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Skill Band Saw 3386 -1.3 Hp Treadmill Motor Retrofit

Ulma Doctor

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Hey Guys and Gals,
i bought what i thought may be a cool little bandsaw,
a Skill 3386...

59-1/2" blades
120 VAC, 2.5 amps


IMG_3557.jpg IMG_3556.jpg

it worked just fine on pine up to 3/8" and it did great on the 5mm plywood.

but it didn't like hardwoods nor did it like any thickness over 3/4" in just about any material.

i'm not a woodworker,
but if i wanna cut a small piece of 2x4, i feel a small saw should do it without too much effort.
this saw had a hard time doing a 2x4, a couple times- stopping the blade all together.
the blade popped off at the same time.
i adjusted the blade for best travel and tried again with a coarser pitched blade
it cut a bit better but it really strained to move the cellulose.

Act 1:

so, i figured before i returned the saw,
i'd modify it permanently to prevent that possibility :grin:

i let the issue go for a month or so,
and then got the inclination to retrofit a 48 frame 5.5amp 1/3 hpp 115v motor into the saw....

OH my friends, the plan was immaculate i tell you !!!!!!
i'd pop in a new motor , wire it up and badda bing, cut wood like a beaver on steroids.

Well, it didn't exactly work like that....:bang head:

Here was the plan...
i'd remove the 2.5 amp 120 VAC (HA_HA_HA) motor and replace it with a (cheap) 1/3 hp motor drawing 5.5 amps @ 115 VAC.
i figured it would do much better than the anemic 2. 5 amp motor

2.5 amp motor, top 5.5 amp motor bottom
IMG_3558.jpg IMG_3553.jpg

i wuzgunna' just take the motor mount and modify it to suit the 48 frame motor i intended to use.

IMG_3573.jpg

well, i intended to use the extended length mount bolts from the 48 frame motor to mount the retrofit motor-
that wasn't gonna work, this time- the bolt circle ended up to be too close to the edge of the stock mount.
i considered making a larger mount plate.

IMG_3574.jpg

i traced a pattern onto the old looking new steel and was gonna start cutting,

then i had another idea, use a wire ring mount.
we use these in our industry to mount 48 frame fans

IMG_3572.jpg

this looked like it was going to be a slam dunk.....
but then reality set in.
i was going to need to make a pulley or make the spacer for the pulley to work with a .500" shaft i had.
here is the OEM pulley

IMG_3564.jpg

i didn't want to go through all the trouble of making a simple spacer,
so i made another pulley from 6061 :grin:

IMG_3562.jpg

IMG_3566.jpg
 
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Ulma Doctor

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ACT 2

i did some figuring and found out my new retrofit motor was a 1080 rpm motor.
the OEM motor was near 2000 rpm by ear
the original pulley od was 30.8 mm
to compensate i could go larger on my drive pulley to gain some speed
i decided to go to 35 mm,
( it's all going together perfectly i'm tellin' myself - :bang head: )

After turning the od and figuring the pitch (35mm OD.100"pitch 60°tool .060" doc)

IMG_3569.jpg

i drilled and reamed the bore to .500"

then, i used my (not so) secret weapon...


i used the crossdrill fixture to drill the set screw hole- works like a champion!!!

IMG_3570.jpg
 
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Ulma Doctor

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here is the OEM and the Retrofit Motors side by side

IMG_3571.jpg

i did the arithmetic and found out i was woefully under-speeding the blade

formula:
(Motor RPM X Motor Pulley Diameter) / (Driven Pulley Diameter X Saw Wheel Diameter X 3.14) / 12

the OEM i figure was traveling near 650 sfm - (2000 x 1.22) / (1.579 X 9 X 3.14) / 12 = 656 sfm
my new arrangement was coming in at near 390 sfm - (1080 x 1.378) / (1.579 X 9 X 3.14) / 12 = 389 sfm

so i went along my happy way.
i finished the retrofit, or so i thought


i turned the saw on and i could tell there was not enough power, even for my high expectations

i thought i could live with it, if it were not going to bog down
boy was i wrong.
it was better than oem,

but i want more!!!!!
 
