JimD

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Everything posted by JimD

  1. JimD added a post in a topic Yamaha RX1 Engines   

    FEM should be interesting related to fatigue stresses; i.e. the cyclic bending moments between the propeller and motor housing. If you run FEM on your design, I would be very interested if you would post the FEM graphics.

     
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  2. JimD added a post in a topic Yamaha RX1 Engines   

    Kitfox glide ratio not as good as I thought, but better than average.  Even though I read a post where a pilot was riding thermals with his Kitfox.  Though I don't recall if he was maintaining altitude.

    Kitfox: 7.8 (at Vg of 60 mph that is 677 fpm sink rate)
    Lancair IVP/Legacy: 13
    Glasair III short/long tips: 6.7 /7.1
    Questair Venture: 10.5
    Cirrus SR22: 10.3
    Super Cub 6.9
    C 172: 7.3
    Zenith CH 801: 3.6
    Dehavilland Beaver: 9.2
    Twin Otter: 10.1
    Caribou: 10.0
    Pilatus Porter: 8.8
    Quest Kodiak: 8.4
    Britten Norman Islander: 7.4
    8GCBC Scout: 7.3
    Westland Lysander: 9.6
    Short Skyvan: 11.1
    PAC 750 XL: 6.6
    Dornier Do 27: 7.4
    Antonov An-2: 8.3 (approx., each wing)
    Sportsman 2+2: 9.1
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  3. JimD added a post in a topic Yamaha RX1 Engines   

    I didn't mean a speed brake with engine out.  I meant during normal operations, would an intentional control of a free-wheeling prop make a good speed brake to provide added control of the aircraft?
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  4. JimD added a post in a topic Yamaha RX1 Engines   

    Increased drag from a windmilling prop was counter intuitive for me.  So I did a search, and sure enough the induced drag is far more than the sail area drag.

    https://forums.jetcareers.com/threads/windmilling-vs-stationary-prop-drag.37467/
    A feathered variable pitch prop has reduced drag because the pitch is taken out (no rotation) and also has reduced sail area.  So the clutch should stay engaged during an engine out emergency.

    Overspeed of prop or mechanicals ignored for the moment.
    is this then an effective "speed brake" allowing for a quick change in altitude without gaining air speed?

    Scenarios
    Losing altitude on approach after clearing a mountain ridge line.
    Clearing an obstacle at the end of a runway.
    Descending from cruising altitude
    ... other scenarios?
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  5. JimD added a post in a topic Yamaha RX1 Engines   

    Nice sounding engine.  Nice clean installation as well.
     
    I've never been around a plane with a propeller clutch before.  Strange to hear engine running and not see the hub spinning.  I would guess that will improve your glide ratio significantly; among other benefits.
     
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  6. JimD added a post in a topic Yamaha RX1 Engines   

    You really have an outstanding accomplishment.
    You mentioned the oil test port.  A spring loaded check valve and auxiliary/prelube oil pump may be able to hook directly into the oil pressure test port.
    Since the RX-1 is a pressurized oil system, I wonder if its TBO would benefit from a pre-lube pump and maybe even a pre-heater incorporated into the pre-lube system?   This could additionally provide a convenient means of having a light weight cabin heater system.
    http://turbowerx.com/Scavenge_Pumps/Exa-Pump/Exa-Pump.html
    Since the RX1 was made to be a vertical motorcycle engine, I would imagine the oil pickup would lose oil pickup supply during negative G's, climbing, slipping, and (if considered) inverted operations.
    I would guess that Winter and daily starting, as well as starting after long times between starting, would benefit from pre-lube and pre-heat.
     

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  7. JimD added a post in a topic Yamaha RX1 Engines   

    Since the RX1 is a 4 stroke, is it quiet in the cockpit? As compared to a 2 stroke.
    Can you post a YouTube with your engine running?
     
     
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  8. JimD added a post in a topic Yamaha RX1 Engines   

    Nice !!!! How is weight distribution? The angle is not so unusual, just wondering how balanced it turned out.
     
