Mailing List flyrotary@lancaironline.net Message #64022
From: Charlie England ceengland7@gmail.com <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: alternator
Date: Thu, 14 Jun 2018 10:38:13 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
I don't know about everyone else, but I'm not at all concerned about losing the belt. The only times I've replaced a belt on a car in the 30+ years is in concert with replacing a bad water pump or alternator. I do have my 2nd alternator driven by a different belt; it does make sense to make *everything* redundant (also, proper geometry was easier to set up). But with proper preventive maintenance, I just don't see the belt as an in-flight failure risk, similar to my attitude about an AGM battery.

Charlie

On 6/13/2018 10:22 PM, Matt Boiteau mattboiteau@gmail.com wrote:
I'm sitting on the fence with that answer....

If we loose our belt, we don't have a water pump, which means we are landing asap anyways. Certainly we have enough battery juice, that will last longer then the engine over heating. With these new PWM alternators (P-D style regulator, which the RX8 is), they don't have internal regulators to go bad like old style alternators.

I'm really not worried about a backup alt, but that's just me. Maybe 35amps is enough for a primary alt though. Then it makes things interesting.



- Matt Boiteau

On 6/13/2018 10:27:47 PM, Neil Unger 12348ung@gmail.com <flyrotary@lancaironline.net> wrote:

Todd,

                Main measurement is the ID of the stator pack.  I have to have an ID of 2 5/8 inches to clear my cushion drive, Then with modification I may have 1 3/4 inches space between the plate and the cushion drive plate.  Will have to measure.  The harley seems a good price compared to the Racemate.  Neil.


On 6/14/2018 11:29 AM, Todd Bartrim bartrim@gmail.com wrote:
Hi Neil;
  First, my apologies for not answering your earlier question sooner, but it's been a busy week.
I'm not certain which dimension that you were looking for, but with it in place it is difficult to measure anything but the rotor cup.
Those measurements are 6.3" OD on the cup and after I machined a little off the face edge of the cup I was left with 1.35" thickness. Looking back at my report it looks like I had to remove a total of about 0.156 off both sides of the cup to make it fit so it was probably about 1.5" thick originally. At the time I did this I had detailed notes on every possible dimension, but that was some years back.
   Not knowing enough about your PSRU, I can't say for certain which would be a good fit, but from what I can see of the Racemate, while it is a good solution for the purpose in which it was intended as a belt driven waterpump alt, I think if I was to do it again, I would not hesitate to use the Harley style again, rather than pay extra to modify something that is well designed for the other end of the engine.
  But I would not buy it from the local Harley shop ever again as I paid far too much for it. I would use the Compufire #55540 kit with rotor, stator & regulator which can be bought at Amazon.com right now for $197.64 usd.
This would be your most cost effective way to add it in and apparently Compufire is manufactured in the USA. (for those worried that it is a cheap Chinese knock-off)
  As far as machining costs, once again I do not know the details of your design, but with mine the greatest difficulty was in doing it as a one off design. But if I was to have been doing a bunch of them, I don't think the additional machining would be too onerous, but would not be able to put a dollar amount on that work. And of course, outside of machining and parts costs, you've got to cut yourself a little something as profit for this venture.
  Now with that said, to answer your current question if we think it would be worth it, I would say yes. I've been doing a fair bit of ground testing for unrelated issues but as I disconnected my main alternator in order to access oil lines, I've been running on the back-up PM alt only and it is working flawlessly. Even with both working I can switch seamlessly from the main to the back-up with only a slight volt drop of 0.4 due to different voltage regulators.
  It seems like a lot of money, but in my opinion it is better money spent than on a back-up lightweight battery. Of course I won't be a customer since I already have it and my opinion is biased, but while I could list more than a handful of things that I wouldn't do again, this isn't one of them.
  I would do it again in a heartbeat.

Todd

Todd Bartrim

On Wed, Jun 13, 2018 at 4:42 PM, Neil Unger 12348ung@gmail.com <flyrotary@lancaironline.net> wrote:
Group,

                      Have done some investigation into mounting another generator on the cushion drive and I think it is possible if I use the Racemate rather than the harley.  Cost appears to be similar but the dimensions of the Racement seem more adaptable.  I will have to alter the cushion drive to fit, but that is simply an annoyance at this stage.  Guessing the cost involved it looks like $350 for the generator and regulator, plus possibly an additional $200 for machining making an additional $550 USD for the generator.

IS this cost effective??  You only can answer this for me.  The generator puts out 35 amps.

What say you all?

Regards.  Neil

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