Drive belt tensioner

[Old Man]

I am in the process of construction of a Listeroid genset and want to drive the generator with a Serpentine belt. All the posts I read slide the generator to tighten the belt. Has any one tried to use a serpintine belt tensioner from a pickup or auto? I would appreciate any thoughts on the subject, thank you,
Old Man

[t19]

its called the KISS principal

the tensioner is an extra part  to wear and break,

[BigGreen]

The plus side of a tensioner is more belt to pulley contact for less slippage and less tension on gen bearing. I have a tendency to over tighten my belt.
The negative is another thing to break and a slightly added load due to friction.
I plan on adding one if/when I upgrade.

[SteveU.]

Hi ALL
For an industrial dual force 20 degree tonsioner try looking at  www.Grainnger.com  or catalog #399 page177.
"Elastomeric Tensioners"  #1L834 for 1&2" belts and #1L835 for 2,3,&4" belts.
I"ve replaced too many automotive tensioners (on automotive) due to plastic bushed pivot shaft wear to believe most automotives would hold up any reasonable time. What is Jens using??

SteveU.

[SteveU.]

Hello Again,
The Auto manufacturers dicovered the hard way by bearing failures in previously known good designed alternators and water pumps that the "new" polygroove belts have NO shock loading dampening. That was why the smart ones found they had to add a spring armed dampener. They are allmost always applied on the slack side.
You are probaly right that in this application putting one on the tensioned/pulled side might be better. I worry however that any tensioning arm piviot will wear out within hours if its going to be cycled 300 plus times a minute. Thats primarily what kills them on cars/trucks due to an unevenly worn belt or pulley crap build up (never use gooey belt dressing on a serp. belt/pulley!!!) causing the tension arm to be constantly jiggling. Look under your hood and the tensioner only loads up and unlaods with major engine speed changes and alternator/PS load changes.

All just my own 40 year professional auto/light truck experiences.
SteveU. 

[SHIPCHIEF]

Right now, my 25/2 ST12 squeeks the belt on engine firing pulses when running at full load. The belt seems tight enough at rest, but the slack side flaps around alarmingly when running at full load.
I think a spring loaded idler pulley could take up the firing pulse.
Assuming the tension side of the belt is off the top of the gen pulley to the top of the engine flywheel pulley:
Mount an idler pulley on top of the belt, pulling it down a couple of inches by spring. Every firing pulse would lift it (trying to straighten out the belt). During the coasting cycle, the spring would pull the belt back down. It would hardly move @ no electric load, but move more @ high Kw?
A tension pulley would also be required on the slack (lower) belt to keep it from flapping, but have a lesser spring.
This is a torsional damper between the prime mover and the load, externally adjustable. The spring would store and return the firing pulse energy as efficiently as anything a DIYer could create.
The parts are readily available from the wrecked pickup truck that you just salvaged the serpentine belt from....But the cyclic load would require lubrication on the tensioner shafts.
In the event of a damper failure, the original straight serp belt system could be used with the original shorter belt.
Scott E

[compig]

The answer to belt slippage in this application , if it happens , is more belts  !!  Our application is similar to belt drive industrial compressors , when more power transfer is required these rigs use more belts. This is due to the requirement for long term reliability as mentioned before in this thread. 

[Jim Mc]

Not in my case either.  The only answer is more tension and increased wrap angle on the flywheel (which is accomplished by minimizing the engine-to-generator spacing).  The number of belts doesn't affect the belt slip issue.  More belts will improve belt life, but that's not been an issue as far as I know.

[SHIPCHIEF]

Slippage occurs on the FLYWHEEL?
I couldn't decide if it was the gen pulley, or the engine flywheel.
I know the serp belt pulley on the gen has all the proper grooves, but it does have less lineal contact area than the flywheel...
Scott E

[Jim Mc]

Yeah, definitely on the flywheel in my case, too.  I can hear the squeaks coming from the flywheel.  I think the V groves in the generator pulley make it pretty much slip-free.  Back to the original question, though...  A tensioner might be a good thing even if it only acts as an idler pulley, since you could position it to increase the wrap angle of the belt around the flywheel.  IOW, the actual tensioner function may not be needed as much as more wrap angle...

[MacGyver]

I don't seem to have any slipping or chirping problems...

Do you folks clean the paint off of the flywheel where you belt rides?

Maybe the indian paint is just slippery...  ?

My flywheel has been cleaned of paint where the belt rides and I don't have any noticeable slippage.

[mobile_bob]

why not run the back side of the belt on the flywheel?

you would have probably 2-3 times the contact area used in this manner

it would require two idlers, one could easily be something useful like an automotive alternator
or a water pump to move the coolant heat somewhere useful?

of course it would require a longer belt, but failing cutting grooves in the flywheel
(something else a crafty guy could do with the engine running) it is the only way i can see of
getting substantially more belt contact.

bob g

[oliver90owner]

Jens,

Isn't the other alternative to make your supporting frame rigid and not have your engine 'rocking' on a 'perch' across the main frame rails??

Regards, RAB

[mobile_bob]

Jens:

i would say you are probably right, except...

if you look at the area on the top of the tooth of the belt it generally can be deformed/distort/rollover when
presented with a shock and the rubber compound on the top of the tooth generally is not as sticky as the
rubber on the back side of the belt (usually there is some cording in the tooth and none on the surface of the back)

take a car that has 1500lbs on the rear axle, use standard tread tires with grooves say 8 inches wide
and rev her up and drop the clutch,, you might smoke the tires, at least a chirp

now jack the same car up and put on a set of slicks, no grooves 8 inches wide, same 1500lbs
rev her up and drop the clutch, you likely won't get a chirp and wont get any smoke unless you have more hp

weight didn't change=belt tension doesn't change either

i mean i follow your physic's but i don't think the coefficient of friction is the same for the back of the belt as it is for the
tips of the teeth (which were never designed or compounded for a high coefficient of friction to start with).

make sense?

bob g

[mobile_bob]

just one more point, the back of the serp belt is compounded to have a high coefficient of friction and is intended to
be able to drive accy's such as waterpumps (automotive serp belts at least)

i bet if you run the belts backside on a clean flywheel it would never chirp/slip or give you any problems and do it with less
tension than needed the way folks are running them now.

ever try to push a dry squeegy across a dry floor?

bob g