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Generator/Alternator Drive

Posted by Peter Brow 
Generator/Alternator Drive
December 27, 2008 05:36PM
I have blueprinted/component-sourced a toothed-belt ("synchronous belt"winking smiley step-up drive from a crankshaft extension shaft to an aircooled-VW 12V generator. This is for a direct-drive, engine-on-axle steam automobile, with very low electricity requirements.

I am wondering about using a modern automobile alternator instead. These are cheaper, lighter, and more compact, and I have been told that the controller is usually built-in. My question is, would there be any problem running a modern automobile alternator in the reverse direction -- only briefly, occasionally, and at relatively low rpms -- when the car is in reverse?

Peter
Re: Generator/Alternator Drive
December 27, 2008 06:17PM

Cooling fan is designed for one direction, (not a problem for short term use).

Alternator will put out regardless of direction of rotation.


Best,
Scott
Re: Generator/Alternator Drive
December 27, 2008 07:44PM
Hi Peter B,


Im guessing, that you want a no-nonsense DC genny.

I would not go the route of auto alt, self exciting or otherwise.

State expected rpm range, and power output in watts. For example, 12volts at 10 amps is 120 watts.

I have referenced something here on the forum before, called a dual rotor PM alternator,using a bridge rectifier to convert to DC. The physical size of such an alt is, about 12inch diameter by about 3inch thick. The magnets, 24 are needed, cost close to 300 or 400 bucks something like that. These type of machines can make 2000watts comfortably. Generally they run at very low rpm, like under 1000rpm.

If your running over 1000rpm, an auto alt may be a good choice in that case.

Let me know, if you want more info on the dual rotor (wind)genny, I can provide some good links, im pretty knowledgeable about the thing. Its all open-source stuff.


Best


Jeremy
Re: Generator/Alternator Drive
December 28, 2008 12:26AM
Thanks Scott!

Jeremy, I don't need more than about 25 amps/12-14v max. Any higher capacity will probably just go unused. Less might be OK, and allows less draggy drive, if I could find a smaller (motorcycle?) alternator/generator. 0-1200 rpm range w/o step-up drive; 0-7200 rpm with a 1:6 step-up. At one point I considered putting permanent magnets on/in the engine drive gear and mounting stationary coils on the engine frame.

Peter
Re: Generator/Alternator Drive
December 28, 2008 06:10AM
Peter
I used a Delco set up to generate at a low alternator RPM as it was driven off the rearend of the Stanley. At ten MPH I got 30 amps from it and more as the car increased in speed.
On my marine engine in my 35 foot boat I used a Belmar marine alternator that was used for low RPM single cyl diesel, at 200 engine RPM it put our 40 amps



Re: Generator/Alternator Drive
December 28, 2008 11:26AM
Peter,

If you rewind an alternator stator with wire 3 gauges smaller wire, the rpm is cut in half to reach charging voltage. The amperage is limited by the wire size, so make sure the alternator is big enough to start with. Three sizes smaller is 1\2 the area, so a number 14 AWG wire is half the area of 11 AWG.

Three wire sizes will effectively double the voltage and cut the current in half, of course the wattage is equal.

Check the alternator you have now to see what rpm is required to reach the desired voltage, there can be considerable differences. Remember when testing without a regulator a alternator can achieve over 100 volts.

Peter Heid
Re: Generator/Alternator Drive
December 28, 2008 12:50PM
Hi Peter B,

Ok, thats much easier.

"Jeremy, I don't need more than about 25 amps/12-14v max. -PB"


Do you have a diameter of flywheel on this engine that you prefer?

Making 350 to 400 watts is no problem with an axial flux alt. At 6 in diameter you should only need 6 mag's per rotor, that s a total of 12. You would have to cast your own stator(in polyester resin), but the system would work like a magneto. If you did not load the alt, it would free-wheel. But rpm is pretty important, in order to figure wire size and number of turns per coil. In cases of fast rpm,(over 4000rpm) you shound use a technique of 'wire in hand' to wind your coils(this works well at low rpm too). This technique will eliminate hysteresis loss in the coils themselves, since 2 or 3 strands of thinner gauge wire are wound, instead of a single thicker gauge wire. This is only important because its a PM type of alt.

I would still like to know your intended rpm range.

