Low budget Ultralight Aircraft

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MGriffin

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I'm new to this forum, but I've read several threads discussing potential low budget aircraft builds. One of these threads that caught my attention went over the biggest problem (in my opinion) with a low budget aircraft.

The engine. If you plan on buying a purpose built aircraft engine, you might as well kiss affordability goodbye.

The thread I mentioned above (I'm unable to find it, I read it about a year ago and I'm also posting with a low quality smart phone) discussed alternative aircraft engines.

Several people had the idea to use industrial engines, like Briggs and Stratton V twins. Another idea that came up was to use a motorcycle engine. Yet another idea was to use a Go Kart racing motor, like a Vegas Carts 460.

These are all great ideas, but there were a lot of naysayers and armchair experts as always, so I don't think anyone came up to a conclusion or found a solution.

I'd like to offer proof that you can successfully use something besides a purpose built $2500+ aircraft engine.

I hope my thread helps the low budget cause. I am looking to design and build a low budget ultralight aircraft, and I always run into the problem of finding a suitable low budget engine.

Here's a person that uses what looks to be a Honda gx390 with a belt reduction on a SkyPup ultralight. It flies. It takes off under it's own power. Sorry, but I couldn't find any specs.

https://m.youtube.com/watch?v=ztJE0-NbKAo

Here's a person that uses two performance modified 6.5 hp Honda clones on a Lazair ultralight. You got it right. A twin engine ultralight.

https://m.youtube.com/watch?v=rehhYT-g9Mk

Here's the thread where the twin Honda clone Lazair guy goes over some specifics. I'm assuming it's the same guy from the video above. Apparently each motor produces 75 lbs of static thrust at 4400 rpm.

http://www.lazair.com/forum/viewtopic.php?p=8194

Here's a person that put a Honda gl500 engine on his CGS Hawk ultralight. Apparently it climbs at 8-900 fpm and cruises at 70 mph while using 1.5 gph of fuel. I highly encourage you to read the description of his video for specifics, and please watch his other videos if you doubt the airworthiness of his concept. This is my favorite idea. Honda gl500 engines are notorious for their reliability.

https://m.youtube.com/watch?v=NnGXUKz1Wpg


As a disclaimer, I am not an expert aeronautical engineer. I have never built an aircraft. I am a **** good mechanic, and I have a pretty good understanding of physics and engineering. I would like to build an Ultralight aircraft of my own design very soon. I've been working on the design for awhile, but haven't really gotten too far because I can't decide on a motor.
 

Topaz

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The lack of "affordable" motors in the 25-40hp range, ever since Rotax essentially pulled out of the market, is one of the real problems for ultralights today. There are the various paramotor engines, of which Polini seems to be the current favorite, but they're hardly "inexpensive" in this context and finding someone who will sell you JUST the engine is something of a chore - most of the distributors of paramotor engines want to sell you the entire paramotor rig.

All the options you show are pretty much the sort of ad hoc solution that the ultralight guys in the 1970's and '80's were doing, before someone discovered the McCullogh 101 and everyone settled on those. It's what you have to resort to, today, to get a really inexpensive ultralight motor. Now, there are conversion issues and the small-motor crowd has yet to really settle on a "standard" conversion yet, but I keep hearing about progress here and there.

Fortunately, most ultralight installations don't require much in the way of real reliability, and the ability to convert a small single- or two-cylinder engine for this kind of usage implies the ability to fix one, so it just becomes part of the "joy" of flying this kind of experimental ultralight. Fly it, break it, glide down, land, talk about it around the campfire, take it home and fix it for another day.

Have fun with it. Most seem to agree that the one thing these motors need is some kind of PSRU-like drive, both to reduce the prop speed and to unload the meager thrust bearing built-in to these motors from the thrust and gyroscopic loads a prop will produce. Then these discussions generally get into the "inferior quality" and "plastic parts" in the motors, and how "I wouldn't fly behind one." Well, like I said, these are ultralights. Your're not crossing oceans with them. Breaking the motor and fiddling with it seems like it was half the fun for the 1980's crowd. No reason it can't be so today, as well.
 

StarJar

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I've thought often and hard about the VC 460. Don't know why more people don't use it. I was thinking a direct drive, but the reduction might make a little more sense. Wouldn't that be about 70 lbs and $1000, not including the prop?
I'm going to check out the Honda Gl 500, too. Sounds interesting.
 

MGriffin

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I completely agree with what you said Topaz. I'm not going to be flying over the rocky mountains. I certainly won't be flying over densely populated areas. I just want a cheap way to get in the air and have fun.

I find it hilarious that the armchair experts use "plastic parts" and reliability as an issue.

The VC 460 doesn't have any internal plastic parts. It has a billet connecting rod and chromium/molybdenum alloy steel push rods.

