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gregcampbellusa(at)gmail.
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 Posted: Wed Nov 15, 2006 9:18 am Post subject: Vacuum Pad Limitations - Weight & Torque... |
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Does anyone know how much torque the www.BandC.biz SD-20
alternator places on the accessory pad drive? The reason I ask
is because I put one on my TCM IO-550N engine and want to be
sure it is within the limits prescribed by the engine manufacturer.
My engine is described by the "Type Certificate Data Sheet" (TCDS) E3SO.
(This applies to most of the Continental IO-550 engine models.)
For those who may not be aware, the TCDS is the "official" source
of limitations on any Type Certified device that the FAA has approved.
The FAA is the official repository of the most up-to-date approved TCDS
and also maintains the historical records as well. You can find them at
http://www.AirWeb.FAA.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf
Anyway... the E3SO (Revision  Type Certificate says that
my engine's "accessory drives" (aka: "vacuum pump pads")
can each be loaded to 100 inch pounds of torque on a continuous basis,
and up to 800 inch pounds of torque on a static basis. A little ***
note indicates that one drive can be loaded to 160 in.lbs if the other
drive is limited to 100 in.lbs, (or in my case, not used.)
It also states that the accessory drive gear ratio is 1.5:1
so if I'm cruising at 2333 RPM or higher, then the alternator
should be turning at 3500 RPM or higher and able to put out a full 20 amps.
(according to the info at www.BandC.biz for it's SD-20 alternator)
The TCDS also shows that the maximum "overhang moment" of each accessory
should not exceed 40 inch pounds. By checking the specs at
http://www.bandc.biz/SD20REVC.pdf
it appears that the SD-20 weighs about 5.72 lbs and the CG is 3.15"
from the flange, for an overhang moment of about 18 inch pounds.
So far, so good!
It would be nice to know if the SD-20 has a "shear shaft"
to limit the damage in the event of a locked rotor. If it sheared around
800 inch pounds of static torque, that would be great to protect the engine.
So... to my great relief (and no big surprise), the SD-20 doesn't appear to present
any excessive burden to the accessory drive on my IO-550. Thousands of these
things flying around, so I didn't expect that there would be a problem.
############## EXTRA CREDIT ################
The only significant "unknown" is what the "continuous" & "static" torque of the
alternator is while fully loaded at my max-rpm's ?
I'll challenge the electrically gifted on this list to come up with a reasonable estimate
of the torque required to produce 20 amps at 3500 to 4050 alternator rpm.
I can follow it through VxA = Watts, Watts -> HP, HP / Efficiency = Input Shaft HP,
Input Shaft HP / rpm = Force or Torque or something - but I get stuck about there.
Bottom line, I'd like to know Input Shaft torque on a continuous basis
over the range of operating RPM's. (Perhaps it's highest at lower RPM ?)
If it's less than 160 inch pounds, then we're good to hang at least one SD-20 (on a TCM IO-550)
If it's less than 100 inch pounds, then you could conceivably hang two SD-20's -
(although it would take tiny fingers & a small miracle to get them both bolted on & torqued properly! 
########################################
If anybody is considering hanging two of the SD-20's, or has a radically different engine,
you might want to look up your TCDS to find the latest "approved" limitations.
You might find out you have a higher or lower gear ratio, torque limit, or max overhang moment.
Just some thoughts for those who are cautious or curious.
(But I'm expecting answers from the electrically gifted!
Greg
[quote][b]
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rtitsworth
Joined: 16 Jan 2006
Posts: 76
Location: Detroit, Mi
|
| Posted: Wed Nov 15, 2006 10:32 am Post subject: Vacuum Pad Limitations - Weight & Torque... |
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I’m planning on using a similar setup (still building). Thanks for the info.
I have no reason to use anything else besides the B&C SD-20. However, does anyone know of any alternatives?
I was at GAMI in Oklahoma last spring and saw a demo of the Supplenator (30 amp version) see: http://www.gami.com/supplenator.html
However, the like GAMI’s phantom PRISM ignition system it is not yet available (perhaps never?)
Rick Titsworth
Cell: 313-506-5604
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Greg Campbell
Sent: Wednesday, November 15, 2006 12:18 PM
To: aeroelectric-list(at)matronics.com
Subject: Vacuum Pad Limitations - Weight & Torque...
