h a l f b a k e r yI didn't say you were on to something, I said you were on something.
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A ratchet spanner, for example, will turn a nut when cranked in one direction then go click click click when cranked in the other direction. The drive direction can be reversed, or the whole thing taken off and turned around. I want a spanner (type device) that would turn a nut when cranked in one
direction then turn it again when cranked in the other direction. The handle goes backwards and forwards but the rotation produced is always in the same direction.
One Way Ratchet Screwdriver
http://borderex.man...het-Screwdriver.htm
Like this, but with automatic switching? [csea, Nov 13 2008]
Automatic Watch Winding
http://www.brainlub....com/watchpage.html
Pretty good visual depictions. [bleh, Jun 01 2009]
Simple Sketchup rendering of my interpretation.
http://www.prism.ga.../reversinggears.png
Crude, I know, the gears are circles, but I think it gets the point across. [bleh, Jun 01 2009]
Hebelantrieb (no idea about translation)
http://www.reha-tec...rg.de/rollstuhl.htm
for disabled persons who can still use their arms. [loonquawl, Jun 02 2009]
[link]
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Nice - plus it solves that problem where you have to remember which way tightens, and which loosens. |
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Yeah, hadn't thought of that. The application I have in mind is not actually as a spanner but the example serves. |
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I was thinking of a recumbent tricycle with optional hand crank by way of levers at each side. I wanted to have a drive stroke with push and pull. Steering would be side to side. |
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I have a screwdriver that works like that. |
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Does it have a name? You turn it to the right and the screw goes in, you turn it to the left the screw goes in? |
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I don't bring it to work with me so I can't tell you |
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there's a switch on the handle. |
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Ah, but po - I think what we're talking about here is one that automatically switches that switch for you. So instead of turn-switch-turn-switch-turn, all you have to do is turn-turn-turn, with all the switching done for you. |
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Actually, I'm talking rubbish, because in my final turn-turn-turn scenario, the nut would be sort of back where it started - what should happen is that a turnL-turnR-turnL motion on the spanner is translated into a turnL-turnL-turnL motion of the nut/bolt. |
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[zen_tom] That's it. Then a switch could be flicked and the L - R - L - R would translate to R - R - R - R |
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[miasere] I'm not sure I get the second handle bit |
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back to my screwdriver if it's in clockwise mode - I turn and then on the anti-clock motion it goes click, click, click and you can twist the screw in a bit further... |
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I think the second handle is to provide a "frame of reference" by which to create the reverse gear. Without it, you won't get reverse motion. |
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Kind of like those hand pumps which pump on the upstroke as well as the downstroke. |
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Two opposing handles (like scissors) could be used to create reversible single-direction rotation. + |
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po, what you are describing is the well baked one way ratchet screwdriver as per [link] |
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What I want is one where, instead of your click click click, it drives the screw in again. |
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I can see it working in my head with one handle. The scissor action pump handles DO provide one way motion but each handle is either only pull or push, not both |
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yes but it's a two way ratchet screwdriver. |
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this is baked in mechanical automatic winding watch
movements. They have a set of (at least 4) gears which take
the movement of an oscillating weight and translate it to
uni-directional winding of the mainspring. |
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Also in place in mechanical alarm wristwatches. The Vulcain
Cricket winds the mainspring when you wind one direction,
and winds the alarm spring when you wind the other
direction. It uses a simple mechanism which could easily be
applied to do this on a larger scale. |
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Fair comment. Cheers for the pointer |
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[M a M] just wondering if it's for lefthanders. |
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impossible. it would require torque without reaction. |
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"impossible. it would require torque without reaction."
Nope. Just like a regular screwdriver, you're pushing with your feet. |
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"You could do it but you'd need another one to undo nuts."
You could probably rig a switch, but you could also put a head on each end and just flip it over to (un)tighten. |
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[miasere] (and others) are right - you will need another handle to provide the reverse direction.
