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Ondray



Joined: 06 Jul 2015
Posts: 142
Location: Newcastle


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Feather making time.

I wanted a much simpler design this time, having a 3d printer now helps because I can print any tricky bits. So I went to my pile of volvo parts so see what I could use, and found this:



The radiator fan motor. Made in Canada no less! So the plan was to build a bot around using this motor, it doesn't have a gear reduction so that leads me to a KE spinner....The three wires on the motor and a quick play with it's control circuitry attached led me to believe it's was a brushless - but after I separated the wires and tried it on a 100A brushless controller I bought for it, I discovered it's brushed! Or at least it runs on DC. There's a red green and a black wire, the black is ground and it behaves the same regardless if I use the red or green, or both red and green wires...weird. But a bot bitz TZ85 runs it just fine. I just have a brushless ESC and no brushless motor now Sad

I thought for a while about the easiest way to build a solid spinner, and wound up coming back to square section. But with the whole bot inside the tubes, and steel instead of aluminum this time. I put some designs on paper using the same dimensions as the Al in Hellamax (50mm sqr, 3mm wall) and came up with a steel shopping list including some 25mm sqr for Hellamax and some 50x10mm flat bar for a spinner...

...Turns out steel places only like to sell 6-8m long pieces! So my shopping list came out to over $200. I asked my old boss if he knew of any good places to buy steel and he said I could just grab what I wanted from his scrap pile on his property Smile ...I didn't think he'd have anything thick enough for bot building - but I checked it out anyway and was happily wrong! Plenty of 75x50mm with 3mm wall, 40mm sqr and some other bits of angle. I also grabbed a tiny off cut of some 150x50mm stuff with a 5mm wall thinking it would be too big an heavy to grab the full bar - but it fits the 125mm wheels inside it perfect! This made armoring the wheels a jillion times easier (I was planning on building a box around them), which means I'll have to go back out to the scrap pile to get a bigger piece of the 150x75mm. Huzzah for scrap piles! Knowing the dimensions of what I was going to work with, I done up a design in Tinkercad:



So simple! most of the bot lives inside one piece of steel, a couple of bars to support the weapon motors and the 150mm pieces to protect the wheels. The design allows the spinning bar to be big, low to the ground and reach behind the bot as well. So somewhere between an offset horizontal bar and a full body. And if I line everything up carefully it will be invertible!

The design calls for some 3d printed pulleys and motor mounting brackets, I've been working on the brackets - up to my 3rd physical prototype:



It's a little big to fit in the section, I can sand them down - but it's all getting reprinted in ABS once I've built an enclosure so I've shaved the design 0.25mm in all directions. I think I'll add some side supports to fit into the 75mm section as well.

Post Wed Jul 06, 2016 11:45 pm 
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Cpnwolfe



Joined: 29 May 2012
Posts: 454
Location: Rockhampton/qld


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love me some spinners! what is the weapon bar made out of? if its mild it will hit hard but will most probably start to deform.
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Post Thu Jul 07, 2016 2:30 am 
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Nick
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Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


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Printed pulleys are not likely to take the strain or heat - belts & pulleys generate quite a bit of heat and even ABS will probably get tacky and fail.
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Post Thu Jul 07, 2016 2:51 pm 
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Ondray



Joined: 06 Jul 2015
Posts: 142
Location: Newcastle


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Wolfe, the current plan is mild steel I'm going to ask the steel place in person if I can get hardened steel bars but I think that'll be a lot harder to source.
I have to buy a 6m bar, so I can make a couple of spares Smile

I was even thinking about seeing if I could use the chemical vapor deposition system gathering dust at uni to do a titanium nitride coating, but the thickness I'd be making would be purely cosmetic. Would be good for a cutting weapon though.

Nick, I did have my doubts about the printed pulleys - I'm still going to try them otherwise I can get access to a laser cutter at work now so maybe 6mm polycarb sandwiched to form the shape...I might even have a big enough holesaw...if that doesn't work I'll try printing a mold for the pulley...

Is polyurethane belt from rs-online the best option for the drive belt?

Post Thu Jul 07, 2016 11:45 pm 
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Nick
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Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


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Do you have a link to the belt in question? I have used polyurethane belt in Mr Mangle for years and it holds up pretty well. The round belts will slip a lot and the smaller sizes will probably snap. The poly V belts will grip the pulleys much better. I used the Z size at first but it wasn't up to the job and stretched too much. I am now using A sized belt with a reinforcing cord embedded in it and that works pretty well.

