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Ah of course. Now you've said that, I remember seeing some data logs (I think for 360's brushless) showing the low continuous current consumption after the initial spin-up period.
The drum spins much more freely now that I've gone back to needle roller bearings, but I'll make a point of lubing them regularly nonetheless.
Quick Update
The belt for the drum arrived today from Technobots, and it's a perfect fit. No tensioners required!
Just gave it a quick spin-up and I'm happy and impressed with the brushless configuration. The drum could be a problem though.
Despite appearing to be balanced when spun by hand, it starts to vibrate and bounce considerably when the throttle goes past about 20%. I reckon this is the same issue of dynamic imbalance that Calum experienced on his drum that just had two teeth offset at 180°.
I had hoped it wouldn't be too much of an issue having three teeth at 120° intervals but seems that's not the case.
Worst case scenario, I can run it at the champs and just ramp up the throttle when I'm about to hit an opponent, but I think it's worth seeing if I can get another tooth made and add it to the drum in the same arrangement as the old drum, so: V---^---^---V
Back out to weld the armour back together, but will have some pictures and possibly a video later.
Had a feeling you'd have that problem... Get a video :)
You will need to get a new drum made I think
Yeah, either a new drum or possibly a beater.
Will save it for after the champs though. Don't have the inclination to rush something beforehand, or the cash for that matter.
The other way of trying to get around it would be to weld on the inside a weight opposite the tooth. Then it will be statically and dynamically balanced. The weight would only have to weigh roughly what the extra material on the ring weighs.
Even if you can't get one welded in the center tooth of the drum, two on the outside teeth would stop the bot from wobbling sideways as the imbalance would be in the center of the drum only. The bot would bob up and down instead of side to side.
O and I would initially do a small tack weld to hold the weights in place. Spin it up again and check it all out. Then if it doesn't work, a large chisel and hammer and some brute force should remove the weight.
Actually it could be welded on the outside, just to the side of the ring. Although it wouldn't be as neat. It obvious I'm thinking on the spot here?!?
Haha, just a bit. I've actually been thinking along the same lines as you though. I can't weld anything to the inside since the endcaps are welded in place, but I'm thinking that welding on some chunks of metal on the outside is worth a shout. Looks aren't important so no worries there :)
Glad I've got the robots ready quite early this year, leaves plenty of time to faff around with things like this!
Do you need your Ali drum back? Haha.
Hope you get it sorted, Drumroll deserves a decent shot, especially with all the upgrades.
Yeah I'll take that ali drum now that you've fitted those lovely teeth to it!
Not got a whole lot left to do to Drumroll now. As mentioned earlier the belt for the drum arrived, along with some fuses for the lipo, and it fitted in nice and snug:
http://i31.photobucket.com/albums/c3...2_build113.jpg
Most of the day was spent re-doing the armour, which hadn't been properly fixed since NST had its way with it. Not sure what it weighs but it now wraps around the robot as a single piece, rather than two separate side pieces. Need to go over a few of the welds to beef them up, but ran out of welding rods:
http://i31.photobucket.com/albums/c3...2_build115.jpg
I was going to re-fit the wedge as well but, as much as I love how it completes the look of the robot, I'm thinking about just ditching it. I reckon it won't be that effective and will more likely get bent and impede the drive.
So currently it looks like this:
http://i31.photobucket.com/albums/c3...2_build116.jpg
It's also had new tyre screwed onto the wheels as the old stuff was a bit flat and not particularly grippy. I can also switch them round with the Banebots hybrids you can see in the background, should I feel they offer better grip or just want snazzier colours.
Still need to fit the fuse, fit some new power distribution bolts, try and balance the drum and then paint it. Maybe a couple of days work overall.
Still got a couple of things to finish up on Carcinus too, but it's pretty much ready to go. Re-did the paint on the claws, although I've taken the easy way out and just made the claws static. With my dad's driving, it's one less thing for him to worry about :lol:
http://i31.photobucket.com/albums/c3...c2_build23.jpg
Plan for tomorrow is to start on the MDF bot, although if there's time, I'll take Drumroll down to the industrial estate for a test.
Both looking excellent, does Carcinus drive funny, diagonal wheels ? :), get those pincers working for your Dad :)
Thanks. Yeah the wheels in Carcinus are set 120° apart and the idea is that the robot is able to strafe i.e. it can go diagonally and sideways. There's supposed to be a third wheel at the back to complete the setup but I've been having trouble trying to find a wheel that's slippy enough to be pulled along when the robot is moving forward/back, but grippy enough to turn the back end when needed.
