Time to pick your brains!

[PJ-27]

Hello,

Having recently decided to build our first fighting robot we actually have several questions! So hello everyone, I'm here to pick your brains!

Firstly, we currently have 2 windscreen wiper motors and 2 12v SLA batteries. My assumption was that these were normal to use in the featherweight world, but they weigh a ton! So should we really be looking at the next weight category? Also FW's look like they are brilliantly engineered, maybe a little beyond us......... (lot of power, tiny size!) so would aiming to make a Lightwight be more sensible, not that I'm knocking LW builders....

From looking at speed controllers they seem expensive! But that is with a 15 - 30amp rating, so am I right in thinking that 2 motors rated around 80w and a 24v system would have 6.6amp draw? Plus the weapon of course.... Would any speed controller with a 10amp rating do? What makes the Electronise, Scorpion and Sabretooth speed controllers mentioned on here special?

Finally where can be a good place to get some of the required safety equipment?

Thanks,

PJ

[typhoon_driver]

Re: Time to pick your brains!

Welcome to the forum. Your best bet is to first read through the other posts on the forum as those will most likely answer a good number of your questions.

Featherweights and heavyweights are the only two weight categories that are usually built to in the UK. There are a few middleweights kicking around but you will struggle to find any competition. Lightweights haven't been big ever. Ants exist also but I'm not up to date with the state of play with them.

Your wiper motors and 12v Slas would have been standard tech around 5 or 6 years ago however times have moved on as you said. The most common motor/gearbox combo to use is a cordless drill motor and gearbox (easy enough to get a hold of and cheap). Slas are old tech as well. You'd probably be better getting some nimh instead. You can still use these parts to get a running chassis and get the basic ideas in your head though.

Speed controllers are an interesting topic when it comes to robots. Generally you will need to use a 15A controller at least with a drill motor or similar. Sure if you do the basic sums a 6A speedo would do the job but sadly we live in the real world. Motors draw huge stall currents at start up, quick reverse or if you are riding around with not only your own machines weight but another feather or two on top. You will usually find that controllers on ebay marked as 10A are fine in hobby sports (ie hobby amps) but because you will be stressing things to their extremes you need to parts that are a bit more industrial in nature. Those 3 speedos you mention are battle proven in many a machine and thats why they are recommended. Simple as that.

My advice would be to build a basic rammer first and then attend an event and speak to the guys there and see whats what. You will learn far more from that one experience than you could ever learn on here and chances are there will be an event near you.

[PJ-27]

Re: Time to pick your brains!

Sounds like good advice! Thanks for the pointers. We'll head over to an event soon then.