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Thread: Arrowprop Reduction drive belt tension

  1. #1
    Senior Geezer buster's Avatar
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    Arrowprop Reduction drive belt tension

    How should the re-drive belt tension be checked. I think I heard the belt should not deflect more than 1/4" when pushed with your thumb. I'm quite sure mine is at least that tight.

    Since my first engine spun a rear main, and had a flat spot on the top, I hesitate to put an excessive amount of pressure on this one. It has worked ok until today, and it still seems about as tight as it was last time I checked it.

    Today I took a buddy and went for a about a one mile run in the Aircat. It went good until I decided to turn around and head back. The wind came up a bit by that time.

    As we were turning the boat came off plane, and would not plane out again. The engine would still turn about 3,300 rpm, but we went all the way back at about 5 mph into a 10 mph wind.

    I don't know what could cause that problem other than belt slippage, but we checked out the belt tension as soon as we got back, and It seemed to be plenty tight.

    Do I just crank up the tension and hope the rear mains holds up, er what

    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  2. #2
    Quote Originally Posted by buster View Post
    How should the re-drive belt tension be checked. I think I heard the belt should not deflect more than 1/4" when pushed with your thumb. I'm quite sure mine is at least that tight.

    Since my first engine spun a rear main, and had a flat spot on the top, I hesitate to put an excessive amount of pressure on this one. It has worked ok until today, and it still seems about as tight as it was last time I checked it.

    Today I took a buddy and went for a about a one mile run in the Aircat. It went good until I decided to turn around and head back. The wind came up a bit by that time.

    As we were turning the boat came off plane, and would not plane out again. The engine would still turn about 3,300 rpm, but we went all the way back at about 5 mph into a 10 mph wind.

    I don't know what could cause that problem other than belt slippage, but we checked out the belt tension as soon as we got back, and It seemed to be plenty tight.

    Do I just crank up the tension and hope the rear mains holds up, er what

    Dave

    Dave,
    I'd crank up the tension as see if the problem goes away. In a stiff breeze the Fatcat is a different boat going into the wind vs. with the wind. And, a little extra weight makes a difference. How many belts are on your redrive? J-bird tells me I need 1 belt for each 10 hp the motor puts out. I, by no means, am an expert on such issues but all things considered, the boat has to run, even if it means over tensioning the belts a bit.

    Bruce

  3. #3
    Senior Geezer buster's Avatar
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    Bruce,

    That redrive has four 3/8" belts, and it was designed for the 4A084 engine so it should be just about right.

    Maybe I can cheat a little and back off the prop pitch a few degrees. It should turn a bit easier that way, I just don't want to spin it faster than 3600 rpm.

    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  4. #4
    Permatex belt dressing? It's a spray on stuff that gives the belts a little more grip. Of course it's not permanent and would need to be re-applied as needed.....

    Bruce

  5. #5
    Senior Geezer buster's Avatar
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    I really don't have much confidence in a spray on belt dressing, but I may pick up a can to keep in the boat, just to get me home again.

    I just happened to think, I went from a stock 4" drive pulley, to a 4-1/2". One would think that would give my unit more gripping surface than stock. Still I have problems.

    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  6. #6
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Buster,

    With the bad experience that you had with the first engine, I can certainly understand the concern you have about belt tension, and crankshaft bearings.

    Part of me wants to say that you started out with an engine that already had "shot" bearings. But we don't know that do we?

    I really don't have any good advice to offer. But I do have something to consider.

    The Arrow Prop reduction drive was intended to be used with a belted cogged wedge v-belt.

    The advice that I have been given (for what it's worth), is that you WANT the belt to be "able" to slip "slightly", during hard acceleration and deceleration. A toothed belt, like a gear belt, (or timing belt, whatever you want to call it) can NOT slip, even slightly, without jumping teeth.

    That could destroy a belt in a very short time.

