av8tor1977

My Feedback: (6)

Captain... One could use a circuit like above, and use a small brushless motor as an alternator. This generated current could be used to power any type of ignition you wanted to use.

It's off your original idea of a small home made magneto, but a similar line of thinking and interesting none the less.

AV8TOR

carlosponti

My Feedback: (1)

the guy with the lite weight flywheel might have been successful had he not added the lightening holes where the magnets were. fill in those holes and it would have been strong enough. the lightening holes on the light side of the flywheel would have been fine. he should have played with the design a bit to handle the stresses.

captinjohn

AV8TOR... Yes that looks like a very good system for the larger engines, and airplanes. It would keep a small battery charged all the time and that same battery could energize a CH or RCxcell CD ignition for start and running.. Or about any CD ignition of your choice. The small brush-less motor used for a alternator could be driven by a small prop and eliminate a belt drive to spin it. lots of possibilities. I think we are at a point of 2 separate systems though. I think both should be further worked on and developed. one system with alternator and various components and the other system just a bare bones mag like we have many of now but would weigh about 1/3 the weight or less if possible. We need more ideas for both. Please anyone out there that even knows of some person that has talent in these fields...tell them what we are trying to do. Thanks Very Much Capt,n[X(]

Bigboat

You don't need a battery if your using a altinator, you only need a battery to start the engine.....or you must have enough rpm at start to activate the altinator.
If the engine running you can disconnect the battery, the altinator will do the (battery) job.

captinjohn

Bigboat, I see what you mean. If a battery was needed for more easy starting, you could have a battery input jack on fuse for starting. I am sure the electrical power needed for idle would be there once engine was running. What do you think is the best way to spin the alternator? Belt? Or?? Thanks Capt,n

Bigboat

Take a look into your car.......they use almost a belt to drive the altinator.
Why, it's a easy construction and you can place the altinator anywhere you want.
You can drive with your car without a battery......not (long) without a altinator.
It's the same principal you can do with the (mini) bruslessmotor on your engine.

captinjohn

Well ya!!![] Just thought you may have more detailed ideas, like about what size pulleys so the PRM of brushless motor will not self destruct and what kind or type of belt to use? [X(] I thought you just might have some links to parts that may work. Guess not[:-] Capt,n

Bigboat

Maybe you can here your awnsers
http://www.rcgroups.com/forums/showthread.php?t=808935
http://mysite.verizon.net/vze49gsg/id2.html

captinjohn

BigBoat, I knew you would come up with more. Hey I read a lot on that link you provided. Now I got to go back and find out whats in that little "black box" Hey...if it works with-out any radio interference in a heli...it should work on about anything. Did I mention No worry of battery pack going dead!!!! Capt,n P.S. Thanks Again for that extra data.

Bigboat

The little blackbox will be a goldcap, lookslike a capacitor and can store some Voltage/current......just enough to make a safe landing.
A bigger Goldcap can store more energie.
This show you wat Goldcap are http://www.alibaba.com/product-free/...Capacitor.html

captinjohn

Here is a couple of photos...looks like something flat & round in the shrinkwrap! Capt,n

Bigboat

At the left the brusless, into the middle the diodebridge and right the electronics.....and if you look good to the shrinkwrap a round *thing*.....thats the Goldgap.

captinjohn

Wow...that photo is 3 years old by the date on it. I bet there is several improvements since then too! Capt,n

Bigboat

NOP, the principal is still the same only the brushless are better.
Now you can buy a very small engine with a lot of power becourse the use neodeen magnets.
A steppermotor is a old brushlessmotor, steppers use ferritmagnets and they are big.

captinjohn

I got a Scorpian electric out-runner on my E-flight cap232. I put new bearings in it and you are right...the pull on those magnets are awsome. You got to be carefull putting them back together so the pull of the magnets does not let rotor slam in place! Capt,n[X(]

WRK

My Feedback: (2)

For a completely self contained unit it would be hard to beat the Walbro unit, the down side is weight.

A battery powered CD unit that is on all the DA's etc. is probably as light as you can get with battery included in the total weight.

A generator powered CD unit could be worked out, you are then providing 5 to 6 volts regulated to power a CH/DA type system.

You have to know the energy you need to power an ignition system so that you can figure out how much generator (size weight) is needed to do the job.

A CH type system uses about .5 to .6 amps at say 6 volts that is 3.6 watts, the generator or alternator + regulator needs to provide this at starting speeds. The generator/alternator/regulator needs enough diameter or speed to provide this power at cranking speed.
(larger diameter equals more magnet surface speed which equals more output for a given RPM)

The size of the generator or alternator and it's weight will be governed by the starting energy needed, it's weight will also be determined by how rugged it needs to be and how much engine vibration it has to stand. You could go with a high speed generator or alternator using belts or gears or you could use a direct drive unit that is larger in diameter to get the magnet surface speed high enough to provide the starting requirement.

A possibly lighter overall unit might be made by using a small battery that is charged by the generator/alternator, the battery is used in starting and is continually charged, once the engine starts, by the generator/alternator, so the gen/alt charges the battery and the battery powers the ignition. The advantage here is that the generator/alternator can now be smaller since it does not have to provide starting energy since we are stating essentially on the battery. This type of setup would probably end up being lighter than the Walbro unit. the biggest challenge would be finding or making a alternator or generator that is physically tough and easily adapts to the engine.

