Author Topic: ST Hum  (Read 9528 times)

NoSpark

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ST Hum
« on: November 27, 2008, 12:08:58 AM »
Been putting some hours on the 'roid using various loads, nothing useful yet. I love the sound of the engine. Sometimes I just stand and watch the flywheels go round and the valves tick away  :). But the hum from the ST5 when loaded is almost maddening  >:(. Anyone had to isolate their ST from a metal frame because of humming, or is this a problem I should be looking for? Maybe it can't be stopped, I thought I read here about someone with the same problem but I couldn't find the post.
Anand Powerline 6/1 ST5

rcavictim

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Re: ST Hum
« Reply #1 on: November 27, 2008, 12:33:15 AM »
Sounds like a bad case of dynamo hum to me....Zappa.

Your head may not have been properly impregnated with motor varnish which when properly applied (under a vacuum process and heat) takes up the slack space in between the stator windings and laminations so they cannot vibrate or buzz when physically influenced by the reversing magnetic fields.  If your head has uncoated windings you could remove the end bells and armature and take the stator cylinder to a reputable motor rewind shop for a varnish or Glyptal treatment.  You likely won't be able to get the varnish to flow into the tight spots where it is needed merely through application to the exposed ends of the stator winding pack.  It needs to get deep into the grooves of the stator and those are closed off with bamboo strips.  Trying to coat by yourself will only succeed in closing off the path needed to get the varnish deep into where it is needed.

If it is an ancient ST head it may just be senile and is humming because it has forgotten the words.   :D
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MacGyver

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Re: ST Hum
« Reply #2 on: November 27, 2008, 01:01:51 AM »
Mine hums (growls) rather loudly if one winding is heavily loaded while the other is not. If both outputs are reasonable equally loaded, then it's pretty quiet even at full load.

Since I'm using a transformer to balance the load on my ST, mine is always quiet.  :)
Steve

JKson (PS) 6/1 'roid & ST 7.5

mobile_bob

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Re: ST Hum
« Reply #3 on: November 27, 2008, 01:42:56 AM »
my st 7.5 makes a godaweful whirring sound, mid pitch, not a low growl but not a scream either
it doesn't do it all the time, but when it does it can take several minutes to calm down.

i figure it is some loose laminations, and plan on getting into it when i tear down for final welding of the
frame.

without ear protection when it is bad it is deafening!

bob g
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rcavictim

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Re: ST Hum
« Reply #4 on: November 27, 2008, 01:50:03 AM »
I do not yet have a working ST head in service.  I have a stripped down ST-12 awaiting a round tuit in the way of a complete stator rewind.  That will be a completely new DIY experience for me if it happens.  I had no idea these were apparently so noisy.

The British made 4-pole head that I have on my Petter with 24 volt DC start function (the large one seen on the original Lister SOM's) has no audible whine issues at all, nor does the 480 volt, 3-phase British made 15 kW, 4-pole head I have on my VW plant.

After reading the comments that followed my earlier post about lamination and winding looseness there is another mechanism that can be responsible for the audible whine, even if the core and windings are potted up solid.  It is the field modulated expansion and contraction of the actual iron core.  This is called magnetostriction.  Not much I know except isolation and acoustical insulation techniques that will take care of that.
« Last Edit: November 27, 2008, 01:53:22 AM by rcavictim »
-DIY 1.5L NA VW diesel genset - 9 kW 3-phase. Co-gen, dual  fuel
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mobile_bob

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Re: ST Hum
« Reply #5 on: November 27, 2008, 02:01:25 AM »
to be fair, i don't think they are all noisey, quite the contrary i think it is an odd one that is.

mine is only noisey every once in a while, and only for a bit, sometimes maybe 10 seconds, sometimes several  minutes
usually throwing a load on it will kill the noise.

i figure on takeing it down for 1st world brgs anyway, so i don't see it as an issue really.

it is a st7.5 and will pull 7500watts continous without even getting warm to the touch, well maybe
just over 105 degree's is the highest i have ever measured at that load.

so i personally think it is one hell of a head for the money, i ain't complaining :)

the whole unit runs so silky smooth that i swear i could set it on 3 coke bottles and run it at full load
and it would sit there happily humping away.  very little vibration to the concrete, likely less than 5% of
a concrete mounting system would provide.

i do know that running the unit sitting on the floor can be felt all through the house, vibrate the dishes
and is pretty obnoxious.

now my wife is unaware it is even running in the attached garage while i am flogging the crap out of it doing
dyno runs from hell.