    We haven't talked much since you changed the lower pulley. Are you still using a belted cogged wedge v-belt?

    Here's the short version of the info that I've gathered.

    4 individual cogged wedge v-belts can transmit more power than 4 normal v-belts. A "belted" cogged wedge v-belt can transmit even more power.

    So, what belt (belts) are you using now that you've changed that lower pulley?

    I'm just thinking out loud now, but if you replaced the belted cogged wedge v-belt with 4 normal v-belts when you made the ratio change, well THAT may be the problem.

    Just trying to help,

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  7. #7
    Senior Geezer buster's Avatar
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    Duane,

    When I changed lower pulleys I had to go to a longer belt than the stock banded belt. I was gonna just use four regular v-belts, but when the guy at Graingers found out what I was using them for, he recommended the heavy duty cogged belts. That is what I ended up getting. I think he reffered to them as high-horsepower belts, if I remember right.

    A toothed belt would not work as designed here since the pulleys have no correspoding teeth, so the cogs are for traction, not a positive (anti-slip) grip.

    One problem with them is, they don't come in the length I wanted so I have very little adjustment left. I'm not sure if the next shorter ones will fit, but I will probably find out soon.

    Also, you are correct about the condition of the bearing on my first engine, but I am quite sure it didn't start out with a flat spot on the top. I don't think the stock flywheel and generator would do that to a rear main.

    I probably did that tightening it too much, to eliminate belt slippage, when that old engine was spraying oil on the belt.

    Dave
    Last edited by buster; 07-29-2010 at 09:23 PM.
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  8. #8
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Buster,

    O.K., as I understand what you're saying, you're using 4 individual cogged wedge v-belts now. Is that right?

    I saw something that claimed that a 4 wide banded cogged wedge V-belt could transmit a good bit more HP than 4 individual cogged wedge v-belts, without significant slippage.

    I'll have to look for that again. In the meantime, here's some good info:

    http://www1.eere.energy.gov/industry..._systemts5.pdf

    http://www.gates.com/brochure.cfm?br...cation_id=3102

    http://www.gates.com/brochure.cfm?br...cation_id=3781

    From what I remember, using a "banded" cogged wedge v-belt increased the HP rating by a LOT, over indivudual cogged wedge v-belts.

    I just got to find it again. I think it was somewhere on Gates website...

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  9. #9
    Administrator Papee's Avatar
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    If it helps you any I have my starter belt pretty tight to keep it from slipping. I have no problems so far. Mine is pretty slow too with two people in going into the wind but I'm in lower water most likely. If you run into that problem again just try to find some low water to run in while running at the wind. I have to run mine full bore with two people in it if the wind is strong. Also have the person move around a bit and see if it helps, If it helps maybe you can relocate some weight to make it work better. If your motor isn't raising in rpms there's a good chance your belt is ok and not slipping. If it were to gain rpm then maybe some slipping.

    I have my boat set to work best with one person in the boat as far as engine angle, if I were to adjust it for two people it would run different with just me in it. You'll have to choose between the two. With these boats we are running right on the edge and every adjustment you make will show a difference. Moving my fuel tank 6" front or back make a big difference when it is full. I have my passenger seat as close as I can get it to me and still have leg room to keep the weight distributed better. One thing you can do is get the two people in your boat and float it and have someone look at How the boat is floating with the two peolpe.
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  10. #10
    Senior Geezer buster's Avatar
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    I thought about moving stuff, or people around, but I'm very limited in that. My battery and gas tank are mounted solid to keep them in place. The passenger in front would have to walk at the outside edge of the boat to move back at all. That in itself sounds bad to me.

    Also, the only place I had very shallow water was near the shore, which was covered with tall weeds (I think they are called rushes). I doubt I could get on plane while mashing down the rushes.

    Anyway, I did get the belts a tiny bit tighter, and backed off the prop pitch about 1-1/2 degrees. I'll see how that goes next week. Thanks for all the input.

    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

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