An engineering challenge - speeder related

[Le Chuck]

In an effort to keep my build thread focused what's actually been built I'm yet again posting harebrained related questions for group brainstorming.

I need to selectively connect two square axles.  This will allow me to use the left and right speeder handles independently or in unison.  My plan is to linearly actuate a collar bearing mounted square-holed sleeve across a gap a RCH wide between the two axles. 

I'm in love with this: but it costs a measly $1500 with controller for an inch of travel.  F that. 

Here's what I'm thinking:  DC motor connected to a rail similar to what's on TJC's CP slides with two limit switches.  Put the rail in the middle and two guide rails on either side then just mount my axle joining bracket to a base plate on all of that.  Whole shebang should take up 3 or 4 inches and only needs to actuate an inch either direction.  Motor wired to a DPDT. 

Crazy, ludicrous, just might work?  Is there a better way to skin this cat?  What parts would you all recommend I start loading into my shopping cart.  I am not opposed to spending money on this to work, I've looked at micro-slide tables and really like those but am not sure how to actuate them as is so building one of my own came to mind. I just don't want to break the bank over a trite feature. 

Thanks!

[Nephasth]

First thing that came to my mind was how tractor brake pedals are set up...

[yaksplat]

This made me think of the hi-low gear on my lathe.  When you want the lathe in high speed you manually push a pin that connects the  gear to the shaft.

To put it back in low you pull the pin out and reconnect the reversing gear.



With the limited amount of travel that you should have, you should be able to  automate a pin, or several pins on a collar that are spring loaded and actuated with a solenoid.

[BadMouth]

I'm not coming up with anything better than the square collar and linear actuator.
(picturing it attached to one axle and extending a collar to the other axle when activated)
Surplus Center has some real cheap ones without limit switches, but built in ones would eliminate a lot of parts.
http://www.surpluscenter.com/item.asp?item=5-1783&catname=
Not sure if you'll already have a 24v source, but the draw is low enough it could be powered from a laptop brick.

EDIT:  probably need to ensure that the collar doesn't move until the axles are aligned. (handles in same position)
          I can see kids messing that up real fast. hmm.....

EDIT 2: maybe have the collar spring loaded in the linked direction and have it ride against a panel that is keyed in such a way that it will only slide through when the axles are aligned properly.  The actuator would keep the spring compressed when in "separate" mode.  Not real crazy about having surfaces riding against each other, but it would only do that until the operator moved the handles to the same position.

[Le Chuck]

probably need to ensure that the collar doesn't move until the axles are aligned. (handles in same position)
          I can see kids messing that up real fast. hmm.....

Good call!  I have limit stops from the SWRA throttle bodies that I'll be using and there is plenty of room to mod a limit switch onto those.  I can put one on each and wire them together so that the handlebars both have to be all the way back before the switch will activate (just hack into the ground I imagine).  I have also toyed with getting a locking switch cover for that control since it's not something that I want folks messing with... plus those locking switch plates are teh kewlz. 

As for spring loaded... I'm gonna call that one out of my range of abilities, for now at least.  I need to sit down and evaluate doing a motor vs a linear actuator.  That LA you linked to can push 100+ lbs and is somewhat overkill since this is not really a load bearing or torqued application, but the size is right and the price isn't bad. 

Yak & Nep - I love this place because I get the coolest ideas of stuff that I get to go research and figure out how it works.  Chasing the rabbit is how I get most of my ideas anyway.   

[yaksplat]

Spring loaded is simple.  Just take a pin, two clips, a spring and the mating plate.


I'm thinking of a pin that's at least 1/4" - 3/8" in diameter.

Cut two grooves in the pin, one beyond the insertion depth of the pin and the other at the opposite end.  Circlips go in the grooves and hold the pin in place and spring load it.

Excuse the crude paint drawing.

[Le Chuck]

Okay but how to I remotely control that and mount all of that stuff to the axle?  Not being a smartass, really asking. 

[Nephasth]

Looks easy to mount, even has the 3/8" plunger recommended earlier. And only $16.45 shipped!

[MacGyver]

Just magnets.  Really strong neo-magnets?  So when they are near, they join, but can be split by a normal strength person to use them independently.

[Le Chuck]

Looks easy to mount, even has the 3/8" plunger recommended earlier. And only $16.45 shipped!

I thought solenoids had to have constant current to remain at state?  This would be a concern, also that's three pounds I'm putting on my axle... hmm, good idea tho. 

Just magnets.  Really strong neo-magnets?  So when they are near, they join, but can be split by a normal strength person to use them independently.

What's to stop them from catching during independent use?  Seems like a hiccup with that would mess with gameplay.  Maybe electromagnets... that way there would be no extra moving parts, but again, would have to be under current the whole time and could potentially burn out. 

[BadMouth]

Just magnets.  Really strong neo-magnets?  So when they are near, they join, but can be split by a normal strength person to use them independently.

What's to stop them from catching during independent use?  Seems like a hiccup with that would mess with gameplay.  Maybe electromagnets... that way there would be no extra moving parts, but again, would have to be under current the whole time and could potentially burn out.

