Bitza Mk2

Finally started to get some work done on Bitza 2! Unfortunately (fortunately?) Dan is off to Uni in a couple of days so this'll be it in progress for a while.

Axle and Drum Shaft fitted. Wheels and teeth just resting in place:

http://i1228.photobucket.com/albums/...ssemblyTri.jpg
http://i1228.photobucket.com/albums/...embledSide.jpg
http://i1228.photobucket.com/albums/...sembledTop.jpg

The side frames:

http://i1228.photobucket.com/albums/.../SideFrame.jpg

And a component mock up:

http://i1228.photobucket.com/albums/...components.jpg

We've gone for the exoskeleton design again since it proved so strong at the UK Champs 2011.

Looks evil! :shock:

Seriously looking awesome. I'd love it if you guys didn't paint it and make it pretty. Leave it as is + armour etc, and rename it Scrap-daddy or The Devil Himself or something! People are always making their bots look mean by putting flames and what have you on them. This thing already looks far more terrifying than any skull-covered machine. :twisted:

cool! what are the teeth on the drum made from?

Oh don't worry we're not making it look nice. We want it to look like a scrap yard came to life. The scoop (not on yet) is some rusted metal, so it's going to look really rustic come the end.

We don't really know what the teeth are, but they are some sort of steel with what I assume a tool steel on the tips (which are seriously sharp). Dan picked them up at a car boot for 50p!

nice, i'm sure i've seen them on something i just can't remember what

Apparently they are something to do with working wood? I don't know what, unless you has some wood you needed destroyed!

Looking good, what motors are you planning on using?

Mabuchi RS-775WC-9013, 300w watts apparently...

Got them from a couple of Dewalt drills Dan bought for 50p........ again!

Be able to do a bit more since Dan has been back for a couple of days. Finished up the frame and then parked Dan's 4x4 on it to see how strong it is/ straighten it up (photos to come soon) and then spent a long time scratching our heads about how on earth we would mount stuff inside. Eventually we came up with a neat solution for the fan motor but the rest is a mystery.
Also fired up the motor (since it came from a written off car) and it sounded terrible! I later found an M5 bolt stuck to the windings, so took that out!

http://i1228.photobucket.com/albums/...motormount.jpg
http://i1228.photobucket.com/albums/...otormount2.jpg
http://i1228.photobucket.com/albums/...motormount.jpg
http://i1228.photobucket.com/albums/...otormount2.jpg

Also fired up Spinza today, but that ended with the blade spinning so ferociously that the wheels fell off and it snapped the timing belt turning the blade. Made a nice circle cut in the wood though...

And the car photos as promised.

Completed Frame:
http://i1228.photobucket.com/albums/...pleteFrame.jpg

Car on Frame:
http://i1228.photobucket.com/albums/...CaronBitza.jpg

And here is Spinza after it shook it's wheels off:
http://i1228.photobucket.com/albums/...aAfterTest.jpg

cool

Managed to do a little more to Bitza 2. Dan made up some motor mounts from Nylon (off cut) which we have bolted to some box section (old BBQ) and steel plate (oven shelf) to then sit at the back of the robot.

Trouble is we were very ambitious with our space and placing and now there is simply no room for the car fan motor. The teeth can still spin freely and the drum from Jamie should also fit but there's just no room for the motor given it's shape and size.

Unfortunately we are some what stuck for a solution.

http://i1228.photobucket.com/albums/...torMounts1.jpg

http://i1228.photobucket.com/albums/...torMounts2.jpg

http://i1228.photobucket.com/albums/...torMounts3.jpg

Mount the wheels externally and make wheel guards?

Extend the front a little? Should only need to add on a few inches to accommodate the car fan motor.
Also, haven't made it to a post office yet but will be heading in tomorrow so will get the drum sent then :)

I'd make one side of the box section flush with the mounts, rotate through 90 degrees and attach to the back bar of the robot so your motors are on top of one another.

You should gain a couple of inches of room in the front that way and still have a bit left over in the back for whatever.

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.

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.

http://i1228.photobucket.com/albums/...iary/Drum2.jpg
http://i1228.photobucket.com/albums/...iary/Drum1.jpg
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http://i1228.photobucket.com/albums/...torBearing.jpg
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http://i1228.photobucket.com/albums/...rumMockup2.jpg
http://i1228.photobucket.com/albums/...rumMockup3.jpg
http://i1228.photobucket.com/albums/...rumMockup4.jpg

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?

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

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.

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

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...

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?

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......

an astra!....good point then ;)

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

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?

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.

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.

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.

http://i1228.photobucket.com/albums/...y/Turning4.jpg
http://i1228.photobucket.com/albums/...y/Turning3.jpg
http://i1228.photobucket.com/albums/...y/Turning2.jpg
http://i1228.photobucket.com/albums/...ry/Turning.jpg
http://i1228.photobucket.com/albums/...uardMockup.jpg
http://i1228.photobucket.com/albums/...ardMockup2.jpg

Cool, how much weight do they add to the drum?

That's a really brilliant example of the Bitza mantra! Can't say I'd have ever considered using a spare weight for something like that. If I had access to a lathe, I'd have probably machined that from stock. Very nice, I like it 8)

Dan's going to weigh it when complete, I'm hoping it hasn't added 56lbs though!

With any luck the drum will end up around the 3kg figure. We're running a near enough 2:1 ratio, anyone have any idea what sort of rpm to expect from a car fan motor at 24v? Spec sheets are impossible to come by.

Cheers Jamie, looks like Dan's done a neat job!

I am guessing that they're quite fast, since well, they drive fans. Of course, even if they spin at just 3000rpm, at 24v you're going to get more like 6000rpm, so either way it'll spin pretty fast. :)

I am really interested to know this. I have a stonkin' great one from an ancient landrover that weighs several tons, could be an epic axe drive motor!

Thats cool :D

the drum is very impressive mate....i'm just thinking about how i'm going to defend against it

Dan has been working hard and has made up some braces for the shafts from the gearboxes, they look very impressive.

http://i1228.photobucket.com/albums/...uderBrace1.jpg

http://i1228.photobucket.com/albums/...uderBrace2.jpg

http://i1228.photobucket.com/albums/...ceMounted2.jpg

http://i1228.photobucket.com/albums/...ceMounted1.jpg

I should start wiring up BitzaMk2 soon but just want to check a couple of things.

Firstly, GiantCod is all out of DSM2 Rxs and I need a few, anyone know any good alternatives? Using a Spektrum DX5E?

Secondly, I think it was mostly dumb luck that Bitza Mk1 actually failed safed, but I don't want to leave it to chance this time.
Plus the fact I'm using a relay to control the weapon, how do people go about getting them to fail safe?
Using Electronize ESCs.

Cheers!

Quote:

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Originally Posted by PJ-27

Firstly, GiantCod is all out of DSM2 Rxs and I need a few, anyone know any good alternatives? Using a Spektrum DX5E?

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Take your pick: http://www.ebay.co.uk/sch/i.html?_from= ... Categories

:)

Cheers, but these aren't £6 each though... Plus I don't know what they are like fail safing.

You used a relay in Drumroll right? How did you get that to fail safe?