Want to add HP to bandsaw. Is this OK?

[Brian Ruhlman]

My 1967 14" floor model Powermatic band saw has a 3/4 HP motor. I have a spare 1/2 HP motor same rpm and rotation. I want to mount it beside existing motor. Pull sheave off existing motor and replace with a two belt sheave same size. Place the original sheave on the small motor join motors together with a belt. I would still run the original motor for light duty stuff knowing it would spin the additional motor. Switch on both motors for resawing. Why would I do this - cheap fix for more power. Are there issues or problems with my plan?

[Jason Beam]

They'll end up fighting each other and you won't see any additional horsepower, I don't think. Sounds good, but the reasons it don't work aren't immediately intuitive. One would normally think that rotational forces are additive, but it turns out that it's more complex than that. I wish I could explain why better, maybe someone smarter than me can?

[Lance Norris]

Brian... you cant increase power output that way. It just doesnt work like that. The only way to increase the power is to replace the motor. Check Grizzly.com for replacement motors. Good luck.

[Cliff Rohrabacher]

No. If the motors were matched you would realize an increase in output but you have mis matched motors and one will most likely become a generator.

That'd be bad.

[Peter Quinn]

I'd stop playing and put in a hemi, something like a 426 out of an old Cuda. Now that will give you resaw power!

[Pete Bradley]

Since the motors are both designed for the same RPM, I expect you'd get some combined effect, but only marginally so. 3/4HP should be fine for that saw though so I wouldn't mess with it. Band selection is generally much more important than horsepower.

Pete

[Lance Norris]

I'd stop playing and put in a hemi, something like a 426 out of an old Cuda. Now that will give you resaw power!

Hey Pete, Ive got a 70 Roadrunner with a 440 6pack. That would probably work also, dont ya think?

[Dave MacArthur]

No. Any RPM difference will cause one motor to drag, reducing it's efficiency, and cause other motor to generate some fraction. There will be some RPM difference.

[Hans Braul]

Hmmmmm......
Seems to me it might just work. Motors do not run at constant speed (i.e they are not "synchronous") but they slip relative to 60 hz, and the amount of slip depends on the load. The more load, the more slip, and the more torque produced by the motor. If you apply load to both motors, they will both slip, each supplying torque accordingly.

Could be wrong, and that would of course use up my yearly quota.http://www.sawmillcreek.org/images/icons/icon12.gif

Cheers

[Jason Beam]

If it worked, we'd have seen it by now, doncha think?

Some redneck engineering would have discovered this long ago, I'll bet.

[Loren Hedahl]

If it worked, we'd have seen it by now, doncha think?

Some redneck engineering would have discovered this long ago, I'll bet.


No one's seen everything yet!

Doesn't mean it has never been done -- Wasn't it Solomon that said, "There's nothing new under the sun."?

Give it a try and report back here. Then the rest of us can say, "We saw it here first!"

My guess is that the two motors in tandem won't add horsepower in a simple addition, but will add as the square root of the sum of the squares.

Simple addition would give 1 1/4 HP. Using the root mean square addition would give 0.90 HP.

This HP would only be realized when each motor was loaded to reach its rated current draw and at its rated RPM. Unloaded they would each run close to synchronous speed, i.e., 3600 RPM. Normally the full load rating is 3450 RPM or a drop of 150 RPM which is known as slip.

Textbook problems sections are full of this kind of scenario. The solutions look fine on paper, but in real life rarely work out exactly as thought, but give a starting point for experimentation.

In your case, I would advertise the motors on Craig's list, take the money and add what it takes to get the motor with a rating you really want.

[Brian Ruhlman]

Well, I think almost everybody is right to some degree.

The band saw is new to me. So Pete Bradley, the saw came with one blade - I will try a different one. I reduced the speed from top to second fastest - much more power, maybe 3/4 HP is enough for a 6 inch cut once I get the right combination. It cut 4 inches but way too slow for splitting long boards. There are various sheaves for speed control setting and a gear box for slow metal cutting. I will play with it.

Fighting each other in some redeck engineering sort of way? Jason Beam, I think what you had in mind was a twang of what Loren Hedahl explained.

I spoke with a technician at work about this question. His experience is really big industrial motors are sometimes joined together i.e. 18+18= 36K HP but the motors are identical right down to the number of winding so no power would be wasted.

