Help with disc

[ewan]

I am looking into building a drill motor powered disc within the build of my next robot. (exactly the same as the last Robot from me at the FWS 2004, only fully CNCd out of 10mm ali... The CNCd chassis will be lighter, and will solve many of the problems involved with the last Steel chassis).
I would be looking into using a 1:1 off the drill motor using a VERY small (about 6.5cm dia)steel disc that would be mounted on the scoop (middle of scoop at front). Could anyone (e.g Ed, Geoff etc) help me with a way to mount the disc onto such a fine (about 4/5mm steel axled) motor... I now have a CNC sponsor who can supply me with ali & steel stock (of MANY sizes) Its just I really need a way of modding this motor or something...

Any help gladly recieved,
Cheers, Ewan

[stu]

Help with disc

Ewan - id personaly advise you to maybe mount the disc onto a weapon axel and use some sort of belt to the disc. The drill gear boxes wont take too much of a pounding like that, you whizzing around at high speed with the disc spinning, then bash.

Mr Stu

[blazerbotics]

Help with disc

are u just using the motor or gearbox as well? either way i suggest that you have an axle supported both sides with the disc on, and like stu says, either a belt or chain to the motor.

[ewan]

Help with disc

(I am planning to run it 1:1 directly off the motor) The problem with chains etc is that A good mount onto the motor with a pulley/sproket would be difficult... Either way, I was planning on suppostion the other end of the axle with 10mm ali anyway, no matter what set-up I conclude on...

[Guest]

Help with disc

It may work, but you wont be able to use that tiny axle thats already on the motor.

First of all, I would suggest that you took a thicker axle and supported it on both sides with some bearings. Then you can just ask your sponsor to make you some adaptors that will join the two axles together!

It will still be direct drive, but the motor axle wont take any damaged from the impacts.

Secondly, I would also suggest that you mount the disc on the back. As it will take some time for the disc to reach full speed, it will be a lot more protected if mounted on the back.

Youll also be able to use the wedge while your waiting for the the disc to actually reach full speed.

Thirdly, I would suggest that instead of overvolting a single motor, you use two motors at their rated voltage.

[geoff]

Help with disc

Stop right there Ewan!...Put down that disc and motor and step away!!
If, after all I have said to you in the past, I catch you hanging a disc on a drill motor shaft, without using any extra suport bearings and a substantialy thicker shaft, I will personaly kick your back-side around the pits...If you think Im joking ...try it!!

Seriously for a moment, Christian has it about right! I couldnt put it much better my self. Think about a shaft dia. of no less than 12mm. We use 20mm on Scorpion Jr and even that is a little thinner than I would like, but testing has proved it to be safe.

Geoff.

[s8nsmum]

Help with disc

I believe FRA guidelins are 10% of the disc diameter but that doesnt really hold when things get too small, on any featherweight disc the smallest axle I would use is 10mm, and that would be a decent axle steel not aluminium.

Joe Townsend

[typhoon_driver]

Help with disc

ewan i wouldnt ever dream of mounting a disc directly onto an axle. You should have a seperate axle for the disc and connect the two using belts etc. If you dont have the weight allowance for this then you should ask yourself if u really can afford to put on a disc as it is better to have a really well thought out disc than one that will break as soon as it spins or is hit.

I may not know about pneumatics, hydrolics etc but if theres one thing i know about, it is discs.

[storm]

Help with disc

as well as disks, Gary is also an expert in spinning lampshade design robots :P

Seriously though Ewan, listen to these people. Ive only built one spinner - Vortex, but it didnt seem to do too badly, so Ill assume I can speak with a little authority here.

You need to think about an axle at least 15mm in diameter. You need to support it at both ends really in bearings. Were just trying to stop you from seriously injuring yourself mate !

Ed
http://www.teamstorm.comhttp://www.teamstorm.com

[ewan]

Help with disc

I am trying to make this one safe Geoff
I need to look at space within the robot (thus why Im not using a bigger motor) This is why I am using a drill motor. A drill motors high RPM is am advantage when it comes to discs, but Ill have to get the spinning mass perfectly balanced. I have decided on a 14mm steel axle, mounted on 10mm aliminium blocks on both sides. 14mm bearings are to be mounted within each block. The disc is to be an 8mm thick steel disc, about 6.5cm diameter, still allowong the robot to be invertable. Im having the centre of the disc milled out to 4mm, aiding the kinetic energy within the disc. I have decided to mount the drill motor (not overvolted) in the blocks Dominic is using in his UK robotics drill mod kit.
I am using a small belt to the weapon axle (from the drill motor) that will have a total reduction of 1:1.5

This setup will all be within the 8cm height of the robot. This is going to be a disc mounted under the wedge (youll know what I mean if your saw my bot at the FWS) designed to nibble at the undersides of an opponent as he goes up the scoop...

Any more suggestions gladly recieved

[kaideejee]

Help with disc

Youll have trouble mounting the motor in Doms mod kit without the gearbox attached - after all thats what stops the motor rotating with the torque.

-- Kev

[ewan]

Help with disc

Im going to fit a small polycarb flange to the front mount, thus stopping the motor from moving... (anyone know when the new technobots store is coming?)

[geoff]

Help with disc

In terms of disc mountings, that dosnt sound too bad. the only thing that comes to mind is disc 65mm dia. by 8mm thick in steel weighs only 208g and has a moment of inertia of 0.003876 ft/lb/s^2 before machining. So even if you are going to spin that at 10,000 RPM you are only going to deliver a little over 89j of kinetic energy into your opponent..I seems a hell of a lot of work for very little energy!
Something to think about!

Geoff

[ewan]

Help with disc

Maybe 20mm steel sounds better...

[geoff]

Help with disc

What, you mean a 20mm thick disc? or a 20mm dia. shaft?