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I'm working on a redrive for a k341 Kohler magnum 16hp and a 48" ultraprop.
I'm looking at components at the the 2 web sites below.
Will 2 belts be enough should I just plan on 4?
I'm going to use a 1" shaft.
What size pulleys should I use to get the most from the engine?
I may upgrade the motor to 25hp 0r 30hp after I get next year.
The 16hp will be enough to do what I want to for the time being.
https://www.surpluscenter.com/home.asp
http://www.metalsdepot.com/products/...l/Farm&aident=
Zion,
I'm no expert by any stretch of the imagination, but I think 2 V-belts should be plenty for a 16 HP engine.
Most engines like you're planning to use are designed to peak at about 3600 RPM.
Most props in that size are intended to run at about 2750 RPM max. You really should talk to Ultra Prop to find out for sure.
The following is just an example:
3600 RPM engine
2750 RPM prop
3600/2750 = 1.3
So you may not need a high reduction.
Heck, you may not need a reduction drive at all. Give Ultra Prop a call.
Papee has ran a larger Ultra Prop on his 45 HP 4A084, direct drive, and seems to be happy with it.
The extra work, expense, and complexity may not be worth it in your situation.
Duane
It's just a matter of time before you go with a bigger motor, I'd go with the 4 pulley. You may only need two belts on it for that motor but at least you will have the capability to move up in engine size. For the difference in price it should be an easy decision.
The ultra prop can be run at 3100 RPM maybe just a bit more at 48", it will let you know if you are spinning it too fast. When I had the small pitch blocks in at one point I heard the "bees".
The reason I'm leaning towards a redrive is to lower the center of gravity.
That way I can keep the hull light as possible and stay safe.
I may try it direct drive
Zion,
3600/3100=1.16 Hmmm.... that's almost a direct drive ratio. Considering that a redrive has some inherent loss, I bet it'd work out close to a match, as far as results go.
If it was me, I think I'd try direct drive first. A direct drive would certainly be cheaper, and less work.
Duane
Zion,
My redrive uses a 3vx profile belt. the gut I bought it from said one belt handles 'about' 10 hp. If you think you may be going to a larger motor in the future, it may be useful information....
Flathead
Zion,
What Flathead said is pretty accurate. The Arrow Prop reduction drive uses a "banded cogged wedge" V-Belt. If I remember right, I have a Gates 4/3VX300 belt. That's 4, 30" long, 3VX profile belts, but made together as a single belt. (Does that make sense?)
One of these actually costs very close to the same as 4 individual belts. Depending on where you shop, it may even be cheaper.
By banding them together, they are good for a little more HP, but not a lot. The big advantage of a banded belt, vs individual belts is that they add a little strength to each other, and they can't roll over. :eek:
Why is this kind of belt better than a timing belt? Some say it isn't. I think it is. The pulleys are certainly cheaper. ;thumb; But the real reason, in my mind, is that during hard acceleration or deceleration, they "can" slip a little.
A timing belt can not slip. Not even a little. It's got to either absorb the shock, jump teeth, or break teeth.
I'm only putting this info out there for reference. I really don't think you need a reduction drive. ;beer;
Duane
have you considered a gearbelt? according to my "innernet reconnoiterin" the friction losses with v-belts can be quite high, in the neighborhood of 10-15%, thus pretty much negating any gains you get at relatively low redrive ratios. Browning belts makes a gearbelt they call the panther, supposedly much more resistant to the problems of shock and tooth snap Duane mentions above. I'm considering one myself for my 4A032 engine spinning a helix variable pitch 51" prop set at 6 degrees. I'm running direct drive at a guesstimated 3200RPM at a measured 100lbs thrust, but this is not enough for my gore peanut hull, I'm thinking of going to a 1.5:1 and increasing pitch to 9 degrees or so, and the panther belts claim a loss of only 3-5%. Grainger sells them so they are pretty widely available. might be worth checking out. After all I'm not running an IO-720, so a loss of 2-5 HP can mean the difference between "hey man what'cha runnin!" or "dude, give it up!" Here's a link to the goods:
http://bibliotheque.mecaniqueindustr..._browning_.pdf