Wood speed is something like 2000 to 3000 fpm or 5 times what you
need for metal. If you want to do wood, I'd suggest some sort of
belt deal to switch back and forth. You would need to change
blades also so why not just make a big deal out of it and do it
right.
You want the 5120 to match up with 565 fpm. You didn't say what
size wheels you plan but assuming 14" or so you will need about
150rpm on the shaft or a 34 to 1 reduction. Only thing that will
do that in one step is a worm drive. I'd suggest a belt reduction
of about 6 or 8 with a gear reduction of 4:1 or 5:1. You might be
able to use the gear reduction bearings for the drive pulley mount.
For 1-1/2 hp, the smallest v-belt drive pulley you should use is
2", 2-1/2" is better. Go smaller and you will have slippage and
excessive belt wear. Assuiming you can even get a 12" pulley,
that means a maximum of 6:1 reduction in a single V-belt
recuction. 2x on this would be 36 to 1, about where you want to
be. You can source the large pulleys at a farm store, they have
an array of hubs, plus an array of wheels, weld them up. Sounds
awful, works fine, about $16 for a 12" pulley in your choice of
hub sizes. If you still want to do wood, use 1 reduction for
wood, 2 reductions and a jackshaft for metal.
You should be able to get the DC motor to run at 1/10th rated
speed if you have good parts. Keep in mind that the TORQUE
available is the same at all the various speeds. Since HP is
speed x torque you have 1/10th the HP at the lowest speed.
Exceeding this means overheating the motor.
Cheers.
Roy wrote:
In the process of making my 3 wheel bandsaw. I am wanting to use a DC
motor of 1 1/2 hp with a speed controller, but would like to add a
jack shaft. as well, just to make sure I can keep up the torque on the
saw at the necessary speeds needed for general metal cutting. The
motor I have is 1 1/2hp Leeson Electric, (removed from a typical
treadmill) and runs up to 5120 rpm and pulls 15 amps. The controller
I have for it is made by Dart and is supposedly capable of handling up
to a 2 HP motor. I understand this controller is supposed to be able
to keep the motors torque up at low speeds, but I would not bet my
life on it. Guess I am just paranoid, as I do not have to much
dealings with DC motors and controllers.
So what ratios would I need to go with to get the saw down to useable
speeds for metal cutting? (Looking for 65 to 550 SFPM from what I
have found out in regards to speed), although it would be nice to
jack it up in speed for wood cutting.
Would I be better off initially reducing the speed with a gear reducer
that drives a jackshaft and then the saw or what? Or should I still be
able to get by with just a 4:1 ration jackshaft and rely on the speed
controller to do its job?
So far except for this problem, the project is going fine. I have one
more wheel (drive wheel) yet to cast and machine, shuld have my tires
next week, have the caster / camber tension assembly made, starting to
work on the blade guides. This brings anopther question to light. Lots
of saws today use simple ball bearing for guides. They seem to last ok
on my H/V bandsaw, but have a habit of allowing lots of crub get by or
get beat into the bearings or blade, so I was thinking on using some
guides similar to what DoAll uses. Is there any materials out there
that I can machine in a home shop thatw ould serve usefull in making
these guides. They need to work with 3/8" at a minimum to no more
than a 3/4" blade. Buying those Cool Cut guides is out of the
question, so I need to come up with a home brew deal. I was also
thinking of using a small engine valve tappet (like found in B & S
engines) that runs in a bushing and is adjustable in and out with a
setscrew. Any other ideas greatly appreciated.
Presently I have just the basic shape of the frame laid out and am
concentrating on making all the actual working parts, so I can juggle
things here and there, and the frame will be built around these last.
Looks like it will have a 17" + - 1" throat size, 8 1/2" to 9" cutting
height, stand 71" tall, have a width of 29" and be 8 1/2" in depth,
take a 107" blade is usiing the three wheels or a 86" blade if
utilizing just two wheels. Table size 20 x 22.
The table is still one item that I need to dio a bit of thinking on. I
wiuld like to be able to mill it out so I can use a push type rip
fence so it looks like a piece of steel plate or perhaps 1/2"
thickness is in order, so if anyone has any other suggestions on a
table they would also be appreciated. I already have a mitre / rip
gauge from a large Delta belt / disk sander that I would like to use.
Visit my website: http://www.frugalmachinist.com
Opinions expressed are those of my wifes,
I had no input whatsoever.
Remove "nospam" from email addy.