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  9. JimD added a post in a topic Yamaha RX1 Engines   

     
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  10. JimD added a post in a topic Yamaha RX1 Engines   

    Been a long time since posted, but still a current issue.  Also, now I'm looking for a power plant.

    180 hp too much for a Rotax gearbox, but in an airplane at constant power output, limiting the RPM to protect the gearbox, also extends expected engine TBO. I wonder how long one of these engines would last at the reduced RPM at say 120 HP ?  Seems like a good deal.

    4-stroke, 120 HP continuous for let's say 1500 hours (Toilet Paper Guess), turbo to have same power regardless of altitude
    Depending upon weight, would love to have 120 HP in an Avid/Kitfox

    As for ignition and needed reliability, that's a tough one.  I'm guessing the ignition is synchronized with the turbo operations.
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  11. JimD added a post in a topic Installing Rotax Ricks 670 Muffler on a 670   

    Huge muffler.  Looks like it would have fit better by turning it around and putting it in a belly pod.     Just a nobody, just sayin...   :.)

    I'm thinking of buying a Kitfox with a 670 and I'm still evaluating the pros and cons.
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  12. JimD added a post in a topic AK 670 Powered Kitfox on Barnstormers   

    I know it's been forever since you posted this. But that is exactly why I hope you still monitor this thread.

    Unless I'm wrong (been at least 10 minutes since that's happened), Rotax Rick has a temperature control process required for warming up 2 strokes to keep the piston from cold seizing.  That requires idling under load at 4500 RPM before takeoff.

    https://rotaxrick.wordpress.com/install-break-in/

    Since you have been idling at 1500 RPM since 2013, now 2017, have you noticed any engine problems?
    What has been your warmup procedure before take-off?
     
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  13. JimD added a post in a topic Noise Abatement & Cabin Noise Reduction   

    Wow, fast response.

    Good to know about the standard muffler.  I'm planning on purchasing a Kitfox with a 670 and am trying to evaluate the best options.  My family owns a place out in the country, and although taking off is around family and they won't complain, I don't want to abuse their hospitality either.
    Additionally, I'm planing on doing some operations on ultralight fields, and one in particular is near a neighborhood.

    I'm just looking for loads of suggestions to pick and choose from, and I provided what little I have found out so far.
     
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  14. JimD added a topic in KitFox General Forum   

    Noise Abatement & Cabin Noise Reduction
    Reducing noise from Kitfox operations in-general. The three main sources seem to be (in order of significance) exhaust thermal expansion, propeller wash around the slipstream of the cowling, and intake air. Taming Noise is a concern to prevent ordinances from being created to prevent flight operations. While flight with reduced cabin noise contributes to hearing protection and creature comfort.  60dB disturbs sleep.
    What are pilot & A&P experiences, and what ideas/suggestions can be provided?
     

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  15. JimD added a post in a topic Noise Abatement & Cabin Noise Reduction   

    Quieter Propellers:  
    Paddle style propellers seem to be quieter in-general

    Off the Shelf: 
    The Felix bi-camber propeller: http://a.moirier.free.fr/H%E9lice/Construction/The%20Felix%20propeller.pdf
    excerpt: Fred Felix at W-10508 Bell Rd., Camp Douglas, WI 54618, 608/427-6544 or l-800/PROPELR

    NASA Stinson & Cub Testing: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19960008053.pdf
     
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  16. JimD added a post in a topic Noise Abatement & Cabin Noise Reduction   

    Swiss Muffler : http://www.piteraq.dk/flight/muffler.html
    The Swiss Muffler is home made, and similar to a GlassPack silencer but much lighter: https://www.summitracing.com/parts/sum-630853?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-summit-racing&gclid=CITa66j39tICFVM8gQodcUgEQQ
    Fairing the front and rear to limit drag.
    Using aluminum round down spout (nice finish), stainless screen, fiberglass insulation, and stainless chore grill as dampened expansion chamber, the total weight would be around 3 pounds for an 18" muffler without significantly contributing to backpressure. The longer, the quieter.
    https://www.guttersupply.com/p-Half-Rnd-Products-Downspouts-Plain-Rnd.gstml?gclid=CPrDksP59tICFUtNfgodJxsOaA
     

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