You have plenty of room in the design so I would look at making larger pulleys and using a regular rubber M sized pulley - they worked very well in Decimator and you can get them quite cheaply from Smallparts http://www.smallparts.com.au/store/partslist/beltsvee100x55mmm3l/beltsvee100x55mmm3l/a/1/ .
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Post Fri Jul 08, 2016 1:38 am 
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Ondray



Joined: 06 Jul 2015
Posts: 142
Location: Newcastle


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This is the belt I was looking at, either the 5mm or 6mm, and I was planning on letting it slip a bit so on impacts less shock is transferred back to my own bot - sacrifice spin-up time and max speed for survivability, especially when the bar and bot will only be mild steel:

http://au.rs-online.com/web/p/round-polyurethane-belts/3098123/

I was looking at polyurethane because I can make any size I want by just heat welding the ends and the v-belts were all too long. My current design calls for a 23cm belt, the v's start at 32cm.

Looking at the pulleys and thinking about putting an idle tensioner on made me realize I can just use up the extra length with the tensioner. It will probably make the belt sit out to the side a lot and I think I'll need a second idler to make the belts wrap around more. The thought of not making my own pulleys, stronger belts and not having to weld the belt is probably going to win me over...if only smallparts.com had an easier to navigate website...

The steel place down the road from my house sold me a 1m off-cut of 50x8mm flat bar for $5 that they had lying around. but I have to order in the 50x10mm. The 8mm will get me started anyway. So I now have enough parts to start building!

Also I've enclosed my 3d printer, but the little bunnings fan died and the hotplate won't even get to 110'C in my 15'C house Sad (It's *almost* there sitting at 107'C) so there'll be another trip before I can print with ABS.

Post Sun Jul 10, 2016 1:17 pm 
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Nick
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Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


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Its hard to predict how that belt will perform - RPM, bar weight and even air resistance all play a factor. Based on using unreinforced Z urethane belt (about 5 x 10mm) on Mr Mangle, the round belt is probably going to stretch too much and overheat. Once it gets hot, it will start to stretch and that leads to a cascade of failure - trust me, I have seen it up close 'n personal!

If you make your own pulleys, perhaps you can make a dual pulley and use two belts?

If the printer's heated bed isn't getting hot enough, you can try insulating the underside of the heater mat. a couple of layers of corrugated cardboard should do the trick if there is nothing higher tech available. What died on the Bunnings heater, the element or the fan?

I have to agree about the Smallparts web site, its a shocker!
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Post Sun Jul 10, 2016 2:14 pm 
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Ondray



Joined: 06 Jul 2015
Posts: 142
Location: Newcastle


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I considered the dual belt idea with custom pulleys especially because the min length from rs-online is 5m, however with 10mm thick pulleys there's only a couple of mm clearance left when it's upside down. The redundancy would have been nice.

I ended up ordering a couple of 75mm pulleys and the shortest belt they had in stock (370mm). It will make things a lot easier.

I don't know what caused the fan to die, I didn't pull it apart - just chucked it in the enclosure. It worked yesterday - then just wouldn't turn on today. I am aware of the little tip switch on the bottom - and it's probably the culprit. If I pulled it apart I could bypass it, but Buntings is so close it's quicker to return it.

I think I've got some old car-exhaust insulation (possibly from the volvo parts bin where I get all my other stuff...) that would be perfect for insulating the underside of the heating bed.

Post Sun Jul 10, 2016 11:20 pm 
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Ondray



Joined: 06 Jul 2015
Posts: 142
Location: Newcastle


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Steel is dense! I done some quick calculations and my original bot design came in over 17kg! So I done up a spreadsheet to calculate how the mass would drop as I shrunk the design. The 150x50x5 RHS had to be dropped for two pieces of the 75x50x3 welded together, which makes the wheel pods weaker Sad but save another drive out to the scrap pile...I also had no idea how I was going to cut something that big.

All the big pieces for the feather are cut out, just need to do a little jigsaw work then it's ready for welding. I also got the pulleys and belt from small parts - the belt that I thought would be too long turned out to be too short because I made a rookie mistake in my calcs, I didn't count the gap between the pulleys twice *facepalms*...but it's only 3mm short for my planned design, so the weapon will just move back 1.5mm from center with no idler.

