Smarty wrote: ...
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Agreed it is simply a noise isolation and damper as noted.
W/O pictures hard to tell; my inclination from description and reading w/o the hands-on would be to use the radiator hose type solution for the connection and look at a flexible mounting for the air cleaner -- think the exhaust system type hangers or similar -- if need more movement than the hose itself would allow.
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On 7/22/2010 10:08 AM WW spake thus:
Nitrile is the word you're looking for here.
Mebbe coat this rubber ditty in some kind of silicone caulk (they make a Silicone III?) or some flexible epoxy? There's even a kind dip for plier handles that gives a very sturdy flexible-ish coating. Proly some other stuff. Pliobond adhesive?
Does this bellows thing wear in one place, or does it fail anywhere? This could affect how you choose to coat/seal this thing.
Another possibility is make some kind of adapter, and just use a tougher flexible tubing.
I spent most of today searching out, buying, and trying the 'loop of hose' method, only to learn that the bending radius for hose of this large dimension creates a loop which just will not fit in the generator cabinet and also will not clear the very limited adjacent carburettor linkages, governor calibration screw, and assorted other parts. The stronger radiator hose with internal helical wire is sturdy but very difficult to bend to a tight loop. I did not buy a piece of silicone tube, but I did play with some and it is also quite stiff due to the thick walls, preventing a small radius bend.
I have ordered a couple hump connectors and lined T-bolt clamps, and also have 3 more Generac bellows here which came from my parts supplier. I am going to experiment further to see what remaining options I have, including coating the bellows, installing the hump hose, or possibly relocating things slightly. I am quite certain that there is no way to significantly move the air cleaner assembly without serious re-design of the internal cabinet brackets, sheet-metal, and plastic housing, none of which I have any real desire to screw around with. Using the current placement of everything, I am down to either a strengthened bellows, a hump hose, or replacing the standard bellows every 9 months or so in the preventative maintenance cycle.
The failure of the 2 bellows are fairly similar, small holes not much bigger than a pin hole, developing on the moving engine / carburettor side of the connection (versus the air filter stationary side).
I would guess that the peak-to-peak vibration of the bellows creates maybe a 3/8" to 1/2" excursion in the worn area of the rubber at the engine rotation frequency (3600 RPM as I recall). The damn bellows has a wall thickness of no more than about 1/16th of an inch of rubber, and is far from being a "heavy duty" construction compared to the hoses and hump parts I see with 4mm thickness or more.
I will update as I learn more. Thanks again!
Rad hose is good. Fermco coupler, maybe.
From what I can figure, the hose doesn't have to be hose clamped down tightly. Perhaps some silicone inside the hose (silicone spray) and sand the fittings. Would allow the hose to slip a bit on the fittings.
Gordon Shumway posted for all of us...
I agree with this. The 'flex area" is too short. Perhaps clamps on each pipe end similar to a conduit clamp mounted to an adjustable automobile exhaust pipe clamp may help.
Another thought is the shrouds that are used around automotive shock absorbers.
Last thought is a plumbing "Fernco fitting". Might work the best...
Lousy design IMO.
Smarty posted for all of us...
See my other post but look at automotive CV joint boots.
If the carb is moving 1/2" is there a problem with the engine mounts? Maybe even flywheel out of balance, or a misfire? That sounds like an awful lot, a 4-cyl. or greater engine at 3600 RPM should not be moving that much IME. Probably hard on the coupling between engine and generator too.
nate
Some good ideas in all these posts, but may I suggest one more item to look at? If the failure is due to movement between the rigid mounted air cleaner and the engine intake, find the source of the excessive engine movement, for example old tired gushy motor mounts. Seems to me if the engine/intake movement is normal, then most any common automotive hose should last for years. Good luck.
Joe
The generator has a one cylinder, 14 HP engine. The overall excursions, as I 'guesstimated' in my prior comment, are maybe 3/8 to 1/2 inch peak to peak, which is basically oscillating about 3/16 to 1/4 inch in each direction. The vibration has been about the same from original installation to the present time, so I don't think that the motor mounts have worn appreciably. It is possible that the mounts may have a problem from the factory which I and the Generac technician who serviced the unit under warranty may not have noticed.
The bellows have about a half an inch of expansion and contraction space and would appear to be adequate to deal with the vibration in terms of lateral 'play'. There are no specs or other adjustments, calibrations, or measurements published for any of this.
Perhaps the one cylinder engine explains why there is more vibration taking place than you originally expected for a 4 cylinder design?
Joe,
I would love to pick the brains of the folks who designed this thing to better understand the part they chose. I can surmise that the bellows was selected to allow for a fair amount of vibration and movement between the carburettor mounted atop the vibrating engine and the nearby stationary air filter assembly. For reasons unknown to me, they chose not to hang the air filter immediately above the carburettor as was done in classical automotive designs for many years. This would have eliminated the need for a bellows and floating connection altogether.
I am entirely frustrated by the fact that no other Google references show up with other people having this same problem. I would imagine that a complaint or two, or perhaps many more would indicate that this is indeed a design flaw rather than my own unique predicament. It tends to give weight to the theory that something else is amiss, such as the motor mounts. I am just not sure how much motion is typical of a single cylinder engine, but I certainly do not recall seeing this much play in my lawn tractor, snow blower, etc.
