| Author |
 Topic  |
|
daveb
New Member
United Kingdom
52 Posts |
 Posted - 16/10/2007 : 09:31:50
|
Hi every one finally got the turbine up and i have to say what a total disappointment it is, the best its done in a good wind is a poltry 8v to be honest its no better than my original motor.Well its up now but after all the time effort and money Ive put into it its really knocked my enthusiasm for a six. I might try some other blades on it but for what ive spent on this and other things ime begining to think i could have bought a comercial or a decent solar panel."well back to the drawing board"
Daveb
|
|
|
Del
Junior Member
United Kingdom
369 Posts |
Posted - 16/10/2007 : 11:14:48
|
Hi Daveb,
The Ametek 38 produces 37 volts at 1000rpm so 27 rpm = 1 volt. If all you've seen is 8 volts you've only had it spin up to 216 rpm which isn't that fast. You're going to need 350 rpm to get a charge from your unit.
Either the wind wasn't that good, your blades are too slow, or you're losing some volts through long thin cable (although I don't think you would lose that much through the last one).
What blade set up are you using and what's the wind like where you are?
Ben made a good suggestion on another thread to take your turbine to a really good windy location to test its output. You might want to consider trekking up a decent hill somewhere to see what you can get out of it.
Cheers
Del. |
 |
|
|
daveb
New Member
United Kingdom
52 Posts |
Posted - 16/10/2007 : 12:11:12
|
HI del i think its down to blades more than anything where i live is quit open in fact the wind is so strong sometimes i have to put my shoulder to the door on the side of my house to close it,and ime using fairly thick flex i could loose a bit of length of it but ive left it a bit long incase i have to reposition my batteries.And i dont think thats the problem i did,nt have any 6inch pipe for the blades and had to use 4inch that was given to me, couldnt find any 6inch in B+Q. So i,ll have to get some ime toying with the idea of a 3 blades from bens PDF download or a 5 blade configuration as i used to use one on my other motor made from ply and they realy flew.
thanks
Daveb |
|
|
|
Del
Junior Member
United Kingdom
369 Posts |
Posted - 16/10/2007 : 15:13:44
|
Ah well, I might be able to offer some help. My first set of blades were from 4" gutter downpipe and I used a three bladed design to Bens first blade design (straight not curvy) and those blades were surprisingly quick.
So if you have quick blades, a windy location, and good cable I'd check the output of your motor using a cordless drill on a slow speed. If you have a drill that has multi speed settings you can check what the rpm is in the owners handboook (on each setting) and then monitor the voltage output using a multimeter.
Give it a go and let us know what results you get.
The only other thing I can think od is that your blades and or hub set-up is seriously out of balance and limiting your blade speed.
Cheers
Del. |
|
|
|
keithw2112
Junior Member
United Kingdom
103 Posts |
 Posted - 16/10/2007 : 15:18:26
|
hi dave i too run a ametek 38 set mine up about may but havent really seen much wind since.i guess we need a wind of at least 12 to 15 miles per hour to get the bugger up to 12-13v i keep an eye on wind speeds for my area from the bbc met office and they have been very low latley. saying that last night wasnt a bad night.but HEY dont dispare winters yet to come and them battries will start charging.
by the way i run three 24 inch pvc blades but my next set i will go 36 inch for that extra bit of oumph |
|
|
|
fungus
Moderator
301 Posts |
Posted - 16/10/2007 : 21:31:52
|
| Odd-mine is working pretty well below house level in a nice breeze right now- 12mph winds and it'll put out up to a half amp- but I guess I do have properly carved wooden blades and turbulance can affect reading seriously between buildings. I have seen up to 4A from it so far but I bet it'll do higher with the winter winds. |
|
|
|
Victor
Junior Member
United Kingdom
425 Posts |
Posted - 17/10/2007 : 05:54:08
|
Dave try and post a video if you have a camera on youtube...point it at the turbine ans we might be able to see the problem.....
I have a small Dynohub Turbine running and live about 30-40 miles away from fungus so we usually get the same winds..... At 12 miles an hour my turbine is flying and it has a coggin effect.......
