3D is great for prototyping new parts

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Carl Van Houten

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I keep way too many projects going around here and like I really have time for another one but I am tired of waiting for a 7.5cc lower unit that comes with a bullet proof prop shaft assembly that is comparable to the one used in the O/S 3.5cc legs. My new prototype unit makes use of current off shelf parts because I really just don't want to get so involved with accessory parts to bring this unit out. It has its obvious design advantages as I have compiled as many perks from other legs as possible. It accepts a standard K&B prop shaft assembly and flex shaft plus my new prop shaft stub (not shown yet). This unit is early into its design phase and will require some actual units made to do testing with. This is just a printed model that only serves as a visual proof of concept but I thought some of you might want to see what it is going to look like when complete.

-Carl

Prototype Lower Unit.jpg
 
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XtremeRcBoats

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Looks great Carl. From the photo it difficult to see it is only a 3d printed prototype.

This will also fit the 67 engines (k&b /nr)?
 

Carl Van Houten

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Hey Paul,

Yes the printed model is cool but not good for much more than making sure everything fits as it should. Having the part made where you can actually hold it and see what you like or dislike about it makes it nice. Mike is hounding me to make a muffler but I really don't think that I am going to get that deep into this. Making the lower unit housing, side plate and and engine mount plate is probably as far as I will go for now. I found out by pulling some serious strings and used up a big favor to find out exactly what material the O/S prop shaft bushing is made from. If I had not been able to get that information I probably would not have even fooled with designing this new lower unit.

Unlike the K&B lower unit there is no need for additional machining work needed to bolt up the Nova Rossi power head. Oh and yes, it will accept the K&B and NR 11cc engines too.
 
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Carl Van Houten

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Thanks Brian. I just finished the side plate model this morning and printed it. I thought that it would be the easy part but at the rear of the plate there is a lot of merging geometry and as it turned out it was actually more to it than I had originally thought. It's done now so when I get the aluminum version in hand I will post a picture of it on here if you guys want to see it.

It should make the SOWEGA race if we have one.
 

LohringMiller

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There's no reason the whole lower unit and mounts can't be 3D printed. The nylons are strong enough if combined with a metal shaft tube, turn fin, and threaded shaft end. I'm considering a .150 shaft version for a P limited outboard. If you really need metal, the printed part can be investment cast.

Lohring Miller
 

Carl Van Houten

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Hey Lohring,

We have mulled over the possibilities and decided that to go with CNC milling the first couple from billet aluminum since I already have the file needed to do most of the contour milling work anyway. Investment casting was the first thing that was discussed. If we like the units we will most likely go to castings but I will also be experimenting with the more exotic filaments that you are referring to. Post pictures of your project when you get time.

-Carl
 

Carl Van Houten

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This lower unit is LONG over due. I am tired of model manufacturing companies dictating what we have or don't have to race with. I have tried to talk to them over the years and you get nowhere with them. This project has been fun so far but there is a lot of tooling expense ahead to bring these to market.
 

LohringMiller

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This is the latest version of a P limited outboard lower. It will run a standard .150 cable with a 3/16 output shaft just like a collet drive system. I'll probably run a wire drive type clamp on the cable for accessibility. There will be a sleeve bearing at the output that runs in a brass tube. The shaft will have clearance in the tube and the thrust will be taken at the output end to prevent binding. A fin will be soldered or brazed to the tube and clamped in the Nylon lower. The mount will also be 3D printed Nylon.

Lohring Miller

3.5 outboard v21.jpg3.5 outboard v21.png
 

Carl Van Houten

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Lohring,

Thanks for sharing your design model. It looks good. When you print it give us a snap shot of it.
 

Paul Renna

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WOW those look GREAT!! We've been working on these

We're machining 3.5 prototypes now. lower.jpg lowerII.jpg
This uses the OS cable and prop shaft and we'll have different motor plates for different motors including FE

The 7.5 is modeled, and 3D printed and ready to start machining prototypes soon
 

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Carl Van Houten

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Nice stuff Paul,

Since I posted the picture of my unit I have increased the length of the skeg to help stabilize the big block engines and their large props.
 
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Grimracer

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Paul,

Looks super.. well done and love to see this happening!

Grim
 

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