PDA

View Full Version : Air compressor belt tensioner



Robo
11-23-2013, 12:07 PM
Anybody have a simple slick design for a belt tensioner on a typical reciprocating shop air compressor? I've got a couple of ideas I want to incorporate but wondering if anyone has already done this and has one that works well and is relatively easy to make. Thank you :)

Ian B
11-23-2013, 12:50 PM
On every one that I've ever seen, tensioning is done by slackening off the 4 bolts holding the motor down and sliding it further from the compressor. Some kind of lever often helps.

A tensioner could be rigged to run on the back of the belt, but you then start flexing the belt in the opposite to normal direction, which'll shorten belt life.

Ian

jlevie
11-23-2013, 12:56 PM
That strikes me as a solution in search of a problem. Tension the belt as Ian B said and be done with it.

dp
11-23-2013, 01:01 PM
Two answers to a question not asked :)

I like the tension pulley on my Dodge truck and Jeep. The wheel is a large diameter thing, wide and flat, and has a durable bearing in the center. The adjuster is a screw jack. Available in any wrecking yard or over the counter. It can also be used with a spring rather than a screw jack so it will self-adjust over time.

Jono
11-23-2013, 01:26 PM
The reason why belt tensioners aren't common on compressors is the load's not constant, unlike a car, and belt life will suffer. If you need to have one, use a v pulley on the inside so the belt flexes one way only. As for the adjuster, I second dp, though not a spring for the above reason.

Ps Be careful to maintain as much wrap.on the wheels as possible, you're transmitting loads more hp than a car fan belt. All in all, tensioners are an inferior solution by far.

RWO
11-23-2013, 01:41 PM
Jack screw adjustable motor bases are a standard industrial component and can be purchased at most motor supply houses. http://www.globalindustrial.com/g/motors/motor-accessories/motor-bases/adjustable-mounting-base

RWO

dp
11-23-2013, 01:55 PM
I can't understand the comment that auto belt loads are constant. The engines go from 0 to 5000 rpm, AC goes on and off, power steering loads change every few seconds, alternator loads some and go as lamps, wipers, etc. operate.

Jono
11-23-2013, 02:44 PM
Yes, but they're not varying in intensity several times a second, which is what a compressor does. You only have to watch the belts jumping under load, not like the smooth run of a car. Industrial belts have a much harder time.

Robo
11-23-2013, 03:57 PM
Jack screw adjustable motor bases are a standard industrial component and can be purchased at most motor supply houses. http://www.globalindustrial.com/g/motors/motor-accessories/motor-bases/adjustable-mounting-base

RWO

That's exactly what I'm looking for and cheap. Thank you no need to even think about building one at that price :)

After looking at the size I need maybe I'm going to build one. Its a bit expensive IMO.

Highpower
11-23-2013, 04:37 PM
That's exactly what I'm looking for and cheap. Thank you no need to even think about building one at that price

After looking at the size I need maybe I'm going to build one. Its a bit expensive IMO.

I replaced the thin stamped sheet metal version on my band saw with one of those. The sheet metal brackets would bent and distort in use and cause the saw to loose belt tension. I made a 1/4" steel base plate to bolt to the saw and then had to shorten the heavier adjustable motor base to fit it, but it works so well I did the same thing on my air compressor. Solid as a rock now - I wish I would have done it years ago!

I bought my adjustable bases on sale from surplus center.... cheap.

http://img.photobucket.com/albums/v82/Highpwr/Shop%20Projects/th_OldNew.jpg (http://smg.photobucket.com/user/Highpwr/media/Shop%20Projects/OldNew.jpg.html) http://img.photobucket.com/albums/v82/Highpwr/Shop%20Projects/th_Newbaseplate.jpg (http://smg.photobucket.com/user/Highpwr/media/Shop%20Projects/Newbaseplate.jpg.html) http://img.photobucket.com/albums/v82/Highpwr/Shop%20Projects/th_Shortenedmount.jpg (http://smg.photobucket.com/user/Highpwr/media/Shop%20Projects/Shortenedmount.jpg.html) http://img.photobucket.com/albums/v82/Highpwr/Shop%20Projects/th_Motor_right.jpg (http://smg.photobucket.com/user/Highpwr/media/Shop%20Projects/Motor_right.jpg.html)

