T-Pain Is On A Boat: Re: [Electric Boats] Gonna Try Direct Drive.

Good synopsis KON. That's whats nice about being handy, we can play & if it doesn't work, oh well.
In selecting belts thru the gates program Chris turned me on to one thing that really stands out to me is how many footpounds of torque is required to properly seat the belt on the drives. That has to have an effect on overall efficiency when loking at how easy stuff turns. Now I'm looking into helical gear drives. Might just hi jack what James at Eectroprop has been doing, thanks James. Personally I think it is a good idea but it comes with a cost & any tweaking from then on point to propeller experimentation. John R brings up a good point about stuffing boxes. Typical box is another place of substanial resistance & no matter how you cut, you have wet bilge.

Bob

--------------------------------------------
On Wed, 5/17/17, king_of_neworleans <no_reply@yahoogroups.com> wrote:

Subject: Re: [Electric Boats] Gonna Try Direct Drive.
To: electricboats@yahoogroups.com
Date: Wednesday, May 17, 2017, 12:10 AM

I think what I took away with me from both this
thread and this experiment, is that the theoretical ideal
reduction ratio is not always necessarily the best in
reality. For one thing, even the best reduction gear robs a
certain amount of power. It may or may not be significant in
an installation, and it can be optimized to some degree but
never made to go away entirely. A less than optimal (by
calculation) setup can sometimes be more efficient than one
that is perfect from an engineering standpoint. Modeling
formulae and software don't lie, but OTOH they do not
always reflect reality. So, experimentation has its place
alongside sensible predictions based on physics.

The final analysis was that
the motor was unharmed, and the noise was a coupling
setscrew grating on a keyed shaft which came loose due to
vibration. The key fell out, the shaft backed out, much
noise was made, I stayed drunk for two days and then waited
a day for the rain to stop. I put the system back together
and saw a best ratio of .7w/rpm, even though the shaft was
severely misaligned. There was not enough adjustment
possible without major work and I had other pressing
matters, so I put the 2:1 gearbox back in the drive train
and saw about .8w/rpm. About like before, but better than
with the 3:1 gears.

Before
reinstalling the 2:1 gearbox, I compared the resistance to
turning by hand of the two units, both at the input and
output ends. The 3:1 offered more resistance to turning than
the 2:1, even from the output end. I think the 2:1 gearbox
was simply broken in from use, whereas the 3:1 was new.
Possibly with a bit of wear, the 3:1 gearbox might have been
as efficient or more efficient than the 2:1, as suggested by
reasonable engineering predictions. BUT the fact remains
that in this case it delivered the worst efficiency while
the logical worst configuration was actually the best.
Without a standardized way of quantifying and applying the
mechanical losses of the gearbox or a belt drive or chain
and sprocket or whatever, a piece of the puzzle is missing.
We can't just assume equal efficiency inherent with a
reduction system, because it simply doesn't work that
way in the real world. Components are not always ideal, nor
are construction and engineering methods.

I have other things I must to
do to the boat before I return to work. When I get home from
my next job I plan to completely reengineer the motor
mounting system and ensure sufficient range of motion to
adapt to any forseeable configuration. The thrust bearing
will stand alone on a thrust plate. The shaft between thrust
bearing and motor will be broken and coupled with a splined
shaft arrangement so that a small amount of axial shaft
movement will have no effect on the motor, and motor
mounting will not be as critical. I will ensure that I can
couple the motor direct, or use the reduction gearbox, or a
belt drive, without disturbing the alignment of the prop
shaft, which will be adjusted for minimum resistance to
turning, and locked into its adjustment. Just the weight of
the shaft within the shaft log is enough to deflect the hose
mounted stuffing box and allow the shaft to drag on the
fiberglass shaft log. When the stuffing box is held exactly
right, the shaft turns smooth as silk, and will freewheel
for a couple of turns after a quick spin with the fingers. I
imagine that makes a few watts difference right there. I
want to couple a small brushed motor with a resistor network
speed control and an ammeter in series with the motor, and
find the sweet spot for the thrust bearing position. I think
thrust bearing placement and adjustment will prove to be a
dealmaker or dealbreaker, and help me to achieve optimum
efficiency from whichever drive configuration I end up
with.

