weedwhacker question

deacon

deacon

minor bike philosopher
Okay
I have used weed whackers previously as friction drive motors. I had less than perfect results due to vibration problems. But that is not todays question.

I plan to build a DIY generator using a scooter motor, as a generator, a #25 chain, and a weed whacker engine. I plan to mount them both together. I am first going to try doing it eliminating the batteries completely. Run the electric drive of the bike directly from the generator. I read that diesel locomotives do not run from the diesel engine. That engine turns a generator which powers an electric motor. The reason is so that the power can be applied to the drive wheels more precisely than any clutch could. If I can make this thing work, there would be no need for shifters or gears. You do not need them on an ebike if it has enough power. If I can't get it consistant enough then I can at least charge the batteries while I ride to increase the range a bit.

For it to work even a little consistently I need the weed whacker to turn the motor at pretty much the same speed all the time. I'm not sure that a weed whacker is capable of that for say thirty minutes at a time.

I don't think turning the scooter motor will be much more strain than turning the cutting head in a weedy lot. However I wanted to get your opinions.

http://i36.tinypic.com/15pk605.jpg

I was at wallymart this morning and found a 25cc blower for 68bucks. I wonder if that will turn the scooter motor fast enough. I wont need a clutch but maybe an electrical switch to interrupt the current flow to the bike motor.
 
That all sounds feasable. I used to run weed wackers for 6-8 hours almost nonstop when I did lawnscraping for a living.

The only reason for not doing it that way is the loss of energy you could have by just running the bike right off the weedwacker.

But that's no fun!
 
BTW- My 7th grade science teacher told me that gas/electric hybrids, and cars/motorcycles that use this power set up were never to be! I wrote an essay on making a hybrid in 1976 or so, and the teacher laughed out loud and made fun of me in class for suggesting it!

I wrote it based on the knowledge that locomotives ran that way already, my idea was to add a storage battery as a "buffer/reserve."
Der.
 
Hi Deacon, (are you still a deacon?)
I am doing exactly what you propose except I have tied a wacker to an alternator, with a rubber hose, and direct drive will not work - the wacker just labors to run the drive motor without any load.
If you gear it down with a ratio that will get the wacker into it's power band, I think it will work fine.

I have electrified my mountain bike and it works - battery power. The next step is to drive a 450 watt motor tied to the 250w motor driving the bike, the alternator deal is replaced with a scooter motor. I have a nice wacker (the one in the experiment) BUT it would require a special output shaft and bearing. The wacker has a clutch (big plus but I don't really want to deal with the special shaft or the needed rpm screaming away back there.
I have been going over what engine to use for a while and I settled on a Techumseh 2 stroke from a Toro snowblower. The same thing I put on my 6 hp 24 inch FS bike.
The toro can be driven with a belt one to one or whatever pulleys I come up with- it will be just loafing along, wheras the wacker motor will have to be doing over 5000 rpm when geared 2 to one to obtain the 2600 rpm of both the drive motor and the "generator" motor.

These Techumseh engines have a 5/8 keyed output shaft, are REAL well made (though real old right now). They weigh 10 pounds and require a remote gastank and a muffler and making a tab on the carb to take an idle stop. Oh, they mount on the side. The wacker motor I have is 5 pounds.
Don't know how much snow you guys get down there.
4 of these old Toros are on Craiglist here in Buffalo right now for $60 or so each. Of course, with 90 inches of snow a year, we do have snowblowers.
If you can think of any other 2 stroke that is adaptable readily, please post it.

I plan to do a complete posting on my bike when it is done.
 
Bikeguy Joe said:
BTW- My 7th grade science teacher told me that gas/electric hybrids, and cars/motorcycles that use this power set up were never to be! I wrote an essay on making a hybrid in 1976 or so, and the teacher laughed out loud and made fun of me in class for suggesting it!

I wrote it based on the knowledge that locomotives ran that way already, my idea was to add a storage battery as a "buffer/reserve."
Der.
Click to expand...

Nice of yer teacher to sorta "forget" alla those WWII diesel/electric sub fleets too lol
 
I like the concept and have to admit that I'm curious. However, it doesn't really matter how much a locomotive weighs and I think it does matter with a mb. I don't see how the power loss due to the inefficiencies with mechanics will benefit you any here. Especially if you plan on not using batteries.
 
Well we are just going to have to see what it does. I'm just not theoretical enough to know what to expect. I expect to use batteries to be honest because the generator (scooter+weed whacker) will not put out enough amps to run the bike up a hill. I expect that the best I can do is increase the range of the bike's batteries.

