Crusher, why not?

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Lowtech
Posts: 56
Joined: Thu Aug 11, 2011 11:02 am

Re: Crusher, why not?

Post by Lowtech »

EddieJ wrote: Mon Mar 08, 2021 8:06 pm Have you got some electronic scales it can bite down on? Perhaps measure what force you are getting now, to see if you are far off the 3.5kg?
Im not sure what amps the Rx will output.
Mmm, that's an idea. I don't have a small enough scale, but my neighbours might!
Firestorm-in-a-teacup (2WD front hinged flipper)
Hydrant (4WD crusher) (in progress)
Ant Ipodean
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Location: Auckland, New Zealand

Re: Crusher, why not?

Post by Ant Ipodean »

It seems that when you are measuring "force" here, you are really meaning torque, which must be defined by pressure AND distance from the centre of rotation.
eg foot pounds, inch ounces, Kg cm, etc.
Perhaps the force you are quoted are at 1cm?
Then if the crusher point is 2cm from it's centre of rotation, the force is half of that.
If its 3cm, the force is a third, etc.

Mike.
Lowtech
Posts: 56
Joined: Thu Aug 11, 2011 11:02 am

Re: Crusher, why not?

Post by Lowtech »

Ant Ipodean wrote: Tue Mar 09, 2021 12:16 am It seems that when you are measuring "force" here, you are really meaning torque, which must be defined by pressure AND distance from the centre of rotation.
eg foot pounds, inch ounces, Kg cm, etc.
Perhaps the force you are quoted are at 1cm?
Then if the crusher point is 2cm from it's centre of rotation, the force is half of that.
If its 3cm, the force is a third, etc.

Mike.
Good question. Yes I used torque as the starting point in my calculation. The motor should have about 13.7 Kg*cm of torque, as the tip is 3.9 cm away from the axis of rotation.

Fyi, I charged the battery up to full and there was a slight improvement. The cardboard box became more concaved under pressure.

I'm beginning to wonder if upping the voltage to 7.4V and/or increasing the current might not put strain on the motor.

Does anyone know how pololu motors handle being stalled for prolonged periods? Realistically, if I can't crush an opponent I have to grab it. So the motor could be stalled for much of the fight.
Firestorm-in-a-teacup (2WD front hinged flipper)
Hydrant (4WD crusher) (in progress)
Fasthippy
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Joined: Mon Mar 15, 2021 5:31 am

Re: Crusher, why not?

Post by Fasthippy »

I feel that you are pushing that motor to its limits. Even with all the gearing you are likely getting inefficiency and such throughout the gear and its about maxed out. For a crusher weapon you might want to consider a system that is specifically built for this application- a linear actuators such as this:

Actuonix L16 Actuator 50mm 63:1 6V RC Control (on amazon)
ttps://www.amazon.com/Actuonix-L16-Actuator-50 ... AndDetails

There are actuators even smaller than the L16- https://www.actuonix.com/L12-Micro-Line ... s/1821.htm

These systems come with its own motor and gearing and use a screw rod and bolt to create its linear motion. These seems to be what the other mentioned bot was using. These systems are designed to handle high torque load and should be more robust that a hand made geared down thing. You might even be able to increase the load with a pivot point that is of uneven length. These are unidirectional systems but they seem to be plug and play like a servo.
Henwilled Antweight team
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Re: Crusher, why not?

Post by Henwilled Antweight team »

It's looking very good... What method of crushing are you using? Curious because I've been using large servos, but they weigh an awful lot, are you using hydraulics of some sort or other?
Lowtech
Posts: 56
Joined: Thu Aug 11, 2011 11:02 am

Re: Crusher, why not?

Post by Lowtech »

Fasthippy wrote: Wed Mar 17, 2021 3:16 am I feel that you are pushing that motor to its limits. Even with all the gearing you are likely getting inefficiency and such throughout the gear and its about maxed out. For a crusher weapon you might want to consider a system that is specifically built for this application- a linear actuators such as this:

Actuonix L16 Actuator 50mm 63:1 6V RC Control (on amazon)
ttps://www.amazon.com/Actuonix-L16-Actuator-50 ... AndDetails

There are actuators even smaller than the L16- https://www.actuonix.com/L12-Micro-Line ... s/1821.htm

These systems come with its own motor and gearing and use a screw rod and bolt to create its linear motion. These seems to be what the other mentioned bot was using. These systems are designed to handle high torque load and should be more robust that a hand made geared down thing. You might even be able to increase the load with a pivot point that is of uneven length. These are unidirectional systems but they seem to be plug and play like a servo.
You know, I might just have to accept that at some point. I think I'll test it at 7.4V and see it works, then leave it at that. The price of linear actuators is surprisingly high it seems.
Firestorm-in-a-teacup (2WD front hinged flipper)
Hydrant (4WD crusher) (in progress)
Lowtech
Posts: 56
Joined: Thu Aug 11, 2011 11:02 am

Re: Crusher, why not?

Post by Lowtech »

Henwilled Antweight team wrote: Wed Mar 17, 2021 7:42 pm It's looking very good... What method of crushing are you using? Curious because I've been using large servos, but they weigh an awful lot, are you using hydraulics of some sort or other?
I'm using a Pololu Micro Metal Gear motor with an extra gearbox screwed on. I can't remember the model, but you will find many such motors quite quickly on Google...
Firestorm-in-a-teacup (2WD front hinged flipper)
Hydrant (4WD crusher) (in progress)
Fasthippy
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Joined: Mon Mar 15, 2021 5:31 am

Re: Crusher, why not?

Post by Fasthippy »

"You know, I might just have to accept that at some point. I think I'll test it at 7.4V and see it works, then leave it at that. The price of linear actuators is surprisingly high it seems."

You might be able to build your own- its a geared down motor turning a screw rod. A bolt rides on the rod and turns the motor motion into linear motion. It may even be 3s printable but ya you will want pretty strong motors and gear boxes and such to handle the high torque, it likely that your getting gear slippage or whatnot that is limiting you system. Than again building your own has its own risks... they are not cheap but they are solid... ugh.
Fasthippy
Posts: 5
Joined: Mon Mar 15, 2021 5:31 am

Re: Crusher, why not?

Post by Fasthippy »

Another idea would be to use pully mechanical advantage. It would seem easy enough to 3d print a pully with multiple runs and you could multiply you motor power several times... I have no idea how to make this work in a practical sense but its an idea...
Fasthippy
Posts: 5
Joined: Mon Mar 15, 2021 5:31 am

Re: Crusher, why not?

Post by Fasthippy »

One other thing to consider. Most flippers use the properties of class three levers to multiply their speed. This is why bronco or other flippers have there piston mid arm with the fulcrum in the back.

For a crusher you may want to think a second class crusher (think nutcracker or nail clippers). You force is at one end and the fulcrum is near the pinch point at opposite end. If you can get them in the jaw you should be able multiply the force and break em open like a nut. Even at ant weights if you can design the jaw right you may be able to get enough force to actually crack them but it would require smart design.
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