Newbie with a question

[Will]

Hi All!

I'm Will and new to this but I've been interested in building robots for years (I just had too many other things to do!) but I'm now at a point where I wanted to get involved in making something.

I've seen the general advice to newbies already - build small (lightweight seems to be the ideal category as a starter) and read the build threads etc which I will do as questions occur to me.

I've got a few ideas (but don't we all!) involving springs to store energy vs CO2 or other methods as I could see them being much lighter weight than CO2 in the smaller weight classes yet still give a very explosive force on release and be much cheaper to maintain. I note in the rules that they must be unloaded at the start of a fight which seems perfectly sensible for safety. Has anyone used these with any success? Or is it in the realm of half baked ideas that don't quite work in practice?

I'm in the northwest (St Helens) so if anyone is nearby I would appreciate seeign them in the metal/plastic/etc to get a feel for things in the metal; I'm even prepared to lend a pair of hands if anyone needs them as I appreciate getting hands on is the best way to learn and don't mind being a spare wheel in a team.

[Eventorizon]

Hi Will

As you saw, the best place to start is the Build Diaries and reading through the posts in the corresponding weight class. There is no point in building a Lightweight in the UK though as no one has an arena to run them. The most common starter classes in the UK are Featherweight, Beetleweight and Antweight, and once you get there you can build a Heavyweight.

Springs have been used in the past but not recently. They will pack less of a punch than pneumatic weapons but I can see them still having enough power to flip opponents or even toss them out the arena. It would be great to see a spring based flipper! You would also have the advantage of, pretty much, unlimited flips, where as a pneumatic robot probably has a max of ~25 flips in a fight (That is a total guess, but its limited regardless)

There are teams based in Leeds, Sheffield and Birmingham so you are not the only person in that area. I'm a little further north near York. I am sure some one on here will be close enough to give you a hand if you need it.

Good Luck!

[daveimi]

I'm in Blackpool if that's not too far. The main reason springs don't get used, even though they store a lot of energy, is because you need some sort of big and complicated way to re-cock it after firing. (which adds complexity, will go wrong when your getting battered and thrown about etc.)

Best way is think about the end result you want and then work on the simplest way to achieve it for reliability.

[Garfie489]

Regarding specifically the idea, it has been done before (Diotoir i believe was spring powered) however it does have its potential problems. Namely the slow return, and also being the least powerful of the common mechanisms.

What you get for that is simplicity, uniqueness, and ease of continued use (once built). Also its something you can just charge up and play, which is always a bonus when starting out. Only potential problem is because its so rare, it may be difficult getting help unless you post an idea and get it "double checked". But certainly at the end you could have a very serious robot which is easy to use and maintain.

Oh btw, you may be thinking of featherweight rather than lightweight.

[Will]

You're right I'm thinking of featherweight - at the small end of the scale where costs are small and everything can be built on one desk without needing any special lifting equipment but not too small to be a pain to build!

I'll try and find a build thread for Diotoir. It might help to see what others have done, even if the scale is different.

With regards the re-cocking of the spring, I was thinking a steel cable that can just be released and then wound back up, or perhaps designing it so it could be re-cocked faster using the entire machines drive system, like into a wall or something.

[jonophilpott]

Small and cost don't normally come in the same sentence 😂

[Will]

Well I was thinking, motors, gearboxes, batteries etc are all much cheaper if you're looking for small ones rather than big ones something to move 100kg around. All relative of course, I'm not fooling myself thinking this will be knocked together for £10 or even £100.

[R9000]

I doubt there will be a build thread for Diotior here. They're one of the oldest teams in Robot Wars, and I'm pretty sure anything they built was long before the days of this forum. They did have a spring-powered flipper though - looked to me like a lifting bar with a compressible suspension spring either side. Im guessing they used gears and some kind of remote clutch to wind it up, but I'm not sure. I think you'd be looking at the 2nd to 5th wars or thereabouts for Diotior in action. I don't know if the team are still active in any way.

[Will]

From the online videos they appear to use a pair of coil springs at the rear face of the flipper. A bit exposed but I guess they're pretty robustly mounted anyway.

Lots more reading / videos to do!

[daveimi]

Think it used a winch. The winch on my series 2 has a lever u pull to let it freewheel...

[Will]

Turning the idea sideways - does anyone use pneumatics to spin up a spinner? They seem a great way of getting a large amount of power easily compared to the electrical methods, allowing a near instantaneous spin up, with just a little motor to keep it spinning?

[R9000]

I imagine you'd exhaust your CO2 supply after only a few spin-ups, even quicker if you had to spend long periods of time without hitting the other robot. I'd expect the energy density of a lipo is more than that in the compressed gas at the temperatures and pressures in a featherweight. I think pneumatics are useful for getting things accelerated and moving over very short bursts, like flippers and axes. There are a few pneumatic grabbers too. Maybe if you had a motor to keep it going, but if you're talking something like Carbide's bar I think you might as well have just the motor. What's more you're now relying on two separate systems to activate one weapon. If one goes down, the weapon does too.

[Will]

I was thinking purely for accelerating up to speed, with a tiny motor to keep it spinning to overcome air/bearing drag. I probably need to do some calcs to see how much air would be needed to get a decent spinner spinning at speed and compare that to an appropriately sized motor.

[bigsi]

The latent heat of vaporisation of CO2 is 574kJ/kg the energy density of a typical LiPo is about 500kJ/kg - so not much to call it.
Unfortunately you need a container for the CO2, which for the relatively small amounts involved drives the density right down.

Not impossible - but probably not an advantage.

Si

[Liftoff]

Well I was thinking, motors, gearboxes, batteries etc are all much cheaper if you're looking for small ones rather than big ones something to move 100kg around. All relative of course, I'm not fooling myself thinking this will be knocked together for £10 or even £100.

How about pneumatics to cock the spring? Have plans for something similar...