Ace is NOT the place!!!

A quick rant tonight.  Got the cutting done for block lifter V0.2, I only made a couple of mistakes, nothing a little grinding with the Dremel won't fix.  In V0.2 I decided to use 1/8" (3mm) wooden dowels for alignment this time around, they should impart better alignment than the metal rods I was using (I've had better success with wood dowels in other projects).  So, I'm running around doing errands and I decide to duck into Ace and pick up an 1/8" dowel or two. Because "Ace is the Place", right?  The ads that I've seen on TV tell me that Ace is a no hassel place to pick up things you need for any project you're doing.  They have friendly helpful staff who will help me find what I need, that's what the ad says...  Well, wrong on both counts, no help, no dowels to be found.  Now I have to wait till I can make it over to Home Despot before I can start gluing things up.  To hell with you Ace!!!

(The place that has stuff when Ace doesn't)

(The place that also doesn't have stuff)

Obsolete but not neglected...

With a bit of spare time I decided to get block lifter V0.1 a bit more assembled.  I'd still like to see how well or poorly this design works.  As noted, my drill holes are not super precise (and the alignment of a number of key parts was a bit skewed while they were being epoxied together), so my trusty hand reamer got some good use today.  Here are some shots of the assembled rack carriage as well as shot of the carriage held in the block (held together with a rubber band).

The vertical slide poles will be cut down to size (that is to say, there is a top to the block).

A view of the rack carriage as it will be when assembly is completed.

These screws are way too long, plus they're pan heads and to light in color.  If I can find them I'd like to get some black anodized countersunk screws.

Behold the ugly as sin panhead screws.  Just plain fugly.

The rack in all of its glory.

  

Plan and Perspective view

A couple of shots of the drone design in plan and perspective plan view.

More drone stuff

After reading on the web and in the model airplane design book I've come to the conclusion that using a ducted fan (which the last concept model reflected) would defeat the purpose of my design.  Ducted fans are noisy and inefficient (sadly)which makes sense though, smaller bades that need to spin faster (thus approaching the sound barrier and making more noise).  Anyway this redesign drops the scoop on top, adds a camera lens detail and a prop. 

The constant drone...

of madness, gnawing away at my psyche.  Actually not, just looking for a semi-clever way to work the word "drone" into my post's title.  Anyway, read random sections of the model aircraft design book and learned that some of my design ideas for a drone are on the right track.  I felt like modeling this evening so I threw this design concept together (even bothering to use the recommended airfoil shape for a swept flying wing design).

Droning on...

For the past couple of months I've been obsessed by my active labyrinth project (hence this blog).  At about the same time I got this bug to build my own UAV (drone), and apparently I'm not the only one, as evidenced by this site.  All I've got to say is, +Timothy Carstens this is all your fault.  Anyway I've suckered myself into buying a book on model aircraft design.  At a first glance this book covers everything I need, so if you want a book that seriously dumbs down (to simple-ish algebraic formulas and backed up by some straight forward calculus) the complicated field of fluid mechanics as it applies to fixed wing aircraft have a gander.

Once I've had a chance to digest some of the information perhaps I'll throw together a 3D model or two of what I'm thinking.

 

Obsessive Compulsive Design

Since I'm not pestering +Andrzej F to use the laser cutter at the moment I've applied myself to designing block lifter V0.2 (in addition to building garden beds and trying to satisfy an unsatisfiable client).  I think I'm getting a little lost in the design process...

Mortis and Tenon...

More technical activities have been superseded by building garden beds for the wife.  As opposed to doing it the easy way, which might have taken an hour, we opted to use a mortis and tenon joints.  Hailed as the strongest joints one can make with wood, the beds took me about 7 hours (half of which was spent figuring out the best way to do a mortis and tenon with the tools I had on hand).  A plunging router with a 1/2" chuck coupled with a mortising bit would have made life so much easier, alas I made do with my 3/8" chuck router coupled with a drill and a shitty Ryobi jigsaw (which couldn't cut a straight, vertical incision to save it's life).  Note: I have plenty of Ryobi power tools, they're cheap (I don't needs something a tradesman would, so I opt to pay 1/3 of the price for most of my tools) and generally get the job done, but not this damn things (it started out subpar and has continued to disappoint).  Anyway, here are the results of plenty of sweat, a few splinters and lots of wood chips:

(5'x3' bed)

(behold the strongest of joints)

UPDATE: Vivisection of a servo

Just spent an hour removing the physical stops from a variety of locations on the gear train, resulting in a broken pressure fit shaft socket.  The pressure fit shaft socket required some high precision grinding, too precise for my ham-fisted self, but only after the damn plastic piece cracked as I was clamping it in the vice.  Tried to reassemble the thing with it's broken socket (it still fit, but not as precisely as before breaking), no dice, the alignment is off and will never be right.  All this to say, my mechanical hacking skills are far below that of a remedial,  apprentice watch maker, and I have failed.  Even if I were successful with this hack it would still be too time consuming for mass production.  I'll just have to find some other small, inexpensive, bi-directional electric motor.

