Bandsaw pulley calculation question

jack shaft

 

You want 250 FPM. A 12" dia. bandsaw pulley is 12 x 3.14=37.67" dia.
250 x 12=3000" per minute. 3000 / 37.67=79.6 RPM.--So---call it 80 RPM to get a 250 FPM blade speed.

Your motor turns 1750 RPM 1750 / 80= 22---You want a 22:1 ratio.(overall).

Lets do it in 2 equal stages. Square root of 22 is approx. 4.7

2" motor pulley x 4.7=9.4"" jackshaft pulley --thats the first stage reduction.
Put a 2" pulley on the other end of the jackshaft pulley, and a 9.4" pulley on the bandsaw.---Thats your second stage of reduction.

So ---Here is the proof
1750 RPM motor divided by 4.7=372.3 RPM at jackshaft.
372.3 RPM jackshaft divided by 4.7=79.22 RPM at bandsaw.

79.2x 12 x 3.14=2984" per minute blade speed

2984 divided by 12=248.7 foot per minute blade speed.

You probably can not get a 9.4" pulley, so try for either a 9.5" dia pulley or a 10" dia pulley----It won't change final speed enough to matter.

 

400 dollars on a motor, wow. maybe a speed reducer from Grainger would do the trick. Can't be too much, hell of alot less than 400 dollars

 

"I value your contribution to the HAMB greatly, but at this moment I will not accept any more negative feedback"

 

good luck with the pulleys

 

I have seen gear reducers on ebay for pretty cheap...If the math is right wouldnt a 3:1 gear reducer work as well?

http://cgi.ebay.com/GROVE-FLEXALINE...7691238QQcmdZViewItem?_trksid=p3286.m20.l1116

Or a steering quickener...reversed.

 

there was an article in a old rod magazine that showed doing just what you want to do , I think he got a pulley from a clothes dryer, just a thought???

 

I think I like the swiping a jackshaft off of a drill press idea best so far.

brianangus's pully sizes will work jim dandy.

 

i googled this it may help, but lotta ideas here


http://smg.photobucket.com/albums/v337/johnoder/36 Crescent/

 

ok i got this from "the home shop machinist" magazine jan/feb 2004

on your drwing bottom to top
motor pulley-- 1 1/2
to a
6 in pulley
on a jack shaft with a 1 1/2
to a 12 pulley

with their 13.75 in saw wheel their math shows 194 feet/min

they also show the math for going straight from the 1 1/2 to the 12 saw wheel pulley will give you 776 feet/min

grainger has the pulleys

there is also a story in american rodder oct 1993 if you have one in your stash.

i'm in the midst of doing the same thing

hope this helps

later jim

 

dude's just trying to help.

even seemingly bad ideas can lead to good ones. gear reduction units are NOT cheap. what IS cheap though is an old manual transmission. find the smallest one you can get for next to nothing, and you can have slow speeds for stainless, up to fast speed for blasting through wood when need be. you could even use the gear box from a riding lawn mower.

 

I have seen it done using an old car transmission, off a 4 cyl. car.--once you get the bell housing and tailstock off, the actual ****** is quite small.--Problem is, you can only get a maximum 4:1 reduction out of them. This means that you need one pulley and belt set between the motor and input shaft, and a second pulley and belt set between the output shaft and the bandsaw shaft. It does however give you the option of higher speeds if you need them simply by shifting the ****** into a higher gear.

 

Thanks Ray, at least I got the calculations right.

Being "positive", try getting a multi-size pulley with 2" and 6" on each end and then mount to one end of a shaft/bearing ***embly. I am sure you can find this in the Grainger book. Hook the motor belt to the 6" end and then the saw belt to the 2" end.

This should give you the 3:1 reduction needed.

Sorry if I offended you in any way.

 

Here are thread worth reading for more ideas on a jackshaft if your interested in going that route.
http://www.jalopyjournal.com/forum/showthread.php?t=138415&highlight=bandsaw+jackshaft

 

I've used a transmission out of a riding lawn mower to get big reductions in RPM's and also to have multiple speeds. Junk riding mowers are not too hard to pick up cheap. Some already have a pulley from a belt drive from the gas engine.

It's more fab work but if you need to mount pillowblock bearings for a jackshaft -- fab work will be required for mounts anyway.