Read this:
http://karting.4cycle.com/showthread.php?34812-The-new-460cc-from-Vegas-Carts

Some guy ran his VC 440 for 8 weekends at 7500rpm and didn't have any issues. Apparently the VC 460 weighs 52 lbs ready to race, so as StarJar said you could easily keep it at or below 70 lbs with redrive and prop. I think the 25 hp rating is being conservative. I would estimate around 30 hp. I could be wrong.

The gl500 would easily surpass most if not all 2 strokes for reliability. I'd trust that motor to keep going no matter what. The only issue I can see with it is fabricating a redrive for it if you decided to go that route.
 

StarJar

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I don't think you're going to find any plastic or flimsy parts in the VC 460, because it's made in the USA for full out go-kart racing or heavy output in golf carts..
I've heard they are a pretty tough engine, also from people who install them in mud boats, and run them at high power for long periods.
As far as meeger thrust bearing, I thinks its more like either you have a thrust bearing, or you don't. I forget if the 460 has one. I talked to the rep a year ago, and wish I could remember.
It would be tempting to me, to run it at 4000 rpm direct drive, with a 48" prop, but that's good for only about 20 hp. With the redrive you might get about 25 HP continuous, maybe 30 for climb and much better prop size for climbing.
 

MGriffin

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Ace aviation makes a redrive unit for the Honda gx390. I think this may fit a VC 460.
http://www.aceaviation.co.uk/index_files/Page718.htm

I'm going to email VC to see if the front cover bolt pattern is the same. If it is, then I'm going to drop the money for this combination. I'd be looking at $740 for the motor (I'd get the forged flat top piston) and $540 for the redrive. Shipping for the motor is free and $90 shipping for the redrive.

Overall I'm looking at about $1370, and another $300 or so for the prop. I'd still be below $2000. I hope the redrive is compatible, I don't have any machining equipment.
 

BBerson

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Welcome to the forum.
Keep in mind that a racing cart engine might work in a cart, but a redrive with a prop may or may not work.
For example, it could self destruct if resonant torsional vibrations occur. Propellers have a large moment of inertia.
The only way to know is experience.
Your comment that you would trust an unknown experimental engine/redrive is concerning.

Also, the Vegas Cart company may not sell for use in aviation.
Nothing wrong with experimenting. But it is a risk.
I haven't seen these fly at Oshkosh yet.
 

cavelamb

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The only problem with many of the above ideas is that they require a fairly well equipped machine shop to convert for aircraft use.

That may have a lot to do with the popularity the idea of using a VW conversion.

Here are a couple of photos of a Subaru set up we ran for a while.
1800 cc Sube and a Rotax C box.
The Sube was a great little engine, but for weight.
Liquid cooling ads a tremendous amount of development work to the job.
And more weight than most would guess.
In the end the weight and cooling complexity were the killers.

soob01-m.jpgsoob02-m.jpg
 

StarJar

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I agree it's relatively untested. Maybe a lightened flywheel can be implemented. From what I was reading, a racing (lightened) flywheel knocks 10 lbs off the 52 lb. figure.
(I wonder how light it is with no flywheel?)
The thing is though, the racing flywheel might get in the way of the Ace redrive.
I wonder if the Ace unit is made to be used with a flywheel?
The idea being that the flywheel would dampen stuff on the crankshaft.
Just thoughts, can't say if a flywheel is a good or an unnecessary thing.
 

StarJar

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The only problem with many of the above ideas is that they require a fairly well equipped machine shop to convert for aircraft use.

That may have a lot to do with the popularity the idea of using a VW conversion.

Here are a couple of photos of a Subaru set up we ran for a while.
1800 cc Sube and a Rotax C box.
The Sube was a great little engine, but for weight.
Liquid cooling ads a tremendous amount of development work to the job.
And more weight than most would guess.
In the end the weight and cooling complexity were the killers.

View attachment 54482View attachment 54483
This little engine is air cooled. If the Ace redrive is good in design, including torsional vibration consideration, it should be a pretty straightforward installation, I think.
 

MGriffin

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Welcome to the forum.
Keep in mind that a racing cart engine might work in a cart, but a redrive with a prop may or may not work.
For example, it could self destruct if resonant torsional vibrations occur. Propellers have a large moment of inertia.
The only way to know is experience.
Your comment that you would trust an unknown experimental engine/redrive is concerning.

Also, the Vegas Cart company may not sell for use in aviation.
Nothing wrong with experimenting. But it is a risk.
I haven't seen these fly at Oshkosh yet.
You're absolutely right Bberson. There is nothing wrong with experimenting, and the only way to know is through experience.

We'd all still be in the dark if Thomas Edison was too afraid to test his light bulbs. I greatly appreciate that you are concerned for my safety, but you have my word that I will thoroughly test all of my concepts before my future design ever leaves the ground.

