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 Horsepower vs Gearing, how much speed is possible?

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Thunderdivine
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PostSubject: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeWed Mar 06, 2013 2:01 pm

So a moped is 2hp, it's made to do 50km/h or 30mph

The opposed Twin I'm getting is 20HP what speed can I expect?
What is the limitations?

Sorry if this is asked before.
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xxXMowerdudeXxx
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeWed Mar 06, 2013 2:12 pm

I've seen one do 55 easily with a 6 speed on utube, I'd say with a lot of mods you could probly get it up to 80. They make kits for trannys that you can put different gears in it so it is a one to one ratio going to the axles, and maybe try a tourque converter on it off a snowmobile. You might be able to do faster idk, I don't know if u would want to go that fast lol
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Thunderdivine
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeWed Mar 06, 2013 2:28 pm

Yeah might try a CVT. Also I guess to small wheels will make you go slower so I went for 16x6.50x8
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WellThatsSurprising
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeWed Mar 06, 2013 2:30 pm

Mostly limited by the RPM's. You also have to figure in weight and wind resistance putting strain on the motor.

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CornishMorgan
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeWed Mar 06, 2013 2:40 pm

Remember that you need to take into account friction from having 4 wheel instead of 2 like on a ped. However you will loose friction if you use better wheels. You will have wind resistance and drag acting against you as well. Just bear this in mind, you can't say a 2hp ped will do 30mph so a tractor with 2hp should do 30mph.

I would guess a 20hp on a salt flat with a huge space, you could get about 85-90.
Don't you go trying to break the land speed record for lawn mowers...That record is mine, I want to set to new record at 125mph then 148.7mph. A tad ambitious but possible.
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Thunderdivine
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeWed Mar 06, 2013 2:46 pm

I'm not just saying, that its made for cutting grass, and when we remove that feature we have to get that HP on the wheels...

I'm guessing there's quite a lot in rpm limitations but also they are quite strong which mopeds are not, so we have to gear them properly.
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TheRainbowBoxer
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeWed Mar 06, 2013 2:49 pm

Yes it does take a decent chunk of that horsepower to run the blades. This leftover HP is a big reason why the engine does not seem to mind at all when you gear them up.

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offroadredneck
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeWed Mar 06, 2013 6:38 pm

I have a video on YouTube of me driving my racing mower 63mh with 23/10/10.5 tires, 23HP v twin,
And a 3 speed transaxle. I could go faster but the pulley sizes are as big And small as I can get them
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Thunderdivine
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeWed Mar 06, 2013 6:56 pm

@offroadredneck wrote:
I have a video on YouTube of me driving my racing mower 63mh with 23/10/10.5 tires, 23HP v twin,
And a 3 speed transaxle. I could go faster but the pulley sizes are as big And small as I can get them

Link?
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dangeroustoys56
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeWed Mar 06, 2013 7:17 pm

It depends on alot of factors - tire size, motor displacement, gear ratios in trans, and pulley sizes.

Bigger front pulley and smaller trans pulley change things drastically - but you lose inital power in takeoff ( i ran a 6" front and 3.5" rear pulley on a 6 speed trans with a 14.5HP OHV briggs and stock tires) - my tractor dogged a bit, till it wound up enough - ended up around 20mph top end.

I kept the same pulleys, upped to a 18HP twin and 8" wheels - in 3rd i was netting around 30mph, still had same inital takeoff lag.

A 1:1 ratio might get a better response, but 3" pulley is the smallest pulley to run ( not enough belt wrap on the pulley) .

I did a pulley swap on my 80's agway when i was using it for mudding, used a 4" motor pulley and a 8" trans pulley - i didnt want 'super fast', just something a lil better then geriatric speeds for the 3 speed trans - 1st and 2nd were pretty much stock, 3rd tho was pretty fast. When i changed it back to mowing duty, 3rd was too fast to be mowing with.

Ive seen full blown racing mowers, running 70/90HP out of v twin briggs motors ( highly modified motors) hitting in the neighborhood of anywhere from 70 to 90mph.


30mph on a basic lawntractor is pretty darn fast , specially when its near stock like mine was, when it was nearly out of control most of the time at those speeds , its a lil unnerving , having virtually no steering and no brakes at all.

My inital aim was to build a tractor w/o any motor mods/power adders and just see how fast i could go - i was aiming for at least 50-60mph , which i believe was reachable, IF i had properly modded the chassis/drivetrain to handle those speeds somewhat safely.

I plan on building a couple fast mods in the future , built to handle higher speeds, when time allows.
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Stretch44875
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeThu Mar 07, 2013 9:10 am

We could hit 35mph with a worn out 8hp. May have took a little time, but it got there.

Horsepower isn't a problem for anything over 10hp. I ran a 10hp for a while, it was just as fast as the 14hp, just took a little longer to get up to speed.

We keep ours geared at 45, with 16 to 20hp, they get there pretty quick.
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crafsmankiller
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitimeThu Mar 07, 2013 12:33 pm

the biggest factor is torque. you can have something geared to the moon (lets say, 80MPH) but if it doesnt have enough torque to stay at tha speed, you wont stay that fast for long.
gearing is the perfect combination of torque and speed.
correct me if im wrong on this.
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PostSubject: Re: Horsepower vs Gearing, how much speed is possible?   Horsepower vs Gearing, how much speed is possible? Icon_minitime

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