter motor driving the lifter for the motor from a car tire pump, which dropped about 2kg of the weight, allowing me plenty of weight for armour. (updated lifter drive shown below)

Gu4dPUj.jpg

The last 40 hours of construction were somewhat hellish; the armour took waay longer to construct than I had expected (I was using 5mm HDPE from an old water tank found in a hedge), which was only finally finished at midnight the night before. Then I had to go and build the lifter drive circuit, which took until 3am, and then there were a whole load of bugs to clear up on the ESC which took me to about 7am... I still hadn't fitted any of the wiring, so bundled it all into the back of my dad's car (I had to get a lift as there was no way I could drive due to lack of sleep at this point) and somehow got it all together and working in time for the first fight.

v1DO5r4.jpg

It was hardly reliable; one of the wheels fell off in my first fight (though i still won it), the battery ran out in my second fight, and then the battery connector fell off in my third fight . On the second day my battery ran out on my first fight, nothing went wrong in my second fight(!), and my wheels fell off again in my third fight..

That being said, I still gave Beauty 2 a run for it's money on my last fight; Almost had it out, but Gimli's motors caught fire so they stopped and reset the match, and Beauty was in no mood for playing the second time I at least got that fight on video:

https://www.youtube.com/watch?v=DtLX...wp0tSCHzqPS4jQ

So yes, technically it is possible to build a featherweight in 3 weeks. However it came in substantially more expensive than a museum ticket (though still pretty pleased with £50), and with the 40 hours straight without sleep at the end, and all the late nights and pain the weeks before, I wouldn't advise it to anyone! I'm bringing it along to Burgess Hill for a few fights on Saturday; Hopefully it's slightly more reliable this time!

[Flag Captured]

Hold your horses everyone, we've found the solution to beating the Beauties!

Very nicely done indeed, I built HardWired I from scratch on a similar budget and timeframe for a college project, but it was nowhere near as good as this is - just goes to show, along with Bitza, that you really can do it all on a budget.

Do you plan on upgrading it at all at some point and entering it in the championships next year? I think with some new batteries and wheel fixtures to stop them falling off (I had this problem with HardWired I too...) this could be a real contender!
Especially like the height you get off the lifter too, could pick things up on the forks and with a little adjustment actually drop them out of the arena - could prove to be very tricky to deal with. Great machine overall!

[Shakey]

It may just be better to fit a small CO2 bottle and hose pointing at my drive system! :P

Also Richie is pretty impressive, and surprisingly well armoured too. Gimli put holes in the HDPE but never got through enough to endanger the parts under the armour. With a drive to match the lifter it should be pretty competitive.

[Rapidrory]

Yeah, the lifter was surprisingly good. It was the drive that let me down; It has very low ground clearance (~5mm) so keeps grounding out, especially when lifting something. The wheels are 4x60mm diameter circles cut from a sheet of silicon, which are then sandwiched between two steel plates... Sounds overly complicated, but they are actually just taken from a ticket dispenser (my dad builds ticket machines). Unfortunately these had disappointingly little grip in the end, and as soon as the wheel nut becomes a little loose the discs just spin on the shaft. I've since added a pair of bolts through each wheel to stop this, but they really need to be replaced with something about 70mm in diameter and more robust.

The ESC doesn't help matters as it has a problem of locking up one or both motors you go to full throttle to fast, (which is why Richie just spins round as soon as the fight starts in the video). It's a protection feature on the drive chips, so it's not damaging anything when it does that, I just need to add a throttle ramp into the code so it gradually brings the throttle up over quarter of a second or something... For the time being I just have to be less enthusiastic on the throttle.

My last major problem is it cannot self right itself when it's on it's side. I tried adding 'whiskers' to give it a little more sideways lift, but it's not enough, and I don't have enough weight left to do anything fancy like adding Razor style wings (though it wouldn't be too hard to do if I could)... Not sure how to resolve that one...

[Flag Captured]

To be honest with you, I'd be looking at upgrading to 4WD - I think it'll suit this style of machine a lot more, and no matter what you lift if you position the wheels right you'll always have your weight over at least some of your drive. Likewise there are other options for wheels like Banebots but they are a little expensive. Very good for grip though.

As for not righting on its side, perhaps you could add some side spikes to stop it getting stuck there? If you upgrade your batteries or replace heavier materials for lighter ones where possible, you could easily have a Razer style tension cord wing thing (which would be absolutely awesome if you were to do it) or you could make adjustments to your body shell to help it roll over on its own...

[mrsam]

I have to say, for a first time featherweight built to such a small budget and in such a small time frame this is brilliant. Having attended my first event in April ( FW champs) i know all too well the frustrations of your robot not being finished on time and then having a whole load of problems present themselves on site. I have to say i agree with Matt about 4 wheel drive, especially if your robot is designed to push others around with the lifter as 2 drills just won't do it. Also if you do enter any spinner events i'd bring spare armour if you don't have the weight to go thicker as it will get torn up, the forks at the front would also be spinner food so for full combat events like the uk champs it might be worth investing in a plate of Hardox or some other steel on the front instead. Most roboteers at the moment use either Banebots wheels or the blue ones from Bearing boy, not cheap but Banebots have plenty of grip although they do wear down quickly and the Bearing boy wheels can just have bike tread added.