Edwin Dirnbeck
11-23-2013, 08:30 PM
Anybody have a simple slick design for a belt tensioner on a typical reciprocating shop air compressor? I've got a couple of ideas I want to incorporate but wondering if anyone has already done this and has one that works well and is relatively easy to make. Thank you :)
Please dont listen to the naysayers . When you have a proper tensioner with a typical thin mutigroove belt you get more belt raparound on your small pulley plus the belt does not need much tension because when the compressor starts and the belt stretches the tentioner takes up the slack.
I designed and instaled a very simple tensioner in 1975 and havent touched it except to replace one belt .I replaced a belt in1995 in 30 seconds with no tools .The reason that I did this is because the belt was tensioned by 4 nuts and bolts on the motor base .They were very hard to get to and the motor could easily get crooked. I am not at home right now ,I will try to post a picture on monday Edwin

digr
11-24-2013, 08:02 AM
This is what I did (http://www.shopfloortalk.com/forums/showthread.php?t=4592)for my air compressor

A.K. Boomer
11-24-2013, 08:48 AM
Yes, but they're not varying in intensity several times a second, which is what a compressor does. You only have to watch the belts jumping under load, not like the smooth run of a car. Industrial belts have a much harder time.

A cars AC comprendo is varying several times a second, and at higher rpm's way more than a conventional shop air comprendo, comprendo?

and incidentally - so is an alternator...

A.K. Boomer
11-24-2013, 09:33 AM
Please dont listen to the naysayers . When you have a proper tensioner with a typical thin mutigroove belt you get more belt raparound on your small pulley plus the belt does not need much tension because when the compressor starts and the belt stretches the tentioner takes up the slack.
I designed and instaled a very simple tensioner in 1975 and havent touched it except to replace one belt .I replaced a belt in1995 in 30 seconds with no tools .The reason that I did this is because the belt was tensioned by 4 nuts and bolts on the motor base .They were very hard to get to and the motor could easily get crooked. I am not at home right now ,I will try to post a picture on monday Edwin


In general I agree with your assessment --- esp. when it comes to the newer serpentine belts, actually a spring loaded tensioner is superior in design to conventional because of a multitude of reasons, first off like you say you can get more pulley involved - secondly is that you can actually run a lower initial belt tension and still have better non-slip results upon start up's and high loads just before shut off,
last but not least is the fact that it all but eliminates "belt whip" or "flutter" --- increasing the service life of the belt...

Conventional systems do not, they load the one side whilst the other gets loose and flaps around,
general wisdom would be to try and mount your comprendo up to the motor as close as possible to reduce this effect,
but now with two greatly different size pulleys youv run into another problemo,,, if you try to keep things compact you greatly limit the contact area of the smaller drive pulley,,,

Yet use a longer belt to increase the engagement degree's on the smaller pulley and your back to having copious amounts of flutter on the non-load side...

The reverse side tensioner eliminates this effect, and even though it's another component to run it's power saving benefits by keeping the optimum tension at all times will offset it's initial deficit....

But,,, On the old thick V-belt's this option can create another problem by flexing the thick belt in the opposite direction,,,
running a tensioner on the inside will eliminate this problem but it comes at the cost of yet again decreasing the engagement degree's on the smaller drive pulley...

all and all none of these examples are extremely critical unless you do something way off the charts.

My old Puma V-twin is running over 25 years now on the same belt and its set up conventionally and it's flopping around on the non-load side continuously...

Therefor, I would go for whatever is the most easiest and economical fix ...

Willy
11-24-2013, 12:17 PM
.....