We all must look into why your turbine is not flying??? Hopefully wee can get this sorted out before the winter winds!!! and get you some free energy ;-) |
|
|
|
Del
Junior Member
United Kingdom
369 Posts |
Posted - 17/10/2007 : 12:11:59
|
Hi Daveb,
Yes that's a good idea by Victor if you can do a short video, but I'd also bench test your motor to see that it's putting out what it should. If it's easier you can set-up a bicyle computer to monitor the rpm of your blades and do some rpm / volt comparisons to check its output.
Cheers
Del. |
|
|
|
Del
Junior Member
United Kingdom
369 Posts |
Posted - 17/10/2007 : 12:34:49
|
Hi Keithw2112,
If your blades aren't spinning quick enough then moving to 36" blades from your 24" ones will slow the rpm down.
The extra length will give more "oomph", "torque" and "grab", i.e there will be more blade surface area to catch the wind so the turbine will spin more of the time and in lower winds, but will not get you in the charging zone more often and will reduce the rpm of your blades so when you do get a good wind you won't be getting the best out of your turbine.
If your turbine isn't spinning at 350+ then there's no point in it spinning at all.
It's all to do with the speed of your blade tips. As the end of your blades travel the most distance they have to move the fastest and their resistance will be a BIG (and ultimately limiting) factor in how quick your blades turn in a good wind (a wind sufficient for charging).
Some calculations to support this to show the difference in tip speed between two foot blades and three foot blades.
Two foot blades mean you will have a circumference of 12.568 feet (pie R squared or pie D)
Multiply this figure by 350 (rpm) as this is the cut-in speed of the Ametek 38 and it gives you 4398.8 feet per minute. Multiply this again by 60 to get feet per hour and you get 263,928. Divide this by 5280 (feet in a mile) and you get 49.98mph. This is the speed of your blade tips at 350 rpm when you get 13v and allow the current to flow into your batteries.
If you do all these claculations again but with three foot blades (so pie x 9 instead of pie x 4) you will get a tip speed of 112.47 mph at the same 350rpm.
The wind resistance at 112mph is massively more than at 50mph and I can't see 3 foot blades hitting 350 rpm very often and it's unlikely they would go much faster.
What you want is shorter blades. They might not spin as often, but for a good enough wind to give you 13v they will spin faster and therefore give you more charge into your batteries.
Personally I use 18" blades on my Ametek 30, but I have five of them. There is a theory that because I have five, each blade is too close to the one in front and disturbs its airflow. I'm not convinced but am still playing with various designs. So far my short five blades is the fastest. I have one more PVC blade set-up evolution to try and after that it's wood for me I think.
Cheers
Del. |
|
|
|
daveb
New Member
United Kingdom
52 Posts |
Posted - 17/10/2007 : 12:50:42
|
thanks everybody theres a decent wind blowing at the moment and the blades are hardly moveing,so i think its the blades i made them using bens print off template but it was only four inch pipe and i think the angle is wrong.So i have a choise of using the template on 6inch pipe or going for the smaller earlier blades also there turning anti-clockwise i know its not supposed to matter but my old blades turned clockwise and seemed to go better.Because i did,nt have any sheet steel for the back plate i made it from ply triangular shaped and on bens plans the mounting holes for the blades are 1/4inch off center any thoughts on this.Del i will try running the motor from my cordless first and i would love to put it on youtube but i only have a vidcam which takes a tape and i dont think i can use it on the computer and if i could i dont know how to do it.It may be a few days before i can get back to you otherthings to do at the moment. thanks to everyone catch you later
Daveb |
|
|
|
Del
Junior Member
United Kingdom
369 Posts |
Posted - 17/10/2007 : 13:13:45
|
Hi Daveb,
If you're off with your mounting holes it will really slow your blades down.