The robot is also front-heavy due to the claws so there's not much weight pushing down on the back wheel, which doesn't help matters. But I've got a homemade wheel idea in mind that I'll try and see how it goes :)
Regarding the claws, I think I've actually made the robot a little compact to fit an effective enough actuation mechanism into. Either that or I need to consider more compact custom options. But the drive uses three channels so I think my dad would struggle to cope with having four channels to operate!
How about a wheel modelled on the back wheels of Razer, rolly bits
I did have a look at omni-wheels, but the only commercial one with a 125mm diameter had rollers that looked like quite a hard plastic, and I didn't want to get it shipped from Australia if it wasn't going to work. I'd probably need a custom-made omni-wheel but there's too much faffing about involved in making one when there's no guarantee that it would definitely do the job.
Will play about with a few different tread materials and see what produces some decent results.
jamie looking really good :)
out of interest how heavy is your outer hardox armour?
Cheers Calum :)
Not sure on the weight, but I'll find out tomorrow and let you know.
So what you taking to the champs? Drum or crusher I hope?
cheers, robot with a beater hopefully :) was going to be having the same kinda hardox armour around the back and sides too so just wondered what yours weighed, i need to get a bit of a move on with getting it made really lol
Weighed the armour tonight Calum. Currently comes in at 2.62kg, and I've still to add some pointy triangle bits on the back and sides to stop the robot resting there.
Update
Been considering my drum options yesterday and today, and in the end I decided to mix and match the two drums that I have. The bar-tooth drum that I ran at the 2010 champs was pretty well balanced when it was running off the brushless, until I smashed a tooth off of it anyway :roll:
So to save having to wrangle with the current drum to try and get it balanced, I figured it'd be easier and more reliable to just settle for the bar teeth.
First things first, I needed the new endcaps (the ones Kenny made) off the current drum, so out came the angle grinder. This was followed by a lot of hammering, bashing and a few choice swear words, but eventually managed to get them free:
http://i31.photobucket.com/albums/c3...2_build118.jpg
Then I needed the old bar-tooth drum. I ditched the aluminium outer tube, sat the titanium endcaps to the side and un-bolted and cleaned up the teeth, along with the salvaged endcaps:
http://i31.photobucket.com/albums/c3...2_build119.jpg
Put it all together and voila:
http://i31.photobucket.com/albums/c3...2_build120.jpg
Still need to weld it but already I can tell it'll a huge step forward to reducing the erratic vibrations of the robot which will make controlling it much easier. This drum weighs roughly the same as the one it's replaced (~2.3kg) so it's not a huge difference, although it will probably be less potent.
So the aim is to get that finished off at the weekend, along with the rest of the armour (5kg worth of welding rods arrived today :) ). Fingers crossed it'll just need a paint come the end of the weekend.
can i get those titanium end caps back? Will need them if i ever rebuild hornet 2
No probs, will bring 'em to the champs.
it's looking less and less likely that i'll be at the champs sadly :( but i'll get them off you the next time i see you
o and you could go for a single tooth config with the bar teeth. Have a quarter of the bar on either side with a half in the center on the opposite side. Dynamically and statically balanced and deadly :)
Oooh, that's a possibility *ponders*
I'll have to think it through, as the hardox bars make up a fair bit of the weight of the drum and with a (--__--) configuration, I'd effectively be taking one of the bars off. Will check the weight of them next time I'm in the workshop and have a think.
And I've got tonnes of jiffy bags kicking about and remember your address, so I'll just stick those endcaps in a bag and mail them to you.
Good point although it's always better to have an effective energy delivery system with a lower kinetic energy than a higher kinetic energy but poorer delivery system.
Update
In the end I just decided to stick with the two teeth rather than splitting them up. Welded the bars in place, but despite trying to get them welded on 180° apart, the drum still seemed to be heavy on one side and attempts to balance it out with angle grinding didn't work too well. So tried the swiss-cheese approach and it now seems to run quite smoothly (still a little bit of vibration but not enough to affect the control)
And yes, I know my welding's pish:
http://i31.photobucket.com/albums/c3...2_build124.jpg
Also welded on some pointy bits (6mm steel) to stop the robot from resting on its side or its back if it gets flipped or does a gyro-dance. The welding was a little better here:
http://i31.photobucket.com/albums/c3...2_build123.jpg
Going to move on to testing now, see if that flags up any weaknesses, and then pull everything apart to check every connector, screw, joint etc. It'll then get re-assembled in preparation for the champs and given a coat of paint. After that, it'll be completely done 8)
And if you work in a confined space, don't spend hours angle grinding bits of metal. Took me three hours tonight to remove the layer of metal dust that had attached itself to everything!
