Weed eater engine conversion

Discussion in 'DIY Marinizing' started by Ward, Jun 2, 2003.

  1. Mark F. CheneyM
    Joined: Oct 2008
    Posts: 12
    Likes: 1, Points: 0, Legacy Rep: 14
    Location: Bountiful Utah

    Mark F. CheneyM Junior Member

    UJ power loss

    All mechanical systems consume power. I think that "V" belts are particularly bad in this regard.

    Short shaft systems use some combination of belt or chain and multiple bearings to get power to the prop. A long shaft system uses a UJ and fewer bearings to get power to the prop. I use an "H" block between the end yokes in order to divide the angle that each UJ must operate under. I think that it is moderately more efficient than a single UJ. However I am sure that it still uses some power. I regard it as the least of multiple evils.

    I am quite sure that a long shaft system is more efficient than a short shaft surface drive system. Surface drive systems do benefit from their gear reduction. I am working on a drive reduction system for my 1.6 HP and 9 & 12 HP models These will all be long shaft systems. They all use a micro grove belt for the reduction system.

    Mark F. Cheney
     
  2. bakewater5
    Joined: Sep 2009
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    Location: SE IOWA

    bakewater5 Junior Member

    Thank you. When i did the thia. I was in debate between the longer shaft(more rotating mass vs u joint and loss of torque. Thank you for your professional opinion.
     
  3. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    ah great the underslung chain drive like my earlier posts...what we would like are some closer up photos.....its not loss in the angle drive thats a big problem but it wearing out ...straight shaft is ok LH prop or chain drive RH prop ..Great Job
     
  4. muddin redneck
    Joined: Jun 2009
    Posts: 95
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    Location: Muscatine, Iowa

    muddin redneck DO IT IN THE MUD!!!

    BW5
    what is the gear reduction that you used one the right motor you built?

    nice job by the way
     
  5. bakewater5
    Joined: Sep 2009
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    Location: SE IOWA

    bakewater5 Junior Member

    Wow. In my first post what I ment was. 90 degrees as viewed from above, And the splasher would be positioned toward the front of the kart. I apologize. I have been sick for a couple days, and guess the cold meds had some effect. Pistonbroke working on getting those picks. Would like to thank all the GREAT MINDS that share there knowledge on here. I've picked up a lot.
     
  6. bakewater5
    Joined: Sep 2009
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    Location: SE IOWA

    bakewater5 Junior Member

    hthttp://www.boatdesign.net/forums/images/attach/jpg.giftp://whttp://www.boatdesign.net/forums/images/attach/jpg.gifww.boatdesign.net/forums/imhttp://www.boatdesign.net/forums/images/attach/jpg.gifhttp:/http://www.boatdesign.net/forums/images/attach/jpg.gif/www.boatdesign.net/forumhttp://www.boatdesign.net/forums/images/attach/jpg.gifs/images/attach/jpg.gifages/attach/jpg.gif


    1 6.5 x 4 prop on my dirrect drive
    2 direct drive


    3 Scavenger prop
    4 diffrent veiw of prop
    5 the prop uses a 1/4 in. round stock about 2 in. long as a key way
    6 back side of copied unit
    7 front side
     

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  7. bakewater5
    Joined: Sep 2009
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    Location: SE IOWA

    bakewater5 Junior Member

    Muddin Redneck, the reduction on mine is a 4:1 the company that manufactures them uses a 3:1 if i remember right. I will check when we get them out of storage. We don't see much difference except in open water the 4:1 scoots a little faster.
     
  8. pistnbroke
    Joined: Jan 2009
    Posts: 1,405
    Likes: 34, Points: 48, Legacy Rep: 404
    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    belt drive ..looks like 2 :1 my chain drive was 2.3:1 the problem is the lower cog gets very big if you go for a high ratio...seem to be a lot of shielding on the prop ??
     
  9. bakewater5
    Joined: Sep 2009
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    Location: SE IOWA

    bakewater5 Junior Member

    2inch top, and 8 inch bottom pullies. As far as the prop. I purchased it form the outboard manufacturer. I'm not really a fan. Made of mild steel and at a $180 price tag. Funny thing is one of the manufactured units we got is like 6 years old prop is worn about 5/8 inch and it performs with the others.
     
