24/48 conversion completed - 16' flying again at 85'

[Dave B]

What was going to be just my annual maintenance turned into a 24 to 48 volt complete conversion. As long as I had it all apart for the inspection and maintenance I decided to cast a new 48v stator and re-wire my L-16's. Replaced my Trace 3624 MSW with a new Magnum 4448 pure sign and rewired my control panel. Plenty of wind predicted the next few days will be good testing weather. A couple of photos here (I hope) showing it back up and running on my 85' Rohn 55 G modified tilt tower. Updates to follow.   Dave B.

[madlabs]

Just had to say wow! That mill looks small on top of that tower!

Jonathan

[kitestrings]

Hi Dave,

Nice work, and no simple task.  We went from a 12V to a 48V system a few years ago.  I think in some ways it is trickier than starting from scratch - so many variables.  I found in our csae with re-wirng the batteries that if I rotated every other battery (6V- L16's) it made the connecting leads more direct and shorter.  We also had to maintain a 12V 'tap, wth an equalizer, for the balance of remaining 12V loads:



I've a few questions for you:

I was trying to follow the guying scheme.  We've done alot of 25 & 45G Rohn's, but it looks like you have some guys that are split before attachment, and others that are going to more than one leg?  Was this to reduce a vibratuion or natural frequency?

Aside from the voltage conversion, you went originally from a water heating unit to battery charging, correct?  I was curious if this required any other changes to the offset/furling for example?

Thanks for sharing.

~kitestrings

[Dave B]

Hi Dave,

Nice work, and no simple task.  We went from a 12V to a 48V system a few years ago.  I think in some ways it is trickier than starting from scratch - so many variables.  I found in our csae with re-wirng the batteries that if I rotated every other battery (6V- L16's) it made the connecting leads more direct and shorter.  We also had to maintain a 12V 'tap, wth an equalizer, for the balance of remaining 12V loads:

(Attachment Link)

I've a few questions for you:

I was trying to follow the guying scheme.  We've done alot of 25 & 45G Rohn's, but it looks like you have some guys that are split before attachment, and others that are going to more than one leg?  Was this to reduce a vibratuion or natural frequency?

Aside from the voltage conversion, you went originally from a water heating unit to battery charging, correct?  I was curious if this required any other changes to the offset/furling for example?

Thanks for sharing.

~kitestrings

  Thanks for the comments and no simple task for sure. I have 8  L-16s and the connections are oriented like yours only 2 rows of 4. I built my enclosure for that space so now going from 2 rows of 4 series / parralleled for 24v  I only had to move one row of the inter connects and change the end for 8 in series 48v.

  If you have done several guyed lattice type towers then you know the challenges involved. Especially interesting is modifying a triangular tower for tilt. To cma I'll just say there are many ways to do things.

  Yes, I have made several turbine changes depending on heating or charging and like most have experienced it has been a trial and error especially with the furling. Normally what you think should happen doesn't and vice versa. My biggest improvement was understanding that blade direction of rotation, offset side and precession made a huge difference in my furling performance. Unfortunately each machine is different but get this figured out for your own machine and no garlic is necessary to keep the mysterious blade seeking curse away.

  Major wind today gusting over 60 mph at times. The logging for today will be interesting, updates soon.  Dave B.

[SparWeb]

Dave,
I did some calc's on Rohn towers a few years ago, and I seem to recall (correct me if you disagree) that the leg compression forces became tremendous when guyed so much.

[Dave B]

I agree the compression forces must be high but if the tension is proper for each level then these towers are designed for these loads as well as the additional weight of stuff normally hung off of them. This is a 55 G and Rohn sells this tower package up to 300'. This tower was 140' and had all kinds of big dishes and mounts etc. hanging off of it. What really amazed me was that each guy level had  only 3/16 guy wire except for the top which was 1/4". Each 10' section weighs about 100 lbs and like mine every 20' was guyed. I think a mistake some could make is improper guy wire tension and I bet more likely on the too tight side. Guy wires only keep the tower from falling over, the legs hold the weight to keep it standing.  Dave B. 

Dave,
I did some calc's on Rohn towers a few years ago, and I seem to recall (correct me if you disagree) that the leg compression forces became tremendous when guyed so much.

[kitestrings]

Ahh, it is four guy points so you can tilt it.  Now I see what I was missing.

I prefer venting the individual cells to building an enclosure.  I think it helps to keep the corosion away from connections, and sugaring tubing is cheap where I live.



So remind me - view from upwind - you're off-set is to the right, blades rotating ccw, and tail furls to the right?

~kitestrings

[Dave B]

Right on, I didn't want to compromise the original guy brackets in any way so I came up with what you see. A big bonus is stability from the tower ever twisting also. What kind of arrangement do you have for the vent connection at the batteries ? Do you force vent these also ? I'd like to have my batteries inside but have little room so I built an insulated enclosure and of course have the temp sensor wired for the inverter / charger. Saving my pennies for another 8  L-16's.  Dave B.

Ahh, it is four guy points so you can tilt it.  Now I see what I was missing.

I prefer venting the individual cells to building an enclosure.  I think it helps to keep the corosion away from connections, and sugaring tubing is cheap where I live.

(Attachment Link)

So remind me - view from upwind - you're off-set is to the right, blades rotating ccw, and tail furls to the right?

~kitestrings

[kitestrings]

The tubing is standard 5/16" maple sap tubing.  I drill the origianl vent-caps and plugged the small holes with silicone.  They go into 6-way manifolds (perfect for 6V batteries), these transition to 1/2" NPT & PVC.  From there I increased to I think it is 1/1/4" PVC.  I vent out through the box-sill and just have a srceen to prevent any vermin.  No fan or controls.

It is not very scientific, but seems to work fine.

Are you thinkling that you can add a new string to the existing bank?  Everyone seems to warn against it, but if they are relatively close in age/condition I'd think it would be okay.

~kitestrings

[Dave B]

Kitestrings,

 Very cool idea with the venting, makes me want to have my bank inside. Maybe by the time I'd have enough for another 8 L-16's I'd sell these and start with 16 new. These are only 1 1/2 years old and are the newer RE version, I've heard of not mixing older and new and the theory sounds good but hey, it's any one's decision to try what they want.

 Forgot to confirm with you that yes, looking from upwind at the front of my machine I am offset to the right with ccw rotation and the tail furls up to the right. I know for a fact (been there done that) that for this machine if I were to change any of this without keeping the relationship the same (offset left, cw rotation furl to the left would work well too I'm sure) the mysterious "wind seeking curse" would be upon me.
 
Dave B.