CEF speed contest Design Discussions

I'm WAY behind with the Rare Bear... I did a lot of little odds and ends this weekend. Little odds and ends add up to a LOT of time!
This is one of many custom .040" aluminum bell-cranks I made in 3 sizes on a CNC router years ago. I'm finally getting to use one of the smallest ones. The bearing is acrylic and was also routered. Lead-outs are .031" music-wire.





I still haven't soldered my tank(s) yet.. but I'm hoping that this setup will help with the task.  

Cribbs74 wrote:Yeah Man!

I'll second what Jim said. Those solids look great!

Ron

Thanks guys.. It had been quite a while since I'd made any. As I mentioned; this set is .031" dia. music-wire... a little "over-kill", but the only other choice on hand was .015"... too small for this app. in my opinion.

Not sure if this will help.. but I use 2 tools to bend the wire; The three 90 degree bends are made using needle-nose pliers; starting at a little over an inch from the wire's end. This leaves a "tang" to be coil-wound, and should be perpendicular to the long wire and ON TOP OF/OVER IT. I'm right-handed... so I position the wire so that the "work" is to the left, with the "tang" facing away from me and "over" the long wire. I then use a small locking-pliers in my left hand, to hold the last "bend" tight while I "wind" the coil with my right hand, using the needle-nose pliers. The .031" wire is the toughest to wind, I'll admit. If you have some .025" wire (I didn't...) it's much easier to wind. (having a bell-crank flopping around doesn't make things any easier either.. it gets attached after the 2nd.. and before the last 90 degree bend)

Make sure before you form both ends of your lead-out... that you "thread" whatever you're using for guides on FIRST.
If you forget.. it will make you rather upset!    

Roddie

EDIT: this photo shows .025" music-wire that I formed for a tail-hook for my pin-stooge. The hook "floats" on the tail-gear strut and stows under the fuse for when photos are taken. Most of my airplanes have a stooge hook of some kind.. and it's usually the means for "hanging" them on a wall... in the "Hangar"!

ian1954 wrote:I am seeing some fine pieces of miniature metal work here. Be careful with the crocodile clips on the helping hands - they are not very strong!

I have bust a few "helping hands" including the magnifying glass (it overbalances easily). I have melted a crocodile clip but ............. they are so useful, I keep buying another one!

Hi Ian, I'm not sure you noticed in the photo.. but I made "soft-jaws" for the Crocodile clips on my "helping-hands" fixture. I made them by cutting pieces 1/4" x 3/4" of bicycle tire "inner-tube" rubber... and facing one side with thin-film double-sided tape to "stick" to the jaws.

I try to protect all my lenses-magnifiers/reader/safety-glasses etc. by storing them in clear plastic bags until ready for use.

The "purely... and undeniably... OCD Roddie"

pkrankow wrote:So much effort for soft jaws... medium silicone fuel line is so much easier and it is heat resistant.

Phil

but Phil... medium Silicone fuel line has a wall thickness of .060"... and it's expensive/precious! My inner-tube "flat-pad" material with film-tape measures .050" thick.. (with the adhesives' liner...) That works out to + .020" more of a bite with the Crocodile clip...  ... and a more stable clamping surface area... and the rubber is heat resistant enough for my home-made Cox muffler bodies to seal a hot engine cylinder.

The "purely... and undeniably... OCD Roddie"

I finally got the nerve to start soldering the 1st of 4 tanks to test. Another lesson in patience... I used a 40w. iron with a long pointed tip, .022" dia. 62/36/2 Silver bearing solder and "Ruby-Fluid" paste flux. All that's left with this one is to solder the rear cap on, solvent-flush and leak test. I couldn't have done this work without a lighted magnifier... and it took me a good part of 5 hours... but that was with screwing around with different methods/fixturing etc. The other tanks should be easier.. and take a lot less time.

This is a uni-flow vent arrangement with a fill-tube that gets capped during running.

Roddie

RknRusty wrote:You got a good hot flow on the outside joints. Those look perfect.

Thanks Rusty.. It definitely took some time. I had thoughts on testing the tanks on a short "RTP" tethered dolly, to see how they flow. It would be simple to build, and I would imagine a 10 ft. tether would produce higher "G's" than would be encountered on the 42 ft. lines we'll be using for the contest. It might help to see if shims are needed.

Roddie

ian1954 wrote:The first few tanks always take a while - soldering them up isn't as easy as it looks! These look very neat.

I would be surprised if skin, hot solder, metal and the iron didn't make acquaintence at some time. This is 3D soldering and manipulating everything for a continuous run isn't always simple.

Solder in one hand, iron/torch in the other - I usually manage to burn my lip! I often use my teeth to pull solder from the reel or bend the end .... often forget it is hot!

Nice work - the metal work on those tanks is very neat.

Thanks much Ian, I "did" use the helping-hands fixture for a couple operations... particularly the "angled" uni-flow tube where it sits atop the pick-up tube at the rear.

I soldered the body-seam 1st.. followed by the front cap (it's definitely worth taking the extra time to dry-fit all the panels; tight and square)...

I cut a balsa gage-block to fit inside the rear body while standing on end to set the depth of the feed tube, while soldering it into the front cap. This worked ok... but I had to take care that the pick-up was also positioned tight into the lower rear corner.



I will try a "crocodile" clip... held by sm. locking pliers; to hold the tube in position next time.

Without paint, controls and tank.. weight is just shy of 5 ounces. The plane is quite nose-heavy right now.. but has perfect longitudinal balance... not that it matters too much. It's sitting on the scale with spinner balancing in a small steel bushing.


sorry... can't seem to save correctly rotated pic...   





I need a painting environment... my wife gets terrible migraines from anything solvent-based that's in the air... and "get this"... "She want's to help with painting the model"... and we live in a VERY small house.  My workshop is less than 100 sq. ft. and it's freezing outside. For all the countless hours I have in this plane.. I have to let her paint something... she is an artist though...   

Roddie

Roddie

a finished tank... hopefully. I need to leak-test it.




Roddie