I may run the motor
with the 3:1 gearing for a couple hundred hours and see if
the resistance to turning diminishes. I suspect that it
might. It is in no way difficult to turn, but even a small
resistance can have a significant effect.

One other thing I might try,
since I have two identical 5kw motors in addition to the big
motor, is to rewind one of the small motors with fewer turns
of bigger wire, for a lower RPM/Volt constant. I may end up
destroying a perfectly good motor. It may not even work.
That's okay, because I will know one more thing that
doesn't work, if it doesn't work.

I heard very sound and logical
argument to go with a lower voltage. Out of economic
necessity I am sticking with these 220ah golf cart
batteries, and I do not wish to wire batteries in parallel.
If I were serious about switching to 24v or 12v or whatever,
I would probably go with some very large single cells, at
least 1000ah. As it is, I think 48v is either optimal, or at
least a necessary compromise. But winding a motor
specifically to deliver lower RPM/volt, while certainly
reducing peak power output, might improve direct drive
efficiency at lower speeds. I have to look into that before
I start tearing up the spare motor.

I am also considering building a motor. Twice
as many poles ought to deliver half the rotational speed for
the same electrical rpm. A larger diameter motor ought to
deliver greater torque at low speeds. Or, maybe not. One
thing I have discovered is that even very knowledgeable and
intelligent experts, and the conventional wisdom, OUGHT to
be questioned and verified with real world experiments even
if they "can't possibly" work. The real world
likes to play little tricks on us.

#yiv1741949299 #yiv1741949299 --
#yiv1741949299ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}

#yiv1741949299 #yiv1741949299ygrp-mkp hr {
border:1px solid #d8d8d8;}

#yiv1741949299 #yiv1741949299ygrp-mkp #yiv1741949299hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}

#yiv1741949299 #yiv1741949299ygrp-mkp #yiv1741949299ads {
margin-bottom:10px;}

#yiv1741949299 #yiv1741949299ygrp-mkp .yiv1741949299ad {
padding:0 0;}

#yiv1741949299 #yiv1741949299ygrp-mkp .yiv1741949299ad p {
margin:0;}

#yiv1741949299 #yiv1741949299ygrp-mkp .yiv1741949299ad a {
color:#0000ff;text-decoration:none;}
#yiv1741949299 #yiv1741949299ygrp-sponsor
#yiv1741949299ygrp-lc {
font-family:Arial;}

#yiv1741949299 #yiv1741949299ygrp-sponsor
#yiv1741949299ygrp-lc #yiv1741949299hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}

#yiv1741949299 #yiv1741949299ygrp-sponsor
#yiv1741949299ygrp-lc .yiv1741949299ad {
margin-bottom:10px;padding:0 0;}

#yiv1741949299 #yiv1741949299actions {
font-family:Verdana;font-size:11px;padding:10px 0;}

#yiv1741949299 #yiv1741949299activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}

#yiv1741949299 #yiv1741949299activity span {
font-weight:700;}

#yiv1741949299 #yiv1741949299activity span:first-child {
text-transform:uppercase;}

#yiv1741949299 #yiv1741949299activity span a {
color:#5085b6;text-decoration:none;}

#yiv1741949299 #yiv1741949299activity span span {
color:#ff7900;}

#yiv1741949299 #yiv1741949299activity span
.yiv1741949299underline {
text-decoration:underline;}

#yiv1741949299 .yiv1741949299attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}

#yiv1741949299 .yiv1741949299attach div a {
text-decoration:none;}

#yiv1741949299 .yiv1741949299attach img {
border:none;padding-right:5px;}

#yiv1741949299 .yiv1741949299attach label {
display:block;margin-bottom:5px;}

#yiv1741949299 .yiv1741949299attach label a {
text-decoration:none;}

#yiv1741949299 blockquote {
margin:0 0 0 4px;}

#yiv1741949299 .yiv1741949299bold {
font-family:Arial;font-size:13px;font-weight:700;}

#yiv1741949299 .yiv1741949299bold a {
text-decoration:none;}

#yiv1741949299 dd.yiv1741949299last p a {
font-family:Verdana;font-weight:700;}

#yiv1741949299 dd.yiv1741949299last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}

