old dayton motor's HP rating doesn't make sense, want to resaw with it!

[Brian D Smith]

so i have been on the hunt for larger motor for my bandsaw. I have a chicago electric 2 hp 3450 open motor that i had gotten free with the purchase of some other tools. i know they aren't known to be the best motors in the world but thats one option.

option 2 which is alittle more appealing because i can leave the pulley's at their current sizes is this...

i came across an older dayton 1 hp motor at my families house, it is actually in a homemade 30" bandsaw my grandfather built to build his boat. it's 1725 rpm etc...so it would be a great fit, only issue is i wanted to step up to 1.5hp. so i'm start checking the faceplate out alittle more and see the specs, can someone tell me if i'm reading this wrong or is this motor very underrated at 1hp?!

it draws 14.4 amps at 115 and 7.2 at 230...so figure just slightly higher then that on 240 but we'll use 230 for the calcs...

so if i understand it correctly 1 HP = 746 Watts and Watts = amps x voltage (hopefully you see where i'm going here)

if you work it out the math it is:

Watts = amps x volts
watts = 7.2 x 230
watts = 1656

1HP= 746 watts so...
1656/746 = 2.2HP

the math says this is 2.2 horsepower?! i'm only showing the 230v calcs because it comes out to exactly the same for 115 and i plan to run it on 240 regardless.

the motor has a service factor of 1.25 so it can run at a rate of 1.25HP according to the manufacturer for short periods.

even assuming that the efficiency of this motor is 75%, which i'm sure it's more, that would leave me with right around 1.66HP

so after this long post my question is this...

do you think this motor will keep up with the newer 1.5 motors that are in, for example, the grizzly 14" extreme bandsaw? I have a riser block on my older 14" and i have used the extreme and it resawed very well!

the motor would be free :-)

please let me know your thoughts

btw i took the grizzly 1.5 hp motor and ran the calcs and assuming the same things i did above and a 75% efficiency rate it came out to right around 1.85HP. so there isn't much difference there at all, about 1/5HP between my older dayton and the newer grizzly (assuming my math and calcs are correct).

thanks!

Brian

[Mike Henderson]

Motors are not 100% efficient. Although a HP is about 750 watts, the motor will draw more than 750 watts because of heat losses and mechanical resistance. Depending on the motor, a 1 HP motor could draw 1 KW or more. I have a 2 HP Chinese motor that draws 12 amps at 230 volts, or over 1KW per HP. I would go by the nameplate HP rating of your motor.

BTW, the service factor is the amount you can exceed the rating - so a 1 HP motor with a service factor of 1.25 means that you can get 1.25 HP out of the motor - at the expense of raising the temperature 10 degrees C. And raising the temperature by 10 degrees C reduces the life expectancy by half. There's no free lunch.

But beyond that, why are you concerned about changing the pulleys to slow down the 3450RPM motor you have. I'd definitely go with that 2 HP 3450 RPM motor.

Mike

[Also, when you raise the voltage on a motor, you do not necessarily raise the current through the motor. But the opposite is true. If you reduce the voltage, you will increase the current through the motor. Motors are not resistance elements and do not act the way a pure resistance would work.]

[Craig Hoehn]

If it says 1 HP on the nameplate its probably not going to put out much more than 1 HP. If its using 2.2 HP at max load that just means its an inefficient motor, they also might assume the motor is at the 1.25 rated load when determining the current draw. As per your other question a 1.5 HP motor is stronger than the 1 HP you have, your 1 HP motor can put out 1.25 HP for a short amount of time but doing so regularly will burn out the insulation and fry the motor.

[Brian D Smith]

Thanks for the sanity check guys!

Also Mike,

My pulleys are currently 2.75" motor and 6" on the wheel.

Somewhere in the neighborhood of 3000 sfpm is recommended for 14" band saw according to everything I have read.

With the 3450rpm motor and those pulleys I would be running 5795 sfpm or almost double!

You don't see that as an issue?

I was going to run a 2" motor and either a 7" or 8" wheel pulley to put me at 3150 or 3600 sfpm.

