Bit of advice on my drumbot please

right, hoping to start making a new one this friday, ordered some 20mm nylon 6 for the 2 bulk heads that will support the drum and the drill motors, theres gonna be a 3mm ali or mabye even 2mm ti baseplate and the rest is hardox with the exception of the lid

but i need some advice as to whether i go 2 or 4 wheel drive off a pair of drill motors some pics are below........

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not fully settled on a design yet and the insides would be set out differentally but i'd use the 75mm wheels instead thou to save on the weight as wheels that big aren't really needed but im really stuck as to what set up im having, the benifits of 4 wheel drive were purley due to the drum being 3.7 kg i was worried about it being front heavy and not driving properly so with 2 wheels either side of the drum it would get rid of this problem and drive better, but then of course then theres all the extra weight from extra wheels and mountings etc and the robot slowly starts to get less compact as it'd have to be made wider to house the wheels and belts so i'd have to skimp on armour. or with the 2 wheels i'd use that size of wheel but i've tried making the robot to have as much weight as possible over the wheels and i've also put them as close to the drum as possible. Althought 4 wheel drive would look better visually, part of me just wants to keep everything simple and 2 wheel drive and see what happens,

then of course theres the problem of it not being invertible, but i think i could live with this because once its upside down anyway the drum isnt effective spining downwards, i could use those massive 150mm wheels again but i don't fancy it cause that take away too much power from the motors and pushing power is very low, but any ideas anyone?

I'd personally try to setup 4 wheel drive. No use having a stonking weapon if you can move it near the enemy effectively! And surely 2 belts and 4 pulleys, with bearings and mounts, isn't going to hugely affect your weight? That weight could be made back quite comfortably by cutting holes in bulkheads and smaller batteries?

Hmm... the drum setup you are using isnt going to work! That kind of setup doesnt work, as the COG on the drum moves up and down (or something like that :lol: )as it spins, and there are going to be some very bad vibrations.

heyy yeah i forgot to say i already new this, the 2 bars were a rush job to get my old drumbot working and they were a very bad idea. im grinding those off later on in the build and getting 2 ring teeth made with 2 teeth on each. not fully decided on that thou yet

get tom to make you 4... two in the middle on one side, and one on each end with teeth on the oposite side.

go 4wd... with self-righter.

and get brushless stuff... thought you wanted to make a proper robot this time?

YE CALUM! BUILD A PROPER ONE! :lol:

just forgetting the fact that i can build robots properly yet but still :proud:

or you could buy a robot you dont know how to use and just start loads of new threads talking about all the projects you want to start that will never materialise? dribble dribble.

:lol:
dont forget your ic car at kidderminster dave.

i was only joking dave, calum knows i dont mean it :)

i realise that i was posting about trash, at least i do now

ah forgot about that terry, good job you reminded me... i mashed up the main central gear... best order a new one.

Hmmm, 2WD or 4WD? I have to admit, the 4WD looks waaay cooler and it looks a little Growler-esque but with a hulking great drum in place of the jaws. In addition to that, if your drum breaks down in battle, 4WD could benefit you more when you have to resort to ramming people around.

Other than that, I don't think there are any advantages of four wheels over two. With two wheels, your turning (particularly on the spot) will be much quicker which could serve you well if you need to spin round quickly to attack someone. As mentioned, it'll also be lighter and more compact, leaving more weight for armour or weapons. Your pushing ability will be slightly less but probably not that significant in the grand scheme of things.

If you can adjust the design slightly to accommodate invertibility, I'd strongly recommend it. A self-righter will take up weight and be a lot of work (thinking back to how many problems Dave had trying to get 360's one working) and for me, just stopping fighting when turned upside-down isn't appealing. Just my opinion though :)
Then again, it could end up righting itself with the drum anyway; that's what Gary discovered with Boner at the 2010 champs with the Speed 900s in. If he spun it up while upside-down the drum teeth would hit off the floor and gradually bounce the robot a bit higher with each hit until it flipped itself all the way back over.

Regarding brushed/brushless, I find the Speed 900s are only really effective if the drum is over a certain weight. They worked great in old Drumroll/Boner because the drum weighed 4.2kg, but my current one weighs 2.1kg and there's just not enough energy in it to do any decent damage. I know the obvious fact is that there is a lot less weight in the periphery so there's not as much energy built up to transfer, but with more speed comes more energy, so brushless motors are probably the better option for the lighter weapons. That's what I'm going for anyway; seemed to work well at the 2010 champs until I busted a tooth :uhoh:

quick reply cause im on my phone, but thanks jamie bin talkin to dave and recon im going for those big wheels again :) i got a decent speed too on only 8.4 volts at the uks. having them as far forward as possible shud hopefully stop it having the same problem as last time D:

Quote:

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Originally Posted by calumco

jamie bin talkin

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Am I the new leader of Al-Qaeda or something? :shock: :lol:

Apparently so :lol:

2 wheels, I'd go for the small ones and have a dummy set on the top side pressed against the powered two to run via friction upside down. Get a decent brushless setup and that drum will fly.

