[HELP] How to amplify a linear motion?

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TazMan2000

Master Member
Another problem with some of the above suggestions (including mine) is the components tearing apart the gun apart due to vibration. If the gun is made out of metal, no big deal, but I doubt if it would be.

TazMan2000
 

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propmaster2000

Sr Member
Another thing to consider by creating a working item using cartoon physics, is that in real life you have to take into account real
physics.
How much real space you have to work within, momentum and gravity, friction of moving parts, type of materials to be used,
leverage required, power source needed [battery, pressurized air (pneumatic), controller needed, using your finger to move the shaft really fast, etc].
.
 
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zapwizard

Sr Member
RPF PREMIUM MEMBER
This is a bit hard to describe: You could not link the 2nd arm directly to the solenoid. Such that the return stoke of the solenoid, and the return stroke of the 2nd arm operate at different speeds. Due to the speed of the solenoid you could have the solenoid push the 2nd arm further than the 40mm stroke. The 2nd arm would travel further if it had a weaker return spring (or magnet). All this requires low friction however.
 

propmaster2000

Sr Member
ANTALIFE,
So......there has been many suggestions on this thread to give you ideas and facts to think about.
Have you started designing and building a prototype to show your progress?
Just wondering :)
I think you would need some mechanical set up that would give you more of a "SNAP" action in both directions at the
prescribed 80 - 100mm you want, rather then using a motor to drive a shaft.
It might be a bit slower then what you are looking for (based on what the video shows).
.
 
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Zinger

Active Member
Just a thought, could you use a pair of electromagnets instead of a solenoid? One at the front of the stroke and one at the back. Mount a permanent magnet in the bolt you're actuating. Then build a circuit that rapidly flips the polarity of the electromagnets.

Say you mount the permanent magnet with the its North pole facing the front of the stroke. When you pull the trigger, have the current flow through the electromagnets such that their South poles are both facing the bolt. That way the bolt is being pushed and pulled to the front.

S <-- <-- <-- N--S <-- <-- <-- S

At the front of the stroke, reverse the polarity of the electromagnets. Now the bolt is being pushed and pulled to the back.

N --> --> --> N--S --> --> --> N

This would be more compact and a lot lighter than a solenoid with mechanical linkage. That's going to be important because inertia is not your friend here. As someone pointed out above, your prop might tear itself apart under the stress of changing directions that quickly.
 

propmaster2000

Sr Member
The main problem was not "how" to move the shaft in two directions quickly (that's a given) but more how "far" to move the shaft quickly.
The distance needed was indicated in the first post 80mm to 100mm (that's quite a bit using the means suggested so far) as well as the
issues with each means.
A lever and fulcrum, solenoid/electromagnet, motor, servo, pneumatic (needs constant, portable pressurized air, valve and piston setup), space restrictions, etc.
TazMan2000 - I think your right, the thread starter is gone.
.
 
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TazMan2000

Master Member
The main problem was not "how" to move the shaft in two directions quickly (that's a given) but more how "far" to move the shaft quickly.
The distance needed was indicated in the first post 80mm to 100mm (that's quite a bit using the means suggested so far) as well as the
issues with each means.
A lever and fulcrum, solenoid/electromagnet, motor, servo, pneumatic (needs constant, portable pressurized air, valve and piston setup), space restrictions, etc.
TazMan2000 - I think your right, the thread starter is gone.
.

Anything that is going to move and object that far is going to take up some room. You either have to modify your project to accommodate that or go without. At this stage of mankind's existence we still have a limit on how efficient a mechanical device can be that can run on a small battery.

Small
Fast
Cheap

Pick two of the above.
I suppose "Easy" would be a choice as well.

But I like that everyone wanted to help with some creative ideas. This is what this forum is about. Our suggestions may not have helped the OP, but I'm sure it will help a member with another project.

TazMan2000
 

ANTALIFE

New Member
Hello ANTALIFE, did you get anywhere with this?

