1/8" Straight Shaft Plans HERE

[Jeff Wohlt]

Hey guys, anyone interested in straight shaft set ups here is probably the best design.


http://www.geocities.com/jwohlt5362/Akstraightshaft.html

[toyboy4145]

Jeff, that is awesome, thanks. Iwas just about to set mine up, before I saw this.

[Doug Forrester]

Doug
I think the upper wheel collar is to prevent the possibility of the upper flanged ball bearing from working its way free of the shaft log.

[Jeff Wohlt]

And it serves as another safety device in case the coupler lets go. You would not have to use it.

This is known to happen with those Flex Couplers from Graupner...this is the neatest part, I think, because you can make the motor fit better in the hull and have some bend in that coupler. I use one in my 700 Mod SH with a decent bend and it is holding up well.

Also, Andy said he spent lots of time dealing with harmonics and vibes and found that 4/9 from the prop end was key to harmonics and vibes.

[AndyKunz]

I always wondered about this. If the flex coupler is secured to the motor shaft, and the thrust bearing is between the flex and the motor,

No, the thrust bearing is on the driveshaft, not on the motor shaft. You can use the wheel collar that retains the top bearing as the surface which runs against the thrust bearing (when I do this, I leave the top bearing out of the stuffing box).

The flex couplers are known to break when thrusted on.

Andy

[lucashurt]

What sort of difference do you guys think there is between bearing and bushings in this case?

I just don't like the idea of bearings in the water. Seems like a lot of maintenance that for just a fun boat I don't really need.

I was thinking of using the octura style strut bushings or maybe brass or maybe even teflon? If you fill the stuffing tube with oil they should stay pretty well lubricated. I know in very large installations, like on ships, line shaft bearings are really more like self oiling bushings than bearings. I a pretty sure the thrust bearings work the same way with a thin layer of oil between two flat plates.

I wonder if this works in small scale.

Anyone have any idea?

[Allan]

Octura lead teflon bushings need no lubrication so long as the shaft is 'highly polished'. A light oiling prior to running can be used but these bushings are quite at home in water. There are two types - bronze or steel backed.

Allan

[AndyKunz]

Lucas,

I did testing with both.

The bushings are fine with higher-power motors (Plett 30-series) but with 05 cans (the subject at hand I believe) you can't beat bearings.

I use the bearings I do because they work and the price is good.

I pull ALL my stuff apart at the end of a day anyway, whether bushing or bearing, just to dry stuff off. What preventive maintenance do you do?

Andy

[Drobie]

[QUOTE]Originally posted by AndyKunz
Hopefully, this will help answer any questions about executing the details in Andy's article:

http://www.madisonrcboats.org/images/Drive%20shaft.jpg

This photo, courtesy of Andy and Electric Thunder, illustrates the system, to include more detail on the thrust bulkhead and how it is integrated into the hull and motor mount structure to better absorb the thrust.

http://www.madisonrcboats.org/images/Thrust%20bearing%20bulkhead.jpg

Andy, how about your thoughts on constructing the bulkhead from ply rather than aluminum.

[AndyKunz]

GREAT PICTURES, DOUG! Maybe we need to talk.

You missed one component. There's a bulkhead at the thrust bearing which transfers the load from the shaft to the hull.

I have some video from 1991 or so from Electric Thunder. I will dig it out in a few minutes. The video is 1G long, so I'll only pull out what you need!

Andy

[AndyKunz]

Download the video on the other link (it finished uploading a minute ago).

The thrust bearing is mounted in a bulkhead. There's a wheel collar mounted on the back side of the driveshaft that presses against the bearing when thrust is applied to the prop.

I think if you download the video you will have a lightbulb experience. It will make lots of sense then.

Andy

[Pete B.]

Andy, this may seem stupid but what does the drive dog end look like? how do you keep the prop on? Is it with a collar? I read your article on Jeff's site and the saw the video. All of my props are 3/16 id I think. Do you keep building up the OD with brass to get them to fit?

Thanks Pete

[AndyKunz]

I use multiple layers of K&S brass to bush up the prop end to accept a 3/16" prop. It uses a 3/16" drive dog, and the setscrew is on the steel core. Sometimes this means you need to throw away the stock setscrew and replace with a 4-40 bolt, then cut the top of the bolt off when you solder the drive dog in (the prop end is fully soldered together).

To hold the prop on the shaft I use a Carl Goldberg 3/16" wheel collar. The reason for Carl Goldberg brand is that they have a much smaller OD than the others. It is the same OD as the prop's hub.

Andy

[Pete B.]

Thanks Andy, thats what I thought. That should be a big improvment over the stock set up (1157?) from grupner.

Thanks again Pete

[AndyKunz]

Andy, how about your thoughts on constructing the bulkhead from ply rather than aluminum.

The aluminum plate is better. Wood will compress over time and pressure, but the aluminum won't.

It looks like you were one of the brave souls who downloaded the video. What did you think of it otherwise?

Andy