Budget built MiniMax 1100 Ultralight

Discussion in 'Hangar Flying' started by Little Scrapper, Mar 10, 2018.

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  1. Mar 26, 2018 #141

    lake_harley

    lake_harley

    lake_harley

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    FWIW...the prices posted for a couple different 277's that were mentioned sound like really attractive prices, especially if they include gearboxes. I don't know that much about Rotax gearboxes, but I think a "C" box would be overkill, larger and heavier than you'd want/need on a 277. The thing to start looking for NOW is an exhaust. I think they're harder to find than the engines! IMHO I think you'd want a muffler that has the tapered cone either going straight into the muffler, or the style that has about a 30 or 45 degree bend in it.

    This is turning into quite the "it takes a village" project! :gig:

    Lynn
     
  2. Mar 26, 2018 #142

    Chris In Marshfield

    Chris In Marshfield

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    I have two 4x8 tables at the cabin in Chetek that you're welcome to use as long as you like. Now getting them home is another story...
     
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  3. Mar 26, 2018 #143

    Little Scrapper

    Little Scrapper

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    I can TIG weld up any exhaust as long as I have a set of numbers to go from. I don't know much about 2 strokes but I do have some experience. If the exhaust isn't built correctly there's a high probability the engine won't run correctly, or even worse, ruin it.

    Does a 277 on a Minimax have a standard type exhaust?
     
  4. Mar 26, 2018 #144

    Little Scrapper

    Little Scrapper

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    I have a lead on some closet doors. Hollow I suspect so I may use those as a base on which I can glue or staple plywood on. I have a ton of 2 x 4's on hand for legs. They have lots of screws and nails in them so I'll need to put the kids to work on cleaning them up.
     
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  5. Mar 26, 2018 #145

    Chris In Marshfield

    Chris In Marshfield

    Chris In Marshfield

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    Now that you mention it, I do have a "portable" work table that I built a while back out of a door and some folding table legs. Also welcome to use it if you like. And that one's local.

    It's quite light and easy to move.
     
  6. Mar 26, 2018 #146

    TFF

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    Good hollow doors tend to be flatter than solid ones, unless they are the heavy fire proof kind. Come up with a scale and weigh the pieces and match them side to side, so there is a good lateral balance. Put heavy sides, of long pieces, forward or inboard. Try and keep the mass centered and towards the front.
     
  7. Mar 26, 2018 #147

    radfordc

    radfordc

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    Short answer is no. Here is some info: https://www.cps-parts.com/cps/pdf/Part48.pdf

    I've seen pictures of a Rotax muffler cut open and it is a complex system of chambers and baffles.
     
  8. Mar 27, 2018 #148

    lake_harley

    lake_harley

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    I agree, there's no "standard" exhaust/muffler used on a MiniMAX but the ones most commonly seen are the ones with a straight tapered cone ahead of the muffler, and others that the cone has about a 30 to 45 degree angle built in.

    Having cut a Rotax muffler open, I'll agree there is a maze of baffles, tubes and chambers. What I didn't see was what I expected and that was a reverse cone hidden inside like those that would be on a "tuned" 2-stroke high performance ski-doo or motorcycle exhaust. A true tuned 2-stroke exhaust will certainly produce more power, but typically in a low range of RPM. There's no doubt the Rotax exhaust/muffler was the result of a lot of design and testing, but I would think, given the application, that they were building it primarily with a broad power range in mind.

    Lynn
     
  9. Mar 27, 2018 #149

    Little Scrapper

    Little Scrapper

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    So with all these 277 MiniMaxes over the years nobody has standardized some type of exhaust the works well? Exhaust plays a role in EGT's , CHT's, RPM's, torque etc.

    In that link it appears length is given but not the chamber.
     
  10. Mar 27, 2018 #150

    pictsidhe

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    Build a decent table from cheap lumber and ply. It doesn't need to be flash, but it needs to be rigid. You can skip flat if you don't mind shimming stuff. But it has to be rigid. Have I said it needs to be rigid?
    For your project, I'd be tempted to build it in the yard and throw a tarp over the whole project to keep weather out.
     
  11. Mar 27, 2018 #151

    don january

    don january

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    And condensation in.:ponder:
     
  12. Mar 27, 2018 #152

    radfordc

    radfordc

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    The Rotax factory developed the correct mufflers for their engines....so I guess that is the standard. I recall that there have been some after market mufflers for Rotax's over the years but none of them seemed to be better than the stock ones.
     
  13. Mar 27, 2018 #153

    pictsidhe

    pictsidhe

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    It's generally pretty difficult to better a factory muffler. It may be possible to reshape a factory muffler to better fit your plane while keeping internal dimensions the same. Length, taper and volume are the critical ones, gentle bends, much less so. Those of us who have experimented with exhaust dimensions favour straight systems for testing.
     
  14. Mar 28, 2018 #154

    Raceair

    Raceair

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    Many of us old Ultralight guys have tried to make improvements to that Muffler, but in the end, its just an 11 pound part of the power package that is best just used as-is.....Rotax had it well figured out for maximum pounds of thrust. On a good day I could get over 190 pounds of thrust with the little 277 engine, and my 'custom pipes' 'improved' that number to 180 pounds......If it aint broke don't fix it.
     
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  15. Mar 28, 2018 #155

    spaschke

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    for 2 stroke, true if you want an "all-rpm" muffler. But if you want more power at a certain RPM , you can do better and it's not that difficult.
    for 4 stroke not true. We replaced the stock muffler with a powerflo muffler on a Cherokee 140 and got better performance and economy all around.
     
  16. Mar 28, 2018 #156

    Little Scrapper

    Little Scrapper

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    The goal of this thread is to build a simple affordable ultralight with basic tools in a small home shop and do it in a timely manner. This means very little customizing from plans. Trying to build a custom exhaust would certainly require the long learning curve of research, testing, risk of making it numerous times etc.

    I want people to watch the videos and say "Hey, I'm an average guy with a minimal budget and time and I can do this".

    I need an exhaust that the last 20 MiniMax builders all agreed worked great and met those requirements above.

    Everyone knows I'd love to take on the challenge and fabricate a wicked cool exhaust, it would be sweet for sure! But not this, this thread is very much a thread of defined purpose. I want to fly this before summer ends and that's a massive undertaking so nothing custom if I can help it.
     
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  17. Mar 29, 2018 #157

    Raceair

    Raceair

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    Yes, Your deadline does not allow for any experimentation.
     
  18. Mar 29, 2018 #158

    don january

    don january

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    Personally I don't think Scrapper has a chance to meet his deadline on this UL M-MAX it will take that long for the glue to dry.:gig: but oh well nothing like a little negative speculation to motivate. Hope you prove me wrong Scrapper
     
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  19. Mar 29, 2018 #159

    Pops

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    At least Scapper will not have all the time it takes to get the paper work done if it was a little heavier. That is a big help in the time department.
     
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  20. Mar 29, 2018 #160

    cdlwingnut

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    I say it like to fly mine by the end of spring. Bit i never say what year in spring :)
     
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