I'd advise using a bit of ply and mounting it on your Ametek and conecting it up to 12 or 24 volt source. As it spins hold a pencil so it draws a perfect circle so that when you cut it out the ply hub you have will have a absolute perfect centre. Stage two is to use the same method to draw two more circles on your hub and these will eventually become the two mounting holes for each blade. By drawing circles this way you will get them perfectly centred. Next stage is to use a protractor to draw 120 degree lines (I assume you're using three blades?) Draw these out from the centre of the hub to the outside edge and where they intersect your two circles you have your six mounting holes. You can check that the measurements between each of the 120 degree lines on the outside edge of the hub are all exactly the same.
If you do this you will have a perfectly centred hub.
You also need to check your blades are all exactly the same weight (you can use kitchen digital scales) and have perfectly drilled holes that are identical to each other.
Don't worry about turning anticlockwise or clockwise - wind doesn't differentiate but some motors prefer to turn one way rather than the other and it's also a small consideration that if yiou use a nut on an abbour then spinning one way will help it self tighten and spinning the other will help it undo.
Where are you based Daveb?
All the best
Cheers
Del. |
|
|
|
keithw2112
Junior Member
United Kingdom
103 Posts |
Posted - 17/10/2007 : 14:54:56
|
hi del
thanks for that bit of info on blade size i understand where your coming from. i had just asumed that bigger blades caught more wind thus more rpm so i think next set will try 18s cheers mate |
|
|
|
Del
Junior Member
United Kingdom
369 Posts |
Posted - 17/10/2007 : 16:27:57
|
Hi Keithw2112,
They will catch more wind as you say so they'll start spinning in a lower wind, but any spinning below 350rpm on an Ametek 38 is not going to get your batteries charged.
I wish i could measure wind speed cos then I could do some graphs to see above what windspeeds shorter and thinner is better and match it to my normal wind availability and the cut-in of my turbine.
I think it's still very much an experiment and see kind of thing. With motors that don't have any cogging we have the luxury of being able to run smaller blades as they don't take much to get going.
Keep us posted as to how it goes.
Cheers
Del. |
|
|
|
ghurd
Junior Member
USA
314 Posts |
Posted - 17/10/2007 : 22:01:44
|
"try some new blades". Definitely.
Shorter blades usually spin faster, if the design is for that diameter.
ie: Cutting a foot off of 3 foot blades isn't a good idea, but making 'new' 2 foot blades may be great.
Bigger blades catch more wind and start easier, but they will turn slower.
If a strong wind is not getting it to charging voltage, knock 25% off the diameter.
It's not scientific, but is is what I do.
I don't worry if a cogger is not turning at 6 MPH, as long as it starts making battery charging amps at 7 MPH. An 8 MPH gust can get it going and it will keep going below 6 MPH if all is OK. Usually.
G-
|
|
|
|
daveb
New Member
United Kingdom
52 Posts |
Posted - 18/10/2007 : 19:32:52
|
Hi everybody managed to get some alterations done today,because i used the PDF print off on 4inch pipe it looked as though the leading edge was turning in toward the center of the blade so Ive taken some of the curve off it and i had a full tail vain on it this Ive halved because when i watched it working it looked like every time it reached a certain RPM the vain seemed to turn the blades out of the wind and Ive lost about a meter of flex"don't think it will make a lot of difference"Del couldn't try running off my cordless 5/8 shaft 1/2inch chuck and i didn't have any means of connecting it but when i spun it by hand i got 17v on the meter so i don't think its the motor although i was surprised the outer casing wasn't magnetised have a set of 5 blades made from ply i was going to try as they used to go quite well but the center hole is to big but im thinking on those lines anyway i don't care how fast they spin as long as they charge batteries. No wind today and none forecast for a few days so its wait and see.Del im in Rotherham S Yorks.
Daveb |
|
|
|
fungus
Moderator
301 Posts |
Posted - 18/10/2007 : 22:11:54
|
| daveb-on the 38v there is a allen/hex key slot I think in the front? shaft, thats how I tested mine getting 1.5A into a battery at about 500rpm, get a key that fits it and chuck it into the drill.. theres also the small ~3mm shaft out the back of it that you can chuck into a drill. |
Edited by - fungus on 18/10/2007 22:12:58 |
|
|
|
Topic |
|
AMETEK38v