I gave a fair amount of thought to using a magnetic AC compressor clutch for a 360/270 degree steering wheel project. 
  Plenty strong enough, but they pull a LOT of current.  I was also afraid that having that strong of a magnet near the monitor/computer/user might lead to other issues.

Attached is my entry for worst drawing in paint.
I left some stuff out to keep it from looking too complicated.
The actuator would attach to the right axle.  The point where it attaches to the middle part would slip, so it doesn't push the center part, but just allows the spring to move it.
There would be a plate on the end of the middle part keyed in such a way that the left axle could only go in when they are lined up.
If the axles have less than 90 degrees of rotation, this might not even be a problem as there would only be one point where the two square pieces could slip together.

[Le Chuck]

Makes sense.  I was just looking at some 2"dia electromagnets.  At 12v the hold is over 200lbs.  Threaded for 1/4".  Wondering how simple it would be to just pop one of those $50 bad boys on the end of one axle and but up a steel plate on the end of the other.  Don't know if it would stand up to the rotational forces, it'll hold but will it stop spin?  For that matter I'm sure I can find some pin solenoids that could do the trick (like the one on ebay linked previously) but I still really like the idea of a connection that is not subject to active current in either state.  Still, an axle mounted solenoid interfacing with a bracket on the other axle is a lot easier to implement than a motor driven sliding plate system with bearing supported sleeves.  Yech.  Hrm.  Option 5 anyone?

[Le Chuck]

Looking at locking solenoids now.  I'm more comfortable with power consumption in the independent handle config since it will be less used (SWRA only), plus if it fails it locks and everything is still functional (more or less)

Update - Need to find a source for bistable solenoids.  Only need current on fire and aren't spring loaded.  Pretty schnazzy.  So far I just have spec sheets and no prices.  Tentatively stoked but somewhat intimidated by the complete lack of pricing data. 

[PL1]

Here's another possibility that is bistable, doesn't matter if the handles are aligned when the switch occurs, and uses a linear actuator with a short throw.

The left throttle collar (green) and right throttle collar (blue) both turn independently of each other around the throttle axle. (yellow)

The coupling collar (gray) fits over and turns with the right throttle collar.  It has a spring loaded pin that goes through the right throttle collar

The linear actuator (light blue) has a screw head (red) on the end that passes through the curved red slot shown in the side view. The screw head and actuator shaft are both too large to pass through the slot.  Use a small bushing (not shown) to protect the threads of the screw.  The actuator is mounted to the speeder body and does not move with the throttles.

When the actuator extends, it pushes the coupling collar forward.  If the pin is not aligned with the hole in the left throttle collar, the spring is compressed until the handles are placed in the same position and the pin pops into place.


Scott

Edit: Updated attachment for greater clarity.

[Le Chuck]

That's a fairly elegant solution, and given that I only have 60 degrees of handlebar movement is more than adequate.  It will require more machining but could use a very small LA.  Rather than deal with the curved slot I'd probably just mount the LA to the axle and affix the collar bushing to the LA directly.  I'll be contacting Kuhnke Controls tomorrow to check on the door locker solenoid but if that's a bust I'll probably work on a variant of what you displayed. 

[PL1]

Thanks.

Here's another version with the LA mounted to the right throttle collar.

The orange are springs so that the LA can go in or out and it puts tension on one spring or the other without forcing the pin to move.  This prevents damage if someone is pressing the throttles in opposite directions so that the pin binds.

The black dots are holes through the shaft. Use mechanics wire and the correct size washer to make a spring stop like on my mouse shooter.  (Parts list here.)




Scott

[Le Chuck]

The orange are springs so that the LA can go in or out and it puts tension on one spring or the other without forcing the pin to move. 

I understand your english words but don't get what the springs are doing.  The LA will go in or out without those springs, how do they aid the mechanism? 

I'm liking your design because I've switched to round axle (cost benefit analysis... something about spending $100 just on sleeves when a welded washer with a set screw will do the same thing on the handle connection).  This outs my previous idea of a sliding collar so I'm pretty much committed to some small factor LA.  Running a pin through some flanged bushings that are welded onto the rod ends will work pretty well I think. 

[PL1]

The orange are springs so that the LA can go in or out and it puts tension on one spring or the other without forcing the pin to move. 

I understand your english words but don't get what the springs are doing.  The LA will go in or out without those springs, how do they aid the mechanism? 

The pin needs to fit snugly and only move in or out when the handles are lined up.

If the pin is to the right (disengaged) and the handles are uneven when the actuator moves to the left, the coupling collar pushes against the left spring.  When the handles are lined up, the spring pushes the pin through the hole in the left throttle flange, locking the handles together.  The spring pushes against the pin which keeps it locked.

When the actuator moves to the right, if there is uneven pressure on the handles, it can cause the pin can bind.  The coupling collar pushes against the right spring.  When the uneven pressure on the handles is released, the spring pushes the pin to the right and it disengages.  The spring pushes against the pin keeping it unlocked.

By using the springs, the hardest pushing/pulling force on the linear actuator is the amount of pressure provided by the springs.  Without the springs, a light actuator could easily exceed specs/fail or a strong actuator could damage the setup.


Scott

[Le Chuck]

^ ah.  Makes sense.