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wrjjrs@aol.com wrote:
Fred, and Group,
FYI Mistral has decided to do the starter generator for weight savings too. Francois mentioned it in a recent post.
Bill Jepson
-----Original Message-----
From: Fred Osborn <fosborn@infowest.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Mon, 9 Jul 2007 9:36 am
Subject: [FlyRotary] Rotary Engine Electrical Power
Ernest Christley wrote 7/6/07, Message #38256, Re: Ford EDIS: 4.7lbs isn't a great weight saver compared to some of the lightweight alternators out there, but I don't think they're usually weighed with the mounting brackets and pulleys from the engine side of the belt. We can get more weight savings if we let the flywheel that we already have double as a rotor. I agree, the thought of the rear counter weight whirling around just stirring air while doing it's balancing function really bugs me. A non-magnetic replacement carrying permanent magnets and surrounded by a set of coils would just cost the added weight of the coils. How much power and reliability do you want? Those coils together with a set of power switching electronics and a position sensor could become a starter/generator. I'm not all that excited by the use of permanent magnets for various reasons. They do have the big advantage of simplicity. Eventually, the goal should be the use of an Integrated Starter/Generators (IGS) such as those being introduced in automotive applications. The power switching devices required are now state-of-the-art and in volume production for a wide variety of switched reluctance motor applications. I have given serious consideration to working this area myself but the recent installation of 3 more stents added to my previous 3 have caused some equally serious consideration to "slowing down". Fred O. Some of the proposed IGS I've seen were based on PMs. Note that the PM we're talking about aren't your grandfathers lodestones. Pull the harddrive out of an old computer to get at what I'm talking about. Spinning 8 stacks of 4 of those sucker at 3 to 6 thousand RPM will give you one heck of a flux field to work with. I'm waiting to get some parts back from a machinist friend that is doing some work for me, but there shouldn't be a problem with fitting a set of coils inside the cup formed inside the rear side-housing and covered by the flywheel. Fitting the rear of the flywheel with an appropriately sized ring (cut from a steel pipe) won't be hard. It'll be centrifugally balanced, so a few large tack welds will keep it in place.
Using the counterweight as a rotor is an interesting idea. An aluminum casting drilled through longitude would hold a handful of the 1/2" button magnets, enough to equal the counterweights moment. MPJA sells the magnets for about $1 each. Building the coils could be as simple as buying a bag motor wire from RadioShack. Just wire the spools together in a Delta configuration to handle the current. The voltage is likely to be way to high, but it's AC. Pass it to a transformer before handing it off to the rectifiers. 40A continuous won't be that difficult.
But I could very well be wrong. The plan is to test it on a drill press before feeling confident that it is anything but a pipe dream. However, until such time as I may provide any useful, I present the following PDF for your amusement.
http://www.scoraigwind.com/pmgbooklet/itpmg.pdf
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