tightening new air compressor belts

[metalmagpie]

I'm setting up a vertical 7.5 hp air compressor. The pump, motor and saddle came from an old horizontal tank that failed hydro. I welded the saddle onto a vertical tank I found that was ASME rated and passed hydrotesting. Now I'm at the point where I have to use both hands to pull on the motor and keep it straight (to tighten the belts) and then reach underneath the saddle with my 3rd hand to tighten the nut on a motor mount bolt while holding the wrench to keep that bolt from turning with my 4th hand. Actually, when I try to tighten the belts (there are 2 B78 belts) by pulling on the motor I can't even pull the kinks in the new belts straight let alone properly tension them. I fastened the pump down solidly and used a 5" hydraulic cylinder powered by a hand pump (porta power setup) to push the motor away. It easily tightened the belts but the motor went all crooked in its slots and by the time I'd gotten the motor all aligned again the belts had gone slack again. Next I used a turnbuckle with eyebolts substituted for the normal ends. It pushed the belt tight but after I got the bolts tight I noticed that the pull had skewed the air pump w.r.t. the saddle.

This is trickier than looked! Any tips from the experienced?

metalmagpie

 

[rancherbill]

 

[isb cornbinder]

Keep at it. The experience will make you a better person.

 

[isb cornbinder]

Something I tried was this. I pulled to motor as tight as I could get it and I lifted the back of the motor up. I had two bolts through the tank mounts which I tightened. Then I forced the back of the motor down which tightened the belts. You may have to return and retighten after a few days of operation. the belts will wear a little and settle in.
A good ratchet strap may work for you.

 

[Ing3018]

My compressor motor sits on an adjustable base like this: https://www.surpluscenter.com/shop.axd/Search?keywords=Motor+base
Easy to maintain alignment and achieve the desired tension.
Otherwise, long prybar and snug the bolts. A mallet to shift it around.

 

[walta]

To my eye the diameter of the motor pulley looks to small to transfer 7.5 horses and you are trying to make the belt tight enough not to squeak.

My guess is the pully on the pump was designed to work with 6 inch or so pulley on a 1750 RPM motor and your motor is 3400 RPM so you installed a 3 inch pulley.

Find room for a jack shaft or find a slower motor.

Walta

 

[Walkers]

To my eye the diameter of the motor pulley looks to small to transfer 7.5 horses and you are trying to make the belt tight enough not to squeak.

My guess is the pully on the pump was designed to work with 6 inch or so pulley on a 1750 RPM motor and your motor is 3400 RPM so you installed a 3 inch pulley.

Find room for a jack shaft or find a slower motor.

Walta

Mine has a 3600 rpm motor and the smallest sheave available for the shaft, maybe 2.5" IIRC. Igot a bunch of flack about how there wasnkt enough wrap, too small a pulley, etc. it has been working that way for over 15 years.

 

[walta]

Mine has a 3600 rpm motor and the smallest sheave available for the shaft, maybe 2.5" IIRC. Igot a bunch of flack about how there wasnkt enough wrap, too small a pulley, etc. it has been working that way for over 15 years.

Ok put the porta power in between the 2 pullies and tighten the belt and call it a day.

Walta

 

[nadogail]

One should not argue with success, if it works it should be "good enough".

 

[Walkers]

Ok put the porta power in between the 2 pullies and tighten the belt and call it a day.

Walta

The belts don't need to be that tight, why would you need a porta power? Mine is a horizontal tank, fairly easy to pull by hand. The OPs is a vertical unit, so he is just in an awkward position for pulling.

 

[mogandave]

Lay the compressor on it's side.

Gravity should be a friend.

 

[The Tool Tyrant]

Patience, persistence & problem solving are required to CORRECTLY align and tension V-belts without a motor alignment plate.
#1, check the owners manual for correct belt tension.
#2, use a straight edge across the face of the pump sheave, spanning across the motor sheave, measuring between the straight edge and the sheave belt grooves.
A few compressor manufacturers include a motor tensioning bracket (1/4"x 1-1/2" +/- flat bar) that attaches under the motor/ pump platform using the 2 motor mounting bolts closet to the sheave and extends forward past the edge of the platform. Picture a threaded block welded on top in which a bolt is threaded into which pushes against the edge of the platform, thusly pulling the motor.

