New here but well worn elswhere.

[opsled]

Hi all, I was turned on here by Doug Schwochert (hope I spelled it right). I have known him for many years and have completely impressed with this world of home built aircraft. I will never build or own one myself but I have great interest in what others do with projects like these. My hobby is snowmobiles and I always like to see what others are doing with the powerplants from them. I have bent wrenches on everything from 1150 cu in Cummings diesels to weed eaters over the years and have a wide base in knowledge but will never profess to be an expert on anything (I've delt with to many of them to ever want to be one). I won't be of much use to most of you but may be able to imput on certian engines that have a base in snowmobiling. Yamaha's are what I own but I have delt with and worked on many others.

Thanks, Phil (opsled)

[animal]

welcome Phil, jump right in, I am sure some of the guys converted sled engines will welcome your input. who knows before it over ya may get hooked on these machines your self.

[barnstorm2]

Welcome Phil!

[Racer]

Welcome Phil, Throw in your two cents anytime you see oppertunity to. Glad to have you.

[opsled]

Thanks guys, I probably won't be spending a lot of time here but will be checking in from time to time. If I have something worth while I'll toss it in. Oh and animal, as far as getting hooked, it probably won't happen. Interested yes but the altitude of my brain is about 6ft above the ground I stand on. When it gets much above that it it starts to fade and could quit working if I tried to push it so I think I'll keep it down here and just watch for now. I've seen Dougs helicycle fly and some of his earlier builds. It's cool as hell but I like being able to pull over, get off and fix my mistake as opposed to never being able to learn from it. I do fly but close to the ground. I have been over 120mph on a river at 14 below zero which could be considered reckless so I'm not really a wuss. I just like the option of walking home if I need to.

Thanks again, Phil (opsled)

[animal]

well drop in from time to time, I am sure you can help some that might decide to try the sled engines. 14 below. ok i like the south better everyday.lol

[NoWingsAttached]

Welcome here friend! One hting I have always found kinda funny is that someone got the crazy idea to use snowmobile sled motors on a gyro, with no changes made for clearances and tolerances.

Now, you take a motor designed to run BELOW 0*C, on the GROUND. THat air and the metals have a different way of interacting at operating ranges like that than when you are in temps exceeding 35*C and several thousand ft above sea level and rising.

So why is anybody surprised when a motor fails? I wonder what the tolerances should be for piston clearances and ring gaps.

Racing engines are built with way more slop to allow for higher temps and expansion, right? So what would these little engines run like with more slop?

[opsled]

Welcome here friend! One hting I have always found kinda funny is that someone got the crazy idea to use snowmobile sled motors on a gyro, with no changes made for clearances and tolerances.

Now, you take a motor designed to run BELOW 0*C, on the GROUND. THat air and the metals have a different way of interacting at operating ranges like that than when you are in temps exceeding 35*C and several thousand ft above sea level and rising.

So why is anybody surprised when a motor fails? I wonder what the tolerances should be for piston clearances and ring gaps.

Racing engines are built with way more slop to allow for higher temps and expansion, right? So what would these little engines run like with more slop?


Thanks for the welcome.

I don't think the "sled engine in an aero application" is really a crazy idea. I havn't reserched history enough to know for sure but I think it was likely that a 2 stroke was used in an aero application long before it was ever used in a snowmobile. Early snowmobiles used crude 4 stroke lawnmower type engines. Once the idea cought on and people started wanting them for more than checking trap lines lighter engines with more power were needed. 2 strokes were a perfect fit and many companies such as Hirth, CCW, Kioritz, Xenoah, Rotax and others started supplying snowmobile manufacturers with engines. The Jap's got into it and the revolution started. Todays snowmobile engines are much more advanced that most of the UL engines I see. They are also more specialized so some might be an even worse fit as a crossover in the UL scene. Anyway I think the "crazy idea" may have originally started in reverse with aero 2 strokes being installed in snowmobiles. It would be very interesting reading if someone were to write something on this early history as I think there are some misconceptions on the real story in todays world. Both UL and snowmobile applications need lightweight HP and 2 strokes fit that bill so it doesn't surprise me that there is crossover with the powerplants from them.

Design differences? Sure. I'm no expert on Ul engines but I think most of the basic differences are in fuel and ignition systems and how the engines are tuned to deliver their power. All the UL engines I have seen are "detuned" as compaired with their snowmobile equals. I'm sure this is done to increase their longevity and to reduce engine failure due to stress. Most sled engines don't see 1/10th the maintenence or inspections you guys do to your engines and the CVT drive system they use can put some severe stress on the crankshaft and bearings so they must be built tough. They are also run in some extreme conditions at higher HP ratings so if they were weak and prone to constant failure knowone would buy them. I do know that in most applications UL engines are under a more constant load for much longer periods of time. Even though it may be only at 2/3 (or so) of what that engine is capable of. Snowmobile engines rarely see full load for long periods of time. I don't think they are built lighter because of that fact but you could argue that a sled engine with equal time on it could be in better condition (if properly maintained) than a similiar UL engine with the same hrs. I doubt if most sled engines make 100% of their potential for more than 20 or 30% of their life but if they wern't built to do so they would be poping right and left.

I'm not sure if there is much difference in design because of different temps they may run in but I would say probably not much if any. I wouldn't hesitate to take a 503 UL engine and install it in a snowmobile. Once properly tuned for it's new environment I think it would perform and live just as well as one that came in a sled originally. To reverse that senario would make me much more cautious because walking home from a problem is usually not an option. I think the danger factor of flying and the need to have everything perfect is more important than where the engine your using originally came from.

