[Burnit0017]

Greetings, I am trying to add a gear drive to the top of a permanent magnet alternator used with a vertical axis wind turbine. I first used gears and found they make to much noise to be used. I am now trying to replace the gears with belts. The belts need to be under tension. If anyone can direct me to any ideas how this can be accomplished please let me know. Comments welcomes

[packrat]

How about a belt tensioner? A pulley mounted on a spring loaded arm to push up against the smooth side of the belt. The pulley has to have a bearing/bushing in it to reduce friction.

[Burnit0017]

How about a belt tensioner? A pulley mounted on a spring loaded arm to push up against the smooth side of the belt. The pulley has to have a bearing/bushing in it to reduce friction.

Hi, I am going to try to making one shaft move so all the belts tighten at the same time this will require the least amount of parts and be easiest to fabricate. Thanks for the suggestion. I found a tooth rake that is used for agriculture that will function as a torsion spring to move the posts apart and provide a constant tension to the belts over time. It will a few days to fabricate all the parts. Thanks again and enjoy the day.

[Al_The_Man]

I have used Rosta products, I think they are owned by Lovejoy now.
http://www.mehanika.by/userfiles/fil...TA/1/rosta.pdf
Al.

[Geof]

Have you looked up the efficiency of belt drives compared to gears? You have a four step belt drive. If each step is 90% efficient, which is optimistic, your overall efficiency is about 65%. At 80% efficiency the overall is only 40%.

Gears might be noisy but they are much more efficient and the next best is chain. Also with gear or chain you don't need as many steps which is what kills the overall efficiency.

[Burnit0017]

I have used Rosta products, I think they are owned by Lovejoy now.
http://www.mehanika.by/userfiles/fil...TA/1/rosta.pdf
Al.

Greetings, thank you for the very useful link. If my plan fails the link may provide a alternative, it is nice to have options. Because wind is a free resource, efficiency will be addressed after the prototype is working. Direct drive would be the best but the rising cost of rare earth material has forced the need for a geared configuration. The increase in cost is really quite alarming.


China Consolidates Grip on Rare Earths - Yahoo! Finance

[Burnit0017]

Greetings, just some photos of torsion spring yoke assembly. I still have to cut slide holes in the mounting plates. Enjoy the day.

[Burnit0017]

Greetings, I still have to add spring shaft adjustment to tighten all the belts at the same time. I made the belt pulleys double the width to allow for easier belt to pulley alignment, this will also allow the belts to self track. Fabrication of the first one is going slow but so far the results appears to indicate that it will work. Enjoy the day.

[Burnit0017]

Greetings, project update:
Timing belts and pulleys are installed on a test rig. Because the pulleys are made using two pieces I was able to bevel each piece toward the center of the pulley. This forces the belts to track toward the center of the pulley so a lip is not required. I have to find the correct tool to bend the spring into the correct shape. This a first attempt but it appears to be working. The spring pulls on the top and bottom of the movable shaft and all belts have tension. Again this is a experiment and a learning experience, I do not know how long the belts will last. The next step is to mount it on the PMA and perform a road test. The current configuration is a 1 : 6 ratio.

[handlewanker]

Hi, I would have thought that the experiences of the "big Windmills" with gearboxes would have highlighted the fact that the design is faulty and not worth progressing with.

If'n you are not experimenting with direct drive you aren't going to achieve any worth while output.

BTW, 1 : 6 ratio is gearing down, which means your wind turbine is going to drive the alternator at 1/6 the speed....you must have some powerfull winds in your quarter if'n you need to slow the alternator speed, or an extremely well balanced vertical turbine assembly.
Ian.

[Burnit0017]

Hi, I have no training with mechanical design. This is a experiment and a learning experience. The blades spin one rotation and the alternator spins six times. The correct notation is 6:1, thank you. I have changed the design to a more manageable two belt configuration. 6.5 : 1. I saw they are using belts drives to replace chains on bicycles and my project needs a transmission because the blades I can fabricate have more torque than speed. Thanks for the info.

