Sudden impact - instantaneous braking

[rackers1992]

Progressing ever onward with the build of THRASH METAL; however I am currently stuck again with an issue.

How have people overcome the instantaneous braking issues that occur when using a momentum/kinetic weapon?
(By this I refer to the sudden stop that occurs upon some impact scenarios when in battle)

My current design is using an Ampflow DC brushed motor and a chain drive on a weapon that is roughly 21kg. I have done some rough workings for speed and acceleration but the braking and stopping still pose an issue. Currently my only solution that would work (and at that somewhat partially) is a cush mount system - similar to the rear drive and sprocket on a motorbike.

I have looked in to Bendix drive systems and centrifugal clutches but I cannot find a suitable method of protecting the motor armature and drive from damage when subject to immediate braking. Both methods do not give suitable mechanical solutions. Is there not a friction based clutch that has similar properties to a torque driver or the slip present in a drill motor?

Other factors include:

- I would prefer to not have to use a toothless belt as this would impede motor acceleration.

- I would also prefer not to use an AC inverter to power an induction AC motor as this is a weighty solution.

PLEASE HELP; I SEEM TO BE STUCK IN THIS VICIOUS CIRCLE OF A MECHANICAL QUANDARY - THIS IS THE PRIMARY ISSUE LIMITING THE FRAME BUILD!

And as always any help is much obliged

[joey_picus]

Most people use timing belts with no teeth on one pulley (usually the weapon), from what I've seen - tensioned right, you're not going to experience much loss of power when spinning up, and that provides the clutching action you're looking for.

[Rapidrory]

To my knowledge, most high power electric weapon which don't use a belt requires a slip clutch to protect the motor from impact. There seems to be a particular type, but I'm not sure of the name...

[typhoon_driver]

Joey the system you describe can work and can work well (especially in feathers) BUT you need a hell of a lot of tension to transfer the power required for a heavyweight spinner. Can't say why I know, but I do

[rackers1992]

Thank-you for the pointers - I will keep looking into the clutch system.

[typhoon_driver]

Your other option would be to use V-belt pulleys. Plenty of grip to transfer power but will happily slip if required.

[rackers1992]

Thanks - cost wise I am leaning toward pulleys!

[supernova]

Try this:

http://www.cross-morse.co.uk/pdf/TL%...ouplingsEN.pdf

[katch]

I work on Motorcycles on a daily basis, a Variator a clutch from a scooter 50cc would probably be more effective since the belt and gearing will always change and be in the right gear for the most efficient use of power. You can experiment with different weight rollers for a faster bite or higher rpm. The V belt is designed to slip and won't wear or break with sudden impacts and will instantly revert back to the best gearing to get going again. overall weight is about 3kg.

[typhoon_driver]

Nice idea with the variator but you need to remember that electric motors have max their torque at 0rpm or stall. Therefore variable gearing isn't required as you have the torque when you need it unlike a petrol engine.

[katch]

Peak torque is still your limit in all situations. I guess if the variator was over geared you could have an automatic gearbox.
You can take your peak torque and instantly use it over variable gearing to spin your own robot against a competitors holding you or pinning you down by your spinner. Who knows. Just because the maths is different doesn't make it wrong. One track minds build one track robots.

[typhoon_driver]

They do but then again a pulley and belt is a far simpler system. With spinners you want the system to be as simple as possible. 500G+ impacts going back through small delicate components is a recipe for a single spin up machine.

[katch]

Probably true, but it would be interesting to do a back to back test or see one in action.

[typhoon_driver]

Get building then

I'm sure a second series of robot wars will be coming along.

[cavecrusher]

Variator/CVT might be a good solution for sensorless bldc motors though.