  10. Erich_870
    Joined: Feb 2009
    Posts: 86
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    Location: Juneau, Alaska

    Erich_870 Junior Member

    That's scavengers design. They use an auger style prop, hoop style tiller handle and a skeg that wraps around the shaft tube.

    Erich
     
  11. bakewater5
    Joined: Sep 2009
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    Location: SE IOWA

    bakewater5 Junior Member

    yep. They also use 3 sealed bearing one on the upper end and, two on the lower end. Nothing for center support. The only welding on them is for the transom mount, and prop.
     
  12. Mark F. CheneyM
    Joined: Oct 2008
    Posts: 12
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    Location: Bountiful Utah

    Mark F. CheneyM Junior Member

    reduction for 1.6 HP Robin

    This is my solution to this problem of high RPM and low engine weight.

    The first picture shows the 1.6 HP 8,000rpm Robin motor ( yellow and grey ) attached to a clutch drum and PTO shaft ( black housing ). There is a 1.5" 6 groove micro belt pulley on the PTO shaft. The 6 groove "J" profile microgroove belt is 16" in circumference. The large 4 " black pulley is metal filled glass with an aluminum center.

    The 4 " pulley is attached to the end of the driveshaft with an accompanying bearing and thrust collar shown in the second picture. A traditional driveshaft and driveshaft tube is used to connect this to the prop.

    This reduces the prop RPM to enable the use of a conventional mud motor prop - I'm gueseing around 2,700 rpm with a 6 x 4 prop.

    The target weight for the assembled unit is 18 lbs.
     

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  13. Mark Wo
    Joined: Dec 2007
    Posts: 143
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    Location: Minnesota

    Mark Wo Senior Member

    Looking nice Mark

    Have to let us know when these are available for purchase.

    Have you had a chance to put that Robins in the water driving the prop you have pictured? The one's I've built and the 2nd hand Rickshaw I own work well but the weakness is the cast aluminum prop. Hit something hard and the prop will shatter (personal experience that scared the crap out of me).

    Mark Wollner
     
  14. Mark F. CheneyM
    Joined: Oct 2008
    Posts: 12
    Likes: 1, Points: 0, Legacy Rep: 14
    Location: Bountiful Utah

    Mark F. CheneyM Junior Member

    Prop

    Mark,

    The pictured prop is cast bronze. I am using it because it is inexpensive. I'm really not for sure on either the reduction ratio or the prop size. A finished prop is available to me in stainless when those 2 issues are cast in stone. Look carefully and you can see a traditional shear pin for driving the prop. This has worked well on this prop traditionally. Normal long shaft designs screw the prop on and eliminate the shear pin. Longshaft environments are rougher than out board environments. For manufacturing it is about sixes either way. I am still waiting on the stainless box to put every thing in. It shouldn't be much longer. I picked up the small pieces today to hook every thing together with. I hope to have one soon now. Thank you for your continued interest. Didn't you get my previous E mail with pictures?

    Mark F. Cheney
     

  15. Mark Wo
    Joined: Dec 2007
    Posts: 143
    Likes: 5, Points: 0, Legacy Rep: 56
    Location: Minnesota

    Mark Wo Senior Member

    I did

    I got the email you sent 6/14 and was certain I replied. As with all things these days, I could have just as easily not replied thinking I did. Forgive me.

    As to the Robins engine - I think what your competiton discovered was that the Robins did not offer any improvement over the current Honda GX35 4 stroke motor that is standard today. I know he tried a bigger Honda but had troubles with oiling and motor seizes. I think this was the GX500 but can't recall exactly and this info is no longer viewable to the public.

    Not to get you off track or anything but have you ever considered making a "Pro-Drive" type of mud motor using a small engine? I don't know if there is value in doing so but just wondering. I have a nice drawing of one somewhere if you would like to see it.

    Still anxiously waiting for the first field trial of your mini longtail. Take some videos if you get a chance.

    Mark W
     
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