My 3d printer is enclosed (with a blanket wrapped around it lol) and is printing abs - so I've got some nice drill brackets . Turns out the problem with the heater was the over-temperature fuse attached to the heating element itself...discovered when the second one I got from bunnings also died (hope they don't read this) so I pulled it apart and bypassed that safety feature and removed the tilt switch while I was at it Smile I only turn the heater on for maybe the first 20-30 mins the box seems to get to around 30-40'C and the bed puts out enough heat to maintain that temp which I'm happy with for now. Only trouble I had was I need to re-level the bed once everything gets to temp - I think the acrylic holding the bed starts to sag as it heats up (it will probably get replaced with something sturdier down the track)

And Hellamax is 4WD now and has stronger weapon mounting bars. No pics because I'm posting from my tablet because I forgot my forum password lol.

Post Mon Jul 18, 2016 12:02 am 
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Nick
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Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


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Thanks for the tip about the thermal fuse - I assumed it reset when the fan cooled down.
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Post Mon Jul 18, 2016 9:30 am 
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evil_steve



Joined: 06 Sep 2015
Posts: 304
Location: Adelaide, SA


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Out of curiosity, did you use a chain breaker on your 04c roller chain? I'm debating buying one from a cycling store and hoping it works or going the hammer and nail route (and/or buying one online and hoping it gets here in a reasonable time-frame).

Post Fri Jul 22, 2016 7:53 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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The problem with using a punch is that the pin will almost always pop out of the chain side plate and even if you don't lose it on the floor, its a right bugger to get back in!
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Post Fri Jul 22, 2016 9:18 pm 
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Ondray



Joined: 06 Jul 2015
Posts: 142
Location: Newcastle


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Oh the fun I had with the 04C chain - I ended up using a combination of a bicycle chain breaker and a hammer and nail and a lot of swearing. The bicycle chain breaker I have sorta fits if I fold the 04C into it - but it's a compact breaker designed to fit into my bike tool pouch, a cheaper and non-compact one may be easier to use. I also clamped the pins in the vice to get it re-assembled.


My spinner now looks like this:


Pretty much just needs the welding and wiring. I sacrificed invertibility for having a decent gap between the spinning bar and the weapon motor...I really didn't want to follow Chromefly's example and have my bot eviscerate itself after hitting an opponent. As for the name, I was calling it Pot Head because in my initial designs I was going to use a cooking pot to protect the pulleys. But steel is heavy! So there won't be enough spare weight for a cooking pot, hopefully I can still get a plastic flower pot on there for namesake Smile

I also learned a lesson in triple checking the hard way that cost a battery, the wiring loom in Hellamax and a BB TZ85...


I simply wired the leads going into the speed controller the wrong way...I even tested it on the lab supply first but I think I hooked it up according to the leads going into the plug instead of the plug itself Sad that was going to be one bot finished too.

Ahh well, I ordered some spares previously so I just have to redo some wiring a bit more carefully.

On the plus side I'll be inheriting my Grandads old welder when I visit the fam this weekend.

Post Wed Jul 27, 2016 8:24 pm 
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evil_steve



Joined: 06 Sep 2015
Posts: 304
Location: Adelaide, SA


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Love how the spinner's shaping up! Maybe you could use a steel colander - that's apparently what the drone for Poison Arrow was using as it's armour.

Thanksfor the chain advice. The bike shop near me had apparently just sold it's last chain breaker when I popped in in the weekend, hoping to get there tomorrow arvo as they should have more in. I'll try and get a cheaper/bigger one!

Bummer about the wiring mishap, I did the same thing when rushing to get Zenghiaro finished for Vivid. Looks like you did more of a number on your battery though - mine looked ok afterwards but apparently destroyed one cell (the charger thinks it's a 3S rather than 4S).

Post Wed Jul 27, 2016 9:23 pm 
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Glen
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Joined: 16 Jun 2004
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Looking good Smile Those chainbreakers are always completely aweful! even the bike shop ones. The best way to get them apart is to grind the end of the pins off and then use a center punch to whack the pins through enough that the side plate comes off.

Master links are fine. Make sure you put it on the right way though, add lock wire if it helps you sleep better at night Smile

http://wenga.net/ellingly/misc/DSC_7268.jpg
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Post Wed Jul 27, 2016 9:34 pm 
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