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3pt Trencher Construction

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activeirrigation
Join Date: Aug 2004
Posts: 4 myrtle beach, sc
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2004-08-28          94815


Hey everyone.

I'm an irrigation contractor and need to be able to trench 2-1/2" wide by 8" deep over long distances (some subdivision entrances can total almost 3/4 of a mile). I'm in Myrtle Beach, SC so I mostly trench in dirt/sand or gumbo clay. (very few rocks but some healthy roots)

I have a craftsman GT5000 garden tractor with a 27 hp engine and extra heavy duty manual transmission. I'm thinking of mounting the Bolton power equipment 3 pt PTO trencher on an Agri-Fab 3 point trailer and towing it behind the tractor. The trailer has a winch to raise and lower the trencher. The trencher requires at lease 21hp at the PTO turning at either 540 or 1000 rpm.

I think that I could mount an engine with some type of clutch mechanism (or hydraulics?) to take the place of a tractor's PTO.
I don't have a lot of knowledge as to engines, transmissions, hydraulics, etc so what I need to know is this:

If an ordinary engine turning at 3600 rpm is rated at 4hp will it achieve 24hp if it's geared down to 600 rpm (standard 6:1 reduction available from most engine manufacturers)It seems to me that it should based on the formula: HP = Torque X (RPM/63025); and

What would be the best way to connect the 3 pt trencher implement to the engine (belts, geared clutch, hydraulics, etc).

I sure would appreciate any help anyone can give me.

Thanks

Gene




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oneace
Join Date: Mar 2004
Posts: 1490 south central pa
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2004-08-28          94846


I think you are opening a can of worms. There are too many factors to consider. My advice: Ditch the craftsman and get a true tractor. The less head ache in trying to make some thing work the better, then that equals more money in your pock in the long run.

....


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BillMullens
Join Date: Jun 2000
Posts: 649 Central West Virginia
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2004-08-28          94848


Gene,

No, the 4 hp engine cannot be made to produce more HP through gearing. What you are doing is increasing the torque at the output shaft; however, it is at 1/6 the rpm, so you'll have 1/6 the rpm and 6 times the torque (less frictional losses), therefore the same HP.
As for driving the implement, I think that a belt, chain, or gear drivetrain (or combination) could be arranged. The hydraulic motors lose quite a bit of power in transmission, I believe, and wouldn't be practical.
All in all I would agree with Oneace.

Good luck,
Bill ....


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Archdean
Join Date: Jul 2004
Posts: 279 Oklahoma
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2004-08-29          94850


I totally agree with Oneace and would even recommend a "Ditch Witch"
Dean ....


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oneace
Join Date: Mar 2004
Posts: 1490 south central pa
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2004-08-29          94851


yes that is one thing I did not think of. You can rent a walk behind unit very cheap. and will be much easier to operate and maneuver. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2004-08-29          94858


A common conversion formula used is t=(5252hp)/rpm, which gives the results in foot-pounds. There are other versions of the formula but the 4hp at 3600 rpm example should result in about 4.8 foot-pounds of torque. Gearing it down by 6:1 would produce about 35 ft. lbs. However, the same hp (not including gearing losses) results due to the lower rpm's. Unfortunately gearing is a torque multiplier but not a hp multiplier or we'd all have unlimited free energy.

I agree with the above comments. However, if really you want to use the Craftsman, a mechanical gear drive for a tractor that doesn't have a power take-off probably isn't realistic but maybe hydraulics. A 21hp belt drive would be quite a thing though. A site at www.precisionfluidpower.com has relevant formula and some ideas. ....


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