http://i31.photobucket.com/albums/c3...m/DSCN6478.jpg
Shame your 3 tooth drum didn't work out, it looked very neat and deadly.
make the drum longer and go back to a 4 tooth backbite drum :)
haha jamie you'll soon learn to aim your grinding sparks into a designated corner of your shed rather than just any direction :P
looking through this wants me to get my spinner on the go (Y)
Haha, I do generally aim the sparks into the one bare corner of the workshop, but because it's only an 8' x 6' shed, the metal dust created just settles everywhere. Most of the grinding's done now and the weather's getting better so no need to mess up my precious shed again :proud:
After the champs I plan on cutting/grinding the teeth off that drum, getting another tooth made and going back to a 4-tooth drum. A wider drum would need a new chassis though, and having just spent ages getting this one done, that's something I'm not prepared to do yet. The current drum length will be fine anyway, I can just stick the two middle teeth together to make one thick tooth in the middle and two on the ends.
Looking Great Jamie! Cant wit to see it going, always performs well.
I really liked the ring teeth, shame about the vibration, the finished bot is looking really good
Thanks guys, much appreciated. Just hope it performs better this year!
I've just weighed the robot in its completed state and it's coming in at 11.3kg :roll:
So 2.3kg to spare and nothing more to do to it. Could possibly increase the thickness of the armour after the champs, but I don't think that would provide much of a benefit. Other option could be to try and pack more weight into the drum.
The plan is to go back to a four-tooth drum after the champs, so my best bet would be to increase the thickness and diameter of the teeth to try and bring the robot closer to the weight limit (while maximising damage potential of course 8) )
Anyway, I'll be taking it to work tomorrow in the hope that I'll have a few spare minutes to test it out. Test subjects will probably be some old drawers and cupboards (maybe some aluminium rail) so nothing hugely challenging, but that's all there really is available. Video should follow within the next day or two...
Well even if you dump a lump of lead on the back, get to the right weight (spinners less likely to hurl you away) plus its squashy so will absorb impacts. You could also melt it easily so you can pour the right shape.
Brick
Had a quick wee test at work today, but me being me, I forgot to take my camera. Wasn't a whole lot to film though; it was a wooden cabinet it was up against but it was quite mouldy/damp so instead of bits flying off everywhere, there was mostly just lots of sawdust. But my colleagues seemed suitably impressed.
The drum had about four spin-ups during the test and was running for about three minutes, but by then the drum wasn't reaching its full rpm and you could hear it running down. The battery was setting off the low-voltage alarm by the end of it, so suspicions about the battery capacity have proven to be an area that needs addressing.
Two options: the first one is that I need to beat all my opponents within a minute or two :proud:
The second, more feasible, option is to connect two packs in parallel. Going to a single bigger capacity pack is fine in theory, but there isn't enough space as the packs get bigger as the capacity increases. But I'd bought a second 18.5V 2200mAh pack to act as a spare, and there's enough space to fit it on top of the existing pack (provided that doesn't cause any safety issues and that parallel connection of lipo packs is fine) so sorting that out will be a job for the weekend.
But that aside, the test showed no major problems. Drive was fine and drum was fine; probably the first test I've ever done that has ended as a result of low batteries rather than something coming loose and/or breaking :)
Update
So took a trip down to the industrial estate today to give Drumroll a run. The results were good; each battery pack went for about four minutes at full power before starting to show signs of running down, so I feel more confident that one pack will be enough to last a battle, and with two packs, I can have one ready and waiting to go into the robot as soon as its last fight is finished. The drum is also running very smoothly with minimal vibrations, so that's another bonus.
The test itself was just against an old computer scanner. Nothing challenging I know, but it's all there was lying about so it had to do. It smashed up well but after a few hits there wasn't much left of it to attack, so I resorted to just going nuts with gyro-dancing 8)
Enjoy:
http://www.youtube.com/watch?v=JXxJ4um0gYM
nice moves jamie :) you could side flip all the way down the arena :)
That's a lovely machine Sir! I like the destructive power and you've an excellent victory dance. I trust you will sort out the getting stuck part :)
It's looking brilliant! I know it's deadly, and I can only say this because I'm not fighting it in qualifiers, but, it's small and it does little dances and it kind of... I find it... c-cute? :uhoh:
I keed I keed, looking very forward to meeting it and watching it destroy things!