----- Original Message -----
Sent: Thursday, December 20, 2007 11:25
AM
Subject: [FlyRotary] Re:
Supercharging
Interesting find, David.
I must admit after seeing all of those squirrel
cage fan "electric superchargers" advertised for $59.99 on E bay
and else where back a few years ago (and perhaps even today) - I was
very skeptical of what I would see here. I also could not find any
technical specifications or compressor map on the website - and that does not
lessen my skeptical feeling.
However, from the forum "testimonials" in which
several folks have dynoed the results as well as collected other parameters, I
must admit it appears there is some validity to the claims or else they are
somehow fooling a lot of folks {:>).
It appears to take between 700 and 1100 watts of power
from what data I could find. So Power = Current*Voltage. The
current would then I = Power/Voltage = 1100/12 = 91 amps, or 700/12 = 58
amps. So the current draw may depend on the model but would appear to
range from 58 - 91 amps or around 1 - 1.4 HP. So a fully charged battery
would probably power it for 5-10 minutes - perhaps longer, you could get more
precise interval by looking up the Reserve Capacity of your battery.
I must admit that for the price it is tempting just to
get one and play with it - However, I have not seen anywhere mention of its
weight. From the electric motors I have seen, - a 1 - 1.4HP
electric motor can be huge and heavy. Now this is
surely a smaller/lighter weight motor than those heavy weighs. I
forget my DC motor types, but as best I recall there is one referred to as a
series winding that simply keeps spinning faster (and drawing lots of current)
until it meets its load limit (or flies apart). But again no
specifications that I could find.
So putting aside my skepticism (for the moment) I
would think for aircraft use you would probably want a second battery you
could dedicate to powering the superchargers electric motor for a several
minutes. Hummm, where did I put that second battery case, I took out of
my aircraft.
I would certainly want to know how long the motor could
stand the load and heat. It does not appear this is meant for sustained
boost, just for getting your Mustang from 0-60 quickly then off the
boost. But, having 30 more HP for take off and initial climbout for 3-5
minutes could be nice to have. Then the next question is how much effect
it has on the air flow to your engine when it is not under power.
Eliminating the need for hot exhaust gas and water coolant lines would be also
be a plus. Could not tell whether it required any tie in to the engines
lubrication system - one would presume so, but there was a turbocharger sold
for a while that had its own oil reservoir. And of course what does it
weigh?
Still for $100 it might be interesting to
experiment with. But, I'll wait a bit - no mention of problems on the
site, but also no mention of life cycles or hours of run time. Still a
bit skeptical, when I don't see any specifications on a website, but willing
to suspend it for a while {:>)
Ed
----- Original Message -----
Sent: Thursday, December 20, 2007 9:06
AM
Subject: [FlyRotary] Re:
Supercharging
Google place this ad for electric superchargers on the last
post. At least it is designed for an engine..
http://www.electricsupercharger.net/
Dave
Leonard
On Dec 20, 2007 6:02 AM, Thomas Jakits <
rotary.thjakits@gmail.com>
wrote:
Here
a another interesting bit on the screw type charger "wars":
http://www.svtsnake.com/forum/archive/index.php/t-1387.html
Obviously one must do his homework before deciding on one.
However the design seems superior to the roots anyway ....
TJ
On Dec 19, 2007 11:15 PM, Ed Anderson <
eanderson@carolina.rr.com> wrote:
----- Original Message -----
Sent: Wednesday, December 19, 2007 10:47
PM
Subject: [FlyRotary] Re:
Supercharging
> Ernest Christley wrote:
>> David
Leonard wrote:
>>>> 6000RPM is about the speed that
commercial leaf blowers use. The
>>>> blowers just
happen to be about the same size as an engine housing.
A
>>>> conservative blower will easily deliver 600 CFM at
150MPH.
>>>>
>>>
>>>
>>> Somehow we are going to
have to connect the blower to the drive
>>> chain.
