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Wood hauling with weak motor

Post in 'The Gear' started by Danno77, Apr 20, 2010.

  1. Danno77

    Danno77 Minister of Fire

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    OK, this is a two-fold question that is relating to a decision I made rather hastily a few days ago.

    Back story:

    I have a dead rider with a 12hp briggs engine in it. it has a few good parts on it, I'll probably sell it for a couple of bucks or pull parts off later....

    I have a crappy push mower with a 3(ish) hp briggs on it. the pull cord and cover are long gone, i've been starting it with a power drill for the past two years (not kidding) and it runs well.

    Dad gave a nice self-propelled with a 6.5hp engine (kohler maybe) and the deck and self-propelled system are crappy and need more work than I'd like to put into it. The engine is awesome.

    my plan (too late to completely talk me out of it)

    Take out 12hp engine from rider (done)

    put in 3hp engine into rider (done-ish)

    put 6.5hp engine onto non-self-propelled mower deck (next on list)

    Question #1:
    I bought the smallest pulley I could for the 3hp engine and have it mounted into the rider. I need to get some front wheels on the thing, and tonight I think I'll see if it will even move....DO you think 3hp can move a rider even in 1st gear? I hope so. I figure it will, but it will go slowly

    Question #2:
    I'd like to use it to pull around a little dump garden cart (i took the deck off of it, I'll never use it to mow again). Do you think it can pull anything of weight with that dinky little engine? (i.e. small loads of firewood)


    Basically just looking for ways to entertain myself, thought this could be fun. That 3hp looks hilarious in the rider and the thing weighs so little now that I can just lift up the front with one hand (very hard to lift before with that big 12hp)

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  2. FLINT

    FLINT Feeling the Heat

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    I think it will move,

    its all about gearing
  3. Danno77

    Danno77 Minister of Fire

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    kinda my thinking. I probably won't have all the gears I used to, but I ain't racing the thing, just want it to not be a pile of junk in the back yard anymore......
  4. Flatbedford

    Flatbedford Minister of Fire

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    If you can gear it low enough, it will pull anything,...slowly. Big trucks used to be powered by 6 cylinder gas engines. They moved big stuff slowly. They built the pyramids with machines that were even less than 3 HP.
  5. Black Jaque Janaviac

    Black Jaque Janaviac Feeling the Heat

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    Who was it that said, "Give me a lever and I'll lift the world."?

    As stated, it's all about gearing. That said, you could end up with something that was pathetically slow - as in, "Never mind, I'll just pull the wagon load by hand".

    3 hp can do a lot of work though. I gotta think that it could move a 200lb man plus an equal amount of wood at a reasonalbe clip. You might have to jetison all bells and whistles.

    I'm sure there's ways that you can help it do it's work too. Such as selecting proper wheel and tire size.
  6. FLINT

    FLINT Feeling the Heat

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    ahh, right, good point

    remember, the wheels are the final "gear" in the system - so the smaller the wheels - the lower the gearing.
  7. LLigetfa

    LLigetfa Minister of Fire

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    Ja, even two. I remember my dad got the John Deere LA tractor stuck and we got the neighbor with his team of work horses to pull it out. After pulling a plow all day, they didn't even break a sweat pulling the tractor out.
  8. Flatbedford

    Flatbedford Minister of Fire

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    "Give me a place to stand on, and I will move the Earth" - Archimedes
  9. Black Jaque Janaviac

    Black Jaque Janaviac Feeling the Heat

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    Funny how quotes get butchered.

    I just had my kids plus a few of their friends playing with a block and tackle and a bosun's chair. The little 6-yr olds got a kick out of lifting a 200+lb grown man several feet into the air. The grown man however, realized quickly that once he was high enough in the air to get hurt the kids didn't appear too trustworthy and ordered them to lower him down slooowly. After that the kids took turns lifting each other while the grown man stood close by to supervise.
  10. Flatbedford

    Flatbedford Minister of Fire

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    That was probably a life saving realization. :lol:
  11. Jags

    Jags Moderate Moderator Staff Member

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    On a riding mower - the largest percentage of HP is used to run the mower deck. You might be surprised to find out how little hp is used at the wheels UNLESS you are trying to pull/tow. The rolling friction of a lawn mower chassis is small (lean on it in neutral and it rolls). Keep your rolling friction as low as possible (trailer wheels instead of skies) and I think you will be able to make it go.

