Tractor vs. Electric Motor

I have a old grain dryer. The manual for the dryer says it can be run with the pto of a "three plow" tractor. So, I would assume, probably, 35 pto horsepower. What horsepower electric motor would it take to replace the tractor? This is to operate the fan on the dryer. Any help?

(quoted from post at 10:17:55 12/18/09) I have a old grain dryer. The manual for the dryer says it can be run with the pto of a "three plow" tractor. So, I would assume, probably, 35 pto horsepower. What horsepower electric motor would it take to replace the tractor? This is to operate the fan on the dryer. Any help?

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F your 35 number is correct?, then you will likely need an electric motor with somewhat less, but probably still more than 20, so before spending too much effort to track that down, I ask, do you have three phase electric power available. If not, you need look no further, as single phase and 20HP are not a match. If yes, continue your investigation, keeping in mind that some major speed reduction will be needed as well (~1750rpm down to PTO rpm).

Most places don't have light enough soil to allow the use of three plow bottoms behind a 35 hp tractor if you want to put the plow in the ground. You are probably looking at a 45 hp requirement.

The manual for a more recent version of that blower would likely list an electric motor size requirement, but half the tractor hp would probably work.

Maybe if its loose sandy soil and youre not plowing too deep a 35 HP tractor might get you by, but around here in hard wet clay at 8 inches or so deep you better have more like a near 50 HP tractor. As mentioned below if you dont have 3 phase avaialble its gonna be tough to power it with an electric motor set up. All that aside, its hard to estimate without knowing the actual load so I wouldnt run out and buy any tractor, heck regardless what that manual says you know farmers around the world just back up and hook it on to whatever tractor thats handy (Ford 8N, now thats a real stretch if 35 HP is required lol, to a Farmall H or M or John Deere A or B or Allis WD or 45) and it may well do the job....... While I'm more of a John Deere kinda guy I bet an Ollie 88 (or even 77) would sure make that dryer scream woooooooo hooooooooo

John T

i wouldnt, when you add the cost of the electric motor, the re wiring to have enough power to run it, if in fact you dont have to go to a stand alone industrial generator to provide the power, then the cost of electricity it will use, then the gear reducing unit to convert the electric motor rpm to 540 rpm, that money would buy and then pay for gas for a old 45 to 50 hp tractor for a very long time, i say generator because when our company moved a rock crusher then set it up [ it has several 20 hp as well as numerous smaller electric motors on the system,] the local electric co op came out, did some figuring, and refused to let us hook up to the power grid, said if we did the start up sequence would brown out the whole north side of lincoln county nm, not a option lol , turns out the power requirement for the crusher was met by a industrial generater, using a 350 cummins diesel, burns about 5 to 6 something gallons per hour under load

How about comparing the size of the fan with a similar electric driven one? Dryer fans usually have special motors that start "softer"; thus a 36" fan may have what is called a 10/16 HP motor.
Speed will also be a factor. Electric motors are typically 1725 or 3450 RPM compared to 540 RPM PTO.

PTO fans also used tractor 12V DC for controls. Electric will probably use 120 or 240 VAC

As mentioned below, I believe that electric power would be out of the question. First of all, if you dont have 3 phase to run the motor, the cost of getting it would be outrageous. Plus a 3 phase panel etc. You can get a Farmall M for 12-1500 dollars amd just go ahead with no problems. Even if you have to go to 2000 its still less expensive than electric. Henry

To answer your question to the best of my abilitys, WITHOUT getting into a long rant about what you should do, and not to get into the 540 rpm vs. 1735 rpm debate. The local Old order amish use the 2:1 rule when replacing electric power with gas. I.E. when removing a five hp electric motor, you have to replace it with a 10 hp gas engine. hope this helps

How is the dryer currently set up? The manual doesn't show or recommend different drives? My past experience is with an old MC400. The elec. version had the fan(s) mounted directly on the motor(s). The PTO version had a jack shaft and belts to increase 540 by about a factor of three. It was really too much of a load for a 40 hp tractor(the same tractor used to pull 3x14" mounted plows easily). The same 40 hp tractor doesn't have enough power to run my alternator to start my current dryer-(10 hp single phase centr. fan on bin dryer). 60 hp tractor does it nicely. It takes a 70 amp breaker to start the motor.
I know this doesn't answer your question but hopefully you will gather enough info. on here to help.

