jehicks87
Member
What are the pros/cons of these two engines, compared against one another, for an UL honeybee/hornet design?
Back again... Rotax 503 vs McCulloch
- Thread starter jehicks87
- Start date
The 503 "may" be able to make Part 103 weight (254lbs)...but not many do.
Weight savers (most are undesirable alternatives):
Single carb?
Belt re-drive?
Light tires?
cable bracing?
Titanium parts (cheek plates, pulleys, hub bar, etc)?
Overhead stick?
Free-air cooled?
No re-coil start?
No electric start?
No electrical?
No guages?
Add a BRS (weight bonus)?
Add floats (weight bonus, like Mosquito heli)?
Light weight custom exhaust?
Reduced sized belt & re-drive componets with newly released Carbon fiber belts?
No seat tank?
Trike style front fork/nose wheel?
Non-steerable nose-wheel?
Carbon Fiber tail?
Weight savers (most are undesirable alternatives):
Single carb?
Belt re-drive?
Light tires?
cable bracing?
Titanium parts (cheek plates, pulleys, hub bar, etc)?
Overhead stick?
Free-air cooled?
No re-coil start?
No electric start?
No electrical?
No guages?
Add a BRS (weight bonus)?
Add floats (weight bonus, like Mosquito heli)?
Light weight custom exhaust?
Reduced sized belt & re-drive componets with newly released Carbon fiber belts?
No seat tank?
Trike style front fork/nose wheel?
Non-steerable nose-wheel?
Carbon Fiber tail?
Last edited:
jcarleto
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The rotax has reliability, the MAC has the horsepower. The MAC may also have a bit better fuel burn, though you have to use 100LL instead of autogas, so it may be a wash from an operating cost standpoint.
It will depend a lot on other factors, such as your weight and the type/brand/size rotors you intend to use. There will also be some design considerations around the thrust line and propeller size, and the motor mounts are completely different.
It will depend a lot on other factors, such as your weight and the type/brand/size rotors you intend to use. There will also be some design considerations around the thrust line and propeller size, and the motor mounts are completely different.
WaspAir
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The McCulloch was designed for an unmanned target drone, expecting it to be shot down, and not to carry live human cargo. Some on this forum have learned enough technical minutiae and lore to keep them running but without such set-up and care they are notorious for quitting at random moments. Search "Mac-attack" on the forum and you'll find lots of mentions.
Stan F - do I recall that you had something like seven engine-outs in your first 100 hours?
Stan F - do I recall that you had something like seven engine-outs in your first 100 hours?
Timchick
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Mac's have to be hand prop started (unless fitted with custom electric start, but then it really won't make ultralight weight). Hand propping has some hazards associated with it. Spare parts are a lot harder to find for the macs. The reliability of the Mac is not as good as a Rotax. Some have had good luck with Macs but nowhere near the level of the Rotax. Getting aviation fuel was always a hassle for me. Mogas for the 503 is everywhere.
Mike484
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This one falls into the UL category, it's currently for sale.
Has pull start (which can be used from the seat), pre-rotator, rotor brake, some gauges, seat tank, water cooled, hydraulic nose wheel brake.
If it's done properly, an UL can have some of the modern conveniences without going over weight.
A Rotax will also make your gyro more valuable and more desirable than a Mac.
Has pull start (which can be used from the seat), pre-rotator, rotor brake, some gauges, seat tank, water cooled, hydraulic nose wheel brake.
If it's done properly, an UL can have some of the modern conveniences without going over weight.
A Rotax will also make your gyro more valuable and more desirable than a Mac.
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Mike484
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And here's another fine example (even though a lot of people will tell you to add a better tail) of an UL with a Rotax 582. Again, pull start, rotor brake, water cooled, some instruments, hydraulic nose wheel brake.
UL can be done with a Rotax and allow for some options you can't have with a Mac and also offers somewhat more reliability.
Some are also having good luck with the MZ 202 on Ultra Lights.
UL can be done with a Rotax and allow for some options you can't have with a Mac and also offers somewhat more reliability.
Some are also having good luck with the MZ 202 on Ultra Lights.
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Mike484
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You should visit the guys at the Morrilton airport, great bunch of guys and they are usually there just about every Saturday.
jehicks87
Member
Mike, thanks for those pictures. Do you happen to know the owners of those aircraft?
Ah, yes, I always meant to go by and meet the morrilton guys, but after I got back from round 2 I got married, and have since PCS'd to Germany... Unfortunately, I never got around to meeting the,. I really wanted to check out the "AirHog".
Ah, yes, I always meant to go by and meet the morrilton guys, but after I got back from round 2 I got married, and have since PCS'd to Germany... Unfortunately, I never got around to meeting the,. I really wanted to check out the "AirHog".
Mike484
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First picture is Ron Menzie's, it's in Searcy Arkansas. I am building one very similar to his but I'm going all the way and getting N-numbers and air worthiness.
The second one, will be mine Saturday when I pick it up. When I got the first KB3 I wanted to keep it as original as possible but I didn't have a tail, blades, engine, engine mount, seat tank, or blades. None of these parts are readily available as original Ken Brock so I installed an RFD tall tail, Rotax 582 Blue Head with and RFD Rotax engine mount, Calumet seat tank, and 23' McCutchen Sky Wheels. Now that I have an opportunity to own an original KB3, the other one will probably get a drop keel and a few more modern design changes.
The second one, will be mine Saturday when I pick it up. When I got the first KB3 I wanted to keep it as original as possible but I didn't have a tail, blades, engine, engine mount, seat tank, or blades. None of these parts are readily available as original Ken Brock so I installed an RFD tall tail, Rotax 582 Blue Head with and RFD Rotax engine mount, Calumet seat tank, and 23' McCutchen Sky Wheels. Now that I have an opportunity to own an original KB3, the other one will probably get a drop keel and a few more modern design changes.
brett s
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Rotax 582 + Sky Wheels & still less than 254 lbs? Seems quite a stretch.
Mike484
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Good catch - That's the one getting the N-Number and airworthiness, there was never the intent to try and make this one UL (I forgot to mention electric start). Even though you would probably never get weighed on a ramp check, some things are just too obvious for it to be UL. And, I like all the bells and whistles that are not available with UL.