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Ulma Doctor

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ACT 3
DC Treadmill motor Retrofit

after having difficulties mounting and belt adjustment on the ac motor side of things,
i made considerations for using a 1.3 hp @95VDC treadmill motor and a KBMM-118 controller i had lying around instead

IMG_3577.jpg

i tuned the KBMM-118 to a nice no load speed and decided not to use the P3 high speed pot tab on the board.
the reason,
is that with the P3 enabled, the blade speed would reach dangerous over-speeds

IMG_3578.jpg IMG_3579.jpg

i clamped, then drilled & tapped my proprietary eyeballed 3 lug pattern on the flange the OEM motor mount to accept the DC motor assembly
and cut the stub threaded end from the motor and then mounted er' up

IMG_3576.jpg IMG_3586.jpg

IMG_3585.jpg

since i already had a pulley made, i just had to punch the bore out to 17 mm
i didn't have a 17 mm reamer, so i drilled to 41/64 then bored to a 17.01 mm finished size.

i hacked the crap out of the main housing to create clearance for the treadmill motor.
a necessity beyond my control.
i was in too deep and not going back :bang head:

i was concerned about dust control so i made use of an under utilized recyclable,
milk jug plastic

i mocked up a simple dust shield for goofs and expanded on the idea

IMG_3587.jpg

after a couple attempts, i made good templates
from these templates i made some respectable dust shields
there is 2 layers, with a floater in between to try to keep the dust away from the dc motor

IMG_3582.jpg IMG_3583.jpg

i did final fitting of the motor and did the pulley alignment and locked er down.

i have about .100" clearance between the pulley and the saw wheel,
but it runs without interference ( sorry poor picture below)
IMG_3584.jpg

(if clearance becomes an issue, i can easily remove and shave down the pulley)
 

Ulma Doctor

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Act 4

I added the control board and connected the wiring in the OEM saw controls
and took it for a test run
the speed was too fast so i turned the KBMM-118 down to acceptable levels

here is a couple shots of the 10k potentiometer i used

IMG_3580.jpg IMG_3581.jpg

here is the diagram fro the KBMM-225- it wires up similar to the KBMM-118


note :Max hp is 1.5 on 115vac control with heat sink
external cooling recommended

KBMM diagram.jpg

i have yet to mount the KBMM-118 , the potentiometer, or the enclosure.

i gotta leave something for act 5 :grin:
 
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dlane

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Sep 27, 2014
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Hi Mike, it’s been a while. I thought you had a band saw already. Anyhow good luck with it.
 

brino

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then, i used my (not so) secret weapon...
i used the crossdrill fixture to drill the set screw hole- works like a champion!!!
Yep the secret is out!
I used mine (a shameless copy of yours!) just yesterday to drill two set-screw holes in a shaft coupler for my farther-in-law.

and took it for a test run
the speed was too fast so i turned the KBMM-118 down to acceptable levels
........i gotta leave something for act 5 :grin:
Well does it work?

You're just a Cut Tease!

-brino
 

markba633csi

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Apr 30, 2015
Messages
4,248
Hi Mike- I have a Skil belt sander of that series/vintage and it's a piece of c**p too.
A heroic effort on your part tho, slow it down even more and you can cut metal
Mark
 

Ulma Doctor

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Hi Mike, it’s been a while. I thought you had a band saw already. Anyhow good luck with it.
Hi Derrick, i hope all is well- it has been a while !
i have meat cutting saws at the shop i can use, but this is my only bandsaw at home

Yep the secret is out!
I used mine (a shameless copy of yours!) just yesterday to drill two set-screw holes in a shaft coupler for my farther-in-law.
Well does it work?
You're just a Cut Tease!
-brino
nice to know that my projects give other's ideas for doing stuff!

yes sir, the saw works!
i'm gonna make a short video and let the peanut gallery see! :grin:

Hi Mike- I have a Skil belt sander of that series/vintage and it's a piece of c**p too.
A heroic effort on your part tho, slow it down even more and you can cut metal
Mark
Thank you very much Mark!
i just hate it when you have (realistic) expectations and the product falls short.
thanks for the idea in regards to the metal cutting!
 

