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Control Line Forum => Engines for Control Line Aircraft => Topic started by: jerryCashman on April 03, 2019, 09:13:47 PM



Title: Method for holding muffler for OS Pet III
Post by: jerryCashman on April 03, 2019, 09:13:47 PM
Hi team,

I've dug an old OS Pet (I think, a Mk III) from the depths and have cleaned it up and it's a great little runner and I'm looking forward to building a little C/L stunt/trainer to get my hands back in after xx years...

The only bit that's missing is the spring gadget that used to hold the muffler on to the head...

Other than fashioning a strip of brass to fit - does anyone have any other suggestions on how to safely fix the muffler on?

cheers. Jerry in Canberra.

(https://www.osengines.com/history/osm640/osm-1971-pet-iii-099.jpg)


Title: Re: Method for holding muffler for OS Pet III
Post by: strat-o on April 04, 2019, 02:13:24 PM
Winding your own spring might seem like a tedious proposition, but I think any alternative would have it's difficulties.  Given a long piece of suitable wire, access to a vice and a steel pin or nail to wrap against as a mandrel should land you in the ball park.  Also a pair of pliers will allow you to pull the wire to a good tension as you wrap.

Marlin


Title: Re: Method for holding muffler for OS Pet III
Post by: NormF on April 04, 2019, 04:27:48 PM
How about using two pieces of wire, tension it by twisting, ala safety wire. Run the wire in some silicone fuel line to add some vibration resistance and also protect the finish of the engine.

Norm


Title: Re: Method for holding muffler for OS Pet III
Post by: jerryCashman on April 04, 2019, 06:08:30 PM
Thanks guys - Norm, I think you are on a winner there with the twisted wire and I do like the fuel-tube cushioning - I'll give it a go! Thanks :-)


Title: Re: Method for holding muffler for OS Pet III
Post by: ffkiwi on June 09, 2019, 04:54:13 AM
As another suggestion-go to your local $2 shop-and buy the smallest pack of curtain wire you can (or bludge a few inches off a mate...!)-then get the smallest screw eye you can find that will screw tightly into the curtain wire coil and use these to hook over the two screws on the muffler where the original spring clip fitted. You will probably: a) require some trial and error to get the tension right-adjust the length of the curtain wire by clipping small bits off with a diagonal cutter, and
 b)  you may have to squeeze the screw eye hooks a bit smaller to get them to fit the muffler screws securely (depending how small a size screw eye you can get locally)

An alternative approach-try a tension spring-these usually have an eye at each end that will fit over the muffler screws...it will be a case of finding one of a suitable length to stretch round the motor when extended. You can find these sorts of springs at Bunnings, Repco and Super Cheap Auto...

 ChrisM
 'ffkiwi'

 PS  Be aware that the OS 701 muffler was sold with two different springs-one for the Pet-III, one for the Max-6....both had the same form, but different lengths-there are probably quite a lot of the Max-6 springs floating about in people's junk boxes-as there weren't that many '6's sold compared to Pet-III's....the Max-6 spring could be extended with say a fishing snap swivel clip to fit the Pet-III....