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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › Hatori header blows out O-rings, why?
01-16-2009 04:29 PM  9 years agoPost 1
MaxAdventure

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Northern CO

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Does anyone have this problem?
I have an OS 70 with an SB14 and I had trouble with the single point mount that the pipe would separate from the manifold.(similar to: http://www.ronlund.com/Merchant2/me...ust_Accessories
)
as seen here:

I now have a loop at the front (zip tie w/silicone tube) in addition to the mount toward the rear and it's staying on very nicely. However, about every two to three flights, I still blow out the first (closest to the engine) O-ring. Seems to rip along it's circumference and spit out at the bottom.

I've been told I need to put them in dry, would oiling the O-ring to get the assembly together allow them to blow out? are they getting too hot? Am I assembling them wrong?

Maybe I should buy 50 packs and consider them a consumable like nitro and hot dogs...

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01-16-2009 05:05 PM  9 years agoPost 2
cdrking

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Seattle

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IMO you can't put them in dry, you just end up pinching them while putting them on. For years I just purchase a pack of 25 from McMaster Carr, they are about 7 or 8 bucks for 25.

I just use spit to put them on and carefully push the pipe on evenly so it doesn't cut or pinch the o-ring. The only time I've had them break is when I pinch or cut them while putting the pipe on.

Jeff

To hover is divine, the alternative is rather PLANE.

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01-16-2009 05:08 PM  9 years agoPost 3
cdrking

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Seattle

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Also I have used that mount years ago and really didn't have great luck keeping the set screw tight. I finally just used red loctite and it stayed fairly good.

Jeff

To hover is divine, the alternative is rather PLANE.

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01-16-2009 06:10 PM  9 years agoPost 4
Dr.Ben

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Richmond, VA, USA

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I've been using Hatori (or Funtec which uses them as well) mufflers constantly for a decade. Hundreds of gallons of fuel. In that time, I've literally replaced less than dozen combined beyond the ones that came with the muffler when new, and I only did those as maintenance and never due to failure or excessive wear.

It does take finesse to install the canister onto the header. I use a small amount of silicone grease and carefully rock/rotate the canister into place. It's EASY to get a pucker of the oring out from around the canister if you aren't careful, so you have to go slowly and check your work. With lube in place, the oring will generally survive a pucker, but it's toast if you try to run it that way.

The main thing that causes the orings to fail is failure to mount the pipe in a stable mount which DOES NOT side or otherwise preload the canister AT ALL when all is tight. You have to watch CLOSELY when whatever clamp you have is tightened. The canister should not move at all from its resting position. If it does, you're side loading the orings, and they'll fail. The pictured mount sucks rocks. It's prone to loosening b/c the rod is steel in the latest versions and the clamp is ali. It easily sideloads the canister and provide minimal stability. There are other options out there, and all are better than the !@#$ clamp.

Ben Minor

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01-16-2009 09:19 PM  9 years agoPost 5
Four Stroker

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Atlanta

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Ben is absolutely correct - no preload. Ben is also correct - don't trash them during the install. When I said dry in the other thread, I meant no grease or oil. Spit as above or failing that a little dishwashing soap in water. The Hatori clamp is two point and you can put one up front if you so desire. If you must use grease, make sure it is O-ring compatible at muffler temps. And finally, they are really cheap - buy a bag of 25.

P.S. Linen filled phenolic standoffs work much better than aluminum.

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01-16-2009 10:02 PM  9 years agoPost 6
MaxAdventure

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Northern CO

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Ben/Fourstroker - Thanks for the replies and suggestions. I don't mind some experimenting, but I'd like to know I'm going down the right path at the very least.
The pictured mount sucks rocks. It's prone to loosening b/c the rod is steel in the latest versions and the clamp is ali. It easily sideloads the canister and provide minimal stability. There are other options out there, and all are better than the !@#$ clamp.
Fourstroker, was the above quote from Ben your point when suggesting:
http://www.ks-j.net/kands/E_KS/sub_windw.cgi?767
http://www.ks-j.net/kands/E_KS/sub_windw.cgi?691

If my clamp is inadequate, I'm willing to get a new one. My thought is put a good one where my current mount is, move that mount up front for added stability.