Also, I came across this mechanism which could also work, but I think modifying/building your own solenoid is the way to go.

(1) Reciprocating linear motion by spiral groove
ANTALIFE,
So......there has been many suggestions on this thread to give you ideas and facts to think about.
Have you started designing and building a prototype to show your progress?
Just wondering :)
I think you would need some mechanical set up that would give you more of a "SNAP" action in both directions at the
prescribed 80 - 100mm you want, rather then using a motor to drive a shaft.
It might be a bit slower then what you are looking for (based on what the video shows).
.


Hi All

Sorry for the long dormant period and thanks heaps for your input!

In the end I decided to use a solenoid + lever combo, which managed to increase my stroke-lengh from ~40mm to ~95mm
Here is a video of how things are looking so far:
 

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TazMan2000

Master Member
There have been a few new members here, who ask for advice when working on a project, that is probably far outside their abilities, and they become disappointed at the advice, which is given to them, because it is way too complicated. This is not the case with you. You took the advice and went far beyond my expectations. You really hit it out of the park. The mechanism works great.

TazMan2000
 

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ANTALIFE

New Member
Did you wind your own solenoid coil?
Yuppo, did end up winding my own in the end out of 0.75mm dia wire

There have been a few new members here, who ask for advice when working on a project, that is probably far outside their abilities, and they become disappointed at the advice, which is given to them, because it is way too complicated. This is not the case with you. You took the advice and went far beyond my expectations. You really hit it out of the park. The mechanism works great.
TazMan2000
This is lovely. Please keep this thread updated with the build, I'm very intrigued :)

Thanks again everyone! I'll go back to posting updates on the project here:
 

propmaster2000

Sr Member
Looking at your video, I could tell it wasn't a store bought coil. To do what you needed, you would need something
with a little more pull...that coil seems to work great.
What kind of power source and oscillator circuit will you be using to drive the solenoid as shown in the video?
.
 

ANTALIFE

New Member
Looking at your video, I could tell it wasn't a store bought coil. To do what you needed, you would need something
with a little more pull...that coil seems to work great.
What kind of power source and oscillator circuit will you be using to drive the solenoid as shown in the video?
.
You have a keen eye for coils ;^]

I'm using a couple of LiFe batteries in series to power the coil at 13.2V. As for the driving circuit, it's a simple MOSFET controlled by PWM from an Arduino Nano

My ultimate goal is to add a couple of sensors to monitor position of the firing pin. That way I won't be dependant on PWM and instead could just turn the coil in until the firing pin reaches the end, and then turn it off until the firing pin reaches the rest position. Would imagine it would help with increasing the firing rate too
 

propmaster2000

Sr Member
Ya, I think you can make a buzzer using a simple relay that way too.
Putting the power through one of the contacts of a relay will cause it to cycle on and off. As the coil energizes
through the contact, power is removed, allowing the contact to close again, reactivating the coil and the action
simply repeats over and over sounding like a small buzzer.
More or less the same concept as you describe. :)

P.S. Maybe a rechargeable battery from a hand tool (drill, etc.) will work good to.
 
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ANTALIFE

New Member
Ya, I think you can make a buzzer using a simple relay that way too.
Putting the power through one of the contacts of a relay will cause it to cycle on and off. As the coil energizes
through the contact, power is removed, allowing the contact to close again, reactivating the coil and the action
simply repeats over and over sounding like a small buzzer :)
P.S. Maybe a rechargeable battery from a hand tool (drill, etc.) will work good to.
Yuppo that's basically the gist of it

And nah, I'll stick with LiFe chemistry batteries. They:
- Give me the voltage I am after for this coil (any higher could cause coil to over heat, think higher current)
- Have a very stable discharge curve, as in the cell voltage is always around 3.3V up until you reach the tipping point
- Are much safer that other lithium based chemistries, as in if you puncture a LiFe battery it will not explode or catch fire
 
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