First thing is to set up the whacker engine to the scooter motor and determine the output in volts. I am thinking a 500 watt motor will put out about 15amps at 30v (if I can get 30v out of the whacker/generator) or so. I am going to run that as a parallel circuit with a set of 7ah batteries. They are old so I feel more comfortable if they blow up lol...

What I think will happen is the drive motor will draw amps from the combined pool available from the generator and the battery pack. Any surplus should go back into the battery.

In other words I hope it will draw less total amps from the batteries than it would without the generator, and when I am rolling downhill, I hope it will be replacing some of the amps it pulled out of the battery while going up hill. Whether it will or not remains to be seen.

The drive motor is independent of the generator motor. The generator motor will just pump power into the battery/drive circuit. If that doesn't work then I will have to try something else I suppose.

If I can pull this off it will add less than a hundred bucks to the cost of the power system and allow the use of less expensive sla batteries. Lithium batteries scare heck out of me. Too many cells with to much electronics to go wrong. At least that is how I feel about them at the moment. Not to mention the exorbitant cost.

I am going to run a very inexpensive small WW at first try. Simply because I don't have any idea what it will take to drive the scooter motor at 2600 rpms. When I put the load on the ww it might choke down to even less. If it does, the next logical step would be to get a smaller wattage scooter motor since i have a feeling a small watt motor would turn with less load. That would increase the ultimate output voltage. Another thing that remains to be seen.

I am using a #25 sprocket and chain system because i have five or more feet of the chain and the sprockets laying around. I do have to get a sprocket onto the WW though and that might prove to be a problem. Actually I think I am going to get a leaf blower for the fixed throttle since it will be going along on the trailer or faux trike basket.

I would love to use it without the batteries but I don't think it will work without them. I am lucky in that I have a controller on the Faux trike that will run with either 24 or 36 volts. so I can use either of those battery packs and generator setting if I can get them to work.

Just have to wait and see. I think I found a small light new leaf blower cheap but since I don't drive I have to wait for Ma'ma to get back from playing with the grand kids. yes I could run the faux trike to the store, but it is raining and very cold here today.

PS... I never was a Deacon, just the name of a character in a series of books I wrote... No they never were published.

The other thing is the benefits. Well the friction drive with the big ole scooter wheel is by far the best one I have ever had. That happens to be from an electric scooter. From that I learned that I could run an electric bike. Then I learned that an electric power bike is still a bike in the eyes of the law. It is not a moped. I don't have to wear a helmet or when the registration of mopeds happens, I still wont have to do that.

So then came the understanding that even though I have a heck of an motor drive, it still sucks because the batteries are such garbage. Someone on a different forum said i should just invest in a 700 set of lithium batteries. I am not likely to do that.

The things lithium brings to the table, I think this generator will solve. If I can add amps to the pool and replace amps then the power curve for the power system will be more straight line. That should help with the deterioration of performance as the batteries give up amps. With a little luck it will also increase the range to rival that of the lithium pack. And all with the ability to replace the batteries relatively inexpensively.

Frankly my ebike does something the gas bikes I built wouldn't do. It starts easily from a stop sign at the bottom of a hill. There is no clutch to jerk around and it actually starts to move and help with the pedaling if you want to increast the speed.

One more thing that just might happen with this system though i am not counting on it. If I plug the generator to the battery system, before the engine is running, the motor/generator will turn. That will drag the ww engine around as well. That just might make it an electric starter for the generator... Lol I have no idea what it will do. That is the joy of being so stupid. Surprises around every corner.
 
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I can't speak for the deacon, this build will be an electric bike- legal in NY. My only reason for doing it. if gas were legal, I would do that. I can say that the torque of the motor is amazing- just the opposite of gas.
To delete batterys is totally desirable to me. I can tolerate a little inefficiency.
My bike with the batterys and a very heavy rack (built to hold a Harbor freight 2.5) weighs 64#.
I think it will be just about 70 with an engine and generator (motor).
 
Well what I have on hand is an 18 tooth sprocket that will have to go to the engine. The motor has an eleven tooth sprocket so to begin with it is going to be the wrong way. I need to get the blower and see what I can do. They make all kinds of #25 sprockets and I have no problem piggy backing them with a welder. Well I have no problem conceiving of it but my lack of welding skill is known far and wide.

The 500 watt motor is a bit tight but if it won't crank out enough volts, my first plan is to get a 200 or so watt motor to cut back on the drag. After that I may have to go with different size sprockets to change the gear ratios. I still have to have the rpm up to at least 3000 I think. They say even the smallest whacker will do 7000 with little or no load. So I will just have to see what motor I wind up with and how much drag I have with the generator/motor.