It appears I could get a more solid mount with the #767. Does someone have a suggestion? My Google skills seem to be lacking today.

I'm guessing I've had issues with both the clamp side-loading as well as pinching the o-rings on install.

thanks again!

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01-16-2009 10:32 PM  9 years agoPost 7
Four Stroker

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Atlanta

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Dr. Ben;

Do you have some pictures of a successful mount of this type of muffler ? What mount and where can he get it ?

MaxAdventure;

I can hear hundreds of people laughing out loud reading this thread. Hatori has gone through many incarnations of pipe mounts and none of them are really satisfactory. All of the old guys and all of the F3C guys have been where you are today. The best bet is to find someone in your area whose muffler does not fall off and get some help. I'm sure the single point mounts were intended to stabilize the muffler and not to hold it in place. Many people have used these successfully but a two point mount is obviously more stable. Finding a place to attach the standoffs may be a problem. If the other side of the mount is hanging in the air it's not much help. The F3A guys continuously fight the same problem with the Hatori #821 and #824 pipes. The worst idea ever was flex-pipes.

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01-16-2009 10:41 PM  9 years agoPost 8
MaxAdventure

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Northern CO

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Fourstroker- thanks again!
All of the old guys and all of the F3C guys have been where you are today.
Honestly, this makes me feel a lot better. Worried I was just being dense. Sounds like I'll get the big bag of rings and try some ideas I have until I can learn to assemble the muffler and have it mounted well and they don't spit out.

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01-17-2009 01:01 AM  9 years agoPost 9
Dr.Ben

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Richmond, VA, USA

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I'll do some checking this weekend for a decent clamp. Honestly, I used the stock Hatori clamps and standoffs with no problems, but I EXHAUSTIVELY (no pun) shimmed the set it up (stand offs and clamps)to make sure the whole affair tightened up without preload. If that is done, most anything will work.

I still detest the clamp in the pic, though.....<G>.

Ben

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01-17-2009 01:09 AM  9 years agoPost 10
cdrking

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Seattle

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Here's one that I used years ago on a Fury Extreme. He doesn't make them anymore though. gjestico clamp

Another one that has been used. Eric Stolz Clamp

To hover is divine, the alternative is rather PLANE.

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01-17-2009 03:25 AM  9 years agoPost 11
Four Stroker

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Atlanta

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Note that the very beefy gjestico clamp stud is backed by a cross member that goes to the other side frame. You should definitely do this with your plastic side frames if you can find a good location.

I don' see any adjustment on the Eric Stolz clamp. But it's beefy.

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02-03-2009 02:40 PM  9 years agoPost 12
MaxAdventure

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Northern CO

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Update; I picked up a bag of silicone O-rings, hoping they were less easily damaged as well as better heat tolerance. They are the same durometer, so I don't know if they really are able to deal with assembly better. I'm trying to ensure I don't have the side loading described, because I think that's probably my main source of issue. I'll continue to try and source a better clamp, meanwhile I'll see if I can't get my current set up more solid. Thanks again!

I'll post back after I get some flying windows to test. I suspect it will take me a couple tries to get this clamp right.

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02-03-2009 05:00 PM  9 years agoPost 13
Dr.Ben

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If they're silicone and not Viton, then you're not going to see the desired longevity. Viton is far more durable in this admittedly hostile environment.

Ben Minor

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02-04-2009 06:36 AM  9 years agoPost 14
mchammer

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California,USA

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I was going through them as well.I tried the ones mentioned erlier from mcmaster they hold up alot better than the hatori ones and alot less expensive.

Peace Through Superior Firepower!!!

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02-04-2009 02:30 PM  9 years agoPost 15
MaxAdventure

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Northern CO

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I've taken Friday off to fly, so we'll see how they perform.

I primarily picked silicone due to the price, as I expect the weakness is me, in making sure I have a solid connection and no side loading as recommended. I expect to blow more out, until I get this figured. If they even last 5-10 flights, I'm way ahead of where I was. If Hatori used them originally, I would think I could get more than that - time will tell. Keep in mind it's winter in Co. They might be going from 15F to 200F in a few seconds when I start up.

