Gas Engines Questions or comments about gas engines can be posted here

O.S. GT33 Muffler

Reply
Old 05-11-2012, 05:13 PM
  #1
JoeMamma
Thread Starter
 
JoeMamma's Avatar
 
Join Date: Nov 2002
Location: Lenox Township, Michigan
Posts: 818
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default O.S. GT33 Muffler

Hi Bax,

My muffler came loose again on my new GT33. This is getting very annoying.

A gasket is used between the muffler and the cylinder head. The supplied muffler bolts are 5mm x 45mm. 5mm flat washers were also supplied. I believe the supplied flat washers may be the problem.

In the back of my GT33 manual on page 26, O.S. is referring to a set of 5mm lock washers, O.S. part number 55500004.

Tower Hobbies has them in stock, but they are pricey at $13.49 for 10 sets of 20 washers.

When I talked to Tower, and because of the high price, I asked them if the 55500004 washers were similar to Nord-Lock (brand) washers. They didn’t know. I also asked if somebody could go into the warehouse and open a package to see if these washers are similar to Nord-Locks. Then I heard the “we can’t go into the warehouse and open up packages” response.......I don’t think they like me anymore.[X(]

Nord-Lock's are sold in sets and use a principal of locking one washer against the other.

I don’t mine paying the $13.49 if these are similar to the Nord-Locks. Could you find out ?

Any other tricks you know of to keep my muffler bolts tight ? As it is, when the muffler bolts come loose, the threads in the cylinder head are getting beat to death.

Thanks,
Joe M.
JoeMamma is offline  
Reply With Quote
Old 05-11-2012, 07:49 PM
  #2
skypete
 
Join Date: Jan 2007
Location: Rockingham, AUSTRALIA
Posts: 5
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: O.S. GT33 Muffler

I had the same issue as you - gasket blew out and muffler came loose. I've used Permatex Ultra Copper instead of the supplied gasket, thread lock on the bolts done up really tight. No problem since (about 15 flights since I fixed it). Re the washers I reckon they're Nord-locs. Locally I couldn't get 5mm ones so I bit the bullet and ordered from Tower Hobbies (recently, they haven't arrived yet). I figure I'll use them on the next model anyway even though they're pricey. I would have used them on my muffler too if I had them at the time.

This is a common problem with mufflers and gaskets.

Pete
skypete is offline  
Reply With Quote
Old 05-12-2012, 01:01 PM
  #3
JoeMamma
Thread Starter
 
JoeMamma's Avatar
 
Join Date: Nov 2002
Location: Lenox Township, Michigan
Posts: 818
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: O.S. GT33 Muffler


Quote:
ORIGINAL: skypete

I had the same issue as you - gasket blew out and muffler came loose. I've used Permatex Ultra Copper instead of the supplied gasket, thread lock on the bolts done up really tight. No problem since (about 15 flights since I fixed it). Re the washers I reckon they're Nord-locs. Locally I couldn't get 5mm ones so I bit the bullet and ordered from Tower Hobbies (recently, they haven't arrived yet). I figure I'll use them on the next model anyway even though they're pricey. I would have used them on my muffler too if I had them at the time.

This is a common problem with mufflers and gaskets.

Pete
Thanks Pete,

I've tried it with and without the gasket. It doesn't seem to matter as the bolts still come loose.

I also tried the Ultra Copper on the second flight. The bolts still came loose on about flight number eight.

As I was landing yesterday, I could hear a loud rattling. Just as the wheels hit the ground, a few of us saw the muffler skipping down the runway. Good thing the muffler landed on the runway as that bugger is a whopping $84.99 (U.S.).[X(] Sure don't want to loose it over the woods ![:@]

Also, the aluminum muffler mating surface on the cylinder head got beat up pretty bad by the muffler. This probably happened from vibration just as the muffler bolts started to loosen up. I sure hope this "boogered up" mating surface will still seal OK.

Another problem is the threads in the cylinder head for the muffler mounting bolts got beat up and are a little sloppy. They aren't terrible, so I'm hoping I can repair them with a little JB Weld. If the JB Weld doesn't work I may need to add a 5mm Heli-Coil into the threads.

I'm getting ready to order a couple of gaskets, lockwashers and 5mm x 45mm hex-headed bolts.

I also have a roll of .020" stainless safety wire. I plan on using the safety wire to anchor and attach the muffler to either the plane or the engine. I'm also going to drill the heads of the new bolts for my safety wire.

I'm also looking at fabricating an aluminum support bracket. One end of this bracket could be attached near the end of the tailpipe. The other end could be attached to the engine. In my opinion, this bracket can only help the situation.

The engine is under warranty, so I could just send the engine/muffler assembly back to Tower Hobby and ask for a replacement, but I'm sure this same problem will probably happen on a replacement engine. I'm hoping I can get my repairs to work.

Joe M.
JoeMamma is offline  
Reply With Quote
Old 05-12-2012, 03:30 PM
  #4
skypete
 
Join Date: Jan 2007
Location: Rockingham, AUSTRALIA
Posts: 5
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: O.S. GT33 Muffler

Hi Joe

What you've proposed doing sounds like a lot of work. What about those Nord-loc washers from Tower? If you know about Nord-loc (it seems you do) they're made for just the problem you have. BTW when I ordered the OS stand-offs for my GT33 engine they came with 4 pair of those very washers. Pity OS didn't supply a couple of pair with the muffler when we bought the engine — it would save a lot of grief.

