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September 29, 2010 5:20 PM Subscribe
Project help: What should I build with several lawn mower engines?
I have 3 lawn mowers that are no longer good mowers, but the engines still run pretty well ranging from 3hp to 6.5hp. I want to use at least one of them in some sort of project, but don't know what to build. I have access to a small mig welder, and own a bunch of hand tools (grinder, sawzall, etc..) and have some friends who could possibly machine bits and pieces if necessary. What should (could) I build?
I have 3 lawn mowers that are no longer good mowers, but the engines still run pretty well ranging from 3hp to 6.5hp. I want to use at least one of them in some sort of project, but don't know what to build. I have access to a small mig welder, and own a bunch of hand tools (grinder, sawzall, etc..) and have some friends who could possibly machine bits and pieces if necessary. What should (could) I build?
A wind machine. I gotta think 6.5 horses on the right fan blade would make a pretty good wind.
posted by gjc at 5:26 PM on September 29, 2010
posted by gjc at 5:26 PM on September 29, 2010
I think that you should build an ultralight. When I first heard about them they were like hang gliders with wheels strapped on the bottom and a lawnmower engine with a prop to get it going.
They fly just above tree level and they do not require FAA licensing.
Excellent project!
posted by jack.tinker at 5:42 PM on September 29, 2010
They fly just above tree level and they do not require FAA licensing.
Excellent project!
posted by jack.tinker at 5:42 PM on September 29, 2010
Hovercraft
posted by trialex at 5:45 PM on September 29, 2010 [2 favorites]
posted by trialex at 5:45 PM on September 29, 2010 [2 favorites]
Best answer: I think its going to be tough to get enough power:weight to build a plane with a lawnmower engine. Maybe a snowmobile engine. You are basically going to be in Wright Brothers territory on that one.
That said, here are things I've built/seen people build out of old lawnmower engines:
- gokart
- minibike
- tow rope for a sled hill.
- fan-style "snowmobile"
- hovercraft. I don't remember how the airpump part of this worked. there was a plywood platform, and I think the skirt was made from heavy garbage bags?
The tow rope for a sled hill was awesome. Imagine all these kids, love sledding, so tired of climbing the big old hill. What if there was a tow rope, ski hill style? Sure, you have to limit the amount of kids, it breaks all the time, etc. but its still soooo awesome.
Are we talking vertical or horizontal shaft here? While we are on the topic, depending on what you want to do, most lawn mower engines are in a pretty soft state of tune: they give up power for ease of starting, reliability, powerband, etc. A couple quick easy mods you can do for more power:
- check if the valves really line up with the strokes (you can just eyeball this). A lot of lawn mower engines keep a valve open for a big chunk of the compression stroke to make it easier to pull the rope starter, but then they are just throwing power away when the engine is running, at all RPMs. If you just trim the ends of the valve stems such that they stay closed you can pick up a lot of power basically for free (modulo engine start difficulty).
- disable the governor. These work a variety of different ways. You also might need specialized tools to do this, but most lawn mower engines have a governor somewhere. Some are in the crankcase and work like a steam-engine governor but to get to them need a gear puller. Some work in the carb and you can figure that out and disable it. This immediately gets you more top end. These are usually set very conservatively.
- Exhaust and intake on lawn mower engines is usually constricted. Naturally, you are quickly going to get into all kinds of actual tuning issues if you start messing with this, but seriously, figuring out a way to make it easier to get air into the airbox and replacing the muffler with a pipe will boost power for the most part. E.g. put a fine mesh screen over the top of the carb and lose the little air filter (i mean, yeah, this will wear the engine but its not like you are going to be riding this engine to work every day)
Do you have kids? Any of these things is great for kids. I don't really know about for adults though. Thinking about lawnmower engines really brings back the childhood memories.
posted by jeb at 6:29 PM on September 29, 2010 [1 favorite]
That said, here are things I've built/seen people build out of old lawnmower engines:
- gokart
- minibike
- tow rope for a sled hill.
- fan-style "snowmobile"
- hovercraft. I don't remember how the airpump part of this worked. there was a plywood platform, and I think the skirt was made from heavy garbage bags?
The tow rope for a sled hill was awesome. Imagine all these kids, love sledding, so tired of climbing the big old hill. What if there was a tow rope, ski hill style? Sure, you have to limit the amount of kids, it breaks all the time, etc. but its still soooo awesome.