[handlewanker]

Hi, I realise you are experimenting and learning, but simply driving the alternator with no load or electricity generated means you are converting torque to speed, and in the process you absorb quite a bit of power from the 'mill through friction in the gearing, belting or through friction in the pulley grooves if'n you are using plain Vee belting on plain pulleys.

Given that on a windy day the 'mill turns and the alternator spins, as soon as you apply a load, eg connect it to a load as in a light bulb, motor or any electric appliance, the alternator will be acting like a brake to the 'mill and you get a reduced rpm output, this means you get less electrics, and less output...the efficiency is probably in the order of 5% if'n your lucky enough to keep it running.

You could side step the friction loading of the belt drive section by designing a direct drive generator that uses some of the output to create a magnetic field in the rotor, thereby enabling you to regulate the output even though the speed varies.

A direct drive generator of that type would have a much larger diam than the actual 'mill itself, and there is a trend to go in that direction now with the larger commercial types.

Using the rare earth permanent magnets in a big diam genny would be quite costly, and they tend to lose their magnetism after a while, but you can DIY an alternator with wound field rotor and stator using most generally available materials, like copper wire from junked transformers etc.

Best of luck for a fascinating hobby.
Ian.

[RomanLini]

Nice design! And a very cool project!

Toothed belts don;t need much or any "tightness" at all, in fact you need them to be fairly loose as plastic gears have quite a high thermal expansion (much more than metal) and will expand in the warm sun and with heat generated by use.

The toothed belts at low speeds have quite a high energy efficiency (especially if they are not tight).

HW- It's generally accepted that the new rare earth magnets have very good retentivity compared to the old ceramic and AlNc magnets.

[Burnit0017]

Hi, When I made the pulleys I rounded off the teeth to much. The weight of the mag rotors is about 20 pounds and there is a lot of force being applied to the teeth on the pulleys to start the mag rotors spinning. I am using a wider belt and machining new pulleys to better match the profile of the teeth on the belts to solve the problems. Thank you for all the suggestions.

[handlewanker]

Hi, in Engineering you don't get anything for nothing, and it's a very unforgiving process for sliding one surface upon another.

In your design, the action of increasing the belt width will create more "gription", note this is a new word and completely describes the action of an object as it attempts to make contact with an another object and move it without slipping.

Grip, as in the "stickiness" you get when one surface temporarily attaches itself to another, and friction, the force you get that impedes the progress of one surface sliding on another.

So, the all empirical Technical College of knowledge, from which I graduated many years ago, LOL.... gives you the fact that the more surface contact you have with a flexible medium the more "gription" you'll get and the more power absorbed in the transmitting of movement.

At the top of the ladder, comes the hardened and ground steel gears running in ball races, and you can get 95% transmission of power with only 5% losses from friction.....quoted in Machinerys handbook, the Engineers Bible.

As you go down the ladder you get to the bottom rung where you have the simple vee pulley with rubberised Vee belt drive.

The tighter you have to make the belt tension in the Vee pulley drive the more "gription" you will get, and the more losses you will encounter.

You can minimise the effect of gription by using the very smallest section of Vee belt you can get, as the forces you are dealing with are of a very low order.

In this area I would prefer to use a Poly Vee belt, a thin very flexible flat belt that has multiple Vee sections on its driving face, and drives on multi grooved flat pulleys.

Toothed belts are one step down from a geared arrangement, and are only really used where a ratio must be maintained at all times, but by the nature of the need to ensure that the teeth of the belt engages with the toothed pulley and do not ride over the pulley teeth you will have to tension them fairly tightly....this can be verified by checking the specs for a cars timing belt tension, where they use toothed belts in place of the multi roller chain drive.....toothed belts being used to offset the need to lubricate a chain drive set-up.

In my opinion, with a 6.5 : 1 ratio and using a belt drive, you will be hard pressed to get the windmill to start turning without requiring a stiff wind at all times.