Pete
skypete is offline  
Reply With Quote
Old 05-12-2012, 04:20 PM
  #5
JoeMamma
Thread Starter
 
JoeMamma's Avatar
 
Join Date: Nov 2002
Location: Lenox Township, Michigan
Posts: 818
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: O.S. GT33 Muffler

Pete,

If I would have designed those muffler bolts, I first would have increased the size up to 6mm. I would then use 6mm grade-8 studs with threads at both ends and a shoulder in the mid-section. This shoulder would fit snugly into the muffler mounting holes.

The stud would be designed to bottom out and be tightened into the cylinder head.

Top it off with a set of Nord-Lock washers and then a 6mm crimp nut (an oval shaped nut that has been slightly crushed). A crimp nut will absoluteley never unscrew due to vibration. The only problem with crimp nuts is they can't be used more than a few times. They tend to tear up threads.

Wherever I use nuts anywhere on my planes they are always Nylon-insert lock nuts, but they don't work very well on exhaust parts as the Nylon is prone to melting.

Joe M.
JoeMamma is offline  
Reply With Quote
Old 05-17-2012, 06:40 AM
  #6
MTK
 
Join Date: May 2004
Location: Whippany, NJ
Posts: 5,386
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: O.S. GT33 Muffler


Quote:
ORIGINAL: JoeMamma
Thanks Pete,

I've tried it with and without the gasket. It doesn't seem to matter as the bolts still come loose.

I also tried the Ultra Copper on the second flight. The bolts still came loose on about flight number eight.

As I was landing yesterday, I could hear a loud rattling. Just as the wheels hit the ground, a few of us saw the muffler skipping down the runway. Good thing the muffler landed on the runway as that bugger is a whopping $84.99 (U.S.).[X(] Sure don't want to loose it over the woods ![:@]

Also, the aluminum muffler mating surface on the cylinder head got beat up pretty bad by the muffler. This probably happened from vibration just as the muffler bolts started to loosen up. I sure hope this ''boogered up'' mating surface will still seal OK.

Another problem is the threads in the cylinder head for the muffler mounting bolts got beat up and are a little sloppy. They aren't terrible, so I'm hoping I can repair them with a little JB Weld. If the JB Weld doesn't work I may need to add a 5mm Heli-Coil into the threads.

I'm getting ready to order a couple of gaskets, lockwashers and 5mm x 45mm hex-headed bolts.

I also have a roll of .020'' stainless safety wire. I plan on using the safety wire to anchor and attach the muffler to either the plane or the engine. I'm also going to drill the heads of the new bolts for my safety wire.

I'm also looking at fabricating an aluminum support bracket. One end of this bracket could be attached near the end of the tailpipe. The other end could be attached to the engine. In my opinion, this bracket can only help the situation.

The engine is under warranty, so I could just send the engine/muffler assembly back to Tower Hobby and ask for a replacement, but I'm sure this same problem will probably happen on a replacement engine. I'm hoping I can get my repairs to work.

Joe M.
Joe,

My OS33GT muffler is for sale. It is brand new, never used, 65$ delivered to your door. Please PM me if intersted.

Let me suggest that you first reface the muffler flange. Put a piece of wet-or-dry paper on a piece of glass and run the muffler flange on that. You should get all the high spots removed. Then definitely use Ultra Copper without a gasket. Also use Ul;tra Copper on the bolts and torque them tight. Let this cure for a day before using. You may use Nord-Locs under the bolts heads but isn't always necessary; it is added insurance.
MTK is offline  
Reply With Quote
Old 05-17-2012, 03:33 PM
  #7
JoeMamma
Thread Starter
 
JoeMamma's Avatar
 
Join Date: Nov 2002
Location: Lenox Township, Michigan
Posts: 818
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: O.S. GT33 Muffler

[/quote]
Joe,

My OS33GT muffler is for sale. It is brand new, never used, 65$ delivered to your door. Please PM me if intersted.

Let me suggest that you first reface the muffler flange. Put a piece of wet-or-dry paper on a piece of glass and run the muffler flange on that. You should get all the high spots removed. Then definitely use Ultra Copper without a gasket. Also use Ul;tra Copper on the bolts and torque them tight. Let this cure for a day before using. You may use Nord-Locs under the bolts heads but isn't always necessary; it is added insurance.
[/quote]

Hi Matt,

Thanks for the offer, but as I mentioned I ALMOST lost the muffler. As soon as I get my new bolts and washers I'm going to use stainless safety wire on the muffler.

Hey, it may come loose again, but at least I won't loose the muffler.

Joe M.
JoeMamma is offline  
Reply With Quote
Old 05-17-2012, 05:45 PM
  #8
Scota4570
 
Join Date: Jan 2009
Location: Salinas, CA
Posts: 841
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: O.S. GT33 Muffler

Clean everything and degrease. Glue everything in place with permatex. Mating surfaces, threads........everything.
Scota4570 is offline  
Reply With Quote
Reply


Thread Tools
Search this Thread
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -8. The time now is 05:13 AM.