Seaview Motor Shafts Question

[dave_mcwhite@cox.net]

Dear David,

In your 2nd posted article on the Sub-Driver Instructions for the Seaview Model, the fist page (of 40) shows a picture of the two shafts connecting to the Seaview's twin motors. In that picture there appears to be a hollow tube you have inserted the shats into, with a spring attached at the end. No where else is this configuration talked to or discribed. Can you elaborate on it and why you need such a configuration? What is the hollow tube connectedd to, just outside of the picture?

[dave_mcwhite@cox.net]

SEAVIEW SHAFT ALIGNMENT (Proposed Solution)

David Merriman responded privately that he did add the spring and exterior shaft tube to help seat the shaft dog bones into the engine shaft couplers on the Sub-Driver. But he left it up to us to figure out how to mount it!

So I've been experimenting on how to do this. Here is what I've come up with:

Starting with David's shafting concept:
i) Attach plastic tubing between the propeller shaft on the Seaview Kit Pump Jet. about 1 to 1-1/2 inches depending on where you lock in your Sub-Driver tube. (I aligned my Sub Driver Tube to have the fwd edge match the joint where the bow bottom (i.e. w/flying sub bay) is attached, along the keel).
ii) Attach the other end of the plastic tubing to the 3/32 inch solid copper rod (the shaft). You need to experiment with the length of this to match up with the Sub Driver.
iii) Use Shaft Dog Bone to attach to the end of the rod, to mate with the Sub Driver Motor shaft coupling.

So here is what I've changed, based on David's recommendation to add a spring behind the dog bone to help keep the dog bone seated in the Sub Driver Motor Shaft's Coupling:

1) I purchased a couple stainless steel springs from the hardware section of Home Depot that looked a little larger than the 3/32 shaft rod. I had to stretch them to make them more flexible. I then cut the spring into 2 cm sections.
2) I purchased some plastic tubing from my local hobby shop, that was just a little larger in diameter than the 3/32 inch shaft rod. I cut the tube into 1 inch sections.
3) Testers sells glue tube detailing plastic (cone) caps. I took one of these caps and cut off the end, so that the 3/32 inch shaft rod just pushes through the cut cone top. I then open it just a little bit larger to allow the shaft to spin easily.
4) I also purchased from my local RC Store a package of small brass washers (just larger than the 3/32 inch shaft. You will need 2 per shaft.
5) I also purchased from my local hobby shop a package of flat plastic sheets (various thickness).

So here is how I assembled these items.

A) I choose a plastic sheet that was somewhat flexible from the std plastic sheet pack (5 above). I cut a oval shaped strip sized to cover the entire area of the Seaview Model hole that David Merriman advised cutting in the hull to connect to the Seaview's propulsion tubes (Which the pod proposer shaft runs thru). Along the aft end of this oval sheet I cut a 3/32 inch wide line opening, such that the 3/32 inch shaft rod just passes through it. I then cut saw tooth patterns on both sides of this line (about ½ cm deep). Making sure the tooth groves matched up on both sides of the line opening.
B) I attached the shaft tubing, as described by David between the propeller shaft and the 3/32 inch shaft rod.
C) I placed the oval plastic sheet over the Hull Opening, temporarily taping it in place.
D) I pushed the Pod proposer into place and using my fingers or a pair of pliers; I inserted the shaft rod through the oval sheet slot, bending the shaft tube almost 90 degrees from what the proper shaft line should be. I found the saw tooth groves in the slot help keep the shaft in place, while you are working.
E) I then slide the plastic cone cap (3 above) down the shaft rod with the large end towards the propeller.
F) Then I slipped the small plastic tubing (2 above) down the shaft to the small end of the cone. Note: the length of this tubing can be experimented with to determine which length best keeps the dog bone into the Sub-Driver motor coupler with a little bit of compression in the spring.
G) Then I place one of the small washers down the rod (4 above), followed by one of the stretched springs (1 above), and then one more small washer (4 above). The washers keep the ends of the spring from eating into the soft plastic of either the dog bone fitting or the plastic tube.
H) Finally I press on the Shaft Dog Bone that came with the Seaview Fittings kit.
Once done you can let the shaft tubing spring back to its desired angle. You will find the cone like fitting will sit into the sheet slot tooth slots. You can adjust which slot best fits your alignment with the Sub-Driver (once you place it in the model). You will find that it is possible to choose a slot that will press the cone into the spring, while the system is aligned with the Sub-Driver Motor Fittings. This is your key sheet slot tooth grove. Mark it!

