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E-Tec or Polaris 800 conversions

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Posted (edited)

Edit: I own a KF1  so I'm interested in the lightest weight horsepower i can find.  Yamaha's look like an awesome conversion but they're way too heavy, in that vein I'm looking at 2 strokes that could be converted for aircraft use.  The name of the thread reflects the first 2 engines i looked at but any lightweight engine in mas production is welcome for consideration. 

 

I've been wondering why i haven't heard of any efforts to convert the above listed engines for aircraft use. Ive heard plenty about the Yamaha 4 bangers and plenty of moaning about the lack of good light 2 strokes for the lighter foxes and avids. 

I've read comments that the E-Tecs are heavy and since Rotax pulled out of the 2 Stroke aviation market it wouldn't surprise me if they intentionally designed the pto side of their sled engines to be hard to mount a redrive to I'm just surprised i haven't read about anyone trying it. Seems like a lot of horse power for the weight even if they are heavier than a 582. I added the polaris in there just because I've seen pics of the engine and at a glance it it looks like it has potential.

I know there are issues with ecu that could go into limp mode and drop you out of the sky but people have found ways around that. 

Ive been reading about engine conversions for a long time and know most of the arguments about why they are so problematic, just wondering why ive never heard a whisper about anyone trying to convert the above listed engines. Is there something that makes these even more trouble than others?

Edited by Willja67
Clarifying purpose of thread
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Posted

because there is no good way to mount a gearbox to it otherwise it would be awesome

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Posted

I’ve seen some very simple psru’s before that use a thick cogged belt that seems like there should be no limits to what we can do. Just need smarter people than me to figure out the math.

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Posted

Re_Drive_001.thumb.JPG.ce0d744917720cbb1I've got a cog belt redrive left off my Hirth.

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Posted

because there is no good way to mount a gearbox to it otherwise it would be awesome

Well maybe we could take a page out of the rotary engine guys book. cozy-engine-conversion-2009-08-update-00The above pic doesn't precisely show what I'm talking about because i couldn't find the pic i wanted but, you can see the thick aluminum plate that the engine is bolted to that is then mounted to engine mount(very much like the plate my 532 is bolted to on my bird). You can also see the big plate with the standoffs to the engine that the PSRU and starter are bolted to.  One design I've seen has the bed mount plate extended forward with the psru mount plate bolted perpendicular to the front edge.

Why couldn't we do something like that? Might have to get a little creative to design the standoffs for the top of the mount plate but as I've mentioned most of the 2 stroke engine mounts are already designed for a bed mount. That should make things maybe a little easier since we won't have to come up with an entirely new mount. 

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Posted

20190105_200447.thumb.jpg.30d0c595fdcd53okay here's a quick and dirty concept. The red thing is the engine the grey thing is the bed mount plate and the purple thing is Psru mount plate. 

Ok guys shoot it full of holes, any reason this couldn't work?

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Posted (edited)

I’ve seen some Weed hopper 503’s use a similar exactly like that

Edited by Matthewtanner

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Posted

I have an old belt drive that mounted on the bottom of the engine, then went up for the part that held the large driven pully.  That front piece had another piece that bolted to the head bolts on the top of the engine, and that kept the top from bending forward from the pull of the belts.   I thought it was a good design, but newer belt drive reduction units aren't made that way, so maybe not??? JImChuk

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Posted

Will,

That shelf concept would work, but a quick thought experiment would tell you why it isn't ideal. A set of struts in the same shape allows you to eliminate all the metal where it isn't needed, and leave strong, hollow members where the stress must flow. My guess is hollow struts would weigh about 15% of what those solid metal thick shelves would weigh.

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Posted (edited)

Will,

That shelf concept would work, but a quick thought experiment would tell you why it isn't ideal. A set of struts in the same shape allows you to eliminate all the metal where it isn't needed, and leave strong, hollow members where the stress must flow. My guess is hollow struts would weigh about 15% of what those solid metal thick shelves would weigh.

Like i said quick and dirty, but yeah any idea to cut weight down is welcome.

I know I started the thread talking about high power engines but since i have a KF1 and winning the stol drags is just a fun little exercise but not something I'm serious about, finding a good engine is. And it would be nice to have a lightweight alternative to the rotax 582  with maybe a little more power, that could use an adapter like the above to mount a rotax c gearbox. 

