Budget Ultralight

[Armilite]

Hi,
As the title says, me and a group of friends are looking for advice on how we could power a small ultralight 1 seater aircraft we plan on building. This plane would not be going from airport to airport and never taken more than 500ft up, it is simply for field hopping. Unfortunately we are based in the UK so both our choice of parts is limited and we only have a budget of around £800 (for the engine). We have looked at small horizontal engines up to 25Hp as it seems the only way to obtain a reasonable amount of power cheaply (how we would go about attaching a propeller will likely be improvised) however if anyone knows of any cheaper solutions or would like to offer us any advice on completely from scratch builds - then it is incredibly welcome.

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$800 GBP = $1,065.15 USD.

What Plane you looking at and what is its MTOW?

Your best bet is to buy a Good Used Rotax 277UL with a Gear Drive, 28hp@6400rpm. They were also rated 26hp@6250rpm. Used they can go from $250 to $600. A complete rebuild kit on eBay is $140. The Skidoo Snowmobile 277F/300F Engine is the same Engine, but can only use a Belt Drive. ACE Belt Drives might be able to help you out with a Belt Drive. Scat Hover Craft also used the 277UL. UL version has an O-Ring groove around the PTO, the Snowmobile version doesn't. Could it be adapted, yes. There was a guy just 2-3 weeks ago on FaceBook Marketplace that had (4) Sled 277F's for $100 each. Complete, Engine, Redrive, Exhaust, their 65 lbs.

 

[n3puppy]

Nichoxx-
If you do decide to try 277 engines, some things to consider

Original 277UL and 277F sled engine were exactly the same. (No O-ring groove)
Both have problems with belt drive due to PTO side plastic bearing mount failure. Later 277UL's solved problem by replacing with aluminum ring of same dimension.

Any 1980-84 snowmobile engine used with belt drive needs the plastic ring replaced.
Looks like Lockwood might still have the aluminum ring.
1993 and later model 277/300 snowmobile engines did not use rings so can be used as is after normal inspection.

Also
Original 277UL Gearbox adapter used full gaskets instead of O-rings
Similar concept might be used today to seal gearbox to plentiful (inexpensive) snowmobile engines.

 

[Victor Bravo]

Total BS.

OK, explain how, and we'll see how your explanation holds up to scrutiny by the overall group here. There are several people on this forum who I know are experts, who know a lot more than me... and I'll accept their opinion over mine or yours. If I'm wrong I'll gladly admit it.

 

[shuffman37]

Would a horizontal lawnmower engine work? Or would we need to create a reduction gear? Just wondering if the force of the propeller pulling would damage a generic engine

Small engines use ball bearings or sleeve bearings and do not have good thrust force resistance. If you do a direct drive, you'll need a thrust bearing externally mounted on a propeller shaft. The thrust load from a prop (150-200 lb) will destroy the crankshaft bearings within a few hours. When the crankshaft end-play gets too large, the connecting rod will get pushed out of alignment and fail. If you find an engine with an oil pump and external filter, that should make the lubrication system easier to turn sideways with a new pickup screen and/or mini dry sump tank.

Most mower engines run 3300-4000 rpm and could directly drive a prop.

 

[BBerson]

Small engines have internal thrust bearings.

 

[Armilite]

Nichoxx-
If you do decide to try 277 engines, some things to consider

Original 277UL and 277F sled engine were exactly the same. (No O-ring groove)
Both have problems with belt drive due to PTO side plastic bearing mount failure. Later 277UL's solved problem by replacing with aluminum ring of same dimension.

Any 1980-84 snowmobile engine used with belt drive needs the plastic ring replaced.
Looks like Lockwood might still have the aluminum ring.
1993 and later model 277/300 snowmobile engines did not use rings so can be used as is after normal inspection.

Also
Original 277UL Gearbox adapter used full gaskets instead of O-rings
Similar concept might be used today to seal gearbox to plentiful (inexpensive) snowmobile engines.


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Actually, the 277F was made 1978 to 2008 for Sleds. Only the A Gear Drive used an Adapter Plate, and hasn't been made is 15 Years. There are still some New A Drives floating around, but the Adapter Plates are rare to find today. Your best bet is to use the B Gear Drive, which sells New for $835 if you shop around. Nobody, to my knowledge, is making a Belt Drive for the 277F/277UL. I think the ACE Belt Drive could be Adapted. You should Upgrade the Sled version to a Cageless Rod Bearing. On the Bearing Sleeves, People ran into trouble account they Over Tightened the Belt Drive, so Rotax Upgraded them to the Aluminum Sleeve on Both Ends, not just the PTO. It's getting harder to find both 277 PTO/MAG Sleeves in Aluminum. You also have the option, to make a new Sleeve out of Steel or Aluminum, or just use a Bigger OD Bearing. I believe the later 2000 to 2008 277 Sled Engines that don't use a Sleeve, just used a Bigger OD Bearing. Today, there are Hybrid Crank Bearings that use Steel Races with Ceramic Balls that Run Cooler, and needs less Oil, and have a 3x Life over Older Conventional Bearings. You have Bearings with Plastic Retainers(Junk), Steel Retainers(That can Rust and Fail), and Nylon Retainers(Best).

 

[Armilite]

277 Sled Motor. Built 1978 to 2008! 1978 to 1981 were Points Engines. 1982 to 2008 were Nippon Denso and later 2000+ Ducati CDI Engines. All 277UL were Points Engines unless converted by Dealers. Steve Beatty of Air Screw did a lot of those Points to CDI conversions 2000+. 277UL's used on Scat Hover Craft 1982+ were all Nippon Denso CDI.

 

[Armilite]

277UL Free Air, 1988 to 1992 when dropped. Basically a Fan Engine where they cut off the Fan Housing and added the Free Air Rope Pull Start.

 

[Armilite]

277UL Free Air Case made from the Fan Cooled Engines.