Need help with math...

[AL P]

Hey guys..I give up...I need some help with a math scenario..:banghead:
Here`s the deal...

motor "A" spins at 1725 rpms..its currently spinning another motor VIA a belt (we`ll call it motor "B"), at 384 rpms..
motor "A" has a 3 7/8in pulley......

now..
if I switch motor "A" to a 3400 rpm motor..with a 2 3/4in pulley..what rpm would motor "B" now spin at??..

so to re cap.., motor "A" is a 1725 rpm motor, with a 3 7/8in pulley, and is currently spinning motor "B" at 384 RPMS..

what RPM would motor "B" be spinning at, if motor "A", was changed to a 3400RPM motor, with a 2 3/4in pulley??

Just to add, if this helps at all..
motor "A" (1725 rpm motor - 3 7/8 pulley) has its pulley currently rotating 4 1/2 turns, per 1 turn of motor "B"`s pulley..

Thanks..
and sorry for the off the wall question..

AL P

[overdrive75]

755 RPM or 576 RPM depending on how and where you round in the math, and how you calculate it. There are multiple ways.

[RedWhiteandBlue]

If the Motor "B" has a pulley that is about 8 1/4" in diameter then I understand you correctly and I am doing the math right....I think. Then your new RPM of "B" pulley will be approx. 381 (depending on how you round everything out while doing the math but I could be way wrong too...Blue

[overdrive75]

Ok lets see here, Motor2(1st RPM)/Motor1(1st RPM)=Motor2(2nd RPM)/Motor1(2nd RPM)

Motor2(2nd RPM) is the unknown.

After solving above equation for Motor2 (2nd RPM):

Motor2(2nd RPM) = (Motor2(1st RPM)*Motor1(2nd RPM))/Motor1(1st RPM)

Motor2 (2nd RPM) = (384*3400)/1725

Motor2 (2nd RPM) = 756.87

Solution two:

Find Ratio of pullies based on speed

Motor1 (1st RPM) / Motor2 (1st RPM) = Pully ratio

1725 / 384 = 4.49

Motor2 (2nd RPM) = Motor1 (2nd RPM) / Pully Ratio

Motor2 (2nd RPM) = 3400 / 4.49

Motor2 (2nd RPM) = 757


Solution 3 same as solution two, but using AL P's rounded Pully ratio

Motor2 (2nd RPM) = 3400 / 4.5

Motor2 (2nd RPM) = 756

[v4eva]

537

[v4eva]

by the way.`motor` B isn`t a `motor`,its a `load`.

[opsled]

Math SUCKS!!! after a 12 hr day.

I'm not even going to make my brain try this one.

Good Luck, opsled :drink1:

[AL P]

Thanks for the reply everyone!!!

I believe 537 is correct??..
the second pulley is about 16 inches or so...

I probley was`nt very clear in my post, sorry about that....
anyway, motor A, has a 3 7/8in pulley, and motor B has about a 16in pulley....motor A is currently a 1725 rpm motor..and the 3 7/8 pulley on it, turns 4.5 turns, for one turn of the 16in pulley on B..
which ends up turning B at about 384 rpms..

what I`m wanting to do, is go with a 3400 RPM motor (higher HP/amp motor), and turn motor B a bit faster..(but NOT more then about 550 RPMs)

Thanks again everyone..I`ve been trying to figure this out for a few days, and have`nt come to any certain conclusions..LOL

AL P

[mark the shark]

Thanks..
and sorry for the off the wall question..


We wouldn't have it any other way, Big Al!

I believe that with your 3.875" drive pulley driving a 16" pulley, your driven pulley ratio is .242. Multiply that by 1725 RPM and the 16" pulley should be turning 417.45 RPM.

A 2.75" drive pulley would make your ratio .171. Multiply that by 3400 RPM and your 16" pulley should be turning 581.4 RPM.

Or I could be full of baloney.

Shark

Or go here and plug in some numbers: http://www.csgnetwork.com/pulleybeltcalc.html

[v4eva]

according to the numbers in your first post,the second pulley is 14.4 in.

[AL P]

I measured the second pulley last night, and it came out to 16.5 in..(or atleast very, very close to it..)

Thanks for the link mark..

AL P

[4with4]

I'll throw in my 2 cents as well. I got your driven pully to be just over 17". With that number used in my calculations, I got your new driven pully speed to be 537 rpm's. A couple others came up with that answer as well.

Ian