Ps Be careful to maintain as much wrap.on the wheels as possible, you're transmitting loads more hp than a car fan belt. All in all, tensioners are an inferior solution by far.

That would have to be one heck of a compressor to exceed the typical loads encountered by an automotive fan belt. Consider 25 HP as a realistic load when all accessories are operating at their maximum load on the average car.
As an example, on a 450-500 HP diesel in an 18 wheeler when climbing a hill I will often have to select a lower gear when the thermostatically controlled fan engages. Keep in mind this is for the fan only even though this belt also powers numerous other accessories. Also bare in mind that these belts are standard automotive belts both in width and thickness.

dp
11-24-2013, 12:48 PM
Conventional systems do not, they load the one side whilst the other gets loose and flaps around,
general wisdom would be to try and mount your comprendo up to the motor as close as possible to reduce this effect,
but now with two greatly different size pulleys youv run into another problemo,,, if you try to keep things compact you greatly limit the contact area of the smaller drive pulley,,,

Two tensioner wheels in a truck configuration would solve all the problems. Two independent sprung tensioner wheels would solve all the problems. One tensioner wheel well placed would be a compromise and solve parts of the problem. Doing nothing solves no problems. Tightening the belts creates new problems.

Any attempt to correct the original problem is a test which may or may not succeed. Any failure leaves the door open for more testing. There may be no practical solution. Nothing is off the table as a solution. Nobody here yet knows what the solution might be. Nobody has offered a suggestion that is guaranteed to not work, and nobody knows which solution will be best because no tests have been done.

Conventional systems flap around because there is generally an impulse load and only two pulleys with two long fetches of belt between them (band saws would be an example of an exception to impulse loads). Rugged V-belts being cheaper than additional hardware, we've become accustomed to compressors that have flapping belts. Serpentine belts are a better solution for auto engines because it reduces the leg room needed for multiple sheaves, and one tensioner takes out the harmonic component on the unloaded span. Multiple load types (impulse from the AC, continuous for steering, alternator) are averaged to reduce the flapping thus reducing the design requirements of the tensioner. Back in the day an air compressor would have a very heavy flywheel to help damp some of the impulse problems and it was also configured as a fan. That is still the case for commercial compressors, but many of the big box stores have light weight wheels that offer little damping.

Robo
11-24-2013, 04:55 PM
This is what I did (http://www.shopfloortalk.com/forums/showthread.php?t=4592)for my air compressor

Digr I like that! Did you use "unistrut" for the "rails"?

digr
11-24-2013, 05:44 PM
Digr I like that! Did you use "unistrut" for the "rails"?
Yes thats what it was

Edwin Dirnbeck
11-24-2013, 06:13 PM
Here is a you tube video of my spring loaded idler that I buit in 1975 .I use this compressor almost daily. Also shown is a cumualative timer .I allways leave the compressor pluged in and once years ago I blew an airline when I was gone all day .When I came home the compressor had been running for hours and was quite warm and stinky. Now after the compressor has run for a total of 1 hour,it shuts off until I press the red reset button and its good to go for another hour.
http://youtu.be/TCvpbKdqtLg

digr
11-24-2013, 08:03 PM
I put a red light bulb above mine so if the compressor is on the light is on. It has saved many trips back out to the shop at nite.

A.K. Boomer
11-25-2013, 08:33 AM
I put a red light bulb above mine so if the compressor is on the light is on. It has saved many trips back out to the shop at nite.

I have a illuminated switch above the compressor for that purpose - it's a small little red led that shows when the switch to the compressor is on so i can tell at a glance across the room...

If a line totally blows it's not always a death sentence for the compressor as it will just be free running against little resistance - however, if it's electric motor or compressor cooling fans are not up to the task it still could be.

your worst case would be a slow leak, but fast enough to never let the compressor catch up keeping it at maximum resistance - now your talking cook time... and if you happen to have forgotten while on vacation quite an electric bill when you get back home.