Ulma Doctor

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ACT 5

i got the saw in a relative state of readiness today,
although i have been working on the saw for a week off and on.

since the video,
i needed to get an electrical enclosure and contemplate mounting solutions.

the first thing i did was come up with a reference area to measure where everything was going to mount.
luckily the main casting had a trapezoidal feature.
the casting protrusion was going to be my mount point for the electrical enclosure.
the protrusion is a thick part of the main casting.
on the interior of the casting, there is a mount point for a brush for the lower wheel to keep chips debris from derailing the blade

i drilled and tapped the holes to 1/4"-20 tpi
IMG_3601.jpg

i cut a piece of reclaimed 1.5"x 1/2"x 6" 6063 aluminum and laid out the mount points on the electrical enclosure.
i transferred the holes and drilled the enclosure for the mount.

IMG_3606.jpg

i drilled a 2-3/4" hole for the fan inlet and sandwiched an improvised nylon scrub pad filter and a small piece of expanded steel to keep the scrub pad out of the fan.
i tapped the fan mounting holes to #10-32 on 3 holes,
(the 4th hole had interference with the enclosure mounting :bang head:)
the fan was sufficiently captured with 3 screws, so i'll live with it
IMG_3607.jpg

i mounted the KBMM-118 and the potentiometer to the enclosure, and plumbed rest of the the wiring through

when i made my video, i was ignorant to the fact that treadmill motors have a fan integral to the design of the flywheel.

that fact was pointed out ,astutely, by a good friend.
he made recommendation of keeping track of the motor temperature.
thanks for the thought and concern!

so with this in mind, i considered ducting the control box air wash through the dc motor.
i prepared by using a high volume/high speed 2-3/4" 115 vac fan,
to get a large volume of air circulating both through the control box,as well as using the clean air to cool the motor.

the wheels were set in motion,
i drilled (read: and hacked) a 3" exit hole on the aft side of the enclosure.
i used commercially available 3" water heater exhaust expanding aluminum duct and sheet metal couplings,
to rig up a 180° cooling elbow , from the big box store.
the fit was glove-like over the DC motor, i just had to notch for the carbon brush holders.
i was able to use a 3" clamp to hold it on the motor and box.
i added some anti-friction wrap on the potential wiring rub points.

IMG_3608.jpg IMG_3605.jpg

here is a side view,
the potentiometer is in the center knockout port.

i used the wrong port of the enclosure to hold the potentiometer ,
it was messing up mounting the incoming power to the enclosure.
there was only a 3/4" knockout there, so i fabbed up a bushing/spacer and washer for the 1/2" electrical fitting.

IMG_3604.jpg

here is a picture of the control box, motor, and (questionable) cooling system, looking to the southeast

IMG_3602.jpg


and one shot looking straight down on the enclosure

IMG_3603.jpg

i taped over the enclosure knock-outs in an attempt to make the box as airtight as practical.
i still may add a gasket to the top cover, not that it fits poorly,
but just preemptively addressing the leaking cooling airflow to the motor.


let me tell you all, i did things the hard way on this build.
everything took twice as long as expected, but the performance is flawless

the retrofit, was less than flawless-
but, i'll take performance over appearance any day of the week ;)

i'll be adding fuses for both the ac and dc circuits,
so the thread isn't over quite yet...

see you all on the next episode,
same bat channel, check your listings for times
drink your Ovaltine!!!
 
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middle.road

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Inspiration! I like the cooling system, ingenious.
I've got three in a round-tuit crate - want to do the Logan, the bandsaw, and a Craftsman 4x36" belt sander...
Missed out on two more donors at an estate sale this past weekend, but then I'm out of room in the shop (as usual).

"drink your Ovaltine!!!" -hehe
1567452923870.png
 

Ulma Doctor

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Joined
Feb 2, 2013
Messages
581
here is a snapshot of some test cuts!

DSCN0173.JPG


lol,
here is what it really cut, (less the spark plug airplane)
DSCN0176.JPG


thanks for reading!
 
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