PDA

View Full Version : 3phase bandsaw conversion



cadwiz
03-26-2007, 07:55 AM
So I'm restoring this old Delta bandsaw and thinking ahead. It's a wood saw so the high speed is completely useless for metal. I was thinking of restoring to original and giving it back to the friend that gave it to me as a goodwill gesture. Unfortunately, the honkin big original Delta 1/2Hp repulsion motor is scrapped, too much saltwater damage. I want to slow this thing down for appropriate metal speeds but also don't want to have to add a jackshaft. Can I put in a 3ph motor/VFD and slow this down enough to work for metal or is this just wishful thinking? I've done a little research and can't really find a definitive answer. Everbody goes off on a tangent about jackshaft additions. I know I could do that at the expense of hacking up the original pulley guard and drilling holes everywhere which is what I wish to avoid. So, anybody care to offer an answer: can I slow down with a 3ph/VFD approach?

Thanks, Cadwiz

Your Old Dog
03-26-2007, 08:21 AM
Have you thought about a jackshaft addition?

mark61
03-26-2007, 08:58 AM
My band saw used to be owned and run by an Amish family used for making big and long timbers for building barns. The father showed me some 12"x16"x 75 FOOT beams they made! They used a John Deer traction engine to power it. Helps to have 8 sons!
Anyways, I was going to use an old lawn tractor gear box to make it slow and adjustable speed. I lucked into finding a motor with a right angle gearbox 48 to 1 on a scraped something or other. I cut up to 3 inch thick steel with. Takes time pushing a 3" piece thru. Use your imagination!

mark61

Bill Pace
03-26-2007, 09:06 AM
Have you thought about a jackshaft addition?

Yeah, you might have to put a jackshaft setup on it........... HAH!! couldnt resist, Cad..

Not exatly the same, but heres my story (and I'm sticking to it!). I got one of those 16" import wood bands that rarely got any use and I was always needin a bigger metal saw, so........ It already had a jackshaft set-up, but the lowest was still WAY to fast for metal, so I had a spare 1hp DC set-up laying around rated at 1800rpm (as opposed to the 3600) so adapted it up looking for the variable speed to bring it on down to a useable speed. And it does, but... the torque at that slow speed suffers pretty badly. I have my lathe and mill on VFD's and the torque on them hardly seems affected at the lower speeds ............sooo, --- I think a VFD'd 3ph 1800rpm on a wood saw would prolly work quite well.
Am looking around for this type setup as a replacement on the saw,... it gives indications it would work pretty well

John Williams
03-26-2007, 10:25 AM
Baldor makes a 3 phase 1140 rpm in 1/2 hp. Works very well on my lathe. Would probably work well on a bandsaw with a vfd also. Got mine on ebay for $50 plus shipping...

motomoron
03-26-2007, 10:47 AM
How about a really big pulley?

My dad has a couple stone-age bandsaws. One has a DC motor with a speed controller, the other a big honking Baldor crafted by guys in a cave with clubs. That one also has 2 pulley sets; one that's about 1.5-1, the the other that's the best part of 14" in diameter with a tiny sheave for the motor. Use that one for light metal use, swap in the other pulley set and you've got wood speeds.

I've got a 14" Walker-Turner vertical I bought last year from a HSM board member. It's a 4 speed-dual range, with the lower wheel pulley equipped with what is essentially a planetary back-gear. 4 useful wood speeds, and 4 for metal.

I usually leave it set on the slowest high range speed with a 1/2" x .032 variable pitch bi-metallic blade. This is fine for hard and soft woods, most plastics, and thinner aluminum.

I've got a Jet 5x6 horizontal for anything else...

DR
03-26-2007, 11:17 AM
Some problems you might encounter by strictly slowing the motor......

The small V-belt motor pulley may not be able to transmit needed torque at very slow speed.

A "regular" VFD will not have enough torque at the slowest speed you need for metal (steel) cutting. A flux vector unit would, but more $$$'$.