I tend to agree with both Hans Braul and Loren discusses. The output would not be a sum. The smaller motor would slip more than the larger motor given equal load and not joined together. I think what they are saying is torque applied equally to motors joined together would have an additive effect but because the slip is different in each motor for the same load, 3/4 plus 1/2 does not equal 1-1/4 but somewhere between 3/4 and 1-1/4 HP.

What I will do: Follow Peter's recommend and get used to my saw first. I will though join the motors together if I then feel I need more power.

Thanks Gentlemen from West Virgina.

I had a really cool Vega with a 283 - would that work Peter Quinn?

[Brian Ruhlman]

Almost everybody is right to some degree.

The band saw is new to me. So Pete Bradley, the saw came with one blade - I will try a different one. I reduced the speed from top to second fastest - much more power, maybe 3/4 HP is enough for a 6 inch cut once I get the right combination. It cut 4 inches but way too slow for splitting long boards. There are various sheaves for speed control setting and a gear box for slow metal cutting. I will play with it.

Fighting each other in some redeck engineering sort of way? Jason Beam, I think what you had in mind was a twang of what Loren Hedahl explained.

I spoke with a technician at work about this question. His experience is really big industrial motors are sometimes joined together i.e. 18+18= 36K HP but the motors are identical right down to the number of winding so no power would be wasted.

I tend to agree with both Hans Braul and Loren discusses. The output would not be a sum. The smaller motor would slip more than the larger motor given equal load and not joined together. I think what they are saying is torque applied equally to motors joined together would have an additive effect but because the slip is different in each motor for the same load, 3/4 plus 1/2 does not equal 1-1/4 but somewhere between 3/4 and 1-1/4 HP.

What I will do: Follow Peter's recommend and get used to my saw first. I will though join the motors together if I then feel I need more power.

Thanks Gentlemen from West Virgina.

I had a really cool Vega with a 283 - would that work Peter Quinn?

[Lance Norris]

Brian... I have a steel frame Grizzly with 2 hp and it cuts anything with ease. I also have a 14" cast iron frame Ridgid with a 3/4 horsepower motor. I have made lots of bandsawn boxes on the Ridgid. I recently added a riser block to the Ridgid, increasing the resaw height to 12". I just cut an 8" thick block of black walnut last night with no problems what so ever, with the Ridgid. The blade was an 1/8" 14 tooth. I didnt go fast, but it took probably 2 minutes to cut out a core that measures 4"x3". I cant see any common domestic hardwood giving the saw any problems. What it wont do, is cut thick, resinous hardwoods like purpleheart or bloodwood, with a fine tooth blade. I like to use a fine tooth blade because it reduces the sanding I have to do. Take your time, make sure the drive belt is tight, use a good, sharp, clean blade and 3/4hp will be plenty.

[Peter Quinn]

Lance, In a recent conversation with a rep from Laguna I was discussing buying the platinum mortiser vrs buying the XYZ axis table and making my own with some steel my dad has. The guy I spoke to was the south and Latin American market rep, and told me he has seen plenty of homespun creations on field trips to wood shops south of the border.

He discussed a verticle band mill/horizontal mortiser that was fashioned using the chassis and motor from an old VW bug as the central component. I'm thinking a 440 6-pack would represent a significant upgrade, only question is how would you geer the rear end? Are you going for 1/4 mile speed or top end?

That's a beautiful car, thanks for the picks. My buddy in high school drove a 69 Superbee with a 383, 4-11 rear end, 4-Speed stock hurst t- shift. It was all stock set up for the 1/4 mile from the factory. I loved that car, he always wanted a 440-6. My wife drives a magnum, that's as close as I'm likely to get!

[Lance Norris]

Peter... right now, it has a 3.23 rear gear. It had a 3.91 when I got it and it was too low for the driving I like to do. The Chrysler 8-3/4 rear end has a center loaded gear assembly, which is nice because you can swap gears in about 2 hours. You just have "pigs" loaded with different ratios, pull the axles and unbolt the pig, swap in another and then bolt the axles back. Nice set-up. Ive driven to National Trails Raceway near Columbus Ohio for the Mopar Nationals with the 3.23s, unbolted and installed 4.56s, race, swap and drive home. The motor is a 68 440 magnum with the cars original 1970 six-pack. I dont know where the original motor went, but most of the car was still in great shape when I got it. Bench seat, column shift automatic, Air-Grabber hood. I havent been into the motor, but other than a lumpy cam, its all stock w/ iron exaust manifolds and full dual exhaust. Best run with the 4.56s--12.54@117 mph. Not bad for a car thats 7 feet wide and 22 feet long.