Think about the motion as axial vectors (horizontally):
Normal: Input -->, Output -->; that's OK
Reverse: Input -->, Output <--; the difference is <----, the reaction required to achieve the output. |
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How does the watch do it? What's wrong with handle movement one way - fine, handle movement other way drops in the extra cog to keep output rotation the same way? |
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As has been pointed out, you can't do it with a single
handle. In effect, you'd be asking the head to turn in the
opposite direction to the applied torque. For this to
happen, there has to be some point of leverage, ie a
second handle. To simplify the problem, imagine the
equivalent problem in linear motion: you're trying to
invent the equivalent of a shovel which pushes forward
even when you pull the handle backwards; it can't work
unless there's a fixed pivot point. |
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In automatic watches, there are various mechanisms, but
they all have a fixed pivot point 'outside' the system, so
that rotation of the weight in one direction can be taken
through a gear (whose axle is the fixed point) to reverse
its direction when necessary. |
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sure, you could use a plantary with a slip clutch but
without an anchor point the whole thing is a disaster. |
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did anyone who bunned this actually think it through? |
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Please, [WcW], remember where you are .... |
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given, but this is a slippery slope. |
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I knew I shouldn't have mentioned a wrench, spanner. Describing turning a nut in the initial description was also not the right thing to do. The both ways ratchet is for handles on a tricycle recumbent. They would have a fixed point, and there would be 2 of them. I still need to have a drive stroke in both directions, not using a crank in the axle. |
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I push forward on the handle and the wheels are driven forward, I pull back on the handle and the wheels are still driven forward. The handles are pivoted somewhere under the seat. |
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The idea is baked if the watch thing comes in but a link or picture would be good. |
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[MaxwellBuchanan] thanks for the shovel explanation, I was struggling with vectors
[WcW] plantary or planetary? |
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planetary. There are plenty of ways to make a ratchet
double acting but they all involve being attached to a
common frame of reference (a torque bridge) that
translates the force. In fact as long as you have some way
to tie down the tool to the work the torque can come from
any source. what you want is a planetary gearset with a
one way clutch on the orbit, drive through the sun gear
and input to the planetary ring . (or the inverse....) this
would allow you to drive forward on both clockwise and
counterclockwise rotation (just as an automatic
transmission does only inverted). You could even have
different gear ratios for push/pull. |
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That word again, impossible.
//they all involve being attached to a common frame of reference//
Like the tricycle frame?
//good leverage for either a push or a pull, not both//
There are two handles, one on each side of the seat (a bit like 'cross country' ski machines, not that they have seats but it is the handles I am refering to) Left hand pushing, right hand pulling. Then right hand pushing, left hand pulling. Body remaining in the middle. Each stroke of each hand turns the wheels forward. |
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I thought it would be a matter of (automatically reversing) gearing |
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I've got a ratcheting overdrive screwdriver - you set the direction, and grab the front part of the handle, and it gives you 3xturn - zzz - 3xturn - zzz; release the front ring and you get 1xturn - zzz - 1xturn - zzz. |
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With the same planetary drive, you could put on 2 ratchet units, one driving a reversing gear, the other direct; they both output to the same shaft into the planetary. Then you would be able to grab the output ring, get turnR - turnR - turnR, release and get zzz - zzz - zzz. Switch both ratchets for turnL, or only one for TFU. |
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nope, the planetary would be better. that way you could
drive from both sides simultaniously. Anyway a better
descrption of the application would really improve the post
and feedback. |
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Sorry, I kinda forgot about this place again.... Georgia Tech
is
a bitch. <linky> for automatic watch winding, but I'm not
sure
it applies to the spanner idea, i think you are going to
need an anchor point. |
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Basically, the watch movement has the drive gear in small
arc shaped channel so that it can move depending on the
input torque. For instance, if input is clockwise, it engages
a train of 2 gears, so that output is also clockwise, If input
is counterclockwise, the drive gear slides over and engages
a train of three gears, thereby reversing the output to
clockwise. I whipped up a little prototype with some clock
gears I had laying around. The trick is when you're turning
the thing in the direction opposite the desired direction,
your going to have a tendency to turn the whole
mechanism, rather than engage the gears. If the screw is
tight enough, the frictional forces may be enough to keep
you from unscrewing, but maybe not. |
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On your tricycle handlebar drive mechanism, the whole
mechanism can be attached to the rigid frame (the frame
acts as the second handle, providing the extra opposing
force) so that it'll
switch every time, but you're gonna have a hell of a time
getting the gears to mesh just right each time, and I
predict some serious jam-ups. |
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Oh, and in my design <also linky>, all the gears will be
turning all the time. I guess you'd need to incorporate a
ratcheting hub on the final output gear similar to a bike
wheel (so that it can keep going forward while the gears
are changing). |
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One more thing: what you're looking for on your tricycle is
a way to turn reciprocating linear motion into constant
rotational motion, which could also be accomplished using
a system similar to steam train engines (a pushrod
attached to the outer rim of the wheel). |
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So i gather this is for driving a vehicle? Baked [link] |
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Back to the question about what's the name of [po]'s screwdriver. |
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I've only got one screwdriver worthy of a name - Phillip. |
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I have a dolly named Salvador, and a pan named Chopin. |
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Most ratchets have a little switch on them to reverse direction. (Righty - Tighty, Lefty - Loosie). |
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Ratchet. Isn't that what certain rodents do in unwelcomed places? |
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