The math should be figured at 2.5 to 1 and most motors are hooked by belts and to reduce speed you just change pulley size to get 540 out of 1740
Motor you perportion the drive pulley 69% smaller than the driven pulley. If you don’t run the tractor full throttle than you go 75 % smaller. Simple. Also if you don’t have three phases they make up to 16 hp electric motors just for what you want to do and that 16 hp electric motor would be equivalent to a 40 hp gas. Here is a link and ignore the price you local supply store should get it a lot cheaper for you. This motor is designed just for grain drying http://www.baldor.com/products/detail.asp?1=1&page=6&catalogonly=1&catalog=GDL1615T&product=AC+Motors&family=Farm+Duty%7Cvw%5FACMotors%5FFarmDuty&phase=1&winding=39WGW747&rating=40CMB%2DCONT

10HP electrical = 10HP diesel = 10HP gas four stroke = 10HP steam turbine = 10HP hamsters on an exercise wheel.
The confusion starts with a 10HP electric motor being able to handle 25-30HP surge loads that would stall a 10HP diesel dead on the spot.

16HP single phase is the largest I've seen before getting into "shaded pole" single phase.
10HP on the fan would be lots and add a few smaller electric motors to run the augers.

I have been running it with a JD 4030 80 horsepower tractor. It's using 8.8 gallons of diesel to dry and cool a 500 bushel batch of corn 7 points of moisture. The tractor runs about 2 hours and 20 minutes to dry and cool the 500 bushels. The tractor seems to have very little load on it. The fan runs at 2000 rpm at 540 pto rpm. I'm guessing the fan is 24 inches in diameter. (it's at another location right now or I'd go measure it.) My plan was to try to go electric, hoping to eliminate the diesel fuel, and reduce the costs. I'm assuming that elctric would be a bunch cheaper wouldn't it? Thanks to all for the great help so far!

How big of a fan is on the dryer??? If it is a 42" you probobaly need a 15hp. Every grain dryer I have worked on (many) the fan blade is directly attached to the fan motor shaft.

I would bet you can run the dryer on electric cheaper than of a tractor. If your needs for grain drying are worth it, I would look for a used dryer that is more modern.

(quoted from post at 18:41:09 12/18/09) 10HP electrical = 10HP diesel = 10HP gas four stroke = 10HP steam turbine = 10HP hamsters on an exercise wheel.
The confusion starts with a 10HP electric motor being able to handle 25-30HP surge loads that would stall a 10HP diesel dead on the spot.

16HP single phase is the largest I've seen before getting into "shaded pole" single phase.
10HP on the fan would be lots and add a few smaller electric motors to run the augers.

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Yes, HP=HP, by definition, BUT.........you can never install and equal HP gas engine on an air compressor, replacing same HP electric motor and have it pull it. Always has to be greater HP gas. Almost certainly has to do with torque curve. Suspect gas doesn't have enough low end torque to pull up to enough speed to develop torque/HP at run speed. In other words it can't get over the starting hump, but if it could, it might be able to hold up the load.

Yes. I would never go back to drying with a tractor. My electric cost is insignificant. This year about $370. Propane about $6000.

Isn't that what I said?

put the 1000rpm shaft in the 4030 and you can slow down the motor and save even more fuel

May be & just different words?

No B&D,10E doesn't =10G or 10D.On grain dryers or fans,it is min.1E vs 2 Internal or tobe on the safe side 1E to 2.5-3.0 Factor using CFM as the gauge.On the single phase part,there are a lot of farms running 50 to 100HP motor loads at one time.(15&20HP fans.) As to the original poster diesel vs electric,you can run a month on electric vs one day on diesel cost.

Read all what I wrote again.
I said an 10HP electric has an overload capability of 2.3 to 3.0 times it's nameplate capacity.Which will carry surge loads which will stall an 10HP diesel dead.
A fan that requires 10HP to spin at rated rpms will spin at the same rpm with the same shaft torque. No matter the prime mover be gasoline, diesel, two stroke, four stroke, gas turbine. Electric series, compound,series/compound, induction, synchronous or repulsion start/induction run, three phase or single phase.Horses or hampsters
So for surge capacity and engine life a 10HP electric gets replaced with a 15-30HP gas or diesel. Depends if it's a fan or a hammermill subjected to surge loads.
If the fan portion of that dryer draws 10HP shaft HP while driven by the tractor at 1800rpm. Then that fan will operate just fine with a 10HP electric at 1740rpm.
Which brings another factor into the equation, the square root and cube root rule with centrifugal fans etc.
That dryer fan using 10HP to spin at 1800rpm will only use 9.3HP when turned at 1740rpm.
We have all seen at shows a tractor loafing along driving a baker fan. Yet add a little throttle and try to increase the fan rpms 10%. The engine is now labouring flat out and can't make the extra 10% increase in rpms.