The other problem with drill gearboxes and large wheels is that the steel gear carrier pins can shear off - there are usually only three pins per stage and they are not good quality. Once a pin breaks, the gearbox self-destructs.
RobotVersion2.png After thinking about what I could do with the disc in the design I already had. The solution I came up with was to replace the disc with a drum or bar(like that on Trouble Starter) I was wondering how difficult it is to build a drum and also how many motors will I need to run it off and where they should be placed to stop balance problems.
I have posted a basic design idea, the wheels will be at the back allowing for it to be invertible.
DSCF5295.2.jpg Here is a sketch of what I thought the new robot design might be. I had a feeling it might be a bit too similar to TS3, what do people think? The plan is to have it come to a wedge at the back and then for it to be small but will a lot of heavy armour (only thing is I can't weld at the moment so will be held together by screws/nuts/bolts/whatever seems to work)
TS3 is an excellent design. I wouldn't worry about your design looking too much like TS3, all bots have similarities. The main improvement to that design is to enclose the weapon less and have it project as far out the front as possible. Having the top and bottom panels come out to the front is a bad idea as they can easily be bent and catch in the beater or 'high side' the bot and stop it moving. Making the beater diameter as large as possible and having it stick out as far as possible helps your bot attack other vertical spinners before they can contact your bot.
As well as TS3, have a look at Conker 3 and my own vertical spinners here: http://www.robowars.org/forum/viewto...=74&start=5955 - not quite your design but there will be ideas you can adapt.
I am planning to use two 12V drill motors and the 30A ESCs (linked near the beginning) for drive. How do I work out what battery pack I need to use?
I tried this calculator: http://architeuthis-dux.org/torquecalc.asp
but couldn't get it to work.
In what aspect?
(assuming we're saying LiPo chemistry here)
Capacity, I'm sure that plenty of drill-based machines use about 3000mAh for their drives, and 3S should give you that 12v. Or you could go 4s for a bit more speed, if your ESCs will take it.
I used a 5000mAh 4s in my very first machine, which ran drills and that seemed good enough for all intents and purposes. That sort of capacity is overkill though, I will say...
Are any brands particularly good/reliable? Also how high could I overvolt a 12V motor before it is likely to cause damage? And finally I get that 3S or 4S is number of cells but what does the mAh mean in terms of performance?
At this point I'm leaning towards 3S as it will be lighter/smaller giving me room/weight for another battery for the weapon. What do people think about going down this route?
Team RCC uses mainly Zippy and Turnegy for the robots. Not to expensive and easy to replace.
Concerning overvolting. Rule of the tumb is 1.5 times nominal voltage.
Meaning you can feed a 12V motor 18V without blowing it up before it does any real work.
But that same motor can easely burn out with 12V if it is worked hard enough.
mAh is the storage capacity of a battery. A 3S 2000mAh battery contains 11.1V 2Ah= 22.2W of power. The C value is what the battery can deliver in a short time without blowing up.
With LiPo that can go up to 130C, meaning a 2000mAh can deliver the whopping 260A (on 3S 2800W+), but will run empty in about 15-20 seconds.
Most decent LiPo's are 30-40C
Using 3S on a 12V motor is not a bad idea if raw drivepower or speed isn't what you need.
We use a dual battery setup Caliope. A 5S 65C 5000mAh for the weapon, and a 3S 2200mAh 30C for the drive.
Just be careful not to get confused between Watts and Watt Hours. Mario's figures above are all in Watts, so that 22.2W of power is actually 22.2Wh. Which means it can give that much energy for an hour. It can supply a lot more power than 22.2W to you system but for a shorter amount of time.
As your unsure of what capacity ratings etc mean, I would recommend using a different battery type for now until you have gained some hands on experience of using and charging batteries before moving directly to Lipos. It's a curve we have all done here as Lipos are a fairly new chemistry, and not as fool proof and safe as other types available. A lot of people now take lipos for granted and recommend them to everyone - however I personally advise caution even to the more experienced roboteer's.
I'm currently trying to sort out the drive system of the robot. I need wheels (Banebots probably) and a way to attach them to the drill motor. While having a look around I found this in which he uses a 3/4" hex hubs with an internal 3/8"UNF thread, does anyone have a better method than this or know where I can find some of the hubs/nuts?
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