i couldn't be happier, but then again it ain't a lister/oid i am working with either :)

oh ya lest i forget

LONG LIVE THE MIGHTY CHANGFA

:)

bob g
otherpower.com, microcogen.info, practicalmachinist.com
(useful forums), utterpower.com for all sorts of diy info

NoSpark

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Re: ST Hum
« Reply #6 on: November 27, 2008, 02:08:49 AM »
Loose laminations  :o  Magnetostriction :o   I'm sure the frame must be amplifying the hum, I may try to isolate the ST from the frame with some rubber or I might just deal with it if it doesn't do any harm. Today it didn't seem to be as loud as it was a few days ago. I've only been loading one leg, I'll have to hook up a socket to the other leg and see what happens. Where can I find the right transformer to balance this thing? Time to start wiring a panel.



"If it is an ancient ST head it may just be senile and is humming because it has forgotten the words" How did I know someone was going to say something like that  :).
Anand Powerline 6/1 ST5

Tom

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Re: ST Hum
« Reply #7 on: November 27, 2008, 02:09:31 AM »
My ST5 didn't hum while it was wired for 120v output, when I rewired it for 120\240v it hums. Like Steve's when loaded evenly it is quiet.
Tom
2004 Ashwamegh 6/1 #217 - ST5 just over 3k hours.

t19

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Re: ST Hum
« Reply #8 on: November 27, 2008, 02:33:54 AM »
maybe it just does not know the words at that range :D
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NoSpark

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Re: ST Hum
« Reply #9 on: November 27, 2008, 02:10:23 PM »
My ST5 didn't hum while it was wired for 120v output, when I rewired it for 120\240v it hums.



Interesting! I'll try changing it to 120v for the hell of it too. thanks
Anand Powerline 6/1 ST5

NoSpark

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Re: ST Hum
« Reply #10 on: November 27, 2008, 07:30:05 PM »
Switched the ST over to 120v today. NOW it hums, before it grrrowled! With 1700 watts I can barely detect the little hum it makes. Coool! But since I need 240v for my service panel I'll have to look into a transformer to balance the loads. BTW when the gen was hooked up 240v I had 119v per winding, with it hooked up 120v I have 130v @60hz.
Anand Powerline 6/1 ST5

ronmar

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Re: ST Hum
« Reply #11 on: November 27, 2008, 08:43:28 PM »
My ST5 dosn't make any real noise.  Your noise was probably mainly from only loading one leg in the 240 mode.  If you hook some 240 load to it, I would guess it will be as quiet as it is in 120v mode. In 240 mode, the coils will be loaded evenly, like they are in 120V mode.  Depending on how your frame is constructed, it could also be amplifying/resonating this sound

Burden Surplus center has some electric baseboard heater elements.  At 250 watts/FT at 240VAC, these make excellent load banks for testing and warmup.  I have a 1500W and a 2000W hanging on my generator room wall. 

http://surpluscenter.com/sort.asp?UID=2008112714313018&catname=hydraulic&byKeyword=yes&search=baseboard
 
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cujet

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Re: ST Hum
« Reply #12 on: November 27, 2008, 09:26:35 PM »
I'll put money on the fact that you have bad bearings, a common ST problem.

Purchase some quality bearings and it will run quiet, for sure.
People who count on their fingers should maintain a discreet silence

M61hops

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Re: ST Hum
« Reply #13 on: November 27, 2008, 11:20:39 PM »
I thought I'd throw in my comment here about ST head hum.  My 7.5 ST head "growls" quite loudly when the load is unbalanced by more than about 700 watts or so but is quiet when the load is well balanced.  Seeing the comments from others about their 7.5 heads makes me wonder if that is something unique to the 7.5 ST heads or if all ST heads might do this?  The noise is not terribly loud but is noticeable and consistant.  It doesn't strike me as anything to worry about, it's not getting any worse, but it is there.  My ST 5 has always had noisy bearings but I never noticed it making more noise when the load was unbalanced.  After I replace the bearings and hook the ST 5 back up I'll check to see if it acts like the ST 7.5.  However it will be some time before I get around to changing out the bearings so I won't be able to report on the results for at least several months.   Anyway, happy Thanksgiving to all on this list!                      Leland
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listeroidsusa1

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Re: ST Hum
« Reply #14 on: November 28, 2008, 02:13:21 AM »
One simple item to check............ The stator core is a slip fit/light press fit in the main housing. There is only one setscrew holding it tight in the case. It is beside the lifting ring on top. Make sure it is tight. If it is loose it can allow the core to shift and make noise.

Mike