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Northern Canada
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I need to make a forklift with about 2 inches of travel.  I like the idea of using a servo as I can mooch power right off the Arduino.  The other reason is I would prefer to direct connect without gears or pulleys as latency could be a deal breaker.  I don't want to mount anything to the slotted slab as there is no clearance for it to recess into the shelf at the bottom (the slot bottoms out just above the shelf).

The problem as I see it (aside from the mechanical linkage design), is to convert the rotary motion of the servo to a linear up and down motion.  Here's an illustration of the gizmo.  Any hot construction tips appreciated.

http://theonqgroup.com/pub/xpression.jpg

Carl


* XPression.jpg (38.71 KB, 605x545 - viewed 29 times.)
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Newcastle, England
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Have a look into linear acutators:
http://en.wikipedia.org/wiki/Linear_actuator

They provide the up-down movement a forklift will need.

Onions.
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Tacoma, WA
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Using a servo will require to transfer the radial energy into linear energy, which will increase your load on the motor - unless you did a rack and pinion style linkage - but that would probably be over your budget.

A 5V servo motor will be pretty weak, what do you plan on lifting? Could you use a linear actuator? Most actuators will have an ohm readout which will give you pretty a pretty decent position gain.

Do you need to move something slowly, or simply lift something 2 inches? You might even find a solenoid with a 2" stroke.
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Seattle, WA USA
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Quote
I like the idea of using a servo as I can mooch power right off the Arduino.
Pssst. Wrong.
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Northern Canada
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Quote
A 5V servo motor will be pretty weak, what do you plan on lifting? Could you use a linear actuator? Most actuators will have an ohm readout which will give you pretty a pretty decent position gain

I have a mini 7.5 gram servo that I'm playing with and it appears to have ample torque (using the 5VDC from the Arduino) for the piece that needs to be raised/lowered.  Solenoids won't do it as the position could be anywhere within the travel of slotted bar I'm moving.  The slotted bar is a plastic piece about 4"x.75", so not a lot of mass to move around.

I will look into linear actuators.  Might be the hot tip I'm looking for.

Thanks all!
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Topsham, Vermont USA
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Hi,
Depends on how much force you need; you'll have to figure that out.

There are continuous-rotation servos with lots of torque, like this one:
http://arduino-direct.com/sunshop/index.php?l=product_detail&p=130

15 Kg-cm means with a 2 cm diameter spool you could winch up 15 KG!!  OK, you don't need that much.

A mechanical configuration I really like is the parallel-arm linkage that's shown on this robot which one of my kids built about 10 years ago. (I can hear it begging for an Arduino Reincarnation!)..


This used a floppy drive stepper as the winch motor, and it had a lot less torque than many servos...

...just throwing out ideas...

Anyone seen a Bot with that configuration?  I thought he had a really cool idea back then, even if he was MY kid  smiley
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Northern Canada
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Parallel arm, that's getting somewhere.  Looked into linear actuators, $50 is pretty steep for proof of concept tho.  Trying to locate a motorized fader as used on some digital mixing consoles,  and they have 10 bit resolution to boot!  I think the little motors in these faders might have enough grunt for the light load I'm trying to move.

Thanks,
Carl
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How about this: http://www.sparkfun.com/products/10734
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