O ya, and seeing as how it's lowww slowww speed, and exposed in bilge.. do not think "Bearings" but rather bronze bushings wherever needed in your setup, and maybe some non ferrous shaft and hardware.
If desirable, one should probably be able to drill out and press in a bronze bush into these wheels.
Basic bronze bushings aka sleeve bearings couple bucks readily available at hardware store in the little Hillman drawers.
Certainly much larger selection like at MMCarr.
Marc
I'm glad I asked- this has been fun. I found this and it is perfect, because it has a key way. Apparently the drive wheels have them. I can even run my line right through the valve hole. It's like it was made for me. Now to order all the bits and pieces. Will let ya know how it comes out.
Attachment 388967
I have seen spoked "mag " wheels for bicycles made of molded plastic. for BMX type bikes. I would use a plastic bushing. Check wheel chair wheels for similar designs.
Do a google search for "Plastic wheelchair wheels"
Insttead of pulley search for "plastic sheave"
Bil l.
Yes, the above is actually one of these wheels. I didn't make that clear. It's a 12" bike wheel by the guys that invented "Tuff Wheels" in the 1970's.Quote:
Originally Posted by Bill Dufour
It is kind of funny how if you call it a wheel, it's $50, but make the same exact thing without the hole for a valve, call it a sheave, and it's $150. ;-)
Don't bother with a second small sheave - just let the line wrap on your shaft.
All you need for this now is a shaft with the right key and 2 pillow block brass bearings.
The cable connected to the board attaches straight to the shaft.
Turn the big wheel and up/down it goes.
I’m kind of thinking that. I am worried now that I will have to pull too much line if I do that. It would make it something like 12 turns to just pull 24” of working end.Quote:
Originally Posted by John C Cox
I guess you have to consider how much mechanical advantage you have vs how hard are you willing to pull....
A 10:1 advantage gives you an 18lb pull to raise the board.... That neglects friction/sticking. But that also gives you the ability to use 30lbs + of pull initially to get it going (or about double to unstick it)... Say you change it to 5:1.. That means the raising force is 36lbs but unsticking may take 50-70lbs on the rope...
You could always try it out and see how it feels. It would be easy enough to clamp a split pulley onto the shaft if you want to increase it's diameter.....
We are woodworkers, make one using wood.
https://www.woodmagazine.com/materia...outdoor-lumber
We are on the same page. There will be a small winch (ratcheting sailboat winch) to add purchase at the other end of this. 5:1 is kind of what I am thinking as a minimum minus the winch. I have two options for the large wheel- 8.5" and 16". They use a 5/8" shaft. I was leaning towards the 16" with 3" smaller pulley for 5.3:1 ratio, but I would have to pull 10 feet of line to get the 24" of line moved at the working end. That's a lot of line to pile up in the cockpit. I could use the 8.5" wheel and 1.5" smaller sheave and get around 5.5:1 and need to pull almost 12'. Ugh. Nothing is ever simple. I also considered a 14" hand wheel that I found, and using a chain to drive the smaller pulley. Advantage: no line in the cockpit. Disadvantage- let go of the wheel and BAM- centerboard free falls. Easier to accidentally let go of a wheel than a line. Also cleating a line is easier than chocking a chain drive and also safer.Quote:
Originally Posted by John C Cox
Keep in mind that although the centerboard weighs 180 pounds, it pivots on a pin which will take some of the weight. There is an extended arm to add mechanical advantage. I'm too tired to do the math, but you are lifting much less than 180 lbs. Another builder of the same design uses a 5:1 purchase and says it easily lifts it.
Attachment 389049
It's on my mind, but if I could get a ready-made part and focus on the build, I would prefer that. If I made a sheave, it would be laminated and have an accent stripe.Quote:
Originally Posted by lowell holmes
Attachment 389068
Look what I just bought. Just need to make a flange which can bolt into those free holes. This is so awesome.