bearing drive shaft

[jtnrumrunner]

I wondering what people think of these bearing drive shafts on ebay (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1755920089). The seller says they spin freely just by giving them a twist, and are used in nitro boats.

I'm somewhat confused as to why the bearing is on the motor side, and bushing on the prop side. I understand the bushing is to help keep out water, but I'm not sure how the washer behind the bushing is held in. This looks like a nice drive for my subsurface hull though. Comments?

[JimClark]

Just do it yourself it will be a lot lighter and work just as well if not better. Check this link http://www.geocities.com/jwohlt5362/Akstraightshaft.html you can also do the shaft with 1/8th stainless steel that you can get from www.smallparts.com

Jim Clark

[Pete B.]

Jim is right, just make them your self. Once you have the materials you can make spare drive shafts to have on hand. For the around 30.00 you can have 3 bearings and enough materials for 3 shafts. You can also make them to your legnth needed. The maintence is easy and all you need is basic hobby tools. In fact I made 2 spare drive shafts yesterday and it only took about 30-45 min. Try it you'll like it!


Pete

[jtnrumrunner]

Thanks Jim and Pete.

You know, I saw this little tid bit a while back on Jim's site, written by Andy K. But I didn't quite understand the language. Now that I sorta do, it sounds very doable. Dont think i'll do the piano string, so thanks for the smallparts.com link Jim. it would be nice to have some really close pictures of the setup like on the ebay site... the ones available are hard to make out.

Andy references a book when he talks about placement of the pivet point (fulcrum), what's this book? On my old setup, the fulcrum was the motor mount. is this typical protocol?

I'm thinking of constructing an adjustable inboard strut so to speak, so the fulcrum can be adjusted. I think I'll make shafts of different lengths so I can control prop depth too. controlling these to factors may prove handy.

where can I get some thrust bearings? and Andy, what journal did you publish the physics derivation for 4/9 magic number for the center bearing ? :)

[AndyKunz]

The "book" is one I've been writing off and on for several years. It's a lot of work and time. It's about 100 pages right now but no pictures yet. The only chapter that's been published is the one of props - there are several others.

No physics publications, sorry!

I challenge you to try another combo and see what happens, though! This would be a good one for Neil to answer - I never did too well with the wave stuff in school.

Andy

[JimClark]

I cant really take pictures of my setup as it is just a fiberglass tube that is the stuffing tube with a flanged bearing on each end and an unflanged bearing inside the tube. I use the small parts Precision ground bar part number U-CGSX-2 which is 1/8th inch and I havent had one that isn't straight yet. It comes in 6,12, 24, and 36 inch lengths.
Jim ClarK
I will see if can get a digital picture of the setup tomorrow I got to get ready for work now.

[Pete B.]

Just don't repair the homade drive shaft! I striped the brass end the other day, so i removed the last 1" or so of the motor end of the shaft and replaced it w/a new sleave of brass. The repair looked good, filed down to the 1/16" steel for the set screws,installed my new SS1,double checked - triple checked and went to the lake Radar gun in hand. The boat was fast and handled like a dream and on a 30 yard straight clocked 28mph on the gun. Then after the second set of 2400's the boat just died. After being pushed in I noticed I had no prop and no bearing in the rear of the tube and no shaft! This can't be I had a collar on the shaft just to prevent this( Per Andy's instructions ). Well the collar was still there, on the sleave that I repaired earlier> Too bad when I repaired this one I made 2 new ones for spares, I just should have thrown out the old one.! Too bad that prop was perfect and I had 2 more sets of 2400's to run. Now I know I need extra bearings too just in case.
One step closer to being ready for anything I guess.

Pete