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Just to keep two generic threads on the go at once (and hoping this is of use to more than me)...
Shock mounting things is a good idea, in a modern day and age. I can see how to insulate my electronics from someone folding my frame in half, and I know about mounting the gearbox as a sub-frame so that when the outer frame gets a whack the drive keeps going. I know about Bigger Brothers two-level frame, and Ive been the instigator of a long rant about whether frames should be designed to bend or not.
I know about soldering the end cap on to motors, and using something sturdy to hold the magnets in place. I certainly know not to leave anything other than a very short bit of axle cantilevered, and obviously not to make the motor axle take the weight. I even know to put enough slip in the wheels that the motor cant stall (unless Ive got current limiting, at least), although how your gearbox is supposed to survive Growler grabbing hold of you, putting his weight on the robot, and spinning the wheels quickly is somewhat lost on me (Im surprised there werent more casualties).
I can just about suss mounting an axle with suspension and a chain drive with a spring-mounted tensioner so that the axle can move a bit relative to the motor - although once youre into long chains with active movement it seems to be mostly a matter of time before something goes pear shaped. And Im aware of the suspension wonders of pneumatic tyres (with a foam filling, as WJ demonstrated), and the benefits of leaving a bit of slack around everything should your frame get bent (demonstrators: George Francis and Andrew Marchant, several times).
So, question: how do you shock mount a drive train? Its not clear to me how one big whack on an axle doesnt throw everything out of step (although an enormous axle obviously helps). My moral objections to the Drop Zone were mostly based on it giving the drive train a whack from a direction it wasnt designed to support, and possibly doing something expensive as a result. Lots of robots fail due to something happening to their drive, some less than others, and Im sure people have given it a lot of thought. Rather than reinvent the wheel (as it were, unless thats the solution), I thought Id ask. :-)
To clarify the question: how do you allow movement in the wheel in all the directions it could get shocked without that shock being transmitted to something delicate and expensive (like a motor)? How do you handle the axle being bent without the drive train being compromised? Other than trying to make the thing so solid that nothing can happen to it, which isnt an approach I really believe in, how do you transmit torque with as many degrees of freedom as possible? How do you stop excess torque (Growler) from knackering the drive?
Am I being overly paranoid here? I can come up with something bizarre with CV joints, rubber shock absorbers (as Diesector uses for the hammers) and some form of slip-release, but Ive seen no sign of any such thing on existing robots. Perhaps I should build it and see whether anyone can break it. :-) (Of course, itll weigh so much than I can only put 1mm of polycarb over the top, but axes are getting rare these days...)
I do have one or two other ideas, but theyre based on odd robot shapes and arent all that useful in the general case. Anyone care to share their techniques? (Gary - this pretty standard shock mounting of yours? Ed - or do you just build everything out of 20mm Ti?)
Thanks everyone for their informative answers to by general questions in the past. Here we go again. :-)
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Fluppet
Shock mounting things is a good idea, in a modern day and age. I can see how to insulate my electronics from someone folding my frame in half, and I know about mounting the gearbox as a sub-frame so that when the outer frame gets a whack the drive keeps going. I know about Bigger Brothers two-level frame, and Ive been the instigator of a long rant about whether frames should be designed to bend or not.
I know about soldering the end cap on to motors, and using something sturdy to hold the magnets in place. I certainly know not to leave anything other than a very short bit of axle cantilevered, and obviously not to make the motor axle take the weight. I even know to put enough slip in the wheels that the motor cant stall (unless Ive got current limiting, at least), although how your gearbox is supposed to survive Growler grabbing hold of you, putting his weight on the robot, and spinning the wheels quickly is somewhat lost on me (Im surprised there werent more casualties).
I can just about suss mounting an axle with suspension and a chain drive with a spring-mounted tensioner so that the axle can move a bit relative to the motor - although once youre into long chains with active movement it seems to be mostly a matter of time before something goes pear shaped. And Im aware of the suspension wonders of pneumatic tyres (with a foam filling, as WJ demonstrated), and the benefits of leaving a bit of slack around everything should your frame get bent (demonstrators: George Francis and Andrew Marchant, several times).
So, question: how do you shock mount a drive train? Its not clear to me how one big whack on an axle doesnt throw everything out of step (although an enormous axle obviously helps). My moral objections to the Drop Zone were mostly based on it giving the drive train a whack from a direction it wasnt designed to support, and possibly doing something expensive as a result. Lots of robots fail due to something happening to their drive, some less than others, and Im sure people have given it a lot of thought. Rather than reinvent the wheel (as it were, unless thats the solution), I thought Id ask. :-)
To clarify the question: how do you allow movement in the wheel in all the directions it could get shocked without that shock being transmitted to something delicate and expensive (like a motor)? How do you handle the axle being bent without the drive train being compromised? Other than trying to make the thing so solid that nothing can happen to it, which isnt an approach I really believe in, how do you transmit torque with as many degrees of freedom as possible? How do you stop excess torque (Growler) from knackering the drive?
Am I being overly paranoid here? I can come up with something bizarre with CV joints, rubber shock absorbers (as Diesector uses for the hammers) and some form of slip-release, but Ive seen no sign of any such thing on existing robots. Perhaps I should build it and see whether anyone can break it. :-) (Of course, itll weigh so much than I can only put 1mm of polycarb over the top, but axes are getting rare these days...)
I do have one or two other ideas, but theyre based on odd robot shapes and arent all that useful in the general case. Anyone care to share their techniques? (Gary - this pretty standard shock mounting of yours? Ed - or do you just build everything out of 20mm Ti?)
Thanks everyone for their informative answers to by general questions in the past. Here we go again. :-)
--
Fluppet
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