Uritski (Russian Orfey Class Destroyer)

I had thought about a few different issues with the the esc being a possibility. I thought maybe it had gotten a drop of water in it, so I tried again the next day to make sure it was dry. Same result. Pretty much as soon as it hits the water it starts cutting out , but not completely. It still tries to rotate, but acts like one of the wires is disconnected. It never really goes completely dead like the esc overheated though. I *think* the motor has enough torque to do the job...... if I keep the motor out of the water and only put the intake under it pumps like crazy. The esc *should* be adequate , its only a 12 amp, but the motor is only supposed to draw less than 5 amps. I was able to run it submerged for about 15 seconds the first time I tried it. It pumped so hard that it blasted water all over my kitchen ceiling, turned the 2 cup measuring cup into a vortex in a short time period. It sure acts like an electrical short. I wasn't aware that there was much in there to short out. I have a couple more of the motors on the way. It is an outrunner, but it shouldn't make a difference. It is a super small motor, maybe its not up to the task. Judging from the initial run it seemed like it was.

 

Its this one, which does not list a Max amp:
www.hobbyking.com/hobbyking/store/_...100kv.html

So I figured the Max amp from this one would be similar:
www.hobbyking.com/hobbyking/store/_...2900kv.htm

This is the esc:
www.hobbyking.com/hobbyking/store/_...oller.html

 

Here are the pics of the pump,
First one is pump v1, shown assembled sans motor, with the impeller and outlet nipple shown next to it. Impeller diameter is just over 5/8" (.650 to be exact). Outlet is 3/16 O.D. Remember, size and weight were paramount here, not pumping capacity.

Disassembled view of pump v1. I decided I didn't care for the thin wall thickness next to the 1-72 machine screw holes, and the fact that the screw heads hung out a hair when assembled so I added some material for v2.

Here is v2 with the extra material added. By the time I made this one the motor had finally arrived so I incorporated a hole for the motor mounting boss to press into. I decided this version was too heavy (or maybe just that it could be made lighter), so I redesigned again.

V2 fully assembled and on scale. I gotta say I'm lovin my $4 ebay scale that weighs in hundredths of a gram!

Even with the quarter there for size reference it's hard to grasp how small this is until you hold it in your hand!

Here is v3 on the scale. Most all unnecessary material has been removed. Even with the boss for motor mounting and the extra material around the holes it's lighter than v1.


V4 is on the way. After programming about half of v3 I realized that if I moved the to outermost holes that it would reduce the over all length of the pump by 20%, but since I was already there and so far along I went ahead and finished v3 even though I knew there would be another redesign.

 

LOL! Funny you should ask! When I took the pics if the pump I also took finals of R2D2 also, just didn't have time to post them. I'll try to do it tonight.

 

Thanks Tugboat! No need to bow however, it should probably be me doing the bowing! I must say that a lot of my ideas and inspiration come from reading your builds and posts so now its my turn

*Bows low and recites "we're not worthy"*

 

That stuttering issue could be a timing thing, especially with outrunners. If the timing is set to high (or above somewhere around 15 degrees or higher) then motors can start stuttering. If the ESC has the option, set the timing to 5 degrees or less and see if the problem isn't fixed.

 

Thanks Richelieu. I can set timing anywhere between 0-30 degrees with a firmware flash. It is currently at 18 deg. I will try to reduce it and see if it clears up the remainder of my issue. I disassembled the motor and looked at the windings under 60x magnification. I found no less than 6 places where the windings were drawn so tightly around a sharp corner of a portion of the stator that it had peeled back the coating. I moved them away as much as possible and after a few attempts back and fourth from the magnifier to the sink I have it to a point where I can get it to about 50-60% throttle before it cuts out. Before it would only get to maybe 10% before the sputtering started. Maybe the timing will get it the rest of the way there, since at this point I'm reasonably confident that nothing is shorting anymore. I wonder if I need to coat the bare areas of the wire?

 

Here is the final version of the pump, v4. It is now 1" long by 3/4" wide, and as you can see, 3 grams. If I can get the current motor to work the fully assembled pump will be around 13 grams

 

That's very cool! Questions:

Why the aluminium impeller? Is plastic not strong enough?
Is your mill CNC or manual?
Do you have any priming issues once you attach an output pipe to the pump?

I'm looking forward to hearing whether you can get that motor working with the added drag from the water (I think that is probably the issue -- I notice that my broadly similar but bigger pump slows down a lot once the motor submerges)

Thanks,
Tom

 

Here they are in all their glory. Invaders v1, v2 & v3. But what the heck are they??

The short answer is a failure!
It was supposed to be a servo actuated, twin 3 way air valve to be used to fire Uritskis torpedos:

Air is routed in through the single inlet on one side, and depending on the orientation of the servo, diverted to one of the other two ports on the opposite side, or if centered, vent the pilot valve to atmosphere. This was supposed to allow me to fire to either side in a small, light, cheap package.

Bottom view showing the plate that holds the servo captive between itself and the body (or Invader )

Another bottom view:

Disassembled showing the internal servo driven rotor:

Way close up of the rotor. Air goes in through top, out through hole with O-Ring in an oval shape around it. There are two such holes. You can also see one of two grooves on the left side that vents the pilot when the servo returned to center.