Gas bikes are still legal here but there is a brewing storm... So many people in this economy have opted for the 50cc scooter that they are becoming a regulation issue. A guy who is riding a $500 scooter with no insurance and smacks a BMW is not going to have anything for the insurance company to get. So eventually they will be regulated. Step on will be to make sure everyone who rides one has a driver's license. I still have mine, but my wife and neurologist say, if I use it they will call the highway patrol. I had seizures a couple of years ago. Once you have those on your medical record, they will always be an issue. So for me it's ride a pedal bike or electric bike. Besides which I hate helmets. None is required with an ebike.
 
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I may have stepped in it. I got the 25cc weed whacker leaf blower. I took it mostly apart and I haven't tested to see if it runs yet. I guess if it doesn't I'm in a world of voodoo. I'll probably premix some gas tomorrow before I start cutting up the plastic parts.

The thing is very light weight. The scooter motor will be adding the only real weight to it. I will try to finish the generator tomorrow and test it. Not on the bike but just try to figure if I can get the right voltage since that is the biggest problem. I face. I found a smaller motor I might be able to use if the 500 proves too much for the ww...
 
The end is an outside threaded road with one flat side. It came with a nut and a fan blade with the one flat side. It is 5/16 diameter fine thread.

I have a 3/8 id sprocket I'm gong to weld to a fine thread nut. Then I am going to cut the center from the fan blade. I'm gong to run the nut on the sprocket down until it is tight against what used to be the center of the fan mount. I might put a welding bead on that as well. I don't want to get it too far out of balance but I don't want it working loose either.

The blower parts came off leaving me the motor and housing still attached. I am gong to have to take the handle off and mount the motor positioned so the handle area is on bottom. I am still thinking but I'm pretty sure I can save the motor cover completely. My main concern is vibration.

The blower has a lever that is attached to the carb as a throttle. It is going to be ideal for starting it setting the throttle by checking the meter to get a suitable voltage, then climbing on the bike and let it run while I take off. I decided that I am going to use the battery pack with the generator if it all works out okay.
 
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Just a midday update, as if anyone cared. I got the blower apart, I was able to reuse the crank shaft fan connector after I welded it to my sprocket. I welded it with just spot weld. The nut will hold it on. I just needed it to stay in place while I tightened it down. I trimmed the case so that it sat pretty flat on the board. Then I trimmed back the blower pieces so that I could reuse the plastic mounting plate. The motor sits flat on the wood after a little trimming the mounting plate should just be to keep it from rotating.

Oh yeah the engine started up just fine. So I have a working engine, with a sprocket to fit my scooter motor. I also have it mounted to a board and ready for me to mount the scooter motor beside it. All in all I got a lot done before 1pm.Next I have to mount the scooter motor and set up the chain. If I get all that done before dark and I should easily, then I will do an output test on the whole thing.

That is the only test that really matters. I'm afraid I did all this and can't get the proper voltage from the generator. If I do then I still have to worry about the number of amps that will be flowing. I know all the electronics guys are sitting around waiting for the whole thing to explode on me. Rofl. I plan to take it in front of a neighbor's house. The one who owes me money before I test it on the bike. It would be a shame to waste a perfectly good explosion.
 
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experiment finished and I failed miserably lol...l.. At least I know now what it will and won't do. A 25cc ww engine will turn a 500 watt motor fast enough to produce 100 volts. It will also break the sprocket off the drive shaft of the engine. The throttle is not sensitive enough to maintain any given rpm rate. I could set the throttle and watch it vary by ten volts.

Now the motor won't start which is probably something to do with pulling a 500 watt motor instead of a fan blade. Either way that is a project with a lot of promise for someone who has a lot more experience with Electronics than I do. In my case it was a waste of my time. Except that I had nothing else to do with the time. Of course now I have a 25cc motor that may or may not ever run again.

I may wait a while then revisit this experiment with a smaller scooter motor to act as the generator. However at this moment I have no plans to pick it up again for a while. I might see if I can get the motor started one day soon. It seems to have compression I probably should check to see if I burned out the magneto. When it gets stone cold it might just start. Of course now I have no real use for it.
 
On my 25cc Homelite blower, there was a spacer that went over the motor shaft. After taking the blower fan off, I had to put the spacer back on the shaft and torque it down with the nut that used to hold the fan on, at the threaded end of the shaft. The nut and spacer are what hold the flywheel on.

That's the way mine is made, anyway. Just thought I'd mention it.
 
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