-edit- ok, so 0 to 1200 off of the crankshaft, that's no probem for direct drive, you will not need to overdrive to 7200rpm, to make the exact same amout of power in watts. Sorry I missed that(1200rpm crank-speed). But, do let me know your prefered flywheel diameter, at 8in dia by 1.5 in thick you could make 400w constantly.-



Best



Jeremy



Edited 1 time(s). Last edit at 12/28/2008 12:58PM by Jeremy Holmes.
Re: Generator/Alternator Drive
December 28, 2008 07:06PM
Hi Rolly,

That's the stuff! Did you use a stock 735 generator drive pinion? 30 amps at 10 mph, wow. Neat steamboat too.

Hi Peter,

I know of a good rewinder, yes it would be nice to cut the rpm/drive ratio. Rewinding it myself is a bit much. If it burns out it would be nice to just drop by Pep Boys for a cheap/quick replacement. Like Harry, I'm consulting outside expertise on things electrical. I'm designing the mechanical side right up to the alternator, then the Electrical Dept here at Brow Motors takes over. smiling smiley

Hi Jeremy,

8" diameter x 1.5" thick fits. It would be extremely nice to just stick a rotor on the 0-1200 auxiliary pto shaft, with no gears, belts, etc at all. Cast polyester is right in my fabrication comfort zone, though I'd prefer epoxy if encasing coils is involved. Cheap doesn't always pay. Depends on heat factor of course. Coil winding and fundamental electrical engineering are pushing things -- "don't build what you can buy" sez Jim, and I'm inclined to agree -- but I will run the idea past the no-nonsense professional Electrical Department.

What is the deal with the dual rotors? Coil(s?) in middle, magnet wheels to either side? Any web links I can check out & forward to "Electrical"?

Peter







Re: Generator/Alternator Drive
December 29, 2008 11:09AM
Hi Peter,

Here's a good link to a website that sells some kits. Ed is a very knowledgable guy. All the other links that I could find were for 2000 and 3000watt machines. This one has a 500watt model. I encourage you to email Ed, and discuss your application with him, Ive spoken with him before. I think he would be interested in the application.

[www.windstuffnow.com]



Best


Jeremy
Re: Generator/Alternator Drive
December 29, 2008 04:29PM
Hi again Peter,

I figured I would add why I think this is a good generator for a steam engine. First off its an inherently low rpm unit.

The reason for the dual rotors is to complete the magnetic circuit. Since this is what's called an 'air-core' it does not use an iron core to concentrate magnetic flux. This is generally compensated for, with this design, using as small as possible 'air-gap' between the rotors. An example would be 1/2in to 3/4 inch. The rotors should use neo type magnets, not ceramic. The stator that houses the coils is fixed.

Since this is an air-core type of genny/alt, it does not 'cog'. Meaning, as its turned, with no-load, it does not feel 'lumpy' as you rotate it. Generally this lumpyness is always encountered with a permanent magnet(PM) type of generator(frequently with iron-core units), or even an auto alternator that has power to its rotor.

These type of alternators(air-core) are preffered for wind-turbines, as they will allow start-up rotation in low winds.

As the genny is rotated to speed, a target 'cut-in speed' is engineered into the winding, once cut-in is reached the genny will start to make power. The load and output of these things is quite linear. And rotation can be reversed at anytime with no adverse effects, since a semiconductor rectifier is used, versa brushes and a commutor.

I would figure a 'cut-in speed' of about 150rpm, for your application, depending on your winding arrangement, you may still have to use a regulator to control things with voltage as you approache 1200rpm. This is really no problem as you can use a standard boat outboard-motor, voltage regulator. Just find any regulator that makes 25amp at 12 to 14 volts dc, using a flywheel with PM's.

As you get farther along, your going to see that since your operating at a relatively low-speed, single phase is most likely best for charging a battery.(most outboard volt regulators are intended for single phase, this is because they rev to 5000rpm) You can opt for more phases which will bring-up the integrity of your output waveform at lower speeds. In general 3-phase to the rectifier is prefered. Also more than 3-phase can be used. With 3-phase your going to find coil winding arrangements like 'star' 'wye' or 'delta', for phases greater than 3, star can be used quite easily.

Once you have the DC output from your rectifiers, you could also look into simple 12 volt regulators on the 70's thru 80's vintage cars. This will be easier to manage if you run multi-phase, which is preffered for good quality output DC power. Incidentally, most auto alternators are infact, 3-phase wired in delta. Just remember the rectifier converts to dc from ac, and the regulator is something different. There are many stand-alone 12volt regulators out there, one will be needed no matter what you choose, unless its built-in like a modern auto alt. If you have an old generator like you describe at the top of the post, you will most likely still need a regulator for that.


