Featherweight vs Heavyweight build: Why is Featherweight better to begin with?

20th January 2016, 12:41

A little bit of background information on me: Back in 2001 with two friends and a electronics teacher, I designed a robot to enter Robot Wars. The project was so slow getting off the drawing board we eventually never entered the competition. We actually never built anything because our teacher disappeared for 6 months. Robot Wars then came off the BBC, and enthusiasm waned. Fast forward 15 years, I'm older wiser and do some small mechanical work on my car. Changing brakes, servicing, changing a catalytic convertor. My soldering skills were really good when I was younger and have done it an odd time since, so I think I have the basic skills required in terms of mechanical and electrical work.

When I heard about Robot Wars returning, I decided to get the old design out and see what I'd change. I then saw the deadline, and because the 15 year old design was very angular I decided the chassis would take too long to build. So I designed a simple pyramid/wedge shaped robot with a pneumatic flipper, along with some semi-automation provided by a Raspberry Pi which would also control a weight distribution system that sits inside the machine. I think it's a fairly simple machine to build given the time restraints they have set out. (This was before I realised there's a whole community that have regular events, which I'll be honest I'd be more interested in doing than putting my ugly mug on TV).

Anyway, in the Live Events forum Garfie489 suggested that I should start with featherweight robots first instead of a heavyweight. I checked the rules and noticed the massive gulf in weight classes between the two classes, and I thought that building a robot at a lower weight class would be far harder to do than building at the higher weight class as the weight of materials wouldn't matter so much, the chassis would be built to withstand more punishment, and would generally allow for quicker engineering.

So I'm curious, why is it better for a novice to start at featherweight rather than heavyweight?

**typhoon_driver** · 20th January 2016, 13:08

Cost mainly. A featherweight drive system can be built from cordless drive motors and gearboxes. A typical rammer can be built for around Â£200 to Â£250.

For a heavyweight you are looking at motors that cost Â£200 a pop depending on what you go with. They generally need a drive train manufactured as well which isn't an easy thing to get right first time and can take many attempts.

Moving them around is also a bigger pain due to the sheer weight and increase in size. A single person can happily lift a featherweight around and work on it at all angles. A heavyweight needs at least two people to move around.

Whatever route you go down you will make mistakes. A featherweight means that these mistakes will likely be a bit cheaper.

**Niels - Team K.a.L.M.** · 20th January 2016, 13:12

Why is it better to start of with a featherweight than a heavyweight...

pro's:

Less costly to start out with and learn. A basic mobile platform can be achieved by cannibalising 2 screwdrivers (12v or 18v), 2 esc's capable of handling 30amps, 1 LiPo battery and a transmitter, receiver. Screwdrivers comes with build in gearing and can be hacked easily to attach a wheel straight onto it. You're looking at about 200 pounds in total costs

Easier to handle. 13.6kgs can easily be picked up and set aside whereas a heavy will suck up space. Plus should a more experienced roboteer live nearby it becomes far easier to bring the machine to have him have a look at it.

Components like batteries, esc's and motors are more readily available.

Just as many events to use them throughout the year. (perhaps more)

**maddox10** · 20th January 2016, 13:37

If cost isn't an objection, then practicality is.

If you're alone, a heavy is not practical. It's 100 to 110 kg of armor, drives , batteries whatnot in an unwieldy package.

If you have teammates or helping hands nearby, it becomes another story.

Also, making parts. A feather drive is reasonably simple. Batterydrills can be adapted with simple tools.
A heavyweight drive is another kettle of fish. The least you need is a drill press and an anglegrinder

I feel feathers are just a better starterclass.

20th January 2016, 13:46

Thank you all for the advice, all of which makes sense. Currently I'm doing this on my own, I was going to tap another friend up to see if he wanted to join in but I've treated this as a solo thing just incase he says no.

While planning the robot I decided to get two 12v wiper motors from a transit van which have arrived today. With the talk of drill motors (which are smaller than wiper motors I think) I think I've already used 2kg of the featherweight limit!

**maddox10** · 20th January 2016, 14:38

You can do it a lot faster/simpeler, but with a pricetag.
There are a few firms that deliver working feather drives out of the box.
Ranglebox, Robot Power and Robot Market Place spring to mind.

ESC's are available from the same places.

Thread: Featherweight vs Heavyweight build: Why is Featherweight better to begin with?

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