Vivisection of a servo

I'm redesigning the block lifting mechanism, version 0.1 (everything you've seen up till now) is too Rube Goldberg-ish (too many moving parts that rely upon the goodwill of the universe for alignment and proper functioning).  It'd probably work if I were a mechanical engineer, but I'm not, so discretion is the better part of valor.  That being said I plan on finishing 0.1 just to see it work (pictures and video will be taken and posted).  Anyway, I was struck by inspiration while I was daydreaming about a potential future project that involves a power screw to lift portions the sculpture.  Ugh, so blindingly obvious, use power screws to lift and lower the blocks.  Each block can be independently raised lowered with with power screws driven by small continuous rotation servos.  This solution would eliminate the need for a higher voltage power system just for the solenoids (to engage the rack and pinion), springs to counterbalance the solenoids (to disengage the rack and pinion) and the rack and pinion.

To this end, I've started looking at inexpensive continuous rotation servos.  One solution that +Jason Hoff suggested is modifying a Tower Pro MG90S servo (I have a couple laying around).  There are a number of tutorials claiming to modify this servo (they're usually not, people generally modify the TGY-90S which has nylon gears), so I disassembled one of the MG90S to see how difficult modding it would be for continuous rotation.  Here are some shots of the vivisected servo, I want my trusty EE to look at the circuitry before I start soldering in resistors and bypassing potentiometers (the MG90S looks a bit more complex than the TGY-90S).  So, once Jason has his ankle bolted back together and he's off heavy tranquilizers I'll see what he thinks.

(lovely, durable metal gears)

(stops that need to be ground down)

Block lifter V0.2 schematics will be forthcoming soon.  Once I've figured out how to mod this little beast I'll post a full and detailed tutorial (as opposed to a video of the the final result and vague instructions on what's needed and how to do it).

You get what you pay for...

(image included for visual interest)

For this project I purchased a drill press accessory for my trusty Dremel.  It's less accurate than I was hoping it would be, unfortunately the Dremel is light weight enough (and spins at between 5000 and 35,000 rpm) that the drill bit has a tendency to wobble and flop around.  This lead to some imprecise drilling today; in places where precision is important I'll have to fudge things with larger holes and some extra epoxy.  In light of these facts I'll be redesigning many of the parts to make the assembly process simpler and faster (with larger alignment dowels / rods).  Much of the design complexity was due to channels I made for screws and shafts, I'm now thinking life can be simplified (and made more accurate) with a drill template for each piece.  A real drill press would probably help as well. 

The Epoch of Epoxy...

The past couple of days have consisted of using a variety epoxy based adhesives to stick small bits of wood together.  Behold the result of JB weld, slow setting epoxy and fast setting epoxy...

In terms of adhesives I like the consistency and strength of JB weld, but it's ugly as sin where it oozes out on to the wood.  The fast setting epoxy (5 minutes) seems to set too quickly for the applications I am using it for.  The slow setting stuff is generally a nice compromise, but it's not tacky enough for some situations.

When the glue age comes to a close it'll be time to move on to drilling out the parts...

Think this design is intricate enough...

I have a feeling I'm going to need to redesign this particular part for the main prototype.  Laminating these parts is pretty time consuming.

Laser Cutter = AWESOME!!!

First of all, I'd like to thank the guys at the WiESEL group again for the use of their laser cutter, you guys rock.  +Andrzej F thanks for taking the time and lending your expertise to help me get the cutting done.  The cutting went really well (with the exception of me forgetting to include a part on the 1/8" sheet of wood, gotta go back an cut that part tomorrow).  Now the work of gluing and bolting it all together starts.  I loosened up the part tolerances (from what I've done in previous projects), it makes things easier to fit together, BUT in some cases I went too far and aligning the pieces while they're setting up (with glue) is going to be a pain.  Check out some of the videos and pictures of the cutting process and results.

(the first 1/4" sheet of plywood)

(the 1/8" sheet of ply wood, faster to cut)

(The outer portion of this prototype assembly)

(The rack and pinion, hope the hold together during testing)

(The block itself)

 

Parts, parts, parts...

Almost done with designing the parts to be cut by the laser cutter. Got time scheduled on Thursday.