Best


Jeremy
Re: Generator/Alternator Drive
December 30, 2008 05:55PM
Hi Jeremy,

Thanks for the extra information. I'm juggling several things at once, and will be looking into it soon. It sounds like a great alternator for this application. No brushes and simplest/ruggedest-possible low-rpm direct drive are really big advantages, good thinking there Jeremy. Need to figure out the build job first. If it's a big enough shop project all by itself, that might tip the scales the other way. Bearings, mounts, etc, are already there, though, because the aux drive shaft will also run the pumps.

For the VW generator, which looks very workable, yes, I'd use the matching VW regulator box. Those can be located in a protected area. In later aircooled VWs it was under the rear seat. Very reliable; I've never had generator or regulator trouble with the 12V VW/Bosch system. 6v was a different story. One downside is that in stock form, this depended on the engine cooling fan for cooling airflow. On a steam car axle, a small custom cooling fan might have to be added. Score another one for modern car alternators there. On the other hand, a fan might not be needed, since it would not be in a hot engine compartment.

There are wee shrimpy alternators to replace the original generators in aircooled VW engines. Extremely lightweight and compact. More amps and cost. Also a slightly oddball "to order" item rather than a Pep Boys pickup. Hoist one of these in one hand, and the original generator in the other hand, to find out one reason why they use alternators instead of DC generators in cars nowadays.

Neodymium/iron/boron magnets, whew. Take one out of its box and it flies across the room to hit the steel file cabinet. WHACK! Now where did I leave that crowbar? Oh, it stuck to the magnet too. LOL

Peter
Re: Generator/Alternator Drive
January 10, 2009 01:21PM
Is anyone making a new Generator/Alternator drive? Most people mention to me that if I run and alternator, be sure the change the orginal drive, as an alternator will have more stress on it.
Re: Generator/Alternator Drive
January 10, 2009 01:39PM
I know steam engines & high revs aren't usually mentioned in the same breath, but this graph shows an alternator that's good for about 95% power delivery all the way from 6000 to 18000 rpm. There's some good stuff on this thread about shipping the power at low revs by providing many cycles per rev to avoid the step up gearing power hit. What about this, and take the step up gearing hit? Lear turbines excepted!

[rb-kwin.bosch.com]

Greg
ben
Re: Generator/Alternator Drive
January 10, 2009 07:31PM
The old pinion is 12 teeth,i think,,,,anything less than 15 is an odd an profile tooth,,,Cut with std cutter for 15 teeth,,then set over to left,,shave a bit,,set right ,,shave a bit more,,to get a "workable " gear,,,Also the old gear was RAWHIDE i think,,to keep it quiet,,not ideal,,BUT it worked for years,Not pos of the details,,I have not done it myself,,,,Hey,,what happend to MY share of this Global Warming thing,,,it was -10 at 7am today,,ahhh but it was dry cold,,haha,,Ben
Re: Generator/Alternator Drive
January 11, 2009 08:50PM
The generator drive pinion gear was made out of phenolic fiber. Interesting thing is that one Stanley owner made a replacement gear out of aluminum and it was quickly eaten up. He replaced it with a phenolic gear and it has worked happily ever since. I too would have thought that an aluminum gear would have been a better choice.
ben
Re: Generator/Alternator Drive
January 11, 2009 09:17PM
Alloy doesn't like to slide,Was it hard ally??,,,Brass or bronze probably better,,Are you sure of the phenolic ,,seems i remember rawhide gears in the book,,,with brass end plates,,,We'll have to ask Walter,,I think he made one on the index head,,Cheers Ben
Re: Generator/Alternator Drive
January 11, 2009 09:18PM
Phenolic fiber ... Micarta? Garolite CE & LE are the same stuff ... all listed as "silent gear" materials, usually in combination with a metal gear. Rawhide gears need metal side plates for support and have oil & moisture problems, unlike Micarta ... too bad the machining is a hassle ... how long do these pinions last on the road?

Peter
Re: Generator/Alternator Drive
January 12, 2009 08:36AM
I have worked with many of the Stanley phenolic generator drive gears and I haven't seen any made out of leather as of yet. I even worked with Jay Leno under his Brougham to remove his stripped out phenolic drive gear so that a new gear could be made. He had an alternator installed in his Stanley Brougham and the gear took a powder with in the first 20 miles. As far as I know, the generator drive gears should be good for at least 40,000 miles if not abused. My 1922 Stanley model 735B has 17,000 miles on it gear and it's gear still looks like new.


Re: Generator/Alternator Drive
January 20, 2009 11:52PM
Hi Pat,

Thanks! 40,000 miles is better durability than many belts in modern cars. I like the photo!

Peter
Re: Generator/Alternator Drive
January 28, 2009 04:56PM
Peter B.