Sorry to hijack your thread, all in all a great first robot

[Rapidrory]

Yeah, I have thought about upgrading to 4wd; would definitely be a much better solution. Obviously it'd require a fairly major redesign though, and a new ESC; don't think my ESC would support 4 motors, unless I went for the 2 motors with drive belts to the wheels approach, but that's not the simplest of mods... maybe tracks? Would also need to upgrade to lipos to free some weight (would save another 2kg), which I am planning to do anyway. However the ESC has no undervoltage protection, and it wouldn't be a trivial task to retrofit it...

As for the armour, I know it's a little on the thin side, but it's all i had time and weight for, and it was designed to allow a lot of flex so it can absorb impacts. I do plan to add more armour to the front at some point, for now i'll be sticking to the whiteboard events :P

Whatever happens, I'm not planning on making any major changes until the summer; Got exams to do, then flat out to get things ready for next AWS... After that I can get back to FWs :L

The only bit i've got to fix after all that is my driving; Having never really played video games, my use of a controller is pretty poor!

[Eventorizon]

*Watching the video thinking* "why is beauty 2 coming off the ground?" *Then it hits me :-D

I am very very impressed! The time frame, the budget, the handmade cloned ESCs, the overall feel of the machine... and having the 3 time UK champ wrapped round your little finger! (Well stuck on the end of your forks doesn't have the same ring to it.) Great little machine. Solve your ground clearance issues, perhaps upgrade some if the electronics and you should easily be able to compete at the champs next year!

[Rapidrory]

Well, we'll see; It was sheer luck that I got a good go at Beauty that time. He was playing for the crowds, so wasn't really fighting to win. After the match was reset, he was in no mood for playing and I was promptly chucked out the arena .

When I've done a proper rebuild with 4WD or tracks, and fixed all the major problems, and learnt to drive , then I'll see about entering the championships :L

[beast]

Well, we'll see; It was sheer luck that I got a good go at Beauty that time. He was playing for the crowds, so wasn't really fighting to win. After the match was reset, he was in no mood for playing and I was promptly chucked out the arena .

When I've done a proper rebuild with 4WD or tracks, and fixed all the major problems, and learnt to drive , then I'll see about entering the championships :L

carnt wait

(ahh it never had its no 1 driver )

have to stop show boating (Alan was that you driving) lol

and I know Beauty is very beat able but this year we just went all out for quick oota, except for the 2 losses which B2 was not driving right fixed by Kane, most figths were over in 6 seconds

[blazerbotics]

Was me driving and being nice!

[Flag Captured]

That's the thing - Beauty 2 and 8 are both beatable (as much as any machine) but the weak points just aren't something you can get at when you're sailing through the air bound for the outside of the arena haha


4WD would go great on Richie though, tracks would be cool but I'm not too sure on how good they are, can always try it if you wanted! I'd personally go for 4WD on the 4 corners of your machine, as best you can. Another thing too, no matter how you think your machine will do, I'd fully recommend just going to it when the time comes - this recent championships was my very first event and I've learned loads just from that alone! The more events you can go to the better I'd say - you learn a lot more about your robot when you're going up against varied types of machines.

In this recent champs, I learned what my main weaknesses were (drums, flippers, anything with pushing power) and now I'm working on counteracting that - likewise I found out that my tires actually wear really fast so next year I'll need spares. Also that I'm a terrible driver.

Best of luck to you though, it's a very solid machine and I can see it going far!

[beast]

I tried 4 wheel drive in B4 and 5 but came 2nd in 2010 back to the speed 900 drive now

[Flag Captured]

Oh, is that all?

The speed 900s work really well, it just depends on your design though I think. Beauty just launches something so the centre of gravity won't be changed by holding another robot up in the air like Richie would on those forks - can definitely see it sort of parading machines around the arena atop those! Besides, the speed that the Beauties reach means it'll have something out of the arena in seconds, which is really what you want!

HardWired 1 2 and 3 will all be running 2WD for the foreseeable future, I don't think 4WD would work well on any of those! Besides, it's more weight and if it won't add much there's not too much point. H2 and 3 definitely so, considering they're going to be tiny and there's no space for an extra set of wheels! H1 could do but I'm too lazy to convert it any more than I already have/will be doing haha

[Rapidrory]

Talking of parading robots around atop the forks, I managed to do just that in both my fights today at Burgess Hill I ended up in the pit both times though as I was shunted in by someone else each time I tried to lower an impaled robot in.. Note to self; bad tactic for melees :L

Richie was much more reliable today; The bolts through the wheels helped loads, and I managed to get it up to 10mm of ground clearance so the drive was much better. Didn't have to do any work on it between fights either despite being launched around, and all I have to do before tomorrow is recharge it (I only have one working battery atm, but at 7Ah it lasts pretty well).

The wheels are already quite worn now as I expected, but I have a few spare 'tires', and I plan to swap those wheels for something better before the next event; I'm currently thinking of using driven wheels at the back, with a belt drive to a pair of wheels at the front, as that's light and should be relatively simple/ reliable. 4WD would be very useful in this case; at the moment I have to lift another robot almost vertical to get the weight back over my wheels so I can drive (looks cool at least )

The ESC still needs more work on the code, but I'll do that when I can face tackling assembler again I'm planning to add a box filter on the signals from the Rx to give smoother control. It'll also act as ramping so the ESC shouldn't lock up as much.