Hello again,

Lizzie has been put on hold because I will not have enough time to build and get enough testing done before Robowars 4. So I will be building a brick.

Robot name: Punk

Weight Class: Feather 13.6 kg

Drive : 4 x XU-1 Drill motors & Red wheels

Chassis & Armour: 12mm Layers of MDF milled and screwed together.

Weapon: Brute Force

Batteries: 4 x 2.2Ah SLAs

Tx, Rx: Spektrum DX-6

Control: Sure, why not?

I have it drawn up, and it's planned to weigh in at 12kg. The guts weigh in at 6.8Kg, so I will run it with only 4 motors to start with and then, if I build a voltage boost, I will run 2 batteries powering 6 motors. I'll post my drawings when I get home.

Last edited by Fish_in_a_Barrel on Sat Feb 02, 2008 11:31 am; edited 1 time in total

Probably a sensible decision, Hammer bots are one of the more difficult designs to get right and to come all the way from WA a conservative design for a first big event makes sense.
A lot of us old timers are chickening out and building wedges, I am a bit ashamed to be running Bane instead of Skeletor.

One of the early versions of Singularity ran 6 drills with I think red wheels. His MDF top armour wasn’t proof against Scoopie but there is no Scoopie to worry about any more.

I wouldnt try and run *6* Drill motors off an IBC, especially with 3 bateries in series.. (36v).

You are likely to blow the drill motors to bits with 36v,

melt the IBC - even at 24v with 4WD the IBC works hard - 6WD at 36v forget it

and run out of battery power.

When I.G. Mk1 ran 2WD at 24v with 2.3 SLA's it was usually crawling by the end of a fight.. at 36v, you have just way increased the current consumption, and then tripled it again by going 6WD

For an IBC powering drills, 4WD at 24v is about the most if will handle and even thats iffy if you stall them hard.

a 6WD 36v Rammer would be anything but a boring wedge, but you are going to need some serious batteries, ESC and Motors to make it hang togther
_________________
Great minds discuss ideas. Average minds discuss events. Small minds discuss people

Well the motors were going to be wired in series, like the batteries, so that the IBC wouldn't be working that hard.

If I had 8 motors then I would probably run pairs in parallel(18V per motor), but then I would have to seriously look at my armour's weight. I'm all for power, but I'm also familiar with the amps vs. volts argument, so I'll stick to series for as long as possible.

Possible fly in the ointment is one wheel off the deck results in no load therefore extreme revs which equal lots of back emf from un loaded wheel limiting power to drive wheels with grip.
Probably throw the wires out of the armature slots and jam the motor to.

Picture your bot with one wheel stalled and the other off the deck. Stalled motor has almost no resistance and other revving really fast.

I would just get some Jaycar motors with lots of turns and run them at 36 volts in parallel.



Unless you rig the drills up on some sort of load sharing suspension its doubtful if 6 is better than 4 as far as traction or pushing power is concerned, looks cool though. Difficult to do and keep it invertible.


Some as in 6 X YM-2776 Jay car motors with a CPU or Graphic card type heat sink and fan screwed to the std IBC heat sink would work fine at 36volts. IG was running a weapon as was KillBot and others that ran on 2 2.2 SLA’s 3 2.2”s Just running the drive should go the distance for a 3 minute match.

Well it looks like I'll do up something out of mdf and see under what circumstances it will lose traction. If it happens too often then I might go for 24v onto 4 wheels.

By the way what is the stall current of an XU-1?

74amps for the 12v RS-550 motors.
_________________
https://www.halfdonethings.com/

I guess I'll run it on 12V with 24V or 36V triggered as a weapon. That should get rid of those pesky flies in my ointment.

The frame is currently being made out of 3mm MDF sheets all glued and screwed together. This will probably be the frame that will be used at robowars as I won't have time to make another one between now and then.

The current design is 4 wheels with 24 volts supplied via 4 2.2Ah SLAs. The IBC will have at least 2 fans on it and I will do my best to run it gently.

I just picked up a nice digital camera today so there will be some photos as the frame is finished.

To save you the dissapointment, replace the 3mm MDF with at least 3mm polycarb or 3mm aluminium. MDF in that thickness is like building with paper... A decent ram from an opponent could see your bot broken in half

3mm Polycarb is pretty cheap from Bunnings, around $40 IIRC.
_________________
https://www.halfdonethings.com/

It isn't 3mm overall it is just being made layer by layer and will be glued together. The outside border ends up being about 20mm x 80mm. If i have weight left over then i will enhance my armour with some thin aluminium.

Will it cause radio problems if my aerial runs parallel to my battery cables?

Its too hard to tell. Some people who know the theory will say it will cause problems, but other people have built the same sort of thing might say that it still worked for them. Only real way to know it to build it and see if it works. Marauder used to have its antenna curled up in a ball in a metal box under the metal shell and it worked fine. We got the robot and tried the same thing and got no range at all.

When running a 36Mhz FM radi on Scoopy, we tried to improve the reception by moving the antenna mounting point away from the shielding metal arm out to the edge of the robot in "clear air".

The range halved So we moved it back to its nice metal shielded protected spot and stuck with that.

At least until I went for the 75Mhz PCM radios and eliminated all reception problems that way.

Radio theory tells you what should work, but there are so many factors that are hidden from sight, it seems a dash of experience and testing is worth a pound of theory.
_________________
Great minds discuss ideas. Average minds discuss events. Small minds discuss people

After spending a few years working with HF and VHF radios and antennas my experience is that radio/antenna theory is just that, a Theory . There are many rules, formulas and guidelines on how to design a good antenna for a specific application but all these are for designing transmitting antennas with the idea that if an antenna can transmit well then it should receive well. This is not always true.
Trial and error is the best way with these things. And don't discount an idea because it sounds stupid. If it works it ain't stupid.
_________________
Get Some!!!

Secretary of the Queensland Robotics Sports Club inc.