Knapp Roller Boat

[Eddy Matthews]

Okay, so rack and pinion certainly does sound like the obvious solution, but the next question is where to obtain suitable rack and pinion that can easily be bent into a circular shape and attached to the outer hull?

I've done a quick search on Google, but haven't found anything really suitable - Does anyone have any ideas?

Regards
Eddy

[amdaylight]

Yup this one is easy, Stock Drive Parts ( https://sdp-si.com/eStore/Direct.asp?GroupID=479 ) They have, stainless steel, brass and nylon.

Andre 
over yonder Portland Oregon

[Tug--Kenny]

As an interesting aside, you could fit a football with an R/C car inside.

When set set loose on the lake it could prove an entertaining distraction. No need for steerage as it could go in any direction

ken

[Eddy Matthews]

As an interesting aside, you could fit a football with an R/C car inside.

When set set loose on the lake it could prove an entertaining distraction. No need for steerage as it could go in any direction

ken

I've called the men in white coats Ken, please let them in when you hear the knock at the door..... 

Eddy

[Dinosaursoupman]

One thing I would think about in using a rack; a straight piece bent into a circle could possibly change the tolerances on the rack. You might think about using an internal gear, perhaps off an RC tank, where the gear teeth are already on the inside of the gear. Since it is designed for that purpose, you wont have the possibility of the teeth binding because of improper clearances.

You may want to think about a pulley and belt drive. I picture the pulley and flywheel assembly that you find in old tape recorders or similar devices. As Oliver suggests, If you were ever to encounter an immovable object, a belt drive may allow enough slip, preventing the interior compartment from spinning around or other damage.

Randy

[Harold H. Duncan]

Hi Eddy,
what you need is epicyclic or planetary gears. If you bend a straight rack around to form a circle it will close up the teeth and not mesh with the pinion.
Some gearbox / gearhead suppliers may sell you just the ring and planet gear as a spare part.
kiwi

[Eddy Matthews]

I agree Randy and Kiwi,

The problem with the gears binding if a rack was bent into a circle is something that crossed my mind earlier today....

I've found a UK supplier for internal gears, but the size I need is damned expensive (around £55).

I cannot see how a belt and pulley system could be used Randy - Care to elaborate? Bearing in mind it's the outer hull that needs to rotate, and the motor would be in the central stationary hull....

Regards
Eddy

[Dinosaursoupman]

I was thinking of attaching the flywheel to the outer hull. The pulley is attached to the face of the flywheel being of a smaller diameter. You won't need to mount the shaft, in fact you could bore out the center of the Pulley/flywheel assembly to allow wiring or mechanical access to either side of the P/F.

If this is still a little vague I could draw up a picture but it may take a while.

Randy

[Eddy Matthews]

If this is still a little vague I could draw up a picture but it may take a while.

Randy

I think a diagram is needed Randy - It's probably me being a bit thick, but I just don't see how it can work...

Regards
Eddy

[Eddy Matthews]

Another problem has reared it's ugly head - As the drive system is in the centre of the hull, that means that the inner hull has to be in two parts with a gap between them to allow for the drive to the outer hull..... With me so far?

So, how do I mount the two inner hull sections within the outer hull, so that it is free to rotate but also stop end float (side to side movement) of the inner hull causing massive drag/friction?

This gets more and more complicated the more I think about it!! Maybe it's me just looking for problems that don't exist?

The design in the patent drawing seems to overcome all (well most) of these problems as the drive is carried down a central shaft and transmitted to the outer hull at the end - So perhaps the patent vessel is the one to build, even though it was never actually built in real life?

Regards
Eddy

[Dinosaursoupman]

how do I mount the two inner hull sections within the outer hull, so that it is free to rotate but also stop end float (side to side movement) of the inner hull causing massive drag/friction ?

A central shaft that is stepped smaller at the ends to fit the I.D. of the end bearings. The outer hull should have a retaining flange to keep the bearing inside the outer hull ends. My thinking is that the end piece or pieces should be made removable (and watertight) to allow access to the inards.

Anyway, here is the diagram as I picture it.

[Dinosaursoupman]

It's taking me longer to download the picture then it did to draw it.

[Harold H. Duncan]

Hi Eddy,
Maybe something like this will help out with your drive issue.
The pivot bearings for the outer I would suggest be at the ends, the inner can then be a plate floor suspended from them. The motor can then be anywhere along the plate, although for access to the belt etc would be better closer to one end.
The ebd plates/frames which have the roller outer bearings should be relatively simple to design as removable, allowing the whole internal "floor to be removed.
Might help,
Kiwi

[Eddy Matthews]

Thanks Randy and Kiwi, interesting solutions to the drive problem. I'll keep them both in mind.

This may well become next winters project. In the meantime, I have a hankering to build another American towboat... Oh, and finish the cigar ship of course!

Regards
Eddy

[Walter Snowdon]

Just athought Eddy. If you need strong planetary gears, what About Sturmy Archer cycle hub gears?  they are very strong, made of metal and are bomb proof. Regards, Walter.