New homemade bullet outboard

[Dim L]

A new outboard drive is under construction! This time is a bullet drive with a 4mm flex shaft in order to handle the torque of a 36 mm motor. Again the end piece of the flex shaft will be based on two ball bearings.
The building technique differs from my previous DIY outboard as you see in the photos below.

Chopped CF with epoxy resign to make the hydrodynamic shape of leg and strengthen the construction.

Then sanding, putty and maybe fiberglassing the whole construction for even more strength.
To be continued....

 

[Dirk Jan]

Wow, nice project! I lost count of your ongoing projects, but it doesn't matter, I like this one [emoji6].

How did you mount the fin below the flex shaft? Did you cut a slot in the brass tube?

And I also wonder how you mount the ball bearings and how to prevent they fall out?

I like this way of modeling, using just hand tools. I have some ideas for a DIY outboard as well and the chopped CF is a really nice method!

 

[Dim L]

Thanks Jan!
Having already some experience from the previous outboard, this time things seem to go really fast. This is a 3 day part time work, a couple of hours in the afternoon. So I believe it won't take long to finish this one.

You are right Jan I cut a slot in the brass tube so that the fin anchors in the main body of the leg.

The ball bearings are secured with Loctite. It has worked perfectly in my small outboard.

I realized that the chopped CF or Fiberglass is another way to thicken your epoxy glue or resign. I also used chopped fiberglass to thicken the epoxy glue and the results were great.

 

[Returntohome]

You do like to get messy

 

[Dim L]

You do like to get messy

Hahaha not really ... !!

 

[Dim L]

After some sanding (~ 20 min)
with a 60 sandpaper the leg looks like this:

The mix with the chopped cf (10% of the total weight) and the epoxy resign came out very nice. It is hard, solid and easily sanded.

 

[Tamiya1970]

Looks like it should come out very nice and solid.

 

[Dim L]

Some progress with the outboard.
- I filled the U shaped aluminum with the CF resign mix.

- Final detailed plans.

- I cut the CF parts following the pattern.

The outboard starting to take its shape.

To be continued...

 

[Dirk Jan]

Wow, great work! How do you cut the carbon fiber? By jig saw? And do you wear a mask, or use a vacuum against the dust?

I like your hand sketches, very 'engineering' style [emoji41]

 

[Dim L]

Thanks Jan!
This time I used my dremel with a disk to cut the pattern and then sanding to make the two pieces equal. Every now and then I stop to clean the dust with a vacuum cleaner and of course I wear a mask with filters. Then, I clean the surfaces and tools with alcohol because they are painted black due to the dust. It is not the best thing to work with CF you get messy.

Oh that is a compliment from a real engineer!

 

[Unusual RC]

I like your hand sketches, very 'engineering' style [emoji41]

It is considered more complicated to make a technical drawing or sketch on paper, than it is in 2D or even 3D design software!

My compliments, true engineering!

 

[Dim L]

Oh thank you so much Michael for you nice words!

 

[Dim L]

Well, this was by far the most tricky part of the construction, but I have adopted a number of innovations:
1. The hinge pin is based on two ball bearings for literally zero tolerance.

2. The angle of the hinge pin is unchanged when you change the angle of the outboard. For the advantages of this property and a related discussion you can see: https://www.intlwaters.com/threads/another-lower-unit-option.81251/page-3#post-809409

3. The outboard will go all the way up if it hits something in the water so as to protect the transom.

Some details

To be continued...

 

[Dirk Jan]

Wow, great job! I know the discussion about the hinge pin angle. I'm not sure if it is noticeable for fun boating around, but it is certainly nice that you adopted this.

The assembly looks very professional with al the bolts. Did you glue the bearings in the outboard adapter with Locktite?

 

[Dim L]

Thank you Jan! I agree that some things are just for the joy of construction .

Yes, I secured the ball bearings with Locktite.

 

[Dim L]

The hinge pin system has been re-engineered in a more concise way to reduce the overall length and weight.

You can also see the angle of the flex shaft on the last photo.

Now, regarding motors do you look at watts or amps all other equal? Because there are significant differences between companies.

 

[Dirk Jan]

Looking really good, great work Dim [emoji106]. Regarding motors, I don't look much at Amp draw and Watts. I look at the size and the kV number mostly.
I guess there are 3 classes of quality: medium (Rocket, Xteam, SSS), high (Leopard, TP) and premium(Neu, Hacker).

Amp draw and Watts depend on the motor efficiency and the voltage applied. Also the efficiency of your setup: shaft, prop, hull weight and size etc. Too many factors to take into account.

That's why I look at what is used in high performing hulls (I guess you do that too!). And try to use that as reference.

 

[Dim L]

Thank you Jan for your detailed reply
. You made my choice a little bit easier and I decided to harry up and order this 3670 2280 kv motor at 52 € (including water jacket and shipping) because there were only 4 pieces left

Let's see how it performs and how durable it is.

 

[Dirk Jan]

Great choice for 4S setup! I've seen these Rocket motors on YouTube and they seem to perform really good.

 

[Unusual RC]

It looks similar in construction as my 4092 1250kV motor from Gool/Seal/WTZ! I am very happy with that one!

I think many brands come from the same Chinese factories.
This is quite a bargain you found!