Today's work on the little Revell SKIPJACK fittings kit

[toppack]

Originally Posted by redboat219
I see in the 2nd and 4th pictures of your lastest post that you're using the slotted servo horn I querried I plan to use to minimize lateral flexing of the pushrods. Any problems with the movement?

Altho the 2 sloted-arm uses are similar, the forces on the servo arm are very different. With the slide system there should be much less and more steady back pressure on the servo-arm, therefore less binding and jerking, than a push/pull rod going thru a WTC seal will have.

[He Who Shall Not Be Named]

I see in the 2nd and 4th pictures of your lastest post that you're using the slotted servo horn I querried I plan to use to minimize lateral flexing of the pushrods. Any problems with the movement?

Don't you just need 2 servos for the U212. 1 for yaw and the other to slide the first servo for pitch. What's the 3rd servo for?

Yes, the slotted servo horn (bell-crank) takes most of the lateral motion out, problem is you'll need a transverse bearing next to it to maintain linear motion.

Good observation. Yes, only two servos needed for the X-tail linkage. The third servo you see there is for the ballast sub-system.

[redboat219]

Sliding Servo Servo Horn

I see in the 2nd and 4th pictures of your lastest post that you're using the slotted servo horn I querried I plan to use to minimize lateral flexing of the pushrods. Any problems with the movement?

Don't you just need 2 servos for the U212. 1 for yaw and the other to slide the first servo for pitch. What's the 3rd servo for?

[He Who Shall Not Be Named]

Moronic, useless posts to a thread

Hey, guys:

Unless you have something of worth to post, please refrain from those useless, "gee ... nice work", "How's the weather over there", and the always nauseating, "LOL" posts.

Post real comments, corrections, additions, and relevant comments and keep your pinkie off the 'send' button till you've given your words a bit of thought.


PLEASE!!!!

Oh ... and there ARE dumb questions! But don't worry, part of the service here is me telling you when you ask a stupid question. No, no ... don't thank me. It's one of my jobs here (when not sweeping out the Caswell Inc. warehouse and scrubbing their toilets).

David,

[He Who Shall Not Be Named]

You said the servos will be located in the box in the middle of the sub-driver, how do you intend to seal the servo linkages?

There are no pushrod seals. The servo push rods are external of the cylinder, each pushrod is magnetically coupled to a servo output arm.

Damn, I'm good!

The below pictures show different sized 'servo boxes'.

The little SKIPJACK uses the short one, it containing only two servos. The three servo box has the servos arranged so that two of them (one sliding, one moving the sliding servo) are configured to operate an X-tail type set of control surfaces -- for the SubDriver that will drive the little Revell, 1/144 Type-212.

David,

[He Who Shall Not Be Named]

Today's work, part-2

As the stern cone master took shape I periodically joined it with the rest of the hull to make sure things would fit and that there would not be any interference issues between running gear (drive shaft, bearings, couplers, motor output shaft, etc.) and linkages (external rudder and stern plane push rods).

I also went about the task of designing and making masters of the fittings that would hold the SubDriver in registration within the hull. I also cast a little block of resin in the bottom of the hull to form a blank from which I would shape a master for the white-metal keel weight that will be provided with our package.

David,

[He Who Shall Not Be Named]

Today's work

Continuing with work on the masters needed to make the tooling from which I'll produce the Revell SKIPJACK fittings kits needed to convert that static scale kit into a proper r/c submarine:

The assembled propeller master was soaked in Ferric Chloride acid to 'pickle' the metal blades, the acid killed in a weak base solution, dried off and primed. The acid pickling makes the metal blades receptive to holding tightly the primer I would spray over them. Each time the primer was sanded and flaws identified for filling, I again pickled the master to insure a good tooth to mechanically bond either the filler, putty, or primer applied to fill the flaws. The process continued till the propeller master was flawless.

The shot you see here is of the initial touch-up putty application being knocked down with #400 sandpaper -- at this stage I was building up the little fillets between blades and hub. Note the use of a hand-vice to hold the work.

The other shots here show the use of the heat-forming technique to shape polystyrene plastic sheet -- these blanks to be later cut up and used as doublers and indexing strips used to align the two halves of the stern cone master. Not seen are wet rags within the plastic hull. Heat-sinks to keep the heated plastic sheet from melting the hull as heat is transferred between the two.

As long as the plastic is of the thermoforming type (polystyrene, vinyl, acrylic, ABS, PVC, butyrate, acetate, the list goes on ...), it can be formed this way. Don't confuse this technique with vacuforming -- that process involves the controlled application of a differential air pressure to make the heated plastic conform to the shape of a plug or cavity. What you're seeing here is simply, dumb-*%*!*%*!*%*! 'drape' forming.

Once I had formed the blanks over the hull, they were cut up and laid into the stern cone masters and the internal edges filleted with Evercoat filler and Nitro-Stan touch-up putty.

[Kazzer]

I am a God!

David,

HMMM! Oh! Dear! :rolleyes:

[He Who Shall Not Be Named]

im guessing youve got the magnifying glasses on. What you gonna do next Faberge eggs?

LOL.

You know, I've been thinking about just that. Not making them, just thinking of the exacting and wonderful work those hollowed out eggs represented.

David,

[He Who Shall Not Be Named]

David this thing is rediculous. Is that 1/32 brass?

.020" brass wire

[He Who Shall Not Be Named]

How did you shape the prop-blades? Are the blades cut from other props and molded into that hub?
They sure do look balanced, evenly spaced and pitched.
You can tell us your Secrets, we will never be able to duplicate it. :D LOL :D

I employ basic marine propeller perimeters: pitch (a linear measurement, not angular as some idiots keep putting out) is 70-80% propeller diameter; total developed blade area is between 60-70% of the disk, less the hub; and constant pitch (no allowances for fluid velocity variance as a consequence of hull and appendage disturbance).

I'm the expert when it comes to model submarine propulsors.

I make a master of the blade -- its form, helical twist, and area determined by a 'blade chart'; I make a rubber tool of that blade master, cast white-metal intermediate blade masters; assemble those, with the aid of of a propeller assembly jig, onto a Renshape hub; make a production tool of the propeller master; and I'm off to the races, production of cast white metal propellers.

I am a God!

David,

[He Who Shall Not Be Named]

Great linkage design and very KISS. ;)
Will the Props be molded from that 5-bladed master?
Will they be cast epoxy?

Reminded me of my very brief stint as a Jeweler's assistant/under-study (bad job, I did not play well with the other drones).

The propellers will be cast from white-metal.

David,

[He Who Shall Not Be Named]

Assembled the propeller master, as well as the stern cone (a re-build of the kit parts). Tomorrow I should have the tooling in hand so I can build the first alpha-test units. Then, some pool time to check things out and we go to market with the little 1.25 SubDriver and little SKIPJACK fittings kit.

David,