If you think hard about the situation you'll realize there's a reason for the gearbox on the wood/metal saws.

SGW
03-26-2007, 11:38 AM
Based on my experience with the VFD on my millling machine, you can probably assume you can get down to 1/3 motor speed (20 Hz) and still have reasonable performance. If 1/3 the slowest belt speed would be slow enough for metal, then it's probably worth a try. No guarantees though....

DR
03-26-2007, 01:03 PM
Wood cutting bandsaws run around 3000sfm.

Steel cutting is around 100 to 150.

That means the reduction drive needs to be about 30:1.

SGW
03-26-2007, 02:31 PM
Jackshaft.... :D

Or a worm reduction.

wierdscience
03-26-2007, 10:05 PM
Do you want to keep the high speed range too?

Forrest Addy
03-27-2007, 12:11 AM
Jacksaft or gears. Period - unless you want a 20 HP motor that will turn down enough yet provide enough traction for a metal cutting saw band.

An automotive flexplate with ring gear attached concrentrically on the lower bandwheel and an "dis-engageable" pinion from the mating starter will give you 14:1 - 18:1 reduction meaning a simple step pulley and or a VFD will complete the picture. This will have to carefully engineered in advance of manufacture of parts and assemblies. A couple of wood mock-ups will help make a conversion that changes readily from wood to metal and back.

This is a fairly advanced project you propose but a careful step at a time approach will win through to success.

cadwiz
03-27-2007, 07:15 AM
Thanks for the replies. Wierd, no I don't need the high speed, already got a wood bandsaw I hardly ever use.

Forrest, I finally found your response the same question (it would have to be 9 pages deep on the search result). Looks like the trans flex plate and Bendix pinion is the way to go. I've got a 4x6 that takes care of my needs now so I'll take my time to engineer this right. Right now just working on derusting, painting, and replacing the broken parts of the saw. I'll start scrounging the parts I need as you suggested.

Thanks, Cadwiz

mark61
03-27-2007, 09:01 AM
Jackshaft.... :D

Or a worm reduction.



You could always go with hydraulic pump/motor and speed control. All the big saws at work use that.
mark61

Mike Burdick
03-27-2007, 04:37 PM
Cadwiz,

Another option you might look into is using a DC motor from an old treadmill. DC motors will supply the torque you need throughout the speed range. Treadmill DC motors usually run in the neighborhood of 1-1/2 hp. You may even be able to maintain the speed range for wood too without any belt changes. You’ll need to put a pencil to it to see for sure what can be accomplished.

Old treadmills can be purchased at most of the donation shops like the Salvation Army or Goodwill stores. You will need to check what stores or other venues are available in your area. If you don't find a used treadmill right away be patient - they will get one soon - you can count on it! :)

As an example, I just picked one up at the Salvation Army store for $2.50 (not a typo). It has a 1-1/2 hp motor and all the necessary electronics. While I was loading it into my pick-up the saleslady said she had one more and gave it to me free. The only drawback is that the motor is open so I need to make a cover for it and housing for the controls, which isn't difficult to do at all.

Good luck and please post back as to what you eventually do.

Thanks...

Mike

wierdscience
03-30-2007, 12:01 AM
Thanks for the replies. Wierd, no I don't need the high speed, already got a wood bandsaw I hardly ever use.

Forrest, I finally found your response the same question (it would have to be 9 pages deep on the search result). Looks like the trans flex plate and Bendix pinion is the way to go. I've got a 4x6 that takes care of my needs now so I'll take my time to engineer this right. Right now just working on derusting, painting, and replacing the broken parts of the saw. I'll start scrounging the parts I need as you suggested.

Thanks, Cadwiz

Oh,good,then it's easy.Right angle gear reducer and a chain and sprocket drive.If you need a gearboxfigure your ratio and send me a note,I have quite a few good used ones lying around,prolly got one with a matching motor too.