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  1. #1
    dasintex's Avatar
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    'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    Here's what I have and know, A DLE55 with a 'JTEC WRAP AROUND PITTS' Muffler on a TF Giant P-40; the Muffler features Long Exhaust Tubes, my thought was, the Vibration and shaking of the Engine will shake the Muffler to a point the Muffler will crack and fall apart, despite how solid the engine feels mounted on the Standoffs, the Engine still Vibrates, Flexes and Shakes, no more than normal and what would be expected, Firewall Flexing, etc,.

    A few Guys have stated their Wrap Around Pitts Mufflers have failed this way and they were using Jtec, in assuming that my Muffler does not come loose which some have stated has happened and probably contributed to the Muffler Cracks and Failure, I will be using Wire Lockable Bolts. Is using a Support Strap, mounted to the Muffler End Plate and secured between the Engine Mounting Bolts and Standoff; Overkill, Not Recommended, etc?

    JTEC does not recommend Support Straps and states that using one Voids the Warranty, besides voiding the Warranty what will it Hurt?

    Thanks.
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  2. #2

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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    I've seen this problem solved by using a better standoff system where long standoffs are needed, as opposed to using the popular aluminum ones. Like using hardwood square stock, boxed in on a couple sides, for example. I've seen others, with very good stand off boxes, still have the issue. If you know the muffler to have the issue, strap it.
    Chad

  3. #3

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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    Whenever possible, use a support strap, so vibrations won't ruin your muffler.
    Pe, (www.mvvs.nl), MVVS, MOKImotor, RCexl, MTW, Xoar, Mejzlik.
    Blessing in ignorance? There is sanctuary in analysis.

  4. #4

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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    Real simple ... Support is good. Support back to the engine assembly itself is best.

    Weight, moment lenghts(short like standard not such a problem) and frequency are the factors.
    Oops!

  5. #5
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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    I believe that JTECs stance is their muffler is very light, "very little mass", therefore a strap is not required. Interestingly enough I just purchased a new Slimeline wrap around style muffler for a DA50 and they have also eliminated the strap. I had a JTEC muffler basically disintegrate into two pieces on a DA50. I believe the contributing cause was long standoffs that had compressed into the plywood firewall at the mounting point. This created a lot of engine oscillation. Maybe a muffler strap would have saved the muffler, hard to say. I decided that a better solution is to mount the standoffs to an aluminmum plate first and then mount the plate to the firewall. Much more rigid setup and more surface area when mounting to the firewall. I also switched to an older Slimline muffler, one with a strap, because I felt the Slimline muffler was a better quality muffler. Just my opinion.

    I totally agree with kmeyers, pe reivers and arobatx, use a muffler strap. Be sure the muffler strap is connected to the engine, not the airframe.

  6. #6
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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    It does depend on the engine and airframe as to how much vibration there is. But with the wrap around Pitts mufflers with all that overhang, using a support bracket is a good idea in any case.

    Club Saito #722, Sig Kadet Brotherhood #80, GlowHead Brotherhood #14,
    AMA # 928076

  7. #7

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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    I got a used TF Gaint p47 and it was done like this.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  8. #8
    dasintex's Avatar
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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    The Support Strap should actually be on the other end of the Muffler, the muffler is already supported at the exhaust port, it needs support on the other end where it is not attached to anything; unless it does have a 2nd one on the othe side not shown in Picture.
    P-40 Brotherhood #3
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  9. #9

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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    First, I've never had a Jtec muffler fail. Second, you've got the engine moving around slightly on the end of those stand offs, so the muffler is moving around with it as well. Now, bolt the end of that muffler to something that's NOT moving, or maybe moving at a different frequency, and what have you created?

  10. #10

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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    The support of the image is recipe for disaster. The engine moves relative to the fuselage, This causes strain on the muffler through the strap.
    The proper way is to fit the strap to the other side of the muffler end, and stay it to the engine block mounting lug, so the complete unit is as rigid as possible before it is bolted to the firewall/standoffs.
    Pe, (www.mvvs.nl), MVVS, MOKImotor, RCexl, MTW, Xoar, Mejzlik.
    Blessing in ignorance? There is sanctuary in analysis.

  11. #11

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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    Can we get some pics of what's right

  12. #12

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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    The strap goes to the rear engine stay.

    Pe, (www.mvvs.nl), MVVS, MOKImotor, RCexl, MTW, Xoar, Mejzlik.
    Blessing in ignorance? There is sanctuary in analysis.

  13. #13
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    RE: 'TO USE' or 'NOT TO USE' a Support Strap/Bracket on a Wrap Around Pitts Muffler?

    Some support for the can is always a good idea and if using a solid strap, make sure you attach it to the engine mount itself instead of a place on the airframe. Otherwise, you will have a situation where the difference between the vibrations of the engines and the airframe actually increases the load on the muffler.
    Many muffler manufacturers leave out any attachment points on their mufflers. In those cases, a simple but effective method is to use a spring (curtain spring or similar), wrap it around the outboard end of the muffler can and attach to the engine box.


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