diy surface drive?

[tom kane]

I tried seperate leavers for each side,giving use of both left and right plus both down together.I tried cables to lift each rudder,using prop wash to pull them down.Hydraulic is slow,but geared up ok.I tried air like truck breaking which is better but difficult to tune, but the best option.The trick is to swing the rudders down to use all the prop wash effect.

[tom kane]

A drive using auto parts for 1600 cc. CV cover can be filled with silicon material (breast implant) for mechanical seal as well as CV cover.Water lube brg at prop end,gland seals before CV inside torque tube.Any water leaking past gland can be pumped from inside hull.Trim up down and steer.Motor at back of hull or over drive.Choice of gearbox or belt drive.

[Frosty]

No mention of a thrust block???

A CV (constant velocity joint) can not take thrust. You mention a ford 1600 ---so whats in the box --an outboard.

Sorry --dont understand.

[tom kane]

Impressed with the simple design concept of this old feasibility prototype?
DIY is using your ideas and engineering skills to to upgrade products to your requirements.If you think extra thrust is required and you have the recources and skills to make a good and useful product, and maybe come up with a new and novel and patentable idea the consumers would reward you and make you rich.

[Frosty]

Im sure we are all well aware of that Tom. I just asked why did you mention a 1600 and have some kind of outboard under a box. It looks a though the outboard just does the steering? But I dont understand it. AND you still cant use a cv for thrust.!!!!

[TerryKing]

Originally Posted by Frosty

...snip...some kind of outboard under a box.

After I looked closely at the photo, it seems there's a surface-drive unit with a boot going thru the lower transom, with (possibly) the casting/mount from an outboard HOLDING it. Tom, can you show us more of the whole idea??

[tom kane]

That was the cheap and simple way to try the idea,not cost much.The lower part of an old outboard for exhaust and steering, propstrut and even trim,very basic.
The motor in this case was inboard of the transom all soft rubber mounted using keelson for support and two short beams to take torque on frames.Four bolts on frames to secure unit which could lift out quickly.A motor in and over the transom inside the box was tried (Have photos).

The photo shown shows an early arneson drive which you could diy. There are water intrusion problems here getting into g/box.This would be an expensive development project.

[Frosty]

Ok now I understand but when the engine trims up the support bearing will need to slide down the shaft. There doesnt seem to be accomodation for that.

And what about side thrust( walk). Set ups like this need to be in twins with a mechanical tie bar as does most surface drives.

For a single installation you need something very strong like a levi drive capable of side and up thrust with a separate rudder system.

[tom kane]

The amount of useful trim up and down on such a short shaft is about half the diameter of the prop (10 inches) typical of the problem of short shaft S/P drives giving big prop angles.The usful turning angle is not much more than a rudder,30 degrees.There is room for inovative improvements on these designs.

[tom kane]

A long trimable shaft gives better shaft and prop angles and are easier to instal than fixed drives with fine fixed tolerances.A rudder steered from the back of a trim tab of a flat rudder will give better steering than just a flat plate rudder.Or use dipping rudders.

[TerryKing]

Tom, this is an interesting configuration.

Can you tell us a little more about the geometry used here?

How about the shaft / tube, aft bearing?

Where / how is the thrust handled?

What hull configuration is required?

All I want to know is Everything!

[tom kane]

The thrust can be like that shown relating to SKF adjustable brg in earlier images and posts using two back to back U/Vs with sliding spline,or making a housing like front wheel drive auto to take thrust and trim. .You need a torque tube to support prop shaft using water lube brgs in lower half or use plastic style water lube brg material and fill torque tube with oil (water in there will not make plastic brg material fail).This also acts in place of glands.

The tail frame mounts prop strut and lifts up or down for trim.Aim for 20 degree shaft angle when drive is down as prop does little work lifted out of water more than 50% of prop diameter.

A hull with a flat bottom is where this drive gives advantages and just about any hull can be fitted with this drive.Take advantage of the flexable nature of the U/V`s and make the drive fully rubber mounted.

[TerryKing]

Originally Posted by tom kane

..snip..Aim for 20 degree shaft angle when drive is down as prop does little work lifted out of water more than 50% of prop diameter.

Thanks for the information..

Is 20 degrees what you meant? This seems very high angle??

[tom kane]

20 degree shaft angle down is about what a conventional inboard drive would be,you may not like running your drive in S/P mode so you can fit a conventional prop and run it in subsurface mode.S/P drive has disadvantages and lots of people are disapointed with it.Twin U/V joints are constant velocity joints.

[Grumpyrelick]

I am a newbie here but I couldn't help noticing that much of the scuttlebutt centred around existing drive units. You can build a DIY surface drive from scratch and I did it for under $2000. It was only moderately successful be cause I chose the wrong hull. (Hey it was free!) It is a 13 ft. Glasspar G3 with a 1985 Oldsmobile 3.8 V6 stuffed into it. (a poor choice for a motor but it was cheap) The prop shaft was cog belt driven (1.1:1). with a 6 degree shaft angle. The hull, with an outboard, required a lot of out trim to perform - something you don't get with a surface prop. Best run - about 40 MPH @ 3000. I expected over 60 @ 5000 RPM. I have more pictures of the machinery and can provide more info if required.