LOL jamie haha

gary i could kiss you..... but i wont, but still thats a brilliant idea! means i can make the bulkheads higher meaning the drum can run freely upside down aswell as it wouldn't have been able to before and the robot can be alot shorter as all the internals can fit in vertically above the motors :) got a pair of 100mm wheels with bearings inside already..... propper job!

nylon came today aswell, so hopefully start making tomorrow/friday :)

Ah yeah, that's something I forgot to add yesterday. Smaller wheels seem to be more reliable with drum spinners (from my experience anyway). Drumroll had 75mm wheels, Drumroll II has 125mm wheels; the greatly-increased speed of Drumroll II is handy for darting about the arena, but there is much more force being placed not only on the drill shaft, but also the nuts melted into the wheels, especially when the shocks from impacts are going through your robot. I'm currently on my third set of wheels with Drumroll II and am planning on making a new set soon. The nuts began to pull out of the first set (home-made), with the second set one became partially loose then got jammed on (the pair I used at the champs) and the current set, while holding up fine in that respect, don't quite have a level of grip or robustness I'm happy with. By comparison, the old Drumroll ran the same set of wheels for four years without any problems.

surprisingly after just 5 and a half hours today i've got something which resembles a robot......

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Going for lipos for the drive and drum as i wana save as much weight as possible for hardox wheel guards and lower back armour. i may even cut the top down so it slopes down towards the back to save on nylon weight as its heavy and to get it even more compact but ill see how i go on space inside. suprised aswell because nothings gone wrong so far or been mounted wrong lol i must be learning after 3 years finally

next job one day next week is to get the speedos mounted, make my own ali bracket for the drum motor and wire most of it up and hopefully give the drum a slow spin up and drive about

Make sure you chop those teeth of before you spin it up lol

Did some yesterday, cut the bulheads down on the top so that they are sloping down towards the back and its looking pretty cool now :) sorted out the motor mounting, and cut the teeth off the drum but the drums now totally screwed :( still badly off balance without any teeth on now im guessing from the welding and weld replacing stainless on the drum and so forth so its once again off balance. thinking about sending it to someone to get teeth made but i don't think it'd be easy balancing it so i may get tom or kenny or someone to make me a beater style weapon instead of the same dia. but pics to follow soon.....

Pics

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Last picture showing the weight, need to make a new motor bracket atm so the motor won't be looking wonkey much longer, was going to go for lipos but for the space i had avaliable nimhs were easier to work with. may go for a slightly lighter weapon as the drums 3.7 kg atm aswell wana hopefully aim for a 3kg weapon

Sell the nimh and get lipo. Find space to fit them in. You would notice a huge difference if you were to do a direct comparison in spin up time.

It's a drum, it's ridiculously compact and it's blue - what's not to like? 8)

Your not Scottish as well are you Calum?!

Being Scottish is awesome, so it's no wonder everyone wants a piece of the action :rofl:

I would gary but the cost of buying more batteries and chargers etc isnt something i can afford atm so if anything i'd upgrade that later on. decided i wanted to put what money i have into a new weapon for the time being.

and yeah lol i couldnt decide what colour to go for and i thought i'll go blue to match the other drumbots lol

[quote=calumco]LOL jamie haha

gary i could kiss you..... quote]

Proof that FRA members know each other a little too well :rofl:

Can i just ask why people use belts for the drive on the drum?

I get the gear reduction and shock absorbtion issue. I'm asking because i have some sprockets and chain which would probably suit and just wanted to know the pros and cons of each

Andy

Both are perfectly usable forms of transmission for drums. I think I chose belts over chains initially because I wanted a bit of slip (although not sure how much a timing belt actually slips during a hit) and if you have flanges on the pulleys, the belt is less likely to come off, whereas a chain could be prone to jumping off or snapping during a large impact. Having said that, I've never worked with chains and sprockets on spinning weapons, but I'm sure I've seen DragonStrike's chain on the arena floor more often than on the motor/disc (and it usually seems to make its way there after a large impact)

And for the obvious; pulleys are lighter than sprockets and easier to machine, which is handy if your facilities are limited. You can get larger reductions in gearing for a certain diameter than you can with sprockets although they usually are the more expensive option, albeit only by a few quid.

They're the main reasons that come to mind and why I chose belts, but if you've got - and want to use - chains, it shouldn't be too much of an issue.

NST snapped a chain at the last UK Champs and I think that was the only bot to use chain driven weaponary.

Chains are a nice option because they're readily available and you can make them to the size you want, plus everything Jamie said....

I could give a list similar to jamie but I can summarise it all with one sentance,

I use them, because they work

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Originally Posted by typhoon_driver

I use them, because they work

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That's just crazy talk that is!!