That
>>> is either going to be a belt (with pullys we can
size however we want) or
>>> some sort of gear. Either
way, everyone will have a blower running
>>> the
rpm
>>> they need, no advantage (or disadvantage) to the
rotary running at
>>> 6000
rpm.
>>>
>>>
>>>
>>
>> What if you replace the flywheel with the fan
from the blower? No
>> gears. No belts. No
chains. No heavy mounting to support any of
>>
them. The advantage of the rotary running at 6000 RPM is that we
don't
>> have to pull the power off and transfer it over to a
different
>> structure. We can mount the blower as an
integral part of the drive chain.
>>>
>>>> We don't
>>>> usually want a
LOT of boost in an airplane, since that will impact
>>>>
reliability, but how much is a
LOT?
>>>>
>>>
>>>
>>> True, not "a lot" by
race standards, but if you just turbo normalize you
>>> WILL
be using a lot of boost (by OEM standards) when above 10000'. I
>>> could
>>> easily max out my stock turbo at
14000.
>> More power is always more better, but what deal with
the devil do you
>> have to make to get it? My project
can't handle the weight of a turbo
>> or a supercharger, and I
personally don't want to deal with the
>> complications of
either. So I back off, accept less power as the
>>
penalty for doing less work. Can I get 10Hp for a couple pounds on
the
>> nose and a few more feet of intake plumbing? The
answers we've come up
>> with so far say that it is a definite
'maybe', with a solid dose of 'it
>> depends'. Maybe I
won't be able to completely normalize, but I think I
>> should
be able to increase my service ceiling. An alternate air intake
>> will enable me to test to see just how much it
increases.
>>
>> --
>> Homepage:
http://www.flyrotary.com/>> Archive and UnSub:
>>
http://mail.lancaironline.net:81/lists/flyrotary/List.html
>>
>>
> A 'sanity check' (of the concept)
might be in order.
>
> How big is the 'fan' in the leaf
blower (diameter & thickness)?
>
> How big is the 'fan'
in a typical turbo for the rotary?
>
> Is it likely that
the 'fan' from the leaf blower can move as much air
> against the
same back pressure turning 6k rpm as the turbo turning 100k rpm?
>
> (A P-port will *reduce* weight as it adds HP. :-) )
>
> Charlie
>
Hi
Charlie,
Flew past your place on Monday heading back from
Louisiana, gave a radio call but got no response and didn't have time to
stop for a visit.
Regarding your suggestion/question. Part of
the problem is that the engine will always displace the same cubic
inches per revolution. Therefore, there are only two ways
to get more power per revolution - increase the density of the
air or provide more oxidizer through a chemical process such as Nitrous
oxide. You simply can not force the engine to produce more power
per rev without doing one of the two - or both.
A turbo compressor or supercharger has to compress
(increase the density of the air) without letting the higher pressure
air (as a result of increased density) flow backwards past the
pump impellers from the high pressure area to the low
pressure area. The roots type blower does this by acting as a
positive displacement pump it self whereas the centrifugal compressor
simply uses the superfast spinning blades to beat the air molecules from
the low pressure area (intake) to the high pressure area (manifold) and
with such close tolerances that the air molecules have difficulty
overcoming the momentum of the air and trying to flow back from the high
pressure area against the spinning blades.
So the reason the turbo and supercharger increase
power for a given rpm over an N/A engine is they increase the
density of the air not the velocity or volume - those are just side
effects. The flow rate will in fact appear to increase because the
non compressed flow will flow faster into the compressor's intake as the
increase in density after the compressor must come from additional
airflow into the compressor. However, the engine itself is still
flowing the same cubic feet/sec its displacement of course does not
change - its just that its combustion chamber is now packed with
more air due to the higher density.
I certainly hope the experiment proves
worthwhile - but, I must admit I can not see how it is going to
significantly increase power. Whether the power addition is worth
the effort will depend on how much effort it requires for the
gain.
Just my 0.02
Ed
--
David Leonard
Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net