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Thread: Cbr 1000 ?

  1. #1

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    Default Cbr 1000 ?

    READ THIS FIRST: I design scientific instruments for people who study plants and food. High tech electrical gear. I know nothing about airplanes and almost as little about engines. I’m posting to learn.

    I am dead set on flying a kitfox that I build myself. I love the experimental aircraft concept. In-line with this, I want to experiment.

    I understand motorcycle engines have been used (and abused) in airplanes already. I am an avid motorcycle rider. Motorcycle engine tech is advancing very quickly. A 2020 engine is much better than a 1996 engine. Like iPhones and other things, I think quantity/market demand is driving them to innovate faster than say ... LSA engine manufacturers.

    I’ve been watching tons of videos on rotax engines and planes flying with them. Maybe we just have different ideas of what reliable is, but they don’t seem reliable.

    With motorcycles the best bikes don’t usually have the most reliable engines. E.g. a Super Duke 1290 is a great bike, but KTM pushes their engines. Japanese bikes, Honda specifically, had a reputation for building extremely reliable gear. And it’s more true now than ever before. My current bike is a Yamaha, similar story there.

    So with this in mind, I’m playing with the idea of a CBR 1000 engine...

    Weight: ~150lbs before mounts and accessories.

    Power: ~110hp and 75lbs torque @ 6000RPM
    ...My plan is to run the engine at low RPM. It’s 140HP at 8k RPMs, which I suspect to wear the engine out.

    Liquid cooled, electric fuel and air intake, etc. Modern gear.

    Help me understand (with reasoned arguments) why this is a bad idea?

  2. #2

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    Default Re: Cbr 1000 ?

    The first thing that comes to mind is that airplane engines are designed to handle full power loads for extended periods. You fly at full power till you reach cruise altitude then you throttle back to ~75% power. Road vehicles never see that kind of loading. Cooling can be an issue as well as wear. Secondly, airplane engines have dual ignition for reliability. I don't want to say not to do this but you and I are in similar situations: electrical engineers with limited flying experience (20 hours in my case). I'm putting a 912UL in my Kitfox to give me one less thing to consider. (I am working on a cool DIY glass panel though).

  3. #3
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    Default Re: Cbr 1000 ?

    Not saying it would not work, but you would be reinventing the wheel. If your not a fan of the rotax, then go with the yamaha apex or the Edge performance EPEX. Gear box and wire harness, motor mounts have already been figured out. You would have a lot of obstacles to overcome running CBR engine. Wire harness, exhaust, motor mount, gear box, transmission, cowling, ect. Also don't base your options of rotax based on the "videos" you see. They are very reliable engines in the stock form.
    Dustin Dickerson

    Building 7ss STI x 2
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  4. #4
    Senior Member Delta Whisky's Avatar
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    Default Re: Cbr 1000 ?

    I don't think it is a bad idea. The question only you can answer is: is it a good idea? Kit building means building before you fly. Kit building and putting in an engine no one else has installed means building AND engineering before you fly.

    Possible? It's up to you to decide.

    If it was easy lots, if not hundreds, of folks would be flying behind engines of their personal choice. (OBTW - a considerable number have tried and they aren't flying.)

    There are numerous opportunities during an "ordinary" build to make decisions regarding changes or additions to make it your plane. Those choices and the work required to successfully implement them will add lots of time compared to a "look alike" build. For example: I wanted an instrument panel that tilts - without removing the instruments. Cost: maybe a week, maybe a little less. I needed to find and design the installation of an oil cooler. Cost: about 2 weeks if you count locating the "best" oil cooler - and I still don't know if it will work. I designed my own pitot tube installation. Cost: a day, maybe 1.5 days. And, the list goes on.

    Good luck in whatever you decide to do.

  5. #5

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    Default Re: Cbr 1000 ?

    The BMW motorcycle engines have been used in many aircraft. your biggest obstacle is the reduction drive, with the BMW engine that is already taken care of.

    airtrikes.net sells the reduction drive for the the BMW R1200 GS motors. (R1100 R1150 and R1200 series engines) there are other vendors as well just can't think of there names right now.

    This engine combination is very popular in Europe. and I know a couple trike guys using this engine already. and one guy with a 701 (that thing RIPS)

    Plus I'd trust a BMW motor over a Honda.. especially since BMW originally made airplane engines prior to cars and bikes
    Last edited by 4Hummer; 02-23-2020 at 06:57 PM.

  6. #6

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    Stockton Ut
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    Default Re: Cbr 1000 ?

    Even highly experienced mechanical engineers have had trouble designing and building reduction drives for engines. A drive that works just fine on one engine may fail catastrophically on another engine because it has different vibrations that the drive wasn't designed for. So unless you really know what you're doing(or are willing to spend the time testing to make sure a certain engine/gear box combination is safe) you'd be well advised to find a already proven combination.

  7. #7
    Super Moderator Av8r3400's Avatar
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    Default Re: Cbr 1000 ?

    An engine with an integral transmission will be difficult to deal with converting to an airplane. There is lots of extra work that will be necessary to do.

    In a practical sense, this engine makes no sense in an airplane.
    Av8r3400
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  8. #8
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    Default Re: Cbr 1000 ?

    I have and example of what you are proposing. I belong to a kit cobra forum and met a guy up north of me that started a kit about the same time as me. I got to visit him soon after we started on our kits as he had some parts he would not use for his build that I could use. In the visit he talked about being a boeing engineer and that he had done in college what he was about to do with his car. His build is an all wheel drive coupe which needs a transfer case of his design and other parts including two drivelines and new hubs and another transmission no one has ever used before. His view at the start was that this car was his test bed for his design and it has been cut up, modified and he has posted updates with his successes. I think it is amazing what he has accomplished. His car still is not 100%. We got these in 2015.
    I guess what you need to decide is if you want to go that route and experiment. These are called experimental. Or, go with proven ideas and get it done and start the next phase of being an experimental airplane owner and pilot sooner. My cobra build took about one year with about 4 months of backordered parts to wait for. Personally I can't wait to start the next build on my kitfox and then fly the heck out of it. I have enjoyed my car to the limit with my seattle car club and all the places we have been with others that have cobras.
    Starfox

  9. #9
    Senior Member rv9ralph's Avatar
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    Default Re: Cbr 1000 ?

    I have a few thoughts.

    First, experimenting will move innovation, making improvements we all can benefit from... however, as Someday7 stated, that experimenting with propulsion systems in autos is different from aircraft. If the system fails in an auto, you can coast to the side of the road and call a tow truck. It the propulsion system fails in an aircraft the results can be more catastrophic.

    Also, developing a PSRU (prop speed reduction unit) system to reduce the engine performance RPM (6-7K) to a usable prop speed of 2-3K is a challenging engineering endeavor. In the 90s there were many options to choose from... they are no longer around... due to either not enough buyers or too many failures to remain viable. I knew a local pilot that built a 3/5 scale P38 using 3 cylinder engines that were rated at 100HP, but did not have enough torque in the midrange to turn the props through the PSRU to the power band needed, even with a flat pitch. He spent a year working on the problem and had to reprogram the Engine Control Module to remap the performance, which was still disappointing. He managed to fly it enough to get through Phase 1... then donated it to a museum.

    As a side note... I did hear of someone using a Honda Goldwing engine with the original gearbox, safety wiring it in 3rd gear to get the most efficient prop RPM.

    Just my thoughts...

    Ralph

  10. #10
    Senior Member
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    Default Re: Cbr 1000 ?

    Shawshaw. I reread your post and i think you could do both if you have the funds. Set up a test stand for a low buget motorcycle engine and plane prop. Testing it to about 2000 hours and at the same time build your kitfox. The time frame may line up just right. If the engine holds out then it may be an excellent powerplant for your build.
    Starfox

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