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Could a BMW K100 engine be airworthy?

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oriol

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Barcelona, Spain.
Hi everyone!

I think Hegger dynamics is the only company selling a roadable aircraft, 2 axis.
It s a current yamaha quad with what it seems to be a centrigugal clutch for the prop, I guess
they put the engine on neutral for flight.

db_ATA-Deesberg_0071.jpgHPIM2059.JPG


I would like to try something like that with a BMW K100 engine. Maybe It works with too much RPM to put the engine on neutral?

Can I try to fly with the second or third gear on to reduce the RPM so that I don t have to use a reduction gear saving a bit weight?


Thank you very much for your answers!



Oriol
 

oriol

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Thank you very much for your answer Craig!


I ve seen many trikes in Europe with BMW boxer engines (100 RS, R 1200) and rotax reduction gear. I never seen any with my own eyes flying with a K100 or K75 engine, it s not usual at all.
Some people complained of too much vibrations for the boxer engines on trikes. The K100 engine is supposed to be smoother, 4 pistons instead of 2 big ones.
On the other hand it works with more RPM.


BMW K100RS 83.jpg K100


I checked the post you linked and I found a K75 with a Rotax reduction gear and another homebuilder with a boxer engine who kept the second gear of the original gearbox to reduce the RPM. Apparently he just have to adapt a centrifugal clutch to start the engine and then accelerate a bit to drive the prop, he said the engine didn t liked to start straight with the prop.


From what I know it seems that centrifugal clutches are quite inneficient: nobody likes to loose a single HP on flight.
Do you think or have you ever heard of someone using the original auto clutch to start a propeller?

Would the engine start without any clutch at all? Is that fine?

Some data of the K100 engine weights 100Kgs (with everything gearbox...), 6000 RPM, about 100 HP. Do you have any idea how much reduction would be required?

This is a ecomobile, It works with several kinds of BMW motorbike engines. If you could use the engine for both ground and air it would become a great roadable car.

ecomobile.jpg

_) It won t be easy to get two outputs from the engine one for the wheel the other one for the prop. I have some ideas but you need to add some weight.


Thank you very much for your comments!:)




Oriol
 

oriol

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I m gonna check some bibliography about props, reciprocating engines to put everything on numbers.


I thought there was supposed to be major design problem with the K100 injection, water cooled engine for aircraft purposes.

Folks prefer to use the Boxer engine(?), wich causes a lot more vibrations. Plus I haven t seen nobody using the original reduction gears from the BMW gearbox. They buy it from Rotax, probably because that way they can use an already designed prop plus use the rotax box to screw an electric governor etc...

Not very far from where I live There s a a person who designs and build wood props following your requirements, It s not very expensive.




Thanks!


Oriol
 

craig saxon

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Canberra, ACT, Australia
Not sure, but wouldn't a centrifugal clutch lead to the prop windmilling in the event of an engine failure? This would lead to a high drag situation when you least need it.
 

oriol

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Barcelona, Spain.
Not sure, but wouldn't a centrifugal clutch lead to the prop windmilling in the event of an engine failure? This would lead to a high drag situation when you least need it.
I never thought of that but you make a good point against centrifugal clutches.
Many paragliders have a centrifugal clutch to make it safer if there s someone around when the pilot turns the engine on.

I ve seen a few ULM in Europe with centrifugal clutches for the same purpose. Maybe most of such planes got an electric governor too wich can possibly modify the prop pitch in case of engine failure.
I believe none of the centrifugal clutches I saw was certified.


Oriol
 

autoreply

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Not sure, but wouldn't a centrifugal clutch lead to the prop windmilling in the event of an engine failure? This would lead to a high drag situation when you least need it.
Many gliders have the same problem (twostroke). Simply have a belt brake for the prop, or a rubber pin that you insert in the path of the prop.
 

JenDAG

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"... I thought there was supposed to be major design problem with the K100 injection, water cooled engine for aircraft purposes. ..."
Oriol
I shouldn't be be scared about injection on K100, it is BOSH motronic.
I ride my K100 "The Flying brick" sixth season now without any trouble at all. My Brick was born in 1984 and it is true BMW's quality.
Fuel injection system gives you automatic altitude correction up to, let's say, 2000-2500 meters above sea level.
More info about flying bricks on Willk. auf Flyingbrick.de

Jenda
 

oriol

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Thanks for sharing the link Jenda,


I´m a K100 enthusiast too. I noticed the aerodynamic shape of the ecomobile (photo some posts above). It´s powered by a BMW engine.

In the quest for a roadable car I thought the BMW engines were good candidates for the job. The engine acts as structure too and it´s powerful enough to carry one or two pilots and won´t have major problems to carry the extra load of the wings on ground.