Are we talking vertical or horizontal shaft here? While we are on the topic, depending on what you want to do, most lawn mower engines are in a pretty soft state of tune: they give up power for ease of starting, reliability, powerband, etc. A couple quick easy mods you can do for more power:
- check if the valves really line up with the strokes (you can just eyeball this). A lot of lawn mower engines keep a valve open for a big chunk of the compression stroke to make it easier to pull the rope starter, but then they are just throwing power away when the engine is running, at all RPMs. If you just trim the ends of the valve stems such that they stay closed you can pick up a lot of power basically for free (modulo engine start difficulty).
- disable the governor. These work a variety of different ways. You also might need specialized tools to do this, but most lawn mower engines have a governor somewhere. Some are in the crankcase and work like a steam-engine governor but to get to them need a gear puller. Some work in the carb and you can figure that out and disable it. This immediately gets you more top end. These are usually set very conservatively.
- Exhaust and intake on lawn mower engines is usually constricted. Naturally, you are quickly going to get into all kinds of actual tuning issues if you start messing with this, but seriously, figuring out a way to make it easier to get air into the airbox and replacing the muffler with a pipe will boost power for the most part. E.g. put a fine mesh screen over the top of the carb and lose the little air filter (i mean, yeah, this will wear the engine but its not like you are going to be riding this engine to work every day)
Do you have kids? Any of these things is great for kids. I don't really know about for adults though. Thinking about lawnmower engines really brings back the childhood memories.
posted by jeb at 6:29 PM on September 29, 2010 [1 favorite]
Response by poster: They are all vertical shaft, which to my mind, complicates a build like a minibike (I think), and I don't live in snow country, but I'm loving the transportation theme so far. I wonder if there's any decent way to change the orientation of the power from vertical to horizontal...
posted by gofargogo at 7:27 PM on September 29, 2010
posted by gofargogo at 7:27 PM on September 29, 2010
Best answer: I wonder if there's any decent way to change the orientation of the power from vertical to horizontal...
You could use some kind of gear box with a 90 degree input-output, although I suspect that could be expensive. Of course people always want to run a vertical shaft engine horizontally and it can be done, but may not be practical. To do it right you need to pay attention to oiling, particularly adding or improvising some kind of splasher on the connecting rod to fling oil up to lubricate the engine, as well as how parts that got oiled in one orientation will do so in another. And there's the possibility of oil leaking from places that were never intended to be completely and permanently submerged. Might need to drill and tap a new drain plug as well. Carburetor might need to be rotated or otherwise modified to work in the different orientation.
The other issue is vertical shaft engines usually rely on the lawnmower blade for at least part of the flywheel and it might not run satisfactorily without the blade.
Not to be too much of a buzzkill but if you want a horizontal shaft engine it's probably better to just get one.
One project that comes to mind that would be completely workable with a vertical shaft engine is a generator. Pull a car alternator at a junk yard and pick up the car battery there as well. Add a cheap inverter and you've got a source of 120VAC to keep some lights and the fridge going in an emergency.
posted by 6550 at 8:49 PM on September 29, 2010
You could use some kind of gear box with a 90 degree input-output, although I suspect that could be expensive. Of course people always want to run a vertical shaft engine horizontally and it can be done, but may not be practical. To do it right you need to pay attention to oiling, particularly adding or improvising some kind of splasher on the connecting rod to fling oil up to lubricate the engine, as well as how parts that got oiled in one orientation will do so in another. And there's the possibility of oil leaking from places that were never intended to be completely and permanently submerged. Might need to drill and tap a new drain plug as well. Carburetor might need to be rotated or otherwise modified to work in the different orientation.
The other issue is vertical shaft engines usually rely on the lawnmower blade for at least part of the flywheel and it might not run satisfactorily without the blade.
Not to be too much of a buzzkill but if you want a horizontal shaft engine it's probably better to just get one.
One project that comes to mind that would be completely workable with a vertical shaft engine is a generator. Pull a car alternator at a junk yard and pick up the car battery there as well. Add a cheap inverter and you've got a source of 120VAC to keep some lights and the fridge going in an emergency.
posted by 6550 at 8:49 PM on September 29, 2010
I wonder if there's any decent way to change the orientation of the power from vertical to horizontal...
Pulleys work great for this. Watch the fingers; build an enclosing box or guard.
posted by RikiTikiTavi at 3:06 PM on September 30, 2010
This thread is closed to new comments.
posted by DMan at 5:22 PM on September 29, 2010