Rotor mounted to the first servo I tried, which wans't even close to strong enough to return to center fully so servo could "rest" with no load. Caused the servo to get hot. That's why the later versions, I tried a larger servo.

The experiment ultimately failed due to air leakage. This was caused by me moving the O-Ring compression well below the lower limits in an attempt to reduce the torque required to turn the rotor. I even made the last version out of teflon. Mechanically, under low pressure it worked perfectly, but once the pressure was raised it began to blow by the orings.

 

On a side note, how does a guy properly attach a servo to a homemade part to insure it doesn't slip in the mounting hole?? You make your own broach to put the splines in the hole! One of the more interesting things I've made lately.

 

@ Tom
I initially was going to make the impeller from plastic, however after some thought I decided to go with aluminum for a couple reasons. 1) as small as it is and with all that material milled out the weight is virtually a non issue. It is so light you can barely tell you have it in your hand
2) I thought I may want to add a set screw to hold it on the shaft and aluminum would be far less likely to strip the threads. Its so small that you are looking at a set screw smaller than 4-40 (probably 2-56 is what I'd go with).

I "borrow time" from a former employer on a cnc lathe with live tooling capability, which allows milling, face drilling off center, and cross drilling.

So far in the limited testing I've done I have experienced instantaneous priming. Its been a total non issue as long as the pump is at least 1/8 inch deep in water and not sitting flat on the bottom. Even with the uni directional impeller, its still pumps well even info I reverse the motor direction, although output is reduced by somewhere around half.

Drag really doesn't *seem* to be an issue.... this little motor is a bull moose. It definitely slows when loaded, and since its an outrunner there is additional drag when submerged as well, but with what I did earlier that I posted, it will now run up to 50 to 60 percent throttle submerged before the jerking and sputtering start.

 

A few more pic of the progress:

I cut the edges from the decks and glued them on to create a inset deck, hopefully it will help reduce water penetration.


The glued edge is pretty thin, I will need to figure out a material to laminate to it to improve sustainability under fire.
Oh, and that's a great price on pork loin!


A shot of the forward deck, I used a drafting divider to mark a line parallel to the edges to help locate where to drill holes for rare earth magnets:


Some of the magnets in place:


All Magnets ca glued in:


There is one magnet mounted in the deck in each location and a mating one in the cap rail. The decks snap down tight and hold on like pitbulls. If you pay attention to the direction you cut your decks out of the plywood, the decks will form to the hull better. Most plywood is more flexible in one direction than the other, so orient the decks so they are more flexible with the length, not the width. It makes it easier for your mounting hardware to create a better seal since it isnt fighting a slight warp of wood that is most rigid along the long length of the decks. The decks on Emile Bertin are 1/8" ply, but are quite flexible so the magnets on her comform the plywood to the hull perfectly. Not quite a watertight seal, but coupled with the inset decks should do a reasonable job of keeping water out. If not I will have to make an rtv gasket.


As she sits now in real time the hull is near completion, but it's been too cold to get to the garage to seal it with epoxy and add some carbon fiber for stiffness. Hopefully soon, then I can sheet her and start assembly. I need to start finalizing design on the torpedos so they can be tested and mounts made before I sheet so it's easier to access everything.

 

Just a shot showing the current weight. I think I'm close to where I want to be when I pile all the stuff on, but I think I'll wind up a little heavier than I was hoping.

 

Still plugging along on this. Almost done with the rib reinforcement and sealing of the wood. I recently threw everything I have on the scale and unfortunately will probably exceed my target weight by a bit due mostly to adding (if it works) another feature. I only have another 1/4 pound available, and several more items to get in there as well as a superstructure. I am also running out of real estate inside the hull at an alarming rate. This is going to come down to the wire, and I still have several unknowns. I have no clue what the torpedo barrels/ loading tubes and ammo will weigh. I still have to complete the mystery feature and find out if its too heavy or not. The battery will probably not have enough ummmph to power it thru a sortie so I will need a bigger one or an additional one. I still need a recovery device too..... ugggh!

 

Well, Here it is.... R2D2s Cousin. Version 2 of my dual 3 way firing valve in "exploded view". I stuck the pen cap there for a size reference.


Another View.


Here it is next to a fully assembled functional unit. It can fire either side of the torpedo from a single unit. There is a separate piston for each side of the torpedo. In it's neutral state, the spring returns the piston and the ball valve cylinder is vented to atmosphere (so the ball valve will close). The inlet on the top supplies air to both pistons. When the servo is rotated, one of the pistons is compressed which uncovers the port to supply air to the proper cylinder to open the ball valve.


A close up. After the miserable failure of the first version, I'm quite happy with the operation of this one. Seems to work good. Only complaints are it's a little slower than I want, and a little too heavy as well. It also eats up considerably more space than I wanted.


Servo is mounted directly to the valve via an aluminum plate:


Side view. I had to make my own nipples, I couldn't find any with a small enough thread. I wound up going with a 5-44 thread, and then cut the threads on the same taper as a pipe fitting so it is self sealing in the plastic. I did use o-rings as well for an added measure of insurance against leaking:


Here is it's weight, fully dressed, ready for battle. I hoped to keep it far lighter (like version 1), but it wasn't in the cards. I could still shave about 5 grams off, but it's still heavier than I planned:


By way of comparison, a single MAV-3, With out nipples. I guess I didn't do too bad... Just hoped for better: