Conveyor Conversion - Electric to Hydraulic

Andrew Brousseau · Jan 23, 2015

Hi all, So i have a 8ft by 30 in conveyor that I am going to build walls around and use as a hopper. I will be dumping compost into it. Compost weighs about 1000lbs per yard. I'd like to be able to have 4 yards in there, but I could be happy with 2 yards if what I build can't handle the weight of 4 yards. The bearings on the conveyor are all well greased, it was well loved by previous owner.

The clutch case on it appears to have exploded, which is fine because I'm not going to use it or the electric motor. I believe the conveyor was previously used for rock duty.

I understand the need for a centrifugal clutch or other type because there will be so much weight of compost on the conveyor and it will need to be stopped and started when its full. The original electric motor says its 3hp, 230volt, 9.2amp, 3 phase , 1755rpm. I want to replace it with a hydraulic motor. I have one that I do not know the displacement of. I will be powering it off of a mustang 440 skid steer. Using that as the power source I can give it 7gpm and up to 2000psi. The motor I have powered a pair of 2ft long discharge augers for a large mixer wagon (which mixes hay/straw for livestock).
The conveyor is chain drive, I could put a small cog on the chain in order to help the motor power through the weight of the compost on the belt.

Any thoughts are appreciated. See the attached photos to see the conveyor and electric motor I am replacing

oldnslo · Jan 24, 2015

Andrew,
What RPM to you wan to run the conveyor at?
Do you have idea on the gear reduction for the original electric motor?

Depending on the efficiency of the motor you select you probably have around 6 hydraulic HP to work with so you should be able to run this conveyor with a hydraulic motor.

Do you have any numbers on a nameplate on your existing motor? I f yes post them and some one can probably provide the specs on that motor.

Andrew Brousseau · Jan 25, 2015

oldnslo said:
Andrew,
What RPM to you wan to run the conveyor at?
Do you have idea on the gear reduction for the original electric motor?

Depending on the efficiency of the motor you select you probably have around 6 hydraulic HP to work with so you should be able to run this conveyor with a hydraulic motor.

Do you have any numbers on a nameplate on your existing motor? I f yes post them and some one can probably provide the specs on that motor.

Hi oldnslow,
I will get the gear reductions tmrw, pending the amount of storm prep needed. If I knew all the gear, and roller diameters, then I should be able to calculate the belt speed if I knew how fast the hydraulic motor is going. Given my setup, what kind of rpm would a hydraulic motor typically spin? What kind of range will I be able to work with?

So you think a 6 hydraulic hp will be enough to power my conveyor? What if there was 4000lbs of compost ontop of it. I think this conveyor used to be a hopper on a rock crusher.

oldnslo · Jan 26, 2015

Andrew,
It all boils down to torque and RPM required. Generic rule of thumb is that hydraulic drive will be around 70 - 85% as efficient as the electric motor. This efficiency all depends on components selected.

Hydraulics are never as efficient as electric / mechanical drives

Andrew Brousseau · Jan 27, 2015

oldnslo said:
Andrew,
It all boils down to torque and RPM required. Generic rule of thumb is that hydraulic drive will be around 70 - 85% as efficient as the electric motor. This efficiency all depends on components selected.

Hydraulics are never as efficient as electric / mechanical drives

Hi oldnslo, I have done some rough calculating based on this belt's speed of 1 foot per second as the ideal. 1ft/sec however is just a guess of what I might need for this feed hopper. I want to load up to 4 yards of compost in it.

I'm calculating about 200 lbs/ square foot on the belt which has a total area of 17.5 ft. So thats a lot of weight.

Starting from the belt going at 1 ft / 1 second..
Drive rolller on the conveyor does 3 ft of belt drive / 1 rev_roller
Drive roller connects to the large sprocket so 1 rev_roller / 1 rev_LargeSprocket
Large sproket has ~45teeth and connects to a 15tooth sprocket, so 1 rev_Large Sprocket / 3 rev_SmallSprocket
The 15 tooth sprocket will be connected directly to my new drive motor.

So doing all that I calculate that to get 1 ft/sec on the belt, I need 60rpm out of the motor. This seems very low, but I can't see if/why its wrong. So using that motor rpm, and knowing that there will potentially be up to 4000lbs pressing down on this belt, I think a high torque, low rpm motor is what we need.

Additionally I could decrease the size of the 15tooth sprocket a bit to get even better gearing.

Looking at Surplus Center

There are a number of motors. How do I choose a displacement. Displacement is related to the overall hp right? Remember i'm trying to replace a 3hp 240v 3 phase, centrifugal clutched electric motor, and i'd like to do it without using a clutch.

If I pick one with a very high displacement that will give me more hp at an rpm I want, but If I don't actually need all the torque, am I wasting flow correct?

If I pick one with too low of a displacement than I will be maxing out my pressure and I will get a lot of leakage if I can even get it spinning.

Are those assumptions correct?

oldnslo · Jan 28, 2015

Andrew,
Back figuring original electric drive system.
a 3 HP motor at 1750 RPM produces 9 ft/lbs torque

Speed reduction from 1750 to 60 RPM is 29:1 ratio.

29 x 9 = 262 ft lbs torque which is what the hydraulic motor would have to produce.

For 60 RPM a LSHT (Low Speed High Torque) motor would be the best choice.

Hydraulic motor torque is figured using:
T = D x PSI / 24 pi

T = torque ft/lbs
PSI = pressure differential across the motor
d = motor displacement CIR (cubic inch / revoltion)

use torque of 262
PSI of 1500 (allows for line losses in the system Quick Disconnects, valves, etc..)

262 x 24pi / 1500 = 13.2 CIR motor

Required flow in GPM = CIR X RPM / 231
13.2 CIR motor at 60 RPM / 231 = 3.4 GPM @ 100% efficient

At 75% efficient the flow is 4.6 GPM

Some one please check my numbers..

The above is an example to show how to try and figure component size

You can always idle the skid loader down for less flow or adjust conveyor speed.

I do not have a clue whether this would be enough torque to move the load required though.

You have enough flow available to drive a 20 CIR @ 75% efficient. Since torque is an unknown iwowuld probably error on the side of using around an 18 - 20 CIR motor. rather have it run a little slow that not work under load.

hosspuller · Jan 28, 2015

You might consider using the gear reducer from the old drive. It looks like there was a variable speed reducer coupled to the gear. The sprocket is on the output shaft of the gear reducer. Likely simpler to couple the hydraulic motor to the original gear reducer.