The question was to switch the crankshat to the prop or to the wheel. It was worth a post:
"designing a transmission for different shafts sharing the same engine"

It involves some extra weight unless you do something not very elegant a velosolex like transmission:


bardot-velosolex-1971.jpgvelosolex.jpgamphibious-velomobile-photo01.jpg


The yellow czech amphibious tricycle, notice the prop behind the wheel, should use a velosolex like system to power the prop.


Again refering to your quotation about me guessing operational problems on the K100 series engine for aviation.
Once discussing with a homebuilder friend about autogyros, pou du ciel, horten wings: in general unconventional flying machines he said to me: "It may look great on paper but if no one has done it before, or it´s not widely extended there must be a reason a BAD reason"


Other than that I´m with you the BMW K100 engine deserves a try! ;)
 

JenDAG

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K100 engine family (K100 8V/16V, K1100, K1200) is really conventional design. It is more automobile style of design than motorcycle.
That's gives to engine long lasting life and reliability.
Of course usage in motorcycle is very different from usage in aircraft.
You should expect some issues with oil suction from wet sump, same as on other wet sump engine. BMW Formula used K1200 longitudinal (last brick engine) engine and it had problem with oil suction in corners.
Another expectable problem is with design and tuning torsion vibrations damper.

And many unexpectable problems... and it is not good choice for every LSA.

Jenda
 

oriol

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I consider the BMW K100 engine a good candidate for a roadable aircraft.
The vehicle I have in mind it´s not a standard car neither aircraft. On ground: It would be three, trike like two front wheels, or ecomobile configuration like, with two little retractable wheels for stability. Definitevily it´s not a muscle car. I have nothing against Ferrari or Hummer but as light as possible is better in all technical aspects.


In flight it would rassemble more a powered sailplane than a spitfire or a modern Cirrus. My idea is to use the engine as little as possible, ideally it would be just for take off.
I live in Spain where there are very good places for soaring, most of the soaring birds in Europe live in Spain and Greece. A roadable soarer would be "practical" for moving along the country, of course you depend on the weather.

410px-Bartgeier_Gypaetus_barbatus_front_Richard_Bartz.jpg800px-Flying-Gyps_fulvus.jpgMotovelero Sirius1.JPGSWIFT.jpg

In case the engine proves to be reliable It may be interesting to run the engine for long periods and see If it´spossible to fly long range.


For the time being: my economical situation, available time for working on such a project... etc
I´m working on a tricycle (SWIFT concept like) that would carry a folded delta wing to the top of the mountain. I may also try to put a little two stroke engine for taking off.


An autopowered vehicle eases a lot the legal issues and is a simple interesting start.


Oriol
 

JenDAG

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Good luck Oriol with your hybrid. Let me know when you fly it.

Just one short notice: The aviation history teach us that new engine and new aircraft never works toghether right. You will never know if it is engine or aircraft issue.
What you need is combination of well known engine with history of service data with good background support (comunity, etc) fitted on new aircraft, so you can focus only on aircraft
OR
well known aircraft with history of service data with good background support (comunity, etc) equipped with new engine, so you can focus only on engine.

Doing both in same time does not work, unfortunately.

Jenda
 

oriol

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Messages
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Location
Barcelona, Spain.
The aviation history teach us that new engine and new aircraft never works toghether right. You will never know if it is engine or aircraft issue.

Yes facts confirms your statement every now and then. For the particular matter of a roadable aircraft, the last serious attempt on a multipurpose engine for both ground/aerial, the terrafugia seems a never ending project.
Other projects sharing similar difficulties the composite boeing, F22 Raptor stol, and DARPA´s transformer XT flying car.


Terrafugia_Transition_flying_car_gets_go_ahead_from_US_air_authorities13.jpgterrafugia-flying-car.jpgimages.jpegTransformer_AVX.JPG189909,xcitefun-avx-aircraft-car-2.jpg


The terrafugia is powered with a 100hp Rotax, a gear box connected to it for ground use.


My idea is to dissociate the project in several mini projects so that I can face the problems one by one. Of course like any homebuilt project it still requires big doses of patience and enthusiasm.



I´ll first try a tricycle, I allready tested a home made recumbent two wheel bike: It´s not stable enough for landing and you can´t bolt a delta wing to it you need to trailer it, plus several other issues.
Other than that the position of the cyclist is incredibly comfortable and the efficiency pedaling is far better than conventional bikes.


Then I´m gonna try different flying configurations: paraglider, delta and maybe 3 axes or a rigid flying wing. For the moment I´m not at that stage.


Oriol
 
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