The bellows is made of thin rubber, no more than maybe 3mm, and possibly thinner. It is extremely tempting to put a Fernco or other flexible hose in the place of the bellows, but I do share the concern that I am now transmitting much more vibration rather than dissipating it.
I am going to call Generac tomorrow (again) and also call a local "Master" Generac service center and see if I can glean any more information.
I have posted a couple photos to show the inside of the Generac.
The first photo shows the overall internal layout with the bellows highlighted by a white ellipse. The engine and carburettor are to the left, and the enclosed air filter compartment is to the right.
The second photo is an enlarged view of the bellows area.
I did not post these earlier, since they really do not show a great deal about the specific bellows problem area. They do reveal how tight and space-constrained the area of the Generac is on the inside where the defective part is situated..
Ok... Some questions here...
Your generator is a little baby one compared to the 8 cylinder cat diesel generator sets I used to help the electrician maintain at the place I used to work...
(1.) How many hours of run-time do you experience between failures of this particular part... Parts and service on generator sets are measured in hours of running time rather than months or years...
(2.) What is the recommended service interval for that particular part in hours? You stated that you had installed the generator after you experienced a storm resulting in two weeks without power...
You haven't described how often the generator performs a "self-test" and runs while switching the emergency loads to run from the generator...
(3.) If this part is causing failures for your gen set why not replace it on a periodic basis even though it is not yet consumed? It is a $5 part to ensure that back up power is available... I have seen thousands of dollars worth of parts replaced annually on two huge cat diesel gen sets to maintain their operational status even though the parts have not yet failed...
Banks of batteries to start the generator were replaced every year in the fall to ensure fresh good batteries would be available to crank the generator during the coldest of winter days even though the battery pan was heated... These generators where integrated into the building automation computer system so they were monitored by many various sensors during their 20 minute exercise run time each week down to the sine waveform the generator was putting out on each phase and if some aspect was out of parameters the gen set could be examined and serviced to make sure it was running in top condition long before it failed...
This sounds like an interesting thing to read up on in the service manual for your gen set to see how often your failing part should be replaced...
Are you sure that there is not something unique to your generator's installation that is causing this part to fail? Animals or insects? Something environmental which could be weakening the rubber?
~~ Evan
I confused, which model Generac standby unit has a one cylinder engine and who manufacturers the engine. The reason I ask is that I've never seen a Generac automatic standby gen-set with a single cylinder engine built in the last 10 years. Back in the 1990's, I installed a number of
8kw Generac automatic standby systems that had the Vanguard V-twin Brigs&Stratton engine then in 1999 Generac developed their own V-twin for the home and RV gen-set market. The last Generac system I installed was several years ago and it had the big honkin Generac V-twin. Somebody has even built a chopper powered by one.TDD
Approximately 1 failure every 10 running hours.
Generac has very explicit service intervals for some items, such as spark plug, valve lash adjustment, etc. It makes no mention of this particular part regarding preventative maintenance / replacement.
Weekly for 13 minutes per week.
I could and I will, but since Generac never recommends it, and the Generac service technician who replaced the first one under warranty seemed very surprised that it had failed in less than a year, blaming it on "a faulty bellows rubber part which has been re-designed", I can only assume that this is NOT supposed to fail this way. It is also a PITA to replace and would be way better if it merely held up longer.
As a retired electrical engineer, I have read the owner's manual as well as the service manual cover to cover. This item is not covered.
A chemist friend of mine opined that a variety of synthetic rubber products are susceptible to airborne chemicals such as lawn pesticide spray, and can weaken as a result. A possible explanation, and one which prompts me to consider a silicone hump hose as a replacement. Also could justify the approach of applying a coating to the bellows by dipping it in some magic "goo" to coat the exposed surfaces. I consider this explanation to be a bit of a stretch, but not entirely sure.
Thanks Nate. My Generac is described at this link:
It is an extremely popular and highly rated unit. Home Depot and other places sold (literally) hundreds (possibly thousands) of these in the aftermath of the October ice storm which devastated the Northeast area I live in a few years ago.
This one cylinder model, at 14.5 HP, makes 7KW of electricity, plenty adequate for a smaller home.
You will see the reference to one cylinder in the link.
Smitty,
This certainly appears to be true, and may explain my problem entirely. The other nearby hose actually lies well above the bellows and clears it with no interference, but the bellows does not sit unloaded without stress as it should, and I need to take a closer look at it. Maybe the clamps they use are somehow deformed.
=?iso-8859-15?Q?Tekkie=AE?= wrote in news: snipped-for-privacy@news20.forteinc.com:
I wonder if the OP has written Generac to let them know about the repeated failure of the bellows-duct?
Maybe they would like the failed parts for analysis and could come up with a more durable part.
the CV boot idea sounds promising;a good idea. either CV or tie rod end boot.
In case you have trouble with the prior link I stated above, here is a shorter link to the same page:
Kohler made/makes a 15 hp single that is very well balanced and pressure lubed. MY Deere LT155 has one in it. Bought in 2000, serviced once a year (oil, filters) it runs like it did the day it was driven off the showroom floor. I could easily see a derivative of the Kohler Commander single in a standby generator. It would run very quietly though and that's one thing the OP said his didn't do. He also said it was a 7kw generator with an auto mains switch.
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