Thoughts?

[Bill Space]

if you work it out the math it is:

Watts = amps x volts
watts = 7.2 x 230
watts = 1656

Brian

For a DC motor this is basically true. However you are dealing with an AC induction motor, and what you have calculated is called the apparent power, not the true power. To calculate true power you have to account for the phase shift between the applied voltage and the current that flows through the motor. This is difficult to measure at home, but likely could be calculated backwards using motor nameplate data.

In in any case, no your calculation above does not represent true power produced by the motor. True power for an induction motor will ALWAYS be less than the calculated apparent power, at least for a simple motor connected directly to the AC power source.

Bottom line is if the motor nameplate states a certain horsepower, do not expect to get much more out of that motor without great risk of letting the smoke out...

Bill

[John McClanahan]

More speed means the saw will cut faster, BUT, there must be a reason most saws run in the 3000 fpm range. I would slow it down closer to 3000 fpm.

John

[Wade Lippman]

14.4a is typically 1.5hp. You have have an extremely efficient motor,or the label could be conservative. Can't tell from here.

[David Kumm]

More speed means the saw will cut faster, BUT, there must be a reason most saws run in the 3000 fpm range. I would slow it down closer to 3000 fpm.

John

Smaller saws run at 3000 fpm because they aren't built or balanced well enough to handle faster speeds. Larger balanced resaws will run 6-8000 fpm. Proper speed really depends on the saw itself. Dave

[Brian D Smith]

the band saw I have is the older grizzly g1019. wheels are true, I just adjusted it all and took it apart and cleaned it...replaced all bearing and put it back together, adding a link belt, upgraded the tension knob to a hand wheel and long acme thread, retrofitted the grizzly "re saw complete fence system", changed out the guide blocks, etc...basically just brought it into this century. the manual stats 3,300 fpm so I figured I would stay close to that.

I just ordered new cast iron pulleys for it. 2" for the motor and 7.45" for the wheel.

3450 * 2 / 7.45 * 14 * 3.1416 / 12 = 3,395 sfpm

that puts me right at 3,400 fpm which is darn close. so I think I'll be happy with that.

good thing I measured the shafts too because I was assuming the wheel shaft was 5/8" just like the motor, turns out the wheel shaft is 3/4", oops haha.

[David Kumm]

I'd swap the link belt for a VX. Link belts are fraction hp and a bandsaw puts a fair amount of stress on a belt, especially if upgrading the motor. Dave

[Brian D Smith]

David,

will do i'll keep that in mind.

[Curt Harms]

the band saw I have is the older grizzly g1019. wheels are true, I just adjusted it all and took it apart and cleaned it...replaced all bearing and put it back together, adding a link belt, upgraded the tension knob to a hand wheel and long acme thread, retrofitted the grizzly "re saw complete fence system", changed out the guide blocks, etc...basically just brought it into this century. the manual stats 3,300 fpm so I figured I would stay close to that.

I just ordered new cast iron pulleys for it. 2" for the motor and 7.45" for the wheel.

3450 * 2 / 7.45 * 14 * 3.1416 / 12 = 3,395 sfpm

that puts me right at 3,400 fpm which is darn close. so I think I'll be happy with that.

good thing I measured the shafts too because I was assuming the wheel shaft was 5/8" just like the motor, turns out the wheel shaft is 3/4", oops haha.

Make sure that shaft really is 3/4". I did similar to what you're doing with a 15" griz bandsaw G1148?. Ordered a 10" diameter 3/4" bore pulley aaand it didn't fit, the bore was a hair too small. The shaft was actually 20 mm as I recall.

[Brian D Smith]

Thanks for the heads up. I actually measured off the pulley itself which still fit snuggly on the shaft. The bore measured .7500" on the calipers. But i checked the shaft to double check and it was .7465" so I should be good.

I have noticed that some of my grizzly equipment is standard and some is metric. Not sure when they made the switch but the g1019 I have is standard and the newer g0555 band saws are metric, I know because when I added the grizzly fence from the G0555 extreme I had to tap the mounting holes for metric screws and bolts.

Brian