#yiv1741949299 dd.yiv1741949299last p
span.yiv1741949299yshortcuts {
margin-right:0;}

#yiv1741949299 div.yiv1741949299attach-table div div a {
text-decoration:none;}

#yiv1741949299 div.yiv1741949299attach-table {
width:400px;}

#yiv1741949299 div.yiv1741949299file-title a, #yiv1741949299
div.yiv1741949299file-title a:active, #yiv1741949299
div.yiv1741949299file-title a:hover, #yiv1741949299
div.yiv1741949299file-title a:visited {
text-decoration:none;}

#yiv1741949299 div.yiv1741949299photo-title a,
#yiv1741949299 div.yiv1741949299photo-title a:active,
#yiv1741949299 div.yiv1741949299photo-title a:hover,
#yiv1741949299 div.yiv1741949299photo-title a:visited {
text-decoration:none;}

#yiv1741949299 div#yiv1741949299ygrp-mlmsg
#yiv1741949299ygrp-msg p a span.yiv1741949299yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}

#yiv1741949299 .yiv1741949299green {
color:#628c2a;}

#yiv1741949299 .yiv1741949299MsoNormal {
margin:0 0 0 0;}

#yiv1741949299 o {
font-size:0;}

#yiv1741949299 #yiv1741949299photos div {
float:left;width:72px;}

#yiv1741949299 #yiv1741949299photos div div {
border:1px solid
#666666;height:62px;overflow:hidden;width:62px;}

#yiv1741949299 #yiv1741949299photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}

#yiv1741949299 #yiv1741949299reco-category {
font-size:77%;}

#yiv1741949299 #yiv1741949299reco-desc {
font-size:77%;}

#yiv1741949299 .yiv1741949299replbq {
margin:4px;}

#yiv1741949299 #yiv1741949299ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}

#yiv1741949299 #yiv1741949299ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}

#yiv1741949299 #yiv1741949299ygrp-mlmsg table {
font-size:inherit;font:100%;}

#yiv1741949299 #yiv1741949299ygrp-mlmsg select,
#yiv1741949299 input, #yiv1741949299 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}

#yiv1741949299 #yiv1741949299ygrp-mlmsg pre, #yiv1741949299
code {
font:115% monospace;}

#yiv1741949299 #yiv1741949299ygrp-mlmsg * {
line-height:1.22em;}

#yiv1741949299 #yiv1741949299ygrp-mlmsg #yiv1741949299logo {
padding-bottom:10px;}

#yiv1741949299 #yiv1741949299ygrp-msg p a {
font-family:Verdana;}

#yiv1741949299 #yiv1741949299ygrp-msg
p#yiv1741949299attach-count span {
color:#1E66AE;font-weight:700;}

#yiv1741949299 #yiv1741949299ygrp-reco
#yiv1741949299reco-head {
color:#ff7900;font-weight:700;}

#yiv1741949299 #yiv1741949299ygrp-reco {
margin-bottom:20px;padding:0px;}

#yiv1741949299 #yiv1741949299ygrp-sponsor #yiv1741949299ov
li a {
font-size:130%;text-decoration:none;}

#yiv1741949299 #yiv1741949299ygrp-sponsor #yiv1741949299ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}

#yiv1741949299 #yiv1741949299ygrp-sponsor #yiv1741949299ov
ul {
margin:0;padding:0 0 0 8px;}

#yiv1741949299 #yiv1741949299ygrp-text {
font-family:Georgia;}

#yiv1741949299 #yiv1741949299ygrp-text p {
margin:0 0 1em 0;}

#yiv1741949299 #yiv1741949299ygrp-text tt {
font-size:120%;}

#yiv1741949299 #yiv1741949299ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv1741949299

__._,_.___

Posted by: bob jennings <sabre281@yahoo.com>

Reply via web post

•

Reply to sender

•

Reply to group

•

Start a New Topic

•

Messages in this topic (32)

Check out the automatic photo album with 2 photo(s) from this topic.

Have you tried the highest rated email app?

With 4.5 stars in iTunes, the Yahoo Mail app is the highest rated email app on the market. What are you waiting for? Now you can access all your inboxes (Gmail, Outlook, AOL and more) in one place. Never delete an email again with 1000GB of free cloud storage.

Visit Your Group