Does anyone know how much torque the www.BandC.biz SD-20
alternator places on the accessory pad drive? The reason I ask
is because I put one on my TCM IO-550N engine and want to be
sure it is within the limits prescribed by the engine manufacturer.
My engine is described by the "Type Certificate Data Sheet" (TCDS) E3SO.
(This applies to most of the Continental IO-550 engine models.)
For those who may not be aware, the TCDS is the "official" source
of limitations on any Type Certified device that the FAA has approved.
The FAA is the official repository of the most up-to-date approved TCDS
and also maintains the historical records as well. You can find them at
http://www.AirWeb.FAA.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf
Anyway... the E3SO (Revision Type Certificate says that
my engine's "accessory drives" (aka: "vacuum pump pads")
can each be loaded to 100 inch pounds of torque on a continuous basis,
and up to 800 inch pounds of torque on a static basis. A little ***
note indicates that one drive can be loaded to 160 in.lbs if the other
drive is limited to 100 in.lbs, (or in my case, not used.)
It also states that the accessory drive gear ratio is 1.5:1
so if I'm cruising at 2333 RPM or higher, then the alternator
should be turning at 3500 RPM or higher and able to put out a full 20 amps.
(according to the info at www.BandC.biz for it's SD-20 alternator)
The TCDS also shows that the maximum "overhang moment" of each accessory
should not exceed 40 inch pounds. By checking the specs at
http://www.bandc.biz/SD20REVC.pdf
it appears that the SD-20 weighs about 5.72 lbs and the CG is 3.15"
from the flange, for an overhang moment of about 18 inch pounds.
So far, so good!
It would be nice to know if the SD-20 has a "shear shaft"
to limit the damage in the event of a locked rotor. If it sheared around
800 inch pounds of static torque, that would be great to protect the engine.
So... to my great relief (and no big surprise), the SD-20 doesn't appear to present
any excessive burden to the accessory drive on my IO-550. Thousands of these
things flying around, so I didn't expect that there would be a problem.
############## EXTRA CREDIT ################
The only significant "unknown" is what the "continuous" & "static" torque of the
alternator is while fully loaded at my max-rpm's ?
I'll challenge the electrically gifted on this list to come up with a reasonable estimate
of the torque required to produce 20 amps at 3500 to 4050 alternator rpm.
I can follow it through VxA = Watts, Watts -> HP, HP / Efficiency = Input Shaft HP,
Input Shaft HP / rpm = Force or Torque or something - but I get stuck about there.
Bottom line, I'd like to know Input Shaft torque on a continuous basis
over the range of operating RPM's. (Perhaps it's highest at lower RPM ?)
If it's less than 160 inch pounds, then we're good to hang at least one SD-20 (on a TCM IO-550)
If it's less than 100 inch pounds, then you could conceivably hang two SD-20's -
(although it would take tiny fingers & a small miracle to get them both bolted on & torqued properly!
########################################
If anybody is considering hanging two of the SD-20's, or has a radically different engine,
you might want to look up your TCDS to find the latest "approved" limitations.
You might find out you have a higher or lower gear ratio, torque limit, or max overhang moment.
Just some thoughts for those who are cautious or curious.
(But I'm expecting answers from the electrically gifted!
Greg
| Quote: | | www.aeroelectric.com |
0123456789012345
[quote][b]
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mprather(at)spro.net
Guest
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| Posted: Wed Nov 15, 2006 11:35 am Post subject: Vacuum Pad Limitations - Weight & Torque... |
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Hello Greg,
It looks to me that the only thing missing in your calculation is hp =
torque (ft-lbs) x RPM / 5252 or torque = hp x 5252 / RPM.
Let's say the alternator is 50% efficient - a very conservative number, I
think.
SD-20 Output Watts = 20A * 13.5V (guess) = 270Watts
with 50% efficiency, that's 540Watts input.
That's 0.723hp (power = 540Watts/746Watts/1hp) - 1hp = 746Watts
Seems like worst case torque might happen when the alternator is at the
lowest RPM - and producing maximum current. The alternator is rated at
3500RPM.
Torque = 0.723hp x 5252 / 3500 = 1.1ft-lb = 13.03in-lb.
Assumptions to be checked:
- My math.
- Shaft load above 3500RPM doesn't significantly increase.