Instead of rewinding an alternator so that it reaches its charging voltage at a lower rpm, you might consider buying a 24 or higher voltage alternator and putting a 12 volt regulator on it. The 24 volt will reach the 12 volt mark at about 1/2 the rpm as a 12 volt unit.

Peter Heid
Re: Generator/Alternator Drive
January 28, 2009 05:56PM
Hi Peter B.,

Couldn't you set a 12 volt alternator to six volts and use a voltage doubler circuit on it? Two sets of bridge rectifiers and a couple of heavy capacitors should do it.

I wonder though about getting enough current out of a slow turning alternator.

Best Regards, --- Bill G.
Re: Generator/Alternator Drive
January 29, 2009 12:15AM
Hi Bill and Peter H,

Thanks; I think these ideas, like Jeremy's dual rotor generator, would work. But I don't want to give the "Electrical Dept" any excuse to get into a big project. To begin with at least, I'm just going to bolt on a big dumb Pep Boys generator or alternator with a big dumb high-ratio synchronous drive belt, and leave it at that. Save my scarce ingenuity reserves for working out a key-start vaporizing pilot/burner which shuts off its own fuel automatically if the pilot goes out -- my current "how the heck to do it?" subsystem project.

These might be good electric ideas for another project though -- somebody else's, or my own next project.

I'm wondering if Harry's electric condenser fan is on the right track. The JEGS cat has a $130 bolt-on 10 amp 12vdc fan that pulls 2900 cfm thru a conventional finned radiator core. That's what, 1/4 hp? Battery and alternator/generator are already there for lights and radio, making a lot more than 10 amps when you need overload condensing, and it should pull a lot more than 2900 cfm thru a condenser core with like 1/4 the airflow resistance or less. Exhaust backpressure switch could kick it on/off. If it busts, bfd, car still runs fine. "KISS" condenser overload goodbye? 1/4 hp, hmm, I have a 1 cyl DA self-start aux oscillating engine design, cheap & tiny, that could generate that without much steam ... live steam condenser fan anyone?

Peter
Re: Generator/Alternator Drive
January 29, 2009 05:57AM
Hi Bill,

One downside of a direct-drive steam car with a direct-drive alternator/generator is that below a certain car speed you get negligible to no electrical generation. But with a good powerplant design, that might not be much of a disadvantage, maybe no problem at all. My setup for the VW generator was designed to give the same generator rpm at top car speed (80 mph) as the VW generator at engine redline. 6:1 ratio x 840 engine/wheel rpm at 60 mph = 5040 rpm at the generator. At 10 mph generator is turning at 840 rpm. 420 rpm generator at 5 mph. It should start "juicing" at a pretty low car speed.

Equivalent of VW idle would be, uh, 4000 rpm vw redline = 80 mph steamer, 60/80 = 5040/6720, so 4000 rpm Vw = 6720 generator, ~800 idle, = 1344 generator rpm at idle in VW. 10mph/840rpm generator = 16mph/1344. So the generator would be at "VW idle equivalent" speed at about 16 mph. At that point it will definitely be generating. Probably some juice at lower speeds.

How much road time will I spend driving below 16 mph, and how much electric will my steam car really need during that time? Not much either way. Probably the only electric things on my car will be the lights and radio. With a deep-cycle battery, those could run for hours with the car stopped and no generator. In a pinch, jack up one rear wheel and crack the throttle. Probably never needed.

I have considered making a length of OTS Acme thread rod, a big nut, and a ratchet wrench into a frame-mounted, driver's-seat-operated jack to raise one side of car (both wheels, Old Bug style). Row the under-dash lever to raise wheels, set parking brake lever, disengage parking brake on the raised side (easy mod), and crack the throttle. You could even do this when stuck in an extended traffic jam, without getting out of the car. Put another such jack on other side for easy tire changes and safe working under car. Way cheaper/easier than an engine clutch, no car shake either, and safest/securest car jack possible. You'd never lose the jack either. Gives a whole new meaning to "carjacking".

Imagine sitting in your toasty-cabin steam car at the South Pole all night in an 80-below blizzard with the headlights on, hot java perking in your cigarette-lighter coffee pot, and Van Halen blasting on the ground-pounder sound system. Everything charged, pumped, hot, and running. When that penguin finally wakes up and switches the manual stoplight to green, crank 'er down and burn rubber outa there. Toss him a shrimp from your electric grill as you pass. All this with a Stanleyoid engine/axle and a cheap jack. And no clutch.

Peter





Edited 1 time(s). Last edit at 01/30/2009 01:32AM by Peter Brow.
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