    Just be reasonable about your expectations.

    Edit: many-O-moons ago I built a very small go-kart for my nephews. I used a 2.5 hp from an old reel lawn mower. At about 5 mph it would pull my 245 pounds through a mild ditch.
    It was a cool kid cart. I designed it so that the adult set the throttle rpm from the back of the unit and the gas pedal just engaged/disengaged the friction pulley that was used on the engine. It would run for a couple of hours on a pint of gas.
  12. Danno77

    Danno77 Minister of Fire

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    This thing will have a fixed throttle because it's a push mower engine. there are ways around that, but I'm not gonna mess with it. it will be driven by clutch basically. I'll install a kill switch, too, because it will be easier than popping the hood and pulling the plug wire (that's how I used to shut it off, because I zip-tied that stupid safety handle closed so that I could start it with a drill without hanging on the handle) The clutch is a brake, too, you just push beyond clutch release and then you start braking on the axle (IIRC)

    I was out fiddling with it again last night, need to put some gas in and start it before I hook the belt up. I forgot that this thing has 1-3 w/ reverse and then a hi-low, too.

    Anybody know RPM specs on a basic 12hp and 3hp briggs? are we talking a HUGE difference or what?
  13. Jags

    Jags Moderate Moderator Staff Member

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    Typically both will be governed to 3600 rpm at WOT. However if your 3 hp is a set rpm - all bets are off. I have a 6.5 hp push mower with a set rpm and it only turns about 2000 rpm (guessing by ear).
  14. Danno77

    Danno77 Minister of Fire

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    it's governed by a flap that the flywheel blows out. If I want to jump rpms up a tad I can just clip off a teensy bit of the flap (flywheel would need to spin faster to push flap out)
  15. Jags

    Jags Moderate Moderator Staff Member

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    Yeah, those are a very simple governor, but it won't tell you what the set RPM's are. As a side note: if you play with that flap gov, don't cut into it. You can basically do the same thing by bending it, in most cases. Its easier to unbend if need be, than to try and add more tin back to it.
  16. Danno77

    Danno77 Minister of Fire

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    it's plastic, and I'll just tune it by ear. I'll leave it alone unless I get bored or if it doesn't run the tractor like I want.
  17. Jags

    Jags Moderate Moderator Staff Member

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    Figures. :lol:
  18. Danno77

    Danno77 Minister of Fire

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    I just thought I'd dig this old thread up because I actually have the old rider up and going now. Drove it around a little tonight. Even towed the small dump wagon around with a load of oak. It definitely struggles under any significant load. it's very loud and vibrates so bad that my feet tingled for a bit after driving it around. Ran it through all the gears, from 1-low to 3-high and it can handle any of those gears from a stop if I let off the clutch slowly. One of the biggest problems that it will take some getting used to is that the teensy new engine throws the weight of the whole thing off. there is essentially no weight up front now, that makes turning hard and even worse with a trailer behind it. Video will come on this tomorrow, hopefully.
  19. benjamin

    benjamin Minister of Fire

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    Push mower engines rely on the blade to "augment" the flywheel, you might be getting the vibration because there's not as much weight there as there was before.
  20. Flatbedford

    Flatbedford Minister of Fire

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    Can it out pull that green tractor of yours? :)
  21. Mainely Saws

    Mainely Saws Member

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    if that 3hp engine is a vertical shaft , the blade is used as a harmonic balancer & will either vibrate a lot or not run at all without the blade . Larger rider engines have a balanced crankshaft to run smoothly ..........
  22. Danno77

    Danno77 Minister of Fire

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    oh, it runs, just not that smoothly. Part of what makes it seem so loud and rough, though, is that it's running at WOT all the time because it's not a manually throttled engine.

    I went out to take video the other day like I posted I would and when I started it up it wouldn't move. Seems that I didn't bolt the pulley onto the crank shaft and threw the pulley. I know I have another key around here somewhere, but until I find it or spend the few cents at the store for another one I can't drive the thing.

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