You will notice that the dog bone will press up into the Sub-Driver Motor Fitting tightly. But if you slide the dog bone away from the fitting, both the spring and the shaft tubing will give a slight resistance to this. This is just what you want.

Now you have several options to lock this in, here is what I chose to do.

I cut a new the plastic sheet oval, this time with a slot that matched the length where I cut the desired (Marked) saw tooth cut that matched my system's arrangement, to a point aft that allowed me to operate on assembling my shaft system.

I spent time trimming the saw tooth slot to better match up with the plastic cone’s larger opening. I may enven deside to glue the cone to the sheet, but I will wait until I get the model in the water to see if it is required.

I then used some more strips of the slightly flexible plastic sheets to build a pocket that the oval sheet slipped into. I glued this second sheet to the Seaview’s hull just below the shaft opening. Making sure that there was enough room to slide the (Un-glued) oval slotted sheet into it. I found because of the geometry of the hull form, that the oval sheet stays in place by friction, due to bending the sheet and sliding it into the bottom slotted sheet that I glued to the hull. This was so I could remove or replace it if it needed in the future. If after I water test this unit, I find that the oval sheet moves, I’ll find a more direct method to secure it in place over the hull shaft opening.

Well that is my plan and I’ve tested out one shaft so far. I would like to hear from other Seaview builders, on how they have solved this problem of holding the shaft alignment while keeping the dog bone tight into the Sub-Driver’s Motor coupling. And still not bind up the shaft with too much friction?

I’ll try posting a few pictures of this later!

Also anyone come up with a alignment method to hold all the push rods in place in the stern section of the Seaview model, so that there is a good clean match up with the Sub-Driver’s Kli-Con magnetic fittings. David only posted his views on hoe to assemble the push rods, but never showed how he mounted them back in the stern area.

[He Who Shall Not Be Named]

This is how I did it with sleeved square-sectioned brass tube and a spring wrapped from .020" brass wire:

[mickelsen]

I used pieces of round rod inserted into the dogbone part, the outer tube is the next telescoping size up and then a spring to keep the dogbone seated in the drive piece. I think that there should still be plenty of friction between the rod and the tubing to drive the pump jet.

[He Who Shall Not Be Named]

I used pieces of round rod inserted into the dogbone part, the outer tube is the next telescoping size up and then a spring to keep the dogbone seated in the drive piece. I think that there should still be plenty of friction between the rod and the tubing to drive the pump jet.

What's keeping the tube from rotating about the the rod, the spring?

David,

[mickelsen]

The tube is directly connected to the pump jet with that piece of flexible tubing that acts like a kind of universal joint. The spring has friction contact with the end of the dog leg (to keep it pushed up into the socket on the motor shaft). The rod is almost as long as the piece of brass tubing. I'm counting on there being enough friction between the rod and brass tube to drive the pump jet. The whole thing is sort of like a clutch, and it will slip if something binds or blocks the impeller in the PJ. Like I said, I haven't had it in the water yet so maybe I'm "all wet", but I think it will work. I can now see that you used pieces of telescoping square rod and tubing. Obviously there would be no slippage that way. I didn't think of that. Well, if my way doesn't work, I may be asking for some new dog leg ends so I can redo it right.
What's your opinion, David?
Thanks.