-Viton has better chemical resistance
-Viton has better tensile strength

-Silicone has better temperature stability
-Silicone was nearly half the price, from McMastercar (~$7.50US for 50)

So far, silicone has seems to be 'slicker' when I lubricate with isopropyl for assembly (I just can't get myself to spit on my heli)

I know it wasn't probably the best material, however I feel I am the weak link in this chain and wanted to afford myself twice as many 'learning opportunities'. Besides, someone said 'try it, and let us know' - seemed like a fun idea.

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02-04-2009 06:30 PM  9 years agoPost 16
Four Stroker

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Atlanta

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Unfortunately the specifications for O-ring materials tells you essentially nothing about how they will perform in an exhaust system. In four strokes, silicone will self-destruct in 1 flight. Viton will hold up for a long time if it is not close to the engine - the exhaust has some time to cool - expansion or distance. Teflon is amazing and will stand up to exhaust that is twice it's rated temp. even though it turns brown.

The Viton will outlast silicone in your application 10 to 1. In your muffler mount the rigidity of the Viton is what holds your muffler on. I believe your muffler was originally sold with orange silicone O-rings - and it spit them out.

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02-04-2009 09:51 PM  9 years agoPost 17
MaxAdventure

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Northern CO

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In your muffler mount the rigidity of the Viton is what holds your muffler on.
I'm feeling pretty ignorant in general about this topic, but wouldn't the durometer of the material dictate the rigidity? The viton and the silicone 0-rings had the same rating.

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02-04-2009 10:47 PM  9 years agoPost 18
Four Stroker

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Atlanta

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You are correct. Durometer is Durometer. At what temp. is the durometer measured ? The specs. don't tell the whole tale. When the material starts to decompose, what does it turn into ? This discussion reminds me of ball bearings and Hitec servos.

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02-11-2009 07:25 AM  9 years agoPost 19
FlytilyaDrop

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Playboy mansion

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I only use the MA 90 muffler mount due to its larger MM bolts used, and I mount the stud on the lower part of the frame on the two lower holes on the fury.

I use red loctite, and I put "most important Teflon tape around the muffler where the clamp goes around, this acts as a shock absorber, in return little vibration to frame of heli.

I am now almost 2 gal on each muffler and still have same o-rings.

I use the o-rings MA sells, when I tighten the setup, I do this in the following.

stud mounted on heli use big washers, red loctite,
rape Teflon around muffler where clamp goes, just enough to act as a shock absorber to clamp..
I put muffler on over o'rings twisting back and forth using little lube, I then pre fit all bolts and sight down the muffler to see a square fit on o-rings, slightly tighten bolts and continue to square out muffler on o-rings, I make sure their is no preload in any way.
then I tighten up the muffler clamp first fully, then check again preload, when I tighten up the clamp to stud, the stud in the hole of the clamp is rested against the side where the set screw pushes it to when tighten up.

so the last screw to be tighten up is the set screw for the clamp to stud off heli.

I have no preload in any way but I do have just a very slight maybe 1 to 2 mm of where the muffler in the rear is closer to heli body than the front of the muffler, I make sure this is done without pre-load, this acts as a leverage to keep the muffler from blowing off.

In a very slight way you could say I am forcing the muffler to stay on where the o-rings are by using the stud and clamp to make that force, maybe a slight pre-load, but not much.

So far its been the best for me, and once I use red loctite I dont like to mess with it for a long time, and now I dont.

The Teflon tape I feel could be a huge factor in my success.
Plus it keeps the muffler nice looking where the clamp scares most mufflers.

This hobby sucks, when your not flying.

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03-29-2009 03:44 PM  9 years agoPost 20
MaxAdventure

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Northern CO

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Thanks for all the suggestions, current report:

The silicone are holding up better than the original O-rings. I'm getting several flights, but still running into some issues. I'm still looking for a better mount/double mount but at least they're not blowing out every time. Last problem I think was due to ground impact from a lost linkage, not so much my muffler o-rings :-o

I've shifted back this spring to flying this model primarily and I expect I'll get it worked out soon with all the great advice! To be clear, the pipe was picked up used with a supply of o rings, so I really don't know what they were for sure that I was blowing out every flight.

thanks again!

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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › Hatori header blows out O-rings, why?
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