This is similar to pedaling a bike and starting from stop with the gearing in the highest notch of your derraileur, which makes it virtually impossible to get up to speed in a short time.

You would attract less friction if'n you used the nylon gears driving together and with shafts running in simple ballraces.....but it depends on the means at your disposal and your ability to mesh gears and fit ballraces.

If'n this is just a short term experiment, then gears and ball races might not figure in the design, but it takes just as much effort to use an alternative method like vee belts and bronze bushes etc.

The point is, the project will fail through lack of design, and design affects every aspect of the drive train from beginning to end, and you can not escape the law of physics in design.

What you will learn in the end is that if'n you had used a better design in the concept stage you will get better results......and if'n you blame the failure of the project on it's concept, it is actually the design you should be blaming.....the 'mill will still go round and round, but for better or for worse.

I would consider the 6.5 : 1 gearing up as a non starter from day one, just my opinion.
Ian.

[Burnit0017]

Hi, photos of belt and pulleys with idlers. The configuration may not be mechanically correct but the belt does not slip and has low bearing load. The configuration allow the pulleys to be placed much closer than normal and the belt cogs mesh with the pulley teeth.

video showing concept
[ame=http://www.youtube.com/watch?v=iO6nZakBcQk&feature=related]Spot Longboard 29er with Belt Drive - YouTube[/ame]

[handlewanker]

Hi, why do you persist in going with a drive that is designed to act like gears when in your project the property of meshed gearing is not needed....IE, you don't need to have an absolute ratio output as in a timing device need, all you need is a step up ratio and if'n the belt slips 1% during it's rotation, it will not affect the output, which means you can go to those skinny belts which will cut down on friction dramatically, also they're much cheaper, both belts and pulleys.

BTW, my tumble dryer has a small flat belt to drive the drum, and although it's a reduction drive in the order of approx 1 : 15 ratio it will drive the drum with a full load of clothes without slipping dramatically.

The flat belt is about 2mm thick and approx 15mm wide, and goes around a small pulley of about 30mm on the motor and wraps round the drum which is about 450mm diam, giving you approx 1 : 15 reduction.

If'n someone has an old belt drive record player they don't need anymore, you can turn it into a wind generator with just a few add on's.

First you make the Savonius turbine blade part and attach it vertically to the turntable with glue(whatever).

The motor will need to be replaced with a small 3 or 6 volt electric plane type motor, and as they have rare earth magnet rotors with wound stators putting out 3 phases, you'll get some electricity if'n you drive it, and it can be rectified to DC.

The original motor will probably have a pulley diam of 8mm or so, and a turn table drive track underneath it of about 250mm diam with a flat belt of about 10mm wide and .5mm thick, which gives you approx 30 : 1 step up drive, so the new motor might be persuaded to accept the old motor pulley with a bit of fiddling, but I'd make a larger pulley for the motor to give a smaller step up drive at about 20 : 1.

I just checked the record player specs.....the motor is a shaded pole type and runs at mains frequency to give (at 50 Hertz) 1425 rpm, and the turntable rotates at 33 rpm, so the ratio is approx 1 : 43 (record playing), and if'n you make the new motor pulley twice the existing diam you'll get about 21 : 1 ratio when you drive it with the turbine.

The turntable bearings will probably support a turbine of 300mm diam and 600mm high on the table.

So there you have it....a DIY wind generator from a "music box"...LOL....probably generating a couple of Flea power, so don't disconnect from the utility supply co. just yet.

The point is, it will work, it's very portable and can be powered to work from a fan wind source for demo purposes, but only for fun to see the wheels go round, but it might recharge your MP3 player, mobile phone or Ipad, if'n you make a voltage/current regulator circuit for it....all very simple at that level, and you do learn how to handle mechanical as well as electrical design for pennies.
Ian.

[Burnit0017]

Hi, it sounds like a interesting project, I hope you post some photos when you have completed it. The configuration of belts and pulleys I am working on functions like a flexible rack and pinion and could be applied to other application. Thanks for all the comments and suggestions enjoy the day.