As you’ll see in the vid below, I’ve overcome the two biggest, and inter-related, problems:
the turbine occasionally tilting forward toward the bike and
the bike stand sometimes being pulled upwards and back toward the turbine.
Building a frame and using clamps to help keep the bike stand in place, and bolting and bracing the turbine into that frame, seem to have resolved those two project-killing issues. So finally I can produce electricity in relative comfort!
(Note: motion sensitive people should watch with caution – hand-turning a pedal to get over 12.5 volts is hard work, so my camera arm wobbles a lot!).
The last (hopefully!) major issue left is that of the chain skipping / jumping a cog or two when pedaling at 13.4 / 13.5 volts. Probably at least two contributing factors here.
the wobble in the face of the turbine means the cogs aren’t keeping to one plane while they rotate (although how to address that without stripping the whole thing down and shaving off some of the rotor’s steel face beats me!).
I’ve not quite managed to get the face of the turbine parallel with the chain going to the bike. Fixing that might mean altering the new frame and bracing arrangement <sigh>.
Of course in the video you might notice the chain appears very slack – and wonder why I don’t tighten it. The simple answer is that, with two links already taken out, tightening it any more will make it too rigid by far. Even moving it onto a bigger cog to take up some slack makes it far too tense. It wouldn’t last long given the forces at work here.
Of course the real answer is to start all over again and build a frame that allows for micro-adjustment of the distances and angles between bike and turbine… but affording the raw materials and time to do that would take a decent lotto win!
So I have to hope that I can resolve the chain problem another way.
A half-day of twiddling… making a new, thinner, front plate for the alternator… attaching the racers rear-wheel cogs again… balancing the turbine with bits of lead flashing… and it is paying off. Because most of the thumping and thudding is gone when I pedal.
I say ‘most’ because, when pedaling fast enough to produce more than 13.5v, there are still times when the chain skips over some cogs. The resulting thud and jolt is nerve-wracking to say the least. Never mind what it might be doing to the bike, chain, turbine or floor!
In case you are daft enough to take on this project yourself, what I think is happening is that the alternator is being pulled forward, toward the bike, with every down-ward pedal. As this is when I’m applying the most force, and that force has a beat / pulse in it, a pulsing momentum begins to build up in the turbine.
Then, not being a robot, one of my downward pedals is slightly weaker/stronger or slight out of rhythm and !!-BANG-!! the chain skips a few cogs on the alternator. At a guess, that problem is exacerbated by the fact that the wood in the pallet might be bending slightly allowing the turbine lift and tilt toward the bike with every downward pedal strokd.
But what it all amounts to is that the chain sporadically slips/skips a few cogs and there’s a massive chunk from behind me. Which ain’t good for turbine, bike or rider!
So the next step is to brace the alternator against the bike training stand. Once done the unit should finally be functional enough to allow me make electricity in comfort. Without fear of chains jumping or alternators getting thumped to bits!!
Finally persuaded a friend to visit and turn the pedals while I watched to see if I could spot what was causing the jumping around. From what I could see the cause is most likely to be balancing… or lack thereof.
The wobbles are tolerable while the turbine turns slowly. But once things begin to speed up it takes on a regular pulsing sound and movement – that might be exacerbated by the shape of the piece of metal onto which the cogs are welded.
Talking with Eirbyte about this, the solution might simply entail replacing the existing wooden disk with a larger one. Then putting lead weights on various parts of that bigger disk to balance the rotor as it turns.
I might also replace the existing piece of metal onto which the cogs have been welded. Because it itself is probably not helping. However I could balance the turbine without doing that… so it’s really a cosmetic desire.
But then again, this yoke is sitting in my house so it’d be nice for it to look good! 8)
That said I’ll only do it if grinding off the current back plate could be done without damaging the cogs.
But now have hope that I can get rid of the thumping and vibrating. It’s about the only thing stopping me clocking up the miles!