[He Who Shall Not Be Named]

The tube is directly connected to the pump jet with that piece of flexible tubing that acts like a kind of universal joint. The spring has friction contact with the end of the dog leg (to keep it pushed up into the socket on the motor shaft). The rod is almost as long as the piece of brass tubing. I'm counting on there being enough friction between the rod and brass tube to drive the pump jet. The whole thing is sort of like a clutch, and it will slip if something binds or blocks the impeller in the PJ. Like I said, I haven't had it in the water yet so maybe I'm "all wet", but I think it will work. I can now see that you used pieces of telescoping square rod and tubing. Obviously there would be no slippage that way. I didn't think of that. Well, if my way doesn't work, I may be asking for some new dog leg ends so I can redo it right.
What's your opinion, David?
Thanks.

I appreciate your thinking here, and yes, there might be enough friction to maintain a no-slip union between intermediate drive-shaft parts -- but I don't think that will be the case.

If your version of the intermediate drive-shaft does not work out, let me know what you need and I'll blast the stuff off to you right away. A practical slip-clutch has great utility here -- would save you from a burned motor if a PJ gets fouled.

Keep thinking outside the box; successful results from practical experiments like this often result in new, useful knowledge for us all.

David,

[dave_mcwhite@cox.net]

This is how I did it with sleeved square-sectioned brass tube and a spring wrapped from .020" brass wire:

David Merriman,

1) If there is nothing holding the outer tubing fixed (from the pictures you posted), what keeps the spring slightly compressed?
2) From your views it seems that the shaft platic tubing acts just like the spring?
3) From the pictures the plastic tubing looks like it is pushed over the outter tube (with the solid shaft turning inside)? Does this not make the whole shaft assembly rotate (Spring outer shaft tube and inner solid shaft)? I don't see any added benefit from the spring, if there is nothing holding the outer tube, and the spring being slightly compressed.
4) Don't you find the plastic tubing provides a flexible enough component to match up the shaft with the engine dog bone coupler?

I'm putting the finishing touches on my version (that I described earlier), and will take a couple of photos to post soon.

Sincerely,

Dave McWhite

[dave_mcwhite@cox.net]

McWhite's Seaview Shaft Design

Here are three pictures of the shaft design I wrote about above. I've dropped the plastic tube in the link up. Found it wasn't needed. Everything turns smoothly, no binding. I did bend the last curle of the spring (on both ends) up alittle so that it would not slide under the washer opening. Hope this helps. Comments welcome.

[He Who Shall Not Be Named]

Here are three pictures of the shaft design I wrote about above. I've dropped the plastic tube in the link up. Found it wasn't needed. Everything turns smoothly, no binding. I did bend the last curle of the spring (on both ends) up alittle so that it would not slide under the washer opening. Hope this helps. Comments welcome.

Dave,

I must first comment about your work ... the simple fact that you are DOING WORK. Good!

Unlike so many guys who pester me with 1001 questions -- you, you pain-in-the-'bottom' -- when I see a series of shots like those just posted by you, the back-and-forth reveals itself to have been a worthwhile, even rewarding, exercise.

Jungleload and others that have posted here and elsewhere have done nothing but buy stuff, complain about it, and talk, talk, talk, talk ....

So, so many people load these forums down with stupid questions (YES, ******, there are stupid questions!), far flung observations, and idiotic proposals. ****** mouth-breathing, morons who still live with their parents. These jerks waste my precious time and contribute NOTHING to the craft. Rare indeed are those outside of the elite (in this game you can count them on one had -- most of them in Europe!) who contribute new knowledge to the craft.

Dave, you appear to have come up with a viable solution to the motor drive-shaft integration problem. Well done, sir! The final proof of the utility of your intermediate drive-shaft couplers will be if they hold together against the torque load presented by the spinning rotor in water. Stay tuned, sports-fan, I think you'll have to switch over to the square-sectioned brass tube once you get into water trials.

I like your blanking off of the propulsion tubes -- I assume you will be opening up massive intakes on the underside of the bilge keels to insure adequate intake water flow? Tell me more about the rational for the blanking plates and how you're providing intake water to the pump-jets.

Keep it up!