This means we are taking something like a CH ignition + a small battery say 200 MA capability + a regulator + a generator/alternator. The regulator will have to be a special in that when the engine is running at high speed it will have more than enough output to run the ignition at lower speed and it's output voltage will want to rise to quite a high voltage, this must be delt with by the regulator. Possibly a small version of an automobile alternator might be used where the regulator directaly governs the output of the alternator, this means that rather than throwing away the extra high speed generated energy you partially shut off the alternator and never allow it to provide a higher voltage than needed at any engine running speed. This type of alternator is more complicated so this must be taken into consideration.

It may also be possible do have an alternator + regulator system that provides power to the battery at medium to high engine speeds and you use the battery to run the engine at low speed when the alternator/generator output is not high enough, then you could use a simpler regulator
set up and with the right size battery you would be charging most of the time so the battery should never go dead.

Hope this makes sense.

Bill

TFM70

Bill
You make perfect sense. When this thread was started by Cap'n, it went like this.
"I was wondering why not much is being done to develop a lite-weight mag and be done with batteries & Glow on say 20cc & bigger RC engines. I drew up a sketch that popped into my mind and you can "kinda see" what I am posting about. I wish more of the good talent out there would help us all (working together) to develop such a lite weight mag. I think the main rotor could be made from about 1/8 inch plate aluminum attached to a hub or machined from much thicker piece of aluminum. A real lite coil must be found & magnets that could be attached to the rotor. With the pic-up coil facing back-side of rotor a more narrow set-up would be good. The pick-up surface would be flat instead of curved to match new flat surface. Please add any ideas and data to this thread. Here is sketch below! Capt,n "
My view of what he was wanting was a small light weight magneto and not need batteries. He didn't say it, but but you stated that (larger diameter equals more magnet surface speed which equals more output for a given RPM) which kind of eliminates a small diameter magentor wheel.
If a method could be found to connect a booster battery into into the magneto primary coil circuit for starting only then what Cap'n wanted would be possible. I have connected a battery into a very old magneto that used points and it made the magneto fire at very very slow rotation. I don't know whats in the solid state modules used in the magnetos today so I don't know if it would be possible.
If you could it would eliminate the alternator, regulater, CH iginition, flight battery and all the mechanical hassel of connecting an alternator to the motor.

mmattockx

Isn't this what the CH Jump Start does?

Mark

Bigboat

The problem with *jigsaw* engines is, they need the heavy wheel.
You can't lose the weight of the magnetwheel, becourse your engine wil stopped at low rpm.
The weight of the magnetwheel push the engine true the TDC.
You need also the (heavy) weight of the magnets to get enough power into the coils at low rpm.
With a CDI you don't have this problem, you get the power from te batteries.
Only if you don't have enough power from the batteries to empty your tank, you can use a generator.

captinjohn

The prop is kinda a flywheel if you need fly-wheel effect. I am reading all this...but got to go now bcause friends are coming soon. Later, Capt,n

TFM70

Mark
You are right. I wasn't familar with the Jump Start and it states that you must have working magneto. But it is only available for a few engines and the one I am interested in (ECHO) is not one of them.

Rob
There are lots of recip. engines running without a flywheel.

mmattockx

Guys, I have a question. This comes from a mag engine rookie, no experience with anything other than EI. When a mag engine is converted to EI the weight usually drops 10oz or so. At least that is what my G-62 loses as converted by Ralph C. This does not consider the weight gain due to the ignition box or the battery (I don't think it includes the ignition, anyway). So, how much of the weight lost is due to a fairly heavy flywheel and how much is the magneto portion with magnets, coil, etc.? Does the EI not use the same coil as the mag did?

I am just wondering, because it seems to me a fairly small wheel and light magnets (rare earth ones should be up to the job and weigh squat) would save similar amounts of weight and avoid the ignition box and battery. Am I nuts?

I am looking to convert a Poulan 46cc and not having to buy an ignition would be nice. Assuming we can get a mag as light as the EI version ends up with ignition box and battery.

I PM'd the cap'n last week and offered my services for analysis of a lightweight rotor if it ever gets to that point. I am a mechanical engineer and do lots of machine design and finite element analysis for work. I can solid model whatever we come up with and ensure it is as light as possible while still being strong enough. So, lets get something sorted out and to the point I can work it up and someone can get one built to test. If I had the Poulan in hand, I would volunteer it for testing, but I don't. Unless someone out there has one sitting in their pile of unconverted engines and wants to sell it to me for a reasonable price...

Mark

captinjohn

There can be 2 ways that may work. One is a super lite-weight mag...nothing else needed or a nice little alternator to supply current to a CD ignition. These CD ignitions can be bought fairly cheap but some people are not going to like the chance of a CD unit going bad verses a simple liteweight mag. We should do both....its good to have a option. What we need is people to help find parts that can be used as much as possible to get the job done faster. Also we need others to come up with any idea that may help. A test unit could be driven by a electric motor to spin the system and see what is going to work. No need to eat fumes and be in the cold garage or outside in the rain. Just mock up a system and see what works. Any Ideas???? thanks Capt,n EDIT to add photo. This is how the rotor could look like (front only) and a high performace magnet could be used on one side of rotor and a blank piece of steel on opposite side. I hope the idea is coming through![X(]

captinjohn

This little brushless motor can be the alternator as shown oh Heli. It could be mounter on a small flat plate and be drive with some osrt of belt? What kind of belt is the question. We need some ideas on that. Also what speed should it spin? Thanks Capt,n

mmattockx

The idea is fine to me. How many magnets are on a normal flywheel? Can we just buy an alternate coil or sensor or whatever is placed close to the magnet, since the existing ones will have a curved surface to match the OD of the flywheel?

Apparently, I need an education on exactly what constitutes a weedwhacker mag ignition. Any takers, in 500 words or less?


Mark