Electric Torpedo using a capacitor

[salmon]

I will download the 3D .stl files once I know how to link it here. Since the article in the SCR came out today, I thought I would follow up with more details and things I found out. If nothing else I can make a dropbox available, but would prefer a solution that is more timeless.

The body is really the most difficult part of this assembly. The electronics is pretty simple.

Next posting I will take more photos and step you through the build.

[crueby]

It wasn't clear from the article, or at least I missed that part, but how far would yours travel on one go? Looking forward to seeing the rest!

[sam reichart]

awesome stuff Tom! I just breezed through the issue last night, but I want to dig in to your build article.

[salmon]

Check out this youtube:

https://youtu.be/aVRb48L6o0k

To directly answer your questions, I am not sure 25 - 30 feet if I was to guess.
It may help on distance. The biggest detriment to distance is friction on the shaft. The 6mm cordless motor is great and all, but a little resistance and it poops out quickly. So alignment of the shaft is critical. I tried a bearing at the very end of the torpedo and the results were disastrous. I am so looking forward to your input if you build these. I think the knowledge base we have here is great and fun things can come from this.
There are many things I think I was not clear on. Not a writer, I am afraid. So, that is why I am doing this WIP. To answer questions, bring value to being a member, and to generate some ideas on developing this

[salmon]

Torpedo_3D_Files.zip
This should work, if you have a 3D printer download these files and let me know how it turns out for you or if I need to modify something. I will have these on Shapeways too for those that want to just purchase the parts.

[salmon]

Here is a video of how much just a little bit of friction makes.

https://youtu.be/AvLUQq5rMNM

When I epoxied this to seal it, a blob got on the shaft. I cleaned it off and the prop turns freely. However, the epoxy left on the shaft rubs on the opening enough to cause this change. I also saw this kind f reduction in run time if I misaligned the shaft and tried to put a bushing at the end.

[salmon]

The hole for the shaft is opened up a little extra to assure no binding.
I used CA to attach the motor mount to the 6mm careless motor.


A syringe is filled with silicon (this case it is aquarium silicon)


Put motor and mount into tail and using a thick CA adjusted until the shaft is centered the exit hole aft. Once dried. used silicon to seal and cushion the motor.


I soldered the positive lead from the capacitor to the single end of the reed switch. The leg with the jog or bend on the reed switch was the normally closed line it will go to the motor. the other lead will go to your + charging port. The negative lead on the capacitor splits off with one lead going to the motor and another to the - charging port.


Above is the crayon schematic to help.

[bob the builder]

This is seriously good stuff, Tom. Thanks so much for getting it out and open for everyone to play with.

I've been working with Dan Kachur for the last 6 months or so (on and off) to see if I can put a kit together for both 32nd and 48th scales. I'm hoping my kits will be out in the next 60 days or so.

Having this information out there for people to try will definitely help to progress the hobby!

Good stuff!

[scott t]

So Tom are you using a seal on the prop shaft?
Was thinking you could connect the motor shaft and prop shaft with tubing.
Then use a cup seal that rides on surface of tubing for water seal.
Or forget a seal and wash it down with WD-40 after each use.

[salmon]

Bob, Thank you! I am working on a 1/72ish torpedo.

Scott,
No real seal. Tubing that will fit .8 mm (shaft size of motor) I did not find. So, I needed to solder.
Any kind of seal seems to cause a lot of friction. Keep your ideas coming you brilliant cyclist.
Peace,
Tom

[scott t]

I prefer mad genius.

Ok for ease of construction try cutting a strip of aluminum foil then apply lite coat of silicon seal to foil surface.
Then wrap around connection between motor and prop shaft a couple of times. Might be strong enough.
Or just a neat blob of silicon seal to create a connection. (like tubing)

[salmon]

That may work! Certainly worth playing with!
I gave Tim Senecal the title of Mad Scientist, You can be Mad Genius.
Thanks Scott!

[salmon]

a switch in gears, going to try a 1/72-ish torpedo. A torpedo in that scale is ~7.4 mm I can make mine ~7.9mm close enough? I think so.
First I have found 1F capacitor that has a 6mm diameter. If I put two in parallel, that would give me 2F of go-go juice.

[salmon]

K&S has an aluminum tube Part# 1115, it is 5/16 inch in diameter and .014 wall thickness. This is the key, I think to make this work. The thin wall gives the inside diameter of ~7.36 mm. That is just enough for the components! The outside diameter 5/16 is about 7.94 mm. The big question is can the size of the torpedo remain buoyant with the weight of a 6mm motor and 2 1F capacitors? Will let you know soon enough.
Maybe tonight or tomorrow I can quickly assemble one to test. Still not sue were to put charging posts. I would lit it placed on the aft end of the torpedo so I can play with a launcher.

[scott t]

Here is an idea:
Take some foam backer rod of correct size. Maybe from Home Depot.

Line up Caps, foam, switch, and motor into torpedo shape and cigarette roll in aluminum tape.


Or take Sam to Wendys for a Frosty and save the large straws for....