diy surface drive?

[tom kane]

There is a big range many style and purposes.Look for series Y bearing flange units cast housing square housing grub screw locking self aligning.FYM is 2.15/16.inch.there should be 4 inch shaft and above.
www.skf.com/skf/productcatalogue/jsp/search/

[TerryKing]

Originally Posted by tom kane

There is a big range many style and purposes.Look for series Y bearing flange units cast housing square housing grub screw locking self aligning.FYM is 2.15/16.inch.there should be 4 inch shaft and above.
www.skf.com/skf/productcatalogue/jsp/search/

Tom, are these primarily thrust bearings, like 'flat tapered rollers', or do they have side-load capability too, like a set of two tapered rollers?

In your designs, have you used a shaft collar of some type to present the thrust load to the bearing, or does the shaft have a shoulder?

...just thinking of how I'm going to DIY this stuff in China next year...

I used some SKF flange-type bearings in big rotary mowers I built years ago.. I'll get that catalog.

[tom kane]

SKF "Y" series, FY model.Shows housing with thrust brg fitted and angled.It revolves to any 360 degree position.Brearing slides out through two slots for renewl.Collet fits on shaft with locking grub screw and is designed to lock onto brg and shaft by of set of-centre turnings shown.This will give shaft angles up to 20 degrees and even steering left and right,up and down if so designed.If you want more shaft angle a different design and pivot point is required.Similar to part of the drive in an inboard/outboard.The design shown is probably the simples you can build.

[tom kane]

Image shows how standard conventional twin universal`s with a sliding spline can give 20 degrees of movement and run in any direction.Usually this set up is only used in a fixed position since Adam..10 degrees motor angle,10 degrees taken up by u/v`s.Electric motor is running and maximum angle can be obvious when angle is too great.Support bearings on prop shaft should comply to 20 40 rule.No closer than 20 times shaft diameter,no further apart than 40 times shaft diameter.

[tom kane]

Auto parts for a surface drive? If you want a real heavy drive pinch a front wheel drive unit from a heavy industrial tractor.It would be adjustable up and down and give stearing.

[TerryKing]

Tom, thanks for the practical info and getting it up for us here.. Please keep on with it!

[Frosty]

Originally Posted by tom kane

Auto parts for a surface drive? If you want a real heavy drive pinch a front wheel drive unit from a heavy industrial tractor.It would be adjustable up and down and give stearing.

If they are constant velocity joints they wont take thrust. I know they use CV on marine installations but they go through a thrust block first.

[TerryKing]

Originally Posted by Frosty

If they are constant velocity joints they wont take thrust. I know they use CV on marine installations but they go through a thrust block first.

Frosty, if the wheel spindle is kept in the package, it has tapered roller bearings that take the side-thrust when cornering the vehicle, which can be considerable. So running a boat underway would be like a constant right (or left) turn with that thrust block.

That said, I'd rather just couple the drive axle after the first (inner) CV joint on a front-wheel drive vehicle to a good thrust bearing like the SKF "Y" series, FY model that Tom showed earlier.

With the differential locked up like for off-road vehicles, there would be a 2 or 3 to 1 reduction ratio (depending on overdrive) on an off-the-scrap-lot front wheel drive engine-transaxle assembly. Running the right prop on a displacement craft should be pretty easy.

Running two identical engines/transaxles facing opposite, you'd have counter-rotating prop shafts at low cost. No marine transmission. Negative: Reverse is a poor low ratio. But I ran a modified car transmission on a small inboard years ago and I just revved the engine to 3000 or so and there was enough reverse for anything reasonable...

What I wonder about is how the numbers would come out for two 100 hp @ 2800RPM (derated from 160 hp * 4800RPM) V6 car engines on a 25 to 30 foot planing hull and the 'right' surface-drive props for the 2.5 or so reduction ratio.

The DIY Budget version: Just added raw water pump(s) and heat exchanger, Dry exhaust.

Hmmm...

[Frosty]

A trimable steerable surface drive is a problem . Its easier to make DIY fixed shaft. This will also be more robust and maintenance free.

Arnesons look great and are the biusness for tearing across the bay before taking it out and washing it. If its going to stay in the water you dont want hydraulic rams in there.

[TerryKing]

Originally Posted by Frosty

A trimmable steerable surface drive is a problem .

With twin engines, I'd be inclined to not make a DIY drive steerable, just trimmable. That might be purely mechanical, not adjustable underway, or use a mechanism where the hydraulics/servos were protected inboard.

With rudders and reversible drive the steering and low-speed maneuvering should be OK. Have you seen configurations like that? What do you think?

[Frosty]

Trimable ,steerable,--youve already done the work all you need is an extra ram.

With steerable and trimable youve got the joint to worry about and keeping sea water out. A rubber grommet or boot is all you can do and antifouling will be a nightmare.

The picture attached is a cat that I own to this day and I made these drives 4 years ago. the reversing deflector is on the floor and without them it reverses awfull. The rudders are number 3 and are final.

The boat performs slightly better than manufactures with 100HP less.

[mydauphin]

Frosty, I dont understand reversing plate. Does that go in front or behind prop. Looks like Levi Drive. Did you make semi-circle out of aluminum or steel?

[Frosty]

The "reverse plate" simulates a 45degree transom. As you can see from the picture the transom is flat ,any thrust from the reversing prop hits this and it goes out the the side or bounces off. Without the plates reversing is very poor.

Those on the floor had just been made and replaced some stainless steel ones that were giving me electrolisis problems. They are simply attached and does nothing but deflect thrust in reverse. When on the way they are out of the water.

Those are rudders number 3 and are satisfactory. They were bent in a press. The flare at the top is a steam pipe 6 inch to 3 inch reducer machined down.

It is very difficult to build in strength into tunnel rudders when the rudder shaft does not continue down through the blade.

I personally know sony Levi and talked to him in great lengths before making this system. So I guess similarity may be incidental, however the sony levy drive has a casing on which every thing is fitted to --mine is using the hull of the boat resulting in a lighter and more simple assembly.

[tom kane]

A rudder only when you need it.Dipping rudders,turn left,right rudder drops down into prop wash.Turn right left rudder drops down.No drag of rudders going ahead more speed.Drive is trimmable up and down 20 degrees.A shaped rudder gives more efficient and greater turning.And if you want to stop in a hurry,both rudders down.

[TerryKing]

Originally Posted by tom kane

A rudder only when you need it..snip..

Interesting, Tom! Is this a concept or is someone doing it??

WhatIf LEFT rudder comes down as left turn is wanted, same for right. So (maybe) if just a very small amount of course correction is needed, it's done mostly with the added drag of left rudder, until more side force is needed??

Maybe the rudder shape is such that at very slow speeds it has even more area rotated into the water... Maybe its outer profile is a half a spiral. So the full-down profile is like typical water-ski fins. Hmmm.