If i were to decide to convert a sled engine these are things i would look for:

1. Obviously lightweight

2. Large production run with good parts support

3. Known reliable engine that makes 100-120 hp, Hopefully doesn't have the seizing issues rotax has. 

4. Not alot of electrical work to do on it, ie minimal sensor and ecu/ wire harness problems to deal with. 

I don't know much at all about snowmobiles so can any of you suggest a make/ model/ year sled that would fill the bill? Any other requirements to go on that list?

It would be nice to come up with a package that some enterprising individual could sell in kit form or even create a conversion manual that could be bought.  If i had the machining skills it would be tempting but i don't. 

Edited by Willja67

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Posted

Leni was talking about putting an 800 CC artic cat engine on his Avid, But I think that is on the back burner at the moment.  Seems he thought the 800 CC engine was pretty durable.  JImChuk

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Posted (edited)

Will

I think a lot of the forethought has gone into this by the folks who looked at the Yamaha Apex engines, and the gearbox that Teal Jenkins is testing right now (and taking orders on, via his FaceBook page) might be a ready solution. The family of Yamahas delivers 200,000 engines a year since the early 90's, so there is a mass of data on reliability behing them. It seems that there are several variants of the Apex that deliver between 140 and 200 HP, and Teal's gearbox is a dandy solution for the stepdown from 10,000 rpm to something more digestible by a prop. 

I am sure several other sled engines are also fine, but since several folks are pioneering the Yamaha path, we can benefit from them. I posted this in another similar thread:, here are some links to explore:

 

I think a cheaper way to get 200+ HP is to look at those turbocharged Yamahas, I saw a fuel injected, turbocharged low mileage sled for sale on craig's list for 3500, plus one of those boxes that are now being tested, (see the thread and FB page by Teal Jenkins) and you could get big horses (200+) for much less that $10K. Here is the FB page: https://www.facebook.com/groups/164864990778457/  and here is the AFF thread: http://www.avidfoxflyers.com/index.php?/topic/5824-yamaha-apex-skytrax-adapters/&page=3#comment-58241

As far as reliability, these 4 strokes are built by the 200,000's per year. And their part pricing is 10% of the Rotax gouge.

Edited by nlappos
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Posted

The problem is i have a KF1 and most 4 bangers are flat out too heavy as is the yamaha. I'm not interested in 200 horses I'd be happy with a more reliable 80 hp if i didn't have to worry as much about seizing the engine.  The only reason I'm looking at the 100+ hp options is that's what a huge percentage of the sled market is.

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Posted (edited)

My vote for a 2smoke would be the 600 etec.  It really has the best track record and durability history.   120 HP but Id derate it to 100 max and 80 continuous.

Biggest obstacle there is (as mentioned) the provisioning for an adapter and gearbox.

IMO the 800 and even 850 etec just havent proven out well enough for use in the air.  They have been "good" at best in sleds and I think Leni is right: among 800s the Arctic Cat motor has the best reputation.

Edited by Yamma-Fox
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Posted (edited)

With that said, my dream motor in a "light" KF or Avid would be the 2cyl 4s Rotax 600ACE.  It is small, reasonably light, high tech EFI, direct drive, and derated at 7300 rpm and 60 HP in the sled.  That derate is to meet BAT noise and emissions standards that are required for snowmo use in Yellowstone Park and other places.

I run one and it is my favorite snowmo motor ever...  ultra quiet, ultra efficient (ACE stands for Advanced Combustion Efficiency), has a broad powerband with nice linear broad torque curve, and time proven reliable (out since 2010).  People ride them until the sled falls apart around the flawlessly running motors (25,000+ miles)

A little exhaust tuning and it can pump out the upper 60HP range at about 7800 rpm.  That's where I run mine and it just purrs along at WOT for miles and miles and miles on end trying to keep up with higher HP sleds. 

I totally believe and would bet my butt (in a plane) that it would do 65 HP continuously for thousands of hours with no worries.   Remember that the 500cc 2cyl 4s Yamaha Phazer reliably puts out 80 HP, and the 600ACE does well with turbo at 90-120 HP, so 65HP seems in contrast to be childs play.

Teal has his hands full but I wish we could clone him and inspire the clone to make up a Integrated gearbox-adapter for the 600ACE!

;)

Ski-Doo_602 ACE-a60ce0e1.jpg

Edited by Yamma-Fox

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