Bitza Mk2

[PJ-27]

Re: Bitza Mk2

Cheers Jamie. We had thought about extending, I think we'll get it driving and then see what we can do.

@Jordan, Good idea, I think we considered it and dismissed it, but can't remember why..... I'll think about it again as it should save us some space.

[PJ-27]

Re: Bitza Mk2

Got a little more work done. Received the drum from Jamie and made our own addition.

Also saved our space problem by angling the motor mounts at 45 degrees in the robot and moving the drum mounts further forward.

Also made a one way bearing for the fan motor. We used the ratchet system from a push bike rear axle and made the assembly with metal from some very rusty angle iron.



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[Mouldy]

Re: Bitza Mk2

Looking great pj! Nice to see some innovation, instead of off the shelf screwed together nylon robots. Glad the drum went to a good home, looks like it was made for it. Might be worth re shaping the front a bit so the drums more exposed though?

[RogueTwoRobots]

Re: Bitza Mk2

Yeah those blades seem like a perfect match, glad it's come in handy

[PJ-27]

Re: Bitza Mk2

Cheers guys!

Yeh the drum fits perfectly and look really mean with those big red blades! Can't wait to see it spinning.
We're moving the uprights to the very ends so the drum will be more exposed.

[billy breach]

Re: Bitza Mk2

What motors are you using for the drive? and are you using chain to connect the fan motor to the drum?

[PJ-27]

Re: Bitza Mk2

I think I mention their names earlier, but they're from Dewalt drills supposedly 300w each. The gearboxes are from the same drills.

Yes using chain, we originally wanted to use V-Belt drive so that it would slip on impact and not stall the motor but we had spare chains and sprockets from an old bike, plus you can easily make a chain to the length you require.

In our case this was very short, and even the shortest fan belts are too long (from Mini's for instance). We considered using the drive belt (or 2) from an upright vacuum cleaner.

Once we fitted to the one way bearing and remembered were using a 6S Li-Po on a 12v fan motor we decided that pulsing the motor and turning it off on impacts would be better than just leaving it spinning the whole time.

Sam with NST I believe just had the spin switch on Ch5 and just flicked it on at the start of the battle (also used chain drive, I believe it's one of the more efficient forms) but he ran into also sorts of issues like contacts welding on Relays...

[billy breach]

Re: Bitza Mk2

did you just fit a cog onto the axle from the drill gearbox then I take it.

Couldn't you just have some slack in the chain with a roller on a spring to keep tension..So on impact or being flipped the chain would just bounce up and down freely?

[PJ-27]

Re: Bitza Mk2

The cog took a little 'persuasion', we welded it on the gearbox shaft in the end.

We thought about using a sprung tensioner, but it's just something else to break. After seeing chains snap in other robots we figured the impact force must be pretty high so let's make this as simple as possible.
Plus given we are over volting the motor by more than double (and it's driving a 2kg drum, not a plastic fa any more!) and have taped up the vents on it it seemed more safe to not let it run for more than a few seconds. Plus it's from a written off Astra and I found a bolt IN it the other day......

[billy breach]

Re: Bitza Mk2

an astra!....good point then

[jonny]

Re: Bitza Mk2

Fan motors can take a surprising amount of abuse, you should be fine overvolting'em up to double imo.

[PJ-27]

Re: Bitza Mk2

Good to know, we have a back up too and hopefully we'll get some testing in before competition time.

Looking into using some HDPE for armour what do people recommend for grades? I've seen anything from 300 - 1000. I'm assuming it relates to density, so the lower the grade the less brittle, higher impact resistance, but would 300 be too low?

[gizz]

Re: Bitza Mk2

300, 500 and 1000 are the most usual ones if i recall correctly.
And it seems like 500 and 1000 are the most popular ones in this sport.

[dragonmaster_1]

Re: Bitza Mk2

The fan motors will take 24v no problem run dragonstrike at 24v never burnded one out yet. Snapped a couple of the drive shafts on EV warriors but not on the fan motor its been in the robot for 4 years now and still works fine just had a problem keeping the chain on.

[PJ-27]

Re: Bitza Mk2

Dan's been working away while at Uni and in the latest (and perhaps strangest) bitza build has turned a 56lb weight into the sprocket guard and middle teeth of our drum!

So far 12 hours on the lathe and 1 hour of hand cutting.