Also, I'm fairly certain Vegas Carts won't stop me from paying them $740. They might not agree with the usage, but they don't have to. If they absolutely refuse to sell me one, I have plenty of freinds that can order one for me if I wire them the money ;)
 

cavelamb

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I agree it's relatively untested. Maybe a lightened flywheel can be implemented. From what I was reading, a racing (lightened) flywheel knocks 10 lbs off the 52 lb. figure.
(I wonder how light it is with no flywheel?)
The thing is though, the racing flywheel might get in the way of the Ace redrive.
I wonder if the Ace unit is made to be used with a flywheel?
The idea being that the flywheel would dampen stuff on the crankshaft.
Just thoughts, can't say if a flywheel is a good or an unnecessary thing.
Depends entirely on the engine.
The GEO 3 cylinder will break the crank if you remove ANY of the flywheel.
 

litespeed

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The Ace redrive goes on the front of the engine so should not be a issue.

I personally would be looking at a V-twin instead for more grunt and a bit less stress on the engine.
 

VFR-on-top

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There is a fella (on another board) using an industrial Generac with some success but he had an attitude problem so I quit following the project, but Generacs might be worth looking into if you haven't already done so.

Good luck!
 

MGriffin

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I agree it's relatively untested. Maybe a lightened flywheel can be implemented. From what I was reading, a racing (lightened) flywheel knocks 10 lbs off the 52 lb. figure.
(I wonder how light it is with no flywheel?)
The thing is though, the racing flywheel might get in the way of the Ace redrive.
I wonder if the Ace unit is made to be used with a flywheel?
The idea being that the flywheel would dampen stuff on the crankshaft.
Just thoughts, can't say if a flywheel is a good or an unnecessary thing.
I'm fairly certain that you could run the VC460 with a billet aluminum flywheel. Vegas carts does sell one for $240

http://www.vegascarts.com/product-p/arc6622.htm

But if you installed it, you'd either have to resort to hand cranking or an electronic starter. You can't use a pull start with it. The electronic start and battery would outweigh any weight reduction benefits of the billet flywheel.

I'd be tempted to get one if it is indeed compatible with the VC460, but is a maybe 10 lb weight reduction worth $240? It kinda goes against the low budget ideology. I should get back to work.
 

Victor Bravo

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The service lifespan of the V-twin generator engines is their strong point. They run thousands and thousands of hours with normal routine maintenance. An aircraft version, hopped up just a little, should easily make 1000 hours minimum if operated within "normal" reason.
 

MGriffin

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The Ace redrive goes on the front of the engine so should not be a issue.

I personally would be looking at a V-twin instead for more grunt and a bit less stress on the engine.
The main issue I have with the industrial V twins is the extra cost and weight. They're a wonderful choice if you have the money, but you'd be looking at at least $1000 for a new V twin. And that would be a totally stock V twin.
You'd have to dump probably another $700 into it to get all the necessary performance parts to run it hard without potentially having a catastrophic failure. Correct me if I'm wrong.
I like the idea, but I'm too cheap and the weight of most V twins really imposes design limitations on a FAR-103 legal aircraft. Especially one designed by an amateur like myself. It's definitely worth considering though.

Oh and I'd like to apologize for giving some misinformation about the VC460. Geoff with Vegas Carts says it weighs 67 lbs in its "stock" form. Here's the link where he says this:

http://vegascarts.proboards.com/thread/27/460-crg-road-rebel-kart

The figure I quoted for weight (52 lbs) was acheived with a billet aluminum flywheel. Here's where I got that information from:

http://karting.4cycle.com/showthread.php?34812-The-new-460cc-from-Vegas-Carts


So according to the link above the VC 460 will work with a billet aluminum flywheel. And it also looks like I'm stuck with spending the extra money on it if I want to achieve the 52 lb figure. Oh well, I'd still probably be below $2000 with the complete engine, redrive and prop :)

The image I attached to this post was sent by Vegas Carts. It is the "front cover" for the Vegas Carts 460. They replied to my email inquiry about the bolt pattern. It looks to have a pretty heavy duty ball bearing that supports the crankshaft.

I asked for a more specific measurement, but I feel I am pushing my luck with them ;)
 

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Hot Wings

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You'd have to dump probably another $700 into it to get all the necessary performance parts to run it hard without potentially having a catastrophic failure.
That kind of depends on what you mean by "run it hard"? In stock form industrial engines are designed to run at 100% of the rated continuous power. Continuous power specifications are not always the same as the 'advertised' horsepower and the difference will vary from manufacturer to manufacturer. If you are thinking about bypassing the governor and running them at higher rpm then specified, or adding a turbocharger, to extract more power then you get into the realm of performance parts and being your own engine engineer/designer.
 
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