Full Body Spinner design?

[Flag Captured]

Hi again everyone, it's that time of the week again, I don't know how to build things. Times like this I regret not taking engineering at Uni, but no matter!

First question is with the actual spinning element, I know the removable link and all that has to go in the axle with a full body (like Little Spinner's) but how would I get the outer shell to rotate properly? I was debating an axle like Hypno-Disc's (http://images.wikia.com/robotwars/im...Hypno_Disc.jpg) with the smaller diameter upper half, if you get my horribly poor descriptions, but the thing I was struggling with was how to prevent any friction on that ridge where the disc will rest - I'd assume some kind of bearing, but I'm not entirely certain on what the best idea would be... The post itself would be about 4cm in diameter, but with a 15mm-ish hole in the centre for the link, possibly. May increase both of those measurements if they prove to be a bit out too, I should add.

Second question along with that, would a wheel-based transmission work, like that on Gyrobot - http://homepage.ntlworld.com/steve-w...y/gallery3.jpg ? It seems like it'd be a relatively simple and effective way of turning the outer shell, only other method I would think of would be a timing belt on the motor and the disc, but again I don't know if that'd get a bit complex and unreliable.

The motor I was thinking of using was either this http://www.hobbyking.com/hobbyking/s...arehouse_.html or this http://www.hobbyking.com/hobbyking/s...tor_730KV.html - preferably the latter just because of the power behind it, but I don't have the right equipment for 11s brushless yet so I might be better off with the first motor I posted...

Thanks for the help in advance!

[adz600]

The shaft can be used with thrust bearings and roller bearings for the high load, ease of use you could use for example a mini Moto quad or go kart hub, is basically a ready made spinner hub.
friction drives are still complex, personally would go belt driven with endless green belt looks like a bungee just cut and glue together Allows slip to avoid stalling, will post links when not on my phone,

[Eventorizon]

Are you attempting a design similar to Little Spinner 4 or are you planning to make it invertible?

Your links are the main issue since usually the whole top would spin. You need a hollow central shaft that the machine spins on in order to get your required stationary links if you are mimicking LS4

If you are going invertible then You have all the issues around driving and supporting your outer spinning element. The wheel is one approach and id the easiest to achieve but it is not very efficient. In their design it works for yours it may not.

LS4's body spins at around a mere 1000 RPM (where most disc weapons are in excess of 4000rpm depending on the design) most of the time but is capable to 2000rpm, it rarely goes there as the chassis begins to rotate along with the body. Your first motor is a better choice as you will need less of a reduction to achieve that 1000rpm rim speed. That speed is linked to the robots diameter. If your diameter is different your speed will be too.

[Flag Captured]

Ahh, brilliant - I shall have a trek down to my local scrapyard to see if they've got anything in there along those lines, like a scrapped mini moto hub or something - it's not terribly likely but I can look! Thanks, adz!

I am planning to borrow the basic idea of LS4, except I'm attempting to make it have a slightly larger diameter and sharper, smaller teeth to cause more localised damage. Was debating an interchangeable tooth design, but I'm just sticking with simplicity for now till I've got my head around it! I was debating that invertible design too, but I think the problems with keeping the disc suspended around the edge are just too much hassle to warrant the effort at the minute, it's something I'm still actively designing around though to try and get that implemented.

Thanks for the insight though there with LS4's RPM, I thought it was much nearer the 5000 mark! Was aiming for about that on my machine, but if LS4 can only manage 2000 at most then I was obviously way out of the ballpark there! I'm not quite sure on the diameter yet, but I'll be making an outer shell with cutouts and then cover those up with some other kind of lighter shock absorbant metal or plastic so I can maximise the diameter of it - not sure exactly how big I'm going to have it but as large as possible is the aim for now!

[Eventorizon]

You may find this useful for more than 1 thing...

http://www.technobotsonline.com/robo...alculator.html

It is all about tip speed of the weapon. There is a limit to what is effective. For example 720's drum is only 95mm in diameter but does 13'000 rpm giving a tip speed of 144.7mph. Binky's disc is 270mm but only does around 6000 pm, giving a tip speed of 158.1mph. LS4 is around 600mm in diameter, at 2000rpm the tip is doing 140.6mph. Conker 3 has a theoretical weapon speed of 8000rpm, the fastest so far, but at 160mm dia it has a tip speed of 149.9mph.

So 4 very different robot designs are + or - 10 from 150mph. What makes LS4 so lethal is its inertia. There is so much spinning mass that almost nothing can stop it from spinning. That is also its down fall as in every hit that energy has to go somewhere.

[Flag Captured]

Ahh, I knew that had something to do with it! Explains why Hypno-Disc's disc was so destructive at the time with under 600RPM in its first appearance if I remember rightly... That calculator's a handy bit of software - got the basic plans outlined, looking at ust out of curiosity too, do you happen to know how heavy that disc on LS4 is? I'd hazard a guess that it's upwards of 8 kilos if it starts turning the chassis at 2000rpm. Thanks for the help too!

[Eventorizon]

It is around 6kg and it turns the base as you go over about 1300. There is no point in going over 50% of the robots weight for the spinning element as the base will spin rather than the top as it weighs less (simply put, there is friction but at that point you are getting silly).

Going over 4kg is really pushing it and that is still almost 1/3rd of the robot! Look at what NST was capable at just 3kg.

And the reason Hypnodisc was so effective in its first was was that no machine was designed to withstand it. Assuming the disc is 1m in diameter then at 600rpm the tip was doing just over 70mph. Berserk was incredibly unlucky and would have won the fight IMO if it were not for the spike.

[Flag Captured]

Ahh, I see! If I were to make a disc at say, over half the robot's weight but load the base up with magnets, would that be sufficient enough to stabilise it or is it best just sticking to around that sort of weight region anyway? NST's only got 3kg on that blade too? That's dead impressive!

That's true... kind of came out of nowhere, around series 5 people got wise and started piling on the armour...