- Dynamic torque load is minimal - I have noticed that when turning PM
dynamos, there are small magnetic "bumps" to get over. I suspect that
the magnitude of these bumps is small, but I don't know.
- Overall dynamo efficiency.
Regards,
Matt-
| Quote: | Does anyone know how much torque the www.BandC.biz SD-20
alternator places on the accessory pad drive? The reason I ask
is because I put one on my TCM IO-550N engine and want to be
sure it is within the limits prescribed by the engine manufacturer.
My engine is described by the "Type Certificate Data Sheet" (TCDS) E3SO.
(This applies to most of the Continental IO-550 engine models.)
For those who may not be aware, the TCDS is the "official" source
of limitations on any Type Certified device that the FAA has approved.
The FAA is the official repository of the most up-to-date approved TCDS
and also maintains the historical records as well. You can find them at
http://www.AirWeb.FAA.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf
Anyway... the E3SO (Revision Type Certificate says that
my engine's "accessory drives" (aka: "vacuum pump pads")
can each be loaded to 100 inch pounds of torque on a continuous basis,
and up to 800 inch pounds of torque on a static basis. A little ***
note indicates that one drive can be loaded to 160 in.lbs if the other
drive is limited to 100 in.lbs, (or in my case, not used.)
It also states that the accessory drive gear ratio is 1.5:1
so if I'm cruising at 2333 RPM or higher, then the alternator
should be turning at 3500 RPM or higher and able to put out a full 20
amps.
(according to the info at www.BandC.biz for it's SD-20 alternator)
The TCDS also shows that the maximum "overhang moment" of each accessory
should not exceed 40 inch pounds. By checking the specs at
http://www.bandc.biz/SD20REVC.pdf
it appears that the SD-20 weighs about 5.72 lbs and the CG is 3.15"
from the flange, for an overhang moment of about 18 inch pounds.
So far, so good!
It would be nice to know if the SD-20 has a "shear shaft"
to limit the damage in the event of a locked rotor. If it sheared around
800 inch pounds of static torque, that would be great to protect the
engine.
So... to my great relief (and no big surprise), the SD-20 doesn't appear
to
present
any excessive burden to the accessory drive on my IO-550. Thousands of
these
things flying around, so I didn't expect that there would be a problem.
############## EXTRA CREDIT ################
The only significant "unknown" is what the "continuous" & "static" torque
of
the
alternator is while fully loaded at my max-rpm's ?
I'll challenge the electrically gifted on this list to come up with a
reasonable estimate
of the torque required to produce 20 amps at 3500 to 4050 alternator rpm.
I can follow it through VxA = Watts, Watts -> HP, HP / Efficiency = Input
Shaft HP,
Input Shaft HP / rpm = Force or Torque or something - but I get stuck
about
there.
Bottom line, I'd like to know Input Shaft torque on a continuous basis
over the range of operating RPM's. (Perhaps it's highest at lower RPM ?)
If it's less than 160 inch pounds, then we're good to hang at least one
SD-20 (on a TCM IO-550)
If it's less than 100 inch pounds, then you could conceivably hang two
SD-20's -
(although it would take tiny fingers & a small miracle to get them both
bolted on & torqued properly!
########################################
If anybody is considering hanging two of the SD-20's, or has a radically
different engine,
you might want to look up your TCDS to find the latest "approved"
limitations.
You might find out you have a higher or lower gear ratio, torque limit, or
max overhang moment.
Just some thoughts for those who are cautious or curious.
(But I'm expecting answers from the electrically gifted!
Greg
|
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aerobubba(at)earthlink.ne
Guest
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| Posted: Thu Nov 16, 2006 5:43 am Post subject: Vacuum Pad Limitations - Weight & Torque... |
|
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Hi Greg et al-
I have no idea what assumptions are built into the max loads the TCDS calls
out, so were it me, I'd verify that the 40 inch pound limit was
specifically at 1g. Otherwise, it sounds like the SD-20 might limit you to
2.2g's. Does anybody out there have an insight into this detail?
| Quote: | The TCDS also shows that the maximum "overhang moment" of each accessory
should not exceed 40 inch pounds. By checking the specs at
http://www.bandc.biz/SD20REVC.pdf
it appears that the SD-20 weighs about 5.72 lbs and the CG is 3.15"
from the flange, for an overhang moment of about 18 inch pounds.
So far, so good!
|
glen matejcek
aerobubba(at)earthlink.net
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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