As far as cooling goes and tolerances, I think there may be some issues there to consider but there are other things that play into the equasion aswell. Here are a few. UL engines are detuned so a 503 in a UL will make less HP in a UL than in a snowmobile and at a lower RPM. HP and RPM make heat. A UL engine will make less heat than a snowmobile engine so which one needs a larger cooling capacity? Could they need the same because the snowmobile engine is running in colder temps? Warm air and altitude also take the ability of an engine to produce HP away. You can make much more HP with the same engine at lower altitudes and colder temps than in warm temps and high altitude. Again less HP = less heat = less cooling capacity needed? I don't think so but the argument can be made that UL and sled engines have much more in common than most would want to admit. They are different in some ways there is no doubt but many have been very successful with crossovers in the past and many more will have success in the future.

I think there are more myths and ledgends than truth in many cases on this issue but it is interesting stuff to think about.

I guess the last thing I would say in regards to failures is that 90+ % of all the 2 stroke failures I see are from lack of maintenance and human errors. There are some bad designs that are prone to break down but most peoples problems are self inflicted. I don't know if the same is true in the UL world but it is in the snowmobile world.

Sorry for being so windy, Phil (opsled)

[animal]

Good post Phil, very informitive and give alot to think about. I am looking forward to hear the reports on Racers sled engine conversion. also keep in mind, in a gyro once you climb up to altitude a gyro throttles back some and is not running wide open like it would be if installed in a helicopter. so that being said, depending how many r.p.m. the sled Engine has to turn to keep ya at flight speed, it very well might turn out to be a great engine in the Gyro. I guess that is why I am looking forward to flight test reports.

[Racer]

Just to give all a mini report on my engine, I have been out doing some crow hops and I love my new engine so far. I get off the ground at less than half throttle and the engine does not even sound like it is working, Never got above 180 degrees (That is where the thermostat keeps it) The only issue I have to work out is the Prop and passing air are sucking oil out of the oil tank vent tube.
Note; The stock engine has a big air box which I eliminated and replaced with individual air cleaners. The vent tube used to go to the stock air box, so this issue is because of my own modification.

[RotoPlane]

Welcome to the forum Phil. From all the reading I’ve done on snowmobile engines, I do not see a problem using most of them in gyros. You obviously have experience in this area, so I would like to pick your brain a bit. You like the Yamaha engines but do you have an opinion on the 2002 Suzuki (Arctic Cat) ZR500 engine with reed ports? Supposedly it has a beefier crank and more power than a ZR580. I can get a new one for $1500, plus about $120 for carburetors. I don’t have a torque and HP chart on this engine but I understand it should deliver about 60hp at 5500rpm. I need to find a suitable (and inexpensive) engine for my UL gyro build, so a Rotax is not an option. I don’t feel comfortable with a used engine because it may have been treated badly.

[opsled]

Animal, Thanks for the kind words. I tend to do as much thinking as working sometimes. Partly because it's easier (I can be lasy) and partly because I don't like making mistakes (I've had my share).

I think Racer will like that engine more than he can imagine once he gets the bugs worked out. In the snowmobile world it's not considered a high HP engine but when compared with what is used in UL's it's up there and what is really great about these Yammie 4 strokes is how they deliver their power. The HP they deliver is good but their TQ is very high and delivered over such a wide rpm range as compared with 2 strokes that they feel much stronger than some of the #'s would suggest. When DynoTech did their first test on the 4 cylinder 140HP version like the one I ride they stated >>> "Though our HP was less than expected, HP/Torque was very high in sled term. So high, in fact, that our dyno absorbsion unit could not hold the engine below 5000rpm! Two cycle engines are "off the pipe" at clutch engagement, meaning withought the supercharging effect on tuned pipes helping at low revs, even 1000cc sled engines are like overgrown chainsaw engines, and can easily be controlled on our dyno at 3-4000rpm, WOT"<<<. This was the first time they had this happen but it was also the first CVT style 4 stroke they tested.

The 120 like Racer is using may not produce as high of #'s as the 140 but it was designed specificly for this application and it's HP/TQ range is even broader than the 140. There are guys with well over 30,000 miles on these engines and most are reporting that they are running as good as new which is unheard of in the snowmobile world. Most 2 strokes need a top end rebuild at 5-10,000 and many never make that far without being total junk. There are exceptions and and some very long lasting 2 strokes out there so this is not a knock on them but none of them will ever see what the 4 strokes could see when it comes to miles or in your terms hours.

Racer, I had a thought on your oil problem. I may be comletely off base but I can see no reason for that engine to be pumping out oil like that unless the air movement you are describing is causing such a vacume around it that crankcase pressure is pushing it out. If thats the case I would think that it would also be an issue for other 4 stroke engines used in similiar applications. I just wondered if Rotax or some other 4 stroke aero engine builder has had this problem and allready has a cure that you could incorporate into your setup.
Just a thought.

RotoPlane, Sorry but I don't have any experience with that engine so I wouldn't have a valid opinion on it. It may be perfect or not, don't know. The price doesn't sound to bad but I would try to get the electronics to run it in the deal. Those components can get VERY expensive if you have to buy them through a dealer. In general when picking an engine I tell people to look for something that has had a long production life and try to find the latest version of it. In 2 stroke sled engines there were many 1 and 2 year wonders who's designs didn't pan out. All the manufacturers have had them but some more than others. Do a google search for that engine with the word "problems" or "issues" in it and you will usually find something if it had them. You can reverse that search to find out good things about it as well.

There are many options in used engines but not knowing history on an engine would not make me comfortable either. I am not likely to be seen at anything above my present elivation but if I were so inclined I would probably go through anything I would buy (new or used) just for piece of mind.

Good Luck

Thanks Guys, Phil (opsled)

PS. Racer, I watched the video link in your signature and made it to the end without puking on my keyboard. Those guys are insane. Very Cool!!