I've found that the opposite end of the motor usually needs to be pushed in the opposite direction to properly align the sheaves.
Just take your time.

 

[isb cornbinder]

On a cold Canadian Morning, is is common for the Baldor motor to overpower the belts. The compressor responds with a slow start and in less than a minute the slippage fades away. I use those multi piece link belts on every machine including my JUKI sewing machine. I painfully discovered that extra caution was wise when manually assisting the sewing machine. The belt grabbed me fingers and I learned something important while my lights went out.

BELT LINK A/4L 1/2IN. PRICED PER FOOT

With POWER TWIST make up any required length of drive belt and install without dismantling the machine.

www.busybeetools.com

 

[TRWham]

My Kellogg has a banded 3/B70 belt. When I installed it I used shims to wedge between the motor and pump to tighten the belt.

 

[The Tool Tyrant]

I've tried a couple of different sheave spreaders, but you can't rotate the sheaves while using them. A quick and painless spreader between the motor and pump can be made by cutting a piece of 1/2" pipe to the appropriate length, threading a nut onto a 1/2" diameter x 3" +/- bolt, place the bolt into one end of the pipe, hold the bolt head with a wrench while tightening the nut against the pipe, increasing belt tension . Can't get any easier.

 

[PoorUB]

On really awkward motors I have built puller screws. Two of them. A bit of flat iron welded to a 3/8" threaded rod with a nut, and a piece of angle iron with holes drilled to match the rods. Mount the rods to two of the motor mount bolts and through the angle iron and tighted the nuts.

 

[metalmagpie]

To my eye the diameter of the motor pulley looks to small to transfer 7.5 horses and you are trying to make the belt tight enough not to squeak.

My guess is the pully on the pump was designed to work with 6 inch or so pulley on a 1750 RPM motor and your motor is 3400 RPM so you installed a 3 inch pulley.

Find room for a jack shaft or find a slower motor.

Walta

Extremely sage wisdom, Walta. Only I didn't post a picture ..

 

[CraigStu]

I am thinking that if you can find a way to pull the motor vs push it, you have a much better chance of it staying straight. You need to pull it at a point that is centered between the belts and parallel to them.

 

[MacMcMacmac]

You can scribe a line across the saddle with a square as far as necessary past the motor base, bolt the motor in place so the edge of the motor base just meets the line, then roll the belts on.

I used to use a large turn buckle with some large key stock welded on the stubs where the eyelets were cut off. The key stock was bent to a shallow "v" and welded such that the corners of the keystock centered it in the groove and the vee shape kept it across the diameter of the pulleys. If you get a big enough turnbuckle you could just perhaps split the eyelets at the outermost point with a zip disk and open it up to create a crescent shape to achieve the same thing without any welding.

 

[mogandave]

Bar and block

 

[PoorUB]

You can scribe a line across the saddle with a square as far as necessary past the motor base, bolt the motor in place so the edge of the motor base just meets the line, then roll the belts on.

That is a good way to ruin belts. You might get by with it, certainly on a low use machine, but I would never recommend it. I worked with a guy that would roll on belts. After he did a pair of belts I had him take a look and rolled the pulleys over slowly. You coulad see a jog in the belt where the fibers were stretched and broken.

 

[niget2002]

I used clamps that have the ability to be spun around and used as spreaders. One on the front of the motor and one on the back. Pushed the motor out while testing the belt, then tightened all the bolts.

 

[Spareparts]

I got a 1" square piece of bar stock, drilled 2 holes thru and tapped them 3/8-16", 2 pieces 3/8" all thread with 2 nuts welded
on the ends. When I got it all lined up on the base plate welded them down. Just loosen the motor a little and tighten the all thread
a little, also handy to square the motor up so the belts run true.