What RPM range would you use?

I have finally figured out how to apply my Minn Kota Trolling motor to my JSP Maltmill.

Per Minn Kota, the motor is rated at 1000rpm at it's highest speed. It'll draw 25 Amps under load. So, basically this means it is a .4 Hp motor with super high torque (value unknown). This motor is a 4 speed motor so, by quartering the RPM I deduce that at speed 1 it runs 250 rpm.

After doing some calculations I have settled on a couple combos.

At a 3.125:1.00 speed reduction ratio I get 80rpm at speed 1 and 317rpm at speed 4.

At 2:1 I get 121rpm over 487rpm.


JSP suggests no higher than 300rpm for the lo0gevity of the mill. Furthermore, a hand cranked crush is estimated at 60 to 100rpm and is the most delicate on the grain husk.

What ratio would you shoot for?

Slow rpm's and a longer crush time per pound (noting that it's automated now).

or

Higher rpm's with a slight sacrifice in crush quality but, gettin' the job done quickly.

I am inclined to go for the slower range favoring a better crush but would like to hear what the community has to say.

I would go for the slower rpm. There are always things to do while the mill is working.
How much grain will you be grinding?

Blender said:

I would go for the slower rpm. There are always things to do while the mill is working.
How much grain will you be grinding?

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Of course it varies but, I generally do 10 Gallon batches in the 1.050 to 1.070 range. So, anywhere from 12 to 25 pounds, more or less.

I am inclined to agree with you tho'. Take the time and protect the grain and realize some benifit of improved efficiency from a good crush.

BrewWare by Karl Lutzen and Mark Stevens states in Appendix A:

"Most people that I've talked to recommend running a mill around 100 to 200 RPM. Faster speeds create more dust, vibration, and so on. Most motors you will encounter are either 1750 or 3450 RPM, gearmotors excepted. If you opt for a standard motor, speed reductions can be achieved using a number of pulley and v-belt combinations. I had originally planned to use a 1750 RPM motor, ...so the the mill was designed to use a 10" pulley to create an effective speed of 175 RPM."

Sheaves and Bushings ordered for the low RPM set-up. I'll source a 4L automotive belt once everything is in place and I can get the proper length.

MotorBoatMill house here we come.

sounds pretty sweet, make sure to post some pics. I too would have opted for the slow speed, its not like your sitting there spinning a crank by hand in order to mill the grain, so who cares how long it takes.

I've said it before, but I'll say it again. Don't waste a working Minnkota on that project. Use a motor guide... Granted, the motor guide will need to be replaced 10 times before your mill shows wear, but damn, save that Minnkota!!!

Anthony_Lopez said:

I've said it before, but I'll say it again. Don't waste a working Minnkota on that project. Use a motor guide... Granted, the motor guide will need to be replaced 10 times before your mill shows wear, but damn, save that Minnkota!!!

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But, I did save the Minn Kota.











For this it appears.

Anthony_Lopez said:

I've said it before, but I'll say it again. Don't waste a working Minnkota on that project. Use a motor guide... Granted, the motor guide will need to be replaced 10 times before your mill shows wear, but damn, save that Minnkota!!!

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I second that in a big way.

For one thing the motor needs water cooling have you considered this?

My Minn Kota Maxxum 50# thrust is a dream machine to use. Only thing wrong I purchased a 83 pound trolling battery that was way too big in amp hour as I can run for three days at 3/4 power with plenty of battery left. Best part it all fits on a built up aluminum hand cart with pole holders, cooler, tackle box, battery, Minn Kota and extended power cord (battery forward in the boat) as a single portable unit. (Best part I cashed in my copper share from work made this a 100% free project. That electronic speed controller sure beats the old heating element resistor type speed controllers of years ago.

I did get a older solid state Minn Kota speed controller free from a service dealer used it on a electric 3/8 scale RC 23 "T" bucket project, added a 1/4 hp 12 volt DC motor. Perfect speed control from 0-100% power. That would be a better motor option for your grain mill.

If it makes you feel any better. It is a MinnKota 35, 17 lb thrust 4 speed assembled in 1989 and hasn't seen the transom of a boat in nearly a decade. For the juice I have a monster StowAway 800CCA.

It was the Minnkota TM or the 79' Monkey Ward 5hp Outboard pull start.

Frankly, I think the latter has too much torque but I do also have a 75cc weed wacker motor too.

GilaMinumBeer said:

If it makes you feel any better. It is a MinnKota 35, 17 lb thrust 4 speed assembled in 1989 and hasn't seen the transom of a boat in nearly a decade. For the juice I have a monster StowAway 800CCA.

It was the Minnkota TM or the 79' Monkey Ward 5hp Outboard pull start.

Frankly, I think the latter has too much torque but I do also have a 75cc weed wacker motor too.

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I WOULD LOVE TO SEE A GRAIN MILL POWERED BY AN OUTBOARD!!!!!

GilaMinumBeer said:

If it makes you feel any better. It is a MinnKota 35, 17 lb thrust 4 speed assembled in 1989 and hasn't seen the transom of a boat in nearly a decade. For the juice I have a monster StowAway 800CCA.

It was the Minnkota TM or the 79' Monkey Ward 5hp Outboard pull start.

Frankly, I think the latter has too much torque but I do also have a 75cc weed wacker motor too.

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Mmmm, two stroke smoked ale!! A possible name, Two Stroke Joke Pale.

Trolling motors are designed to be water cooled, supposedly will burn out pretty quickly if not.... how are you using it?