David,

[dave_mcwhite@cox.net]

Providing more water to the pump jet

David,

From the picture I've up-loaded you can see that I openned up only the lower side of the jet tubes. Keeping the origional fake intakes for astetics. I'll paint them black when the model get's it's final painting.

The flexible removable internal cover keeps your goal of finger access to do maintenace, while inforcing a better flow into the pump jets. It should also greatly improve the reverse thrust you complained about. I'm sill experimenting on the best method to hold it in place without gluing it down. The cover should also reduce or eliminate the suction you got when moving full speed ahead while trying to flood your ballast tanks.

After I cut the larger exterior openings I filled the foward internal cavity of the stern tubes with Bondo and model putty, sanding them down smooth with the rest of the tube's internal walls. This too should help in the water flow (less cavitation), and gives a direct backward flow of the water when going in reverse.

I'll admit it took a lot longer to fabricate, and $40 worth of sand paper to make smooth. I found the thick bondo shank as it dried and got hot, causing a portion of the outer tube plastic to pull in (dent inwards). So I had to putty that area twice to get it back smooth again on the exterior.

As I may have told you I have a MS in Naval Architecture and Marine Engineering, as well as a BS in Ocean Engineering. My current occupation is the Ship Systems Design Integration Manager for the Navy's new Stealth Destroyer (the DDG 1000), which has given me the oportunity to work along tow tank models at the David Taylor Model basin. I even produced a stealth aircraft carrier hullform desing that made the cover of Popular Mechanics. My father was a officer on the USS Pargo (Gato Class) during WW II and I have worked on the Sea Wolf and Los Angeles Class submarine designs as a Jr. Engineer at NAVSEA HQ. So I know a little bit about underwater hydrodynamics and how bad cavitation is to propeller performance.

Given the new hydrodynamics of the tubes, I'm not sure the 2 prop design you settled on, is still the best for this intake flow. Would love to barrow your other test props, once I get my version up and running, just to see if there is a difference in the thrust generated.

Thanks again for capturing my attention and all the fun I'm having building this model and learning from the whole team here on the forum.

Sincerely,

Dave McWhite

[He Who Shall Not Be Named]

Good stuff, Dave.

A number of years ago I operated an r/c sub in the MASK tank and shock basin over at DT for a TV special dealing with the Civil War era, ALLIGATOR.

I have three and four-blade rotors for those pump-jets -- give me a buzz when you're ready for them and I'll break out the tools and cast some up for you.

You're not going to get any pressure differentials extreme enough to cavitate, don't sweat it. Your problems will be sucking down air from the surface because of the models high freeboard (the rotors are so close to the surface).

David,

[dave_mcwhite@cox.net]

Seaview Stern Tubes & Propellers

David,

Thanks for the offer. I'll let you know when I'm near testing in the water.

I'm sorry to say I'm falling a little bit behind schedule in completing the kit. Work has me pushing 60 hours/week and I've come down with a mild cold. So the few days I get off I've been sleeping.

Still trying to track down a couple of power switches for the Sub-Driver and Up-Periscope tubes. Got your leads but haven't been able to track down the items.

Sincerely,

Dave McWhite

[He Who Shall Not Be Named]

David,

Thanks for the offer. I'll let you know when I'm near testing in the water.

I'm sorry to say I'm falling a little bit behind schedule in completing the kit. Work has me pushing 60 hours/week and I've come down with a mild cold. So the few days I get off I've been sleeping.

Still trying to track down a couple of power switches for the Sub-Driver and Up-Periscope tubes. Got your leads but haven't been able to track down the items.

Sincerely,

Dave McWhite

One source for you is McMaster-Carr. This switch and watertight boot is from their catalog:

7347K75
Miniature Toggle Switch Spdt, on-on, 6 Amps At 125 VAC
$5.24 Each

70205K2
Switch Seal and Boot Toggle, 1/4"-40 Bushing Size, .50" Height
$4.34 Each

Our SubDriver bulkheads are designed to accept these switches and boots.

David,