Movin/on

 

There's a post on here somewhere that explains how to use a treadmill motor on a wood band saw to convert it to a metal saw. D/C motors can be slowed down with potentiometer. A/C motors will only work at one voltage without burning up.

heres the post
http://www.jalopyjournal.com/forum/showthread.php?t=223009&highlight=treadmill

 

Here's my bandsaw:
An old Delta Milwaukee 14" from the '30's or '40's. I slowed it down to cut metal with a 19.5:1 gear reduction mounted on a simple angle iron frame below the saw. There's a further 3:1 reduction (pulleys) between the motor and the gearbox input, and two sets of pulleys on the output and the saw, to give two final speeds- about 90 ipm for thick/ tough steels, and about 200 ipm for thin steel, aluminum, wood, etc. The little idler pulley is needed to tension the belt on the faster speed.

Try used machinery dealers and rebuilders for an inexpensive reducer.

 

You want to get Bi-metal blades for cutting steel. there not cheap about $20. but they last a lot longer. It has a hi-speed edge welded to a flexible back. I have a jack shaft on my band saw, 2 pulleys on the electric motor, when I want to cut wood or aluminum I just switch the belt to direct drive on the motor and take up the belt slack with a spring loaded idler.


Ago

 

Is it me,or is there a lot of band saw issues,the last couple days????

 

Yeah Bob! I asked about bandsaw blades last night!

 

hahaha! Hadn't seen the word "bandsaw" on the HAMB before,and then saw it 4 times in the last 24hrs,LOL.....

 

quick thinking I would say ( 2:1725 :: X : 200 ) them multiply 2 X 200 and then devide the 400 into 1725 and I would say try a 4.25" diamiter pully. You could also try an adjustable pully

 

Did you quote someone else on this? This would come in handy those times someone gets under your skin on here.

 

I am in the middle of doing this myself & would like to know how yours turned out. I think the system by brianandgus is probably right but would appreciate some more feedback from you.

 

any metal band saw i have seen used a primary reduction that had steped pullies and then a secondary reduction , this is so you can change you band speed, not unlike a drill press.

 

Flatford39--My system worked out great---I use it every day.---Brian

 

my 2 cents worth,

I would use a Variable speed drive pulley with a adjustable motor base.
that way you just crank the handle on the motor base to speed up or slow down the saw just like on a DoAll band saw.
some mini bikes used them as a clutch.

 

something like this and I'm not saying to BUY THIS ONE, it's just another way to skin a cat.

<TABLE cellSpacing=7 cellPadding=0 border=0><TBODY><TR vAlign=top><TD align=middle>
</TD><TD align=left>218352A - Torq-A-Verter, 3/4" Bore 12 Teeth, #35 Chain Torque Converter

The Torq-A-Verter is a fully automatic variable speed drive system (torque converter). There are no gears, no complicated controls or levers and neither manual shifting nor clutching is involved in these systems. The unique design of the movable face in each driver and driven member causes automatic infinite variation and thus smooth shifting action between the system's low and high range in immediate response to changing load and/or travel conditions..with constant optium ratio between engine and drive wheels ensuring that you get the use of all the power your engine develops. Since ratio selection and "down-shifting" is automatic, braking and vehicle control are enhanced. The Torq-A-Verter system engages at 2200 rpm. As the engine throttle is "opened" the drive belt engages, driving the driven unit at it's largest diameter. This is the most powerful ratio of the system (2.7:1). At the highest speed (overdrive) and lowest load demand the driven unit pulley flanges are wide open providing the smallest possible belt contact diameter. The drive unit pulley flanges are closed to provide the largest possible belt contact diameter. This gives the system an overdrive ratio of .90:1.

Replaces OEM #: 218352

Suggested Retail Price: $208.25
Our Price: $169.99 </TD></TR></TBODY></TABLE>

 

That's mine

I did the jackshaft, and it turned out great. I cut many miles of steel, since I did the whole set-up.

 

Brianangus

Your calculations worked perfectly. I did the jack shaft today on my wood cutting band saw using 2" & 10" sheaves & I was able to cut thru some 1 1/2 x 3/16 angle iron with a really screwed up blade quite easily. Going to order new blades later today.

Thank you for the help & direction.